Investigation of Structure and Material for Back Yoke at 13.56 MHz Wireless Power Transfer Focused on High Transmission Efficiency

Wireless power transfer (WPT) is a technique to send electricity without the need for a mechanical point of contact. Because of the widespread use of WPT technology, fast charging speeds and space saving devices are desired. Therefore, in order to shorten the charging time, suitable materials and structures of the back yoke were examined. We made a core and cap-shaped back yoke using an amorphous powder with low loss. As a result, the transmission efficiency in the ideal state increased by 0.7%, and at 50 W transmission, it increased by 1.2%.