AP62- MR16 Reference DesignCree® XLamp® MT-G
MR16 Reference Design

CLD-AP62 REV 0

APPLICATION NOTE

Cree XLamp® MT-G MR16 Reference Design

1: MR16 Assembly (Left: Carclo TIR optic, Right: Ledil reflector optic)
Figure 1: MR16Figure
assembly(left: Carclo TIR optic, right: Ledil reflector optic)

The design and production of high lumen, small-form, point-source illumination has been oneof the more problematic solid state lighting applications. High lumen density combined withlimited space for drive electronics and thermal dissipation have limited the adoption of LED
illumination in applications like MR16 bulbs.

TABLE OF CONTENTSINTRODUCTION
In addition to being an interesting exercise in systems
development, we are presenting a multivendor, multi-disciplinary approach to solving the MR16 lamp constraints. The successful
Introduction......................................................... 1
The design and production of high-lumen, small-form,
solution has required collaborative design and innovation in LED packaging, power supply,
Design approach/objectives...................................
3 to bringpoint-source
illuminationpractices
has been
optics and heat sink development. In ordera series of industry-leading
to one of the more
bear
on
a
trickyproblem,webelieve
this
kind
of
collaboration
will
becomeincreasingly
The 6-step methodology........................................ 4
challenging solid-state lighting applications. Requirecommon in the solid state lighting arena. Just as traditional lamp and ballast manufacturers
1. Define lighting requirements......................... 4
ments for high lumen density combined with limited
have engaged in symbiotic development so too must companies working on LED illumination
2. Define Design
goals.....................................
8 beneficial
spaceproblems.
for drive electronics and thermal dissipation havecomponents
work together to solve mutually
3. Estimate efficiencies of the optical, thermal &limited the adoption of LED illumination in applications
This application note details the design of an MR16 bulb with Cree’s XLamp MT-G component.
electrical systems........................................ 8
like MR16 bulbs.
The goal of the design is to enable a LED-based MR16
replacement retrofit bulb, which delivers
4. Calculate theequivalent
number performanceof LEDs .....................14
to a 35W-50W Halogen MR16s and conforms to the latest Energy Star1
requirements.
5. Consider all design
possibilities...................14
In addition to being an interesting exercise in systems
6. Complete the final steps: implementation anddevelopment, we are presenting a multi-vendor, multi-

Special Thanks....................................................18

orative design and innovation in LED packaging, power1

As specified in the Integral LED Lamps specification version 1.1
analysis....................................................15
disciplinary approachandto
http://www.energystar.gov/ia/partners/manuf_res/downloads/IntegralLampsFINAL.pdf
the solving
Energy Starthe MR16-lamp conIntegral LED Lamp Center Beam Intensity Benchmark Tool (ed7/6/2010) The successful solution has required collabConclusions........................................................18
straints.
http://www.energystar.gov/ia/partners/manuf_res/downloads/EIQ_Form_All_Categories.xls

supply, optics and heat-sink development. In order to
WWW. CREE.COM/XLAMP

2011-02-14

Cree Company Confidential
Pagepractices
1 of 18
bring a series of industry-leading
to bear on atricky problem, we believe this kind of collaboration will
become increasingly common in the solid-state lighting arena. Just as traditional lamp and ballast manufacturers have engaged in symbiotic development, so too

Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor
Copyright© 2010Cree, Inc.
rights reserved. The information in this document is subject to change without notice.
endorsement,
sponsorshipor Allassociation.
Cree,
the CreelogoCree,and XLamp
registeredtrademarksof Cree, inInc.
Copyright© 2011
Inc. Allare
rightsreserved.
The information
this document is subject to change without notice. Cree, the Cree logo
and XLamp are registered trademarks of Cree, Inc. This document is provided for informational purposes only and is not a warranty or a
specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree
Sales at sales@cree.com.

Cree, Inc.
4600 Silicon Drive
Durham, NC 27703
USA Tel: +1.919.313.5300

XLAMP MT-G MR16 REFERENCE DESIGN

must companies working on LED illumination components work together to solve problems in a mutually beneficial way.
This application note details the design of an MR16 bulb with Cree’s XLamp® MT-G component. The goal of the design
is to enable an LED-based MR16 replacement retrofit bulb that delivers equivalent performance to 35W – 50W halogen
MR16s and conforms to the latest Energy Star requirements.1
In early 2011, many MR16 replacements currently available on the market underperform when compared to standard
halogen bulbs and several misrepresent their halogen equivalency on datasheets and packaging. The DOE’s CALIPER
testing program corroborates this, most recently with the CALIPER Round 11 tests.2
The design in this application note will show that a highly efficient, high lumen output multi-die LED array such as the
XLamp MT-G, when designed with the proper heat sink, optics and driver, can enable a true 35W – 50W MR16 bulb replacement, delivering superior product repeatability, efficacy and longevity.
In presenting this design, our team set out to create a luminaire with 50,000 hour L70 longevity, created through a low
power/high efficacy instrumentation of the LED. Cree created these MR16 prototypes using an elegant MR-form heatsink design from Neng Tyi Precision Industries Co., Ltd.,3 and collaborated with multiple industry-leading driver and optic
partners to create an integrated, optimized system with multiple components and combinations to function with the
MT-G LED. This reference design shows only a few possible implementations of an MR16 bulb with the MT-G LED and ismeant to demonstrate increasing value of multi-disciplinary design to bring segment leading products to market.

