Isolated Gate Driver for Medium Voltage Applications Using a Single Structure

Abstract

According to the International Electrotechnical Commission, medium voltage ranges from 1 kV to 36 kV. In this voltage range, the field of power electronics has been focusing on developing power converters with high efficiency. Converters for such applications include solid-state transformers, energy storage systems for vehicle charging, electric aircraft, etc. Power ranges could reach tens to hundreds of kilowatts at relatively high frequency (10–50 kHz). Currently, there are no high-frequency power semiconductors capable of switching these voltage levels. Instead of using a single power switch, a string of power switches is used. The upper switches in the string require special attention because they need the highest isolation capabilities and a floating control signal and power supply for the gate driver. Many techniques have been proposed to accomplish this, but they commonly use separate circuits for the control signal and the power supply, increasing the cost, size, and complexity of the gate driver. This paper presents a gate driver for medium voltage with high-voltage isolation capabilities in a single structure for the control signal and the power supply. The proposed gate driver uses a resonant converter that transmits power within the gate driver information. A demodulator separates the gate driver information from the power signal, obtaining the power supply and the control signal for the switch. The paper includes simulation and experimental results that demonstrate the viability of the proposal. The experimental results show the principal features of the gate driver, achieving improvements in complexity, isolation capabilities, and both rise and fall times for large input capacitances of power semiconductor switches. The proposed gate driver presents a rise time of 44 ns and a fall time of 46 ns for the gate input capacitance of currently available SiC MOSFETs. The isolation barrier uses a 25 mm air gap, achieving an isolation capability of approximately 68.2 kV, which exceeds the requirements for MV applications.