An LLC-based planar wireless power transfer system for multiple devices

Wireless power transfer (WPT) technology has become a popular idea in battery charging for both low- and high-power applications, such as mobile-phones and electric vehicles (EV). For charging portable devices, common ideas apply location sensing and turn on specific coils under the loads. This paper proposes a universal WPT system for multiple electronics devices. The system is based on LLC circuit, with an additional inductor added on the primary LC circuit, making the system less sensitive to load variations while maintaining a reasonable voltage-range. Parallel-connected transmitting coils provide independent charging for each load. A simple yet effective variable-frequency control algorithm is used to provide maximum and balanced charging power to the loads. Simulation results have demonstrated the advantages of the system - optimal operating frequency in a small range, simple control and independent charging for each load. The hardware has been used to show the practicability of the system.