www.ti.com

Description

Test Report: PMP22650

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger
Reference Design

1 Description
The PMP22650 reference design is a 6.6-kW, bidirectional, onboard charger. The design employs a two-phase
totem pole PFC and a full-bridge CLLLC converter with synchronous rectification. The CLLLC utilizes both
frequency and phase modulation to regulate the output across the required regulation range. The designuses a single processing core inside a TMS320F28388D microcontroller to control both the PFC and CLLLC.
Synchronous rectification is implemented via the same microcontroller with Rogowski coil current sensors. Highdensity is achieved through the use of high-speed GaN switches (LMG3522). The PFC is operating at 120 kHz
and the CLLLC runs with a variable frequency from 200 kHz to 800 kHz. A peak system efficiency of 96.5% wasachieved with an open-frame power density of 3.8 kW/L.
While the design calculations were done for a 6.6-kW output power, the design represents a suitable starting
point for a 7.x-kW (for example, 7.2-kW to 7.4-kW) rated OBC operating from a 240-V input with a 32-A breaker.

Figure 1-1. OBC Front View

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

1

Test Prerequisites

www.ti.com

Figure 1-2. OBC Back View

Figure 1-3. Simplified Schematic

2 Test Prerequisites
2.1 Voltage and Current Requirements
Table 2-1. Voltage and Current Requirements
Parameter

Min

TypMaxUnits

AC Input Voltage

90240

264

V32A

250400450

V

DC Output Current (Constant Currentmode)

20A

DC Output Power (Constant Powermode), VIN > 210 VRMS

6.6kW

AC Input Current
DC Output Voltage

2GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

TIDT249 – SEPTEMBER 2021Submit Document Feedback

www.ti.com

Test Prerequisites

2.2 Required Equipment••••

240 VAC, 7 kW AC source
250 V to 450 V, 6.6 kW DC load
12 V, 2 A bias supply
Refrigerated recirculating chiller

2.3 Dimensions
Total volume: 105.8 in3•••

Red region– All top-side components except output bulk capacitors– 113 mm × 241 mm × 50 mm
Blue region– Output bulk capacitors– 113 mm × 30 mm × 52 mm
Green region– PCB and bottom-side components– 113 mm x 271 mm x 6.4 mm

Figure 2-1. Solution Dimensions

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated3

Test Results

www.ti.com

3 Test Results
The power density achieved in this design is 3.8 kW/L (62.5 W/in3). The total system efficiency is 96.5%. ThePFC has an efficiency of 98.5% and the CLLLC is 98%.

3.1 Efficiency
Efficiency data is provided in the following graphs with and without 12-V bias power. The bias supplies power tocontrol, isolators, and gate drive. The graph in Figure 3-1 was taken under the following conditions:•••

VIN,RMS = 240 V
VOUT = 400 V
Coolant Temperature: 20°C

Figure 3-1. PFC Efficiency
The graph in Figure 3-2 was taken under the following conditions:•••

VIN = 400 V
VOUT = 350 V
Coolant Temperature: 20°C

Figure 3-2. CLLLC Efficiency4GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

www.ti.com

Test Results

The graph in Figure 3-3 was taken under the following conditions:•••

VIN,RMS = 240 V
VOUT = 350 V
Coolant Temperature: 20 °C

Figure 3-3. System Efficiency

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated5Test Results

www.ti.com

3.2 System PerformanceThe following figures summarize the total system efficiency, system losses, total harmonic distortion (THD), andthe normalized output voltage regulation accuracy.
The power density achieved in this design is 3.8 kW/L (62.5 W/in3). This comes with a total system efficiencyof 96.5%. Loads above 1.5 kW have a THD < 5% and the regulation accuracy of the output voltage is roughly
within ±0.06%.
The graphs in Figure 3-4 use the following conditions:•••

VIN,RMS = 240 V
VOUT = 350 VCoolant Temperature: 20 °CFigure 3-4. System Performance

6GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

www.ti.com

Test Results

3.3 Bode Plots
The following bode plots were acquired using the onboard software frequency response analyzer inside theTMS320F28388D microcontroller. The load used in the tests was configured as a constant current sink. The
microcontroller is configured to regulate a constant output voltage. The bandwidth is roughly from 1 kHz to 2.5
kHz with a phase margin in excess of 45°.

