A Novel ZCS Bidirectional CUK Equalizer for Energy Balance of Battery Cells Connected in Series

In this paper, a new soft switching bidirectional CUK equalizer for cell balancing of a series connected battery string is proposed to achieve a high-efficiency and fast equalization. A resonant tank, which consists of two resonant inductors, a resonant capacitor and an auxiliary switch, is employed in the proposed equalizer to achieved zero-current switching(ZCS) of all semiconductors. Thus the switching loss is reduced and the battery equalizer's efficiency is increased. In this study, the operation principles of the equalizer are given and verified using a 60W experimental prototype. The related experimental results show that the efficiency at 300kHz switching frequency increases around 5%-8% compared with the hard-switching bidirectional CUK equalizer.