A Receiver-side Self-Harvesting Protection Circuit in Wireless Power Transfer Systems

This paper presents a resonant wireless power receiver with a cut-off circuit to control the rectified voltage, without increasing the specifications of generic components of the receiver such as the receiver coil, resonant capacitors, and semiconductor switches of rectifier. The self-harvesting technique is proposed in order to drive bidirectional switches without uses of bulky isolated gate-drivers and snubber circuits. The self-harvesting operation and the overvoltage protection of the cut-off circuit are experimentally verified in the loosely coupled wireless power transfer system with wide variations of the coupling coefficient (0.003 - 0.03) at 6.78 MHz. The receiver is successfully protected when it approaches to a close distance with the maximum deliverable power more than 20 W. The additional power loss from the self-harvesting is as small as 20 mW when the receiver delivers the load power of 5.4 W.