A method of resonant frequency optimized selection for a SP inductive coupled power transfer system

Inductive coupled power transfer (ICPT) is an emerging technology that may create new applications for wireless power charging. However, low efficiency is one of the main obstructing factors for promoting this technology. In this paper, a method of resonant frequency optimization based on resonant current calculation at the secondary side of the system is proposed to achieve higher efficiency. In order to research the influences of resonant frequency on system efficiency, the resonant current of the secondary side circuit is calculated, from which the phase shift angle between resonant current and voltage, and the conduction angle of diodes of rectifier can be obtained. Furthermore, a set of simulations are performed to find the optimized resonant frequency relationship between output power and the resonant current amplitude, because the copper loss and core loss of a loosely coupled transformer are all positively associated with resonant current. Finally, a 1.6 kW ICPT system is built and tested to verify the effectiveness of the proposed system. The results prove that the optimized resonant frequency can achieve a system efficiency of 92.5%, when that of a conventional system with a resonant frequency equal to the working frequency is 92%.