# TECHNICAL SUPPORT DOCUMENT:

ENERGY EFFICIENCY STANDARDS

FOR CONSUMER PRODUCTS:

NON­CLASS A EXTERNAL POWER SUPPLIES

Including:

Market Assessment Technology Assessment Engineering Analysis Energy Use and End­Use Load Characterization Life­Cycle Cost and Payback Period Analysis National Impact Analysis

August 2009

U.S. Department of Energy Assistant Secretary Energy Efficiency & Renewable Energy Office of Building Research and Standards Washington, DC 20585

IThis Document was prepared for the Department of Energy� by staff members of� D&R International, Ltd� and� Navigant Consulting, Inc�

IITABLE OF CONTENTS

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CHAPTER 1 MARKET ASSESSMENT................................................................................ 1­1

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1.1 Introduction................................................................................................................... 1­1

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1.2 Distribution Channels and Markups ............................................................................. 1­1

­ 1.2.1 Multiple­Voltage External Power Supplies ......................................................... 1­1

­ 1.2.2 High Output Power External Power Supplies...................................................... 1­2

­ 1.2.3 External Power Supplies for Medical Devices .................................................... 1­3

­ 1.2.4 External Power Supplies for Certain Battery Chargers ....................................... 1­4

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1.3 Interested Parties........................................................................................................... 1­6

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1.4 Existing Energy Efficiency Programs........................................................................... 1­7

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CHAPTER 2 TECHNOLOGY ASSESSMENT ..................................................................... 2­1

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2.1 Introduction................................................................................................................... 2­1

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2.2 Functionality of Non­Class A EPSs.............................................................................. 2­1

­ 2.2.1 Particular Functionality of Multiple­Voltage EPSs ............................................. 2­1

­ 2.2.2 Particular Functionality of High­Power EPSs ..................................................... 2­2

­ 2.2.3 Particular Functionality of Medical EPSs............................................................ 2­3

­ 2.2.3.1 Lifetime of Medical EPSs.................................................................................... 2­4

­ 2.2.3.2 Safety Concerns of Medical EPSs ....................................................................... 2­4

­ 2.2.3.3 Levels of Protection under UL 60601­1 .............................................................. 2­5

­ 2.2.3.4 Output Voltages of Medical EPSs ....................................................................... 2­5

­ 2.2.3.5 Leakage Currents in Medical EPSs...................................................................... 2­6

­ 2.2.3.6 Maintaining Safety Certification.......................................................................... 2­7

­ 2.2.4 Particular Functionality of EPSs for BCs ............................................................ 2­7

­ 2.2.5 Electromagnetic Interference Suppression .......................................................... 2­7

­

2.3 Circuit Design of EPSs ................................................................................................. 2­9

­ 2.3.1 General Design of an External Power Supply ..................................................... 2­9

­ 2.3.2 Design Choice: Single Versus Multiple Voltage EPSs...................................... 2­10

­ 2.3.3 Class A AC/AC External Power Supplies ......................................................... 2­12

­ 2.3.4 Class A Unregulated Line­Frequency AC/DC External Power Supplies.......... 2­12

­ 2.3.5 Class A Linear­Regulated Line­Frequency AC/DC External Power Supplies.. 2­13

2.3.6 Class A Switching­Regulated Line­Frequency AC/DC External Power Supplies2­15

2.3.7 Switched­Mode AC/DC External Power Supplies ............................................ 2­16

­ 2.3.8 Design of Output Cables.................................................................................... 2­18

­ 2.3.9 Particular Designs of Multiple­Voltage EPSs.................................................... 2­19

­ 2.3.9.1 Additional Regulators from a Single Tap .......................................................... 2­19

­ 2.3.9.2 Multiple Taps..................................................................................................... 2­20

­ 2.3.9.3 Multiple Windings ............................................................................................. 2­21

­ 2.3.9.4 Multiple Cores ................................................................................................... 2­22

­ 2.3.10 Particular Designs of High­Power EPSs............................................................ 2­23

­ 2.3.10.1 Line­Frequency Designs for High­Power EPSs .............................................. 2­24

­ 2.3.10.2 Switched­Mode Designs for High­Power EPSs .............................................. 2­24

­

III2.3.11 Particular Designs of Medical EPSs .................................................................. 2­28

­ 2.3.12 Particular Designs of EPSs for BCs................................................................... 2­29

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2.4 Technology Options for Improving Energy Efficiency.............................................. 2­29

­ 2.4.1 Transformers...................................................................................................... 2­29

­ 2.4.2 Diode Losses and Synchronous Rectification.................................................... 2­30

­ 2.4.3 Technology Options for Multiple­Voltage EPSs............................................... 2­31

­ 2.4.4 Technology Options for High­Power EPSs ....................................................... 2­31

­ 2.4.5 Technology Options for Medical EPSs.............................................................. 2­31

­ 2.4.6 Technology Options for EPSs for BCs .............................................................. 2­31

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CHAPTER 3 ENGINEERING ANALYSIS ........................................................................... 3­1

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3.1 Introduction................................................................................................................... 3­1

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3.2 DOE Methods for Determining ERMC ........................................................................ 3­1

­ 3.2.1 Summary of Methods........................................................................................... 3­2

­ 3.2.2 Available Data ..................................................................................................... 3­3

­ 3.2.2.1 SME Efficiency Measurements of 5 W EPSs...................................................... 3­3

­ 3.2.2.2 SME Teardowns................................................................................................... 3­3

­ 3.2.3 DOE Method for Determining ERMC from iSuppli Data................................... 3­4

­ 3.2.4 Assumptions......................................................................................................... 3­8

­ 3.2.4.1 Production Volume .............................................................................................. 3­8

­ 3.2.4.2 Data Included in the Cost­Efficiency Curves ...................................................... 3­8

­ 3.2.5 SME Cost­Scaling Methodology ......................................................................... 3­9

­ 3.2.5.1 Direct Substitution of iSuppli Component Costs................................................. 3­9

­ 3.2.5.2 Direct Substitution of Category­Average iSuppli Component Costs .................. 3­9

­ 3.2.5.3 Scaling of SME Costs Using SME­iSuppli Component Matches ..................... 3­11

­ 3.2.5.4 Substitute Category­Average iSuppli Component Costs................................... 3­14

­ 3.2.6 Summary............................................................................................................ 3­15

­

3.3 Scaling EPS Efficiency with Output Power................................................................ 3­15

­

3.4 Scaling EPS Efficiency with Output Voltage ............................................................. 3­18

­ 3.4.1 Summary and Introduction ................................................................................ 3­18

­ 3.4.2 Experimental Basis ............................................................................................ 3­19

­ 3.4.3 Loss Calculations............................................................................................... 3­20

­ 3.4.4 Conclusion and Examples.................................................................................. 3­22

­

3.5 Cost Scaling by Nameplate Output Power and Sales Volume ................................... 3­24

­ 3.5.1 Introduction........................................................................................................ 3­24

­ 3.5.2 Observed Relationships in Available Data ........................................................ 3­24

­ 3.5.3 Model Development........................................................................................... 3­26

­ 3.5.4 Model Deployment ............................................................................................ 3­30

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3.6 Representative Product Classes and Representative Units ......................................... 3­31

­ 3.6.1.1 Representative Product Classes and Units for Multiple­Voltage EPSs............. 3­31

­ 3.6.1.2 Representative Product Classes and Units for High­Power EPSs ..................... 3­33

­ 3.6.1.3 Representative Product Classes and Units for Medical EPSs............................ 3­35

­ 3.6.1.4 Representative Product Classes and Units for EPSs for BCs ............................ 3­37

­

IV3.7 Selection of Candidate Standard Levels ..................................................................... 3­40

­ 3.7.1.1 Candidate Standard Levels for Multiple­Voltage EPSs..................................... 3­42

­ 3.7.1.2 Candidate Standard Levels for High­Power EPSs............................................. 3­45

­ 3.7.1.3 Candidate Standard Levels for Medical Device EPSs....................................... 3­45

­ 3.7.1.4 Candidate Standard Levels for EPSs for BCs.................................................... 3­47

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CHAPTER 4 ENERGY USE AND END­USE LOAD CHARACTERIZATION ................. 4­1

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4.1 Introduction................................................................................................................... 4­1

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4.2 Walkthrough of Unit Energy Consumption Calculation .............................................. 4­1

­ 4.2.1 Usage Profile for Multiple­Voltage EPS (203W, Xbox 360).............................. 4­2

­ 4.2.2 EPS Power Consumption by Modes of Operation............................................... 4­2

­ 4.2.3 Active Mode Efficiency and No Load Mode Power Consumption..................... 4­3

­ 4.2.4 Calculating Unit Energy Consumption................................................................ 4­3

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4.3 Unit Energy Consumption Values for Non­Class A External Power Supplies ............ 4­8

­ 4.3.1 Multiple­Voltage EPS for Multifunction Devices ............................................... 4­8

­ 4.3.2 High­Power EPS for Amateur Radio Equipment ................................................ 4­9

­ 4.3.3 EPS for Medical Devices................................................................................... 4­12

­ 4.3.4 EPS for Battery Chargers for Floor Care Appliances........................................ 4­14

­ 4.3.5 EPS for Battery Chargers for Power Tools........................................................ 4­15

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4.4 EPS Power Consumption by Modes of Operation...................................................... 4­17

­ 4.4.1 EPS Energy Use................................................................................................. 4­20

­ 4.4.1.1 EPS Energy Consumption.................................................................................. 4­20

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CHAPTER 5 LIFE­CYCLE COST AND PAYBACK PERIOD ANALYSIS ....................... 5­1

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5.1 Life­Cycle Cost and Payback Period Analysis ............................................................. 5­1

­ 5.1.1 Introduction.......................................................................................................... 5­1

­ 5.1.2 Overview of LCC and PBP Inputs....................................................................... 5­2

­ 5.1.3 Life­Cycle Cost Inputs......................................................................................... 5­5

­ 5.1.3.1 Efficiency­Related Consumer Purchase Price Inputs .......................................... 5­6

­ 5.1.3.2 Operating Cost Inputs .......................................................................................... 5­7

­ 5.1.3.3 Other Inputs to the LCC Analysis...................................................................... 5­10

­ 5.1.4 Payback Period Inputs........................................................................................ 5­12

­ 5.1.4.1 Definition and Inputs ......................................................................................... 5­12

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CHAPTER 6 NATIONAL IMPACT ANALYSIS.................................................................. 6­1

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6.1 Introduction................................................................................................................... 6­1

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6.2 National Inventory ........................................................................................................ 6­2

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6.3 Layout of the NES­NPV Workbook............................................................................. 6­3

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6.4 NES­NPV Calculation Walkthrough ............................................................................ 6­7

­ 6.4.1 Calculation of Unit Energy Savings .................................................................... 6­7

­ 6.4.2 Calculation of National Energy Savings in kWh................................................. 6­9

­ 6.4.3 Calculation of National Energy Savings in 2008$............................................. 6­12

­ 6.4.4 Calculating Incremental Unit Cost Increases..................................................... 6­12

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V6.4.5 Calculation of National Costs in $ (non­discounted)......................................... 6­14

6.4.6 Calculation of National Costs in 2008$............................................................. 6­17

6.4.7 Calculation of Net Present Value in 2008$........................................................ 6­17

6.5 Net Present Value Results........................................................................................... 6­17

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APPENDIX A.

­ NON­CLASS A EXTERNAL POWER SUPPLY COST­EFFICIENCY

ESTIMATION SURVEY...................................................................................... I

LIST OF FIGURES

Figure 1.1 Distribution Channels for Multiple­Voltage External Power Supplies...................... 1­1 Figure 1.2 Distribution Channels for High Power External Power Supplies .............................. 1­2 Figure 1.3 Distribution Channels for External Power Supplies for Medical Devices ................. 1­4 Figure 1.4 Distribution Channels for External Power Supplies for Certain Battery Chargers.... 1­5 Figure 2.1 Example Circuit of an EMI Filter............................................................................... 2­8 Figure 2.2 Topologies for External Power Supplies.................................................................. 2­10 Figure 2.3 Power Distribution Configurations for Consumer Products With Subsystems Requiring Different Supply Voltages ..................................................................... 2­11

­ Figure 2.4 Circuit Diagram for an AC/AC External Power Supply .......................................... 2­12

­ Figure 2.5 Circuit Diagram of a Line­Frequency Raw Supply.................................................. 2­13

­ Figure 2.6 Block Diagram of a Linear Regulator ...................................................................... 2­14

­ Figure 2.7 Simplified Circuit Diagram of a Linear Regulator................................................... 2­14

­ Figure 2.8 Block Diagram of a Switching­Regulated Line­Frequency AC/DC EPS................ 2­16

­ Figure 2.9 Block Diagram of a Switched­Mode Power Supply ................................................ 2­16

­ Figure 2.10 Simplified Circuit Diagram of a Flyback Switching Regulator ............................. 2­17

­ Figure 2.11 The second winding is center­tapped, providing multiple voltages ....................... 2­21

­ Figure 2.12 Multiple­Voltage EPS Design with Multiple Independent Cores, Which Allow the

­ Operation of One of the Outputs to be Suspended When Not Needed .................. 2­23

­ Figure 2.13 Switched­Mode Topologies and Corresponding Power Levels ............................. 2­25

­ Figure 2.14 Two­Transistor Forward Converter Circuit............................................................ 2­26

­ Figure 2.15 Push­Pull Converter Circuit ................................................................................... 2­27

­ Figure 2.16 Half­Bridge Converter Circuit................................................................................ 2­27

­ Figure 2.17 Full­Bridge Converter Circuit ................................................................................ 2­28

­ Figure 3.1 Illustration of DOE Process Used to Compile High­Volume Cost Estimates for the

­ Non­Class A Eps Determination Analysis from Sme and Isuppli Teardowns......... 3­2 Figure 3.2 SME Efficiency Measurements of 5 W EPSs ............................................................ 3­3 Figure 3.3 Categorization of Components Used to Perform Substitution or Scaling.................. 3­9 Figure 3.4 Tests of Variation and Number of Cost Estimates Necessary for Device Scaling... 3­10 Figure 3.5 Schematic Illustration of the Distribution of Efficiency Versus Maximum Rated Output Power; the ENERGY STAR Level Is Shown as a Pink Line, while the Blue Background Indicates Where Most of the Units Lie .............................................. 3­16

­ Figure 3.6 Schematic Illustration of Scaling EPS Efficiency with Output Power .................... 3­17

­ Figure 3.7 ENERGY STAR Level and Calculated Best­in­Market and Worst­in­Market Curves3­17

­ Figure 3.8 Schematic of EPS Loss Model Used for Scaling Efficiency with Voltage.............. 3­19

­ Figure 3.9 Difference in Active Mode Efficiency vs. Nameplate Output Voltage................... 3­20

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VIFigure 3.10 Efficiencies of 5W, 5V EPS Test Units After Scaling to the 1.8 W, 6 V Representative Unit Level ...................................................................................... 3­23 Figure 3.11 Efficiencies of 5W, 5V EPS Test Units After Scaling to the 4.8 W, 24 V Representative Unit Level. ..................................................................................... 3­23 Figure 3.12 Manufacturer Selling Price Versus Volume For Specific 2W and 5W EPSs ........ 3­25 Figure 3.13 Manufacturer Selling Price Versus Output Power for Specific 2 W And 5 W EPSs at

Different Production Volumes................................................................................ 3­25 Figure 3.14 Example EPS materials Cost Modeled as a Sum of Fixed and Incremental Costs.3­26 Figure 3.15 Offset Efficiency­Related Materials Cost Versus Volume for Specific 2W and 5W

EPSs........................................................................................................................ 3­27

­ Figure 3.16 Extended Trendlines Based on Publicly Available EPS Data................................ 3­28

­ Figure 3.17 Extended trendlines with confidential dataset trendline added. ............................. 3­29

­ Figure 3.18 Product Count for Multiple­Voltage EPSs............................................................. 3­32

­ Figure 3.19 Product Count for High­Power EPSs ..................................................................... 3­34

­ Figure 3.20 Product Count for Medical EPSs............................................................................ 3­36

­ Figure 3.21 Estimate of Energy Consumption for Different EPSs for BCs .............................. 3­39

­ Figure 3.22 Comparison of Active Mode Efficiency and No­Load Power; Arrows Point in

­ Direction of Increased Efficiency........................................................................... 3­42 Figure 4.1 Relationship Between EPS Input Power and Output Power at Five Loading Points as Measured by the Test Procedure............................................................................. 4­19 Figure 5.1 Usage of External Power Supplies ............................................................................. 5­2 Figure 5.2 Flow Diagram of Inputs for the Determination of LCC and PBP.............................. 5­3 Figure 5.3 Normalized AEO2009 Residential Sector Reference Case Electricity Price Trend 5­10 Figure 6.1 Flow Chart Showing the Calculation of National Energy Savings and Net Present

Value......................................................................................................................... 6­3

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LIST OF TABLES

Table 1.1 Markups for Multiple­Voltage External Power Supplies ............................................ 1­2

­ Table 1.2 Markups for High Power External Power Supplies..................................................... 1­3

­ Table 1.3 Markups for External Power Supplies for Medical Devices ....................................... 1­4

­ Table 1.4 Markups for External Power Supplies for Battery Chargers ....................................... 1­5

­ Table 1.5 Trade Associations and Their Likely Areas of Interest ............................................... 1­6

­ Table 1.6 Trade Associations and Their Members ...................................................................... 1­7

­ Table 1.7 Selected Energy Efficiency Programs for External Power Supplies ........................... 1­8

­ Table 2.1 Maximum Leakage Current for Portable Equipment .................................................. 2­6

­ Table 2.2 Quality of Core Steel and Level of Magnetic Induction............................................ 2­30

­ Table 3.1 EPSs Torn Down by SMEs to Develop Low­Volume ERMCs................................... 3­4

­ Table 3.2 Information for Five Components from EPS #106...................................................... 3­5

­ Table 3.3 Information for All Components from EPS #106........................................................ 3­6

­ Table 3.4 EPS #106 Production Related Device Information ..................................................... 3­7

­ Table 3.5 EPS # 106 Summary of Component Costs by Efficiency Relevance.......................... 3­7

­ Table 3.6 EPS and BC Units that iSuppli Tore Down and DOE Used in Data Scaling.............. 3­8

­ Table 3.7 Example Matches Between SME and iSuppli Component Cost Estimates Used to

­ Develop Category­Specific Scaling Ratios ............................................................ 3­12

­ Table 3.8 Losses for Scaling Model for Efficiency with Output Voltage ................................. 3­20

­

VIITable 3.9 Value of Calculated Model Parameters ..................................................................... 3­30

­ Table 3.10 Representative Product Classes for Multiple­Voltage EPSs ................................... 3­31

­ Table 3.11 Characteristics of the Multiple­Voltage EPS Representative Units ........................ 3­33

­ Table 3.12 Representative Product Classes for High­Power EPSs............................................ 3­33

­ Table 3.13 Characteristics of the High­Power EPS Representative Unit .................................. 3­35

­ Table 3.14 Representative Product Classes for Medical EPSs.................................................. 3­35

­ Table 3.15 Characteristics of the Medical EPS Representative Unit......................................... 3­37

­ Table 3.16 Representative Product Classes for EPSs for BCs................................................... 3­37

­ Table 3.17 Representative Unit Characteristics for Battery Chargers....................................... 3­38

­ Table 3.18 Assumptions for Calculating Annual Energy Consumption.................................... 3­38

­ Table 3.19 Characteristics of the EPS for BCs Representative Units........................................ 3­40

­ Table 3.20 Candidate Standard Levels for a 40­Watt Multiple­Voltage EPS for a Multi­Function

­ Device ..................................................................................................................... 3­43 Table 3.21 Candidate Standard Levels for a 203­Watt Multiple­Voltage EPS for a Video Game

Console ................................................................................................................... 3­43

­ Table 3.22 Candidate Standard Levels for a 345­Watt High­Power EPS for a Ham Radio...... 3­45

­ Table 3.23 Candidate Standard Levels for an 18­Watt Medical Device EPS for a Nebulizer .. 3­46

­ Table 3.24 Candidate Standard Levels for a 1.8­Watt EPS for BC for a Vacuum.................... 3­47

­ Table 3.25 Candidate Standard Levels for a 4.8­Watt EPS for a Do­It­Yourself Power Tool.. 3­47

­ Table 4.1 Weighted­Average Usage and Output Power of EPS for Xbox 360 ........................... 4­2

­ Table 4.2 Load by Application State for EPS for Xbox 360 ....................................................... 4­3

­ Table 4.3 Candidate Standard Levels for an EPS for Xbox 360 ................................................. 4­3

­ Table 4.4 Equations Used to Calculate Energy Consumption in Each Application State........... 4­4

­ Table 4.5 UEC for Active – Playing Video Game (EPS Output Power = 102.62 W)................. 4­5

­ Table 4.6 UEC for Active – Idle Video Game (EPS Output Power = 101.50 W)....................... 4­5

­ Table 4.7 UEC for Active – Playing DVD (EPS Output Power = 95.02 W) .............................. 4­5

­ Table 4.8 UEC for Active – Idle DVD (EPS Output Power = 95.02 W) .................................... 4­6

­ Table 4.9 UEC for Active – Idle No­Disc (EPS Output Power = 86.38 W) ............................... 4­6

­ Table 4.10 UEC for Active – Off (EPS Output Power = 2.35 W)............................................... 4­6

­ Table 4.11 UEC for Active ­ Continued ...................................................................................... 4­7

­ Table 4.12 UEC for No Load Mode ............................................................................................ 4­7

­ Table 4.13 UEC by Application State at Each Candidate Standard Level .................................. 4­8

­ Table 4.14 Candidate Standard Levels for 40 W Multiple­Voltage EPS for Multifunction

­ Devices ..................................................................................................................... 4­8 Table 4.15 Usage and Output Power of EPS for 40 W Multiple­Voltage EPS for Multifunction

Devices ..................................................................................................................... 4­9 Table 4.16 Unit Energy Consumption for 40 W Multiple­Voltage EPS for Multifunction Devices4­9 Table 4.17 Candidate Standard Levels for 345 W High­Power EPS for Amateur Radio Equipment................................................................................................................. 4­9

­ Table 4.18 Light Usage of 345 W High­Power EPS for Amateur Radio Equipment ............... 4­10

­ Table 4.19 Medium Usage of 345 W High­Power EPS for Amateur Radio Equipment........... 4­10

­ Table 4.20 Heavy Usage of 345 W High­Power EPS for Amateur Radio Equipment.............. 4­11

­ Table 4.21 Weighted­Average Usage and Output Power of 345 W High­Power EPS for Amateur

­ Radio Equipment .................................................................................................... 4­11 Table 4.22 Unit Energy Consumption for 345 W High­Power EPS for Amateur Radio Equipment4­12

Table 4.23 Candidate Standard Levels for 18 W EPS for Medical Devices ............................. 4­12

VIIITable 4.24 Medium Usage of 18 W EPS for Medical Devices ................................................. 4­12

­ Table 4.25 Heavy Usage of 18 W EPS for Medical Devices .................................................... 4­13

­ Table 4.26 Weighted­Average Usage and Output Power of 18 W EPS for Medical Devices .. 4­13

­ Table 4.27 Unit Energy Consumption for 18 W EPS for Medical Devices .............................. 4­13

­ Table 4.28 Candidate Standard Levels for 1.8 W EPS for Floor Care Appliances ................... 4­14

­ Table 4.29 Usage and Output Power of 1.8 W EPS for Floor Care Appliances ....................... 4­14

­ Table 4.30 Unit Energy Consumption for 1.8 W EPS for Floor Care Appliances .................... 4­14

­ Table 4.31 Candidate Standard Levels for 4.8 W EPS for Power Tools................................... 4­15

­ Table 4.32 Light Usage of 4.8 W EPS for Power Tools............................................................ 4­15

­ Table 4.33 Heavy Usage of 4.8W EPS for Power Tools........................................................... 4­16

­ Table 4.34 Weighted­Average Usage and Output Power of 4.8 W EPS for Power Tools........ 4­16

­ Table 4.35 Unit Energy Consumption for 4.8 W EPS for Power Tools.................................... 4­17

­ Table 5.1 Draft Inputs to the Life­Cycle Cost and Payback Period Analysis.............................. 5­4

­ Table 5.2 Annual Average Consumer Price Indices.................................................................... 5­9

­ Table 5.3 AEO2009 Electricity Prices......................................................................................... 5­9

­ Table 5.4 Shares and Interest or Return Rates Used for Household Debt and Equity Types.... 5­11

­ Table 6.1 Example National Inventory Table.............................................................................. 6­2

­ Table 6.2 Unit Energy Consumption in the Base Case (2013).................................................... 6­8

­ Table 6.3 Unit Energy Consumption in the Standards Case (2013) ............................................ 6­8

­ Table 6.4 Unit Energy Savings by Shipment Year .................................................................... 6­10

­ Table 6.5 Unit Inventory In 2018 .............................................................................................. 6­10

­ Table 6.6 Combination of Tables 6.4 and 6.5............................................................................ 6­11

­ Table 6.7 Unit Cost in the Base Case ........................................................................................ 6­13

­ Table 6.8 Unit Cost in the Standards Case ................................................................................ 6­13

­ Table 6.9 Unit Incremental Cost by Shipment Year.................................................................. 6­15

­ Table 6.10 Unit Shipments by Shipment Year .......................................................................... 6­15

­ Table 6.11 Combination of Tables 6.9 and 6.10........................................................................ 6­16

­ Table 6.12 Net Present Value of Standards at 3 Percent Discount Rate.................................... 6­18

­ Table 6.13 Net Present Value of Standards at 7 Percent Discount Rate.................................... 6­19

­

IXCHAPTER 1 MARKET ASSESSMENT

1.1 Introduction

This chapter of the Technical Support Document (TSD) contains information that supports and expands upon the market assessment section of the notice of proposed determination. The notice was issued by the U.S. Department of Energy as part of its determination concerning the potential for energy conservation standards for non­Class A external power supplies. a

1.2 Distribution Channels and Markups

1.2.1 Multiple­Voltage External Power Supplies

Almost all EPSs in this group are contracted by two OEMs (Microsoft and HP) for use with two products (Xbox 360 and HP’s multifunction devices) and are not sold through EPS distributors or directly to retailers. Once packaged with the Xbox 360 or a multifunction device, products are sold exclusively through retailers. Figure 1.1 depicts the distribution system just described. Based on its understanding of distribution channels, DOE calculated a markup of between 3.15 and 3.18 for multiple­voltage EPSs from ERMC to post­tax consumer price. This markup is detailed in Table 1.1.

**Component Manufacturers** 

**EPS Manufacturers** 

**Consumers OEMs** 

**Consumer Product**  **Retailers**

Figure 1.1 Distribution Channels for Multiple­Voltage External Power Supplies

a The notice and the accompanying TSD can be downloaded from the Office of Energy Efficiency and Renewable Energy’s website: http://www1.eere.energy.gov/buildings/appliance_standards/residential/battery_external.html

1­1Table 1.1 Markups for Multiple­Voltage External Power Supplies

­

Step Markup

EPSs for MFDs EPSs for Xbox 360

EPS Manufacturer Markup 64% 64%

OEM Markup 32% 31%

Device Retailer/Distributor Markup 37% 37%

Sales Tax 6.8% 6.8%

Consumer Price : ERMC 3.18 : 1 3.15 : 1

Source: EPS Manufacturer markups based on interviews with EPS Manufactures. OEM and retailer markups are based on gross margin data for public companies retrieved from http://finance.yahoo.com. The population­weighted, national average sales tax figure is from the Sales Tax Clearinghouse, Inc. (http://www.thestc.com/FAQ.stm)

1.2.2 High Output Power External Power Supplies

Because of the flexible environment in which EPSs intended for use with amateur radio equipment are used, these EPSs are not supplied with specific applications or equipment. Rather, they are sold as stand­alone products, so their design and manufacture is initiated by the EPS manufacturer itself. The EPS manufacturer then distributes the product through specialty retailers for amateur radio equipment. Because of the small number of retailers and low volume of shipments involved, EPS distributors are generally not used. Figure 1.2 depicts the distribution system just described. Based on its understanding of distribution channels, DOE calculated the markup for high power EPSs at 1.80 from ERMC to post­tax consumer price. This markup is

detailed in Table 1.2.

**Component Manufacturers** 

**EPS Manufacturers** 

**Consumer Product Retailers** 

**Consumers**

Figure 1.2 Distribution Channels for High Power External Power Supplies

­

1­2Table 1.2 Markups for High Power External Power Supplies

­

Step Markup

EPS Manufacturer Markup 24%

Retailer 36%

Sales Tax 6.8%

Consumer Price : ERMC 1.80 : 1

Source: EPS Manufacturer markups based on interviews with EPS Manufactures. OEM and retailer markup based on difference between estimated distributor price and retailer price. The population­weighted, national average sales tax figure is from the Sales Tax Clearinghouse, Inc. (http://www.thestc.com/FAQ.stm)

1.2.3 External Power Supplies for Medical Devices

Medical devices, unlike most other applications powered by EPSs, must meet certain design requirements before distribution. These requirements are maintained by the FDA’s Center for Devices and Radiological Health b and covered under 21 CFR 800­1299. c Despite these additional design requirements, the distribution for EPSs for medical devices is roughly similar to that of other EPSs. This is because while the requirements of 21 CFR 800­1299 affect the design of the EPS, the medical devices to which the EPS provides power generally do not require anything beyond the requirements of a generic power source. Therefore, once an EPS is built to the requirements of 21 CFR 800­1299, it can be used with multiple medical devices, much as a generic Class A EPS can be used with multiple applications. For those medical devices requiring more specialized input power, custom EPSs may be used instead.

Once the EPS is received by the OEM, it is packaged with the device itself then sold via medical device distributors or specialty retailers. OEM’s rarely sell medical devices directly to consumers. Figure 1.3 outlines the distribution system for EPSs used to power medical devices as just described. Based on its understanding of distribution channels, DOE calculated a markup for medical device EPSs between 3.46 and 4.02 times the ERMC and a shipment­weighted average markup of 3.60. This markup is detailed in Table 1.3.

b http://www.fda.gov/CDRH /

c http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPartFrom=800&CFRPartTo=1299

1­3**Component Manufacturers** 

**EPS Manufacturers** 

**EPS Distributors** 

**OEMs**

**Medical Product**  **Medical Product** 

**Distributors Retailers** 

**Consumers**

Figure 1.3 Distribution Channels for External Power Supplies for Medical Devices

Table 1.3 Markups for External Power Supplies for Medical Devices

Step Markup

EPS Manufacturer Markup 64%

[EPS Distributor Markup] 16%

OEM Markup 50%

Retailer/Distributor Markup 32%

Sales Tax 6.8%

Consumer Price : ERMC (without distributor)
Consumer Price : ERMC (with distributor) 3.46: 1

4.02 : 1

Shipment­Weighted Average Markup 3.60 : 1

Source: EPS Manufacturer markups based on interviews with EPS Manufactures. OEM and retailer markups are based on gross margin data for public companies retrieved from http://finance.yahoo.com. The population­weighted, national average sales tax figure is from the Sales Tax Clearinghouse, Inc. (http://www.thestc.com/FAQ.stm). Assumes 25 percent of EPS shipments pass through an EPS distributor on their way to the OEM.

1.2.4 External Power Supplies for Certain Battery Chargers

Similar to the design of multiple­voltage EPSs, the design of EPSs to be used with battery chargers is highly customized. Because of this, DOE believes that EPSs in this group are nearly always contracted by OEMS for use with a specific product. It is unlikely that any EPS to be used with a battery charger would ever be sold separately from the battery charging system, except possibly as a replacement part. In addition, DOE could find no instance of an OEM

1­4selling directly to consumers. Therefore, DOE assumes that all EPSs in this category are contracted by an OEM and sold through a retailer. Figure 1.4 outlines the distribution system for EPSs for battery chargers as just described. Based on its understanding of distribution channels, DOE calculated markups for EPSs for battery chargers of 3.69 times the ERMC for floor care appliances and 4.14 times the ERMC for DIY power tools. See Table 1.4 for more detail.

**Component Manufacturers** 

**EPS Manufacturers** 

**Consumers OEMs** 

**Consumer Product**  **Retailers**

Figure 1.4 Distribution Channels for External Power Supplies for Certain Battery Chargers

Table 1.4 Markups for External Power Supplies for Battery Chargers

Step Markup

Floor Care Appliances DIY Power

Tools

EPS Manufacturer Markup 60% 60%

OEM Markup 49% 61%

Retailer Markup 45% 51%

Sales Tax 6.8% 6.8%

Consumer Price: ERMC 3.69 : 1 4.14 : 1

Source: EPS Manufacturer markups based on interviews with EPS Manufactures. OEM and retailer markups are based on gross margin data for public companies retrieved from http://finance.yahoo.com. The population­weighted, national average sales tax figure is from the Sales Tax Clearinghouse, Inc. (http://www.thestc.com/FAQ.stm)

1­51.3 Interested Parties

Table 1.5 lists a number trade associations that may have an interest in this determination and indicates which types of NCA EPS DOE believes each association has an interest in. Table

1.6 gives examples of each association’s member companies.

Table 1.5 Trade Associations and Their Likely Areas of Interest

Trade Association MultipleVoltage

EPSs High Power

EPSs Medical

EPSs EPSs for

Certain Battery Chargers

Advanced Medical Technology Assoc. X

American Radio Relay League X

Assoc. for the Advancement

of Medical Instrumentation X

Assoc. of Home Appliance

Manufacturers X

Consumer Electronics

Assoc. X X

European Power Supply

Manufacturers Assoc. X X X X

Information Technology Industry Council X

Medical Device

Manufacturers Assoc. X

Power Sources

Manufacturers Assoc. X X X X

Power Tool Institute X

Source: Trade association websites and lists of past participants in DOE’s battery charger and external power supply rulemakings.

