Wireless power transfer system with ideal transformer characteristics determined solely by coil turns ratio

Abstract

To manufacture wireless power transfer (WPT) products, not only in-depth knowledge of WPT but also various factors, such as power supply, charging circuit, and battery, must be considered, and the complexity is a barrier to the spread of WPT technology. Therefore, if the voltage is easily stepped up/down by the WPT circuit section, a general-purpose power supply and charging circuit can be used, leading to simplification of the system. The S/SP method proposed in this study exhibits the same input/output (I/O) characteristic of an ideal transformer, and the I/O ratio of the WPT circuit is determined from the turn ratio of the coils, similar to a general transformer. In a power feeding experiment, the I/O voltage ratio of the WPT circuit matched the turn ratio of the coils. The power transfer efficiency of the S/SP system was lower than that of the S/P system, but the difference was only 1.0%. Through a secondary side misalignment experiment, we confirmed that the I/O relation was maintained to an extent. In addition, the S/SP method was clarified to have better displacement characteristics than those of the S/P method.