Cylindrical Transmitting Coil for Two-Dimensional Omnidirectional Wireless Power Transfer

Megahertz-range wireless power transfer has become a promising approach for increasing spatial freedom of charging. This article proposes cylindrical-shaped coil, which can produce the homogeneous magnetic field in plane. The coil consists two helical windings, are wound to guide current opposite directions. A single source is used excite transmitter without any amplitude or phase control circuits. Furthermore, since parasitic capacitance not negligible due complexity shape, we develop general equivalent model with analysis complex coils. system efficiency proposed omnidirectional device validated by practical experiment. measured dc-to-dc approximately 72.4% and load 13 W demonstrated charging at 6.78-MHz operating frequency. Finally, verify that electromagnetic exposure satisfies safety regulations.