A Switched Capacitor-Coupled Inductor Based High Gain Buck Converter with Power Factor Pre-regulator for LEVs Charging Application

In this paper, a two-stage charger topology is presented to devise a cost effective and efficient charging solution for light electric vehicles (LEVs). In the presented topology, a canonical switching cell AC-DC converter ensures a high-power factor at the AC side while regulating DC voltage over a wide range of supply voltage. Further, a high gain switched capacitor-coupled inductor buck converter based DC-DC stage is utilized to regulate the charging process while ensuring high step-down gain between input and output side with a sufficiently high duty ratio. It is noteworthy that, unlike the conventional DC-DC stage, the transformerless high gain buck DC-DC converter provides wide voltage gain capability, low voltage stress across semiconductor devices, the optimum volume of magnetic components, and continuous input and output current characteristics. Further, the discontinuous current mode operation of the AC-DC stage simplifies control complexities and reduces the implementation cost of the charger. The operational principle, design procedure of each component and control logic of the presented topology, are elaborated in detail. Finally, the presented charger topology is analyzed under various operating conditions for the LEVs charging applications, and the results are demonstrated for the performance verification.

I. Introduction

The growing demand for electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs), has started a new era in the transportation sector. The concept of e-mobility not only curb CO₂ and greenhouse gas emissions but also reduces the consumption of conventional fossil fuels [1]. Generally, the power demands of EVs and PHEVs are partially or fully fulfilled through battery packs. The technological breakthrough in power electronics has provided various onboard and off-board charging solutions for the EVs/PHEVs battery packs. The onboard chargers have gained significant attention due to their significant advantages, such as charging facility through standard utility socket, safety, and affordability. However, the conventional onboard chargers, especially for light EVs (LEVs) like two-wheelers and three-wheelers, have significant shortfalls like compromised supply side performances, low efficiency, large volume, high stress across semiconductor devices, and slow varying ripples in the charging current [2].