A new method to implement the constant Current-Constant Voltage charge of the Inductive Power Transfer system for Electric Vehicle applications

Inductive Power Transfer (IPT) method becomes more and more popular for the Electric Vehicle (EV) battery charger due to its convenience and safety as compared to the plugged-in charger. In recent years, Lithium batteries are increasingly used in EVs and Constant Current/Constant Voltage (CC/CV) charge needs to be adopted for the high efficiency charge. However, it is not easy to design the IPT Battery Charger which can charge the battery with CC/CV charge under the wide range of load variation due to the wide range of variation in its operating frequency in the case of frequency control or in duty and phase shift in the case of duty and phase shift control. This paper proposes a new design and control method which makes it possible to implement the CC/CV mode charge with minimum frequency variation (around 1 kHz) during all over the charging process. A 6.6 kW prototype charge has been implemented and 96.1 % efficiency was achieved with 20 cm air gap between the coils.