Journal of Power Electronics

The Korean Institute of Power Electronics (전력전자학회)
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High-voltage gain bidirectional two-switch active-clamp forward-flyback converter for low-voltage DC-DC converter for electric vehicles

  • Jin‑Hong Kim (Power Electronics System Laboratory, POESLA, College of Creative Engineering, Kookmin University) ;
  • Sang‑Kyoo Han (Power Electronics System Laboratory, POESLA, College of Creative Engineering, Kookmin University)
  • Received : 2025.08.11
  • Accepted : 2025.08.27
  • Published : 2025.11.20
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Abstract

This paper proposes a method to eliminate the precharge circuit in a battery disconnection unit (BDU) for separating the high-voltage (HV) battery and HV link capacitor of electric vehicles via a bidirectional operation using a low-voltage DC-DC converter. The method involves charging the HV link capacitor to the HV battery voltage and connecting the HV battery via the BDU. This method suppresses the inrush current, eliminating the need for a separate precharge circuit. A two-switch active-clamp forward-flyback converter is employed, given the increase in HV battery voltages. In the backward operation, this converter exhibits operational characteristics similar to those of current-fed topologies. which have start-up and voltage spike problems. A higher voltage gain is required due to the wide input-output range. This paper presents an active-clamp snubber to resolve start-up and voltage spike problems and proposes a voltage doubler structure based on the switching modulation of the HV side to achieve higher voltage gain. Experimental results for an 840 W prototype operating at HV battery voltages of 320-840 V and low-voltage battery voltages of 12-15.1 V are presented to verify the feasibility of the proposed method, which achieved a peak efficiency of 92.93%.

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References

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