Reconfigurable intermediate resonant circuit based WPT system with load-independent constant output current and voltage for charging battery

Abstract

In this letter, a compact battery charger based on wireless power transfer (WPT) technology without any communication requirement is proposed. Here, a new intermediate coil is developed to achieve load-independent constant current (CC) and constant voltage (CV) outputs. The intermediate coil is split into two coils and is overlapped with the receiver coil to form a compact structure. Two switches on the receiver side are used to reconfigure the intermediate resonant circuit in order to select different charging modes, i.e., CC mode or CV mode. The communication between the transmitter side and the receiver side as well as complex control strategies is not needed in the proposed structure. Besides, the proposed system can achieve zero phase angle operation, fixed operating frequency, and zero-voltage switching, which not only can lower the power rating of power devices but also improve the efficiency. A laboratory prototype with a 3.6 A charging current and a 48 V charging voltage is built to verify the feasibility of the proposed method.