Design, Analysis, and Experimental Verification of a Ball-Joint Structure With Constant Coupling for Capacitive Wireless Power Transfer

This article presents the design, analysis, and verification of a ball-joint structure suitable for capacitive wireless power transfer (WPT) for a consumer electronic lighting system. The WPT structure consists of a ball-joint component rotatable inside a spherical socket. Conductive surfaces are used to form equivalent plates so that the capacitive WPT can be achieved through electric field coupling. One unique feature of this novel structure is that the mutual capacitance remains almost constant in the rotatable angular range. The design and theoretical analysis are included and practical results obtained from a 7-W prototype are included to confirm the theory.