The Mechanism and Optimized Research on the RC Snubber Circuit in Phaseshifted Full-Bridge ZVS Converter

Phase-shifted full-bridge ZVS converter has been widely used in high power application as a result of high efficiency and ease of control. Since high voltage stress through rectifier diodes, snubber circuit is needed to ensure performance of the system. Therefore, converter with RC snubber circuit in some cases becomes third-order unstable system, which leads to resonance close to switching frequency and even higher voltage stress through diodes. In this paper, equivalent circuit model during the energy transfer mode of phase-shifted full-bridge ZVS converter is established, mechanism of how the RC circuit effect stability of the system and principle of how circuit parameters affect the oscillation are revealed. Not only the voltage stress of rectifier diodes in the transformer secondary side can be inhibited, but also the oscillation brought by RC circuit can be solved from the proposed appropriate parameters selecting method of RC snubber circuit. In addition the efficiency of the whole system can be improved. A prototype of 3.2 kW(10 A, 320 V) is designed to verify the theoretical analysis.