(A) new synchronous rectifier (SR) control method for high efficiency phase-shifted full-bridge converter with coupled inductor rectifier for LED driver

Abstract

A new synchronous rectifier controller method for phase-shifted full-bridge (PSFB) converter with coupled inductor rectifier (CIR) is proposed in order to achieve high efficiency of LED driver with wide output voltage range. The proposed synchronous rectifier (SR) control method can rebuild-up the circulating current on the primary side by operating the SR earlier than the conventional SR control method, 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 can achieve high efficiency over a wide output voltage range. The proposed control method is verified by using prototype converter at 400 VDC input and 350-700 W (27-54 V / 13A) output.