A pack-to-cell-to-pack battery equalizer with soft-switching based on buck-boost and bidirectional LC resonant converters

A pack-to-cell-to-pack battery equalizer with soft-switching based on buck-boost converter and bidirectional LC resonant converter is proposed to achieve a fast and high-efficiency battery equalization. The buck-boost converter is employed to transmit energy from a high tension supply to a low one in the buck mode or from a low one to a high one in the boost mode with zero-voltage switching (ZVS). The bidirectional LC resonant converter is employed to automatically transfer energy with zero-current switching (ZCS) with electrical isolation. A prototype with four lithium-ion battery cells is implemented. Experimental results show the proposed scheme exhibits outstanding balancing performance, and the measured peak conversion efficiency is about 93% in the cell-to-pack mode and 72.5% in the pack-to-cell mode.