Galvanic Isolation System with Wireless Power Transfer for Multiple Gate Driver Supplies of a Medium-voltage Inverter

In this paper, a gate driver supply, which supplies power to multiple gate drivers, is demonstrated. Robust isolation is required in the gate drive supplies of a medium-voltage inverter in order to drive high-voltage switching devices such as insulated-gate bipolar transistors. The proposed isolation system achieves isolation with transmission coils mounted on printed circuit boards. Furthermore, the isolation system transmits power from one transmitting board to six receiving boards. In the conventional system, the number of receivers is limited to one. In contrast, multiple receivers are acceptable in the proposed system. These characteristics help reduce the of the isolation system for the gate driver supplies. This paper presents the fundamental characteristics of the isolation system. The equivalent circuit of the proposed system can be derived by applying the equivalent circuit of a wireless power transfer system with a repeater coil. In addtion, a design method for the resonance capacitors is mathematically introduced using the equivalent circuit. It is verified that an isolation system with multiple receivers can be designed using the same resonance conditions as an isolation system with a single receiver. Moreover, the isolation system is experimentally demonstrated. It is confirmed that the isolation system transmits power with a maximum efficiency of 46.9% at an output power of 16.6W beyond an air gap of 50mm with only printed circuit boards.