Design and Performance Analysis of a Repeater-Assisted, Multi-Receiver Wireless Power Transfer System Operating At MHz Frequencies

Simultaneous wireless power transfer (WPT) to multiple receivers (Rxs) is an important requirement for wireless charging of consumer electronic devices. In this article, we propose a WPT coil structure capable of achieving independent multi-Rx WPT with a confined and uniform rotating magnetic field at megahertz operating frequencies. Compared with the existing multiple receiver WPT structures, the proposed structure exhibits low leakage flux outside the power transmitter. Thanks to the single-coil transmitter structure and the load-independent current feature in the repeater coil, no additional control circuit is needed to obtain independent power transfer to multiple receiver devices. The proposed solution is experimentally demonstrated in a 6.78-MHz 80-W WPT prototype, with a dc-to-dc efficiency of 90.2 % in the full-load case using four 20-W receiver circuits.