High-Efficiency Omnidirectional Wireless Power Transfer System

To achieve omnidirectional wireless power transfer (WPT), it is crucial to tune the direction of the total magnetic field from the transmitter (Tx) coils toward the receiver coil (Rx) that can be placed at different positions with respect to Tx. Several methods, such as amplitude modulation, phase-shifting, and frequency modulation, have been proposed to vary the Tx currents, depending on the angular position of Rx, but complex sensing and feedback control systems are required. In this article, we propose an efficient omnidirectional WPT system that is capable of self-tuning the power flow without any feedback from the Rx-side. It only requires a simple Tx current switching rather than complex feedback control system for detecting the Rx position. The proposed system consists of three orthogonal transmitter-repeater (Tx-Rp) channels that deliver power to Rx. In this configuration, the Tx currents are proportional to the mutual coupling between the Rp and Rx in the same channel, which ensures the self-tuning of the optimal power flow through channels. Both theoretical and experimental studies are performed to validate the proposed method. The prototype of the proposed approach enables the Rx to harvest power with almost uniform high efficiency (about 90%) regardless of its angular position.