High‑voltage gain bidirectional two‑switch active‑clamp forward‑flyback converter for low‑voltage DC‑DC converter for electric vehicles

Jin-Hong Kim; Sang-Kyoo Han

High‑voltage gain bidirectional two‑switch active‑clamp forward‑flyback converter for low‑voltage DC‑DC converter for electric vehicles

Jin-Hong Kim

Sang-Kyoo Han

Vol. 25, No. 11, pp. 1993-2004, Nov. 2025

10.1007/s43236-025-01172-5

Electric Vehicles

High-voltage gain

Low-voltage DC-DC converter

Start-up operation

Two switch activeclamp forward-flyback converter

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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Cite this article

[IEEE Style]

J. Kim and S. Han, "High‑voltage gain bidirectional two‑switch active‑clamp forward‑flyback converter for low‑voltage DC‑DC converter for electric vehicles," Journal of Power Electronics, vol. 25, no. 11, pp. 1993-2004, 2025. DOI: 10.1007/s43236-025-01172-5.

[ACM Style]

Jin-Hong Kim and Sang-Kyoo Han. 2025. High‑voltage gain bidirectional two‑switch active‑clamp forward‑flyback converter for low‑voltage DC‑DC converter for electric vehicles. Journal of Power Electronics, 25, 11, (2025), 1993-2004. DOI: 10.1007/s43236-025-01172-5.