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

Frequency Selection

Raising the frequency of a switched-mode power supply results in a size reduction of many of the reactive components. The transformer is typically the largest single component in the DC/DC converter, and its physical size is highly dependent on operating frequency. The high efficiency of a GaN switch at elevated frequencies is the fundamental tool for reducing solution size.

Figure 8-1 shows how the operating frequency affects the transformer volume in a CLLLC converter. The transformer volume is normalized to the volume at 100 kHz, which means that at 500 kHz, the volume of the transformer should be about 35% of what a 100-kHz design would be. This enormous volumetric reduction means that designers will need to consider a few other factors before deciding on the exact switching frequency.

GUID-20220218-SS0I-S9ZH-NCZH-STLQPJSX77SP-low.png Figure 8-1 Transformer volume vs. frequency.