Control Technique for Wide-Range ZVS of Bidirectional Dual-bridge Series Resonant dc-dc Converters

This paper describes a control technique for wide-range zero-voltage switching (ZVS) implementation of bidirectional dual-bridge series resonant dc-dc converters (DBSRCs). The proposed control technique integrates variable frequency modulation(VFM) and phase shift modulation (PSM), in which the former effectively achieves ZVS operation at nonunity voltage conversion ratio, while the latter contributes to output power extension when the ratio is close to unity. The proposed VFM technique is built on the time-domain analysis of ZVS condition. A closed-form solution is formulated which guarantees sufficient ZVS commutation current at switching instants, accounting for the presence of switches parasitic and/or snubber capacitances. Effectiveness of the proposed technique is verified by means of a 700 W experimental prototype, indicating efficiency enhancement over minimum rms current trajectory (MCT) modulation.