Bridgeless SEPIC-based AC-DC converter for compact inverter and low-power AC drive applications

In this work, an efficient AC-DC converter based on a bridgeless single-ended primary inductor converter (SEPIC) is proposed. Composed of only two anti-series switches, two diodes, two inductors, and one coupling capacitor, SEPIC has two different voltage outputs with inverted polarities, which makes it simpler and more attractive than the existing ones. More importantly, each output voltage can be individually adjusted by two different control loops, thus contributing to two different and independent duty cycles. With no need for a front-end diode bridge rectifier (DBR), its efficiency is enhanced. The simulation results on MATLAB/Simulink successfully validate that the converter is capable of supplying an output current in both directions. By connecting two independent loads to the output terminals, each with load characteristics of 100 V, 200 W, and 2 A which fit well with the application requirements of Fuji compact inverters, stable output voltages with a voltage ripple lower than 4.2% were obtained. The operating efficiency under rated load conditions was 95%, resulting in a 10% reduction in DBR usage. Moreover, the envelope of the input line current closely resembles the standard sinewave with a total harmonics distortion (THD) of 2.00%, while the AC load current has a THD of 6.89%, both within standard limits.