1­6Table 1.6 Trade Associations and Their Members

­

Trade Association Examples of Members

Advanced Medical Technology Assoc. Baxter International, Covidien, Philips Healthcare

American Radio Relay League (The ARRL is the largest national membership association for Amateur Radio operators in the U.S.)

Assoc. for the Advancement

of Medical Instrumentation (Membership list is not publicly available.)

Assoc. of Home Appliance

Manufacturers BISSEL Homecare, Black & Decker Corp., Dyson Limited, KitchenAid (Whirlpool), Panasonic, Philips Electronics, Remington, Wahl Clipper

Consumer Electronics

Assoc. Apple, Bose, Canon USA, Daewoo, Energizer, Epson, Dell, Garmin, HP, JVC, Kodak, LG, Microsoft, Mitsubishi, Nokia, Panasonic, Philips, Radio Shack, Ricoh, Samsung, Sanyo, Sony, Toshiba, Tyco

European Power Supply

Manufacturers Assoc. Artesyn Technologies, Astec Europe, Cherokee, Delta Electronics, Efore, FRIWO Power Solutions, Lambda Europe, MagnaTek, Roal Electronics

Information Technology Industry Council Apple, Canon, Cisco, Dell, Kodak, HP, Lenovo, Lexmark, Microsoft, Panasonic, Sony, Texas Instruments

Medical Device

Manufacturers Assoc. (Membership list is not publicly available.)

Power Sources

Manufacturers Assoc. Artesyn, Astec, Ault, Cherokee, China Power Supply Society, Emerson Energy Systems, Leader Electronics, Power Integrations

Power Tool Institute Black and Decker, Bosch, Dewalt, Delta, Dremel, Makita, Ryobi

Source: AHAM, CEA, EPSMA, ITIC, PSMA, and PTI websites.

1.4 Existing Energy Efficiency Programs

DOE has identified both voluntary and regulatory energy efficiency programs that may affect the efficiency of NCA EPSs sold in the United States. The five most important programs, summarized in Table 1.7, include three domestic programs and two foreign programs. The three domestic programs are the federal mandatory standard for Class A EPSs, the U.S. EPA’s voluntary ENERGY STAR standard for EPSs, and California’s mandatory standard for so­called “State Regulated EPSs.” Among the many foreign programs, there are two particularly noteworthy programs in the European Union. All five programs are discussed below.

1­7Table 1.7 Selected Energy Efficiency Programs for External Power Supplies

­

Country/Region Authority Program/Institution

United States Mandatory Federal standard for Class A EPSs

United States Voluntary ENERGY STAR for EPSs

California Mandatory State standard for “State Regulated EPSs”

European Union Mandatory Eco­design of Energy­using Products (EuP) Initiative, Directive 2005/32/EC

European Union Voluntary Code of Conduct on Efficiency of External Power Supplies, EU Standby Initiative

A federal standard for Class A EPSs took effect on July 1, 2008. This standard, while intended to regulate only Class A EPSs, may very well have a spillover effect on the efficiency of EPSs outside of Class A. The standard for Class A EPSs has increased the demand for, and lowered the cost of, some of the more efficient components and has stimulated the adoption of improved designs. Because many of the same techniques and components are used to manufacture NCA EPSs that are used to manufacture Class A EPSs, DOE assumes that some of these components and designs will carry over into the design and manufacture of NCA EPSs.

New, more stringent ENERGY STAR criteria for EPSs took effect on November 1, 2008. As of December 2, 2008, there were already over 1,000 qualified models. d Like the existing federal standard, these voluntary criteria apply only to Class A EPSs. Nevertheless, DOE expects the ENERGY STAR program’s efforts to improve the energy efficiency of Class A EPSs to have some spillover effect on the efficiency of NCA EPSs.

On December 3, 2008 the California Energy Commission adopted standards, retroactive to July 1, 2008, for certain “State Regulated EPSs.” e State Regulated EPSs appear to include EPSs for medical devices and for most battery chargers, but explicitly exclude multiple­voltage EPSs and high power EPSs. The standard levels are identical to those for Class A EPSs. California is home to about 12 percent of the U.S. population f and probably represents about the same proportion of the U.S. market for EPSs for medical devices and certain BCs. Thus, if manufacturers are complying with California law, at least 12 percent of the NCA EPSs of these two types sold in the U.S. already comply with the standard for Class A EPSs. In fact, it is likely that an even larger proportion comply, given that manufacturers tend to sell the same products throughout the country.

d External Power Supplies Ac­Dc QP List. U.S. Environmental Protection Agency. December 2, 2008. (Retrieved

­ 12/17/08 from http://www.energystar.gov/index.cfm?c=manuf_res.pt_adapters)

­

e Proposed Amendments to Appliance Efficiency Regulations (Express Terms), California Code of Regulations,

­ Title 20, Sections 1601 through 1608. California Energy Commission. November 2008. (Retrieved 12/17/08 from

­ http://www.energy.ca.gov/2008publications/CEC­400­2008­021/CEC­400­2008­021­15DAY.PDF )

­ f Table 1: Annual Estimates of the Resident Population for the United States, Regions, States, and Puerto Rico: April

­ 1, 2000 to July 1, 2008 (NST­EST2008­01). Population Division, U.S. Census Bureau. Released December 22,

­ 2008. (Retrieved 12/22/08 from http://www.census.gov/popest/estimates.php )

­

1­8The European Commission, as part of its Eco­design of Energy­using Products (EuP)Initiative, has established mandatory minimum energy performance standards for all singlevoltage EPSs with nameplate output power up to 250 watts sold anywhere in the European

Union. The current standard levels are set to take effect in 2010 and are identical to those for Class A EPSs in the U.S. Exclusions include medical devices, battery chargers, uninterruptible power supplies, voltage converters, and EPSs for low voltage tungsten halogen lamps. The Commission has also set more stringent standards, which take effect in 2011. g

The European Commission Joint Research Centre developed and administers the E.U. Code of Conduct on Efficiency of External Power Supplies, a voluntary agreement. Signatories to the Code of Conduct, which include major manufacturers of external power supplies, agree to meet active­mode efficiency and no­load power consumption targets for at least 90 percent of their product lines. The current targets, which took effect on January 1, 2009, are more stringent than those for Class A EPSs in the U.S. All single­voltage EPSs and battery charger wall adapters with nameplate output power between 0.3 watts and 150 watts are covered under this

standard.

g Commission Regulation (EC) No. 278/2009, Official Journal of the European Union . L 93/3 of April 6, 2009.

1­9CHAPTER 2 TECHNOLOGY ASSESSMENT

2.1 Introduction

The following chapter of Technical Support Document (TSD) contains information that supports and expands on the Technology Assessment section of the Notice of Proposed Rulemaking (NOPR), which can be referenced for further information regarding the following topics:

• Definitions

• The Role of Power Converters

• Efficiency Metrics

• Product Classes

• Overlapping Terminology

Specifically, this technology assessment TSD chapter examines the functionality and design of non­Class A external power supplies (EPSs) with a focus on the components and subsystems that have the biggest impact on energy efficiency. DOE believes that there are four types of non­Class A EPSs: (1) multiple­voltage EPSs, (2) high power EPSs, (3) medical EPSs, and (4) EPSs for battery chargers (BCs). The chapter begins with a description of the functionality provided by external power supplies in the context of the system that they power. Meeting the functionality requirements of EPSs is the objective of the circuit design. To that end, the chapter continues by presenting the circuit designs that manufacturers typically use to achieve these specifications. Because the design of non­Class A EPSs has much in common with Class A EPSs, the assessment first discusses designs of Class A EPSs (such as unregulated, linear regulated and switched­mode regulated EPSs). DOE then presents the unique traits of each of the four types of non­Class A EPSs. Last, the chapter presents technology options for improving the efficiency of non­Class A

EPSs.

2.2 Functionality of Non­Class A EPSs

2.2.1 Particular Functionality of Multiple­Voltage EPSs

This class includes both devices that provide power at more than one distinct voltage to a consumer product as well as devices that have one power level, but one or more signal connections to the consumer product. All the multiple­voltage external power supplies that DOE has analyzed to date provide a regulated DC voltage at each power “output bus,” a although a multiple­voltage AC/AC power supply is also a technological possibility. Similarly, although it is technically possible for multiple­voltage EPSs to have any number of outputs, DOE is only aware of dual­output EPSs in use with commercial products.

a An “output bus” is a pair of conductors used to transfer power from the EPS to a consumer product, as opposed to a pair of conductors used to transmit a data signal. For example, an EPS may have two pairs of conductors—a power output bus and a pair used to transmit a “standby” signal, causing the EPS to enter a low­power state when the product is not using the EPS.

2­1Although EPSs in this class provide multiple voltages simultaneously, they are designed to power a single consumer product. The wires that comprise the multiple output busses are typically contained within a single cable with a single output connector with multiple terminals or pins. The output busses provide power to the various subsystems within the consumer product, each of which has a particular voltage requirement that depends on its own function and

components.

Multiple­function devices use multiple­voltage EPSs to provide a dedicated voltage to the ink cartridges, called “pens,” and use a second voltage for all other functions (logic, print­engine motors, etc...) Multi­function devices are combination­printers that allow the user to scan, print, copy, and/or fax documents in addition to standard printing functions.

Video­game consoles rely on multiple­voltage EPSs for a different reason. Because of their compact size, video­game consoles may use an EPS to minimize space constraints and heat exposure to the main console. In addition manufacturers use an external power supply to limit the number of products requiring UL recognition. The UL process adds to the cost of the unit and can take six to nine months to complete. This allows manufacturers to save money and time. In the topology of the video­game EPS there is an additional 5 V output for operation of the game console in a “standby” b mode

. This output, which is provided by a separate transformer core within the EPS, provides all the power required by the product during standby, allowing the rest

of the EPS to shut down.

2.2.2 Particular Functionality of High­Power EPSs

High­power EPSs are a fixture in any electronics laboratory and are sometimes used for commercial applications such as audio recording and processing and powering illuminated signs. However, as mentioned in the market assessment section of the NOPR, the primary consumer application of these EPSs is powering communications equipment, in particular amateur or “ham” radios. These radios are capable of transmitting information across the country and, given sufficient power, even around the world. Ham radios are mostly a hobby item for those wishing to communicate with others; however, these radios can be of particular importance in cases of emergency, for example, when natural disasters have disabled other means of communication.

Although they range in power from 100 W to over 1 kW, c EPSs for ham radio applications provide a DC output at 13.8 V, allowing ham radio users to operate mobile equipment intended for use in a vehicle d in a stationary location. Unlike stationary ham

b This standby mode and the device mode that it enables should not be confused with the standby mode of the EPS, which is defined as the condition where the power supply is connected to mains, is disconnected from the load, and has any manual on­off switches in the on position.

c EPSs for ham radio applications with output power less than or equal to 250 W are common, but are outside the scope of this determination analysis and are covered under DOE’s energy conservation standards for Class A EPSs.

d Although lead­acid automobile batteries have a nominal voltage of 12 V, the voltage provided by the alternator must be higher to maintain the charge of the battery. Thus, when the car is running, the voltage across the battery ranges between 13 V and 15 V depending on alternator charge current, battery chemistry, and temperature, with

13.8 V as a nominal value. D. Linden and T. Reddy. Handbook of Batteries. Third Ed. New York: McGraw­Hill, 1995. pp. 23.68–23.75.

2­2equipment, mobile equipment does not include an internal power supply because it was designed around the availability of DC power from a vehicle’s electrical system. Therefore, when this equipment is taken out of the vehicle, an EPS is required.

Even though this ham radio equipment is mobile, it is not exactly portable: users are not expected to travel extensively with the transmitters and power supplies, unlike in the case of laptop computers. As a result, EPSs for radio applications tend to be larger and heavier than those for other consumer applications, when compared at output powers below 250 W.

Because high­power EPSs are primarily used in communication applications, electromagnetic interference, or “noise,” impacts their functionality. The Federal Communications Commission (FCC) has regulations for electromagnetic compatibility (EMC), which limit interference from consumer products, such as high­power EPSs. Although manufacturers of high­power EPSs ensure that their products comply with these regulations, ham radio receivers have excellent sensitivity, enabling reception of very weak electromagnetic (EM) signals. Having a local noise source, such as a switching supply, can interfere with reception. As a result, the electronic noise generated by an EPS, however small, can couple to the radio receiver affecting its utility, and at high enough levels become an audible buzzing sound or a constant hum. The local emissions will also act to reduce the gain of the receiver if they are stronger than the desired signal. The receiver gain is determined by the strongest signal. This happens because of adaptive receiver behavior (automatic gain control). Noise is therefore an extremely important consideration that influences the EPS design. In EPSs significantly over 100 W, it is possible to dramatically improve EMI suppression for a minimal increase in cost or efficiency. Doing so calls for a higher level of inductance in the common mode chokes (see section 2.2.5 for more detail). Most designers only design their ham radio EPSs to just meet FCC requirements, but technology exists that can cost­effectively eliminate the issue of interference in ham radios. As a result, line­frequency EPSs, which generate much less EM noise than switch­mode EPSs, are still used to a greater degree in amateur radio field setups.

2.2.3 Particular Functionality of Medical EPSs

Interviews with EPS manufacturers indicate that external power supplies used with medical devices, unlike Class A EPSs used with commercial information technology and entertainment (ITE) equipment, have additional requirements for use in a medical setting. One difference is that medical devices have longer lifetimes than other electrical products. Another requirement comes from the Food and Drug Administration, which regulates medical equipment under the Federal Food, Drug, and Cosmetic Act. The act stipulates that all medical devices

must be safe and effective e . Although the FDA does not specify a single safety certification, safety is typically conferred by Underwriters Laboratory (UL), the major product safety certification organization in the United States. Overall, the additional requirements of medical EPSs affect their price, but have limited impact on achievable efficiency.

e SEC. 513. [21 USC 360c ] – taken Sept. 4 th 2008 from http://www.fda.gov/opacom/laws/fdcact/fdcact5a2.htm

2­32.2.3.1 Lifetime of Medical EPSs

Electronic medical devices are typically used for a period of as few as 5 years to 10 years or more, whereas consumers tend to use commercial ITE equipment for 1 to 4 years. Further, medical devices are often in use continuously as opposed to commercial products that operate at a maximum of 8 hours per day. During operation, medical EPSs typically operate at 75% to 80% of their maximum rated output. Another consideration is the hold­up time of the EPS – how long it can provide output power during an interruption of its input power. Medical EPSs can have hold up times of around 50 ms as compared to EPSs for ITE products that have hold up times of just a few milliseconds. Most importantly, the consequences of a medical EPS failing are much more dire than for EPS for ITE products. When commercial equipment fails the consumer may be frustrated and upset; however, if a medical device were to fail it could result in injury or possibly death. Therefore, medical EPSs are more stringently designed not to fail over longer lifetimes and under continuous operating conditions than general EPSs.

2.2.3.2 Safety Concerns of Medical EPSs

Another design consideration is safety. In the United States, medical EPSs must be proven safe, typically through certification under the Underwriters Laboratory 60601­1 standard, which is based on the internationally­harmonized standard IEC 60601­1, developed by the International Electrotechnical Commission (IEC). The primary philosophy of the standards is to ensure equipment safety in normal operating conditions and during a single fault condition. An example of a normal operating condition is that the consumer accidentally plugs in the EPS with reverse polarity of the mains supply. An instance of a single fault condition is failure of electronic components, one at a time. These standards are more stringent than those for general commercial equipment because medical patients may not be able to respond to electrical shocks or pain, there may be an electrical connection to the patient, and some medical devices provide life support, so their failure could result in the death of the patient.

Similar to other electrical products, medical products have the option of using either an internal power supply or an external power supply. External power supplies offer the benefits of reducing the size of the medical device and reducing the safety requirements of the medical device, by placing it on the EPS. The size is reduced by placing the power supply circuitry outside the housing for the medical device. As compared to general EPSs, UL 60601­1 requires medical EPSs to have wider distances between the primary and secondary sides of the circuit for added safety, resulting in physically larger circuits. Furthermore, products that connect directly to mains must use tougher, more expensive materials to reduce the risk of failure. An EPS will isolate the medical devices from mains and, thus, reduce the device’s safety requirements. This benefit can be particularly useful for medical devices that deal with fluids. Those medical devices may use an EPS with a short, 2 ft. AC input cord and a long 10 – 15 ft. DC output cord, whereas an EPS for ITE applications could have input and output cords that are both 3 ft. long. These cord lengths increase the safety of the medical device by increasing the separation of the device and its fluids from mains power.

2­42.2.3.3 Levels of Protection under UL 60601­1

UL 60601­1 applies both to medical devices as well as their external power supplies. For medical EPSs, the primary concern is protection from electrical hazards in the circuit design. The standard stipulates that there must be two levels of protection against an unintentional leakage current passing through the patient. This current could pass between a live part connected to mains and an applied part that might contact the patient. The patient must be protected if they are accidentally grounded or accidentally connected to mains. The levels of protection can be (1) insulation to separate the patient from mains, (2) protective impedance to limit the current that can flow to a patient, or (3) protective earth that provides current a direct path to ground, rather than through the patient.

For the insulation barriers, UL 60601­1 specifies spacing distances and dielectric withstand voltages, based on the input voltage of the EPS. The distances specify how close the primary and secondary sides of the circuit can be. For example, with a 125V input voltage, a circuit is considered to have “basic insulation” if the primary and secondary are separated by 3 mm of creepage distance and 1.5 mm of air clearance. In addition, the dielectric separating the two sides is required to withstand a 1 kV drop across it. EPSs are often designed for universal input power, in which case the insulation barriers meet the more stringent requirements associated with 250 V, the European AC input voltage.

The EPS could also use protective impedance as a level of protection. The impedance would act to limit the maximum current to the patient to 10 �A or 100 �A, depending on the specification requirements.

Depending on the design, medical EPSs can also use a protective earth and are classified as either Class I or Class II. Class I EPSs have a protective earth connection, such as a metal enclosure, that is that tied to the ground pin of a three­pronged power plug. Class II EPSs do not have a protective earth, and instead use insulation as a layer of protection. In the United States, the protective earth must pass 15A or 1.5 times the nameplate current for 5 seconds. In Canada, the protective earth must pass 30 A or 2.0 times the nameplate current for 2 minutes. Typically, manufacturers of U.S. products test the protective earth with the Canadian requirement since most products are common between the two countries.

2.2.3.4 Output Voltages of Medical EPSs

Another safety requirement for medical EPSs is lower output voltages. EPSs for ITE products can have a DC output voltage as high as 60 V. However, medical EPSs do not go above 30 V to have a safety extra low voltage (SELV). However, it is possible for medical EPSs to have higher output voltage, but that would require additional levels of protection. Typically, medical EPSs have an output voltage between 18 V and 30 V.

Some medical EPSs have two or more output voltages. Multiple voltages are useful when there are different voltage requirements for different circuits within the medical device. For instance, logic circuits might require voltages around 3.3 V to 5 V whereas a pump or motor might require 12 V to 30 V. Currently, the trend is that manufacturers prefer single­voltage medical EPSs over multiple­voltage ones. This is because there is an increasing amount of logic

2­5circuits in medical devices, each with a different voltage requirement. Consequently, it becomes less attractive for the medical EPS to have an increasing amount of output voltages. Rather it’s simpler to have an EPS with one high output voltage and many local DC­DC converters within the product for smaller voltages. Nonetheless, multiple­voltage EPSs continue to be used with legacy products as well as products with motors and pumps, which consume large amounts of power and require isolation from logic circuits. In terms of energy efficiency, multiple­voltage medical EPSs face the combined challenges of multiple­voltage ITE EPSs and single­voltage

medical EPSs.

2.2.3.5 Leakage Currents in Medical EPSs

In addition to having levels of protection and lower output voltages, medical EPSs have restrictions on leakage currents. The limits depend on the type of leakage current, the operating condition, the degree of protection against electric shock, and the type of medical equipment. The leakage current can be through the ground pin, to ground via the patient from the enclosure, or to ground through the patient from an applied part. For the operating conditions, the maximum allowable leakage current is lower in the normal condition than in the single fault condition. The degrees of protection are classified as type B, BF, or CF. Type B provides a basic degree of protection and the applied part may be directly connected to ground. Type BF has a higher degree of protection, where the “F” indicates that the circuit is floating with respect to ground. Type CF is typically used with cardiac applications and offers even more protection; again, the “F” denotes that it is floating. Patient care equipment and portable equipment are two types of medical equipment, each with different ratings for leakage current.

For example, Table 2.1 shows the maximum leakage currents for portable equipment. The table indicates that for a Type BF device in the normal condition, 100 �A is the maximum current that can flow through the patient from the enclosure or from the applied part. If the device were type CF, the enclosure limit would still be 100 �A, but the maximum leakage current from the applied part would be 10 �A, which is very restrictive.

Table 2.1 Maximum Leakage Current for Portable Equipment f

Leakage

Current Type B Type BF Type CF

Normal

Condition Single

Fault

Condition Normal

Condition Single

Fault

Condition Normal

Condition Single

Fault

Condition

Earth Leakage

Current 500 uA 1 mA 500 uA 1 mA 500 uA 1 mA

Enclosure Leakage

Current 100 uA 500 uA 100 uA 500 uA 100 uA 500 uA

Patient Leakage

Current 100 uA 500 uA 100 uA 500 uA 10 uA 50 uA

f Taken in September 2008 from http://www.xppower.com/page.php?pagename=Medical&lang=EN

2­6The medical device could cause leakage current to flow through the patient in two ways: the patient could be connected to ground or connected to mains power. The mains connection could happen due to a complete failure in another piece of equipment. A connection to mains will not harm the patient as long as the patient remains isolated from ground so that no current flows. The patient could be connected to mains due to failure in another medical device or simply from the patient contacting liquid that touches a grounding source, such as a cold water tap. The medical EPS must not exceed the leakage current limits in either scenario.

In the design of medical EPSs, the tighter leakage current limits trade off with more lenient electromagnetic compatibility (EMC) requirements. There are two classes of EMC: Class A, for industrial and medical applications, and Class B, for commercial applications. As compared to ITE products, medical products have more lenient EMC limits. However, another concern for medical EPSs is the ranges of frequencies to avoid, known as keep out frequency ranges. For example, several major medical equipment manufacturers have established such ranges to ensure that the power supply switching frequency does not interfere with ultrasound equipment.

2.2.3.6 Maintaining Safety Certification

To obtain safety certification, the EPS must document that it meets all of these safety requirements. Some manufacturers need up to a year to complete the testing and documentation. Once certification is achieved, the EPS design is fixed. No component can be changed without a justification and re­certification of the entire EPS.

2.2.4 Particular Functionality of EPSs for BCs

In its framework document for BCs and Class A EPSs, DOE describes different approaches for considering a BC wall adapter to be an EPS for BC. g Specifically, DOE is considering Approach A which considers BC wall adapters with constant­voltage output to be

EPSs for BCs. In that case EPSs for BCs have the same electrical characteristics as Class A EPSs; the only difference between the EPSs is their end­use applications.

2.2.5 Electromagnetic Interference Suppression

There are two types of EMI when dealing with external power supplies. The two categories of interference are differential mode and common mode noise. What distinguishes the two is the manner in which the interference is manifested in the circuitry and transmitted to AC mains. Since the two types of noise develop differently, designers have different solutions that reduce the effects of the noise that is generated. The FCC and European entities established electromagnetic interference (EMI) limits among those frequencies allocated to commercial broadcasting and to short wave transmissions used for communication purposes.

g U.S. Department of Energy­Office of Energy Efficiency and Renewable Energy. Energy Efficiency Program for Consumer Products: Public Meeting and Availability of Framework Document for Battery Chargers and External Power Supplies. Federal Register . June 4, 2009. vol. 74, No. 106: p. 26816.

2­7Differential mode noise is associated with the switching frequency of an EPS as well as the first few upper, odd harmonics of that frequency. Those harmonics that fall into the broadcast bands are the frequencies of most concern. The general range of the broadcast band is 550 kHz to 1650 kHz and is the broadcast band of AM radio. To suppress the effects of this type of EMI designers may add one or two, non­polarized capacitors (or “X” capacitors) across the AC mains input and an inductor filter (or differential­mode choke) in one of the AC input legs can help reduce the noise. Figure 2.1 shows the circuit diagram of an EMI filter that employs two “X” capacitors, C1 and C2, and a differential­mode choke, L2.

The second type of noise, common mode noise, is created throughout the EPS circuitry. It occurs when fast rising pulses are coupled, via parasitic capacitance and inductance to other circuit elements and incoming AC wiring separate from the switch. Parasitic capacitance is the stray, unavoidable capacitance that exists between circuit elements. Common mode interference is generally seen at frequencies from 1 MHz up to 30 MHz. To combat this interference designers use a common mode choke on the AC input lines and a capacitor connected from each of the AC lines to ground, called a “Y” capacitor. Figure 2.1, shows the circuit diagram of an EMI filter that employs a pair of Y capacitors, C3 and C4, and a common mode choke, L1.

Figure 2.1 Example Circuit of an EMI Filter

Parasitic capacitive coupling among components can cause interference to be radiated around the common mode choke and appear at AC mains. To avoid this, sometimes an EMI filter like that shown above can be placed externally to the EPS. This filter is placed between the AC main power and before the input to the EPS. That way AC main power can only enter the EPS after passing through the filter.

When designers make these additions to their EPSs, cost and size are the two most important considerations. To stay competitive, EPS manufacturers want to keep both of these characteristics to a minimum, while also meeting necessary EMI standards. The impact of additional cost and size of these electrical components becomes greater for EPSs with higher output powers. This is especially true of the “X” capacitors and both choke cores, whereas the size and cost of the “Y” capacitors will remain relatively constant. For example if the value of

2­8the common mode and differential mode choke were to triple, the physical size could be as much as 10 times larger and 5 to 7 times as expensive.

The FCC and the European Union (EU) have set limits for electromagnetic interference. The European standards are more stringent than those set by the FCC and are generally the specifications that manufacturers, even those in the United States design to. The reason U.S. EPS manufacturers still use the EU limits is that their products are designed for possible global consumption. For this reason, many U.S. products have labels declaring conformity with the standards set forth by the EU in EN 55022.

The issue of noise is of particular importance for high power EPSs used in ham radio applications and is discussed in detail in section 2.3.10 below.

2.3 Circuit Design of EPSs

2.3.1 General Design of an External Power Supply
EPSs must meet several specifications in order to power a consumer product; EPSs are generally designed to provide power at a fixed output voltage with variable current to a consumer product. The consumer product is what determines the EPS design criteria, including output power, output voltage, and the tolerance of the output voltage. EPSs designed for consumer products that require precise voltages ( e.g. , computers) will also incorporate output voltage regulation to minimize voltage fluctuations caused by load or power source variations. Other applications that can tolerate some voltage fluctuation may use simpler EPSs that do not regulate the output voltage. Also, EPSs might have other specifications, such as total harmonic distortion or power factor.

Of all these specifications, output power and output voltage have the largest impact on EPS efficiency, because together they determine the output current, which directly affects conduction losses and associated power dissipation in the EPS.

External power supplies can have different topologies for power conversion and regulation (Figure 2.2). Line­frequency EPSs have that name because the frequency of the current passing through their transformers is the same as that of the AC mains current (nominally 60 Hz in the United States). Switched­mode power supplies (SMPS) convert power differently than line­frequency EPSs. SMPSs first rectify the AC mains voltage to DC, converting it to pulsating DC by switching the current on and off at high frequency. The high­frequency pulsating DC current passes through the primary winding of a transformer where it appears as a high frequency AC voltage. The high frequency output from that secondary winding of the transformer is rectified by high frequency diodes, resulting in a low­voltage DC output. Because the pulsating current passing through the transformer is at high frequency, the transformer is smaller, resulting in lower weight, material costs, and losses in the transformer, all of which

decrease with transformer volume.

2­9GENERAL EXTERNAL POWER SUPPLY TOPOLOGIES

­

POWER CONVERSION REGULATION TYPE

Line­Frequency Unregulated

Linear­Regulated

­

Switched­mode

­ SwitchingRegulated

­

Figure 2.2 Topologies for External Power Supplies

2.3.2 Design Choice: Single Versus Multiple Voltage EPSs
Consumer electronic products often use external power supplies and typically require different voltages within the product. As can be seen in Figure 2.3 the multiple voltages can be generated either inside the EPS or inside the consumer product. If generated inside the consumer product the EPS typically provides only a single output voltage (Figure 2.3b). Sometimes all of the voltages are generated outside the product, as in Figure 2.3a, or the design involves a combination approach with a multiple­voltage EPS and additional voltage regulation within the product (Figure 2.3c).

2­10Multiple DC

**AC Mains**  **Multiple­Voltage** AC **Subsystems**

**Subsystems**

**EPS Consumer** 

**Product**

a.

Single DC

**AC Mains**  **Class A**  **Single** AC **Volt. Reg.** 

**Volt. Reg.**  **Subsystems**

**Subsystems**

**Voltage EPS**  **Consumer**

**Product**

b.

Multiple DC

**AC Mains**  **Multiple­Voltage**
**EPS** AC **Volt. Reg.** 

**Volt. Reg.**

**Subsystems Subsystems** 

**Subsystems**

**Consumer**

**Product**

c.

Figure 2.3 Power Distribution Configurations for Consumer Products With Subsystems Requiring Different Supply Voltages

There is an increasing trend for consumer electronic products that use external power supplies, to use single­voltage EPS and create any additional voltages inside the consumer product itself with DC­DC converters. Because of this most consumer electronic products for sale today either use internal power supplies or a single­voltage power supply, followed by one or more voltage regulators. However, there remain two important consumer applications that continue to use multiple­voltage EPSs: video­game consoles and printing applications, which are discussed in section 2.2.1. In addition, DOE is aware of external hard drives, inkjet printers, security equipment and medical equipment that also might use multiple­voltage EPSs, although

their use is uncommon.

2­112.3.3 Class A AC/AC External Power Supplies
An AC/AC external power supply, a type of Class A EPS, is the simplest type of EPS, typically consisting only of a transformer and only one output voltage. A transformer contains two wires, each wrapped a number of times around a metal core, and as current passes through the primary wire, power is transferred to the secondary wire at a lower voltage through magnetic induction in the core. The size of the wires and core depend on the output power of the transformer. The output voltage is dependent on the turns ratio, which is the ratio of the number of times the primary wire is wrapped around the metal core to the number times the secondary is wrapped around the metal core. The windings of the transformer are wound so that the voltage generated in the secondary wire is at the design voltage for the consumer product when mains voltage is applied to the primary wire. Because the primary and secondary windings are two separate wires, the transformer also provides a safety function, electrically isolating the consumer product from the mains. The key factors that determine transformer losses are core size, core material, number of windings, and wire gauge.

Figure 2.4 Circuit Diagram for an AC/AC External Power Supply

2.3.4 Class A Unregulated Line­Frequency AC/DC External Power Supplies
An unregulated line­frequency EPS is referred to as a “raw supply,” which has three distinct stages (Figure 2.5): a transformer to isolate and step down mains voltage, a rectifier to convert AC voltage to a pulsating DC voltage, and a filter capacitor to smooth the output voltage. The two main sources of loss are the transformer and the rectifying diodes. After passing through the transformer, current passes through rectifier diodes, which have voltage drops that also dissipate power. Typically, diodes have a drop of 0.8 –1.2 volts, if Schottky diodes are used these drops are less, around 0.6 volts. These drops constitute a proportionally larger share of the losses at lower output voltages. For AC­DC EPS that have a low output voltage, below approximately 12 V, the power consumed by the diodes also becomes significant in that it is more than 10% of losses, if the rectifier is a bridge with two diodes.

2­12Figure 2.5 Circuit Diagram of a Line­Frequency Raw Supply

The raw supply is directly responsive to the load: A change in the mains power or the resistance of the load directly affects the output voltage of the raw supply. If required, a regulator circuit follows the raw supply circuit, housed either in the EPS or in the device before the load.

2.3.5 Class A Linear­Regulated Line­Frequency AC/DC External Power Supplies

To achieve voltage regulation, manufacturers can add a second stage, such as a linear regulator, to the line­frequency power conversion stage described above, or redesign the power conversion stage entirely using a switched­mode topology. Of the two regulator technologies, linear regulators are simpler, bulkier, cheaper, and generally less efficient at higher power levels than switching regulators. Switching regulators, although more complicated and costly, provide a good alternative when portability is a concern, such as when an EPS is used with a mobile phone.

The AC­DC conversion stage of a regulated line­frequency EPS is essentially the same as that of an unregulated EPS, with the same sources of power consumption. The linear voltage regulation stage adds to these losses by passing power from the AC­DC converter to the consumer product through a power­dissipating element. This regulation stage senses the output voltage and adjusts the voltage across the power­dissipating element to keep the output voltage fixed. Loss in a regulated line­frequency EPS is caused by the conversion stage delivering current at a higher voltage than needed by the consumer product, and dropping the excess voltage across the regulator to achieve the lower regulated output voltage. Dissipated as heat, the power lost in the regulator is the product of the voltage drop and the load current.

Linear regulators have two key elements: a sensor and a pass device, which work together to produce a fixed output voltage (Figure 2.6). To determine those adjustments, the sensor element continuously compares the output voltage to a reference voltage. Whenever there is a difference between the two voltages, the sensor directs the pass device to adjust the output in order to reduce that difference. This continuous adjustment allows the regulator to yield a constant output voltage as the load resistance or mains voltage varies. The output voltage of the linear regulator circuit is what the user sees as the output voltage of the EPS.

2­13Figure 2.6 Block Diagram of a Linear Regulator

Figure 2.7 shows a circuit diagram of a “low­dropout” linear regulator h , one of the more common types of linear regulators. To determine the voltage drop across the pass device, an operational amplifier (commonly referred to as an “op­amp”) acts as a sensor that compares the output voltage against a reference voltage. Based on those two signals, the op­amp controls a transistor, which is the pass device. The voltage drop across the transistor determines the output voltage but also dissipates energy. The energy dissipated by the pass device is the main source of energy consumption in the linear regulator, and hence the main source of inefficiency and heat generation. Together, the sensor and the pass device adjust the output of the regulator to produce a stable output voltage, which is what the load receives as the output voltage of the EPS.

