Analysis of Circular Couplers in Capacitive Power Transfer

Wireless power transfer (WPT) technology is expected to be applied to a wide range of products. Currently, inductive coupling is mainstream, but capacitive coupling is attracting attention from the perspective of misalignment and EMI. In capacitive power transfer (CPT) systems, circular couplers, which have no horizontal directivity, can be used for wireless charging in a variety of situations. In this paper, we propose the optimum ratio of plate sizes for CPT systems of ringtype and vertical-type couplers. In addition, we clarify the difference in electrical characteristics between ring-type and vertical-type couplers. The analysis results of CPT systems with LC compensation show that the optimum size ratios for ring-type and vertical-type couplers are 0.7 and 0.6, respectively.