Analysis on a single-layer winding array structure for contactless battery charging systems with free-positioning and localized charging features

Planar contactless battery charging system is an emerging technology that can be applied to a wide range of portable consumer electronic products. Beginning with a brief historical background, this paper presents a patent-pending single-layer winding array structure with cylindrical ferrite cores for planar contactless battery charging systems. Complying with the “Qi” standard, this design enables multiple devices to be placed and charged simultaneously on the wireless charging pad in a free-positioning manner. The charging flux is totally localized within the covered area between the selected primary winding and the secondary winding inside the load. The electromagnetic characteristics of such winding design are studied in finite-element analysis and confirmed by practical implementation.