1
As specified in the Integral LED Lamps specification version 1.1 http://www.energystar.gov/ia/partners/manuf_res/downloads/IntegralLampsFINAL.pdf and the Energy Star Integral LED Lamp Center Beam Intensity Benchmark Tool (ed 7/6/2010) http://
www.energystar.gov/ia/partners/manuf_res/downloads/EIQ_Form_All_Categories.xls
2
http://www1.eere.energy.gov/buildings/ssl/caliper.html
3
http://www.nengtyi.com.tw/eindex.aspx

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

2

XLAMP MT-G MR16 REFERENCE DESIGNDESIGN APPROACH/OBJECTIVESIn the “LED Luminaire Design Guide”4 Cree advocates a six step framework for creating LED luminaires and lamps. We
use this framework, with the design guide’s summary table reproduced below.
Step
1.

Explanation

Define lighting requirements•

The design goals can be based either on an existing fixture or on the application’slighting requirements.

2.

Define design goals•

Specify design goals, which will be based on the application’s lighting requirements.

•

Specify any other goals that will influence the design, such as special optical orenvironmental requirements.

3.

Estimate efficiencies of the optical,•

Design goals will place constraints on the optical, thermal and electrical systems.

thermal & electrical systems•

Good estimations of efficiencies of each system can be made based on these constraints.

•

The combination of lighting goals and system effiiciencies will drive the number ofLEDs needed in the luminaire.

4.

Calculatethenumber

of

LEDs

•

needed5.

Based on the design goals and estimated losses, the designer can calculate thenumber of LEDs to meet the design goals.

Consider all design possibilities and•With any design, there are many ways to achieve the goals.

choose the best•

LED lighting is a new field; assumptions that work for conventional lighting sources
may not apply.

6.

4

Complete final steps•

Complete circuit board layout.

•

Test design choices by building a prototype luminaire.

•

Make sure the design achieves all the design goals.

•

Use the prototype to further refine the luminaire design.

•

Record observations and ideas for improvement.

LED Luminaire Design Guide, Application Note APO000015, www.cree.com/products/pdf/LED_Luminaire_Design_Guide.pdf

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

3

XLAMP MT-G MR16 REFERENCE DESIGN

THE 6-STEP METHODOLOGY

The major requirement and goal for this project was to demonstrate an easy-to-implement, high efficiency lamp that
could replace the current halogen MR16 bulbs on the market, showing that a true 35W-50W equivalent MR16 LED lamp
is possible at a reasonable cost. Cree framed the project as a retrofit, so the MR16 bulb designed in this application note
could take advantage of the installed base of track lighting and fixtures.5,6

1.

DEFINE LIGHTING REQUIREMENTS

The table below lists important characteristics to consider for the design of the MR16 in this reference design.
ImportanceCriticalCharacteristics

Unitslight intensity

CBCP (foot-candles)

beam angle (FWHM)

degrees

electrical power

watts (W)luminous flux

lumens (lm)form factor

Important

price

$

lifetime (L70)

hours

operating temperatures°C

operating humidity% RH

color temperature

K

CRI

100-pt scalebulb-to-bulb consistency
driver power factor
manufacturablilty
Table 1: Important characteristics of target MR16 luminaire

Examination of existing halogen MR16 lamp data sheets gives basic benchmark data:7
SourceLuminaire Power

Luminous Flux

Efficacy

(W)

(Lm)

(Lm/W)

35W halogen wide flood

35

540

15.4

50W halogen narrow flood

50

800

50W halogen indoor flood

50

850

CBCP (cd)Beam Angle

Lifetime(°)(hours)8

1000

36°

3000

16.0

2500

24°

3000

17.0

1600

36°

3000

Table 2: Halogen MR16 data-sheet information8
5
Track Lighting markets are documented in a recently release report from the US Department of Energy, Energy Savings Estimates of Light Emitting Diodes in Niche Lighting Applications, http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/nichefinalreport_january2011.pdf
6Production and cost-optimized implementations are beyond the scope of this document.
7
Source: http://www.lighting.philips.com/us_en/browseliterature/download/p-5755.pdf
8Rated average life is the length of operation (in hours) at which point an average of 50% of the lamps will still be operationaland 50% will not.

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

4

XLAMP MT-G MR16 REFERENCE DESIGN

Measurement of MR16 halogen lamps as purchased from retail stores shows that the consistency of the beam angle ispoor. This application note will show that with proper design of an LED system, an MT-G-based MR16 will significantly
improve this and create a much more repeatable beam with equivalent intensity. The graphs below shows the measured
data, normalized to show the light distribution for various types of halogen MR16s.
The datashows
AP62- MR16
Reference
Designa significant variationof peak intensity locations and beam shape.

