Switching Technique for Inductive Power Transfer at High-Q Regimes

Inductive power transfer employing high quality factor (high-Q) resonators is an effective method to extend the transfer range of the wireless power transfer system. However, the overenhanced loading effect on the transmitter side exacerbates the degradation of power transfer capability and the phenomenon of frequency splitting at a short coupling distance. Currently, range adaptation techniques compensate and maximize the power transfer capability at the cost of power transfer efficiency, which leads to the power plateau and power transfer efficiency bound of 50% for voltage-fed inductive power transfer (IPT) system. In this paper, a switch-mode operation is proposed to improve the transfer characteristics of the high-Q voltage-fed IPT system at a short distance. By employing the resonators as an energy storage element rather than a loosely coupled transformer, the proposed method takes advantage of the transient process of energy exchange between resonators, which decouples the load with the TX circuit and maximizes the transferred power without the need of reducing efficiency of the system. The proposed operation is demonstrated by the experiment. The results show that the switch-mode operation significantly enhanced the power transfer capability of the system used in the experiment. Meanwhile, the power transfer efficiency and the transferred power of the experiment circuit are independent with each other; both of them increase with coupling monotonously.