A planar magnetically-coupled resonant wireless power transfer using array of resonators for efficiency enhancement

A novel magnetically-coupled resonant wireless power transfer (MCR-WPT) system using an array of printed spiral resonators is presented. By replacing the single transmitting resonator in a conventional MCR-WPT with an array of smaller resonators, the transfer efficiency of the planar WPT system in both the over-coupled and under-coupled regions are significantly enhanced. Furthermore, with a proper design of the driving loop, the proposed WPT is able to provide consistent transfer efficiency even when the receiver is axially misaligned with the transmitter. Two WPT systems of the size of 10×21 mm² and 21×21 mm² for the transmitter, and 10×10 mm² for the receiver are proposed. The results are compared with the conventional planar WPT of the same size. The measurement results show that with the proposed design, the transfer efficiency of the planar WPT system can be increased from 5% to 66% in the over-coupled region and from 0.75% to 40.67% in misalignment region.