An Improved ZVZCS PWM FB DC/DC Converter Using the Modified Energy Recovery Snubber

Abstract—The conventional high-frequency phase-shifted zero-voltage-switching (ZVS) full-bridge dc/dc converter has a disad-vantage, in that a circulating current flows through transformer and switching devices during the freewheeling interval. Due to this circulating current, rms current stress, conduction losses of the transformer and switching devices are increased. To alleviate this problem, this paper proposes an improved zero-voltage zero-cur-rent switching (ZVZCS) phase-shifted full-bridge (FB) dc/dc con-verter with a modified energy-recovery snubber (ERS) attached at the secondary side of transformer. Also, the small signal model of the proposed ZVZCS FB dc/dc converter is derived by incor-porating the effects introduced by a transformer leakage induc-tance and an ERS to achieve ZVZCS. Both analysis and exper-iment are performed to verify the proposed topology by imple-menting a 7-kW (120 Vdc, 58 A) 30-kHz insulated-gate-bipolar-transistor-based experimental circuit Index Terms—Energy-recovery snubber, full-bridge (FB) dc/dc converter, small-signal modeling, zero-voltage switching (ZVS), zero-voltage zero-current switching (ZVZCS). I