A Bridgeless Modified Switched-Inductor SEPIC High Power Factor Rectifier with Extended Voltage Transfer Ratio for Low Voltage Battery Charging Applications

This paper presents a modified single-ended primary inductance converter (SEPIC) based single-stage ACDC converter designed specifically for low voltage electric vehicles (LVEVs) charger applications. The rectifier showcases in this study demonstrates a high-step down buck gain, making it ideal for charging low-voltage battery packs commonly found in LVEVs. By utilizing a bridgeless structure at the input side with simultaneously operated switches, the converter reduces control complexity and eliminates the need for input voltage polarity sensing, a requirement in conventional continuous inductor current mode (CICM) converters. The converter's extended step-down gain is achieved through switched-inductor structures, enabling it to deliver the required battery charging profile for low-voltage battery packs. Operating the inductors in discontinuous inductor current mode (DICM) not only facilitates intrinsic power factor correction (PFC) capabilities at the grid side but also reduces the size of magnetic components. DICM operation also provides zero-current turn-on for switches and zero-current turn-off capability for high-frequency diodes, thereby minimizing losses associated with diode reverserecovery transitions. During testing on a proof-of-concept testbench at a power level of 450W, the converter demonstrated a peak efficiency of 94.2% at rated power. Additionally, the total harmonic distortion (THD) in input current was measured at 3.4%, showcasing a unity power factor and good power quality (PQ) indices at the grid. These results highlight the effectiveness of the converter in maintaining proper battery charging profiles while ensuring high efficiency and power quality standards in LVEV charging applications.