A design criterion to ZVT DC-DC PWM converters with constant auxiliary voltage source

This paper proposes a design criterion to calculate the resonant auxiliary elements of ZVT DC-DC PWM converters that use a DC auxiliary voltage source. The proposed criterion is based on stored energy in resonant auxiliary elements and takes into account the influence of the auxiliary voltage source value. By means of this criterion the reactive energy can be kept at a minimum level and a reduction of the auxiliary elements current ratings is achieved, which leads to lower conduction losses and improved converter efficiency. In addition, a reduction in auxiliary magnetic elements size can be accomplished. To illustrate the usefulness of the design criterion proposed, comparative results obtained from the true pulse-width modulated (PWM) zero-voltage switching (ZVS) pole boost converter designed by proposed criterion and its original design guidelines are presented. Experimental results show an efficiency gain of about 1% for a wide range and 1.5% at full load. In addition, a reduction of about 52% in the auxiliary transformer volume for the implemented prototype was achieved, ensuring a reduction in overall converter size. Experimental results were obtained from 1 kW, 100 kHz laboratory prototype.