A Power Relay System With Multiple Loads Using Asymmetrical Coil Design

In this article, we propose a power relay system to power multiple loads wirelessly via magnetic coupling. Multiple power relays are placed in a line and the power can be transferred between these relays. Each power relay consists of two relay coils, which function as the receiver and transmitter, respectively. In order to suppress the magnetic coupling between the two relay coils in the same power relay, bipolar coils are adopted and placed perpendicularly. A compensation capacitor is connected in series with each transmitting coil, while another one is connected in parallel with each receiving coil. It is derived that the constant voltage characteristics can be obtained for each load, which means the load power is decoupled from each other. The two coils in the same power relay have different inductance values, which form an asymmetrical structure to achieve equal load voltage distribution. Moreover, zero phase angle can be obtained for the input impedance. The proposed system is suitable to power the gate drivers of series-connected insulated gate bipolar transistors, where multiple isolated power supplies are needed. An experimental prototype with six loads has been constructed to validate the proposed system. The maximum efficiency can reach 94.0% at a power level of 12.6 W.