Dual-mode Wireless Power Transfer Module for Smartphone Application

In this paper, we propose a dual-mode wireless power transfer (WPT) module with a single resonance coil which can operate at two different frequency bands including 6.78 MHz magnetic resonance WPT mode and 13.56 MHz near field communication (NFC) mode. In order to be able to embed this module into smartphone battery back cover, the electrical designs are optimized and then the size was fixed 45 x 90 x 0.35 mm(3) (including ferrite sheet) which is the same commercial smartphone Samsung galaxy note 4. At two different frequency bands, the proposed dual-mode WPT module has more than 20 dB return loss characteristics and shows more than 70 % transfer efficiency between resonant coils at 6.78 MHz in magnetic resonant charging environment. From these results, it has been confirmed that the proposed dual-mode module can be used as the magnetic resonance based wireless charging and NFC for smartphone application.