Figure 2.7 Simplified Circuit Diagram of a Linear Regulator

The efficiency of the linear regulator, η LinReg , is:

h Low dropout simply means the minimal voltage drop across the regulator at its maximum current rating. A low dropout regulator has very low voltage drop at maximum current and can therefore be very efficient at that point.

2­14P V I LinReg

_ out LinReg

_ out LinReg

_ out η = = Eq. 2.1

LinReg P V I LinReg

_ in LinReg

_ in LinReg

_ in

where

­ I LinReg_in is the current into the linear regulator,

­ I

LinReg_out is the current out of the linear regulator,

­ P

LinReg_in is the power into the linear regulator,

­ P

LinReg_out is the power out of the linear regulator,

­ V

LinReg_in is the voltage into the linear regulator, and

­ V

LinReg_out is the voltage out of the linear regulator.

­

Because the linear regulator directly attaches to the raw supply, V LinReg_in is equal to

V

RawSupp_out , the output voltage of the raw supply.

Because the input current flows directly to the output through the pass device, with other currents being negligible, I ≈ I

_ in . Therefore, the efficiency of the linear regulator LinReg

_ out LinReg alone is approximately:

V

LinReg

_ out η ≈ Eq. 2.2

LinReg V LinReg

_ in

The total efficiency of an EPS with a linear regulator depends on the efficiency of both the linear regulator stage and the raw supply stage. Depending on the load conditions, η LinReg generally ranges from 0.6 to 0.8, meaning the linear regulator is about 60 to 80 percent efficient. The efficiency of raw supply, η RawSup , also varies with load, generally from 0.7 to 0.9. The raw supply and linear regulator each are most efficient at different load conditions. Multiplied, η LinReg and η RawSupp yield the total efficiency of an EPS with a linear regulator, η Lin_EPS , which is generally about 50 percent, but is lower for EPSs with output power below 10 W:

η = η * η Eq. 2.3

Lin

_ EPS RawSupp LinReg

2.3.6

­ Class A Switching­Regulated Line­Frequency AC/DC External Power Supplies
An alternate to a linear regulator is a switching regulator that can also follow the raw supply (Figure 2.8). Switching regulators tend to be much more efficient than linear regulators because they do not dissipate excess power. Rather, to regulate output they take power as necessary to maintain constant output voltage. Due to their higher costs, these switching regulators tend not to be as common as linear regulators as an auxiliary regulator, since it is

2­15typically more cost­effective to use a switched­mode power supply design in the first place, in which case there is no need for an auxiliary regulator.

Figure 2.8 Block Diagram of a Switching­Regulated Line­Frequency AC/DC EPS

2.3.7 Switched­Mode AC/DC External Power Supplies
A switched­mode power supply consists of five stages: a 60Hz AC­DC conversion stage,a high frequency chopper stage, an energy transfer stage, a control stage, and an electricallyisolated feedback stage (Figure 2.9). First, the current is rectified and passed to the chopper, which converts the 120­Hz­pulsing DC voltage to pulsing DC, but at high frequency. The energy transfer stage (transformer) then takes energy from the chopper, briefly stores it, reconstitutes it as high frequency AC and then passes it to the rectifier to be the output to the consumer product. The energy transfer stage also serves to isolate the user from the mains. The level of the output voltage is fed back through a feedback isolation stage to the controller, which tracks the output voltage and adjusts the chopper duty cycle or frequency to set the desired voltage.

Figure 2.9 Block Diagram of a Switched­Mode Power Supply

The critical elements in a switched­mode EPS are the transistor, output rectifier, bulk capacitor, transformer, and controller. A transistor acts as a switch that constrains the flow of power rectified from mains into the transformer (or choke), through the output rectifier, and, ultimately, to the consumer product. A controller, typically an integrated circuit (IC), switches the transistor on and off based on the output voltage. By adjusting the duty ratio, the IC controls the rectified mains current into the primary winding of the transformer and thereby the output voltage of the EPS. The IC can also limit power dissipation in active mode by reducing

2­16switching at low current or low voltage. Further, the IC can greatly increase efficiency by reducing power consumption in no­load mode, the condition when the EPS has been disconnected from the load, resulting in zero output current. After passing through the transformer, the current is rectified and filtered before reaching the consumer product. Principal sources of loss in a switched­mode EPS are the transistor on­state resistance and capacitive switching dissipation, magnetization, and resistive losses as a result of transformer current, controller IC power consumption, and rectifier losses. Although there are more sources of loss for switched­mode EPSs than line­frequency EPSs, in total, losses in switched­mode EPSs tend

to much lower.

The switching regulator usually consists of an integrated circuit controller and discrete components. The circuit diagram in Figure 2.10 depicts a “flyback” switching regulator, the most common type for EPSs used with consumer electronics; however, many other switching regulator designs also exist. The AC/DC conversion stage consists of a diode bridge and filter capacitor, similar to a raw supply. In this case, current flows directly from mains to the diode bridge, rather than through a transformer.

The chopper stage uses a transistor, which switches on and off at high frequency to convert the DC current from the AC/DC converter back to a pulsating DC current for the energy transfer stage. A control stage drives the transistor; the duty cycle of the transistor determines how much energy is transferred through the energy transfer stage. The switching frequency is in the kilohertz range, with lower frequencies having lower switching losses. The minimum frequency is virtually always 20 kHz (typically above 50 kHz) above the audible range of human hearing.

Figure 2.10 Simplified Circuit Diagram of a Flyback Switching Regulator

The energy transfer stage consists of a transformer, a capacitor, and a diode. The choke is similar to a transformer and has the same symbol in the circuit diagram. One difference is that a transformer in a line­frequency EPS using a forward converter topology is designed to pass energy from one winding to another with minimal energy storage, while a transformer in a

2­17flyback­topology switched­mode EPS is designed to store and release energy, similar to a way a choke. A typical forward converter requires a transformer but also an output filter choke. The less expensive flyback accomplishes the transformer and choke function in one component. The flyback approach creates additional undesirable output ripple that is typically acceptable in lower cost EPS units. Also, the phasing of the windings is not important in the line­frequency transformer, but it is critically important in the flyback switching regulator. This is represented in Figure 2.10 by dots on the transformer.

When the chopper switch is closed, the primary winding of the transformer takes energy from the chopper and stores the energy in the transformers. When the chopper switch opens, the secondary winding transfers that energy through the diode to the capacitor and provides the output for the switching regulator, electrically isolating the load from the mains. Because the transformer operates at a high frequency, it benefits from the associated decreases in size and weight. The energy transfer scheme of the switching regulator is more efficient than a linear regulator, in part because the transformer, doubling as a choke, stores and returns energy with relatively low losses.

The feedback isolation stage typically uses an optocoupler that consists of a light source and a photosensitive detector. By converting the electrical feedback signal to an optical one, the optocoupler maintains the load electrically isolated from the mains. The detector converts the optical signal back to an electrical signal for the controller.

Generally, the controller is an integrated circuit that drives the chopper with a highfrequency pulse­width­modulated (PWM) waveform. The controller monitors the EPS output voltage and adjusts the pulse width to increase or decrease the amount of energy transferred by the chopper. If the output voltage dips, the controller will increase the duty cycle, thus increasing the energy passed by the energy transfer stage and increasing the output voltage. Conversely, if the output voltage rises, the controller will decrease the duty cycle or possibly skip cycles. This cycle­skipping feature is especially useful at low­load or when there is no load attached, because the EPS will only take from the mains the small amount of power it needs to keep itself running.

As an alternative to an IC controller, a switched­mode EPS can also use discrete components, as in the case of a ringing choke converter. In that topology, discrete transistors control the chopper and the resulting energy transfer. EPSs without ICs tend to be more common at lower output powers. However, by not having an IC, the EPS may consume less overhead power, but offers less functionality, such as cycle­skipping at low load, which can limit EPS efficiency.

2.3.8 Design of Output Cables

Cable losses are related to the output power and output voltage of the external power supply as well as the resistance of the output cable, based on its materials, length, and gauge. This relation can be expressed in the following equation:

2­182  P  2

OUT  P

LOSS = I OUT R =  R

, Eq. 2.4    V OUT 

where P LOSS is the power lost in the output cable,

I

OUT is output current, power, voltage,

P OUT is the output power,

V

OUT is the output voltage, and

R is the cable resistance.

2.3.9 Particular Designs of Multiple­Voltage EPSs

As described previously, multiple­voltage external power supplies can be divided into two different groups by number of output busses capable of delivering power to the load. The first group, which has only one output bus and one or more auxiliary signal outputs, are designed fundamentally the same as single­voltage external power supplies: the power conversion process is the same, but the EPS contains additional circuitry that provides the added signal outputs necessary for device operation. Although this signal circuitry is not in the power conversion path, it requires power to perform its function, affecting the efficiency of the EPS. Therefore, the strategies for improving the efficiency of this group of multiple­voltage external power supplies would focus on improving the efficiency and no­load power of the power­conversion process, as analyzed for single­voltage EPSs and/or reducing the power consumption of the circuits driving the auxiliary outputs. However, the power supplies in this group do not appear to be in the market; therefore they were not analyzed further in this determination analysis.

The other group consists of EPSs that, in addition to any auxiliary signal outputs, have multiple power outputs at two or more voltages that operate load subsystems with differing supply voltage requirements. These EPSs power applications such as multi­function devices and video­game consoles, and can generate their multiple output voltages in several different ways: (1) through additional regulators connected to a single tap, (2) through multiple taps of a single transformer winding, (3) through multiple windings on a single core, and (4) through multiple

cores.

In each of the approaches—described in detail below—the power conversion stage utilizes either a line­frequency or switched­mode high­frequency design. Similarly, in the case of a line­frequency power conversion stage, voltage regulation at the output can be performed either not at all (e.g., in the case of an AC­AC EPS) or using linear or switching voltage regulators.

2.3.9.1 Additional Regulators from a Single Tap

Topologically, this circuit approach is similar to using a single­voltage EPS followed by post­regulation, except the voltage post­regulators are located inside the external power supply rather than the consumer product. Although employing this approach as opposed to the one in

2­19Figure 2.3.b may decrease the size of the consumer product, it has numerous disadvantages such as a thicker and heavier output cable with multiple conductors, higher losses in the output cable, and higher minimum tolerances on the output voltage, such that this approach is not commonly seen in practice.

2.3.9.2 Multiple Taps

In its simplest form, a transformer couples the magnetic flux in a pair of windings, relating the AC voltage across the two windings by their turns ratio, such that:

N 1

= v 1

, Eq. 2.5 N 2 v 2

Where N i is the number of turns and v i is the voltage of each winding.

Rather than just obtaining the output voltage from the two ends of the secondary winding, it is also possible to place a tap at an intermediate point along the winding, in which case the location of the tap along the winding proportionally determines the voltage across the winding. For example a transformer with a 10:1 turns ratio and 120 V across the primary would have a secondary voltage of 12 V, whereas a tap placed in the middle of the winding would provide 6 V across each half of the winding. By placing additional taps, further voltages can be obtained from the secondary winding.

Because the secondary voltages are related to each other by the turns ratio, it is possible to forgo the multiple voltage regulators—one on each output—of the previous approach. For example, in a switched­mode design, the voltage on the primary output is fed back to the control circuit that determines the duty ratio of the primary­side switch and the voltage across the primary side of the choke, the high­frequency transformer used in switched­mode designs. The output voltages across the secondary winding is distributed among the outputs proportionally, depending on the location of the tap or taps along the windings, so the closed­loop feedback regulation of one output results in some degree of regulation of the other outputs. An illustration of this approach can be found in Figure 2.11; the design in the Figure economizes on parts by eliminating the regulator that would otherwise be employed on the +12 V output.

2­20**­12**

**+12**

**+5 AC**  **POW ER** 

**FILTER LINEAR** 

**REG.**

**LINEAR**

**REG. FILTER** 

**LINEAR**

**REG. FILTER** 

202 BLOCK DIAGRAM

Figure 2.11 The second winding is center­tapped, providing multiple voltages

Although this approach results in a reduction in the number of components, it may not provide sufficient voltage regulation of the secondary outputs, and secondary post­regulation may be used on those outputs. For example, although the closed­loop feedback may provide a constant voltage to within 1% on the primary output, it may only provide cross­regulation to within 5% on the other outputs. Furthermore, this approach cannot be used to minimize the number of post­regulators in line­frequency designs, where the voltage across the primary is provided directly by the AC mains and not controlled by feedback from one of the outputs.

2.3.9.3 Multiple Windings

Rather than provide a center tap, it is also possible to provide multiple windings on the secondary side of the transformer. These windings share the same core, but are not electrically connected with each other, which allows the resultant output busses to be isolated from each other, with different grounds. i This may be necessary if the application requires isolation between the circuits supplied by each output. Alternatively, even if it does not, a power supply that provides separate grounds that are later connected inside the product itself reduces the interference between circuits powered by each output bus. These benefits must be weighed

i A ground is typically the lowest potential point in a circuit through which current returns to the supply, having performed useful work in a circuit.

2­21against the increased complexity and cost of the transformer and output cable with multiple ground leads. Figure 2.11, for example, shows a line­frequency design that combines the two approaches: it contains two windings, one of which is center­tapped.

Like the center tapped­designs described earlier, EPSs with multiple windings can also be designed with fewer voltage regulators than outputs because of cross­regulation between regulated and unregulated outputs. As before, the applicability of forgoing some voltage regulators depends on the output voltage accuracy requirements of the particular consumer product application, and it is not always seen in practice. Again, cross­regulation will generally not work with line­frequency designs because of the circuit’s inability to control the primary voltage. One exception would be a line frequency design with an AC pre­regulator. With a stable AC input voltage at the primary, the unregulated voltages will be much more stable. Linear regulators may still be used, but they will operate with consistently small voltage drops

and much lower losses.

2.3.9.4 Multiple Cores

A final approach to the design of multiple­voltage EPSs involves power supplies with multiple windings on multiple cores. This approach not only guarantees isolation between the different voltage outputs, but also allows the outputs to be operated independently. This allows for the operation of a portion of the EPS to be suspended when a particular output is not needed by the consumer product—for example, when the subsystem powered by the output is in standby mode. The result, depending on the design and usage of the consumer application, could be decreased losses at low loads as unused cores, and all the associated circuitry, shut down.

The potential gains in efficiency come at a fairly high cost, as two transformers will require more core material than one transformer of equivalent power. Furthermore, in the case of a switched­mode design, each core will require its own duplicate switch and PWM controller with associated circuitry such as a snubber and an optocoupler. In this approach there are, to a significant degree, separate switching power supplies inside one enclosure. The only thing in common is that the multiple sections receive their rectified/filtered AC mains voltage from a common “front end.” The “front end” may consist of the basic AC conversion block as seen in Figure 2.10 or an AC/DC conversion stage that also incorporates power factor correction. Finally, to shut down individual outputs based on application needs requires communication between the application and the power supplies, adding further complexity and cost to the design. However, this design has been observed in practice, and is illustrated in Figure 2.12. This approach is often found where the equipment to be powered requires more than one output voltage of comparable power and voltage tolerance.

Typical digital­circuit­oriented electronic equipment will generally require the largest portion of power for low voltage logic circuits, a smaller portion for mechanical devices or display circuits, and an even lower portion for what are often called “biasing” or control circuits. In these situations, these combined “auxiliary” outputs are typically much less than 50% of the total power and can be derived with auxiliary regulators without great efficiency penalty. However, sometimes a second output does not require logic type voltages, but nevertheless requires a large amount of tightly regulated, efficient power, just as the primary output does. In such a case, a second independent power “loop’ is called for.

2­22**RECTIFIER**

**FILTER**

**SWITCH FILTER**  **PWM**

**CONTROL**
**ON \**  **OFF**

**CONTROL**

**+5 STANDBY**  **+12**

**PWM**

**CONTROL SWITCH**  **INRUSH**

**LIMITER AC** 

**POWER** 

# .

. . . .

**203 BLOCK**  **DIAGRAM**

Figure 2.12 Multiple­Voltage EPS Design with Multiple Independent Cores, Which Allow the Operation of One of the Outputs to be Suspended When Not Needed

2.3.10 Particular Designs of High­Power EPSs

Similar to other classes of EPSs, high­powered EPSs can be categorized based on their design as either line­frequency or switched­mode. Line­frequency power supplies arecharacterized by a relatively large, 60­Hz, transformer performing the isolation and voltage stepdown functions, followed by rectification and post regulation using either a linear or switchingregulator. At lower power levels these linear­regulated EPSs are less expensive than switchingregulated EPSs because of their lower component count and less reliance (if at all) on integrated

circuits for control.

However, as the output power increases, the line­frequency transformer must become physically larger to accommodate saturation, necessitating an increase in wire size to carry higher current. This adds steel and copper to the power supply which causes it to become larger, heavier, and more costly. Switched­mode EPSs also become more expensive at higher output power levels; however, their cost is not as dependent on output power partly because fixed costs account for a larger proportion of the total cost. Therefore, their cost increases at a slower rate than line­frequency models. There is an additional factor which did not exist 20 years ago, but is a major consideration today. Global standardization today makes it virtually mandatory that

2­23power supplies above 100 watts employ power factor correction. Doing this with power supplies employing 60Hz magnetics becomes size and cost prohibitive. On the other hand power factor correction circuits for switching power supplies are now standardized, require minimal space, and are relatively inexpensive, adding about a five to seven percent increase in material cost. The present global standards not only dictate high power factor, but also the minimization of harmonic generation. So, from a regulatory standpoint there is a decreasing global acceptability of higher power EPS units that use 60 Hz magnetics. In the end, at higher power levels switched­mode EPSs eventually become not only more efficient, but also less expensive than line­frequency EPSs. Nevertheless, both of these topologies are commonly used for ham radio applications.

The use of line­frequency EPSs is in stark contrast with other segments of the EPS market, where it is difficult to find a line­frequency EPS with an output power above 10 W. The reason, touched upon previously, is electromagnetic interference or noise. Switched­mode designs use a high­frequency PWM controller to switch current rapidly through the EPS. Despite circuit measures such as filtering, these high­frequency currents both couple to the input and output of the power supply, where they appear as high frequency noise up to 30 MHz, creating fields that radiate from the switching circuitry. From there, the conducted and radiated energy can either be radiated with the input or output cable serving as antennas, or conducted directly into the load, causing undesirable interference. Even though these devices are designed to meet the regulations for class B digital devices set forth in Part 15(B) of the FCC regulations, they may still be unable to operate ham radio equipment, which requires the amplifying of weakexternal signals that may be corrupted by power supply emissions. Therefore, even though linefrequency EPSs are expensive and less efficient at high­power levels, they are still in use because they are not as electrically noisy as switched­mode EPSs. They also remain popular because of their relative simplicity and maintainability.

2.3.10.1 Line­Frequency Designs for High­Power EPSs

Line­frequency EPSs are sometimes preferred for lower noise and emissions. Their efficiency can be improved with the use of either manual or automatic transformer tap switching. This minimizes the amount of voltage dropped across the linear regulator pass element. Another approach is line frequency switch mode, usually with silicon­controlled rectifiers (SCR) phase control, although, the use of SCRs is not as common now, because of the advent and availability of power MOSFETs. Again, the raw supply voltage into the linear regulator is kept low, to minimize the voltage drop and losses in the pass element. The switch frequency is usually twice the line frequency, so 120Hz for a 60Hz line. Switched­mode designs are discussed in the

sections that follow.

2.3.10.2 Switched­Mode Designs for High­Power EPSs

Switched EPSs use several different topologies, depending on the output power level, as shown in Figure 2.13. Of the different switching­regulated EPS topologies, those employing a “forward” converter, as opposed to a “flyback” converter are geared more towards high­power applications. There are fundamental differences between forward and flyback converters. The main difference between forward converters and flyback converters is that forward converters transfer energy to the secondary side of the transformer when the switching transistor is turned

2­24on, whereas in a flyback EPS the energy transfer is done when the switching transistor is off. After the transformer in the energy transfer stage of the switching regulator there is a high speed diode and a ripple­filtering capacitor for flyback converters. In forward converters, there is a similar diode, (but usually a pair of them,) a similar ripple­filtering capacitor, as well as an output inductor.

The presence or absence of the separate inductor is the most obvious difference between the two topologies. Often there is very little other substantive difference. However, the transformer core of a flyback converter usually requires a gapped core while the forward converter does not. The necessity for the gap restricts the options for choice of magnetic designs. This means that in certain situations or at certain power levels it may not be obvious which of the two methods the better option is. At higher power, the flyback approach can also be more prone to electrical noise generation.

These extra components are shown in Figure 2.14. There are four types of forward converters used in high­power switched­mode EPSs: two­transistor, push­pull, half­bridge, and full­bridge. Figure 2.15 is an example of a push­pull topology.

SWITCHED­MODE TOPOLOGIES

­ and corresponding power levels

­

High­Frequency

­ Switched­Mode

­ Flyback

<125 W

Forward One­transistor

100 to 200 W

Two­transistor

150 to 600 W

Push­pull

<1000 W

Half­Bridge

150 to 600 W

Full­Bridge

>500 W

Figure 2.13 Switched­Mode Topologies and Corresponding Power Levels

­

2­25Figure 2.14 Two­Transistor Forward Converter Circuit

Two­Transistor Forward Converters

The two­transistor forward converter layout is shown in Figure 2.14, above. This topology is typically used for 150 W to 600 W power supplies. In contrast to the following three topologies, this design is asymmetrical, meaning that the secondary of the transformer is not center tapped—i.e., the current only flows in one direction in the primary during energy transfer.

One­transistor forward converters are used, but are generally used in lower power supplies. The voltage stresses on the single switch are about double the stresses on the switches in the two­transistor forward converter. Although, current technology has allowed the development of transistors that are designed for high voltage situations and thus, eliminate much of the switching related device stresses. The designer has to weigh the added cost of the higher voltage switch (one­transistor circuit) against the cost of providing floating gate drive for the upper switch (two­transistor circuit). At power levels where the flyback topology is no longerthe best choice, the single transistor forward circuit is used. As power levels increase, the twoswitch topology becomes the better choice.

Push­pull Converters

In the push­pull converter topology, the primary and secondary sides of the transformer are connected symmetrically or center tapped as shown in Figure 2.15 below. Again, two transistors are used on the primary side. A controller turns the transistors on sequentially, with a short period of downtime in between to prevent simultaneous conduction. This causes a polarity change in the voltage across the transformer which maximizes energy transfer. While either transistor is on, energy is provided to the secondary side of the transformer. When the two transistors are off, the diodes on the secondary side act as snubbers to carry the output inductor current. The push­pull circuit transistors have the same voltage stresses as a single transistor forward circuit, about double Vin. Good use is made of the transformer core but primary side utilization is poorer than in the half and full bridge converter circuits.

2­26Figure 2.15 Push­Pull Converter Circuit

Half­Bridge Converters

The operation of the half­bridge converter, shown in Figure 2.16 is very similar to the push­pull converter. However, in this topology the primary is not center­tapped and there are two capacitors that cause only half of the voltage to apply to the primary side of the transformer. Because of this, the half bridge converter is not used in applications requiring as much power as the push­pull converter, and like the two­transistor converter, this design is most commonly used in power supplies providing between 150 W and 600 W.

Figure 2.16 Half­Bridge Converter Circuit

Full­Bridge Converters

Figure 2.17 below shows the full­bridge converter topology. It is very similar to the halfbridge converter, only the two capacitors prior to the transformer have been replaced with two more transistors. In this setup, the transistors work in pairs (1, 3 and 2, 4). These transistor pairs are then alternatively driven by a controller. The full­bridge converter provides two times the

2­27output power of the half­bridge converter and is therefore more useful in very high­power applications, above 500 W.

Figure 2.17 Full­Bridge Converter Circuit

2.3.11 Particular Designs of Medical EPSs

As described in section 2.2.3, medical EPSs face a number of design constraints. These include longer lifetimes, long output cords, levels of protection from insulation or protective ground connection, limited output voltages, and maximum leakage currents.

Heat is the principle factor affecting the reliability and consequent lifetime of medical EPSs. The principal components that are susceptible to heat degradation over time are electrolytic capacitors, optocouplers, and integrated circuits. The EPS also dissipates heat through its components, particularly those that pass large amounts of current such as the transformer, switching transistor, and rectifier diodes. To mitigate against heat and extend the lifetime of the medical EPS, designs typically include MOSFETs with low R ds_on

.

Long output cords can be necessary for safety to separate the medical device from mains power. The main design option for the output cords is the wire gauge, which governs the resistance. Resistance, particularly for long output cords, can be a major source of loss, up to 10% for high­power, low­voltage medical EPSs.

Insulation and a protective connection to ground are two methods for providing a layer of protection. Insulation requirements typically affect spacing between components, but do not affect efficiency. One exception is for transformers where insulation spacing requirements between windings reduces efficiency.

Lower output voltages, particularly those below 10 V, tend to decrease efficiency; although the SELV limit of 30 V is high enough that it should not overly constrain the efficiency

of medical EPSs.

Maximum leakage currents have the largest effect on the design and efficiency of medical EPSs. The primary barrier to leakage currents from mains to the patient is at the barrier

2­28within the EPS between the primary (mains) and the secondary (output). Only a few components bridge both sides of that barrier: the transformer, an optocoupler, and a Y­capacitor, which is the largest conductor of leakage current. The transformer is the primary means of passing energy from mains through to the output. Leakage currents through the transformer can be reduced by increasing the insulation and spacing between the windings. An optocoupler provides feedback from the output to the controlling circuitry on the primary side. The optocoupler is not a significant source of leakage current. The purpose of the Y­capacitor is to reduce electromagnetic interference (EMI) and meet electromagnetic compatibility requirements. The Y­capacitor reduces EMI by shunting capacitive­coupled common mode noise generated between primary and secondary windings within the transformer. However, inductors at theinput and output terminals of the EPS can offer similar EMI reductions. By replacing the Ycapacitor with such inductors, either of higher inductance values or in greater number, the medical EPS can still meet EMC requirements and eliminate a major conductive path for leakage

currents.

2.3.12 Particular Designs of EPSs for BCs

j EPSs for BCs, as described in the NOPR, are electronically the same as Class A EPSs. Therefore, there are no unique design traits for EPSs for BCs beyond those discussed in subsections 2.3.1 through 2.3.8.

2.4 Technology Options for Improving Energy Efficiency

2.4.1 Transformers

For line­frequency BCs and EPSs, the largest losses are in the transformer, particularly at light loads. The most effective means to reduce transformer power loss at light loads is to select a transformer with higher quality core material and a lower level of magnetic induction. At line frequency, the transformer core material typically is thinly laminated steel alloyed with silicon. The amount of silicon affects the core power loss and the cost of the transformer. Core performance is enhanced by magnetically orienting the grain structure in the metal. The industry standard for common non­oriented grain­structure core material ratings range from M19 to M45, with the lower number having fewer electrical losses. M6 core steel is used in an energy efficient EPS transformer because it is a high­quality grain­oriented core steel that has very low electrical

losses.

The second important factor contributing to core loss is the level of magnetic induction. Core losses are measured in watts per pound (W/lb), and induction is given in kilogauss (kG). Induction levels in these devices typically range between 10 kG and 15 kG. Reducing the induction level will reduce the core losses, but increase the winding losses. Reducing the induction requires more wire turns and therefore a larger core for a given power rating. The trade­off of these improvements is the increased size and weight of the transformer, and ultimately the EPS. Table 2.2 shows the effects of material type and induction on core loss.

j U.S. Department of Energy­Office of Energy Efficiency and Renewable Energy. Energy Efficiency Program for Consumer Products: Public Meeting and Availability of Framework Document for Battery Chargers and External Power Supplies. Federal Register . June 4, 2009. vol. 74, No. 106: p. 26816.

2­29Power loss in the transformer core can be reduced by an order of magnitude by increasing the quality of the core steel and reducing the level of magnetic induction: 0.28 W/lb versus 3.1 W/lb.

Table 2.2 Quality of Core Steel and Level of Magnetic Induction

Steel Core Losses at Various Levels of Magnetic Induction

10 kG 12 kG 15 kG

M6 0.28 W/lb 0.40 W/lb 0.60 W/lb

M19 0.85 W/lb 1.2 W/lb 2.0 W/lb

M45 1.4 W/lb 1.9 W/lb 3.1 W/lb

Additionally, some primary transformer windings have high resistance to prevent failure in the case of overload conditions. Using a separate fuse or thermal cutout to prevent failure would allow the transformer to have a lower winding resistance, thus reducing electrical losses.

A large potential source of energy loss in a high­frequency EPS is the flyback transformer, similar to the transformer in line­frequency EPSs. Methods of improving the energy efficiency of chokes are similar to those for improving transformers, that is, improving the core material and increasing the amount of copper to reduce copper losses.

Particularly, for EPSs with output power greater than 10 W, a switched­mode power supply is generally a more efficient alternative to a line­frequency. At lower wattages, however, neither regulation technology has a clear efficiency advantage. This is partly because the switching regulator circuit components themselves consume some energy, regardless of the output power of the device. At lower wattages, this fixed energy consumption is a more significant proportion of total EPS energy consumption.

2.4.2 Diode Losses and Synchronous Rectification

Diodes are another source of loss for DC line­frequency EPSs. These losses increase as the output voltage decreases, and become particularly significant below 12 V. The power consumed by a diode is the product of the current flowing through the diode multiplied by the voltage drop across it. When a line­frequency EPS is designed for low­output voltage, that drop becomes a significant portion of the overall losses in the EPS. Using Schottky diodes k reduces the voltage drop across the diodes, thus improving efficiency. Conventional diodes have a voltage drop of about 1.0 V at typical operating conditions, which can be reduced to about 0.5­

0.6 V by using Schottky diodes.

Synchronous rectification offers even lower losses by replacing diodes with very low

R DS_ON MOSFET transistors. In this situation, the transistor mimics the rectification effect of the diode. However, the loss across the source­to­drain resistance of the transistor is much lower

k A Schottky diode is a metal­semiconductor diode with a smaller voltage drop than a conventional diode, therefore consumes less power.

2­30than that of a diode. When synchronous rectification is used, it is virtually always on the secondary side of the transformer in switched­mode EPSs because that is where it offers the most energy savings. In a switching power supply the output rectifiers typically constitute 50­60% of all semiconductor losses in the unit. Consequently, reducing rectifier losses by a factor of 2 with synchronous rectification is very meaningful.

2.4.3 Technology Options for Multiple­Voltage EPSs

All technology options for Class A EPSs are applicable to multiple­voltage EPSs.

2.4.4 Technology Options for High­Power EPSs

There are several generic technology options for all EPSs that can increase the efficiency of high­power EPSs, as well as some technology options explicitly for EPSs. Manufacturers use various topologies when designing their EPSs which can change depending on intended utility. Line­frequency, linear­regulated EPSs are generally the least efficient of the topologies created, but they are still common in communications because of their lower electromagnetic interference. There are ways to improve the efficiency of these power supplies; however, as efficiency becomes a greater concern, some users are also changing to switched­mode EPSs.

Even though noise is a concern with switched­mode designs, manufacturers can make switched­mode EPSs that meet FCC regulations on electromagnetic interference (EMI). This gives users a viable option if more efficiency is needed than an improved line­frequency EPS canprovide. DOE considered several technology options, some of which can be used on linearregulated EPSs and some of which are only applicable to switched­mode EPSs. DOE also considered switched­mode EPSs a technology option for increasing efficiency from levels achievable by line­frequency EPSs.

The technology options, discussed in detail previously and that DOE considered for improving the efficiency of high­power EPSs are:

• Improved Core Steel in Transformer

• Switched­Mode EPSs

• Multi­Mode Integrated Circuits

• Low­Loss Transistors

• Resonant Switching

• Schottky Diodes & Synchronous Rectification

2.4.5 Technology Options for Medical EPSs

All technology options for Class A EPSs are applicable to medical EPSs.

2.4.6 Technology Options for EPSs for BCs

All technology options for Class A EPSs are applicable to EPSs for BCs.

2­31CHAPTER 3 ENGINEERING ANALYSIS

3.1 Introduction

This chapter of Technical Support Document (TSD) contains information that supports and expands on the Engineering Analysis section of the Notice of Proposed Rulemaking (NOPR). Specifically it provides examples and additional details for DOE’s methodology for scaling cost and efficiency of non­Class A EPSs. The chapter also provides details on representative product classes, representative units, and candidate standard levels discussed in the NOPR. In addition, Appendix A includes the manufacturer interview guide that Navigant Consulting, Inc. used when interviewing manufacturers on behalf of DOE.

3.2 DOE Methods for Determining ERMC

In the engineering analysis, DOE focused on efficiency­related materials cost (ERMC). DOE scaled data when the tested units were different than the representative units. DOE needed to scale the data because, although it attempted to purchase units for testing and teardown that all had the characteristics of the representative units, it was not always possible due to limited product availability in the market and changes to the representative units’ characteristics during the course of the analysis. DOE identified three key characteristics: output power, output voltage, and production volume. If the test units differed from the representative units by any of these three characteristics, their costs and efficiencies would not be directly applicable to the representative units. For these cases DOE developed a methodology to scale cost and efficiency data for test units to estimate what those values would be, if the test units were to have the characteristics of the representative units. The following section provides additional explanation and examples of how and why these scaling methods were used.

As illustrated in Figure 3.1, DOE calculated ERMC from iSuppli data whenever possible. When iSuppli data was not directly available, DOE estimated the ERMCs of EPSs not directly costed by iSuppli by developing scaling methods. DOE’s scaling methods combined low­volume cost estimates performed by its subject­matter experts (SMEs) with iSuppli’s high­volume cost estimates for other units. Specifically, it developed four methods to determine the high­volume cost of individual components, which were used to construct a high­volume ERMC, which was subsequently scaled to the representative unit volume, power, and voltage, as described in sections 3.3, 3.4, and 3.5.

