Planar Transmitter Coils for Misalignment-Insensitive Wireless Power Transfer System

Conventional wireless power transfer (WPT) systems easily suffer from coil misalignment. This paper introduces a novel coil design that effectively mitigates both angular and lateral misalignment problems. The proposed design is capable of generating a three-dimensional (3-D) rotating magnetic field with a planar structure, enabling one-axis coils to receive power regardless of their position and orientation. The proposed coil consists of three planar coils that are mutually decoupled. A 3-D polarized magnetic field is obtained when excitation currents with amplitude modulation are employed. Then, a detailed analysis of circuit topology is conducted to realize the proposed excitation strategy. The experimental results validate the omnidirectional and free-positioning capability of the proposed WPT system. When five receiver coils are being powered, the DC-to-load efficiency of the system is 10.46% at a height of 0.08 m with a total of 1.05 W load power.