A modified asymmetrical pulse width modulated resonant dc/dc converter employing an auxiliary circuit will be proposed in this paper. The auxiliary circuit consist of a network of two capasitors and an inductor. The aim of this network is to produce zero voltage switching (ZVS) over a wide input voltage range, while reducing the voltage stress on the resonant component. A detailed analysis and performance characteristics are presented. Experimental results for a 5V, 35W converter show an efficiency of 83 % at a constant operating frequency of 500 kHz. Using metal oxide semiconductor field effect transistors (MOSFETs) as synchronous rectifiers can further reduce power losses and improve the efficiency to be greater than 90 %.