Improvement of characteristics of active-clamped ZVS forward converter with a synchronous rectifier for high efficiency

For power supplies of communication system, we propose an active-clamped zero-voltage-switching (ZVS) forward converter with a synchronous rectifier. This converter was designed and fabricated, and the power conversion efficiency was compared with a conventional forward converter having a reset winding with synchronous rectifiers. Here, they were operated on the conditions of input voltage of DC 48 V, output voltage of 5 V, output current of 10 A and switching frequency of 120 kHz. As a measurement result, the conversion efficiency of the proposed converter was 90.6 % and it was average 3.1 % higher than the conventional forward converter having a reset winding with synchronous rectifiers. If major components of a converter are carefully chosen by considering the switching characteristics and the driving circuit for ZVS is more stabilized, this proposed converter can be used to realize the converter with output voltage lower than 3.3 V, higher conversion efficiency, and higher output current.