A New Phase-Shifted Full-Bridge Converter With Maximum Duty Operation for Server Power System

Anew high-efficient phase-shifted full-bridge (PSFB) converter is proposed in this paper. The conventional PSFB converter with an external inductor and clamping diodes is widely used in server power systems due to limited voltage stress on switches and its zero-voltage switching (ZVS) characteristics. However, a hold-up time regulation rule in server systems limits its operating duty ratio in nominal state and it increases the conduction loss of the converter. With simple modification, the proposed converter can be operated in the optimal operating point, 50% duty ratio, both in nominal operating condition and hold-up time condition. The ZVS characteristic is still maintained in the proposed converter. Therefore, conduction loss at the primary side of the converter is reduced and higher efficiency can also be obtained in the proposed converter than the conventional converter. The operational principle and analysis of the proposed converter are presented and verified by the 1-kW prototype.