Modeling and Analysis of vgs Characteristics for Upper-Side and Lower-Side Switches at Turn-on Transients for a 1200V/200A Full-SiC Power Module.

In this work, a 1200V/200A full-SiC half-bridge power module was fabricated for high-power high-frequency application, and the characteristics of gate-source voltage (vgs) at turn-on transient under different output power was investigated via experiments, modeling, and simulation. Also, the comparison of the vgs characteristics between the upper-side and lower-side was conducted. From experiments, the vgs characteristics show negative spike issue and it becomes severe under higher output power conditions. On the other hand, the upper-side and lower-side show different characteristics, namely, the vgs spike of upper-side is superimposed by a 83.3MHz high frequency oscillation during the process of vgs being pulled down, while the vgs spike of lower-side contains no oscillation. The mechanisms behind the influence of output power on the vgs spike characteristics and their difference between the upper-side and lower-side were studied via modeling and simulation. Equivalent RLC (resistance-inductance-capacitance) circuit models were proposed and established for the gate driver loops of the upper-side and lower-side based on the internal structure of the power module. With the help of the proposed models, vgs characteristics of the upper-side and lower-side were simulated and compared with the experimental results. The trend of changes in the vgs pulling-down and oscillation amplitude along with the increasing output power from simulation are consistent with that of the experimental results. In addition, different conditions of gate resistance for the SiC power module are compared. Through the comparison between the experiments and simulations, the validity of the proposed equivalent RLC circuit model and the rationality of the analysis about the mechanisms behind the vgs characteristics at turn-on transient for SiC half-bridge power module are confirmed.