SiC power MOSFET in short-circuit operation: Electro-thermal macro-modelling combining physical and numerical approaches with circuit-type implementation

Abstract

The purpose of this paper is to describe, for the first time, a global transient electrothermal model of (SiC) power MOSFETs during accidental short-circuit (SC) operations. The developed models allow to analysis an inverter-leg malfunctioning. A thermal model of the SiC MOSFET dies combined with extensive experimentations allow to develop models of the gate leakage current and of the drain saturation current during SC events. After verifying the robustness of the proposed elementary models, an original global circuit model with an easy implementation using a commercial circuit simulation tool is proposed and discussed. This circuit model can be used in order to develop protection schemes against SC faults.

Thermal simulations of SiC MOSFETs under short-circuit conditions: influence of various simulation parameters

“…In [12], two 1D electro-thermal models are proposed. The first one is linear and implemented in PLECS whereas the other, implemented in Comsol, takes into account the temperature dependence of the thermal properties of the materials.…”

“…The depth of the depletion layer *"$$ = 1 μm was chosen from values commonly found in the literature [10], [12].…”

“…On the other hand, complete 3D FE simulations can be much more costly and accurate [3], [11]. If some papers perform electro-thermal simulations so as to couple thermal and electrical models [3], [5]- [7], [12], [13], others use experimental electrical measurements to define the heat source [9], [14]- [16].…”

Physical Origin of the Gate Current Surge During Short-Circuit Operation of SiC MOSFET

“…During the SC, the DUT undergoes a high power-density peak leading to a fast rise of its junction temperature. A 1D thermal model has been developed in [9] in order to estimate this temperature. The thermal model is composed of the top aluminium layer and the SiC bulk.…”

“…It is generally assumed that the physical origin of this gate current is due to Fowler-Nordheim (F-N) tunnelling. However, in SC condition and especially with a SiC power device, the junction temperature rises rapidly to reach 1200 K to 1800 K [5], [9]. Furthermore, the gate electrical field is at nominal level (≈4 MV/cm) which does not favour F-N conduction which is supposed to be triggered by a high electric field and is hardly a function of the temperature.…”