A Frequency-Controlled Battery Adaptive Long-Distance High-Efficiency Wireless Charging System

The multirelay wireless power transfer (MR-WPT) system offers significant advantages in long-distance wireless power supply for equipment in complex spaces unsuitable for maintenance. While ensuring functionality, the simple structure will undoubtedly have a strong appeal in terms of stability and cost. This article presents an extremely simple battery load adaptive wireless charging system. A novel n-coil MR-WPT system has been designed that is capable of achieving constant current output with a zero phase angle (CC-ZPA) and constant voltage output with a zero phase angle (CV-ZPA) at different frequencies. The port characteristics of the system were obtained after a method for sensing the battery charge state at the transmitter (Tx) side was obtained. This is employed as a foundation for establishing the switching criterion for the two charging modes. The system uses the Tx’s current to determine the battery status and adjust the frequency to change the charging mode; it is the simplest structure as it does not require any communication and topology switching. Finally, a six-coil prototype was used to validate the system with a maximum resonator transmission efficiency of 97%.