Two-switch voltage equalizer based on half-bridge converter with multi-stacked current doublers for series-connected batteries

A two-switch voltage equalizer using a half-bridge converter with multi-stacked current doublers (MSCDs) is proposed for series-connected batteries in this paper, for which only two switches are required, regardless of the number of batteries connected in series. The proposed equalizer is also capable of relatively large equalization currents without increasing ripple current thanks to the interleaved operation of the MSCDs. Fundamental operational analysis for discontinuous conduction mode, in which currents in the equalizer can be limited to within desired levels without feedback control, is performed. The result of an experimental equalization test performed for four lithium-ion batteries connected in series demonstrated the ability of the proposed equalizer to effectively eliminate voltage imbalance.