Research On Several Flexible Topology Of Low-to-Middle Power Level Soft-Switching DC-DC Converters

Under the development trend of Power Electronics System Integration (PESI), research on the establishment of standard power modules (SPM) as well as development of its universality and versatility is one of the important works of power electronics. In order to fundamentally improve the performance of SPM, expand its scope of application, the power electronics topology, which is the core of the SPM, should be studied in-depth to optimizing its performance.In this background, the paper focused on studying the isolated small to medium power level DC-DC topologies: Flyback, Forward and Flyback-forward topologies. The modes to realize soft-switching, broaden input range, as well as the way to optimize efficiency under the entire input range were discussed. In the aspect of soft-switching, Active clamped soft-switching technology was selected to be the ascendant method, which has good performance when applying in flyback, forward and flyback-forward topologies. Active clamped dual-switch flyback topology and active clamped dual-switch flyback-forward topology were proposed for high voltage input applications. The detailed operation principles, characteristics and design conditions were also presented. The research results have shown that active clamped is an effective way in soft-switching achieving and efficiency upgrading for topologies of flyback, forward and flyback-forwardBased on these active clamped DC-DC topologies, corresponding Variable Topology Flexible Converters (VTFC) were proposed, they are: flyback VTFC with active clamped single-switch flyback topology and Asymmetrical half-bridge flyback topology combined; forward VTFC with active clamped single-switch forward topology and Asymmetrical half-bridge forward topology combined; active clamped dual-switch flyback-forwad VTFC with full bridge and current-double rectifier structure combined. The Superiority of VTFC, as well as detailed design methods and shifting control strategy were discussed. And prototypes were designed to verify the wide input range characteristic, the improvement of efficiency under the all input range and the feasibility of topologies transformation.