Wide-Range ZVS Control Technique for Bidirectional Dual-Bridge Series-Resonant DC-DC Converters

For high-voltage and high-power bidirectional dc-dc converters, soft switching of all active power devices is mandatory to ensure the high efficiency and reliability. This paper describes a control technique for wide-range zero-voltage switching (ZVS) implementation of dual-bridge series-resonant dc-dc converters. The proposed control technique integrates variable-frequency modulation (VFM) and phase-shift modulation (PSM), in which the former effectively achieves the ZVS for both step-down and step-up operation, while the latter is employed to further extend the power transmission capability. The proposed technique is built on the time-domain analysis of the ZVS condition. A closed-form solution is formulated that guarantees the sufficient ZVS commutation current at switching instants, accounting for the presence of switches parasitic and/or snubber capacitances, while maintains the rms tank current at near-to-minimum levels. Furthermore, a compensation strategy for the effect of conduction losses is presented achieving better switching behavior and higher efficiency. Compared with the minimum rms current trajectory modulation, lower switching losses, enhanced efficiency, and mitigated voltage ringings are obtained. Effectiveness of the proposed technique is verified by means of a 800 W experimental prototype. Closed-loop operation with the proposed VFM+PSM controller is also implemented and experimentally tested.