High-power-factor soft-switched DC power supply system

This paper proposes a dc power supply system to give high power factor and low current distortion on the rectifier side and provide stable dc voltage on the isolated dc/dc converter side. The proposed dc power supply system uses a new ZVS strategy to get ZVS function. Besides operating at constant frequency, all semiconductor devices operate at soft-switching without additional voltage stress. A significant reduction in the conduction losses is achieved, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path, and the rectifier in the proposed dc power supply system uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. An average-current-mode control is employed in proposed dc power supply system to detect the transition time and synthesize a suitable low harmonics sinusoidal waveform for the input current. A design example of 1000 W soft-switching single-phase dc power supply system is examined to assess the converter performance.