144

150

156

162

-180
168 174
100.0%-174 -168

-162

90.0%

80.0%

138
132

70.0%

126

Measured Normalized Intensity:
Halogen MR16s

-156
-150
-144
-138
-132

-126

60.0%

120

-120

50.0%

114

-114

40.0%

108

-108

30.0%

102

20.0%

-102

96

10.0%

-96

90

0.0%

-90

35W Indoor Flood #1

35W Indoor Flood #2
35W Indoor Flood #3
35W Indoor Flood #4
50W Indoor Flood #1

84

-84

50W Indoor Flood #2

78

-78

50W Indoor Flood #3

72

-72

50W Indoor Flood #4

66

-66

60

-60
54

-54
48

-48

42

-42
36

30

24

18

12

6

0

-6

-12

-18

-24

-30

-36

Figure 2: Measured
goniometric intensity
intensity polarpolar
plot of Halogen
MR16
Figure 2: Measured
goniometricplot ofhalogen MR16

Data from the Energy Star Program Requirements for Integral LED Lamps gives us additional
performance requirements9.
General Energy Star Luminaire Requirements:
Correlated Color
Temperature(CCT)
Nominal CCT
2700 K
3000 K
3500 K
4000 K
Color
Maintenance
Color Rendering
Index (CRI)
Dimming
9

The luminaire must have one of the following designated CCTs and fall within the
7-step chromaticity quadrangles as defined in the Appendix.
Target CCT (K) and tolerance
Target Duv and tolerance
2725 ± 145
0.000 ± 0.006
3045 ± 175
0.000 ± 0.006
3465 ± 245
0.000 ± 0.006
3985 ± 275
0.001 ± 0.006
The change of chromaticity over the minimum lumen maintenance test period(6000 hours) shall be within 0.007 on the CIE 1976 (u’,v’) diagram.
Minimum CRI (Ra) of 80. In addition, the R9 value must be greater than 0.
Lamps may be dimmable or nondimmable. Product packaging must clearly

http://www.energystar.gov/ia/partners/product_specs/program_reqs/ILL_prog_reqs.pdf

2011-02-14

Cree Company Confidential

Page 5 of 18

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

5

XLAMP MT-G MR16 REFERENCE DESIGN

Data from the Energy Star Program Requirements for Integral LED Lamps gives us additional performance requirements.9
General Energy Star Luminaire Requirements:
Correlated Color Temperature (CCT)The luminaire must have one of the following designated CCTs and fall within the 7-step
chromaticity quadrangles as defined in the Appendix.

Nominal CCT

Target CCT (K) and tolerance

Target Duv and tolerance

2700 K2725 ± 145

0.000 ± 0.006

3000 K

3045 ± 175

0.000 ± 0.006

3500 K3465 ± 245

0.000 ± 0.006

4000 K

3985 ± 275

0.001 ± 0.006

Color Maintenance
Color Rendering Index (CRI)

The change of chromaticity over the minimum lumen maintenance test period (6000
hours) shall be within 0.007 on the CIE 1976 (u’,v’) diagram.
Minimum CRI (Ra) of 80. In addition, the R9 value must be greater than 0.
Lamps may be dimmable or nondimmable. Product packaging must clearly indicate
whether the lamp is dimmable or not dimmable. Manufacturers qualifying dimmable

Dimming

products must maintain a Web page providing dimmer compatibility information.
Minimum efficacy, light output, CCT, CRI, and power factor of dimmable lamps will be
confirmed with the lamp operated at full power.

Warranty
Allowable Lamp Bases

A warranty must be provided for lamps, covering material repair or replacement for aminimum of three (3) years from the date of purchase.
Must be a lamp base listed by ANSI.
For lamp power ≤5 W and for low voltage lamps, no minimum power

Power Factor

Minimum Operating Temperaturefactor is required For lamp power >5 W, power factor must be ≥ 0.70
Note: Power factor must be measured at rated voltage.
Integral lamp shall have a minimum operating temperature of -20°C or below.
≥ 120 HzLED Operating

Note: This performance characteristic addresses problems with visible flicker due to low

Frequency

frequency operation and applies to steady-state as well as dimmed operation. Dimming
operation shall meet the requirement at all light output levels.

Electromagnetic and Radio Frequency In-

Integral LED lamps must meet the appropriate FCC requirements for consumer use (FCC

terference

47 CFR Part 15).

Audible Noise

Integral lamp shall have a Class A sound rating.
Power supply shall comply with IEEE C.62.41-1991, Class A operation. The line transient

Transient Protection

shall consist of seven strikes of a 100 kHz ring wave, 2.5 kV level, for both common
mode and differential mode.

Operating

Lamp shall operate at rated nominal voltage of 120, 240 or 277 VAC, or at 12 or 24

Voltage

VAC or VDC.

9

http://www.energystar.gov/ia/partners/product_specs/program_reqs/ILL_prog_reqs.pdf

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

6

XLAMP MT-G MR16 REFERENCE DESIGNAnd MR16-specific data:10
Application Requirements:
Criteria Item
Definition
Minimum luminous efficacy- Lamp diameter ≤ 20/8 inch

ENERGY STAR Requirements
Directional lamp means a lamp having at least 80% light output within a solid angle ofπ sr (corresponding to a cone with angle of 120°)
40 lm/W

Color Spatial

The variation of chromaticity within the beam angle shall be within 0.006 from the

Uniformity

weighted average point on the CIE 1976 (u’,v’) diagram.

Maximum lamp
diameter
Maximum overall
length (MOL)

Not to exceed target lamp diameter
Not to exceed MOL for target lamp
Link to online tool at

Minimum center

http://www.drintl.com/htmlemail/Energystar/Dec09/ESIntLampCenterBeamTool.zip

beam intensity

Enter the following information into the online tool:- MR16 lamps

Target lamp nominal wattage
Target lamp beam angle in degrees (Note: maximum allowable beam angle = 50°.)