3­1

### 1 1

- - 

### 1. DOE

selected

units 2. SMEs

measured efficiency 

### 3. SMEs

costed

units 4. iSuppli

costed

units 5. DOE

developed

methods 

### 7. DOEcompiled highvolume costs 6. DOE

scaled

costs

2

3

4

5 2

3

4

5

BOM $

Cap

Res

Xfmr $0.11

$0.03

$0.64 

### BOM $

Low to High

Volume Scaling

Methods 

### 1

5 2

3

4 # % $

75%

46% $1.68

$2.09 2

3 75% $3.59 32%

46% $4.68

$5.21 1

2

3 32%

65%

53% $1.22

$1.03

$1.54 1

4

5.........

Cap

Res

Xfmr $0.02

$0.007

$0.26...... high volume from low to Costs scaled Highvolume costs only

Low- High

volume volume

costs from costs from
public private catalogs database

Figure 3.1 Illustration of DOE Process Used to Compile High­Volume Cost Estimates for the Non­Class A Eps Determination Analysis from Sme and Isuppli Teardowns

3.2.1 Summary of Methods

To develop a high­volume ERMC from a low­volume ERMC provided, DOE analyzed eight high­volume iSuppli cost estimates for units with approximately the same production volume (150,000–225,000 units/year) and therefore had comparable component costs. DOE then used high­volume component costs and their averages, and ratios between the high­volume and low­volume component costs and their averages, to replace or scale the low­volume component costs, arriving at high­volume ERMCs comparable with the other high­volume cost­estimates used in later analysis. The methods that DOE used to perform these transformations are listed

below.

Method 1. Direct Substitution of iSuppli Component Costs: Directly substitute highvolume iSuppli component costs for low­volume component costs when there was an exact match between the two components ( e.g. , certain electrolytic capacitors). See

section 3.2.5.1.

Method 2. Direct Substitution of Category­Average iSuppli Component Costs: Directly substitute the category­average high volume iSuppli component costs across component categories where prices do not vary ( e.g. , surface­mount resistors). See

section 3.2.5.2. 

### 1

2

3

4

5 # % $

32%

75%

46%

65%

53% 1

2

3

4

5 

### 1

2

3

4

5 # % $

1

2

3

4

5...... 

### # % $ # % $

1

2

3

4

5 # % $

1

2

3

4

5 iSuppli

DOE scaling

DOE scaling

iSuppli

iSuppli Source

$1.22

$1.68

$2.09

$1.03

$1.54 32%

75%

46%

65%

53%...

3­2Method 3. Scaling of SME Costs Using SME­iSuppli Component Matches: Multiply the low­volume SME component costs by a category­average scaling ratio between the low­volume SME component costs and the high­volume iSuppli component costs ( e.g. , bipolar­junction transistors). See section 3.2.5.3.

Method 4. Substitute Category­Average iSuppli Component Costs : For the remaining components, for which no low­volume SME component costs were estimated, simply use the average high­volume iSuppli cost estimates for the component category. ( e.g. , some integrated circuits). See section 3.2.5.4

3.2.2 Available Data

3.2.2.1 SME Efficiency Measurements of 5 W EPSs

In 2007, DOE’s SMEs measured the efficiencies of 11 EPSs with nameplate output power at or around 5 W and voltage around 5 V. These were made by different manufacturers and featured disparate designs, resulting in a wide spread of active­mode efficiencies and no­load powers. The measurement results appear in the figure below.

**0 0.2**  **0.4 0.6**  **0.8**

**1 1.2**  **1.4 1.6**  **1.8**

**2**

**0% 10%**  **20% 30%**  **40% 50%**  **60% 70%**  **80%**

Active Mode Efficiency [%]No­LoadPower[W]

**5 W,**  **5 V** 

**5.15 W,**  **5.15 V** 

**5.2 W,**  **5.2 V** 

Figure 3.2 SME Efficiency Measurements of 5 W EPSs

3.2.2.2 SME Teardowns

The SMEs tested 11 EPSs, nine with an output power of 5 W and output voltage of 5 V, one with 5.15 W, 5.15 V, and one with 5.2 W, and 5.2 V. Of these, nine were torn down. The teardowns, whose results are listed in Table 3.1, consisted of opening the EPS housing, counting and identifying the components, and costing them using component catalogs such as Digi­Key a

a “Digi­Key Catalog,” Digi­Key Corporation, www.digikey.com.

3­3and Mouser. b The costs for most components were obtained at low­volume quantities of 1000 units, with the exception of line­frequency transformers, which were costed using a bottom­up approach, taking into account the cost of steel for the laminations ($1.667/lb), and adding in the costs of copper and assembly (assumed to be equal to the steel cost). In cases where the component could not be identified or located in the catalogs, costs for equivalent or similar components were used.

Table 3.1 EPSs Torn Down by SMEs to Develop Low­Volume ERMCs

Unit

# Pout Vout Mfr. Model Active

Mode

Eff. No­Load

Power

[W] LowVolume

ERMC

27 5 5 Globtek 48­5­1000R 49% 1.424 $2.230

17 5 5 Phc PV­51AR 36% 1.852 $2.950

8 5 5 Phihong PSA05R­050­R 73% 0.112 $3.411

22 5 5 Prs HP­5V2 59% 0.421 $3.978

18 5 5 Ericsson PS­513 70% 0.540 $4.011

24 5 5 Phihong PSA05R­050R 72% 0.109 $4.040

21 5.2 5.2 Netbit DSC­51FL­52P US 71% 0.102 $4.670

25 5 5 Phihong PSA05A­050 66% 0.641 $4.712

37 5 5 Phihong PSA05A­050 66% 0.657 $5.020

45 5 5 Reliapro DCU050100 50% 1.400 No

Teardown

10 5.15 5.15 Phihong PSAA05A­050­R 53% 0.108 No

Teardown

The SMEs tore down several BCs in a similar fashion. Because BCs and EPSs share many common components, these BC teardowns were used to develop the four methods for scaling between low­volume and high­volume parts costs, as described in section 3.2.5.3.

3.2.3 DOE Method for Determining ERMC from iSuppli Data

DOE subcontracted iSuppli to tear down and cost 20 EPSs and BCs, of which six were non­Class A EPSs. Specifically, DOE provided iSuppli with 20 units for which iSuppli determined the cost per component at high volume. DOE included in each unit’s ERMC the costs for components directly related to efficiency, but not costs for components secondarily or not related to efficiency. To better explain this approach, DOE provides an example of this approach for some of the components in EPS #106.

Table 3.2 lists five of the components costed by iSuppli for EPS #106; Table 3.3 presents a complete list of components for the EPS. Table 3.4 and Table 3.5 illustrate an example for EPS #106. The ERMC of $1.13 for EPS #106 includes costs for the capacitor ($0.078) and diode ($0.035) in the table. However, costs for the printed circuit board (PCB), enclosure and label are

b “Mouser Electronics Catalog,” Mouser Electronics, Inc., www.mouser.com.

3­4not included. In general, more efficient circuits tend to be smaller and would therefore require smaller, and consequently cheaper, enclosures and PCBs. Therefore, DOE considers the PCB and enclosure as secondarily related to efficiency because their cost can indirectly vary with efficiency. The ERMC does not include the cost for the label because the label has no relation to efficiency.

Table 3.2 Information for Five Components from EPS #106

Component Efficiency Type Component Cost Included in ERMC

Capacitor (Film, 0.1uF) Direct $0.078 Included

Diode (Schottky) Direct $0.035 Included

Printed Circuit Board Secondary $0.094 Not Included

Enclosure (Top) Secondary $0.210 Not Included

Label (White Mylar) Not efficiency related $0.014 Not Included

In addition to materials costs, iSuppli also provided conversion costs for labor, such as for assembly, insertion, and testing. However, DOE did not include labor costs in the ERMCs, but rather accounted for labor costs in the markup from ERMC to EPS manufacturer sales price.

3­5Table 3.3 Information for All Components from EPS #106

­

Component Efficiency Type Quantity Cost Per Component Included in

ERMC Analog Controller Direct 1 $0.1700 Included

Analog Regulator Direct 1 $0.0180 Included
Capacitor (Ceramic) Direct 3 $0.0028 Included

Capacitor (Ceramic, 0.1nF) Direct 1 $0.0160 Included

Capacitor (Electrolytic, 100uF) Direct 1 $0.0170 Included

Capacitor (Electrolytic, 10uF) Direct 1 $0.0520 Included

Capacitor (Electrolytic, 330uF) Direct 1 $0.0170 Included

Capacitor (Electrolytic, 470uF) Direct 1 $0.0300 Included

Capacitor (Electrolytic, 47uF) Direct 1 $0.0100 Included

Capacitor (Film, 0.1uF) Direct 1 $0.0780 Included

Capacitor (Film, 2.2uF) Direct 1 $0.0220 Included

Diode Direct 5 $0.0052 Included

Diode (Fast recovery) Direct 1 $0.0150 Included

Diode (Melf) Direct 2 $0.0090 Included

Diode (Schottky) Direct 1 $0.0350 Included

Inductor Direct 1 $0.0380 Included

Optocoupler Direct 2 $0.0450 Included

Resistor Direct 2 $0.0120 Included

Resistor Direct 3 $0.0009 Included

Resistor Direct 9 $0.0003 Included

Thermistor Direct 1 $0.0350 Included

Transformer Direct 1 $0.2300 Included

Transformer Direct 1 $0.1550 Included

Transistor Direct 1 $0.0200 Included

AC Plug Secondary 1 $0.1800 Not Included

Enclosure (Bottom) Secondary 1 $0.2400 Not Included

Enclosure (Top) Secondary 1 $0.2100 Not Included

Printed Circuit Board Secondary 1 $0.0940 Not Included

Spacer Secondary 1 $0.0550 Not Included

Jack (USB) Not efficiency related 1 $0.0750 Not Included

Label (Aluminized Mylar) Not efficiency related 1 $0.0580 Not Included

Label (White Mylar) Not efficiency related 1 $0.0140 Not Included

Label (White Paper) Not efficiency related 1 $0.0110 Not Included

Jumper Wire Not efficiency related 1 $0.0100 Not Included

3­6- Table 3.4 EPS #106 Production Related Device Information

­

Device Category Cell­Phone Chargers

ID# 106

Reference Information EPS #106 – 2.5W Class A Annual Production Volume (K Units / Year) 1,000 Production Lifespan (Years) 5 Lifetime Production Volume (Units) 5,000,000

Table 3.5 EPS # 106 Summary of Component Costs by Efficiency Relevance

­

EPS # 106 – 2

. 5 W Class A

Cost Type Efficiency Family Type Component Type % of Total

Component Cost
$USD Sum of Total

Component

Cost $USD Sum of Qty

Direct

Material Cost Direct Magnetic (transformer only)

Capacitor
Metal - heatsinks only

Transistor

Resistor

Diode

Fan

Magnetic
Analog

Fuse
Coupler

LED 17.87% $0.39

11.62% $0.25

0.00%
0.93% $0.02

2.99% $0.06

4.36% $0.09

0.00%
1.76% $0.04
8.73% $0.19

0.00%

4.18% $0.09

0.00% 2

11

1

15

9

1

2

2

ERMC Efficiency related
materials cost (Direct Total) 52.45% $1.13 43

Not efficiency related Metals

Switch

Connector

Hardware

Other 0.00%

0.00%

3.95% $0.09

0.00%

3.85% $0.08 2

3
Not efficiency related Total 7.80% $0.17 5
Secondary Plastics & Elastomers

PCB
Connector (Output Cord) 31.80% $0.69

4.36% $0.09

0.00% 4

1

Secondary Total 36.16% $0.78 5

Direct Material Cost Total 96.41% $2.08 53

Conversion

Cost Not efficiency related Assembly

Test

Insertion 0.00% $0.00
2.28% $0.05

1.31% $0.03

Not efficiency related Total 3.59% $0.08

Conversion Cost Total 3.59% $0.08

Grand Total 100.00% $2.15 53

3­73.2.4 Assumptions

3.2.4.1 Production Volume

As described in section 3.2.2.2, the SMEs analyzed the cost of the 5 W EPSs using production volumes of 1,000 units/year. Whereas iSuppli performed their cost estimates using component costs at volumes of 1,000 unit/year to 1,000,000 units/year. To develop high­volume ERMCs for the 5 W EPSs and several non­Class A EPSs, DOE relied on eight iSuppli teardowns developed assuming volumes around 225,000 units/year and listed in Table 3.6.

Because iSuppli estimated the component costs assuming a similar volume, DOE was able to use cost estimate from across these eight teardowns to create its own high­volume

ERMC.

Table 3.6 EPS and BC Units that iSuppli Tore Down and DOE Used in Data Scaling

Unit # Device Class Manufacturer Model Volume [units/year]

EPS #117 Mid­Power EPSs Elpac FW1812­760F 225,000

EPS #118 Mid­Power EPSs Elpac FWC1812­760F­NC 225,000

BC #2 Low­Voltage BCs Norelco 7140XL 150,000

EPS #120 Mid­Power EPSs SL­Power PW118RA1203F01 225,000

BC #28 Low­Voltage BCs Wahl 9953 150,000

BC #5 High­Voltage BCs Makita DC1804 T 150,000

EPS #127 High­Power EPSs SL­Power PW122MA2403F01 225,000

EPS #128 High­Power EPSs XP­Power AML120PS24 225,000

3.2.4.2 Data Included in the Cost­Efficiency Curves

(1) Costs : Besides electronic components, an EPS contains a printed circuit board to which the components are attached and through which they are connected to each other, heat­sinks that dissipate heat generated during power conversion, mounting hardware as well as a plastic housing and output (and potentially input) cords and connectors. Except for heat sinks, which were excluded, the SME cost estimates included all components “directly related” to efficiency. The heat sinks and the remainder of the components, which are secondarily or not at all related to efficiency, were inventoried by iSuppli, but not by the SMEs, and were not included in the efficiency­related BOM cost estimates.

(2) Power Losses : The low output voltage (5 V) of the 5 W EPSs used to estimate the efficiency typical of EPSs for BCs results in significant losses in the output cable, which decrease the active­mode efficiency. Because altering the length and gauge of the output cable is not a design option for increased efficiency (a different output cable may impact utility), the cable losses were not included in the analysis of the 5 W EPSs. DOE seeks comment on how it should treat cable losses and their variability in the future.

3­83.2.5 SME Cost­Scaling Methodology

3.2.5.1 Direct Substitution of iSuppli Component Costs

In cases where there was an exact match between a component in the low­volume SMEBOM and a component in the high­volume iSuppli BOM, DOE directly substituted the highvolume cost estimate. This was performed in the case of generic components such as 1N2007 rectifier diodes and electrolytic capacitors with equal capacitances and voltage ratings.

3.2.5.2 Direct Substitution of Category­Average iSuppli Component Costs

The costs of the components contained in the eight high­volume iSuppli teardowns were categorized by component family, component type, component subtype, and additional qualifications, which included qualities that affect cost such as package form, precision, or voltage, current, and power ratings. At each level of detail, the component costs belonging to the same category—and regardless from which of the eight teardowns the components originated— were grouped together and compared.

For example, the component costs for all the precision resistors in 0603 packages across the eight teardowns were compared to each other. The same was done for the 0805­package precision resistors, and then all (precision and non­precision) 0603­ and 0805­package resistors and then 0603 package capacitors, etc., and then for all capacitors and all resistors, regardless of their package form. Finally, all the component costs in each family ( e.g. , passive, discrete semiconductor, etc.) were also compared. The relationships between the component categories, including some examples, are illustrated in Figure 3.3.

Comp. Family

Comp. Type

Comp. Subtype

Add’l Qualifications All Components

Passive Discrete Semiconductor

Capacitor Resistor Diode Transistor

0603 0 805 Etc.

Etc. IC

Precision Precision Etc. Categories:

Figure 3.3 Categorization of Components Used to Perform Substitution or Scaling

Depending on the spread and number of component cost estimates within each category, a category­average cost was calculated and substituted for all members of that category. For example, 0402­package capacitors are a commodity item the cost of which does not depend strongly on manufacturer, capacitance, or temperature characteristics. Therefore, all 0402 capacitors, regardless of capacitance, had similar costs, so the iSuppli cost estimates could be averaged and the average substituted directly into the 5 W teardown.

3­9The same substitution, however, could not be performed with capacitors in general—the parent category containing 0402 capacitors. In addition to 0402 and other surface­mount capacitors, this category includes many leaded capacitors, the costs of which depend significantly on capacitance, rated voltage, and temperature characteristics. As a result, a comparison of the costs of all capacitors ( i.e. , surface­mount and leaded) showed great variation in the estimated component cost, meaning that an average would not be representative of the category as a whole.

An average may also not be representative if, despite a low variation in the per­category component cost estimates, there is a limited number of estimates to average. Given two estimates that are within 0.5 cents of each other, it is difficult to predict where the third one will fall. A minimum number of cost estimates is therefore necessary to reassure that the variation of this sample of cost estimates is characteristic of the component category, and that an average based on the sample is representative. These two tests—variation and number of cost estimates—are illustrated in Figure 3.4.

Figure 3.4 Tests of Variation and Number of Cost Estimates Necessary for Device Scaling

In the derivation of high­volume 5 W curves for use in the non­Class A determination analysis, the substitution of component­category iSuppli cost estimates into the SME teardowns was performed under the following constraints on the variation and number of cost estimates:

• Variation : The standard deviation of the cost estimates for the component category had to be under $0.01. A variation of $0.01 was assumed insignificant given a total unit cost of greater than $1.00.

• Sample Size : The number of cost estimates for the component category had to be greater than 5. A number of cost estimates greater than 5 was deemed to be representative of the entire component category, and given a sufficiently low variation, usable as a basis for a category­wide average.

3­10• Exceptions : Exceptions were made for standard­sized passive components, such as capacitors and resistors in 0402 and 0603 and resistors in 1/4 W and 1/2 W packages. These were assumed to exhibit sufficiently small variation, even if the number of cost estimates was less than 5, such that the average was always taken and substituted into the SME teardowns for components from these categories.

As a result, the average iSuppli cost estimates for the following categories were substituted directly into the SME 5 W teardowns (the component costs for the remainder of categories had to be estimated using the other methods):

• Discrete Semiconductor, Diode, Rectifier, 1­2A • Passive, Resistor, 0603

• Discrete Semiconductor, Diode,

Zener • Passive, Resistor, 0805

• Discrete Semiconductor, Transistor, BJT, 500­1000 mA • Passive, Resistor, 0805, Precision

• Optical Semiconductor • Passive, Resistor, 1206

• Optical Semiconductor, Coupler • Passive, Resistor, 1210

• Passive, Capacitor, 0402, • Passive, Resistor, 2512

• Passive, Capacitor, 0603, • Passive, Resistor, 1/8 W

• Passive, Capacitor, 0805, • Passive, Resistor, 1/4 W

• Passive, Capacitor, Y1, • Passive, Resistor, 1/2 W

• Passive, Capacitor, Y2 • Passive, Resistor, 1 W

• Passive, Capacitor, Y2, 1­10nF • Passive, Resistor, 2 W

• Passive, Resistor, 0402 • Passive, Resistor, Thermistor

3.2.5.3 Scaling of SME Costs Using SME­iSuppli Component Matches

As can be seen above, the number of component categories that had sufficiently low variation and sufficiently large number of cost estimates was small, limited mostly to standardized surface­mount passives and leaded resistors in 1/8 W through 2 W packages. c In the other component categories, however, there was more variation in the characteristics of the components and therefore more variation in their cost. Rather than substitute category­average

c The package size of resistors determines their power rating.

3­11component costs directly into the 5 W SME teardowns, the SME cost estimates were scaled by a category­specific ratio.

Of the eight units torn down by iSuppli (shown in Table 3.6) three were also torn down by the SMEs: BCs #2, #5, and #28. These were used to calculate the scaling ratios by matching the low­volume SME cost estimate for each component with the high­volume iSuppli cost estimate. The iSuppli component cost was then divided by the SME component cost, resulting in a scaling ratio between the two, as shown in Table 3.7.

Table 3.7 Example Matches Between SME and iSuppli Component Cost Estimates Used to Develop Category­Specific Scaling Ratios

SME iSuppli iSuppli

SME Comp iSuppli Comp. iSuppli Comp. ScaComp. SME Comp. . Cost Comp. Descrip Comp. Cost Comp. Add’l ling Type Description [$] Type tion Pkg. [$] Subtype Qual. Ratio

Choke Axial lead

choke 3.9mH

TDK in

Mouser 0.350 Magnetic Inductor

­ Wound

Ferrite

Core SMD 0.0340 Wound

Ferrite 0.10

Choke Ferrite bead

wound as

small

common mode choke 0.100 Magnetic Ferrite

Bead 0805 0.0025 Ferrite

Bead 0.03

Axial ­

Resistor 1/4W 0.012 Resistor Carbon 1/4 W 0.0044 1/4 W 0.37

Film

Capacitor 1500pF

ceramic 0.025 Capacitor Ceramic

Disc ­ Radial, Dipped,

1.5nF Thru

Hole 0.0125 Ceramic 1­10

nF 0.50

Transistor SOT­23 0.030 Transistor Bipolar
­ NPN,

50V,

100mA SOT34

6 0.0080 BJT 100­

200

mA 0.27

To illustrate, suppose that two of the units torn down by the SMEs featured transistors in the same package—TO­220. Unlike 0402 capacitors, which vary only in capacitance, TO­220 transistors look similar but may vary in many substantive ways ( e.g. , device type, voltage and current ratings, on resistance, frequency response, etc.) that will significantly affect their cost. Therefore, it would not be appropriate to find the iSuppli costs of all TO­220 transistors, take the average, and substitute that for the cost of each TO­220 transistor that appears in the SME teardowns. Rather, a scaling ratio must be calculated that reflects the volume discounting typical for that component category and subsequently multiplied by the low­volume SME component costs to calculate high­volume component costs.

3­12Once the match between the low­volume SME and high­volume iSuppli cost estimates for the same component was made, and a ratio calculated, the ratios were then grouped according to the categories in Figure 3.3. Components were first grouped by package form, then by component type, and finally by component family; average scaling ratios were calculated for each of the categories.

Scaling ratios had to be developed for each category level due to the limited number of component matches, d a scaling ratio could not be calculated for all components. Using Table 3.7 as an example, a scaling ratio was calculated for 3.9 mH chokes, but it may not be applicable when scaling a 39 mH choke. It was necessary, therefore, to calculate a scaling ratio for all magnetics and passives. The appropriate (as explained below) category­specific ratio was then used to scale the low­volume cost estimates of components for which substitution was not possible and to obtain a high­volume cost estimate.

Scaling ratios varied within and between component categories, with greatest variation between the ratios for components in the integrated circuit component family (4 matches, average scaling ratio of 0.41, standard deviation of 0.40) and least variation between the components in the optical semiconductor component family (2 matches, average scaling ratio of 0.233, standard deviation of 0.01). Furthermore, each category level ( e.g. , component type, package form, etc.) had its own scaling ratio that differed from the scaling ratio of the broader categories above it. For instance:

• The 2–5 A rated rectifier diode fully qualified component category had an average scaling ratio of 0.09;

• The rectifier diode component subtype (which includes rectifiers of all current ratings) had an average scaling ratio of 0.21;

• The diode component type (which includes rectifiers as well as switching and Zener diodes) had an average scaling ratio of 0.26; and

• The discrete semiconductor component family (which includes diodes as well as transistors and thyristors) had an average scaling ratio of 0.36.

In this example, the choice of scaling ratio could change the high­volume cost by a factor of four. DOE considered several approaches to choose the ratio.

In one approach, DOE could simply take the ratio for the narrowest category that includes the component undergoing cost scaling. Under this scheme, the low­volume SME cost of a 2–5 A rated rectifier diode would be multiplied by 0.09 to arrive at a high­volume cost. Similarly the cost of a generic rectifier diode with an unknown current rating would be multiplied by 0.21, the cost of a diode with an unknown function ( e.g. , rectification, switching, etc.) would be multiplied by 0.26, while the cost of a thyristor—a semiconductor component

d Again, only three BCs had undergone both SME and iSuppli teardowns, resulting in only 66 component matches that could be used to calculate scaling ratios.

3­13used for power switching—would be multiplied by 0.36, the average discrete­semiconductorfamily scaling ratio.

The narrower the component category, however, the fewer matches there are between SME and iSuppli cost estimates from which to calculate an average scaling ratio. Because DOE performed matching on a limited set of teardowns ( i.e. , the three BC units), some categories had no matches, while many more had only one match. As with the price substitutions, an averageratio based on only a few matches may not be representative of the relationship between lowvolume and high­volume costs for all components within that category.

Therefore, when DOE selected which scaling ratio to use for a particular category, the standard deviation of the scaling ratios for matches within that category and its broader parent categories (if any) were compared, and the average scaling ratio of the category with the lowest

standard deviation was used.

Using the above example, there was only one match between SME and iSuppli cost estimates for 2–5 A rectifier diodes, so no standard deviation could be calculated. Therefore, the scaling ratio for the parent category ( i.e. , rectifier diodes, which had five matches) was used, and the SME cost estimates for 2–5 A rated rectifier diodes were multiplied by 0.21 (the general rectifier diode scaling ratio) to arrive at a high­volume cost estimate. Thus, even though the broader parent category includes a greater diversity of components, the larger number of components it contains may lead to a lower variation in the scaling ratio, as reflected in the

standard deviation.

3.2.5.4 Substitute Category­Average iSuppli Component Costs

Finally, in several of the EPSs torn down by the SMEs, DOE was unable to estimate some of the low­volume costs for a few components. Although most components are either identified with specific part numbers or other markings ( e.g. , transistors) or are generic enough that such markings are unnecessary when estimating cost ( e.g. , surface­mount capacitors), some components fall into neither of these groups.

In particular, some integrated circuits are custom­made for a specific application so their part number cannot be found in a component catalog, making identification and pricing intractable. Alternatively, some diodes and many surface­mount discrete semiconductors may lack part numbers entirely, displaying instead a short manufacturing code that may distinguish the component from others made by the same manufacturer. However, such codes also do not appear in component catalogs.

Nonetheless, it is possible to determine the component’s location and function in the circuit. Based on this information, DOE was able to categorize the component by type ( e.g. , transistor) and occasionally even by subtype ( e.g. , field­effect transistor). Subsequently, DOE proceeded to substitute the category­average iSuppli component cost, as described in section

3.2.5.2. However, unlike in the original application of that method, the variability and number of samples upon which the averages were based were not considered, as this was the only method remaining for estimating the high­volume cost of these components.

3­143.2.6 Summary

For the units that iSuppli tore down, DOE used iSuppli data exclusively. In cases where DOE not could obtain high­volume iSuppli cost estimates to support its non­Class A EPS engineering analysis, it relied on teardowns and low­volume cost estimates performed by its SMEs. As described above, the high­volume iSuppli component costs were then either directly substituted for the low­volume estimates obtained by the SMEs, or used to scale the SME estimates. The component costs thus adjusted were then compiled into a high­volume ERMC for the unit, for use in subsequent analysis.

3.3 Scaling EPS Efficiency with Output Power

The practically achievable efficiency of an EPS depends on its nameplate output power: lower­power EPSs tend to exhibit lower active­mode efficiencies than similar units with higher output powers. (Changes in output power do not impact the no­load power consumption.) However, some of the EPSs that DOE analyzed for the non­Class A engineering analysis differ in output power from the representative units for their product class. DOE therefore developed a model for estimating the change in active mode efficiency when the output power of an EPS is shifted to that of the representative unit.

Figure 3.5 is a schematic representation of the EPS efficiency distribution with power, which shows the relationship between the two. Based on this distribution, DOE concluded that if a manufacturer were to design two similar EPSs with slightly different powers, the efficiency of the higher­power EPS would be higher, and vice versa. However, there is a wider range of efficiency at low output power than at high output power. Any shift of a manufacturer’s unit to the representative unit output power should therefore take into account both effects, preserving a unit’s relative standing in terms of efficiency among other units in the market.

3­15**Efficiency [%]**  **ENERGY STAR**  **demarcates the**  **75 th** 
**percentile of**  **efficiency.**



### Rated **Output Power**  **[W]**

Figure 3.5 Schematic Illustration of the Distribution of Efficiency Versus Maximum Rated Output Power; the ENERGY STAR Level Is Shown as a Pink Line, while the Blue Background Indicates Where Most of the Units Lie

A unit’s relative standing could be calculated by comparing its efficiency to the level specified in the ENERGY STAR EPS Eligibility Criteria Version 1.1 (2005) e as well as the bestin­market level, defined as the curve­fit of the highest­efficiency units in the ENERGY STAR qualifying products database. Because of the fundamental similarities in the design of Class A and non­Class A EPSs, DOE extended these same relationships and datasets to model the impacts on non­Class A EPS efficiency.

To preserve the relative standing of the manufacturer’s unit in the market, while shifting the results to the representative unit output power, DOE maintained the ratios among the unit’s efficiency, the ENERGY STAR level, and the best­in­market level. Figure 3.6 illustrates this process, while Figure 3.7 shows how DOE generated the best­in­market curve­fit using theENERGY STAR qualifying products database. Since no correlation has been found between noload power and output power, DOE did not scale the no­load power.

e EPA, “ENERGY STAR Program Requirements for Single Voltage External Ac­Dc and Ac­Ac Power Supplies: Eligibility Criteria,” Ver. 1.1, 2005. http://www.energystar.gov/ia/partners/product_specs/program_reqs/archive/EPS_Eligibility_Criteria_V1.1.pdf

3­16

### Shift

η **BEST_IN_MARKET Efficiency** **[%]**



### P **MFR_UNIT** 

### P **REP_UNIT** 

### η′ **MFR_UNIT** 

### η **ENERGY_STAR**



### η **MFR_UNIT**



### Rated **Output Power**  **[W]**

Figure 3.6 Schematic Illustration of Scaling EPS Efficiency with Output Power

**0% 10%**  **20% 30%**  **40% 50%**  **60% 70%**  **80% 90%**  **100%**

**0 50**  **100 150**  **200 250** 

Rated Output Power [W]ConversionEfficiency

**Highest performing**  **units**

**ENERGY STAR**  **v. 1.1**  **level**

**Best­in­market level** 

**Worst­in­market level** 

Figure 3.7 ENERGY STAR Level and Calculated Best­in­Market and Worst­in­Market

Curves

3­17DOE performed the shift in efficiency relative to the best­in­market and ENERGY STAR levels using the following equations:

η ′

= η ′

− r ⋅ 

# ( η ′

− η ′ MFR

_ UNIT BEST

_ IN

_ MARKET BEST

_ IN

_ MARKET ENERGY

_ STAR 

# )

Eq. 3.1

and

η

− η BEST

_ IN

_ MARKET MFR

_ UNIT r = , η

− η

BEST

_ IN

_ MARKET ENERGY

_ STAR

Eq. 3.2

where:

η , η , and η are the efficiencies of the unit under analysis,

MFR

_ UNIT BEST

_ IN

_ MARKET ENERGY

_ STAR the best­in­market point, and the ENERGY STAR level, respectively, at the manufacturer­provided nameplate output power, while

the primed terms refer to the same quantities at the nameplate output power of the representative unit, to which the unit efficiency is being scaled, and

r is a scaling ratio that represents the position of the efficiency of the manufacturer­provided unit

to that of other EPSs in the market.

3.4 Scaling EPS Efficiency with Output Voltage

3.4.1 Summary and Introduction

Together with the nameplate output power, the nameplate output voltage constrains a power supply’s achievable efficiency. Given two EPSs with an identical design but different output voltages, the lower­voltage unit will be less efficient, primarily due to:

• Resistive losses: outputting the same power at a lower voltage requires higher output current, increasing the resistive losses, which are proportional to the square of the current; and

• Rectifier losses: the voltage drop across the output rectifier increases with higher current, such that at a lower voltage more power (current times the voltage drop across the rectifier) will be dissipated, decreasing the efficiency of the power supply.

In addition to the above losses, the EPS also experiences fixed losses that do not depend on the output voltage. These losses are associated with, for example, the quiescent current of the controller IC for switched­mode designs or the core magnetization losses for line­frequency designs and are equal to the no­load power consumption of the power supply. The schematic in Figure 3.8 summarizes the loss mechanisms described above.

3­18

### I Q 

### R OUTPUT 

### R CORD



### +

− +

- V OUT 

### V S



### - V DIODE 

### +

Figure 3.8 Schematic of EPS Loss Model Used for Scaling Efficiency with Voltage

When scaling the efficiency of a power supply with voltage, DOE first calculated the typical losses according to the model presented in Figure 3.8. Because the characteristics of each of the components in the loss model were fixed, the losses calculated using the model depended only on the output current and voltage, not the design specifics of the EPS. In short the model returned the same losses for any two EPSs with the same output characteristics, regardless of their designs.

However, because each EPS has its own specific design, the actual losses of the power supply differ from those calculated according to this generic model. This difference between the modeled and actual losses does not depend on the output power or voltage, but is correlated instead with the active mode efficiency and no­load power of the EPS. Thus the actual losses of an EPS can be said to be the sum of two components: (1) generic losses, dependent on output power and voltage and modeled as described above; and (2) additional losses, dependent on the design of the EPS. Because the additional losses reflect the design of the EPS, and the purpose of scaling was to estimate the losses of a particular design at the representative­unit output power and voltage, the additional losses were held constant between the original EPS and the representative unit to which it was being scaled.

Having obtained the generic losses for the original EPS using the model and its technology­dependent additional losses, the generic losses for the representative unit were calculated. These were then added to the technology­dependent additional losses, resulting in an estimate of the total losses of the EPS design at the representative­unit output power and voltage. The representative unit’s efficiency was finally calculated as the ratio of output power and the sum of the output power and the losses thus estimated.

