Investigation and Implementation of an Input-Series Auxiliary Power Supply Scheme for High-Input-Voltage Low-Power Applications

Aiming at the high-input-voltage multiple-output low-power applications, an input-series two-transistor flyback auxiliary power supply scheme is proposed and investigated. In this converter, an integrated-transformer is adopted instead of the single-transformer in each series-module, all of the series-modules are operating synchronously, and the input voltage sharing (IVS) can be achieved automatically. The active IVS mechanism of this converter is analyzed, furthermore, through the influence analysis when the series-modules are operating asynchronously and the tolerance features of the key parameters are considered, the related design consideration of the input filter capacitor in each series-module is discussed. Finally, after the simulation verifications, a 60-W laboratory-made prototype of this auxiliary power supply composed of three series-modules is built, by which the feasibility of the presented scheme and the validity of the theoretical analysis are verified.