Energy Injection ZVS Full Bridge Converter With Extended Soft-Switching Range

Phase-shifted full-bridge (PSFB) converter is widely used in high efficiency and high power topologies due to its soft switching characteristics. However, the traditional PSFB converter is difficult to realize soft switching of the lagging-leg switches under light load, and has shortcomings such as circulating current, duty cycle loss, and secondary parasitic oscillation. The shortcoming hinders the high frequency and high efficiency of the converter. In view of the shortcomings of the traditional PSFB, this article proposes an improved topology, which uses a four-winding transformer and an auxiliary circuit to transfer the energy in the auxiliary circuit to the primary side of the transformer and realize the soft switching of the legging branch. By properly setting the capacitance value of the injection side, ZVS (Zero Voltage Switch) can be achieved in a wide range, while reducing the duty cycle loss and secondary side voltage oscillation. The detailed working principle and experimental results are given to verify the effectiveness of this method.