Design of a four-coil wireless power transfer system with load-independent constant voltage output

Abstract

A desirable output regulation scheme is crucial for wireless power transfer (WPT) systems to guarantee different charging requirements. In general, an output controller is applied to the load-end circuit to regulate the system's working conditions. However, the additional hardware device applied on the receiver circuit is not an ideal way because it will occupy the receiver side volume and increase the system cost. Besides, the power loss cost by the controller is also inevitable. Although many different types of control methods are proposed while not using the output controller, the control complexity and communication-free operation should be further considered. To eliminate the output controller and make the system as simple as possible, a design process of four-coil WPT systems with load-independent (LI) constant voltage (CV) output characteristics is proposed in this paper. The methodology of deducing the LI-CV frequencies of the proposed wireless power transfer systems is analyzed and the output control can be easily achieved through the primary side frequency regulation without using any additional hardware.