Lumen
Maintenance≥ 70% lumen maintenance (L70) at 25,000 hours of operation

Rapid-Cycle

Cycle times must be 2 minutes on, 2 minutes off. Lamp will be cycled once for every two

Stress Test

hours of required minimum L70 life.

10

Ibid. p13-14

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

7

XLAMP MT-G MR16 REFERENCE DESIGN

2.

DEFINE DESIGN GOALS

The design goals for this project:
Characteristic

Unit

Minimum Goal

Target Goal

Luminaire Light Output

Lm

500

600

Illuminance Profile

Identical

Better

Power

W

<<50

<8

Beam Angle°

25°-40°25°-40°

Cd

1409

>2044

Cd

791

>1147

Hours

25,00050,000

K

3,000

3,000

80

85

30

40

Center Beam Candle Power:
27° Beam
Center Beam Candle Power:
38° Beam
Lifetime
CCT
CRI
Max ambient temperature

3.

ºC

ESTIMATE EFFICIENCIES OF THE OPTICAL, THERMAL & ELECTRICAL SYSTEMS

Component Efficiency
The MT-G EasyWhite LED has a variety of efficacies depending upon color temperature, bin, and drive conditions. Basedon the preliminary data of the MT-G, Cree chose to work with the MTGEZW-00-0000-0B00G030F, highlighted in yellow
below, to give the closest possible CCT equivalent to a halogen bulb and the highest efficiency. These components, when
attached to a proper heat sink and fit with an appropriate secondary optic and driven with the correct conditions, will
deliver the sufficient center beam candle power (CBCP) to be considered a 35W – 50W equivalent MR16 bulb as specified by Energy Star.

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

8

XLAMP MT-G MR16 REFERENCE DESIGN

Figure 3: Order codes from MT-G EasyWhite data sheet

Basic LED (not system) electrical data and optical output from Cree’s Product Characterization tool is listed below in
Figure 4.11

AP62- MR16 Reference Design

Figure 4: Cree's Product Characterization Tool with XLamp MT-G Minimum Flux Data

Figure 4: Cree’s Product Characterization Tool with Preliminary XLamp MT-G minimum flux data
11

calculations
use of the PCT, wedetermined
to drive the MT-G at 1.10A in
The analysis Aftercamesome
frombasic
Cree’s
Productand
Characterization
Tool.
http://pct.cree.com/

order to generate the sufficient system luminous output and efficacy. The choice wasconstrained by our desire to use less than 6.5 Watts of LED power while delivering more than
Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarks
the minimum required CBCP from the EnergyStar specification. We chose the lumen output
of Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warrantybased
information,please contact
Cree ourSalesexperienceat sales@cree.com.
on historical
data andin the conversion of lumens to candela for standard
9
secondary optics in the desired beam angle range.

XLAMP MT-G MR16 REFERENCE DESIGN

After some basic calculations and use of the PCT, we determined to drive the MT-G at 1.10A in order to generate thesufficient system luminous output and efficacy. The choice was constrained by our desire to use less than 6.5 Watts of
LED power while delivering more than the minimum required CBCP from the EnergyStar specification. We chose the lumen output based on historical data and our experience in the conversion of lumens to candela for standard secondary
optics in the desired beam angle range.

Thermal Requirements
The XLamp MT-G operates at just over 6 watts of power, at steady state temperature, when running at the chosen 1.10A input current and requires a heat sink to dissipate this thermal load. In an LED-based MR16 design, the heat sink must
not only dissipate the heat generated by the LED but also provide the mechanical frame for the LED, optic, driver andbase. Additionally, to be considered a true MR16 retrofit, the overall footprint must fit into the ANSI-standard envelope
AP62- MR16 Reference Design

as defined in ANSI C78.24-2001.12 We chose to find an off-the-shelf heat sink for this reference design instead of creating a custom heat sink. A benefit of this approachis to show how easy it can be to create a high-quality MR16 retrofit
as defined in ANSI C78.24-200112. We chose to find an off the shelf heat sink for this reference
bulb with the MT-G component.
design instead of creating a custom heat sink. A benefit of this approach is to show how easy it
can be to create a high quality MR16 retrofit bulb with the MT-G component.
After evaluating designs from several heat-sink manufacturers, we decided to focus on a single heat sink from Neng Tyi
After evaluating designs from several heat sink manufacturers, we decide to focus on a single
13
Precision Industries heatCo., sink
Ltd.,
which
met
the necessary
requirementsof thermal
dissipation for this project. We meafrom
NENG TYIPRECISION
INDUSTRIESCO., LTD.13 which
met the necessary
requirementsof thermal
dissipation
this project.
Wea thermal
resistance of heat sink.
sured a thermal resistanceof 4.5°C/W
heatsink toforambient(Θhs-a) measured
for the Neng
Tyi “Diamond”
4.5°C/W heat sink to ambient ( hs-a) for the Neng Tyi “Diamond” heat sink.

