A Loosely Coupled Planar Wireless Power Transfer System Supporting Multiple Receivers

A high-efficiency wireless power transfer system which is capable of supporting more than one receiver using class E operation for transmitter via inductive coupling has been designed and fabricated. The design approach of the system is also presented in this paper. The system requires no complex external control system but relies on its natural impedance response to achieve the desired power delivery profile across a wide range of load resistances while maintaining high efficiency to prevent any heating issues. A switch circuit is used to decouple the fully charged receiver from the system so that power delivery to the other receiver can be improved. The fabricated system at 12 V supply voltage is compact and capable of approximately 2.5 W of power delivery to each of the two receivers in a dual receiver setup and 5 W to a single receiver alone or when the other receiver is decoupled by the receiver switch. During high-power delivery state, the system efficiency is between 67.5% and 77.5%.