Pulse Frequency Modulation for Parity-Time-Symmetric Wireless Power Transfer System

This article proposes and implements an advanced pulse frequency modulation (PFM) scheme to adjust the output power of the parity-time (PT) symmetric wireless power transfer (WPT) system. The key is to utilize PFM to adjust the duty ratio of the self-excited oscillating inverter for the PT-symmetric WPT system, hence transferring more power than that of the conventional forced oscillating inverter under the same input voltage and duty ratio. Besides, the transmission efficiency can maintain high when the coupling coefficient is larger than the critical value. With a proper signal processing circuit, the phase of the inverter output voltage can lead to that of the primary-side current, which can help reduce the switching loss. Therefore, the system efficiency of this self-excited oscillation scheme for WPT can keep high, while the output power can be larger than that of using the conventional forced oscillation scheme. Theoretical analysis and simulation results are given to verify the feasibility of the proposed scheme.