SLUP412 February   2022 LMG3522R030-Q1


  1. Introduction
  2. Comparing Different Technologies
  3. Advantages of Integrating the Driver With GaN FETs
  4. The GaN-Based 6.6-kW OBC Reference Design
  5. PFC Stage
  6. DC/DC Stage
  7. DC/DC Topology Selection
  8. Frequency Selection
  9. Core Loss
  10. 10Loss of ZVS
  11. 11Dead Time
  12. 12ISR Bandwidth
  13. 13Overall
  14. 14Resonant Tank Design
  15. 15Thermal Solution
  16. 16Layout Best Practices
  17. 17Control-Loop Considerations
  18. 18Conclusions
  19. 19References
  20. 20Important Notice

The GaN-Based 6.6-kW OBC Reference Design

The GaN-Based 6.6-kW Bidirectional Onboard Charger Reference Design [2] supports operation from a universal single-phase input off the AC grid and provides full output power (6.6 kW) to the load at an input voltage of 208 VAC and above. Below this input voltage level, the output power is linearly derated. The main target of this reference design is to deliver the maximum possible power to the battery, with a power density level greater than 60 W/inch3 (3.66 kW/L) and a battery voltage range between 250 V and 450 V. Additionally, this OBC design supports bidirectional operation. Table 4-1 lists the power-supply specifications.

Table 4-1 Power-supply specification for the 6.6-kW OBC reference design.
Parameter Description Minimum Typical Maximum Units
AC input voltage 90 220 264 VRMS
AC input current 32 ARMS
DC output voltage 250 400 450 V
DC output current (CC mode) 20 A
DC output power (CP mode) 6.6 kW
Power density 60 W/inch3
EMI compliance level CISPR 32, Class B [9]
AC line frequency 47 63 Hz
Power factor (full load) 0.99
Cold-plate coolant temperature 65 85 °C

Figure 4-1 is a block diagram of the 6.6-kW OBC reference design.

GUID-20220218-SS0I-PN07-WFTF-HC3NZLQZNPPJ-low.png Figure 4-1 Block diagram of the 6.6-kW OBC reference design.

Both the PFC stage and the DC/DC converter leverage 30-mΩ automotive-qualified 650-V LMG3522R030-Q1 GaN FETs for control by a single C2000™ TMS320F28388D real-time microcontroller (MCU). In total, the converters use 12 GaN FETs; the low-frequency FETs for the bridgeless input rectifier are regular silicon MOSFETs.