3.4.2 Experimental Basis

As can be seen in Figure 3.9, there is a direct relationship between the nameplate output voltage and average active mode efficiency for EPS units within the same design family (group of EPSs that share a common output power and fundamental design, but vary in output voltage). Because of this relationship, it is possible to estimate the efficiency of one EPS unit given the voltage of the unit as well as the voltage and efficiency of another unit in the same EPS design family. Similarly, given the output voltage and efficiency of an EPS it is possible to estimate the efficiency at the output power and voltage of the representative unit.

3­19**0% 1%**  **2% 3%**  **4%**

**10 12**  **14 16**  **18 20**  **22 24** 

Nameplate Output Voltage [V]DifferenceinActiveModeEfficiencyRelativeto12VUnit **75 W**  **EPS Family** 

**60 W**  **EPS Family**  **1**

**60 W**  **EPS Family**  **2**

**60 W**  **EPS Family**  **3**

**60 W**  **EPS Family**  **4**

Figure 3.9 Difference in Active Mode Efficiency vs. Nameplate Output Voltage

The relationship displayed in Figure 3.9 is representative of higher­power, higher­voltage EPSs. However, the analysis of EPSs for BCs for the non­Class A determination required the aggregation of efficiency at the 1.8 W, 6 V and 4.8 W, 24 V representative unit powers and voltages for accurate comparison. Because the experimental data in Figure 3.9 does not extend to the output powers and voltages of these representative units, a different model was developed based on the losses inherent in the components of the EPS.

There was no correlation between nameplate output voltage and no­load power consumption.

3.4.3 Loss Calculations

To scale the efficiency of a given EPS to the representative­unit output power and voltage, the losses in the EPS must first be modeled. These are assumed to conform to the simplified model below, which takes into account the quiescent losses, which are independent of the output voltage, as well as losses in the output cord, rectifier diode, and the output resistance of the EPS. This loss model is illustrated in Figure 3.8. The losses in each component are summarized in Table 3.8 Losses for Scaling Model for Efficiency with Output Voltage.

Table 3.8 Losses for Scaling Model for Efficiency with Output Voltage

Loss Type Power Loss Equation Explanation Quiescent

Loss LOADNO LOSS PP

− = Where:

LOSS P is the power lost in the

3­20modeled component; and

LOADNO P

− is the no­load power

consumption of the EPS.

Rectifier LOSS P

⋅ = DIODE LOAD VI Where:

Diode Loss      

+ ⋅= 1 ln

S LOAD TLOAD I I VI LOAD I is the load current;

T V is the thermal voltage equal to

0.026 V; and

S I is the saturation current equal to

1x10 ­12

. Cord

Resistance

Loss LOSS P CORD LOAD RI ⋅= 2 Where:

LOAD I is the load current; and

CORD R is the cord resistance.

Output

LOSS P ⋅= OUTPUT LOAD RI 2 Where:

Resistance

Loss       Δ

⋅=
MAX OUT LOAD I V I 2 2 LOAD I is the load current;

OUTPUT R is the output or source

resistance;

OUT Δ V is the voltage regulation (e.g.,

5% of the nameplate voltage); and

MAX I is the nameplate output current.

After the above component losses are calculated for an EPS at its original output power and voltage and at each loading condition, they are subtracted from the total unit power loss at each of the active mode loading conditions (25%, 50%, 75%, and 100% of nameplate output current) resulting in an additional loss term. This additional loss is related to the specifics of the EPS design; for example an EPS that uses a Schottky rectifier diode will have a lower diode voltage drop, resulting in lower rectification losses, and possibly a negative additional loss term. The relationship between the unit efficiency at a given loading condition and the component and additional losses is reflected in the equation below.

P P P

OUT OUT OUT Eff = = = , P P + P P + P + P

IN OUT LOSS OUT LOSS

_ COMP LOSS

_ ADD ' L

Where:

Eff is the efficiency at a given loading condition;

P OUT is the output power at the loading condition;

P

IN is the input power at the loading condition;

3­21P LOSS_COMP is the power lost by the unit modeled by the component losses at the loading condition; and

P

LOSS_ADD’L is the power lost by the unit not modeled by the component losses at the loading

condition.

Because the additional losses are technology dependent and do not show any correlation when plotted against output power or voltage, they are assumed to remain constant for EPSs in the same design family. This is not the case for the modeled component losses, which are dependent on the EPS output power and voltage and must be recalculated for each unit. The efficiency of the EPS scaled to representative unit power and voltage was therefore calculated as

follows:

P ′ Eff ′

= OUT P ′ + P ′ + P

OUT LOSS

_ MODELED LOSS

_ ADD ' L

Where:

The primed quantities are calculated at the representative unit output power and voltage.

The efficiencies thus calculated at each of the four active mode loading conditions are then averaged to obtain the representative­unit average active mode efficiency. The no­load power consumption does not depend on voltage, so it is assumed to remain constant when scaling to the representative unit.

3.4.4 Conclusion and Examples

The above model was used to develop the engineering curves for the EPSs for BCs analysis, which focused on two representative units with output power and voltage of 1.8 W, 6 V and 4.8 W, 24 V. Efficiency data on several low­power EPSs were first scaled to the representative­unit output power using their relative standing in the market. The above model was then used to adjust the efficiency to the representative­unit output voltage. The results returned by the model are illustrated in Figure 3.10.

3­22**30% 35%**  **40% 45%**  **50% 55%**  **60% 65%**  **70% 75%**  **80%**

**4.8 5**  **5.2 5.4**  **5.6 5.8**  **6 6.2** 

Nam eplate Output VoltageAverageActive­ModeEffiiciency

Figure 3.10 Efficiencies of 5W, 5V EPS Test Units After Scaling to the 1.8 W, 6 V

­

**30% 40%**  **50% 60%**  **70% 80%**  **90% 100%** 

**0 5**  **10 15**  **20 25**  **30**

Nam eplate Output VoltageAverageActive­ModeEffiiciency Representative Unit Level

­

Figure 3.11 Efficiencies of 5W, 5V EPS Test Units After Scaling to the 4.8 W, 24 V

­ Representative Unit Level.

­

3­233.5 Cost Scaling by Nameplate Output Power and Sales Volume

3.5.1 Introduction

A wide variety of Non­Class A EPSs exists on the market in the product classes analyzed by DOE for the NCA EPS determination. Because analyzing every available EPS in each product class was not feasible, DOE chose one EPS in each product class as a representative unit of analysis in order to develop relationships between cost and efficiency. To supplement the cost­efficiency analysis, DOE also tore down a selection of other available EPSs in each product class to obtain data on efficiency, no­load power consumption, output power, ERMCs, and production volumes.

DOE research suggests that for a given EPS design, the ERMC is dependent the output power of the EPS as well as its production volume. In order to compare costs and efficiencies of various EPSs and develop cost­efficiency curves, DOE had to account for variations in output power and production volume across the EPSs analyzed. DOE did this using a scaling model that estimated what the ERMC of a torn­down EPSs would be at the production volume and output power of the representative unit. The development of this model is described in the sections that

follow.

3.5.2 Observed Relationships in Available Data

DOE used two datasets to develop the scaling model. The two datasets allowed DOE to assess relationships between materials cost, production volume, and output power.

The first dataset was a confidential submission of EPS production cost data to DOE. This dataset contained production costs for EPSs with various output powers (including 5 W) at low volumes. DOE observed a linear statistical relationship (with R 2 values of approximately 0.94) between manufacturer selling price and output power for EPSs in the dataset.

The second dataset was a public submission of manufacturer selling price (MSP) to the California Energy Commission (CEC) in support of CEC’s 2006 appliance standards rulemaking. f This dataset contained MSP versus production volume data for 2 W and 5 W EPSs at high volumes. The relationship between MSP (and, hence ERMC) and production volume appeared to be nonlinear, as shown in Figure 3.12 (where production volume is plotted on a logarithmic scale).

Based on the observed linear relationship between EPS output power and EPS production cost in the confidential dataset, DOE assumed that the relationship between EPS output power and MSP in the public dataset would also be linear. Linear trendlines and associated equations for the dataset are shown in Figure 3.13 for three different production volumes.

f Available at: http://www.energy.ca.gov/appliances/archive/2006rulemaking2/documents/comments/NRDC.PDF

. Last accessed March 2, 2009.

3­24**$0.00 $0.50**  **$1.00 $1.50**  **$2.00 $2.50**  **$3.00 $3.50**  **$4.00 $4.50**  **$5.00**MSP[$] **50,000**

**100,000**

**10,000,000 $2.50** 

**$2.00**

**$1.50**

**$1.00**MSP[$]

**2 W**
**$0.50 5 W** 

**$0.00**

**10,000 100,000**  **1,000,000 10,000,000**  **100,000,000**

Shipment Volume (log scale)

Figure 3.12 Manufacturer Selling Price Versus Volume For Specific 2W and 5W EPSs

­

**0 5**  **10 15**  **20 25** 

Output Power [W]

Figure 3.13 Manufacturer Selling Price Versus Output Power for Specific 2 W And 5 W

EPSs at Different Production Volumes

3­25**$0 $5**  **$10 $15**  **$20 $25** Per­UnitProductionCost[$] **Incremental Cost** 

**Total Cost**  3.5.3 Model Development

As mentioned above, there appears to be a nonlinear relationship between MSP and

volume for EPSs. g DOE modeled this relationship as a sum of incremental and fixed costs, as illustrated in Figure 3.14. The per­unit incremental costs account for the component, labor, and other variables costs necessary to manufacture an EPS and do not vary with the number of EPSs

manufactured. h The fixed costs, on the other hand, account for the capital and other one­time costs of manufacture, which are amortized across the number of units.

Under this model, at single unit volume, the total cost of the unit would equal the cost of setting up the assembly line plus the incremental costs for the components, etc. On the other hand, at infinite volume, the fixed cost of setting up the assembly line would be distributedacross the infinite number of units so the per­unit fixed costs would approach zero. The total perunit costs would therefore only equal the incremental costs.

**1,000 10,000**  **100,000 1,000,000** 

Volume ['000s] (Log Scale)

Figure 3.14 Example EPS materials Cost Modeled as a Sum of Fixed and Incremental

Costs.

Because the per­unit fixed costs approach zero at infinite volume and approach infinity at

1 zero volume, DOE modeled them as proportional to

x , where V is the volume and x , the V exponent, is a positive number. The per­unit total cost, which also includes a variable cost, can

therefore be modeled as:

g Because MSP is directly derived from the ERMC through markups, this discussion will focus on the latter term for consistency with the remainder of the engineering analysis.

h A manufacturer may pay different prices for components purchased at different volumes, but DOE assumes that because the similarity in EPS designs, an EPS manufacturer purchases components at a volume much larger than that of an individual design and reuses the same components across several designs—e.g., a change in volume from 10,000 to 100,000 will not have much of an effect if a manufacturer has purchased components in volumes of 10

million.

3­26**Power (2 W)** ERMC = aV

− b + c Eq. 3.6

Where:

ERMC = EPS efficiency­related materials cost;

­

a = Linear scaling term;

­ b = Positive exponent;

­

c = Offset term representative of the variable cost; and

­ V = EPS production volume.

­

To find the parameters a , b , and c , in the above model for the publicly available 5 W manufacturer data, DOE first chose a trial value for c , subtracted if from the ERMC, and performed a regression on

ERMC

− c = ERMC ′

= aV

− b Eq. 3.7

DOE subsequently repeated the regression for different values of the variable­cost offset,

c , to maximize the R 2 value of the resulting curve fit. Once the resultant variable cost, c , was subtracted, the materials cost was equal to a power function of the volume with parameters a and

b

. An illustration of this curve­fit can be seen in, with the values for a and b listed directly on the figure.MSP­ Offset[$] **$0.70**

**$0.60**

**$0.50**

**$0.40**

**$0.30**

**$0.20**

**$0.10**

**$0.00 2**  **W 5**  **W**

**= 138.**  **85x ­0.4985**  **y**

**R 2**  **= 0.9997** 

**y =**  **135.9x ­0.522**  **4**

**R 2**  **= 1** 

**10,000 100,000**  **1,000,000 10,000,000**  **100,000,000**
Shipment Volume (log scale)

Figure 3.15 Offset Efficiency­Related Materials Cost Versus Volume for Specific 2W and

5W EPSs

As could be seen in Figure 3.15, it was possible to determine the model for either a 2 W or 5 W EPS based on the data provided. Going forward, however, DOE used the 5 W model

3­27exclusively because of the second, confidential dataset, which included MSP data at low volumes for a 5 W EPS. By combining these two datasets, DOE was able to increase the robustness of the scaling model at low production volumes.

Figure 3.16 shows the ERMC versus output power for the publicly available 2 W and 5 W data. As before, the 2 W and 5 W points at constant volume are connected with linear trendlines. Note that the 2 W/5 W trendlines intersect, roughly at the same point, forming a family of curves that describe the cost of a particular design as one adjusts output power and production volume.

**­$1.00 $0.00**  **$1.00 $2.00**  **$3.00 $4.00**  **$5.00**

**­15 ­5**  **5 15**  **25**MSP[$] **50,000**

**100,000**
**10,000,000**

Output Power [W]

Figure 3.16 Extended Trendlines Based on Publicly Available EPS Data

Figure 3.17 adds the trendline for the confidential dataset to the extended trendlines in Figure 3.16. The exact volume at which the prices are displayed has been withheld to protect proprietary manufacturer information. It is clear, however, that the volumes must be much lower than those previously displayed.

Despite this stark difference in volume and manufacturer, i this new trendline intersects the earlier trendlines near where they intersect each other. Even though the intersections are imperfect, DOE nonetheless was able to incorporate this trendline into its family of curves by taking the x­ and y­ coordinates of the average intersection point, and setting this average as the common intersection point for the entire family of curves.

i Even though a different manufacturer provided the information underlying this trendline, all data pertains to similar designs able to meet the same efficiency levels.

3­28MSP[$] **$12.00**

**$10.00**

**$8.00**

**$6.00**

**$4.00**

**$2.00**

**$0.00**

**25**

**­$2.00 50,000** 

**100,000**

**10,000,000 Confid**  **ential D**  **ataset**

**­1 5**  **­10 ­5**  **0 5**  **1 0**  **1 5**  **2 0** 

Output Power [W]

Figure 3.17 Extended trendlines with confidential dataset trendline added.

The resultant family of curves models the dependence of ERMC on output power and production volume, taking into account the data of two manufacturers spanning several decades of shipment volumes. This family of curves is described by Eq. 3.8, which captures the linear dependence on output power as well as the nonlinear dependence on volume. The calculated values for all the parameters are summarized in Table 3.9.

aV

− b + c

− Y ERMC = 

## ( P

− X 

## ) + Y Eq. 3.8 P

5 W − X

Where:

ERMC = EPS efficiency­related materials cost;

a = Linear scaling term;

b = Positive exponent;

c = Offset term representative of the variable cost;

V = EPS production volume;

P = EPS output power;

P 5W = Output power of 5 W EPS;

X = X coordinate (power) of average trendline intersection point; and

Y = Y coordinate (cost) of average trendline intersection point.

3­29Table 3.9 Value of Calculated Model Parameters

­

Parameter Calculated Value

a **128.64**

b **0.49**

c **$1.45**

P 5W 5 W

X **­5.7 W** 

Y **$0.47**

The parameters are assumed fixed; thus, the relationship and its associated parameters is assumed reasonable enough to allow scaling across the range of production volumes and output powers of the torn­down EPSs and representative units.

3.5.4 Model Deployment

With this relationship in hand, DOE was able to estimate changes to ERMC that would result from changes to the unit output power and/or production volume. Given a known ERMC, output power, and production volume of a torn­down EPS, together with a known representativeunit output power and production volume, DOE used Eq. 3.9 to estimate the ERMC that the torndown EPS would have at the representative unit output power and production volume.

− b   c

−



## ( 

# ( ) + aV� Y R

− +             X� Y P

R

− P

5 X W ERMC� ERMC Eq. 3.9

­ = Scaled T

− b c

− + aV� Y 

## ) T
P

5 − + P

T X� Y�

− X W

Where:

­ ERMC Scaled = Torn­down EPS efficiency­only materials cost at representative output power and production volume

ERMC T = Torn­down EPS original efficiency­only materials cost;

a = Linear scaling term;

b = Positive exponent;

c = Offset term representative of the variable cost;

V = EPS production volume;

P

R = Representative unit output power;

P T = Torn­down EPS output power;

P 5W = Output power of 5 W EPS;

X = X coordinate (power) of average trendline intersection point; and

Y = Y coordinate (cost) of average trendline intersection point.

3­303.6 Representative Product Classes and Representative Units

3.6.1.1 Representative Product Classes and Units for Multiple­Voltage EPSs

DOE proposed two product classes for multiple­voltage EPSs. Because those product classes are sufficiently different from each other, DOE used both as representative product classes (Table 3.10).

Table 3.10 Representative Product Classes for Multiple­Voltage EPSs

Nameplate Output Power

< 100 watts ≥100 watts

Product Class Multiple­Voltage Product Class 1 Multiple­Voltage Product Class 2

DOE chose one representative unit for each representative product class based on amarket survey it conducted that identified popular nameplate output powers among multiplevoltage EPSs (Figure 3.18). The survey counted the number of products available in online distributor catalogs, including Mouser.com and Jameco.com, which sell multiple­voltage EPSs independent of an end­use consumer product. The survey also included websites, such as Amazon.com and RadioShack.com, that offer replacement EPSs for existing products. Typically, multiple­voltage EPSs are sold packaged with end­use products; however, DOE evaluated individual multiple­voltage EPSs because it could not obtain detailed data for EPSs sold with end­use products. In total, the survey counted 129 unique multiple­voltage EPSs. Most of the multiple­voltage EPSs in the survey had nameplate output power below 70 watts, with popular ratings at 10 watts, 20 watts, and 40 watts. In addition, there were three EPSs with nameplate output power at 203 watts for use with a video game console.

3­31**0 5**  **10 15**  **20 25** ProductCount[#]

**0 5**  **10 15**  **20 25**  **30 35**  **40 45**  **50 55**  **60 65**  **70**

**. . . 203** 

Nameplate Output Power [W]

Figure 3.18 Product Count for Multiple­Voltage EPSs

Based on the market survey, DOE decided to have two representative units with nameplate output power at 40 watts and 203 watts. Originally, DOE considered using nameplate output voltages at 5 V and 12 V for the 40­watt representative unit because that was the most popular voltage combination in the survey. However, during manufacturer interviews it became clear that 40­watt EPSs with that output voltage combination were legacy products in a very small and shrinking market. Because of that, DOE selected the output voltages for the 40­watt unit to be 16 V and 32 V, which are a popular voltage combination for EPSs used in printing applications.

Printing and video game applications are by far the most popular uses for multiplevoltage EPSs. The 203­watt representative unit corresponds to the EPS used with the Microsoft Xbox 360, currently the only video game console to use a multiple­voltage EPS. Therefore, the unit’s combination of output voltages corresponded to that of the Xbox 360: 5 volts and 12 volts. In researching the market, DOE noted that there is a trend for EPSs for video game consoles to use EPSs with lower output powers. Specifically, the Xbox 360 originally used a 203­watt EPS, but uses a 175­watt EPS currently. This occurs because the video game console requires less power, in part due to improvements in its components. In the future, the video game console will probably use an EPS with even lower output power. Nonetheless, DOE analyzed a 203­watt EPS because it is the most established EPS, having multiple manufacturers. DOE believes that it canscale results for the 203­watt EPS to lower power EPSs in future analyses. A full list of multiplevoltage EPS design parameters that DOE fixed for isolating the impacts of efficiency is presented in Table 3.11.

3­32Table 3.11 Characteristics of the Multiple­Voltage EPS Representative Units

­

Parameter Values for 40 W EPS Values for 203 W EPS

Output Voltages and Currents V 1 = 16 V, I 1 = 0.625 A,

V

2 = 32 V, I 2 = 0.940 A V 1 = 5 V, I 1 = 1 A,

V

2 = 12 V, I 2 = 16.5 A

Input Voltage 115 volts rms, 60 Hz 115 volts rms, 60 Hz

Input Protection Primary current fuse, inrush current limiting Primary current fuse, inrush current limiting Output Voltage Regulation ± 5% (excluding cord) ± 1% (excluding cord)

Output Voltage Ripple 2% V P­P maximum 1% V P­P maximum

Transient Response 0.5 ms for 50% load change typical 0.5 ms for 50% load change typical

Output Protection Overcurrent protection, short­circuit protection Overcurrent protection, short­circuit protection

Unit Volume 1M units per year 4M units per year

Application Multi­Function Device Video Game System

Package Sealed polycarbonate Sealed polycarbonate

Output Cord Length 6 feet 6 feet

Regulatory Compliance UL, FCC UL, FCC

Product Lifetime 5 years 5 years

3.6.1.2 Representative Product Classes and Units for High­Power EPSs

DOE proposed one product class for high­power EPSs which it used as a representative product class (Table 3.12). Since ham radios are essentially the only end­use consumer application for high­power EPSs, the nameplate output voltage of the representative unit was

13.8 volts corresponding to the standard ham radio operating voltage.

Table 3.12 Representative Product Classes for High­Power EPSs

Nameplate Output Power

> 250 watts

Product Class High­Power Product Class 1

DOE chose one representative unit within the representative product class based on a market survey it conducted that identified popular nameplate output powers among high­power EPSs (Figure 3.19). The survey counted the number of products available in online distributor catalogs that sell high­power EPSs for use with ham radios, including UniversalRadio.com and

AESham.com . Typically, high­power EPSs are purchased through these types of ham radio part distributors separately from other ham radio products; therefore this data gathering method

3­33reflects the high­power EPS market. However, there was a limited amount of EPSs availablebecause ham radios are a niche application. Nonetheless, the survey counted 37 unique highpower EPSs. Among those units there was a range of nameplate output power from 276 watts to 786 watts. DOE selected 345 watts because it was the most popular (9 units available) and is in the middle of the output power range for all units. Because the output power is in the middle of the range, DOE believes that it will be easier to scale the results of the 345­watt EPS across the whole range of high­power EPSs. A full list of high­power EPS representative unit design parameters that DOE fixed for isolating the impacts of efficiency is presented in Table 3.13.NumberofUnits[#] **10**

**8**

**6**

**4**

**2**

**0**

**276 303.6**  **317.4 345**  **414 510.6**  **552 690**  **786.6** Nameplate Output Power [W]

Figure 3.19 Product Count for High­Power EPSs

­

3­34Table 3.13 Characteristics of the High­Power EPS Representative Unit

­

Parameter Values for 345 W EPS Output Voltages and Currents V 1 = 13.8 V, I 1 = 25 A

Input Voltage 115 volts rms, 60 Hz

Input Protection Primary current fuse, inrush current limiting Output Voltage Regulation ± 1% (excluding cord)

Output Voltage Ripple 1% V P­P maximum

Transient Response 0.5 ms for 50% load change typical

Output Protection Overcurrent protection, short­circuit protection

Unit Volume 1,000 units per year

Application Ham radio

Package Metal enclosure with slats

and fan. Output Cord Length 6 feet

Regulatory Compliance UL, FCC

Product Lifetime 10 years

3.6.1.3 Representative Product Classes and Units for Medical EPSs

DOE proposed six product classes for medical EPSs and identified similarities between medical EPSs and Class A EPSs. Because of these similarities, DOE chose only one representative product class and one representative unit for medical EPSs (Table 3.14).

Table 3.14 Representative Product Classes for Medical EPSs

Nameplate Output Voltage Nameplate Output Power

4–60 watts

≤12 volts Medical Product Class 2

DOE chose the medical EPS representative unit based on a market survey it conducted that identified popular nameplate output powers among medical EPSs (Figure 3.20). The survey counted the number of individual medical EPSs available in online distributor catalogs, including Newark.com and AlliedElec.com. Typically, medical EPSs are sold packaged with end­use products; however, DOE evaluated medical EPSs sold separately because it could not obtain

3­35detailed data for EPSs sold with medical products. In total, the survey counted 86 unique medical EPSs. In the survey, most of the units had less than 70 watts nameplate output power. There was a cluster of units with nameplate output power near 18 watts. EPSs with nameplate output power at 50 watts and 60 watts were also popular. DOE chose 18 watts for the medical EPS representative unit because it is a popular wattage and it is the same output power as the Class A EPS representative unit. A full list of high­power EPS representative unit design parameters that DOE fixed for isolating the impacts of efficiency is presented in Table 3.15.

**25**

**20**

**15**

**10**

**5**

**0**

Figure 3.20 Product Count for Medical EPSsProductCount[#]

**0 10**  **20 30**  **40 50**  **60 70**  **80 90**  **100 110**  **120**

Nameplate Output Power [W]

3­36Table 3.15 Characteristics of the Medical EPS Representative Unit

­

Parameter Values for 18 W EPS Output Voltages and Currents V 1 = 12 V, I 1 = 1.5 A

Input Voltage 115 volts rms, 60 Hz

Input Protection Primary current fuse, inrush current limiting Output Voltage Regulation ± 1% (excluding cord)

Output Voltage Ripple 1% VP­P maximum

Transient Response 0.5 ms for 50% load change typical

Output Protection Overcurrent protection, short­circuit protection

Unit Volume 10,000 units per year

Application Medical diagnostic

Package Sealed polycarbonate

Output Cord Length 6 feet

Regulatory Compliance UL 60601­1, FCC

Product Lifetime 8 years

Also, among the 86 medical EPSs surveyed, five units had multiple voltage outputs. Because this group was so limited, DOE did not create a separate product class and representative unit for it. However, medical EPSs with multiple­voltage outputs may be considered in future analyses and/or rulemakings.

3.6.1.4 Representative Product Classes and Units for EPSs for BCs

DOE proposed six product classes for EPSs for BCs and identified similarities between EPSs for BCs and Class A EPSs. Because of these similarities, DOE chose two representative product classes for EPSs for BCs (Table 3.16).

Table 3.16 Representative Product Classes for EPSs for BCs

Nameplate Output Voltage Nameplate Output Power

<4 watts 4–60 watts

≤12 volts EPS for BC Product Class 1

>12 volts EPS for BC Product Class 5

DOE chose the EPSs for BCs representative units based on previous analysis of BCs, detailed in the Framework Document and Draft Technical Report. That analysis identified four

3­37representative units for battery chargers. Table 3.17 lists their characteristics along with the characteristics of their wall adapters. Among these four units, three use wall adapters that were considered as possible representative units for EPSs for BCs: wall adapters for shavers, vacuums, and do­it­yourself tools, which could be considered EPSs for BCs if they meet the scope of DOE’s Approach A for EPSs and BCs discussed in the technology assessment section of the

NOPR.

Table 3.17 Representative Unit Characteristics for Battery Chargers

Application Wall­Adapter

Characteristics Battery Charger Characteristics Output Power [W] Output Voltage [V] Battery Voltage [V] Battery Capacity [Ah] Charge Rate [C]

Shaver 0.3 3 1.2 1.2 0.1

Vacuum 1.8 6 4.8 1.2 0.1

DIY tool 4.8 24 18 1.5 0.15

Pro tool N/A N/A 18 2.4 1

In addition to the three wall adapters from the BC representative units, DOE also considered wall adapters for camcorders because they were identified as a unique application that uses detachable batteries. To decide which among these four possible units would be used as representative units, DOE estimated the total energy consumption for all units sold in a year. DOE chose this metric since it is a good indication of potential savings and impact. Also, DOE could not use the market survey method it used with the other non­Class A EPSs because it is still developing a method for distinguishing EPSs for BCs from other BCs for wall adapters.

To estimate energy consumption, DOE used data listed in Table 3.18 in addition to the data previously discussed. Figure 3.21 presents the estimated total energy consumption for the wall adapters that would be considered EPSs for BCs under DOE’s Approach A. j Among these applications, vacuums and DIY tools consume more than 10 GWh/yr whereas shavers and camcorders consume less than 2 GWh/yr. Therefore, DOE selected as the representative units for EPSs for BCs a 1.8­watt EPS for a vacuum and 4.8­watt EPS for a DIY tool, characteristics of

which are detailed in Table 3.19.

Table 3.18 Assumptions for Calculating Annual Energy Consumption

Application Amount of BC wall adapters that are EPSs for BCs* [%] Monthly Use [uses per month] Amount Typically Unplugged After Use [%]

Shaver 5 ** 4 90

Vacuum 5 ** 4 10

DIY tool 5 ** 2 20

Camcorder 5 ** 0.5 90

* Based on DOE’s Approach A scope of EPSs for BCs.

­ ** The true percentage is lower. Five percent was used as a maximum value.

­

j These estimates are preliminary. More thorough calculations are in section 5.1

3­38**20,000,000**

**15,000,000**

**10,000,000**

**5,000,000**

**0**

**Shaver Vacuum**  **DIY Power**  **Tool Camcorder** 

Application of EPS for BC

Figure 3.21 Estimate of Energy Consumption for Different EPSs for BCsEstimateofAnnualEnergyConsumption[kwh/hr]

3­39Table 3.19 Characteristics of the EPS for BCs Representative Units

­

Parameter Values for 1.8 W EPS Values for 4.8 W EPS Output Voltages and Currents V 1 = 6 V, I 1 = 0.3 A V 1 = 24 V, I 1 = 0.2 A

Input Voltage 115 volts rms, 60 Hz 115 volts rms, 60 Hz

Input Protection

­ ­ Output Voltage Regulation

­ ­ Output Voltage Ripple

­ ­

Transient Response

­ ­

Output Protection

­ ­

Unit Volume 1M units/year 1M units/year

Application Cordless Hand Vacuum Cordless DIY Power Tool

Package Sealed plastic Sealed plastic

Output Cord Length 6 feet 6 feet

Regulatory Compliance UL, FCC UL, FCC

Product Lifetime 5 years 5 years

3.7 Selection of Candidate Standard Levels

CSLs are generally based on (1) efficiencies achievable by commonly used design options, (2) voluntary guidelines or mandatory standards already in existence that have prompted manufacturers to develop products at particular efficiency levels, and (3) the max­tech level. k For example, DOE often considers the ENERGY STAR level as one CSL, while the least efficient models in a product class typically serve as the baseline CSL. Basing CSLs on established guidelines or standards increases the availability of data because manufacturers may have already designed products to meet the CSL, and may therefore be able to provide cost information. Furthermore, products meeting the CSL may exist in the marketplace and be available for testing and teardowns, further strengthening the analysis.

Specifically in this analysis CSLs are based on (1) EPSs that have been tested and torn down, (2) data points provided in manufacturer interviews and (3) the International Efficiency Marking Protocol for External Power Supplies. l In choosing the basis for the CSLs, DOE gave

k The max­tech level represents the most efficient design that has been demonstrated in a prototype with materials or

­ technologies available today. Max­tech is not constrained by economic justification, and typically is the most

­ expensive design option considered in the engineering analysis.

­ l Energy Star. International Efficiency Marking Protocol for External Power Supplies . 2008.

­ www.energystar.gov/ia/partners/prod_development/revisions/downloads/International_Efficiency_Marking_Protoco

­ l.pdf (Last accessed November 18, 2008.)

­

3­40the highest priority to units that were torn down and tested because DOE had complete data for efficiency and cost. If test and teardown data were not available then DOE used data points provided by manufacturers. Last, if no data were directly available, DOE referred to the International Marking Protocol. Where possible, DOE tried to relate CSLs to design options.

However, even if CSLs are based on design options in units currently being manufactured, they should not be seen as technologically prescriptive. In other words, manufacturers are free to use any combination of design options to achieve the efficiency specified by a given CSL. To maintain this approach throughout the analysis, DOE did not examine CSLs that could only be achieved through proprietary design options not available to all

manufacturers.

The CSLs are specified in terms of the efficiency metrics utilized in DOE’s test procedure for single­voltage EPSs and a proposed test procedure for multiple­voltage EPSs: active mode conversion efficiency and no­load mode power consumption. Because both of the efficiency metrics output by the EPS test procedure affect the energy consumption of the unit, DOE developed CSLs that included “matched pairs” of limits on both metrics simultaneously. Matched pairs allowed DOE to base CSLs on existing EPS standards, such as those developed by ENERGY STAR. As these CSL matched pairs progress from least to most efficient, either the active mode efficiency or no­load power­consumption requirements, or both, increase in stringency. By preventing a decrease in the stringency of these metrics, DOE makes a tacit assumption that there is no trade­off between EPS performance in the two modes, and increasing the energy savings in one mode does not necessarily cause a decrease in energy savings in the

other.

To verify this assumption, DOE analyzed the relationship between active mode efficiency and no­load power consumption for products currently in the market. Figure 3.22 plots efficiency measurements conducted by DOE on EPSs with nameplate output power around 5 watts and 60 watts. The figure shows that EPSs with higher active mode efficiencies tend to also have lower no­load­mode power consumption. This is probably true only up to a point, however, and one can imagine cases in which an EPS manufacturer tries to minimize no­load power, but can only do so at the expense of lower active mode efficiency. Therefore, DOE based its matched pairs on those currently seen in the market. The CSLs followed—as much as possible—the efficiency metrics achieved by actual EPSs at representative­unit output powers and voltages.This ensured that EPSs currently produced would be able to meet both active mode and no­loadmode requirements.

3­41**0 0.5** 

**1 1.5** 

**2 2.5** **No­Load Power** **[W] 0–6**  **Watts Maximum**  **Rated Output**  **Power**
**40–66 Watts**  **Maximum Rated**  **Output Power** 

**20% 30%**  **40% 50%**  **60% 70%**  **80% 90%** 



### Average **Efficiency [%]** 

Figure 3.22 Comparison of Active Mode Efficiency and No­Load Power; Arrows Point in Direction of Increased Efficiency

For each of the six representative units, DOE created four CSLs, although it may create more levels in future analysis or in response to stakeholder comment. These CSLs are intended to reflect the efficiencies in the market, although they do not necessarily include the highest efficiencies. The CSLs in this analysis are sufficient for the determination analysis to demonstrate whether DOE should conduct a standards rulemaking. In future analysis, DOE may include a max­tech CSL to reflect the highest achievable efficiency.

