Kiyoto Matsui

A numerical study of power loss factors in resonant magnetic coupling

We numerically studied the affect of power loss factors in a wireless power transfer system using resonant magnetic coupling. Resonant magnetic coupling is regarded as one of the most promising methods for mid-range wireless charging systems. To make this method practical, it is important to accurately estimate power transfer efficiency and effect of each loss factor in the device-designing stage. We conducted a numerical simulation using an equivalent circuit model and electromagnetic analysis for a mobile-device model. Resonance at 7 MHz between the transmitting and receiving coils was achieved using lumped capacitors attached at the coil ends. In addition to the skin effect, we consider various loss factors such as proximity effect, loss tangent of lumped capacitors, and so on. The results show that the proximity effect significantly decreases the power transfer efficiency of the system, and the loss tangent of lamped capacitor also decreases it by a few percentage points.

Phase and intensity control of multiple coil currents in resonant magnetic coupling

We studied the effects of the phase and intensity of multiple coil currents in a wireless power transfer system using resonant magnetic coupling. Resonant magnetic coupling is regarded as one of the most promising methods for mid-range wireless charging systems. For mid-range charging, the charging device can assume various positions and postures, and some of the conditions make wireless charging difficult. To solve this problem, we propose a method to control the phase and intensity of multiple coil currents. By performing numerical simulations using an equivalent circuit model and electromagnetic analysis, we confirmed that it had the desired effect.