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

This paper introduces innovative nonisolated and isolated soft-switched dc-dc topologies with the step-up/down ability. The nonisolated topology is constructed by adding a small ac capacitor 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 substituting the main inductor with an air-gapped high-frequency transformer, 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 comprehensive 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.