Time-Domain Analysis of Full-Bridge Series-Resonant Converter and Boundary Conditions for DCM Operation

In this study the operating regions of the DC-DC full-bridge LC-series resonant converter are obtained using time-domain analysis. The conditions to achieve zero-voltage and zero-current switching (ZVS and ZCS) are deduced and the minimization of losses during hard-switching are discussed. In addition, the boundary condition between continuous and discontinuous current mode (CCM and DCM) is derived, as a function of the switching frequency and the load. The analysis is verified by simulations and laboratory measurements, for a small-scale high-frequency converter. Finally, a potential weakness of ZCS is discussed, and a comparison between MOSFET and IGBT semiconductors is performed with respect to the losses.