Optimum Receiver-Side Tuning Capacitance for Capacitive Wireless Power Transfer

This paper reveals the optimum capacitance value of a receiver-side inductor-capacitor (LC) network to achieve the highest efficiency in a capacitive power-transfer system. These findings break the usual convention of a capacitance value having to be chosen such that complete LC resonance happens at the operating frequency. Rather, our findings in this paper indicate that the capacitance value should be smaller than the value that forms the exact LC resonance. These analytical derivations showed that as the ratio of inductor impedance divided by plate impedance increased, the optimum Rx capacitance decreased. This optimum capacitance maximized the TX-to-RX transfer efficiency of a given set of system conditions, such as matching inductors and coupling plates.