A General Purpose Transformerless Charging System Based on Fully Bridgeless Canonical Switching Cell High-Quality Rectifier for LVEVs

Abstract

A general purpose transformerless charging system (CS) targeted for various class of low voltage electric vehicles (LVEVs) (24 V–72 V), is designed, analyzed, and implemented in this work. The presented CS employs a fully bridgeless canonical switching cell (FBLCSC) improved power quality rectifier (IPQR) at its front end stage, and a high gain buck (HGB) DC-DC converter at its back end stage. At front end, the presented FBLCSC IPQR does not employ diode bridge rectifier (DBR) circuit, and therefore, ensures better conversion efficiency while operating over wide range of AC mains conditions (110 V–265 V). Further, compared to conventional buck-boost derived IPQRs, the presented IPQR employs minimum component count and maintains low current ripples at its AC and DC ends. On one side, the minimum component count shrinks down the cost, size and losses of the complete CS; low current ripples characteristic on the other side lowers the size of AC and DC end filtering elements. Notably, the FBLCSC IPQR exhibits auto unity power factor operation during discontinuous current mode (DCM) design, and thus, facilitates simple and low cost control architecture. Apart from control simplicity, the DCM operation of FBLCSC IPQR leads to negligible switch turn-on and diode reverse recovery losses. Likewise, at the back end stage, the HGB converter realizes a transformerless DC-DC stage to ensure ripple free charging of different classes of LVEVs. Even if, the HGB DC-DC stage accomplishes transformerless steeper step down gain, its simple design and effective operation over wide battery voltages (24 V–72 V), are further ensured through flexible DC link voltage (150 V – 350 V) control of front end FBLCSC IPQR. At last, the design, operation, and performance of the presented CS are validated experimentally, and relevant results are discussed comprehensively in support of the performance validation of the presented CS.