Analytic solution for transfer efficiency of magnetically-coupled inductive wireless power transfer system with constant power load

Due to the advantage of power transmission over certain distance without using wires, the wireless power transfer system has attracted more and more attention. This paper proposes an analytic approach to investigate the transfer efficiency of magnetically-coupled inductive wireless power transfer system with constant power load. The mathematical model of the wireless power transfer system with constant power load is developed, and the resonance condition is derived. Furthermore, the closed-form transfer power and the closed-form transfer efficiency of the system are proposed. The influence of output power, output voltage, input voltage, resonant frequency, and mutual inductance on the transfer power and transfer efficiency are analyzed. This paper can provide a guideline for engineers to follow in the application of magnetically-coupled inductive wireless power transfer system with constant power load.