Application of Parity-Time Symmetry to Low-Frequency Wireless Power Transfer System

Abstract

In this study, parity-time symmetry (PTS) was applied to a wireless power transfer (WPT) system in the low-frequency range of 30-40 kHz. A series-parallel topology was analyzed using the coupled mode theory. It was demonstrated that PTS can be preserved over a long transmission distance even at low frequencies by reducing the self-inductance of the receiver coil. The receiver solenoid coil (dimensions: 71 × 30 × 7.4 mm, mass: 45.6 g, self-inductance: 119 μH) was able to maintain a transmission power of 23±1 W and an efficiency of 83±1% within a distance of 12-40 mm. In addition, the suitable coil orientation range was significantly increased from ±5° to ±65°. The power conversion efficiency of a switching-mode amplifier based on a class-D inverter reached 97% at low frequency. These results are expected to contribute to the expansion of PTS-WPT applications.