A phase-shift-based synchronous rectification scheme for bi-directional high-step-down CLLC resonant converters

A frequency-modulated bi-directional CLLC resonant converter with high-step-down feature designed for power-to-gas applications is presented. To avoid magnetizing current being provided from low voltage side, which causes remarkable conduction loss and current stress in a high-step-down design, a novel synchronous rectification scheme based on small phase shift technique is proposed. The switching transient under the proposed scheme is analyzed, which indicates that the reactive current of low-voltage side can be eliminated when the switching frequency equals the resonant one. Furthermore, the steady-state characteristics of the converter are discussed. A prototype is built, and experimental results have verified the principles and the benefits of the proposed scheme.