Overvoltage Reduction with Enhanced Snubber Design for GaN-Based Electric Vehicle Drive

Power electronics applied to electrical vehicle is a field where power density, cost and weight are the main factors for dimensioning a power converter. In this context, one of the trends is to increase the working frequency and use smaller components. This can be achieved with components using technologies that allow an extremely small switching time while keeping the breakdown voltage and current as high as possible. This contemporary trend leads to the use of new materials such as Gallium Nitride or Silicon Carbide. Gan transistors in particular, with switching time as low as 2 ns lead to high overvoltages even with minimized power loop inductances. This overshoot can be addressed by adding an external circuitry known as snubber. While it is widely used, there are difficulties in its modeling and predicting its impact on the transient waveform. This paper aims to present the snubber circuitry applied to fast switching components such as GaN transistors. A mathematical model considering the internal parameters of the transistor is proposed. This model will be used to predict the overvoltage and the impact of the snubber. The mathematical approach is tested by simulation, considering an EPC component on a PCB having a loop inductance of 0.7nH and a dv/dt of 25 V/ns. The waveform improvement and losses are compared and the first results show significant improvement in the voltage waveform with lower overvoltage and ringing.