A Single-Stage Fully Bridgeless Switched-Inductor Based Modified SEPIC AC-DC Converter with High Step-Down Gain for LVEVs Charging Applications

A charger topology based on a modified fully bridgeless switched-inductor SEPIC converter is demonstrated in this paper for the charging application of low voltage electric vehicles (LVEVs). As compared with the conventional SEPIC converter with buck-boost gain, the presented modified converter is able to give higher step-down gain, by utilizing a switched inductor structure. Moreover, the fully bridgeless configuration at the frontend, reduces the conduction losses incurred, adding to the improved efficiency of the charger. Further, the intermediate inductors in this converter, are designed in discontinuous inductor current mode (DICM), which reduces the size of the inductors, enables inherent power factor correction (PFC) and facilitates inherent zero-current turn ON and zero current turn OFF for the switches and diodes, respectively. The control complexity is reduced, with the inherent PFC feature reducing the need to generate the fundamental frequency component for input current shaping. The charger presented in this work is able to give good grid side performance, with unity power factor operation, as well as low harmonics distortions, while maintaining good charging profile at the output. Finally, the charger topology is simulated, through the proper design of its components; modes of operation and the performance of the charger along with its control circuitry is analyzed in detail. The results of the same are discussed in this work.