Dakang Yuan’s research while affiliated with Beijing University of Technology and other places

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.

Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) have great advantages in improving the power density and performance of power converters due to the high switching frequency, high operating voltage. However, the increase in switching frequency is also increasingly inflicted the voltage and current stresses to the parasitic elements of the SiC MOSFET, which restricts the device’s optimal performance. In addition, many parasitic elements of SiC MOSFET are coupled with each other during the switching process, which makes the analysis complicated and calculation cumbersome. This paper presents an analytical model for SiC MOSFETs, which identifies and selectes the dominant elements and key variations of each stage separately according to the change stages of major variables. The complexity of the model is reduced while the accuracy is guaranteed. Using this model, the voltage and current switching rate of SiC MOSFET can be quickly solved, and the impact mechanism of each critical parameter can also be revealed clearly. A double pulse test circuit composed of a 600V/20A SiC MOSFET is set up and experimental results are obtained to verify the accuracy of the proposed analytical model.

SiC MOSFETs have an excellent characteristic of high switching speed, which can improve the efficiency and power density of converters significantly. However, the fast switching processes of SiC MOSFETs cause serious crosstalk problems in bridge-arm configurations, which restricts the devices’ performances. This paper presents a detailed and accurate improved crosstalk analytical model, which takes into account the nonlinear capacitances, the parasitic inductances, the reverse recovery characteristics of the anti-parallel diodes, and the nonlinear voltage switching and damping oscillation process. The novelty of the proposed model lies in the fact that under the condition of comprehensively considering all these non-ideal factors of the bridge-arm, the effects of multi-parasitic elements and multi-variables coupling to the crosstalk are hierarchically divided. The parasitic elements and their correlations are described in detail and the direct and indirect variables’ impacts are clearly traced. Thus, according to the different variables switching stages, the influence processes of these parasitic elements and variables can be integrated and a complete equivalent analytical model of the crosstalk process can be derived. The simulation and experiment platforms are established and a series of experimental verifications and comparisons prove that the model can replicate experimental measurements of crosstalk with good accuracy and detail.