Synchronous Rectification Method for High Frequency CLLC Resonant Cnverter

Abstract

CLLC resonant converter employing wide bandgap devices requires a synchronous rectification (SR) to obtain high power conversion efficiency. Conventional SR methods for the CLLC resonant converter have a duty loss to prevent turn-on and-off switching failure in the SR operation. Especially, turn-on duty loss cannot be avoided to prevent the turn-on switching failure during the discontinuous conduction mode (DCM) operation. The proposed SR method uses the transformer voltage reflected on the third winding and the forward voltage drop of the rectifier, which can minimize the duty loss during the turn-on period. In addition, it can operate during the continuous conduction mode (CCM) as well as the DCM. The operational principles are introduced to design and to implement the proposed SR circuit. Simulation and experimental results verify the performance of the proposed SR method a 40 W prototype bidirectional CLLC resonant converter.