Multi-Mode Lithium-Ion Battery Balancing Circuit Based on Forward Converter with Resonant Reset

Abstract

A multi-mode active balancing circuit based on a forward converter with resonant reset is proposed to deal with unbalanced states of lithium-ion battery packs. The balancing circuit utilizes the forward converter, enabling high-power balancing. SPST relays are selected to constitute the switching matrix, and the proposed balancing circuit completes the connection of serial battery clusters to the main circuit by controlling the SPST relays, realizing the Multi-Cell-to-Multi-Cell (MC2MC) balancing method. An “adaptive selection mode based on the state of high energy battery” balancing strategy is proposed. The proposed balancing strategy allows the proposed balancing circuit to have multiple balancing modes, flexible balancing paths, and switching between different balancing processes in real time, significantly improving the balancing speed. The inherent LC resonant reset structure of the forward converter is employed to achieve MOSFET zero-voltage switching (ZVS). To optimize the balancing performance, the circuit model is built and the balancing parameters in the circuit are analyzed. An experiment with an eight-cell lithium-ion battery pack was performed to verify the balancing effect of the proposed circuit, and comparison with a typical balancing circuit was carried out. Experimental results show that the proposed balancing circuit has a faster balancing speed.

Keywords

• lithium-ion battery
• active balancing circuit
• Multicell-to-Multicell (MC2MC)
• forward converter
• zero-voltage switching (ZVS)