A novel charge equalizer with auxiliary circuit to control the allowable charging and discharging current of the Lithium-ion battery

This paper proposes a novel type of active cell balancing circuit using the multi-winding transformer. This scheme is applied auxiliary circuit for controlling the charging and discharging current of the Lithium-ion battery. Conventional schemes using a multi-winding transformer require a large magnetizing inductance to satisfy the allowable charging and discharging current of the battery cell. In order to obtain a large magnetizing inductance, the cross-sectional area of the core and the number of turns must be increased. For this reason, there are drawbacks that the system becomes bulky and difficult to design. To overcome this problem, the proposed circuit limits the current flow through the diode of the auxiliary circuit to the magnetizing inductance of the multi-winding transformer and controls the slope of the current with the inductor of the auxiliary circuit. Therefore, since the magnetizing inductor does not participate in the slope of the discharge current during the balancing operation, it can be designed with a small magnetizing inductance and has an advantage of easily designing the transformer. In order to verify the validity of the proposed circuit, we analyzed the configuration, operation principle and operation mode of the proposed circuit. Also, the waveforms of the balancing performance according to various conditions, the charging and discharging current control performance of the conventional circuit and the proposed circuit are presented.