A Bridgeless Semi-Quadratic Gain High Power Factor AC-DC Converter Based LEVs Charging Solution

Abstract

A charger topology using a single stage and transformer-less design employing bridgeless semi quadratic voltage gain with high power factor (HPF) AC-DC converter, is demonstrated in this paper for the charging system of light electric vehicles (LEVs). In order to achieve transformer-less structure and wide voltage gain (particularly step-down gain) between high AC input and low DC output (LEVs battery packs), an integrated structure comprising of a bridgeless SEPIC (single ended primary inductor converter) and a buck converter, is effectively utilized to achieve desired charging characteristics at the battery end and maintaining high power factor at AC end of the charger. The bridgeless along with the transformer less structure, together helps in reducing the size, and the cost of the charger and to improve its overall efficiency. Unlike existing SEPIC and Cuk HPF AC-DC converter based battery chargers, the presented charging system ensures continuous current characteristic both at AC side and battery end, and also has the freedom of operating in the discontinuous inductor current mode (DICM) operation. The continuous current characteristic considerably reduces the size of filters and minimizes associated losses, whereas the DICM operation enables control simplicity. Further, the DICM operation optimizes the volume of magnetics and ensures zero current switching of semiconductor devices. Lastly, the design, operating modes, and performance of the charging circuitry are verified through simulation and corresponding results are discussed here for performance verification.