SDAA026 June   2025 TPSI3052

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Using a Solid-State Relay as an Isolated 15V Supply
  6. 3Topology of Totem Pole PFC for Applying Turn On Switch
  7. 4Original Implementation for Driving PFC Slow Switch at High-side and Low-side
  8. 5Achieving Performance for Driving PFC Slow Switch at High-side and Low-side
  9. 6Test Results Comparing Before and After for High-side Implementation
  10. 7Summary
  11. 8References

3 Topology of Totem Pole PFC for Applying Turn On Switch

A basic totem-pole PFC structure is shown in Figure 3-1. Note that Q3, Q4 and the inductor consist of a boost converter. Based on VAC polarity, Q3 and Q4 alternately work as a PFC main switch or sync switch. During a positive VAC cycle, Q4 is the main switch, while Q3 works as a sync FET. The driving signals for Q3 and Q4 are complementary: Q4 is controlled by the duty cycle (D) from the control loop, while Q3 is controlled by 1 – D. During a negative VAC cycle, the function of Q4 and Q3 is swapped where Q3 becomes the main switch, and Q4 works as a sync FET. The driving signals for Q3 and Q4 are still complementary, but Q3 is now controlled by D while Q4 is controlled by 1 – D. Because of the reverse recovery issue, a regular MOSFET cannot be used in a continuous-conduction mode (CCM) totem-pole PFC, therefore, Q3 and Q4 need to be gallium nitride (GaN) FETs, which have no reverse recovery. Q1 and Q2 diodes are paralleled with regular MOSFETs to further improve efficiency.

Basic Totem Pole PFC Circuit Structure Figure 3-1 Basic Totem Pole PFC Circuit Structure