A Multiwinding Coupling Model for the Forward Input-Series Transformer-Integration Converter

The forward input-series transformer-integration (ISTI) converter is suitable for high-input voltage multiple-output applications. Active input voltage sharing (IVS) of this converter is achieved through coupling of the transformer primary windings (PWs), which can be affected by windings arrangements of the integrated-transformer. To describe coupling influences of various PWs, as well as coupling influences between each PW and the secondary windings adequately, a multiwinding coupling model of the forward integrated-transformer is proposed. Based on this model, active IVS performance of the forward ISTI converter is analyzed in detail, through which design principles of the forward integrated-transformer to improve active IVS performance are concluded. Finally, the forward integrated-transformers with four typical PWs arrangements are design for a 1 kV/96 W laboratory-made forward ISTI converter, and the analysis based on the proposed model is verified by the simulating and experimental results.