Switched-capacitor charge equalization circuit for series-connected batteries

In this paper, a novel switched-capacitor charge-equalization circuit is proposed. Electric charge is transferred to a capacitor from two series-connected cells; whereas charge is returned back one of the cells by the charged capacitor. In this way, a larger equalization current can be achieved, and therefore effectively shorten the equalization time. In order to enhance the energy efficiency, voltage-sensing and comparison circuits are added. By comparing the voltages of the adjacent cells, switches are differentially operated to allow selective energy transfer. Thereafter, meaningless energy transfers are reduced and the equalization circuit can achieve higher efficiency.