Robust Parity-Time-Symmetric WPT System With Reduced Switching-Frequency and Improved Step-Down Conversion Ratio

In this article, combining the phase synchronization method (PSM) and high harmonic operation (HHO), a novel parity-time (PT)-symmetric wireless power transfer (WPT) system with reduced switching frequency and improved step-down conversion ratio is proposed, where the power transferred to receiver side is carried by the $n$ th harmonic. We demonstrate that constant current (CC) and constant voltage (CV) independent of coupling coefficient and load resistance can also be obtained without wireless communication and additional dc–dc converters. Here, a new implementation of a negative resistor based on the $n$ th harmonic operation is proposed, which is a necessary condition of a PT-based system. In contrast to the standard PT-based system with the same resonant frequency, the switching frequency is reduced to 1/ $n$ due to the use of the $n$ th harmonic, thereby realizing low switching losses and high system efficiency. Besides, an inherently improved step-down conversion ratio can be obtained. A prototype with a 6-A charging current and a 36-V charging voltage is built to verify the feasibility of the proposed method.