Analysis and Suppression of the Circulating Current Influence in the Input-Series Auxiliary Power Supply for High-Input-Voltage Applications

The input-series converters based on transformer integration have the advantages of active input voltage sharing (IVS) and simplicity of the whole system, which are suitable for the high-input voltage multiple-output applications. However, due to the parameters error in each series module, the circulating current occurs among the series modules during the active IVS process. Aiming at this type input-series two-transistor flyback converter, the mechanism and influence of the circulating current in each series module are analyzed. On this basis, according to the characteristics of the peak current mode control scheme adopted in this converter, a suppression strategy is proposed, by which influence of the circulating current on the operational stability of the converter under the light load conditions can be eliminated. Finally, based on the simulating results, the experimental study has been done on a 60-W experimental prototype composed of three series modules, and the theoretical analysis and the proposed suppression strategy have been verified by the experimental results.