Influence of parasitic elements of busbar on the turn-off voltage oscillation of SiC MOSFET half-bridge module

In high-power converters based on SiC-MOSFET half-bridge modules, laminated busbar plays a critical role in linking the DC capacitor bank to power modules. The busbar stray capacitance has the same order of magnitude with drain-source capacitance of SiC-MOSFET and has a great impact on the turn-off voltage oscillation of SiC-MOSFET. In this paper, parasitic elements of a three-layer laminated busbar are extracted and a busbar model with consideration of stray capacitance is obtained. A spectrum analysis is performed on a small-signal model of equivalent circuit of double pulse test (DPT), and the model with busbar stray capacitance has lower oscillation frequency of turn-off voltage. The results of simulation and experiment of DPT indicate that the simulation waveforms of model with busbar stray capacitance are more consistent with the experimental waveforms over the entire voltage levels, which proves a greater accuracy of the proposed busbar model.