Horizontal Charging Area Extension Based on Switchable Relay Coils

This article explores the potential of relay coils (ReXs) to extend the horizontal charging area for planar inductive couplers. It focuses on the coupling mechanism and derives the equivalent coupling coefficient for model simplification. Based on the new model, a one-ReX coupler is proposed to enhance the coupling under large misalignment. Besides, the influence of coupling polarity change is evaluated and well compensated. In order to further enhance the coupling, a multiple-ReX technique is proposed and justified by a two-ReX coupler and a three-ReX coupler. The experimental result shows that the enhanced coupling coefficient helps maintain the efficiency to be above 92.5% under large misalignment when the one-ReX coupler is used. With three ReXs, the achieved efficiency is further improved by 2.3%.