Figure 5: A picture of the Neng Tyi “Diamond” MR16 heat sink

Figure 5: The Neng Tyi “Diamond” MR16 heat sink

12
13

To verify the performance, thermal simulations were executed with ANSYS simulation
software14 . Shown below are the simulation results showing images of the assembly and across section the heat sink running at 6.5W input power in a 25°C ambient environment. The
peak solderpoint temperature calculated by the software is 79°C, or 54°C above ambient. The
thermal resistance of the MT-G component is 1.5°C/W, so the junction temperature will thus be~92°C. Since the XLamp MT-G LED is a new component, based on our experience with similar
LED systems (e.g. XLamp MP-L), we expect this design with this heat sink to attain the lifetime
http://www.nema.org/stds/c78-24.cfm
design goal of 50,000 hours, L7015.
http://www.nengtyi.com.tw

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

1012

http://www.nema.org/stds/c78-24.cfm

XLAMP MT-G MR16 REFERENCE DESIGN

To verify the performance, thermal simulations were executed with ANSYS, Inc. simulation software.14 Shown below are
the simulation results showing images of the assembly and a cross section of the heat sink running at 6.5W input power
in a 25°C ambient environment. The peak solderpoint temperature calculated by the software is 79°C, or 54°C above
ambient. The thermal effective resistance of the MT-G component is 1.5°C/W, so the junction temperature will thus be
89 °C. Since the XLamp MT-G LED is a new component, based on our experience with similar LED systems (e.g. XLamp
MP-L), we expect this design with this heat sink to attain both the minimal goal of an Energy Star-compliant L70 ratingof 25,000 hours and the target design goal of an L70 rating of 50,000 hours.15

AP62- MR16 Reference Design
AP62- MR16 Reference Design

Figure 6: Ansys Thermal Simulations.

Figure 6: Ansys thermal simulations
Figure 6: Ansys Thermal Simulations.

Data collected (below) from an MT-G mounted to the MR16 heat sink, running at 6.5W, shows
Data collected (below)
an MT-G
mountedto theMR16
heatsink, runningat 6.5W, shows thermal performance inthermal fromperformancein linewithin a few
degreeswiththe thermal
simulations
above.
Data collected (below) from an MT-G mounted to the MR16 heat sink, running at 6.5W, showsline within a few degrees with the thermal simulations above.
thermal performance in line within a few degrees with the thermal simulations above.

Figure 7: Measured solderpoint temperature above ambient of XLamp MT-G MR16 at 6.5W input power.
Figure 7: Measured solderpoint temperature above ambient of XLamp MT-G MR16 at 6.5W input power.

Figure 7: Measured solder-point temperature above ambient of XLamp MT-G MR16 at 6.5-W input power

14
15

Cree used Ansys DesignSpace, http://www.ansys.com/products/structural-mechanics/products.asp
That is, after 50,000 hours of operation, the LED will still deliver at least 70% of its initial luminous flux.

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

2011-02-14

2011-02-14

Cree Company Confidential

Cree Company Confidential

Page 11 of 18

Page 11 of 18

11

XLAMP MT-G MR16 REFERENCE DESIGN

Relative Flux Output vs. Junction Temperature (If = 1100 mA)

The following graph represents typical performance of each LED die in the XLamp MT-G

Relative Luminous Flux

120%

100%

80%

60%

40%

20%

0%
20

40

60

80

100

120

140

Junction Temperature (ºC)

Figure 8: XLamp MT-G Data Sheet: Relative Luminous Flux vs. Junction Temperature

Looking at either the PCT or information in the MT-G data sheet,16 a MT-G LED operating with a 90°C junction temperature will have a brightness of just less than 100% of the 85°C pulsed binning data, which is confirmed in our measurements.

Drive Electronics
One of the biggest challenges of this design was fitting the necessary drive electronics into the small area of the MR16
base. Numerous types of transformers are on the market, including magnetic and electronic. Full compatibility withall transformers will depend significantly on driver design and is not in the scope of this document. For this reference
design, Cree focused on the more-common electric transformers, such as the Lightech17 LET 60 LW, a low-wattagetransformer compatible with both LED and halogen MR16s. Standard MR16 track lighting transformers supply 12 VAC
to the bulbs, so the internal driver must convert the 12 VAC from the transformer to a 1.10-A current source for the
MT-G component, running at approximately 6.0 V. We determined the driver would have to be 80% efficient in order tominimize the total load to under 8 W and not generate excess heat.
Working with several driver partners, we identified and characterized three solutions for this reference design. Drivers
from Diodes Incorporated,18 National Semiconductor,19 and Texas Instruments20 were fabricated by each company to fit
the required form factor and deliver the necessary current.

16
17
18
19
20

www.cree.com/products/pdf/XLampMTG-EZW.pdf
Lightech Electronic Industries, Ltd. website: http://lightechinc.com
Diodes Incorporated’s website: http://www.diodes.com/zetex/cree.html
National Semiconductor Corporation’s website: http://www.national.com/analog/partner/creeTexas Instruments, Incorporated’s website/reference design link/etc. http://www.ti.com/led

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

12

XLAMP MT-G MR16 REFERENCE DESIGN
AP62- MR16 Reference Design

Instruments20 were fabricated by each company to fit the required form factor and deliver thenecessary current.
Schematics and reference designs of the specific drivers used can be found on each of the
Schematics and reference
designs websites.
of the specificdrivers
used canbe found on
each
of on
the
driversuppliers’ websites. The
driver suppliers’
The driverfrom National
Semiconductor
was
based
their
LM3401The driverwas
frombased
Diodeson
Inc their
was basedon their
AL8806 controller.
The driverdriver from Nationalcontroller.
Semiconductor
LM3401
controller.
The driverfrom from
Diodes, Inc. was based on
Texas Instruments was based on their TPS54260 controller. All of these drivers were ~80%
their AL8806 controller. The driver from Texas Instruments was based on their TPS54260 controller. All of these drivers
efficient and had a power factor of 0.6-0.9.
were ~80% efficient and had a power factor of 0.6-0.9.