Figure 3-5. Voltage Loop Bode Plot

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

7

Test Results

www.ti.com

The following bode plots were acquired using the onboard software frequency response analyzer inside theTMS320F28388D microcontroller. The load used in the tests was configured as a constant voltage. The
microcontroller is configured to regulate a constant output current. The bandwidth is roughly from 1 kHz to
2.5 kHz with a phase margin in excess of 60°.

Figure 3-6. Voltage Loop Bode Plot (Constant Voltage Load)

8GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

www.ti.com

Test Results

3.4 Efficiency and Regulation Data
The following table shows efficiency and regulation data.
VOUT (V)IOUT (A)

POUT (W)

VIN (V)IIN (A)

PIN (W)

VBIAS (V)IBIAS (A)PBIAS (W)Eff (%) NoBias

Eff (%)
With Bias

352.760.5

177.35240.121.17

215.36

11.92

1.24

14.73

82.35

77.08

352.741

354.12240.051.79

391.84

11.92

1.23

14.67

90.37

87.11

352.721.5

530.65239.982.49

572.25

11.92

1.24

14.8

92.73

90.39

352.71

2

706.27239.913.23

753.97

11.92

1.24

14.78

93.67

91.87

352.7

2.5

882.52239.843.97

936.83

11.92

1.24

14.76

94.2

92.74

352.7

3

1058.9239.764.72

1118.95

11.92

1.23

14.71

94.63

93.41

352.7

3.5

1235.3239.695.48

1301.58

11.92

1.23

14.65

94.91

93.85

352.6941411.74

239.626.23

1484.44

11.92

1.23

14.61

95.1

94.18

352.694.5

1587.99239.55

6.99

1667.43

11.92

1.22

14.57

95.24

94.41

352.695

1763.62239.477.75

1849.94

11.92

1.22

14.51

95.33

94.59

352.695.5

1939.96

239.4

8.51

2031.56

11.93

1.21

14.48

95.49

94.82

352.6962116.85239.329.27

2212.59

11.93

1.21

14.48

95.67

95.05

352.686.5

2293.18

239.2510.02

2392.72

11.93

1.21

14.46

95.84

95.26

352.6872469.51

239.1710.78

2572.43

11.93

1.21

14.4

96

95.46

352.677.5

2645.17

239.1

11.53

2751.5

11.93

1.19

14.16

96.14

95.64

352.6882821.8239.0212.29

2931.48

11.94

1.16

13.85

96.26

95.81

352.698.5

2998.24238.9513.04

3111.5

11.94

1.14

13.56

96.36

95.94

352.7193174.78238.8713.8

3292.5

11.95

1.11

13.26

96.43

96.04

352.729.5

3350.46238.7914.56

3472.6

11.95

1.09

12.99

96.48

96.12

352.76103527.33238.7115.33

3654.7

11.95

1.07

12.76

96.51

96.18

352.7910.5

3704.19238.6316.09

3837.211.96

1.05

12.52

96.53

96.22

352.84113881.08238.5416.87

4020.3

11.96

1.03

12.37

96.54

96.24

352.9111.5

4058.4238.4617.64

4204.2

11.96

1.02

12.24

96.53

96.25

352.92124235

238.3718.42

4387.9

11.96

1.02

12.16

96.51

96.25

352.93

12.5

4411.3238.2819.2

4571.5

11.96

1.01

12.08

96.5

96.24

352.96134588.2238.18

19.98

4756

11.96

1

12

96.47

96.23

352.9913.5

4765.1238.0920.77

4940.9

11.96

1

11.92

96.44

96.21

353

14

4941.9237.9921.55

5125.811.97

0.99

11.86

96.41

96.19

353.0214.5

5118.9237.8922.34

5311.4

11.97

0.99

11.79

96.38

96.16

353.02155294.8237.7923.13

5496.4

11.97

0.98

11.73

96.33

96.13

353.0215.5

5471.6

237.6823.92

5682.4

11.97

0.98

11.69

96.29

96.09

353.03165648.3237.6224.71

5868.9

11.97

0.97

11.64

96.24

96.05

353.0516.55825.2237.5125.51

6056.1

11.97

0.97

11.59

96.19

96

353.0217.5

6176.6237.2627.13

6432.3

11.97

0.96

11.52

