Automatic Voltage Equalization Circuit Based on Multiple LC Resonant Units for Series-Connected Supercapacitor Strings

The series-parallel switched-capacitor (SPSC) equalization circuit has high voltage stress on switch. To overcome this problem, an automatic voltage equalization circuit based on multiple LC resonant units is proposed for series-connected supercapacitor strings in this paper. The proposed equalization circuit shortens the equalization paths among cells and uses multiple LC resonant units, which improves the equalization speed. In the proposed equalization circuit, the maximum voltage stress on switch is only half of that in the SPSC equalization circuit. The configuration and operation principle of the proposed equalization circuit is presented. The power, equalization speed, and efficiency of the proposed equalization circuit are analyzed in detail. Based on the theoretical analysis, design considerations of the equalization circuit and design of modularized equalization circuit are proposed to optimize the equalization performance and to further decrease the voltage stress on switch. Simulation and experimental results are provided to verify the validity of the proposed equalization circuit. The results show that the proposed equalization circuit achieves fast equalization speed, high efficiency, and high equalization accuracy.