Partial-Resonant Buck–Boost and Flyback DC–DC Converters

This paper introduces innovative nonisolated and iso-lated soft-switched dc–dc topologies with the step-up/down ability. The nonisolated topology is constructed by adding a small ac ca-pacitor in parallel with the main inductor of the conventional buck– boost converter and replacing its semiconductor devices with the reverse-blocking switches. By using a novel control scheme, true zero-voltage switching is realized at both turn-on and turn-off of the power switches irrespective of the input voltage, output voltage, or load value. The isolated form of the converter is created by substi-tuting the main inductor with an air-gapped high-frequency trans-former, similar to the flyback converter. In this case, two smaller ac capacitors are placed on both sides of the transformer to realize soft switching as well as passive clamping; no extra clamping circuit is required. The basic operation of the proposed partial-resonant converters includes four modes and is described in detail. The com-prehensive analysis of the topologies is carried out as well. Various experimental results in different operating conditions are provided to verify the performance of the proposed power converters.