Figure 9: Driver image (from left: National Semiconductor, Diodes Inc, Texas Instruments)

Secondary Optics
Figure 9: Driver image (from left: National Semiconductor, Diodes Incorporated, Texas Instruments)

Another challenge was to tailor the secondary optic for the MT-G component to fit within thestandard MR16 envelope and produce the proper beam angle and center beam candle power(CBCP). The baseline performance for CBCP was established from the Energy Star Integral LED
Secondary Optics
Lamp Center Beam Intensity Benchmark Tool (ed 7/6/2010). The footprint of the optic had to fit
within the heat sink opening as provided by Neng Tyi.
Another challenge was to tailor the secondary optic for the MT-G component to fit within the standard MR16 envelope
Creebeamcollaborated
partners tocandle
create secondary
optics forthebaseline
XLamp MT-G
LED thatand produce the proper
anglewithandopticalcenter-beam
power (CBCP).
The
performance
for CBCP was esfit the form factor requirements and cd/lum conversion in the design goals. Carclo Technicaltablished from the EnergyStar
21 Integral LED Lamp Center Beam Intensity Benchmark Tool (ed 7/6/2010). The footprint
Plastics Ltd created three versions of a 30mm TIR lens compatible with the XLamp MT-Gof the optic had to fit
within the
openingprovidedby NengTyi,
well as comply
component
andheat-sink
fit within the
Neng Tyias
heatsink. A custom
holderwasas
engineered
to fix the with the ANSI standard
22
optic
to
the
heat
sink
at
the
correct
opticalheight.
LEDIL
OY
providedaninnovativereflector
dimensions.
solution that fit around the MT-G component and snapped into the existing optic holder
provided by Neng Tyi for the Diamond heat sink. Photometric results for both of theseCree collaborated with
opticalto create or select secondary optics for the XLamp MT-G LED that fit the form
solutionsarepartners
shown below.
factor requirements and cd/lum conversion in the design goals. Carclo Technical Plastics Ltd, a division of Carclo plc21
provided three versions of a 30-mm TIR lens compatible with the XLamp MT-G component that fit within the Neng Tyi
heat sink. A custom holder was engineered to fix the optic to the heat sink at the correct optical height. LEDIL OY22
20
provided an innovative
solutionthat
fit aroundthe MT-G component and snapped into the existing optic holder
TI’sreflector
website/reference
designlink/etc.
http://www.ti.com/led
21

Carclo http://www.carclo-optics.com/

provided by Neng Tyi22 Ledilfor http://www.ledil.com/index.php?page=cree
their Diamond heat sink. Photometric results for both of these solutions are shown below.
2011-02-14

21
22

Cree Company Confidential

Page 13 of 18

Carclo http://www.carclo-optics.com/
Ledil http://www.ledil.com/index.php?page=cree

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

13

XLAMP MT-G MR16 REFERENCE DESIGN
AP62- MR16 Reference Design

Figure 10: Top: Neng Tyi optic holder and Ledil reflector; Bottom: Prototype SLS optic holder and Carclo TIR optic

4.

Calculate the number of LEDsOne.
The purpose of this reference design is to show that a single LED package can deliver equivalent
lighting utility and superior efficacy compared to the existing bulbs on the market. The XLamp
MT-G Tyi
EasyWhite
LED is a andmulti-chippackage bottom:
that can offer
the requiredaFigure 10: Top: Neng
optic holder
LedilLED
reflector;
PrototypeSLS CBCP
opticofholder
and Carclo TIR optic
replacement bulb with new levels of LED-to-LED color consistency and efficiency.

4.

5.
Consider allOF
designpossibilities
CALCULATE THE
NUMBERLEDS

The design possibilities for a retrofit LED MR16 bulb are endless. There are countless ways todesign the necessary heat sink that can dissipate the heat and fit within the standard MR16One.
envelope. One such heat sink was an existing design from OEM bulb manufacturer Neng Tyi
Precision Industries. There are also many ways to both drive the LED and design the optics.
The purpose of this reference
designto showfor
thata singledesign
LED package
deliverfor
equivalent
lighting utility and supeWorking withdriver iscompanies
a reference
and opticscan
companies
a customized
design,
both
were
made
to
providetheperformancenecessary
for
a
true
35W-50W
halogenrior efficacy compared to the existing bulbs on the market. The XLamp MT-G EasyWhite LED is a multi-chip LED package
MR16 replacement bulb.
that can offer the required CBCP of a replacement bulb with new levels of LED-to-LED color consistency and efficiency.

5.

However, this reference design is intended to show how straightforward it is to design with
Cree’s XLamp MT-G EasyWhite LED. This application note is not intended to show the only way
to ALLdo this,but rather demonstrate
the ease of implementation in a difficult set of engineering
CONSIDER
DESIGNPOSSIBILITIES
constraints. With a dedicated design team and resources, the solution space is large!