3.7.1.1 Candidate Standard Levels for Multiple­Voltage EPSs

On behalf of DOE, Navigant Consulting, Inc. collected data from original equipment manufacturers (OEMs) of multi­function devices and video games that use multiple­voltage EPSs with their products as well as EPS manufacturers themselves. In addition, DOE tested the efficiency of two EPSs for multiple­function devices and four EPSs for video games. These data sources indicated that there is a limited spectrum of efficiencies in the multiple­voltageEPS market, typically with conversion efficiency above 80%. No­load power for multiplefunction devices tended to be less than one watt whereas DOE measured EPSs for video game consoles with no­load power greater than 12 watts.

Table 3.20 and Table 3.21 show the CSLs for the two multiple­voltage EPSs.

3­42Table 3.20 Candidate Standard Levels for a 40­Watt Multiple­Voltage EPS for a MultiFunction Device

Level Reference Minimum Efficiency [%] Maximum No­Load Power [W] Basis

0 Current Market 80.8 0.50 Manufacturer interview

1 Mid level 85.9 0.45 Manufacturer interview

2 High level 89.9 0.31 Manufacturer interview

3 Higher level 90.9 0.20 Manufacturer interview

Table 3.21 Candidate Standard Levels for a 203­Watt Multiple­Voltage EPS for a Video

Game Console

Level Reference Minimum Efficiency [%] Maximum No­Load Power [W] Basis

0 Generic Replacement 82.4 12.33 Tested unit (#213)

1 Manufacturer Provided 86.4 0.40 Tested units (#206, #214)

2 EU Qualified Level 86.4 0.30 Manufacturer

interview

3 Higher level 88.5 0.30 Manufacturer

interview

DOE created CSLs for the 40­watt EPS based on values provided by a manufacturer during an interview. The manufacturer provided cost­efficiency points at four levels in terms of both maximum efficiency and no­load power consumption. The manufacturer describes an EPS meeting CSL 0 as a switched­mode EPS with a flyback topology. To achieve the higher efficiency of CSL 1, the metal–oxide–semiconductor field­effect transistor (MOSFET) that controls the current into the transformer could be replaced with a MOSFET with lower resistance when turned on (R ds_on ). To meet CSL 2 the manufacturer would design an EPS with three major changes in addition to maintaining the MOSFET with lower R ds_on : (1) use a more advanced integrated circuit (IC) with a more efficient switching algorithm, (2) use a transformer with lower losses, and (3) change the output diode from a standard diode to a Schottky diode. Last, to meet CSL 3, the EPS would have synchronous rectification instead of a Schottky diode and the transformer, chokes, and MOSFET would all have low losses.

The manufacturer’s range efficiencies encompassed the measured efficiencies of EPS#217 (85.7% efficient, 0.27 watts no­load power) and EPS #218 (84.4% efficient, 0.26 watts noload power). Originally, the manufacturer provided the conversion efficiency values in terms of efficiency at full load (100% of nameplate output current) rather than at average loading, which is DOE’s metric. DOE analysis of EPSs #217 and #218 indicate that their average efficiency was

1.01 times higher than the full­load efficiency. Therefore, DOE multiplied the original manufacturer maximum efficiency points by 1.01 to estimate the average efficiency. There was no need to adjust the no­load power, which DOE used directly in the CSLs. EPSs #217 and #218

3­43meet CSL 0 because their efficiency is not greater than the efficiency at CSL 1. DOE chose to maintain the manufacturer’s levels for consistency between the matched pairs and because the no­load power is an indication of a maximum, so there was no conflict if the tested units had lower no­load power than the candidate standard level.

For candidate standard level 0 and CSL 1 for the 203­watt EPS, DOE based its CSLs on units measured in the market. Specifically, CSL 0 reflects the efficiencies of generic replacement EPSs made by manufacturers other than Microsoft. DOE tested two such EPSs whose efficiencies were lower than the EPS currently provided by the video game manufacturer: EPS #213 (82.4% efficient, 12.33 watts no­load power) and EPS #216 (81.2% efficient, 5.16 watts no­load power). DOE based CSL 0 directly on the tested values measured for EPS #213 because it also obtained an estimated ERPC for the unit. Maintaining the same source for both allows for consistency between the EPS cost and efficiency.

For the 203­watt EPS, CSL 1 is supposed to reflect the efficiency of the 203­watts EPSs that were sold with the Xbox 360 game console. DOE based CSL 1 on two units: the conversion efficiency of EPS #203 (86.4% efficient, 3.29 watts no­load power) and the no­load power of EPS #214 (84.5% efficient, 0.4 watts no­load power). DOE used two different units because of possible discrepancies within the data. In particular, DOE purchased EPS #203 individually (as opposed to being sold with the game console) through a third­party retailer on Amazon.com. Because EPS #203 was not purchased with the game console, DOE cannot definitively confirm that the EPS is an authentic Microsoft product, despite having a Microsoft label. Further, Microsoft reported to DOE that the original 203­watt EPS it used with the console has a no­load power of approximately 0.4 watts. m To that end, Microsoft provided DOE with EPS #214, which DOE tested to verify Microsoft’s assertion. Therefore, DOE used the conversion efficiency from EPS #203 because DOE has an estimate of the ERPC for this unit. However, the no­load power comes from EPS #214 to better reflect the no­load power consumption of products sold in the

market.

Candidate standard level 2 and CSL 3 come from manufacturer interviews with Microsoft who detailed methods for improving the no­load power and conversion efficiency of the 203­ watt EPS. CSL 2 reflects a reduction in no­load power to 0.3 watts. To achieve this Microsoft reduced losses in the transformer core, changed the switching frequency, and optimized the circuitry of the EPS. n Microsoft originally designed the EPS for lower no­load power consumption as part of an effort to comply with the European Union standard for a maximum of one­watt standby power consumption (when the console is turned off and attached to the EPS), hence CSL 2 is referred to as the “EU qualified level.” In addition, Microsoft believes that it can increase the conversion efficiency of the EPS by 2.15% by replacing Schottky diodes with a synchronous rectification circuit and by using MOSFETs with lower R ds_on

. o

m Calland, T. Personal communication. Microsoft Corp, Redmond, WA. Email to Michael Vladimer, Navigant

­ Consulting, Inc. February 9, 2009.

­

n Calland, T. Personal communication. Microsoft Corp, Redmond, WA. Email to Michael Vladimer, Navigant

­ Consulting, Inc. February 9, 2009.

­

o Calland, T. Personal communication. Microsoft Corp, Redmond, WA. Email to Victor Petrolati, DOE, and Michael Vladimer, Navigant Consulting, Inc. November 4, 2008.

3­443.7.1.2 Candidate Standard Levels for High­Power EPSs

DOE developed candidate standard levels for the 345­watt representative unit for highpower EPSs based on data from tested and torn down units as well as manufacturer interviews. On behalf of DOE, Navigant Consulting, Inc. collected data from distributors and manufacturers of power supplies for ham radios. In addition, DOE tested the efficiency of four high­power EPSs. These data sources indicated that there is a wide, divided spectrum of efficiencies in the high­power EPS market: lower efficiencies for line­frequency power supplies and higher efficiencies for switched­mode power supplies. Table 3.22 shows the CSLs for high­power

EPSs.

Table 3.22 Candidate Standard Levels for a 345­Watt High­Power EPS for a Ham Radio

Level Reference Minimum Efficiency [%] Maximum

No­Load Power [W] Basis

0 Line Frequency 62.4 15.43 Tested unit (#401)

1 Switched­mode ­ Low

Level 81.3 6.01 Tested unit (#402)

2 Switched­mode ­ Mid

Level 83.5 1.50 Manufacturer

interview

3 Switched­mode ­ High

Level 85.0 0.50 Manufacturer

interview

The lowest CSL corresponds to line frequency EPSs. DOE tested two line frequency EPSs: EPS #401 (62.4% efficient, 15.43 watts no­load power) and EPS #404 (50.7% efficient,

12.6 watts no­load power). DOE used EPS #401 as the sole basis for CSL 0 because that unit was costed by iSuppli which allows the cost for the CSL to be related to an exact data point. Similarly, DOE based CSL 1 on the tested values of a switched­mode EPS #402 (81.3% efficient, 6.01 watts no­load power) because iSuppli also costed this unit. CSL 2 and CSL 3came from interviews with a designer and distributor of high­power EPSs. Specifically, the highpower EPS designer indicated that the higher efficiency of CSL 2 could be achieved by using an IC with a more efficient switching algorithm. The distributor of high­power EPSs indicated that higher efficiencies such as CSL 3 were possible by changes such as replacing rectifying diodes with a synchronous rectification circuit. Candidate standard levels 2 and 3 were verified as reasonable by a subject matter expert familiar with high power EPSs. p

3.7.1.3 Candidate Standard Levels for Medical Device EPSs

DOE developed candidate standard levels for the 18­watt representative unit for medical device EPSs based on data from manufacturer interviews, laboratory testing, and the international efficiency marking protocol. On behalf of DOE, Navigant Consulting, Inc.

collected data from medical device EPS manufacturers. Manufacturers indicated that medical

p Rodriguez, E. Personal communication . OptoThermal Technologies, Wakefield, MA. Telephone conversation with Michael Vladimer, Navigant Consulting, Inc. February 5, 2009.

3­45requirements should not affect an EPS’s efficiency. DOE verified that assertion by testing two medical EPSs and comparing them to four Class A EPSs. These test data indicated that efficiencies are comparable between the two types of EPSs. Therefore DOE based most of the CSLs for medical EPSs on the International Efficiency Marking Protocol for External Power Supplies that applies to Class A 18W EPSs (Table 3.23). The lowest level, “Less than the II mark” is based on the efficiency of a line­frequency Class A EPS with a nameplate output power of 14.4 watts and nameplate output voltage of 12 volts. DOE scaled the efficiency of the unit to determine that its expected efficiency, if it were to be an 18­watt EPS is 66.0 percent, hence the conversion efficiency of CSL 0. The maximum no­load power for CSL 0 is the same as for CSL 1, the mark II level. Candidate standard level 0 has a maximum no­load power of 1 watt, which is the same level as CSL 1, because EPS #130 consumed 0.56 watts of no­load power.

To develop the requirements for CSL1 and CSL2, DOE observed that there was no clear relationship for the switched­mode EPSs with average active­mode efficiency and the no­load power requirements between mark II (70% efficient and 1­watt no­load power consumption) and mark IV (76% efficient and 0.5­watts no­load power consumption) for an 18­watt EPS according to the International Efficiency Marking Protocol for External Power Supplies. DOE was confident that EPSs already available on the market could meet a standard set at the mark IV requirements because some tested units demonstrated this fact. DOE thus chose to use theserequirements for CSL2. A manufacturer stated that it is possible to meet this CSL with a switchmode EPS using a flyback topology and a specific PWM IC as well as a Schottky diode on the EPS’s output rectifier.

The same manufacturer discussed ways to produce a medical device EPS with an average active­mode efficiency of 85% and a maximum no­load power of 0.15 watts. DOE used these characteristics as the requirements for CSL3 for medical device EPSs. These requirements can be met through the usage of a quasi­resonant PWM circuit, a primary field­effect transistor (FET) and secondary synchronous circuit with low voltage drops, wiring with an increased gauge, and aplanar transformer. Table 3.23 details the minimum active­mode efficiency and maximum noload power requirements for all CSLs for medical device EPSs.

Table 3.23 Candidate Standard Levels for an 18­Watt Medical Device EPS for a

Nebulizer

Level Reference Minimum Efficiency [%] Maximum No­Load Power [W] Basis

0 Less than the II mark 66.0 1.00 Scaled tested unit (#130), Marking protocol

1 Meets the II mark 69.9 1.00 Marking protocol

2 Meets the IV mark 76.0 0.50 Marking protocol

3 Higher level 85.0 0.15 Manufacturer interview

3­463.7.1.4 Candidate Standard Levels for EPSs for BCs

DOE developed candidate standard levels for the 1.8­watt and 4.8­watt representative units for EPSs for BCs based on data from laboratory testing of Class A EPSs. DOE based CSL 0 on the scaled efficiency test results of the least efficient tested unit, EPS #17, which is a line­frequency EPS. The higher CSLs are based on the international efficiency marking levels for a Class A 1.8W EPS and a Class A 4.8W EPS, shown in Table 3.24 and Table 3.25, respectively. DOE chose to use the marking levels because DOE observed that there were EPSs available on the market that could already meet the average active­mode efficiency and no­load power requirements of the levels.

Table 3.24 Candidate Standard Levels for a 1.8­Watt EPS for BC for a Vacuum

Level Reference Minimum Efficiency [%] Maximum No­Load Power [W] Basis

0 Less than the II mark 24.3 1.85 Scaled tested unit (#17)

1 Meets the II mark 45.3 0.75 Marking protocol

2 Meets the IV mark 55.3 0.50 Marking protocol

3 Meets the V mark 65.9 0.30 Marking protocol

Table 3.25 Candidate Standard Levels for a 4.8­Watt EPS for a Do­It­Yourself Power

Tool

Level Reference Minimum Efficiency [%] Maximum No­Load Power [W] Basis

0 Less than the II mark 37.6 1.85 Scaled tested unit (#17)

1 Meets the II mark 55.8 0.75 Marking protocol

2 Meets the IV mark 64.1 0.50 Marking protocol

3 Meets the V mark 72.0 0.30 Marking protocol

3­47CHAPTER 4 ENERGY USE AND END­USE LOAD CHARACTERIZATION

­

4.1 Introduction

This chapter provides an example walkthrough of the methodology DOE used in its determination analysis to calculate the annual unit energy consumption (UEC) of an external power supply (EPS). The methodology is implemented in a Microsoft ® Excel workbook that can

be downloaded from the EERE web site. a

Section 4.2 provides a walkthrough of unit energy consumption for the multiple voltage EPS used to power an Xbox 360.

Section 4.3 provides inputs and calculated unit energy consumption values for all remaining EPSs.

Section 4.4 provides the methodology for calculating EPS power consumption for all modes of operation.

4.2 Walkthrough of Unit Energy Consumption Calculation

This section presents the inputs and calculations in the same order as they appear in the NOPR. In the following sub­sections, DOE discusses the following inputs:

4.2.1 Usage Profile for Multiple­Voltage EPS (203W, Xbox 360)

4.2.2 EPS Power Consumption by Modes of Operation

4.2.3 Active Mode Efficiency and No Load Mode Power Consumption

4.2.4 Calculating Unit Energy Consumption

a Available for download from the EERE website: http://www.eere.energy.gov/buildings/appliance_standards/residential/battery_external.html

4­14.2.1 Usage Profile for Multiple­Voltage EPS (203W, Xbox 360)

In the NOPR, DOE defined two usage profiles for the Xbox 360, one for a light user and one for a heavy user. These usage profiles were combined to create a weighted­average usage profile as shown in Table 4.1

Table 4.1 Weighted­Average Usage and Output Power of EPS for Xbox 360

EPS Mode Application

State Annual Usage (hours/year) EPS Output

Power* [W] Light User
[80%] Heavy User
[20%] WeightedAverage

User

Active Playing Video

Game 500 2,100 820

102.62

Idle Video

Game 560 560 560

101.50

Playing DVD 90 90 90 95.02

Idle DVD 150 150 150 95.02

Idle – No Disc 150 150 150 86.38

Off 7,310 5,710 6,990 2.35

No Load Disconnected

from EPS 0 0 0 0

Unplugged

— 0 0 0 0

* Output power levels for all application states were derived from input power measurements reported in NRDC, "Lowering the Cost of Play: Improving the Energy Efficiency of Video Game Consoles," November 2008 using DOE’s measurements of the efficiency and no­load power consumption of the EPS that ships with the Xbox 360.
Video game application state usage estimates: Nielsen Wireless and Interactive Services, "The State of the Console ­ Video Game Console Usage ­ Fourth Quarter 2006," 2007.
DVD Usage Estimates: TIAX, "Energy Consumption by Consumer Electronics in U.S. Residences," Final Report to the Consumer Electronics Association, January 2007. (Adjusted to 33% of use per “Lowering the Cost of Play,” cited above.)

4.2.2 EPS Power Consumption by Modes of Operation
In the NOPR, DOE described the following loads for each application state. In addition, DOE calculated the load as a percentage of nameplate output power, to be used in the next section to determine the equation used for calculating energy consumption. Table 4.2 shows an example of load by application state for the EPS for the Xbox 360.

4­2Table 4.2 Load by Application State for EPS for Xbox 360

­

EPS Mode Application State EPS Output Power [W] Percentage of Nameplate Output Power [%]

Active Playing Video Game 102.62 51

Idle Video Game 101.50 50

Playing DVD 95.02 47

Idle DVD 95.02 47

Idle – No Disc 86.38 43

Off 2.35 1

No Load Disconnected from

EPS 0

­

Unplugged

— 0

­

4.2.3 Active Mode Efficiency and No Load Mode Power Consumption
Table 4.3 shows the minimum active mode efficiency and the maximum no load mode power consumption for each CSL.

Table 4.3 Candidate Standard Levels for an EPS for Xbox 360

CSL Minimum Active Mode Efficiency [%] Maximum No­Load Power [W]

0 82.4 12.33

1 86.4 0.40

2 86.4 0.30

3 88.5 0.30

4.2.4 Calculating Unit Energy Consumption
Using the above inputs, DOE calculated UEC as the sum of energy consumption in all

EPS modes:

E Con = P CON­Active1 * T Active1 + Eq. 6.1

P CON­Active2 * T Active2 +

P CON­Active3 * T Active3 +

P CON­Active4 * T Active4 +

P CON­Active5 * T Active5 +

P CON­Active6 * T Active6 +

P CON­No­Load * T No­Load

For all the active application states, P Con is a function of P Out . The function selected depends on the load of the application state. For each application state with a load greater or equal to 25 percent of nameplate output power, P Con was calculated using the following equation:

4­3P Con = P Out x (1/η – 1) Eq. 6.2

For each application state with a load less than 25 percent of nameplate output power,

P Con was calculated using the following equation:

P Con = ({[(25% x [P Nameplate / η]) – P NL ] / [25% x P Nameplate ]}­1) x P Out + P NL Eq. 6.3

For no load mode, P Con is simply P NL:

P Con = P NL Eq. 6.4

Table 4.4 indicates which equation was used to calculate energy consumption in each application state and each EPS mode.

Table 4.4 Equations Used to Calculate Energy Consumption in Each Application State

EPS Mode Application State EPS Output Power* [W] Percentage of Nameplate Output Power [203 W] Equation

Used

Active Playing Video Game 102.62 51 6.2

Idle Video Game 101.50 50 6.2

Playing DVD 95.02 47 6.2

Idle DVD 95.02 47 6.2

Idle – No Disc 86.38 43 6.2

Off 2.35 1 6.3

No Load Disconnected from

EPS 0

­ 6.4

Unplugged

— 0

­ ­

* The values in this table are the results of the calculations described above and so, due to rounding errors, may not exactly match the values actually used in the determination analysis.

P Con and UEC are calculated for each application state and each EPS mode in the following seven tables.

4­4Table 4.5 UEC for Active – Playing Video Game (EPS Output Power = 102.62 W)

­

CSL Minimum

Active Mode

Efficiency [%] P Con­Active1 [W] (Equation 6.2) Weighted Average Usage

[hours/year] Unit Energy Consumption

[kWh/year]

0 82.4 102.62 x [(1/0.824)­1] =

21.92 820 17.97

1 86.4 102.62 x [(1/0.864)­1] =

16.15 820 13.24

2 86.4 102.62 x [(1/0.864)­1] =

16.15 820 13.24

3 88.5 102.62 x [(1/0.885)­1] =

13.33 820 10.93

Table 4.6 UEC for Active – Idle Video Game (EPS Output Power = 101.50 W)

­

CSL Minimum

Active Mode

Efficiency [%] P Con­Active1 [W] (Equation 6.2) Weighted Average Usage

[hours/year] Unit Energy Consumption

[kWh/year]

0 82.4 101.50 x [(1/0.824)­1] =

21.68 560 12.14

1 86.4 101.50 x [(1/0.864)­1] =

15.97 560 8.94

2 86.4 101.50 x [(1/0.864)­1] =

15.97 560 8.94

3 88.5 101.50 x [(1/0.885)­1] =

13.18 560 7.73

Table 4.7 UEC for Active – Playing DVD (EPS Output Power = 95.02 W)

­

Level Minimum

Active Mode

Efficiency [%] P Con­Active1 [W] (Equation 6.2) Weighted Average Usage

[hours/year] Unit Energy Consumption

[kWh/year]

0 82.4 95.02 x [(1/0.824)­1] =

20.29 90 1.83

1 86.4 95.02 x [(1/0.864)­1] =

14.95 90 1.35

2 86.4 95.02 x [(1/0.864)­1] =

14.95 90 1.35

3 88.5 95.02 x [(1/0.885)­1] =

12.35 90 1.11

4­5Table 4.8 UEC for Active – Idle DVD (EPS Output Power = 95.02 W)

­

CSL Minimum

Active Mode

Efficiency [%] P Con­Active1 [W] (Equation 6.2) Weighted Average Usage

[hours/year] Unit Energy Consumption

[kWh/year]

0 82.4 95.02 x [(1/0.824)­1] =

20.29 150 3.04

1 86.4 95.02 x [(1/0.864)­1] =

14.95 150 2.24

2 86.4 95.02 x [(1/0.864)­1] =

14.95 150 2.24

3 88.5 95.02 x [(1/0.885)­1] =

12.35 150 1.85

Table 4.9 UEC for Active – Idle No­Disc (EPS Output Power = 86.38 W)

­

CSL Minimum

Active Mode

Efficiency [%] P Con­Active1 [W] (Equation 6.2) Weighted Average Usage

[hours/year] Unit Energy Consumption

[kWh/year]

0 82.4 86.38 x [(1/0.824)­1] =

18.45 150 2.77

1 86.4 86.38 x [(1/0.864)­1] =

13.60 150 2.04

2 86.4 86.38 x [(1/0.864)­1] =

13.60 150 2.04

3 88.5 86.38 x [(1/0.885)­1] =

11.22 150 1.68

Table 4.10 UEC for Active – Off (EPS Output Power = 2.35 W)

­

CSL Minimum

Active Mode

Efficiency [%] P NL [W] P Con­Active1 [W] (Equation 6.3)

0 82.4 12.33 ({[0.25 x [203/0.824])­12.33]/[0.25 x 203]}­1) x 2.35 +

12.33 = 12.26

1 86.4 0.40 ({[0.25 x [203/0.864])­0.4]/[0.25 x 203]}­1) x 2.35 + 0.4 =

0.75

2 86.4 0.30 ({[0.25 x [203/0.864])­0.3]/[0.25 x 203]}­1) x 2.35 + 0.3 =

0.66

3 88.5 0.30 ({[0.25 x [203/0.885])­0.3]/[0.25 x 203]}­1) x 2.35 + 0.3 =

0.59

4­6Table 4.11 UEC for Active ­ Continued

­

CSL P Con­Active1 [W] Weighted Average Usage

[hours/year] Unit Energy Consumption

[kWh/year]

0 12.26 6,990 85.70

1 0.75 6,990 5.24

2 0.66 6,990 4.61

3 0.59 6,990 4.12

Table 4.12 UEC for No Load Mode

­

CSL P NL (W) P Con­NoLoad [W] (Equation 6.4) Weighted Average Usage [hours/year] Unit Energy Consumption

[kWh/year]

0 12.33 12.33 0 0

1 0.40 0.40 0 0

2 0.30 0.30 0 0

3 0.30 0.30 0 0

The UECs calculated in the preceding tables are summarized in Table 4.13.

­

4­7Table 4.13 UEC by Application State at Each Candidate Standard Level

­

EPS Mode Application

State UEC (kWh/year)*

CSL 0 CSL 1 CSL 2 CSL 3

Active Playing Video

Game 17.9 13.3 13.3 10.9

Idle Video

Game 12.1 9.0 9.0 7.4

Playing DVD 1.8 1.3 1.3 1.1

Idle DVD 3.0 2.2 2.2 1.8

Idle – No Disc 2.8 2.0 2.0 1.7

Off 88.3 4.6 4.0 3.7

No Load Disconnected

from EPS 0 0 0 0

Unplugged

— 0 0 0 0

Total UEC: 126.01 32.44 31.85 26.57

* The values in this table are the results of the calculations described above and so, due to rounding errors, may not exactly match the values actually used in the determination analysis.

Inputs and calculated UEC values for other EPSs are listed in the following sections. For the specific calculations please refer to the UEC workbook.

4.3 Unit Energy Consumption Values for Non­Class A External Power Supplies

The following tables show, for each type of non­Class A EPS, the candidate standard levels, usage profiles and unit energy consumption values calculated at each candidate standard level in each application state.

4.3.1 Multiple­Voltage EPS for Multifunction Devices

Table 4.14 Candidate Standard Levels for 40 W Multiple­Voltage EPS for Multifunction

Devices

CSL Reference point for level Minimum Efficiency [%] Maximum No­Load Power [W]

0 Current level 80 0.6

1 EISA level 83 0.5

2 Greater than EISA 85 0.4

3 Higher level 89 0.3

4­8Table 4.15 Usage and Output Power of EPS for 40 W Multiple­Voltage EPS for

Multifunction Devices

EPS

Mode Application State Annual Usage
[hours/year] EPS Output Power [W]

Active Printing, Photocopying, Faxing, Scanning 52 32*

Idle 1,606 9.1

Off 7,102 6.2

No Load Disconnected from

EPS 0 0

Unplugged Disconnected from

EPS 0 0

* DOE estimated EPS output power for printing, photocopying, faxing, and scanning to be 80 percent of nameplate output power.

Table 4.16 Unit Energy Consumption for 40 W Multiple­Voltage EPS for Multifunction

Devices

CSL Unit Energy Consumption (kWh/year) EPS Active Mode (Application State) EPS NoLoad Mode Total Printing, Copying, Faxing, Scanning Idle Off

0 0.40 3.55 11.81

­ 15.75

1 0.27 2.47 8.47

­ 11.22

2 0.19 1.69 5.79

­ 7.66

3 0.17 1.49 4.95

­ 6.61

4.3.2 High­Power EPS for Amateur Radio Equipment

Table 4.17 Candidate Standard Levels for 345 W High­Power EPS for Amateur Radio Equipment

CSL Reference point for level Minimum Efficiency [%] Maximum No­Load Power [W]

0 Line Frequency 50 16

1 Switched­mode – Low Level 81 6

2 Switched­mode – Mid Level 84 2

3 Switched­mode – High Level 87 1.5

4­9Table 4.18 Light Usage of 345 W High­Power EPS for Amateur Radio Equipment

­

EPS

Mode Application

State Annual Usage (hours/year) Reasoning

Active Transmitting 10 Radio setup is used roughly 2 hours a week, during which time the equipment is transmitting for 10 percent of the time, receiving for 10 percent of the time, and idle for the remaining time. Receiving 10

Idle 80

No Load Disconnected

from EPS 0 The EPS is never disconnected from the

load but left connected to mains.

Off or Unplugged — 8,660 The EPS is either turned off or unplugged and stored when not in use.

Table 4.19 Medium Usage of 345 W High­Power EPS for Amateur Radio Equipment

­

EPS

Mode Application

State Annual Usage (hours/year) Reasoning

Active Transmitting 100 Radio setup is used roughly 20 hours a week, during which time the equipment is transmitting for 10 percent of the time, receiving for 10 percent of the time, and idle for the remaining time. Receiving 100

Idle 1,600 Assumes that roughly 90 percent of

medium users turn the EPS off when not in use and that the remaining 10 percent leave it on.

No Load Disconnected

from EPS 0 The EPS is never disconnected from

the load but left connected to mains.

Off or Unplugged — 6,960 The EPS is turned off when not in use, but is never unplugged.

4­10Table 4.20 Heavy Usage of 345 W High­Power EPS for Amateur Radio Equipment

­

EPS

Mode Application

State Annual Usage (hours/year) Reasoning

Active Transmitting 438 Radio setup is always on, during which the equipment is transmitting for 5 percent of the time, receiving for 5 percent of the time, and idle for the remaining time. Receiving 438

Idle 7,884

No Load Disconnected

from EPS 0 The EPS is never disconnected from the

load but left connected to mains.

Off or Unplugged — 0 The EPS is never turned off or unplugged.

Table 4.21 Weighted­Average Usage and Output Power of 345 W High­Power EPS for Amateur Radio Equipment

EPS Mode Application

State Annual Usage (hours/year) EPS Output

Power

[W]* Light

User
(50%) Medium

User
(25%) Heavy

User
(25%) Weighte

dAverage

User

Active Transmitting 10 100 438 140 276

Receiving 10 100 438 140 69

Idle 80 1,600 7,884 2,411 69

No Load Disconnected

from EPS 0 0 0 0 0

Off or Unplugged — 8,660 6,960 0 6,070 0

* DOE estimated output power levels at 80 percent of nameplate for transmitting and at 20 percent of nameplate for receiving or idle.

4­11Table 4.22 Unit Energy Consumption for 345 W High­Power EPS for Amateur Radio Equipment

CSL Unit Energy Consumption (kWh/year) EPS Active Mode (Application State) EPS NoLoad Mode Total Transmitting Receiving Idle

0 23.23 6.24 107.82

­ 137.29

1 8.84 2.38 41.08

­ 52.30

2 7.61 1.94 33.60

­ 43.15

3 6.79 1.71 29.60

­ 38.11

4.3.3 EPS for Medical Devices

Table 4.23 Candidate Standard Levels for 18 W EPS for Medical Devices

CSL Reference point for level Minimum Efficiency [%] Maximum No­Load Power [W]

0 Less than the II mark 66 2

1 Meets the II mark 70 1

2 Meets the IV mark 76 0.5

3 Meets the V mark 80 0.3

Table 4.24 Medium Usage of 18 W EPS for Medical Devices

­

EPS

Mode Application

State Annual Usage (hours/year) Reasoning

Active On 121.7 The medical device is used twice daily.

Off 8,638.3 The medical device is turned off when

not in use.

No Load Disconnected

from EPS 0 The EPS is never disconnected from the

load.

Unplugged

— 0 The EPS is never disconnected from

mains.

4­12Table 4.25 Heavy Usage of 18 W EPS for Medical Devices

­

EPS

Mode Application

State Annual Usage (hours/year) Reasoning

Active On 182.5 The medical device is used three times daily.

Off 8,577.5 The medical device is turned off when

not in use.

No Load Disconnected

from EPS 0 The EPS is never disconnected from the

load.

Unplugged

— 0 The EPS is never disconnected from

mains.

Table 4.26 Weighted­Average Usage and Output Power of 18 W EPS for Medical Devices

­

EPS

Mode Application

State Annual Usage (hours/year) EPS Output

Power

[W]* Light

User
(33%) Medium

User
(34%) Heavy

User
(33%) WeightedAverage

User

Active On 60.8 121.7 182.5 121.7 14.4

Off 8,699.2 8,638.3 8,577.5 8,638.3 0.9

No Load Disconnected

from EPS 0 0 0 0 0

Unplugged

— 0 0 0 0 0

* DOE estimated output power levels at 80 percent of nameplate when the application is on, and at 20 percent of nameplate when the application is off.

Table 4.27 Unit Energy Consumption for 18 W EPS for Medical Devices

­

CSL Unit Energy Consumption (kWh/year) EPS Active Mode (Application State) EPS No­Load

Mode Total

On Off

0 0.90 7.20

­ 8.11

1 0.55 5.42

­ 5.97

2 0.43 3.65

­ 4.08

3 0.31 2.21

­ 2.52

4­134.3.4 EPS for Battery Chargers for Floor Care Appliances

Table 4.28 Candidate Standard Levels for 1.8 W EPS for Floor Care Appliances

CSL Reference point for level Minimum Efficiency [%] Maximum No­Load Power [W]

0 Less than the II mark 30 1.5

1 Meets the II mark 45 0.75

2 Meets the IV mark 55 0.5

3 Meets the V mark 66 0.3

Table 4.29 Usage and Output Power of 1.8 W EPS for Floor Care Appliances

­

EPS

Mode Application

State Annual Usage (hours/year) Reasoning EPS Output

Power (W)

Active Active Charging 416 The battery undergoes one 24 hour charging cycle a week. During this charging cycle, the battery is in an active charging state for 8

hours. 1.44

Maintenance 8,292 When the vacuum is not in an active charging state or in use, the vacuum is left

in the cradle and/or

attached to the EPS. 0.63

No Load Disconnected

from

EPS/Cradle 52 The vacuum is used for a total of 1 hour per week. While in use, the vacuum (and integrated battery) are

disconnected from the

cradle/EPS. 0

Unplugged

— 0 The EPS is never

disconnected from mains. 0

Table 4.30 Unit Energy Consumption for 1.8 W EPS for Floor Care Appliances

­

CSL Unit Energy Consumption (kWh/year) EPS Active Mode (Application State) EPS NoLoad Mode Total Active Charging Maintenance No­Battery

0 1.87 16.23 0.10

­ 18.20

1 0.73 6.31 0.04

­ 7.08

2 0.49 4.22 0.03

­ 4.74

3 0.31 2.71 0.02

­ 3.03

4­144.3.5 EPS for Battery Chargers for Power Tools

Table 4.31 Candidate Standard Levels for 4.8 W EPS for Power Tools

CSL Reference point for level Minimum Efficiency [%] Maximum No­Load Power [W]

0 Less than the II mark 30 3

1 Meets the II mark 56 0.75

2 Meets the IV mark 64 0.5

3 Meets the V mark 72 0.3

Table 4.32 Light Usage of 4.8 W EPS for Power Tools

­

EPS

Mode Application

State Annual Usage (hours/year) Reasoning

Active Active Charging 36 The battery is charged once a month and takes 3 hours to fully charge.

