Parity-Time (PT) symmetry is helpful in wireless power transfer (WPT) systems, as it provides constant power (CP) and efficiency independent of the coupling factor within the critical coupling. The problem facing PT-symmetry WPT systems is their inability to soft switch, which decreases the system efficiency. In this digest, we propose a control method to achieve soft switching and high misalignment tolerance by combining a PT-symmetry-based WPT system with a homogenous transmitter coil. The homogenous transmitter coil provides a constant coupling factor between it and the receiving coil within the homogenous area, allowing for fixed frequency control. The fixed frequency will be slightly higher than the resonance frequency to achieve soft switching. Outside the homogenous area, the controller will switch to resonance tracking mode to achieve PT-symmetry, thereby extending the misalignment tolerance. This study demonstrates a 24V 100W WPT system. The experiment shows that the proposed design can yield 3-4% higher system efficiency within the homogenous area while having CP output and transfer efficiency. Furthermore, 100% free-positioning is achieved within the transmitter coil.
