Coupled Inductor Design Methodology to Improve Energy Transfer Efficiency in Active Cell Balancing Circuit using Multi-Winding Coupled Inductor

This paper proposes a coupled inductor design of a cell balancing circuit using an inductor coupled by multiple windings. The coupling coefficient of the multiwinding inductor and the output capacitance of MOSFETs affect the energy transfer efficiency of the cell balancing operation. During the balancing operation, the multi-winding inductor stores the energy in the specific source cell and subsequently transfers this energy to the target cell. However, the leakage inductance of the multi-winding inductor and the output capacitance of the MOSFET induce unintended energy transfers to other non-target cells, thereby degrading the transfer efficiency of the balancing current in each cell balancing operation. In this paper, the impact of the energy transfer efficiency deterioration is analyzed, and the design methodology of the multi-winding inductor is proposed to improve the energy transfer efficiency. The improvements of the proposed method are verified by experiments with a 1 W prototype cell balancing circuit.