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

9 Core Loss

Controlling transformer core loss is a priority, especially high-frequency transformers. Equation 2, the Steinmetz equation, shows the relationship between loss density in the core and frequency:

Equation 2. P F E = k   f α B P K β

where PFE is the loss per unit volume; ƒ is the excitation frequency; BPK is the peak flux density in the core; k, α and β are material constants.

From Equation 2, it is apparent that as the frequency increases, so will the losses. The losses in modern magnetic materials start to become difficult to manage when the switching frequency goes much above 1 or 2 MHz.