Planar multiresonance reactive shield for reducing electromagnetic interference in portable wireless power charging application

Wireless power transfer (WPT) technologies are currently growing in popularity because of problems with batteries in portable devices, such as the added weight and the inconvenience of conventional wired charging methods. However, wireless charging systems generate leakage magnetic fields, causing malfunctions in adjacent electronic devices. Technologies to suppress electromagnetic interference (EMI) from portable WPT systems are required to prevent this problem. In this paper, we propose a topology design for a multiresonance reactive shield to suppress the EMI from WPT systems. The proposed shield employs closed loops, which are located peripheral to the WPT coil and resonance matching capacitor. The power efficiency and shielding performance of the proposed method were compared with those of the conventional WPT system coil shielding topologies. The proposed shield exhibited about 27.37dB more 3rd harmonic EMI suppression than other methods while maintaining higher power transfer efficiency.