A class of zero-voltage-zero-current switching full bridge PWM converters with a parallel capacitor for primary current reset

This paper presents and analyses the principle of zero-voltage-zero-current switched phase shifted full-bridge DC/DC converters using the parallel capacitor. In principle, the parallel capacitance across the secondary terminals of the transformer and the primary side inductor (usually referred to as leakage inductor) are used to achieve a zero-current-zero-voltage turn off and a zero current turn on of the passive-to-active leg transistors. The turn off of the active-to-passive leg transistors is with zero-voltage and the turn on is with zero-voltage-zero-current across them. This switching scheme is attractive for high power applications where switches such as IGBTs and MCTs are dominantly used. Several topologies that apply this principle are shown. These topologies are experimentally tested and a comparative analysis is performed. Merits and limits are discussed and illustrated. Control and design issues are also discussed.