A New Synchronous Rectifier Control Method for High Efficiency Phase-Shifted Full-Bridge Converter with Coupled Inductor Rectifier

A new synchronous rectifier (SR) control method for phase-shifted full-bridge (PSFB) converter with coupled inductor rectifier (CIR) is proposed in order to achieve high efficiency over wide output voltage range. The key operation of the proposed control method is to turn on the SR earlier than the conventional method in which SR is operated as a diode. By using the proposed SR control method, the primary circulating current can be rebuilt-up, and the circulating current is used to achieve zero-voltage switching (ZVS) of the primary legging-leg switches. Therefore, since the magnetizing inductance of the transformer can be designed large, the conduction loss and the switch turn-off loss on the primary side can be reduced. As a result, the proposed SR control method achieves high efficiency over a wide output voltage range. The proposed method is verified by using prototype converter at 400 V input and 27-54 V/13 A output condition.