A Detailed Analytical Model of SiC MOSFETs for Bridge-Leg Configuration by Considering Staged Critical Parameters

Abstract

The high operating voltage and switching speed of silicon carbide (SiC) MOSFETs have significant impacts on parasitic elements. This leads to a limitation in the performance of the devices. Especially in the bridge-leg configuration, the coupling of the parasitic elements, in the upper and lower bridge-legs, produces knock-on effects, which complicates the modeling development to reveal the underlying mechanisms. This paper presents a detailed piecewise linear analytical model for bridge-leg configured SiC MOSFETs, which takes into account their characteristics and all parasitic elements. The novelty of the proposed model lies in the fact that the critical parameters in each stage are distinguished flexibly and emphatically according to their influence weights to the corresponding main variables. Therefore, the complexity of the model which considers all parasitic elements is reduced but the critical impacts on the switching processes are carefully kept. The turn-on and turn-off processes are analyzed stage-by-stage in detail with the derived critical parameters equivalent circuits, and the mechanism underlying how each critical parameter influences the model is revealed individually. Furthermore, based on this model, the impact mechanisms and trends of the switching rate variation, the power loop attenuation oscillation, and the driver loop crosstalk phenomenon for different critical parameters are analyzed emphatically. Double pulse measurements with a 600 V/20A SiC MOSFETs based bridge-leg test circuit are used for the experimental verification of the accuracy of the model and the trends of the critical parameters' impacts.

Keywords

• Analytical model
• bridge-leg
• SiC MOSFET
• critical parameters
• impact mechanisms
• staged