A Comparative Study Between Novel and Conventional Four-Resonator Coil Structures in Wireless Power Transfer

Magnetic resonant wireless power transfer is an emerging technology that may create new applications for wireless power charging. However, for general deployment, low efficiency is a main obstructing factor. In this paper, a novel four-resonator coil structure is presented to improve system efficiency. Compared with the conventional four-resonator coil structure, its source and load coils are designed to have high loaded-Q (quality factor) and maximum cross coupling coefficients. Therefore, the source and load coils participate in the coupled-resonance with opposite-side resonators. And additional energy exchange paths are provided. To prevent frequency splitting and to obtain optimum efficiency, a method of coordinating the load resistor and operating frequency is proposed. The theoretical analysis and experimental results demonstrated that the proposed coil structure and method can increase system efficiency effectively.