Dynamic Resonant Matching Method for a Wireless Power Transmission Receiver

Wireless power transmission systems can be optimized by matching the resonance frequency of a receiver. However, in certain applications, such as, e.g., a multireceiver system, it is desired to match the individual resonance frequencies of the receiver to a fixed (e.g., common) operation frequency. In this publication, a method is proposed to match the resonant frequency dynamically without changing the physical value of the components. Instead, it is changed “virtually” by a method, which is named “frozen resonance state” by the author. The basic idea is to maintain the state of a resonant circuit (to “freeze” the state) for a fraction of the resonant period, e.g., by freewheeling the current of the resonant inductor or maintaining the voltage of the resonant capacitor. This additional time extends virtually the resonant period leading to an effective lower resonant frequency. By adjusting the additional time, the effective resonant frequency can be matched to the operation frequency individually for each receiver. This publication explains the basic idea more in detail and gives an overview of the different possible circuit topologies. Furthermore, the method is applied to an exemplary receiver of a capacitive wireless power transmission system, where measurements are presented.