Design Procedure for High-Frequency Operation of the Modified Series-Resonant APWM Converter to Reduce Size and Circulating Current

In this paper, a generalized analysis for the auxiliary network in a modified series-resonant asymmetrical pulse-width-modulated (APWM) converter is performed to produce a design procedure that ensures that zero voltage switching (ZVS) is achieved for any series-resonant APWM converter design. New equations that correctly predict the magnitude of auxiliary current are obtained by accounting for the trapezoidal nature of the waveforms associated with high-frequency operation, and the dead time between the switches in the half-bridge. A design example of a 48-V/1.2-V, 25-A converter operating at 1 MHz is chosen to highlight the validity of the proposed design and that superior results can be achieved if the resonant tank is designed in tandem with the auxiliary network. Experimental results verify that ZVS is achieved, and that the proposed design reduces the auxiliary inductor by close to a factor of 3.