The design possibilities for a retrofit LED MR16 bulb are endless. There are countless ways to design the necessary heat
2011-02-14

Cree Company Confidential

Page 14 of 18

sink that can dissipate the heat and fit within the standard MR16 envelope. One such heat sink was the existing designfrom OEM bulb manufacturer Neng Tyi. There are also many ways to both drive the LED and design the optics. Working with driver companies to create reference design and optics companies to create and/or select appropriate optics,
provided the performance necessary for a true 35W – 50W halogen MR16 replacement bulb.
There are a number of desirable performance-related benefits in this design, which are part of the XLamp MT-G pack-Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

14

XLAMP MT-G MR16 REFERENCE DESIGN

age. Because the MT-G uses EasyWhite technology, LED-to-LED color consistency can be guaranteed to within four or
two McAdam ellipses (for any given CCT and depending on the order codes). The MT-G has an 80 CRI minimum and isbinned at 85° C, so the tested/binned CCT will be as faithful as possible to the system operating environment. These
are all component features that allow for new levels of specification accuracy.
However, the primary purpose of this reference design is to show how straightforward it is to design with Cree’s XLamp
MT-G EasyWhite LED. This application note is not intended to show the only way to do this but rather to demonstrate
the ease of implementation within a difficult set of engineering constraints. With a dedicated design team and resources,
the solution space is large!

6.

COMPLETE THE FINAL STEPS: IMPLEMENTATION AND ANALYSIS

In this section, Cree illustrates some of the techniques used to create a working prototype MR16 lamp using the XLamp
MT-G EasyWhite. Additionally, the photometric results of the XLamp MT-G EasyWhite-based MR16 with comparison toclassic halogen lamps will be shown.

Prototyping Details
The essence of the design is to attach a Cree XLamp MT-G EasyWhite component to a heat sink and assemble the necessary optics and driver around this to create a true 35W-50W halogen MR16 replacement. The steps of the assembly
will be detailed below.
1.

Per the details given in the MT-G data sheet, we soldered a single MT-G LED to a star-shaped metal core printed
circuit board (MCPCB) designed for the MT-G.

2.

Once the LED is soldered to the MCPCB, wire connectors are soldered to the star board for contact with the driver.

3.

A thermal epoxy is placed on the back of the MCPCB to attach to the heat sink. In this reference design, we used
Arctic Silver thermal adhesive.23

4.

The MCPCB is placed onto the heat sink with the leads placed through the thru-holes of the heat-sink base plate,
and the thermal paste is allowed to cure (allow at least 15 minutes to cure).

5.

Insert the driver board into the plastic base.

6.

The wires from the MCPCB are soldered to the driver.

7.

Depending on the optic used, there are two methods for attaching the optic to the heat sink.

8.

23

a.

The Carclo optic is assembled by snapping the optic to the custom holder.

b.

The Ledil optic is snapped into the optic holder from Neng Tyi.

c.

These assemblies can then be snapped into the heat sink over the MT-G, aligning around the MCPCB.

The assembly is now finished, and the lamp can now be powered by 12 VAC.

http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

15

XLAMP MT-G MR16 REFERENCE DESIGN

Results
Optic results:
Optic

Optic TypeBeam Angle

Carclo 10756 Narrow Frosted

TIR

27°

Carclo 10757 Medium Frosted

TIR

31°

Carclo 10758 Wide Frosted

TIR

Ledil Minnie

Optic
Reflector
Carclo 10756 Narrow Frosted
Carclo 10757 Medium Frosted
Carclo 10758 Wide Frosted
Ledil Minnie

Cd/LumEfficiency

3.2
AP62- MR16 Reference Design
1.9

42°

1.1

Optic TypeBeam Angle
38°
TIR
27°
TIR
31°
Table
TIR4: Optic test
42°data
Reflector
38°

Cd/Lum
3.2
1.9
1.1
1.4

1.4

88%
84%
81%

Efficiency
88%
84%
81%
91%

91%

Table 4: Optic test data
-180
Measured Normalized Intensity:-176-172
168172176-168
100.0%-164
160164-160
MT-G MR16
156
-156
152
-152
90.0%
148
-148
144
-144
80.0%
140
-140
136
-136
70.0%
132
-132
128
-128
60.0%
124
-124
120
-120
50.0%
116
-116
40.0%
112
-112
108
-108
30.0%
104
-104
MT-G Component
20.0%
100
-100
Carclo Narrow Frosted
96
-96
10.0%
92
-92
Carclo Medium Frosted
0.0%
88
-88
Carclo Wide Frosted
84
-84
80
-80
Ledil Minnie
76
-76
72
-72
68
-68
64
-64
60
-60
56
-56
52
-52
48
-48
44
-44
40
-40
36
-36
32
-32
28
-28
24
-24
20 16
-20
-16
12 8 4-4 -8 -120Figure 11: Goniometric Intensity Polar Plot of XLamp MT-G MR16

Figure 11: Goniometric-intensity polar plot of XLamp MT-G MR16

Description

Wattage

Current
Output (A)T_sp (°C)

Lumen

CBCP (cd)Beam Angle(°)

Energy Star
Equivalence

MT-G MR16, Carclo Narrow>35W
Frosted Optic, Diodes Inc.
7.2 W
1.08
84°C
497
1755
27°
(~43W)
Driver @1.1A
MT-G MR16, Carclo Narrow>50W
Frosted Optic, Diodes Inc.
10.1 W
1.50
103°C
611
2250
27°
(~57W)
Driver @1.5A
MT-G MR16, Ledil Minnie
Reflector, Diodes Inc. Driver
7.2 W
1.08
82°C
515
794
38°
35W
@1.1A
MT-G MR16, Ledil Minnie
Reflector,
Diodes Inc. Driver10.1 W
1.50
100°C
636
973
38°
42W
Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarks@1.5Afor informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atof Cree, Inc. This document is provided
www.cree.com. For warranty information, please contact Cree Sales atTable
sales@cree.com.
5: System test data, steady state

16

XLAMP MT-G MR16 REFERENCE DESIGN

Description

Wattage

Current

T_sp

Output

(°C)

Lumen

CBCP

Beam

Energy Star

(cd)

Angle

Equivalence

(A)

(°)

MT-G MR16, Carclo Narrow
Frosted Optic, Diodes Inc.

