Modelling the Switching Behaviour of WBG based Power Devices

Silicon Carbide (SiC) MOSFET and Gallium Nitride (GaN) HEMT fall into the category of wide band gap (WBG) power devices. These devices compete with the state-of-the-art Silicon MOSFET and IGBT. Superior material properties of SiC and GaN lead to lower on-state drop and support faster-switching transients, hence, lower switching loss. However, it excites device and circuit parasitic that may lead to prolonged oscillation, high device stress, spurious turn-on and EMI-related issues.

So, the benefit of using SiC and GaN power devices comes with numerous design challenges, resulting in their slow commercial adoption. The overall market share of WBG devices (SiC and GaN together) was less than 10% of that of power semiconductors in 2023. A better understanding of switching behaviour is essential to overcome the design challenges and fully utilise the benefits of fast-switching of WBG devices. However, the switching dynamics of WBG devices are complex due to the highly non-linear device characteristics and participation of circuit parasitic.

This talk will discuss recent work on developing a circuit-based model for hard and soft transitions of SiC and GaN FETs that captures the complex non-linear dynamics observed in the experiment. Given the device-related parameters extracted from the data sheet and estimated or measured circuit parasitic, the developed digital twin model can predict lost switching energy, rate of change of device voltage, transient over-voltage, etc., which are necessary for a successful power converter design. Based on this model, an interactive software tool was developed.