Magnetic Coupling WPT Efficiency Improvement by Inserting Relay Coil with Optimized Load Impedance

This paper proposes a novel method using optimized load impedance and parasitic relay coil to improve the power transmission efficiency in the magnetic field coupling wireless power transmission. Although the relay coil is effective to enhance the WPT efficiency, it is not always effective in improving the maximum power transmission efficiency that uses a matching circuit. To address the issue, this paper adopts inserting a load in series with coil port. By optimizing the load impedance using an electromagnetic field analysis, the efficiency without the matching circuit can be increased. The difference between the efficiency and the maximum power transmission efficiency with the matching circuit can also be reduced. Both of the efficiency and the maximum efficiency of WPT could be improved by inserting the relay coil when the same impedance elements are loaded on all of the power transmission coil, power reception coil, and relay coil.