Influence of Negative Gate Bias on Crosstalk Spike in SiC MOSFETs Half-Bridge Circuit

Due to the high switching speed and low threshold voltage (Vth) of SiC MOSFETs, a negative turn-off gate bias (Vgsoff) is widely used to avoid false turn-on. The crosstalk spike amplitude is primarily influenced by the ratio of gate-drain capacitance to gate-source capacitance (Cgd/Cgsratio),dv/dt, and gate resistance. This paper firstly demonstrates that negativeVgsoffhas two opposite effects on the crosstalk spike amplitude via its impacts on bothdv/dtand theCgd/Cgsratio. On the one hand, a decrease in negativeVgsoffleads to a reduction inVth, which results in an increaseddv/dtand, consequently, a higher crosstalk spike amplitude. On the other hand, the decrease in negativeVgsoffcontributes to a reduction inCgdand an increase inCgs, which results in a lowerCgd/Cgsratio and, consequently, a reduced crosstalk spike amplitude. Experimental results validate the above analysis, showing that the dominant mechanism governing the variation in crosstalk spike amplitude depends on the gate structure of SiC MOSFETs as well as the operating conditions. The findings of this study can inform gate driver design and contribute to crosstalk spike mitigation strategies.