Battery Charger Based on High Step-Down DC-DC Converter for Light Electric Vehicle Charging Applications

This paper proposes a battery charger system based around a high step-down DC-DC converter, which is capable of stepping down a 400-V input to a 25.6 V for charging a lithium-ion battery pack. The converter combines features of cascaded and interleaved buck converters, while also incorporating a switched capacitor. Hence, the converter can provide a higher step-down voltage gain for a given duty cycle. A constant current-constant voltage (CC-CV) control technique is used as the charging scheme. The battery charging capability of the converter is validated experimentally by building a 160-W lab-scale prototype for 0.5C and 1C charging rates. For result verification, a comparative analysis is conducted between the charging characteristics of the proposed prototype and a commercially available battery tester. The result shows a maximum average error of 0.87% and 0.56% for 0.5C and 1C charging rates, respectively. The converter's ability to achieve over 92% charging efficiency across various charging rates demonstrates its suitability for charging light electric vehicles (LEVs).