Design of a High Misalignment Tolerance and CV Output WPT System Using a Secondary Repeater

This article is dedicated to improving the misalignment tolerance of a wireless power transfer (WPT) system using a secondary repeater. To mitigate the drop of mutual inductance when misalignment occurs, the receiver with a co-axial intermediate coil is deployed. As such, the proposed system contains three tuning ratios which correspond to the transmitting, intermediate, and receiving coils. To facilitate the choice of these parameters, an efficient tuning technique is proposed. With the proposed tuning technique, one can conveniently achieve zero voltage switching, constant voltage output, load power regulation, and suppression of load voltage fluctuation under coil misalignment. A 500-W experimental prototype is built to verify the effectiveness and superiority of the secondary intermediate aided (SIA) system. The experimental results show that within a 80-mm planar misalignment range (53.3% of the primary coil diameter), the output voltage fluctuation of the SIA WPT system is within 3%, and the peak dc–dc efficiency is 86.87%. In the vertical transfer distance range of 30–65 mm (70% of the standard transfer distance), the output voltage fluctuation is within 5%, with a peak dc–dc efficiency of 88.27%.