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

1 Introduction

Server power SMPS modules must be able to operate normally not only with AC input voltage, but also with DC input voltage (battery power). When the DC input voltage is applied, the polarity is sometimes reversed (live terminal (-) voltage, neutral terminal (+) voltage). In this case, the slow switch high-side FET turned on, but the existing charge pump circuit cannot generate the VDD voltage (this does not switch because this is referenced to the opposite DC input), so the high-side FET cannot be turned on. The current flows to the parasitic diode, causing heat generation and reduced efficiency. Therefore, an appropriate IC and external circuit design is needed to make sure of stable operation.