Maintenance 252 Each time the battery is charged, it is left in the charger for 21 hours after being fully charged.

No­Battery 0 The battery charger and EPS are unplugged and stowed when not in use.

No Load Disconnected

from EPS 0 The battery charger and EPS are unplugged and stowed when not in use.

Unplugged

— 8,472 The battery charger and EPS are unplugged and stowed when not in use.

4­15Table 4.33 Heavy Usage of 4.8W EPS for Power Tools

­

EPS

Mode Application

State Annual Usage (hours/year) Reasoning

Active Active Charging 312 The battery is charged twice a week and takes 3 hours to fully charge.

Maintenance 7,616 For each charge cycle, the battery is left in the charger for 22 hours (total 66 hours). In addition, the battery is left in the charger in general, except when in use. (An additional time of 24 hours a year is added to this time as a correcting factor.)

No­Battery 416 The power tool is used twice a week, for 8 hours each time. Fifty percent of power tools come with cradle chargers. Thus half the time is allocated to the no­battery state. The remaining half is allocated to

no­load mode.

No Load Disconnected

from EPS 416 (see reasoning above)

Unplugged

— 0 The battery charger and EPS are never

disconnected from mains.

Table 4.34 Weighted­Average Usage and Output Power of 4.8 W EPS for Power Tools

­

EPS Application Annual Usage (hours/year) EPS Output

Power

[W] Mode State Light User
(75%) Heavy User
(25%) WeightedAverage

User

Active Active Charging 36 312 105 3.84

Maintenance 252 7,616 2,093 1.68

No­Battery 0 416 104 1

No Load Disconnected

from EPS 0 416 104 0

Unplugged

— 8,472 0 6,354 0

4­16Table 4.35 Unit Energy Consumption for 4.8 W EPS for Power Tools

­

CSL Unit Energy Consumption (kWh/year) EPS Active Mode (Application State) EPS NoLoad Mode Total Active Charging Maintenance No­Battery

0 0.67 5.83 0.20 0.19 6.90

1 0.32 2.79 0.10 0.08 3.28

2 0.23 1.97 0.07 0.05 2.31

3 0.16 1.37 0.05 0.03 1.60

4.4 EPS Power Consumption by Modes of Operation

In the NOPR, DOE defined power consumption as a function of three factors: the nameplate output power of the EPS, the efficiency of the EPS, and the consumption of the EPS

when in no load mode.

Note: When discussing power consumption, DOE is referring to the power loss associated with the use of the EPS. That is, the power “consumed” by the EPS is the difference between input and output power.

No­load mode power (P NL ) is the measured power drawn by the EPS from mains while in no­load mode. Because the EPS is disconnected from the application, all of the power drawn from mains is consumed by the EPS. For each candidate standard level, an associated no­load mode power is given. No­load mode power levels for each of the representative units are discussed in the engineering analysis section of this notice.

EPS power consumption while in active mode varies as the power requirements of its load vary. Nameplate output power is the highest output power that an EPS is capable of delivering. In the case of high power EPSs used for amateur radio equipment, nameplate output power is also described as instantaneous, intermittent, peak or surge power. Nameplate output power is the product of nameplate output voltage and nameplate output current, which are defined in the EPS test procedure. Nameplate output voltage is the voltage output of the EPS as specified by the manufacturer on the label on the housing of the EPS. (10 CFR 430, Appendix Z) Nameplate output current is the current output of the EPS as specified by the manufacturer on the label on the housing of the EPS. (10 CFR 430, Appendix Z)

DOE used two different approaches to calculating EPS power consumption in active mode—one for those application states requiring 25 percent or more of the EPS’s nameplate output power and another for those application states requiring less than 25 percent of the EPS’s nameplate output power.

The approach for application states requiring 25 percent or more of the EPS’s nameplate output power is straightforward. The EPS test procedure measures the active mode efficiency (η) of the EPS at 25, 50, 75, and 100 percent of nameplate output power or current. The active mode efficiency of the EPS is then defined as the average of these 4 values (points 2, 3, 4, and 5 in Figure 4.1) As such, power consumption is

4­17P Con = P In – P Out

where

P Out = P In x η

or

P In = P Out x (1/η)

Therefore,

P Con = P Out x (1/η – 1)

For example, an EPS delivering an output power of 10 watts at 75 percent efficiency

would consume:

P Con = 10 W x (1/0.75 – 1) = 3.33 W

Active mode efficiency (η) levels for each of the representative units are discussed in the engineering analysis section of this notice.

The approach for application states requiring less than 25 percent of the EPS’s nameplate output power blends measures of the EPS’s active­mode efficiency and no­load mode power consumption. Most applications have some application states that require an output power below 25 percent of nameplate. Additionally, many applications spend a significant portion of time in these states. However, at these low power levels the efficiency of an EPS is relatively low (see Figure 4.1

. ). Because of this, DOE did not use the active­mode efficiency metric alone.

4­185**Input Power**  **X**

4

**X**

3

**X**

2

**X**

**X**

**0% 25%**  **50% 75%**  **100%**

**Output Power**  **(Percent of**  **Nameplate)**

Figure 4.1 Relationship Between EPS Input Power and Output Power at Five Loading Points as Measured by the Test Procedure

Instead, DOE calculated energy consumption in this region by interpolating between two known points: (1) the no load power consumption and (2) the active mode consumption at 25 percent of nameplate output power. These are points 1 and 2 in Figure 4.1. At an output power of 25 percent, the energy consumed by the EPS is: P Consumed = P Out x (1/η – 1). At an output power of 0 percent (no load mode), the energy consumed by the EPS is: P Consumed = P NL

. Given these two known values, DOE assumed that the energy consumed by an EPS at an output power between 0 and 25 percent of nameplate output power must fall on a curve between these two points.

DOE approximated this curve with a straight line between points 1 and 2, which can be described by the following equation relating input power to output power:

P In = m x P Out + B

Where B is the y­axis intercept, or P NL , and m is the slope, or:

m = ∆y/∆x

m = [(25% x [P Nameplate / η]) – P NL ] / [(25% x P Nameplate ) – 0]

Thus, for output power levels below 25 percent nameplate output power, the input power of the

EPS is: 1

**(0W, P**  **NL )** 

4­19P In = {[(25% x [P Nameplate / η]) – P NL ] / [25% x P Nameplate ]} x P Out + P NL

Since

P Consumed = P In – P Out

Then

P Consumed = {[(25% x [P Nameplate / η]) – P NL ] / [25% x P Nameplate ]} x P Out + P NL – P Out

Or

P Consumed = ({[(25% x [P Nameplate / η]) – P NL ] / [25% x P Nameplate ]}­1) x P Out + P NL

DOE seeks comment on its methodology for calculating energy consumption at output power levels below 25 percent of nameplate output power.

4.4.1 EPS Energy Use

4.4.1.1 EPS Energy Consumption

Unlike most other consumer products using electricity, the energy consumption of an EPS cannot always be measured as the energy drawn from mains, since the function of an EPS is to deliver power for the operation of other end­use applications. DOE calculated the energy consumption of an EPS (E CON ) as the difference between energy drawn from mains (E IN ) and the energy supplied to the end­use application (E OUT ), or:

E CON = E IN ­ E OUT

Since energy measures power (P) multiplied by a duration of time (T), the following equation is used:

P CON * T = (P IN – P OUT ) * T

Factoring in the different EPS modes we get:

P CON * T TOTAL = ­ P CON­Active * T Active + ­ P CON­No­Load * T No­Load

­

Further factoring in application states, we get:

P CON * T TOTAL = ­ P CON­Active1 * T Active1 + ­ P CON­Active2 * T Active2 + ­ P CON­Active3 * T Active3 + ­

... P CON­No­Load * T No­Load

4­20Thus, to calculate the energy consumption of an EPS, DOE then combined the time and power consumption values (from shown in the usage profiles) with power consumption values.

4­21CHAPTER 5 LIFE­CYCLE COST AND PAYBACK PERIOD ANALYSIS

5.1 Life­Cycle Cost and Payback Period Analysis

5.1.1 Introduction
This chapter of Technical Support Document (TSD) contains information that supports and expands on the Life­Cycle Cost and Payback Period Analysis section of the Notice of Proposed Rulemaking (NOPR). Specifically, this section describes the methodology that the Department of Energy (DOE) used to analyze the economic impacts of possible energy efficiency standards on individual consumers. DOE performed this analysis on the same representative units evaluated in the engineering analysis section of the NOPR. The effects of standards on individual consumers include a change in operating expenses (usually decreased) and a change in purchase price (usually increased). This section describes the two metrics DOE used in the consumer analysis to determine the effect of potential standards on individual

consumers:

• Life­cycle cost (LCC) is the total consumer expense over the lifetime of an appliance,

including the up­front cost (the total price paid by a consumer before the appliance can be

operated) and all operating costs (including energy expenditures). DOE discounts future

operating costs to the time of purchase.

• Payback period (PBP) represents the number of years it would take the customer to

recover the assumed higher purchase price of more energy­efficient equipment through

decreased operating expenses. a Sometimes more energy­efficient equipment can have a

lower purchase price than the less energy­efficient equipment that it substitutes for; in

this case, the consumer realizes an immediate financial benefit and thus there is no

payback period.

a DOE computes a “simple PBP,” where only the first year of operating costs are used. Thus, operating costs are not

discounted. See section 5.1.4.1 for further information.

5­1EPSs are unique appliances because they are always used in conjunction with other products of interest, as shown in Figure 5.1. Most EPSs are packaged with particular products; thus, consumers usually do not buy EPSs directly. Instead, for example, consumers obtain EPSs for video game systems when buying the video game systems themselves. Thus, although the LCC and PBP analysis uses the consumer purchase prices of EPSs, in reality those prices are a “hidden” portion of the prices that consumers pay for the products of interest.

Figure 5.1 Usage of External Power Supplies

Because EPSs are used in conjunction with other products, their energy consumption is directly related to the usage of those other products as well as the technologies that the EPSs utilize. The energy consumption of the analyzed Non­Class A EPSs is assessed in further detail in the energy use and end­use load characterization section of the NOPR. The technologies of the analyzed Non­Class A EPSs are assessed further in the technology assessment section of the

NOPR.

5.1.2 Overview of LCC and PBP Inputs
For the Non­Class A EPS determination analysis, DOE categorized inputs to the LCC and PBP analysis as follows: (1) inputs for establishing the consumer purchase price of an EPS, and (2) inputs for calculating the operating cost . In this analysis, all dollar amounts are in 2008

dollars.

The primary inputs for establishing the consumer purchase price are:

• efficiency­related materials cost (ERMC) in 2008 dollars

, which is based on the bill of materials cost of the efficiency­related components of the EPS; and

markups as scaling factors applied to the manufacturer production cost to create the final efficiency­related consumer purchase price. The primary inputs for calculating the operating cost

are:

• unit energy consumption in kilowatt­hours per year (kWh/year), which is the annual site energy use of the EPS;

• electricity prices in 2008 dollars, which are the prices paid by consumers for electricity;

• an electricity price trend , which is applied to the 2008 electricity price to forecast electricity prices into the future;

5­2• start year , which is the year in which the EPS and its associated product are purchased (for the LCC and PBP analysis, DOE uses 2013 as the start year for all products);

• lifetime , which is the age at which the EPS and its associated product are retired from service (lifetimes vary by product); and

• discount rate , which is the rate at which DOE discounted future expenditures to establish their values in the start year. Note that future expenditures are discounted for the LCC calculation and not the PBP calculation, as DOE uses a simple PBP. See section 5.1.4 for further information.

Figure 5.2 presents the flow diagram for the draft determination analysis LCC developed by DOE. The figure depicts LCC inputs in yellow boxes, interim calculated values in green boxes, and final output values ( i.e. , LCC and PBP results) in aqua boxes. Table 5.1 lists the draft inputs DOE developed for the determination analysis.

Figure 5.2 Flow Diagram of Inputs for the Determination of LCC and PBP

EfficiencyRelated

Materials Cost

Markups EfficiencyRelated

Consumer

Purchase

Price

Unit Energy Consumption

Electricity Prices Annual Energy Cost

Lifetime

Discount

Rate Electricity

Price Trend

Lifetime Operating Expense Payback

Period Life­Cycle

Cost

Start Year

5­3Table 5.1 Draft Inputs to the Life­Cycle Cost and Payback Period Analysis

­

Input Description Average or Typical

Value Sources

EfficiencyRelated

Materials Cost The bill of materials cost, in 2008 dollars, of the efficiency­related components

of the EPS. $2.95 EPS testing and teardowns, manufacturer interviews, and distributor catalogues.

Markups The factor increase applied to the production cost to arrive at the consumer purchase price including the OEM markup,

the retailer and distributor markups, and sales tax. 3.6 Discussed in the NOPR.

Unit Energy Consumption The annual on­site electricity consumption of an EPS in kWh per year. 24.1 kWh/year Discussed in the NOPR.

Electricity Prices The national residential sector average price in 2008 dollars per kilowatt­hour ($/kWh). $0.118/kWh Residential national average electricity price

based on data from the Energy Information Administration (EIA) year 2006 Form 861 b and

the EIA AEO2009 (Annual Energy Outlook, Year 2009), c both

discussed in section

5.1.3.2.

Electricity Price

Trend The projected changes in the price of electricity over the analysis period. 11 percent increase by

2030 EIA AEO2009 residential reference case electricity price trend, discussed in

section 5.1.3.2.

b Department of Energy. Energy Information Administration. Table 8. Electricity Supply, Disposition, Prices, and

Emissions . Report #:DOE/EIA­0383(2009) Early Release. December 2008. http://www.eia.doe.gov/oiaf/aeo/excel/aeotab_8.xls

.

c Department of Energy. Energy Information Administration. Form 861 . 2006. http://www.eia.doe.gov/cneaf/electricity/page/eia861.html

.

5­4Input Description Average or Typical

Value Sources

Lifetime The total number of years in

use after which the consumer

retires the EPS and associated product from service. This may be before the EPS

reaches the end of its useful

life. 6 years Discussed in the NOPR.

Discount Rate The discount rate DOE estimates to be representative of EPS consumers, used to

establish the value of future expenditures in the start year of analysis. 5.6 percent Weighted average of residential financing methods, discussed in

section 5.1.3.3.

Start Year The year in which the EPS is purchased by the consumer. 2013 The potential effective date of an energy

conservation standard for Non­Class A EPSs,

discussed in section

5.1.3.3.

5.1.3 Life­Cycle Cost Inputs
The life­cycle cost of an EPS consists of the consumer purchase price plus all of the operating costs over the lifetime of the EPS, as shown in Eq. 5.10. When calculating the LCC, DOE discounted all future operating costs to the start year. See section 0 for further details on discounting.

N LCC = PRICE + 

# ∑ OC

t

t Eq. 5.10 

## ( 1 + r 

## )

where: LCC is the life­cycle cost in 2008 dollars,

PRICE is the efficiency­related consumer purchase price in 2008 dollars, t = 1



## ∑ N is the sum over the EPS lifetime, from year 1 to year N

,

t = 1

N is the lifetime of EPS in years,

­

OC t is the operating cost in 2008 dollars in year t

, ­

r is the discount rate, and

­

5­5t is the year for which operating cost is being determined (where the start year of the analysis is year 1).

The following sections discuss efficiency­related consumer purchase price, operating cost, EPS lifetime, discount rate, and start year.

5.1.3.1 Efficiency­Related Consumer Purchase Price Inputs

The consumer purchase price for an EPS is based on how the consumer purchases the EPS. DOE defined markups for converting manufacturer production costs into consumer purchase prices. The inputs for determining the consumer purchase price are listed below.

• Efficiency­Related Materials Cost

• Overall Markup

DOE calculated the consumer purchase price for all EPSs based on Eq. 5.11:

PRICE = ERMC × MARKUP Eq. 5.11

where: PRICE is the efficiency­related consumer purchase price in 2008 dollars,

ERMC is the efficiency­related materials cost in 2008 dollars, and

MARKUP is the overall markup factor (product of original equipment manufacturer (OEM) markup, retailer or distributor markup, and sales tax).

In the LCC analyses in several other DOE rulemakings, d the up­front cost of an appliance includes a purchase price for the appliance as well as a price for its installation. EPS installation, however, typically entails a consumer simply unpacking the EPS from the box it was sold in and connecting it to mains power and its associated product. Because the cost of this “installation” is not quantifiable in dollar terms, DOE did not include it in the LCC for Non­Class A EPSs. Furthermore, recall that most EPSs are purchased in conjunction with the consumer products that they power; thus, consumers usually do not pay the consumer purchase price of the EPS directly. For this determination analysis, DOE has also chosen to focus specifically on efficiency­related prices, as the efficiency­related prices depend directly on the different technologies

manufacturers would use to reach various candidate standard levels.

DOE researched information about each of the input variables that it used to calculate the consumer purchase price. DOE developed its manufacturer production costs through manufacturer interviews, EPS testing and teardowns, and research of distributor catalogues. Information from these sources was used to develop the bill of materials (BOM) cost, direct overhead costs, and labor costs that comprise the manufacturer production cost.

d For examples, see the Energy Conservation Standards for Commercial Ice­Cream Freezers; Self­Contained Commercial Refrigerators, Commercial Freezers, etc., (74FR1092); the Packaged Terminal Air Conditioner and Packaged Terminal Heat Pump Energy Conservation Standards (73FR58772); and the Energy Conservation Standards for Residential Furnaces and Boilers (72FR65136).

5­6Markups represent how the price of an EPS increases as it travels along the distribution chain from manufacturer to consumer. Generally, an OEM markup is first applied to create the EPS manufacturer selling price to a distributor or retailer. The retailer or distributor then applies another markup along with sales tax to create the consumer purchase price. Thus, the total markup factor is the product of the OEM markup, the distributor/retailer markup, and the sales tax. DOE developed OEM and retailer/distributor markups based on manufacturer interviews. The sales tax of 6.8 percent was computed based on a population­weighted average in 13 geographic regions and large states.

5.1.3.2 Operating Cost Inputs

The operating cost of the EPS consists of the cost of electricity associated with the consumer’s usage of the EPS. The inputs to the operating cost calculation are as follows:

• Unit Energy Consumption (UEC)

• Electricity Prices

• Electricity Price Trend

For every analysis year in the Non­Class A EPS LCC analysis, DOE computed the operating cost as shown in Eq. 5.12:

OC

t = UEC × EP

t Eq. 5 .12

where: OC t is the cost associated with operating the EPS in year t in 2008 dollars,

UEC is the unit energy consumption of the EPS in kWh per year,

EP t is the electricity price in year t in 2008 dollars,

t is the year for which operating cost is being determined (where the start year of the analysis is year 1).

Although operating costs for several other DOE rules have encompassed repair and maintenance costs, e DOE did not consider those costs (which are usually associated with larger products and appliances) in the draft LCC for the determination analysis of Non­Class A EPSs. In making this decision, DOE recognized that the service life of an EPS typically exceeds that of the consumer product with which it is designed to operate. Thus, a consumer would not incur repair or maintenance costs for an EPS. Also, if an EPS did fail, DOE expects that consumers would typically discard the EPS and purchase a replacement.

e For examples, see the Energy Conservation Standards for Commercial Ice­Cream Freezers; Self­Contained Commercial Refrigerators, Commercial Freezers, etc., (74FR1092); the Packaged Terminal Air Conditioner and Packaged Terminal Heat Pump Energy Conservation Standards (73FR58772); and the Energy Conservation Standards for Residential Furnaces and Boilers (72FR65136).

5­7The unit energy consumption is the site energy use associated with operating the EPS. The UEC varies with the product efficiency and the number of hours that the product is used. Generally, the unit energy consumptions associated with candidate standard level EPSs ( i.e.

, EPSs with efficiencies greater than the baseline EPSs) are less than the UECs associated with baseline EPSs. For the LCC and PBP analysis described in this section, UECs representing nominal usage were developed and used.

Electricity prices are the prices paid by consumers for electricity during the years of analysis. Multiplying the UEC of a particular EPS by the electricity price for a given year yields the EPS’s operating cost for that year. DOE developed residential sector future electricity prices using the residential sector national average electricity price in EIA’s most recent (year 2006) Form 861 along with the residential sector national average electricity price trend from EIA’s Annual Energy Outlook year 2009 reference case. Though the AEO2009 contains actual residential sector national average electricity prices for 2008 (note that they are in 2007 dollars), DOE uses EIA Form 861 instead for the electricity price because the form contains actual sales data from electric utilities across the country and thus is of a higher resolution.

DOE’s LCC and PBP analysis, however, is in 2008 dollars and depends on the most upto­date electricity price information. Because the EIA Form 861 electricity price is in 2006 dollars, DOE first converted the price to 2008 dollars using annual average consumer price indices (CPIs) from the U.S. Bureau of Labor Statistics. f To do this, DOE multiplied the 2006 electricity price by the ratio of the 2008 CPI to the 2006 CPI, as shown in Table 5.2, to produce the 2006 electricity price in 2008 dollars. Next, DOE projected the 2006 electricity price to 2008 by multiplying the price by the ratio of the AEO2009 residential 2008 electricity price to the

AEO2009 residential 2006 electricity price, as shown in Table 5.3. DOE thus arrived at the 2008 residential sector national average initial electricity price of $0.121/kWh in 2008 dollars. An equation detailing the creation of the 2008 initial electricity price is shown in Eq. 5.13.

 CPI   AEO 

2008 2006 2008 2008 IEP 2008 = EIA 2006 ×    ×   Eq. 5.13     CPI 2006   AEO 2006 

where: IEP 2008 is the 2008 initial electricity price in 2008 dollars, 2008

EIA 2006 is the EIA Form 861 2006 electricity price in 2006 dollars, 2006

is the 2008 consumer price index, CPI 2008

CPI 2006 is the 2006 consumer price index,

AEO 2008 is the AEO2009 2008 electricity price in 2007 dollars, and

f Bureau of Labor Statistics. Table Containing History of CPI­U U.S. All Items Indexes and Annual Percent Changes From 1913 to Present . 2009. ftp://ftp.bls.gov/pub/special.requests/cpi/cpiai.txt

.

5­8AEO 2006 is the AEO2009 2006 electricity price in 2007 dollars.

Table 5.2 Annual Average Consumer Price Indices

Year Annual Average Consumer Price

Index

2006 201.6

2008 215.303

Ratio 1.1

Table 5.3 AEO2009 Electricity Prices

­

AEO2009 Price

Year 2007$/kWh

2006 0.1065

2008 0.1103

Ratio 1.0363

To develop electricity prices for all of the years in the LCC analysis, DOE normalized the

AEO2009 residential sector electricity prices using the AEO2009 electricity price for the year 2008 to create the electricity price trend. The electricity price trend is shown in Figure 5.3. The start year of analysis (2013) and the associated scaling factor are indicated in the figure. The

normalized AEO2009 price trend was then used as a set of scaling factors to produce the electricity price for each of the analysis years, as shown in Eq. 5.14. DOE used an electricity price of $0.118/kWh in the start year of 2013, based on the scaling of the initial electricity price ($0.121/kWh) by the 2013 scaling factor 0.98.

EP = IEP 2008 × AEOTREND Eq. 5 .14

t 2008 t

where: EP

t is the electricity price in year t in 2008 dollars,

IEP 2008 is the 2008 initial electricity price in 2008 dollars, 2008

AEOTREND

t is the scaling factor for year t based on the electricity price trend,

and

t is the year for which electricity price is being determined (where the start year of the analysis is year 1).

5­9Figure 5.3 Normalized AEO2009 Residential Sector Reference Case Electricity Price

TrendScalingRelativeto2008 **1.15**

**1.10**

**1.05**

**1.00**

**0.95**

**0.90** Start Year:
2013 Scaling:
0.98

**2005 2010**  **2015 2020**  **2025 2030**  **2035**

**Year**

5.1.3.3 Other Inputs to the LCC Analysis

To compute the life­cycle cost of an EPS, the operating costs of the EPS must be discounted to the start year of the analysis period. DOE assumes that money consumers spend in the future is worth less to them than money they spend today. For example, a dollar obtained today may only be worth 90 cents to the consumer a year from now. Thus, discounting reflects the current value of money spent or saved in the future. The inputs that DOE used to perform the discounting for the LCC and PBP analysis are as follows:

• EPS Lifetime

• Discount Rate

• Start Year

The EPS lifetime is discussed in the NOPR. The discount rate and start year are described

in the sections below.

START YEAR AND EFFECTIVE DATE OF STANDARD

The effective date is the date when a new standard becomes operative, i.e., the date by which EPS manufacturers must manufacture products that comply with the standard. For the purpose of this analysis, DOE has assumed that a Non­Class A EPS efficiency standard would be published in conjunction with an efficiency standard for Class A EPSs. Publication of a final standard for Class A EPSs is scheduled for July of 2011 (42 U.S.C. 6295(u)(6)(D)(I)), and the effective date of this standard is July 1, 2013 (42 U.S.C. 6295(u)(6)(D)(II)). DOE assumes that all consumers will purchase an EPS in the year of the effective date of standard. Thus, the start year for the LCC analysis is 2013.

5­10DISCOUNT RATE

The calculation of the LCC required DOE to use a discount rate to determine the present value (at the start year of the LCC analysis) of the money the consumer would spend to operate the EPSs over their lifetime. Because consumers can use a variety of financial means to purchase an EPS, the discount rate should equal the average cost of capital to the consumer. DOE assumed these financial means, listed in Table 5.4, to be similar to the ones residential consumers use when purchasing and financing replacement appliances for the home. DOE’s approach involved identifying all possible debt or asset classes those consumers might use to purchase replacement equipment, including household assets that might be affected indirectly.

DOE estimated the shares of the various debt and equity classes in the typical U.S. household portfolio using the Federal Reserve’s Survey of Consumer Finances ( SCF ) g data for 1989, 1992, 1995, 1998, 2001, and 2004. DOE also used SCF data to determine rates of return for each class. DOE then calculated an average rate weighted by the share of each class of debt or equity, equal to 5.6 percent, to represent a household discount rate, shown in Table 5.4.

Table 5.4 Shares and Interest or Return Rates Used for Household Debt and Equity Types

Type Average Share of

Household Debt Plus Equity* [%] Mean Real

Effective Discount Rate** [%]

Home Equity Loans 3.6 4.0

Credit Cards 2.0 11.0

Other Installment Loans 1.7 6.0

Other Residential Loans 4.9 4.6

Other Line of Credit 0.5 8.7

Checking Accounts 4.5 0.0

Savings and Money Market Accounts 15.7 2.3

Certificates of Deposit 9.0 2.4

Savings Bonds 1.5 3.5

Bonds 10.0 4.2

Stocks 29.1 8.8

Mutual Funds 17.5 7.0

Total: 100 Weighted Average: 5.6

* Not including primary mortgage or retirement accounts.

­ ** Adjusted for inflation and, for home equity loans, loan interest tax deduction.

­

g The Federal Reserve Board. Survey of Consumer Finances

. http://www.federalreserve.gov/PUBS/oss/oss2/scfindex.html

.

5­115.1.4 Payback Period Inputs

5.1.4.1 Definition and Inputs

The PBP is the amount of time it takes the consumer to recover the assumed higher purchase cost of a more energy­efficient EPS as a result of lower operating costs, in comparison with a specific less energy­efficient EPS. In general, a PBP that is longer than the lifetime of the EPS is an indicator that a consumer purchasing that EPS will realize negative LCC savings. This is because the increased purchase price is too great for the consumer to recover in operating cost savings before the EPS and its associated product are retired from use.

Numerically, the PBP is the ratio of the increase in purchase cost (i.e., from a less efficient design to a more efficient design) to the decrease in first year operating costs. This type of calculation is known as a “simple” PBP, because it does not take into account changes in operating cost over time or the time value of money. That is, the calculation is done at an effective discount rate of zero percent. The PBP uses the same inputs as the LCC calculation described in section 5.1.3, except that electricity price trends are not required. The required electricity cost is only for the year in which DOE has a new energy conservation standard for Non­Class A EPS to take effect—in this case, 2013. Thus, the electricity price DOE uses in the PBP calculation for electricity cost is the price projected for 2013, expressed in 2008 dollars. PBPs are expressed in years.

The equation for PBP is:

Δ PRICE k → L PBP k → L = Eq. 5.15 Δ OC 1, k → L

where: PBP k → L is the payback period (in years) that a consumer replacing an EPS at

CSL k with an EPS at CSL L would experience,

PRICE

→ is the difference in efficiency­related consumer purchase price Δ k L between an EPS at CSL L and an EPS at CSL k , and

OC is the difference in the first year of operating costs between an EPS at 1, k → L CSL L and an EPS at CSL k

.

PBPs greater than the life of the EPS generally indicate that the increased efficiencyrelated consumer purchase price of the more efficient product is not recovered in reduced operating costs over the lifetime of that product. It is also possible for a more efficient EPS to have a lower efficiency­related consumer purchase price than the baseline EPS. In this case, the consumer would immediately realize financial benefits and there would be no PBP.

Note that because the simple PBP does not take into account changes in operating cost over time or the time value of money, there are some situations where consumers will realize negative LCC savings when purchasing an EPS with a simple PBP that is slightly less than the EPS lifetime. Alternatively, there are some situations where consumers will realize positive LCC

5­12savings when purchasing an EPS with a simple PBP that is slightly greater than the EPS lifetime (e.g. when electricity prices increase over the lifetime). As done for several other DOE rulemakings, h DOE uses the simple PBP to express to the public the approximate amount of time that a consumer will have to operate an EPS to recover the increased purchase cost through savings in electricity expenditures. When assessing the economic benefits of a standard, DOE prefers to use the LCC savings due to its higher fidelity (including discounting and the change in electricity prices over time).

h For examples, see the Energy Conservation Standards for Residential Furnaces and Boilers (72FR65136) and the Packaged Terminal Air Conditioner and Packaged Terminal Heat Pump Energy Conservation Standards (73FR58772).

5­13CHAPTER 6 NATIONAL IMPACT ANALYSIS

6.1 Introduction

This chapter provides supplemental information on the methodology DOE used in its determination analysis to calculate the National Energy Savings (NES) and the Net Present Value (NPV) as part of the National Impact Analysis (NIA) for non­Class A external power supplies (EPSs).

The calculations for NES and NPV were implemented in two Microsoft ® Excel

workbooks that can be downloaded from the EERE web site. a The workbooks are identical in design. The first workbook, titled “NCAEPS Determination NOPR NIA PartA.xls” contains the NES and NPV calculations for four types of EPS:

A) Multiple voltage EPSs used for multifunction devices B) Multiple voltage EPSs used for Xbox 360 video game consoles C) High power EPSs D) EPSs used to power medical devices The second workbook, titled “NCAEPS Determination NOPR NIA PartB.xls” contains the NES

and NPV calculations for two EPSs:

A) EPSs used for battery chargers for cordless handheld vacuums

­ B) EPSs used for battery chargers for power tools

­

This document is a guide to these two workbooks. Section 6.3 provides an overview of the layout of the workbooks. Section 6.4 contains a step­by­step walkthrough of the calculation of NES and NPV, using as an example the multiple­voltage EPSs used with Xbox 360 video game consoles. References in the walkthrough to specific cells refer to cell in the workbook with

the filename: “NCAEPS Determination NOPR NIA PartA.xls”

The analyses referred to collectively as the national impact analysis are depicted graphically in Figure III.19 of the NCA EPS NOPR. The national impact analysis consists of

four calculations:

• National inventory , which measures the total number of units affected by the standard;

• Unit energy savings (UES), which measures the change in unit energy consumption due to the impact of the standard;

a Available for download from the EERE website: http://www.eere.energy.gov/buildings/appliance_standards/residential/battery_external.html

6­1• National energy savings (NES), which combines unit energy savings and the national inventory to obtain the aggregate energy savings generated by the standard; and

• Net present value , which calculates the net present savings and costs of a standard by comparing the present value of energy savings from national energy savings with the present value of the increased consumer purchase costs associated with the standard.

6.2 National Inventory

DOE used a national inventory model to represent the installed base of EPSs that a standard would affect. Because the EPSs remain in use for several years, the national inventory represents the stock of EPSs in service for any given year of the analysis period. It is important to track the date of manufacture, or vintage, of products in the installed base because the energy efficiency and price of products sold changes over time. DOE used three inputs to calculate the national inventory for the determination analysis: start­year shipments, shipment growth rates, and product lifetimes. Values for these three inputs are given in section Section III of the NCA

EPS NOPR.

Table 6.1 shows how the national inventory model tracks the number of products by vintage in the installed base for a given year. In 2013, 100 units are sold and enter the installed base. In this example, the product has an average lifetime of 3 years. Therefore, the units sold in 2013 are retired at the end of 2015, and removed from the inventory for 2016. The shipment growth rate is 5 percent, so 105 units are sold in 2014. These units are added to the 100 units that remain in the installed base from the year before. In 2014, 205 units are in the installed base. This process of adding to and subtracting from the installed base is carried forward throughout the analysis period. Figure 6.1 shows the flow of the calculations.

Table 6.1 Example National Inventory Table

Vintage Year of Analysis

2013 2014 2015 2016 2017 2018 2019

2013 100 100 100

­ ­ ­ ­ 2014

­ 105 105 105

­ ­ ­ 2015

­ ­ 110 110 110

­ ­ 2016

­ ­ ­ 116 116 116

­ 2017

­ ­ ­ ­ 122 122 122

2018

­ ­ ­ ­ ­ 128 128

2019

­ ­ ­ ­ ­ ­ 134

Total 100 205 315 331 348 366 384

6­2Electricity Price
National Energy

­ Savings ($)

­

Discount Rate Net Present Value

Figure 6.1 Flow Chart Showing the Calculation of National Energy Savings and Net

Present Value

6.3 Layout of the NES­NPV Workbook

The NES­NPV workbook contains 10 worksheets (tabs) as follows:

Cover

This worksheet gives a brief description of the functions of the tabs within the workbook.

