A New Half Bridge Converter for the Personal Computer Power Supply

A new half bridge converter for the personal computer (PC) power supply is proposed in this paper. Generally, PC power supply has two unique input/output specifications which are wide input voltage range and long hold up time. Therefore, it has to be operated with a small duty ratio. That makes it difficult to apply ZVS PWM topology to the PC power supply. The proposed ZVS half bridge converter controls the primary current which flows through blocking capacitor with an auxiliary switch of the secondary side. As a result, it can ensure zero DC offset of the magnetizing current even if it is operated with a small duty ratio. Moreover, ZVS conditions are maintained by reflected load current without disturbance due to the DC offset of the magnetizing current. Therefore, it shows a high efficiency and a low EMI at the PC power specifications. The operational principle, analysis and design of the proposed converter will be presented. Experimental results demonstrate that the proposed converter can achieve a significant efficiency improvement in a 280W (12V, 23.3A) prototype converter.