SLUP412 February   2022 LMG3522R030-Q1

 

  1. 1 Introduction
  2. 2 Comparing Different Technologies
  3. 3 Advantages of Integrating the Driver With GaN FETs
  4. 4 The GaN-Based 6.6-kW OBC Reference Design
  5. 5 PFC Stage
  6. 6 DC/DC Stage
  7. 7 DC/DC Topology Selection
  8. 8 Frequency Selection
  9. 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

8 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.