An Inductive Power Transfer System With a High-Q Resonant Tank for Mobile Device Charging

Inductive power transfer (IPT), which employs the principle of electromagnetic induction, is widely applied to wireless charging applications. The efficiency of an IPT system is highly dependent on the quality factor (Q) of the power resonant tank. In this paper, a novel design on the structure of the resonant coil is used in the resonant tank to achieve a significantly high Q above 1000 for the IPT system. Compensating capacitors are used in both primary and secondary circuits to align the resonant frequencies in order for the system resonant status to be maintained by a frequency tracking circuit. The experimental results show that with a primary coil Q of 1200, the proposed IPT system allows power to be transferred at a maximum air gap distance to coil diameter ratio of 1.46 for a highest efficiency of 87% at the resonant frequency of 106 kHz.