1 Controls

This worksheet contains the controls and outputs of the NES­NPV calculations.

Input controls are on the left side of the worksheet, and highlighted in light yellow. The controls are arranged, from top to bottom, in the following manner:

B5 to B8 Market Growth Rate

B12 to B15 Lifetime (Not used in this analysis)

B19 to B22 Base Case Standard Level

B26 to B29 Standard Case Standard Level Unit Energy Savings

National Inventory National Energy

­ Savings (kWh)

­

National

­ Improvement Costs

­ Unit Improvement

­ Cost

­

6­3C31 Efficiency Progression

­

C33 Market Response to Standard (Not used in this analysis)�

C35 Electricity Price Case (Not used in this analysis)�

B39 Electricity Price Ratio (Not used in this analysis)�

C42 Discount Rate

­

Outputs for NES and NPV are on the right side of the worksheet and are arranged as follows:

G4 to G8 National Energy Savings in kWh

H4 to H8 National Energy Savings in Quadrillion BTU

I4 to I8 National Energy Savings in 2008$

J4 to J8 Total Costs in 2008$

K4 to K8 Net Present Value in 2008$

In addition, 3 output figures give the annual results as follows:

Figure 1 National Energy Savings in 2008$

Figure 2 Total Costs in 2008$

Figure 3 Net Present Value in 2008$

2 Inputs

This worksheet contains all the input values used in the calculations. The inputs are divided into four categories as follows:

Rows 9 to 84 Constant Values and Structural Values

Rows 85 to 195 Market and Usage Values

Rows 196 to 389 Variable Values

Rows 390 to 411 Model Reference Values

6­43 NES

This worksheet contains the National Energy Savings calculations. In this worksheet, results are displayed in units of kWh.

Columns G to AT Results/Values for each year from 2008 to 2047

Column AU Total results for all years

Rows 1 to 6 Summary Results

Rows 41 to 45 Results for EPS Type A

Rows 80 to 84 Results for EPS Type B

Rows 119 to 123 Results for EPS Type C

Rows 158 to 162 Results for EPS Type D

4 NPV

This worksheet contains the Net Present Value calculations.

Columns G to AT Results/Values for each year from 2008 to 2047

Column AU Total results for all years

Rows 2 to 6 NES in kWh (copied from 3 NES )

Row 8 Electricity Price ($/kWh)

Rows 10 to 14 NES in $ (non­discounted)

Rows 16 to 20 Incremental Installed Costs in $ (non­discounted)

Row 22 Discount Multiplier

Rows 24 to 28 NES in 2008$ (discounted)

Rows 30 to 34 Incremental Installed Costs in 2008$ (discounted)

Rows 36 to 40 NPV in 2008$ (discounted)

Rows 75 to 79 Incremental Installed Costs for EPS Type A

Rows 114 to 118 Incremental Installed Costs for EPS Type B

6­5Rows 153 to 187 Incremental Installed Costs for EPS Type C

­

Rows 192 to 196 Incremental Installed Costs for EPS Type D

­

5 Inventory

This worksheet contains the rolling inventory for each EPS type.

Columns D to AQ Inventory for each year from 2008 to 2047

Column AS Shipments for each year

Rows 4 to 46 Inventory for EPS Type A

Rows 50 to 92 Inventory for EPS Type B

Rows 96 to 138 Inventory for EPS Type C

Rows 142 to 184 Inventory for EPS Type D

6, 7, 8, 9 Distribution Tables

This section addresses the following worksheets:

6 MV­MFD EPS Dist Tables

­

7 MV­Xbox EPS Dist Tables

­

8 High­Power EPS Dist Tables

­

9 MED EPS Dist Tables

­

These worksheets contain the distribution of shipments by efficiency for each year. These worksheets also contain the calculations for unit energy savings (UES) and incremental installed

costs.

Columns C to O display the scenario where efficiency does not progress in the absence of a standard. Because the distribution of shipments by efficiency level in this scenario remains static (unchanging), this walkthrough will hereafter refer to this scenario as the static scenario. Within this group of columns:

• Columns D to G display the distribution of efficiency by year.

• Column L displays the weighted­average unit energy consumption

• Column M displays the unit energy savings

6­6• Column N displays the unit cost

• Column O displays the incremental unit cost (as compared the unit cost at CSL0)

Columns AE to AQ display the scenario where efficiency does progress even without a standard. Because the distribution of shipments by efficiency level is dynamic (changing), this walkthrough will hereafter refer to this scenario as the dynamic scenario. Within this group of

columns:

• Columns AF to AI display the distribution of efficiency by year.

• Column AN displays the weighted­average unit energy consumption

• Column AO displays the unit energy savings

• Column AP displays unit cost

• Column AQ displays the incremental unit cost (as compared the unit cost at CSL0)

Starting at the top, and moving down, forecasts are outlined for each CSL, with CSL 0 (Rows 15 to 59) at the top, CSL 1 (Rows 61 to 105) and CSL 2 (Rows 107 to 151) in the middle, and CSL 3 (Rows 153 to 197) at the bottom.

6.4 NES­NPV Calculation Walkthrough

This section presents an example walkthrough for the calculation of NES and NPV for the EPSs used to power Xbox 360 video game consoles. For this walkthrough, DOE will conduct the calculations for a dynamic scenario, and with a standard set at CSL 1. For the calculation of NPV, DOE will use a 3 percent discount rate. When referring to specific cells in the walkthrough, DOE will use the following format:

Tab Name ­ Cell

6.4.1 Calculation of Unit Energy Savings

For each year in the analysis period:

Step 1: Weighted Average Unit Energy Consumption (UEC) in the Base Case

Starting in 2013 we take the base case distribution of shipments by CSL

[ 7 MV­Xbox EPS Dist Tables ­ AG25 to AJ25 ]

and the UEC by CSL

[ Inputs – C182 to F182 ].

6­7Using these values, we calculate the weighted average (using the Excel SUMPRODUCT function). This result is displayed in [ 7 MV­Xbox EPS Dist Tables – AN25 ].

Table 6.2 Unit Energy Consumption in the Base Case (2013)

Candidate Standard Level CSL 0 CSL 1 CSL 2 CSL 3 Weighted Average

UEC Percentage of Current Shipments 2.5% 92.5% 5% 0%

UEC (kWh/year) 126.01 32.44 31.85 26.57 34.75

This calculation is then repeated for each year new products are shipped during the analysis period, with the results displayed in [ 7 MV­Xbox EPS Dist Tables – AN25 to AN44 ].

Step 2: Weighted Average Unit Energy Consumption in the Standards Case

Starting in 2013 we take the standards case distribution of shipments by CSL

­

[ 7 MV­Xbox EPS Dist Tables ­ AG71 to AJ71 ]

­

and the UEC by CSL

­

[ Inputs – C182 to F182 ].

­

Using these values, we calculate the weighted average (using the Excel SUMPRODUCT function). This result is displayed in [ 7 MV­Xbox EPS Dist Tables – AN71 ].

Table 6.3 Unit Energy Consumption in the Standards Case (2013)

Candidate Standard Level CSL 0 CSL 1 CSL 2 CSL 3 Weighted Average

UEC Percentage of Current Shipments 0% 95% 5% 0%

6­8UEC (kWh/year) 126.01 32.44 31.85 26.57 32.41

This calculation is then repeated for each year new products are shipped during the analysis period, with the results displayed in [ 7 MV­Xbox EPS Dist Tables – AN71 to AN90 ].

Step 3: Calculating the Unit Energy Savings (UES) due to the standard:

Using the results from steps 1 and 2, we calculate the difference in UEC for each year.

Starting in 2013, we take the UEC for the base case:

[ 7 MV­Xbox EPS Dist Tables – A025 ] 34.75 kWh/year

and subtract the UEC for the standard case:

[ 7 MV­Xbox EPS Dist Tables – A071 ] 32.41 kWh/year

Yielding a UES of 2.34 kWh/year

This result is displayed in [ 7 MV­Xbox EPS Dist Tables – AP71 ]. This calculation is repeated for each year new products are shipped during the analysis period, with the results displayed in [ 7 MV­Xbox EPS Dist Tables – AP71 to AP90 ].

6.4.2 Calculation of National Energy Savings in kWh

To calculate energy saving in a year, we combine the inventory of products for that year with the unit energy savings for each shipment year. Performing this calculation for each year of the analysis period generates the National Energy Savings in kWh.

For example, in 2018:

We take the unit energy savings by shipment year : ­

6­9[ 7 MV­Xbox EPS Dist Tables – AP71 to AP90 ]

Table 6.4 Unit Energy Savings by Shipment Year

Year UES

2013 2.3391

2014 1.8713

2015 1.4035

2016 0.9357

2017 0.4678

2018 0.0000

2019 0.0000

2020 0.0000

2021 0.0000

2022 0.0000

2023 0.0000

2024 0.0000

2025 0.0000

2026 0.0000

2027 0.0000

2028 0.0000

2029 0.0000

2030 0.0000

2031 0.0000

2032 0.0000

We then take the inventory of units in 2018:

[ 5 Inventory – N56 to N75 ]

Table 6.5 Unit Inventory In 2018

Year Number of

Units

2013

­ 2014 4,776,209

2015 4,919,495

2016 5,067,080

2017 5,219,093

2018 5,375,666

2019

­ 2020

­ 2021

­ 2022

­ 2023

­

6­102024

­ 2025

­ 2026

­ 2027

­ 2028

­ 2029

­ 2030

­ 2031

­ 2032

­

Combining these tables yields:

Table 6.6 Combination of Tables 6.4 and 6.5

Shipment

Year UES

kWh Number

of Units Total Energy Savings

2013 2.3391

­ ­ 2014 1.8713 4,776,209 8,937,720

2015 1.4035 4,919,495 6,904,511

2016 0.9357 5,067,080 4,741,267

2017 0.4678 5,219,093 2,441,492

2018 0.0000 5,375,666 0

2019 0.0000

­ ­ 2020 0.0000

­ ­ 2021 0.0000

­ ­ 2022 0.0000

­ ­ 2023 0.0000

­ ­ 2024 0.0000

­ ­ 2025 0.0000

­ ­ 2026 0.0000

­ ­ 2027 0.0000

­ ­ 2028 0.0000

­ ­ 2029 0.0000

­ ­ 2030 0.0000

­ ­ 2031 0.0000

­ ­ 2032 0.0000

­ ­ Total Energy Savings (2018) 23,024,800*
*Total value may be different due to rounding.

The resulting total is displayed in:

[ 3 NES – Q3 ]

6­11This calculation is repeated for each year, until no inventory is left to generate savings. In the case of the Xbox 360, which has a lifetime of 5 years, the last year of shipments is 2032, so the last year of savings would be 2036. The values by year are displayed in:

[ 3 NES – G3 to AT3 ] and the sum of all years is displayed in [ 3 NES – AU3 ].

6.4.3 Calculation of National Energy Savings in 2008$

To convert the NES from kWh to discounted 2008$, we combine the results of

­National Energy Savings in kWh [ 3 NES – G3 to AT3 ] with

­the electricity price for each year [ 2 Inputs – C287 to AP287 ]

The results for each year are displayed in:

[ 4 NPV – G11 to AT11 ] with the total for all years in [ 4 NPV –AU11 ]

These values are multiplied against

­the discount multiplier for each year from [ 4 NPV – G22 to AT22 ]

The results for each year are displayed in:

[ 4 NPV – G25 to AT25 ] with the total for all years in [ 4 NPV –AU25 ]

6.4.4 Calculating Incremental Unit Cost Increases

Incremental Unit Costs are calculated in the same way that unit energy savings are calculated.

Step 1: Weighted Average Unit Cost in the Base Case

Starting in 2013 we take the base case distribution of shipments by CSL

­

[ 7 MV­Xbox EPS Dist Tables ­ AG25 to AJ25 ]

­

and the unit cost by CSL

­

[ Inputs – C192 to F192 ].

­

6­12Using these values, we calculate the weighted average (using the Excel SUMPRODUCT function). This result is displayed in [ 7 MV­Xbox EPS Dist Tables – AQ25 ].

Table 6.7 Unit Cost in the Base Case

Candidate Standard Level CSL 0 CSL 1 CSL 2 CSL 3 Weighted Average

Unit Cost Percentage of Current Shipments 2.5% 92.5% 5% 0%

Unit Cost ($) 19.07 28.10 28.48 38.27 27.90

This calculation is then repeated for each year new products are shipped during the analysis period, with the results displayed in [ 7 MV­Xbox EPS Dist Tables – AQ25 to AQ44 ].

Step 2: Weighted Average Unit Cost in the Standards Case

Starting in 2013 we take the standards case distribution of shipments by CSL

­

[ 7 MV­Xbox EPS Dist Tables ­ AG71 to AJ71 ]

­

and the unit cost by CSL

­

[ Inputs – C192 to F192 ].

­

Using these values, we calculate the weighted average (using the Excel SUMPRODUCT function). This result is displayed in [ 7 MV­Xbox EPS Dist Tables – AQ71 ].

Table 6.8 Unit Cost in the Standards Case

Candidate Standard Level CSL 0 CSL 1 CSL 2 CSL 3 Weighted Average

Unit Cost Percentage of Current Shipments 0% 95% 5% 0%

Unit Cost ($) 19.07 28.10 28.48 38.27 28.12

6­13This calculation is then repeated for each year new products are shipped during the analysis period, with the results displayed in [ 7 MV­Xbox EPS Dist Tables – AQ71 to AQ90 ].

Step 3: Calculating the Unit Incremental Cost Increase due to the standard:

Using the results from steps 1 and 2, we calculate the difference in unit cost for each year.

Starting in 2013, we take the unit cost for the standards case:

­

[ 7 MV­Xbox EPS Dist Tables – AQ71 ] $28.12

­

And subtract the unit cost for the base case:

­

[ 7 MV­Xbox EPS Dist Tables – AQ25 ] $27.90

­

Yielding an incremental unit cost increase of $0.23*

­

(* Note, values may be different due to rounding.)

­

This result is displayed in [ 7 MV­Xbox EPS Dist Tables – AR71 ]. This calculation is repeated for each year of the analysis period, with the results displayed in [ 7 MV­Xbox EPS Dist Tables –

AR71 to AR90 ].

6.4.5 Calculation of National Costs in $ (non­discounted)

To calculate total improvement costs, we combine the weighted­average incremental unit costs from the previous step with the numbers of EPSs shipped. Performing this calculation for each year of the analysis period generates the total costs in $ (non­discounted).

Take the incremental unit cost:

[ 7 MV­Xbox EPS Dist Tables – AR71 to AR90 ]

6­14Table 6.9 Unit Incremental Cost by Shipment Year

­

Shipment Year Unit Incremental Cost Increase ($)

2013 0.2258

2014 0.1807

2015 0.1355

2016 0.0903

2017 0.0452

2018 0.0000

2019 0.0000

2020 0.0000

2021 0.0000

2022 0.0000

2023 0.0000

2024 0.0000

2025 0.0000

2026 0.0000

2027 0.0000

2028 0.0000

2029 0.0000

2030 0.0000

2031 0.0000

2032 0.0000

Take the shipments of EPSs by year.

[ 5 Inventory – AS56 to AS75 ]

Table 6.10 Unit Shipments by Shipment Year

Shipment Year Vintage Number of Units Shipped

2013 4,637,096

2014 4,776,209

2015 4,919,495

2016 5,067,080

2017 5,219,093

2018 5,375,666

2019 5,536,935

2020 5,703,044

2021 5,874,135

2022 6,050,359

2023 6,231,870

2024 6,418,826

2025 6,611,391

6­152026 6,809,732

2027 7,014,024

2028 7,224,445

2029 7,441,178

2030 7,664,414

2031 7,894,346

2032 8,131,176

Combining these tables yields:

Table 6.11 Combination of Tables 6.9 and 6.10

Shipment

Year Unit Incremental Cost Increase ($) Number of Units Total Costs by Year

2013 0.2258 4,637,096 1,047,056

2014 0.1807 4,776,209 862,831

2015 0.1355 4,919,495 666,537

2016 0.0903 5,067,080 457,689

2017 0.0452 5,219,093 235,710

2018 0.0000 5,375,666 0

2019 0.0000 5,536,935 0

2020 0.0000 5,703,044 0

2021 0.0000 5,874,135 0

2022 0.0000 6,050,359 0

2023 0.0000 6,231,870 0

2024 0.0000 6,418,826 0

2025 0.0000 6,611,391 0

2026 0.0000 6,809,732 0

2027 0.0000 7,014,024 0

2028 0.0000 7,224,445 0

2029 0.0000 7,441,178 0

2030 0.0000 7,664,414 0

2031 0.0000 7,894,346 0

2032 0.0000 8,131,176 0

Total Costs 3,269,891

The resulting total by year is displayed in:

­

[ 4 NPV – G17 to AT17 ]

­

and the sum of all years is displayed in:

­ [ 4 NPV – AU17 ].

­

6­166.4.6 Calculation of National Costs in 2008$

To convert the national costs to discounted 2008$, we combine the results of

­National Costs [ 4 NPV – G17 to AT17 ] with

­the discount multiplier for each year from [ 4 NPV – G22 to AT22 ]

The results for each year are displayed in:

[ 4 NPV – G31 to AT31 ] with the total for all years in [ 4 NPV –AU31 ]

6.4.7 Calculation of Net Present Value in 2008$

To calculate Net Present Value, we simply calculate the difference between

National Energy Savings (in 2008$) [ 4 NPV – G25 to AT25 ] and

National Costs (in 2008$) [ 4 NPV – G31 to AT31 ]

The results for each year are displayed in:

[ 4 NPV – G37 to AT37 ] with the total for all years in [ 4 NPV –AU37 ]

6.5 Net Present Value Results

This section contains tables which show the net present value (NPV) of standards for non­Class A external power supplies using discount rates of 3 percent (Table 6.12) and 7 percent (Table 6.13). The NPV of standards at each candidate standard level (CSL) is expressed as a range, reflecting uncertainty about the rate of efficiency improvements in the absence of a standard. The lower value represents the NPV using a base case efficiency forecast where efficiency would improve even in the absence of a standard. The higher value represents the NPV using a base case efficiency forecast where efficiency would not improve without a standard. These efficiency forecasts are explained in section III.A.3 “Market Assessment ­ Shipments, Efficiency

6­17Distributions, and Market Growth” of the NOPR and can be viewed in the NES­NPV Excel

workbooks. b Negative values are shown in parentheses.

Table 6.12 Net Present Value of Standards at 3 Percent Discount Rate

Type of EPS Net Present Value at 3 Percent Discount Rate 2013 to 2042 ($ millions)

CSL 1 CSL 2 CSL 3

Multi­Voltage for

Multifunction Devices 113.6 ­ 129.1 139.3 ­ 157.4 155.9 ­ 174.4

Multi­Voltage for Xbox 360 13.1 ­ 189.4 (0.96) ­ 187.5 (517.1) – (341.0)

High Power (>250 W) 1.8 ­ 2.3 2.1 ­ 2.7 2.36 ­ 2.94

For Medical Devices 31.9 ­ 56.7 141.8 ­ 192.0 80.9 ­ 129.9

For Battery Chargers for Floor Care Appliances 2.8 ­ 4.8 4.4 ­ 6.3 8.0 ­ 10.1

For Battery Chargers for

Power Tools 1.3 ­ 2.3 2.62 ­ 3.5 4.1 ­ 5.1

Note: Negative values are shown in parentheses.

­

b Available for download from the EERE website: http://www.eere.energy.gov/buildings/appliance_standards/residential/battery_external.html

6­18Table 6.13 Net Present Value of Standards at 7 Percent Discount Rate

­

Type of EPS Net Present Value at 7 Percent Discount Rate 2013 to 2042 ($ millions)

CSL 1 CSL 2 CSL 3

Multi­Voltage for

Multifunction Devices 59.9 ­ 67.8 68.2 ­ 76.9 75.9 ­ 84.8

Multi­Voltage for Xbox 360 9.4 ­ 100.9 0.7 ­ 98.4 (316.4) – (225.2)

High Power (>250 W) 0.9 ­ 1.2 1.1 ­ 1.4 1.2 ­ 1.5

For Medical Devices 16.9 ­ 28.2 74.2 ­ 97.8 26.8 ­ 49.5

For Battery Chargers for Floor Care Appliances 1.6 ­ 2.6 2.5 ­ 3.5 4.5 ­ 5.6

For Battery Chargers for

Power Tools 0.7 ­ 1.2 1.5 ­ 1.9 2.3 ­ 2.8

Note: Negative values are shown in parentheses.

­

6­19APPENDIX A. NON­CLASS A EXTERNAL POWER SUPPLY COST­EFFICIENCY

ESTIMATION SURVEY

Navigant Consulting, Inc. (NCI) is conducting an engineering analysis to understand the relationship between manufacturers’ cost and the efficiency a of external power supplies (EPSs). This engineering analysis is part of a larger determination analysis on whether the U.S.Department of Energy should conduct an energy conservation standards rulemaking on nonClass A external power supplies (NCA EPSs). These EPSs are defined in contrast to “Class A” EPSs as defined by EISA 2007 as being less than 250 W output power, not for medical devices, and single­output voltage – among other criteria. Through this worksheet, NCI is seeking your guidance on design changes you might make to external power supplies to improve their efficiency.

NCI is currently focusing its analysis on:

1.

­ A medical EPS with a nameplate output rating of 18 W and 12 V

2.

­ A multiple­voltage EPS with a nameplate output rating of 40 W with 16 V and 32 V

busses

3.

­ A multiple­voltage EPS with a nameplate output rating of 203 W with 12 V and 5 V

busses

4.

­ A linear­regulated high power EPS with nameplate output rating of 345 W with a 13.8 V

bus

5.

­ A switching­regulated high power EPS with nameplate output rating of 345 W with a

13.8 V bus

Please describe the discrete design steps you would undertake to achieve the efficiency level and no­load power specification shown in the table below. In each case, start with a baseline SMPS, and list the necessary design changes to enable it to meet the higher efficiency levels. The efficiency levels are defined to be: Efficiency

Level Descriptor Explanation

0 Baseline, lowest cost A cheap, low­efficiency model

1 Intermediate level A model with improved efficiency, but less than

EISA 2007

2 Exactly EISA 2007 A model that has efficiency just at the EISA 2007

level

3 EISA 2007 qualified A model that comfortably qualifies as EISA 2007

4 Maximum commercially

achieved The highest efficiency of the ENERGY STAR qualifying units (US EPA 2007) b

5 Maximum technologically

feasible The highest­efficiency model possible

a “Efficiency” is used in this worksheet as a proxy for both conversion efficiency and no­load power.

b Taken in 2007 from “Table 6­1 – Outstanding EPS in terms of average efficiency and no­load losses” from www.ecocharger.org/docs/BioConsortium_EuP_Lot7_Task%206.pdf

iFor each design change, please also provide an estimate of your incremental production cost over the baseline, as well as the total unit selling price to an OEM or distributor. In case it is not possible to list the increase in cost per design change, please specify the total bill­of­materials (BOM) cost increase for all the improvements. Finally, please describe your markup structure to make it clear how increases in production costs impact the total per­unit manufacturer’s selling price.

We recognize that detailed designs may be difficult to prepare; therefore, in the interests of generating reasonable results in a short space of time, we invite you to use your best judgment and experience when completing the following tables.

In addition, we believe that the output cord can be a significant source of loss for the external power supply. To address this, we consider efficiency at two points: at the output where the PCB connects to the output cord and at the end of the output cord.

iiPlease use the following design specifications:

­

EPS 1: 18W MEDICAL EXTERNAL POWER SUPPLY

Input voltage: 115 volts rms, 60 Hz Unit volume: 5,000 units per year

Input protection: Primary current fuse, inrush current limiting Application: Medical diagnostic

Output voltage regulation: ± 1% (excluding cord) Package: Sealed polycarbonate

Output voltage ripple: 1% V P­P maximum Output cord length: 6 feet

Transient response: 0.5 ms for 50% load change typical Regulatory compliance: UL 60601­1, FCC

Output protection: Overcurrent protection, short­circuit protection Product lifetime: ~10 years

EPS 2: 40W MULTIPLE VOLTAGE EXTERNAL POWER SUPPLY

Input voltage: 115 volts rms, 60 Hz Unit volume: 1M units per year

Input protection: Primary current fuse, inrush current limiting Application: Printer

Output voltage regulation: ± 5% (excluding cord) Package: Sealed polycarbonate

Output voltage ripple: 2% V P­P maximum Output cord length: 6 feet

Transient response: 0.5 ms for 50% load change typical Regulatory compliance: UL, FCC

Output protection: Overcurrent protection, short­circuit protection Product lifetime: 4 years

iiiEPS 3: 203W MULTIPLE VOLTAGE EXTERNAL POWER SUPPLY

Input voltage: 115 volts rms, 60 Hz Unit volume: 4M units per year

Input protection: Primary current fuse, inrush current limiting Application: Video Game System

Output voltage regulation: ± 1% (excluding cord) Package: Sealed polycarbonate

Output voltage ripple: 1% V P­P maximum Output cord length: 6 feet

Transient response: 0.5 ms for 50% load change typical Regulatory compliance: UL, FCC

Output protection: Overcurrent protection, short­circuit protection Product lifetime: 4 years

EPS 4 and EPS 5: 345W HIGH POWER EXTERNAL POWER SUPPLY

Input voltage: 115 volts rms, 60 Hz Unit volume: ? units per year

Input protection: Primary current fuse, inrush current limiting Application: Ham radio

Output voltage regulation: ± 1% (excluding cord) Package: Sealed polycarbonate

Output voltage ripple: 1% V P­P maximum Output cord length: 6 feet

Transient response: 0.5 ms for 50% load change typical Regulatory compliance: UL, FCC

Output protection: Overcurrent protection, short­circuit protection Product lifetime: 4(?) years

Thank you for your input. If you have any questions or suggestions, please contact:

­

Matt Malinowski Michael Vladimer

202­481­7304 202­481­7323 Matt.Malinowski@NavigantConsulting.com MVladimer@NavigantConsulting.com

ivThe table on this page provides an example of the kind of information we need in order to create a cost­efficiency curve for non­Class A EPSs. In this particular example, we show one set of improvements for increasing the efficiency of an 80%­efficient 75 W, 12 V Class A EPS to meet the requirements of the EISA 2007. This example is purely illustrative. However, this table does provide an indication of the level of detail being requested for the tables on the following pages. The column labeled “Incremental Unit Cost per Improvement” represents the cost of the specific improvement described. If additional rows are needed to describe all the design changes you would make, please feel free to modify the tables. The column labeled “Total Mfr. Unit Selling Price” is your final selling price to your customers, such as OEMs or distributors.

Example: EPS 1: Class A EPS POUT = 75 W, VOUT = 12 V

# Efficiency

Level Conversion Efficiency NoLoad

Power Defining Design

Characteristics Mfr. Production Cost Total

Mfr.

Unit Selling

Price Board Output EndofCord
2­stage topology with

­ PFC

$8 UC3844 PWM controller

­

0 Baseline,

lowest cost 74% 1 W E­type transformer

­ Output rectifier w/

Schottkies ­

Size: 4 in x 2.5 in x 1.5

­ in

# Efficiency

Level Conversion Efficiency NoLoad

Power Improvements over

Baseline to Meet Efficiency Level Incremental Cost (over Baseline) per Improvement Total

Mfr.

Unit Selling

Price Board Output EndofCord
Variable­frequency

PWM controller IC + $0.05

Change in transformer + $0.20 due to higher IC

2 Exactly

EISA 2007 85 % 0.5 W switching frequency $10 Additional filtering caps due to higher IC EMI + $0.12

Miscellaneous additional + $0.10 components (e.g., XXXXX)

vEPS 1: Medical Grade, P OUT = 18 W, V OUT = 12 V

Conversion

# Efficiency

Level Efficiency c NoLoad

Power Defining Design

Characteristics Mfr.

Production

Cost Total Mfr. Unit Selling

Price Board Output EndofCord

0 Baseline:

lowest­cost 65% d 1 W

# Efficiency

Level Conversion Efficiency NoLoad

Power Improvements over

Baseline to Meet Efficiency Level Incremental Cost (over Baseline) per Improvement Total Mfr. Unit Selling

Price Board Output EndofCord

1 Intermediate 70% 0.8 W

2 Exactly EISA

2007 76% 0.5 W

3 EISA 2007 qualified 78% 0.3 W

4 Maximum Commercially

Achieved 88% 0.15 W

c Conversion efficiency, as defined by DOE, ENERGY STAR, and CEC test procedures, is the arithmetic mean of

­ efficiencies at 100%, 75%, 50%, and 25% of maximum rated output current.

­ d These are NCI’s straw­man estimates of efficiency values. We welcome your input on these values.

­

vi5 Maximum Technologically

Feasible 90% 0.10 W

• How do you apply markups to your production costs in order to arrive at an OEM and distributor selling price?

viiEPS 2: Multiple­voltage EPS POUT = 40 W, V1 = 16 V @ 0.625 A, V2 = 32 V @ 0.940 A

­ Conversion

# Efficiency

Level Efficiency e NoLoad

Power Defining Design

Characteristics Mfr.

Production

Cost Total Mfr. Unit Selling

Price Board Output EndofCord

0 Baseline:

lowest­cost 65% f 1.4 W

# Efficiency

Level Conversion Efficiency NoLoad

Power Improvements over

Baseline to Meet Efficiency Level Incremental Cost (over Baseline) per Improvement Total Mfr. Unit Selling

Price Board Output EndofCord

1 Intermediate 75% 1 W

2 Exactly EISA

2007 83.6% 0.5 W

3 EISA 2007 qualified 85% 0.45 W

4 Maximum Commercially

Achieved 89% 0.31 W

e Conversion efficiency, as defined by DOE proposed multiple­voltage test procedure, is the arithmetic mean of

­ efficiencies at 100%, 75%, 50%, and 25% of simultaneous loading to maximum rated output current, adjusted for

­ derating and minimum output requirements.

­ f These are NCI’s straw­man estimates of efficiency values. We welcome your input on these values.

­

viii5 Maximum Technologically

Feasible 90% 0.2 W

ixEPS 3: Multiple­voltage EPS POUT = 203 W, V1 = 12 V @ 16.5 A, V2 = 5 V @ 1 A

­ Conversion

# Efficiency

Level Efficiency g NoLoad

Power Defining Design

Characteristics Mfr.

Production

Cost Total Mfr. Unit Selling

Price Board Output EndofCord

0 Baseline:

lowest­cost 80% h 1.4 W

# Efficiency

Level Conversion Efficiency NoLoad

Power Improvements over

Baseline to Meet Efficiency Level Incremental Cost (over Baseline) per Improvement Total Mfr. Unit Selling

Price Board Output EndofCord

1 Intermediate 82% 1 W

2 Exactly EISA

2007 85% 0.5 W

3 EISA 2007 qualified 86.5% 0.45 W

4 Maximum i
Commercially

Achieved 89% 0.3 W

g Conversion efficiency, as defined by DOE proposed multiple­voltage test procedure, is the arithmetic mean of efficiencies at 100%, 75%, 50%, and 25% of simultaneous loading to maximum rated output current, adjusted for derating and minimum output requirements.

h These are Navigant Consulting’s straw­man estimates of efficiency values. We welcome your input on these

values.

i These values have not been commercially achieved for multiple­voltage EPSs. We welcome your input on these

values.

x5 Maximum Technologically

Feasible 91% 0.3 W

xiEPS 4: High Power EPS (Linear­Regulated) POUT = 345 W, V1 = 13.8 V @ 25 A

­

# Efficiency

Level Conversion Efficiency j NoLoad

Power Defining Design

Characteristics Mfr.

Production

Cost Total Mfr. Unit Selling

Price Board Output EndofCord

0 Baseline:

lowest­cost 55% k 18 W

# Efficiency

Level Conversion Efficiency NoLoad

Power Improvements over

Baseline to Meet Efficiency Level Incremental Cost (over Baseline) per Improvement Total Mfr. Unit Selling

Price Board Output EndofCord

1 Intermediate 1 l 62% 15 W

2 Intermediate 2 75 % 12 W

3 Exactly EISA

2007 85% 8 W

j Conversion efficiency, as defined by DOE proposed multiple­voltage test procedure, is the arithmetic mean of

­ efficiencies at 100%, 75%, 50%, and 25% of simultaneous loading to maximum rated output current, adjusted for

­ derating and minimum output requirements.

­ k These are NCI’s straw­man estimates of efficiency values. We welcome your input on these values.

­ l This level corresponds to data points measured by Navigant Consulting.

­

xiiEPS 5: High Power EPS (Switched­mode) POUT = 345 W, V1 = 13.8 V @ 25 A

­

# Efficiency

Level Conversion Efficiency m NoLoad

Power Defining Design

Characteristics Mfr.

Production

Cost Total Mfr. Unit Selling

Price Board Output EndofCord

0 Baseline:

lowest­cost 80% n 10 W

# Efficiency

Level Conversion Efficiency NoLoad

Power Improvements over

Baseline to Meet Efficiency Level Incremental Cost (over Baseline) per Improvement Total Mfr. Unit Selling

Price Board Output EndofCord

1 Intermediate o 81% 6 W

2 Exactly EISA

2007 85% 0.5 W

3 EISA 2007 qualified 86% 0.45 W

4 Maximum Commercially

Achieved 90% 0.3 W

m Conversion efficiency, as defined by DOE proposed multiple­voltage test procedure, is the arithmetic mean of

­ efficiencies at 100%, 75%, 50%, and 25% of simultaneous loading to maximum rated output current, adjusted for

­ derating and minimum output requirements.

­

n These are NCI’s straw­man estimates of efficiency values. We welcome your input on these values.

­

o This level corresponds to data points measured by Navigant Consulting.

xiii5 Maximum Technologically

Feasible 93% 0.2 W

xiv