Analysis and Design of Series LC Partial-Resonance-Pulse-Based ZCS Current-Fed Push-Pull Converter

This article analyzes a partial-resonance-pulse, created through a series LC resonant circuit, on the current-fed push-pull converter topology to achieve the zero-current-switching (ZCS) of the semiconductor switches. During switching overlap of the semiconductor switches, referred to as energy storage mode, the resonance occurs and offers the natural commutation of the semiconductor devices. During this period, the current is smoothly transferred from one switch to the other and the outgoing switch commutates naturally with ZCS. It solves the historical problem of the voltage spike across the devices at their turn-off and thus, eliminates the requirements of the snubber across switches or the clamping circuit. This reduces the hardware complexity and makes the converter snubberless, compact, and cost-effective. The variable frequency with constant switching overlap time is adopted for the load voltage regulation and to maintain the ZCS of the devices for a given range of source voltage and load current. A comprehensive study of the steady-state operation and analysis of the proposed topology is reported along with the design and selection of the resonant tank elements. A hardware proof-of-concept prototype rated at 500 W is developed and tested to validate the analysis and claims and demonstrate the converter performance. An efficiency of 96.2% is recorded in a laboratory on the prototype at full load.