Soft-Switching PWM DC-DC Converter with Reduced Circulating Current

Abstract

Soft-switching phase-shifted PWM converters have been attracted much attention because of their low switching losses, constant frequency operation and simple control. However, a circulating current flows through the transformer and the primary bridge circuit during the freewheeling interval, resulting in relatively high current stresses for the transformer and switching devices compared with those of conventional hard-switching PWM converters.
This paper presents an improved soft-switching PWM DC-DC converter which can substantially reduce the circulating current by employing a tapped inductor for output low-pass filter. The principle of operation and the role of the tapped inductor are illustrated. The effectiveness of the tapped inductor is evaluated through simulating analysis. Moreover, a 500W-100kHz prototype converter is implemented to demonstrate the excellent performances of both low switching and low conduction losses.