Underresonant Modulation Scheme for Dual-Bridge Series-Resonant Converter

This article proposes an underresonant modulation (URM) scheme for the dual-bridge series-resonant converter to achieve full-load-range zero voltage switching (ZVS) over various voltage gains. Compared with the traditional overresonant modulation, the proposed URM scheme can not only provide a larger ZVS range for the circuit but also effectively reduce the size of the resonant tank in applications where the voltage gain varies in a wide range. For an optimized peak current, the Karush-Kuhn-Tucker conditions are applied to derive the closed-form solution for the control variables. Based on the analytical results, a multimode URM scheme is offered to reduce the current stress on power devices, and achieve full soft-switching operation while simplifying the closed-loop control. The developed approach is validated on a 2-kW dual-bridge series-resonant converter (DBSRC) prototype whose output voltage varies from 250 to 500 V.