Analysis and Design of an IPT System Based on Shunt Inductor Compensation for Battery Charging Applications

Inductive power transfer (IPT) system which has advantages of safety, convenience, and flexibility is attractive in battery charging applications. Constant current/constant voltage (CC/CV) charging profile is important to extent the lifetime and improve the performance of the battery. This paper proposes compensation topologies with additional shunt inductor added to the primary or secondary side on the basis of series/series (S/S) compensation, and load-independent CC/CV outputs with near zero phase angel (ZPA) between the input voltage and current can be achieved at two different frequencies. The proposed topologies can reduce passive component counts compared with conventional topologies which have the above characteristics. The nature of gyrator provides a simple way to analyze the characteristics of resonant topologies. In addition, the design freedom can be increased. A 2kW prototype is set up to verify the performance of the system. Frequency can be fine-tuned to improve output accuracy in CV mode, and help maintain high efficiency in CC mode. Experimental results show that zero voltage switching (ZVS) can be achieved over the entire charging process, and the achievement of near ZPA is conductive for high efficiency. In CC mode, the efficiency stays above 95%, and the peak value is 95.5%.