7.2 W

1.08

84°C

497

1755

27°

10.1 W

1.50

103°C

611

2250

27°

7.2 W

1.08

82°C

515

794

38°

10.1 W

1.50

100°C

636

973

38°

Driver @ 1.1 A
MT-G MR16, Carclo Narrow
Frosted Optic, Diodes Inc.
Driver @ 1.5 A>35 W(~43 W)>50 W(~57 W)

MT-G MR16, Ledil Minnie Reflector, Diodes Inc. Driver @

35 W

1.1 A
MT-G MR16, Ledil Minnie Reflector, Diodes Inc. Driver @
1.5 A

>35 W
(~42 W)

Table 5: System test data, steady stateAP62- MR16 Reference Design

We chose the driver from Diodes Incorporated because it was easy to modify so as to deliver 1.5 A. In this configuration,
the solder-point temperature measured ~103°C: hot, but manageable. With this driver configuration, we were able to
We chose the driver from Diodes Inc because it was easy to modify so as to deliver 1.5A. In thisachieve 50W halogenconfiguration,equivalency
on theEnergy Star
requirements.
the Carclo
Frosted TIR optic,
thebasedsolderpointtemperature
measured~103°C: hot, Using
but manageable.
ButNarrowwiththisdriverconfiguration
we
were
able
to
achieve
50W
halogenequivalency
based
on
the
we demonstrated a 50W equivalent MR16 lamp. The measured CBCP was 2250 cd, above the minimum 2044 cd required
Energy Star requirements. Using the Carclo Narrow Frosted TIR optic, we demonstrated a 50W
for a 27° beam. At the 1.5-A drive level, the lumen output was 620 lumens at steady state, with a 12.0 VAC input. Seeequivalent MR16 lamp. The measured CBCP was 2250cd, above the minimum 2044cd required
below for the beam profile
luminous
intensity
data.
for a 27°andbeam.
At the 1.5A
drive level,
the lumen output was 620 lumen at steady state, with a
12.0 VAC input. See below for the beam profile and luminous intensity data.
MT-G MR16,Carclo Narrow Optic, DiodesInc 1.5A driver

2500

Luminous Intensity

100.0%

2000

Luminous Intensity (cd)

1500
60.0%

1000

40.0%

Relative Luminous Intensity

80.0%

Viewing
Angle: 27°
500

20.0%

0

0.0%
-80

-60

-40

-20

0
Theta (°)

20

40

60

80

Figure 12 Measured Luminous Intensity of 50W equivalent MT-G MR16

Figure 12 Measured luminous intensity of 50W equivalent MT-G MR16
Conclusions

This reference design demonstrates the ease of integration of a Cree XLamp MT-G component
into
a conventional
MR16 housingwith great
results.
The design
hereutilized
properheatand XLamp are registered trademarks
Copyright © 2011 Cree, Inc. All
rightsreserved. The informationin this document
is subject
to change
without
notice.
Cree, theCree logo
of Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atsinking,
opticalcontrol
anddriverdesigninorder
toefficiently
andeffectivelyhit
thetargets
www.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.
outlines by EnergyStar as a true 35W-50W equivalent MR16. The chosen driver current andheat sinking allows for the necessary environment to achieve L70 50,000 hour designation. This17

XLAMP MT-G MR16 REFERENCE DESIGNCONCLUSIONSThis reference design demonstrates the ease of integration of a Cree XLamp MT-G component into a conventional MR16
housing with great results. The design here utilized proper heat sinking, optical control and driver design in order to efficiently and effectively hit the targets outlined by Energy Star as a true 35W – 50W equivalent MR16. We chose drivercurrent and heat sink to achieve a minimum L70 25,000-hour designation. This document is meant to show that thislevel of performance is achievable and attainable with a single MT-G component but is not meant to be interpreted as
the only way that a good LED MR16 can be designed.

SPECIAL THANKS
Cree would like to acknowledge and thank Carclo Technical Plastics Ltd a division of Carclo plc, Diodes Incorporated,
LEDIL OY, Lightech Electronic Industries Ltd., National Semiconductor Corporation, Neng Tyi Precision Industries Co.,
Ltd., and Texas Instruments Incorporated for their vision and collaboration on this reference design. The XLamp MT-G
component used in this design was an engineering prototype. Similarly, these partner companies have contributed
advanced-design prototypes that can be further optimized for improved manufacturability and performance. Pleasecontact them directly for an update on these and other thermal, driver and optical products.

Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarksof Cree, Inc. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available atwww.cree.com. For warranty information, please contact Cree Sales at sales@cree.com.

18