A Parallel Primary Windings Scheme for the Flyback Input-Series Transformer-Integration Converter

A parallel primary windings (PWs) scheme is investigated for the integrated-transformer of the flyback input-series transformer-integration (ISTI) converter. Compared to the existing layer-by-layer PWs, the parallel PWs are easy to be manufactured, and active input voltage sharing performance of the converter can be improved if the parallel PWs scheme is adopted. Energy influences of the stray capacitances are slightly larger in the parallel PWs than those in the layer-by-layer PWs, but this difference will decrease as the layer number of each PW increases. Based on the two-transistor flyback ISTI converter, the parallel PWs is analyzed in detail compared to the layer-by-layer PWs, through which applications of the parallel PWs scheme are concluded. Finally, experimental comparisons have been done on a laboratory-made flyback ISTI converter with five different integrated-transformers, and the theoretical analysis is verified by the experimental results.