An Input-Series Flyback Auxiliary Power Supply Scheme Based on Transformer-Integration for High-Input Voltage Applications

An input-series flyback auxiliary power supply scheme is proposed and investigated, which is suitable for the high-input-voltage multiple-output low-power applications. In this power supply, a common integrated-transformer is adopted, all of the series-modules are operating synchronously, and the active input voltage sharing (IVS) can be achieved efficiently without any special controller. The active IVS mechanism of the proposed scheme is analyzed in detail. Furthermore, design considerations of the common integrated-transformer and the input filter capacitor of each series-module are discussed, as well as the influence analysis when the series-modules are operating asynchronously. Finally, a 60-W laboratory-made prototype of the auxiliary power supply composed of three flyback series-modules is built, and the feasibility of the proposed scheme and the validity of the theoretical analysis are verified by the experimental results.