96.03

95.85

353.02

186353.2

237.1427.94

6621.6

11.97

0.96

11.49

95.95

95.78

353.0318.5

6529.8237.0128.76

6812.2

11.97

0.96

11.47

95.85

95.69

353.05196706.8

236.8729.59

7004.3

11.97

0.96

11.44

95.75

95.6

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference Design
Copyright © 2021 Texas Instruments Incorporated

9

Test Results

www.ti.com

3.5 Thermal Data
The following image is taken under full load operation. All of the significant heat generation components areconnected to the cold plate on the bottom side of the board. The hottest components visible in this image comefrom the common-mode inductors in the EMI filter. These parts have no access to the cold plate and receive alltheir cooling via the ambient air.

Figure 3-7. Top Side Thermal ImageGaN FET temperatures are provide by means of the onboard temperature sensors inside the LMG3522 devices.
Under full load conditions, all FET temperatures are less than 75°C.
Table 3-1 lists the GaN FET temperature measurements under the following conditions:•••

VIN,AC: 240 VVDC,LINK: 400 V
Coolant temperature: 33°C
Table 3-1. GaN FET Temperature Measurements

10GaN FET

Temperature (°C)

PFC

66.8

CLLLC Primary (350 V/19 A)

58.1

CLLLC Secondary (350 V/19 A

59.5

CLLLC Primary (300 V/19 A)

61.0

CLLLC Secondary (300 V/19 A)

74.0

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

www.ti.com

Test Results

Figure 3-8 shows the critical transformer temperatures under the following conditions:••

Coolant Temperature: 33°C
Transformer temperature measurement locations– PRI 1 - Measured on the inside surface of the primary winding– PRI 2 - Measured on the outside surface of the primary winding– SEC 1 - Measured on the inside surface of the secondary winding– SEC 2 - Measured on the outside surface of the secondary winding– CORE 1 - Measured on the top of the core center leg– CORE 2 - Measured on the bottom of the core center leg– CORE 3 - Measured on the side of the core
– CORE 4 - Measured on the top of the coreFigure 3-8. CLLLC Transformer Temperatures

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

11

Waveforms

www.ti.com

4 Waveforms
4.1 PFC Waveforms
Figure 4-1 shows the PFC input voltage and input current waveform measured at the following parameters:••

Traces– C2: VIN
– C4: IIN
Conditions– VIN = 208 V– VOUT = 400 V– ROUT = 43 Ω

Figure 4-1. PFC Input Voltage and Input Current

12GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

www.ti.com

Waveforms

Figure 4-2 shows the PFC GaN drain voltage waveform measured at the following parameters:••

Traces– C1: GaN Switch Node Drain Voltage– C2: VIN
– C4: IIN
Conditions– VIN = 208 V– VOUT = 400 V– ROUT = 43 Ω

Figure 4-2. PFC GaN Drain Voltage

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

13

Waveforms

www.ti.com

A zoom-in of the GaN switch drain-to-source voltage transition is shown to be approximately 20 ns in Figure 4-3.
This rapid transition comes from the low COSS of the LMG3522.
The waveform in Figure 4-3 was measured using the following parameters:••

Traces– C1: GaN Switch Node Drain Voltage– C2: VIN
– C4: IINConditions– VIN = 208 V– VOUT = 400 V– ROUT = 43 ΩFigure 4-3. PFC GaN Drain Voltage - Transition

14GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

www.ti.com

Waveforms

4.2 CLLLC Waveforms
Figure 4-4 shows CLLLC operation at 19 A (6.6 kW) under the following parameters:••

Traces– C1: GaN Primary Switch Node Drain Voltage– C2: GaN Secondary Switch Node Drain Voltage– C3: Transformer Primary Current– C4: Transformer Secondary Current
Conditions– VIN = 400 V– VOUT = 350 V– IOUT = 19 A

Figure 4-4. CLLLC Operation 19 A (6.6 kW)

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

15

Waveforms

www.ti.com

Figure 4-5 shows CLLLC operation at 10 A and the following parameters:••

Traces– C1: GaN Switch Node Drain Voltage Leg 1– C2: GaN Switch Node Drain Voltage Leg 2– C3: Transformer Primary Current– C4: Transformer Secondary Current
Conditions– VIN = 400 V– VOUT = 350 V– IOUT = 10 A

Figure 4-5. CLLLC Operation 10 A

16

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

www.ti.com

Waveforms

A zoom-in of the GaN switch drain-to-source voltage transition is shown to be approximately 40 ns in Figure 4-6.
This rapid transition comes from the low COSS of the LMG3522.
The waveform in Figure 4-6 is measured using the following parameters:••

Traces– C1: GaN Switch Node Drain Voltage Leg 1– C2: GaN Switch Node Drain Voltage Leg 2– C3: Transformer Primary Current– C4: Transformer Secondary Current
Conditions– VIN = 400 V– VOUT = 350 V– IOUT = 10 A

Figure 4-6. CLLLC Operation 10 A - GaN FET Transitions

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated17Waveforms

www.ti.com

The waveform in Figure 4-7 is measured using the following parameters:••

Traces– C1: GaN Switch Node Drain Voltage Leg 1– C2: GaN Switch Node Drain Voltage Leg 2– C3: Transformer Primary Current– C4: Transformer Secondary Current
Conditions– VIN = 400 V– VOUT = 350 V– IOUT = 2 AFigure 4-7. CLLLC Operation 2 A18

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference DesignCopyright © 2021 Texas Instruments Incorporated

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

www.ti.comWaveforms

A zoom-in of the GaN switch drain-to-source voltage transition is shown to be approximately 75 ns in Figure 4-8.
This rapid transition comes from the low COSS of the LMG3522. The slightly longer transition time in this image
comes from the lighter load condition and the resulting reduced current flow.
The waveform in Figure 4-8 is measured using the following parameters:••

Traces– C1: GaN Switch Node Drain Voltage Leg 1– C2: GaN Switch Node Drain Voltage Leg 2– C3: Transformer Primary Current– C4: Transformer Secondary CurrentConditions– VIN = 400 V– VOUT = 350 V– IOUT = 2 A

Figure 4-8. CLLLC Operation 2 A - GaN FET Transitions

TIDT249 – SEPTEMBER 2021
Submit Document Feedback

GaN-Based, 6.6-kW, Bidirectional, Onboard Charger Reference Design
Copyright © 2021 Texas Instruments Incorporated

19

IMPORTANT NOTICE AND DISCLAIMER
TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATA SHEETS), DESIGN RESOURCES (INCLUDING REFERENCEDESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”
AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANYIMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRDPARTY INTELLECTUAL PROPERTY RIGHTS.
These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate
TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicablestandards, and any other safety, security, regulatory or other requirements.
These resources are subject to change without notice. TI grants you permission to use these resources only for development of an
application that uses the TI products described in the resource. Other reproduction and display of these resources is prohibited. No license
is granted to any other TI intellectual property right or to any third party intellectual property right. TI disclaims responsibility for, and you
will fully indemnify TI and its representatives against, any claims, damages, costs, losses, and liabilities arising out of your use of theseresources.
TI’s products are provided subject to TI’s Terms of Sale or other applicable terms available either on ti.com or provided in conjunction withsuch TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable warranties or warranty disclaimers for
TI products.
TI objects to and rejects any additional or different terms you may have proposed. IMPORTANT NOTICE
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2022, Texas Instruments Incorporated