An IPT-Based Voltage Equalizer with Voltage-Doublers for Battery-String Charging

Existing multiple-receiver-IPT-based equalizers targeting individual batteries are not suitable for balancing multiple battery cells, because one receiving coil can be only used to charge one battery cell, resulting in lots of component consumption and complicated systems. Thus, a IPT-Based voltage equalizer with voltage-doublers is proposed in this paper to address this problem. Using the unidirectional conduction characteristics of the diodes in the voltage doublers, the induced voltage at the secondary side can be naturally divided into positive and negative parts and used to charge two battery cells. Both the balancing principle of the two batteries in one voltage doubler and the batteries in different voltage doubler modules are analyzed. A prototype comprising 3 coils and 6 individual cells is carried out to validate the performance of the proposed voltage equalizer. Experimental results demonstrate that the proposed voltage equalizer can realize both system charging and balancing functions, achieving a 78.6% charging efficiency with a 9.1 W charging power.