Capacitance Variations and Gate Voltage Hysteresis Effects on the Turn-ON Switching Transients Modeling of High-Voltage SiC MOSFETs

Abstract

This paper presents a discrete and real-time capable dynamic behavioural model of the turn-on switching transition of high-voltage and high-current Silicon Carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) half-bridge power modules. The dynamic switching model utilizes the Shichman and Hodges equations using voltage-dependent non-linear device capacitances and module electrical parameters to obtain an accurate dynamic model of the device switching transients. The key device states gate-source voltage, drain current and drain-source voltage are modelled. The paper investigates the impact of correct device capacitance modelling with low off-state gate-source voltage values, impacting the device capacitances and causes gate-voltage hysteresis effects. It has been shown that the presented discrete-time dynamic switching model accurately describes the turn-on transient and the results highlight the importance of correct capacitance and threshold voltage characterization data. The modelling results are compared to experimental measurements conducted in a 3.3 kV/750 A SiC MOSFET power module. The model exhibits an average accuracy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim 4\%$</tex-math></inline-formula> for turn-on energy and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim 1.3\%$</tex-math></inline-formula> for the turn-on time compared to measurements. These models are valuable for rapid and cost effective design and validation of advanced gate-driver circuits and for determining key design and operating parameters such as deadtime, switching frequency and switching losses.