Relationship between Leakage Magnetic Field Reduction and Coil Shape for Wireless Power Transfer

Technology for wireless power transmission via electromagnetic induction is expected to be useful for many kinds of electric equipment. In this technology, an alternating magnetic field shared between the primary and secondary coils is necessary. However, the leakage magnetic field caused by this linkage may negatively affect electronic circuits and other devices near the wireless power transmission unit. This paper describes a wireless power transmission coil shape that has high efficiency and a restraining leakage magnetic field. The main result is that a figure-8 coil with a ferrite plate reduces leakage magnetic field strength while maintaining efficiency of wireless power transmission.