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在高频开关工况下,SiC器件分布参数(电感、电容)间耦合振荡带来的过电压易造成元器件的击穿损坏、引发的电磁噪声会干扰变流器其他部件的正常运行。文章对SiC MOSFET的开关过电压进行了机理分析,特别是杂散电感对其开关特性的影响,对其吸收回路进行了研究,利用开关系统大信号模型等效出脉冲开关系统小信号模型,并依此分析了吸收电容对关断过电压的影响,提出了SiC MOSFET高频吸收电路的选型方案。仿真和实验结果验证了分析结论的正确性及所提方案的有效性和可行性。
Under high-frequency switching conditions, the over-voltage caused by the coupling oscillation between SiC device distributed parameters (inductors and capacitors) can easily lead to the breakdown breakdown of the components. The induced electromagnetic noise may disturb the normal operation of other components of the converter. In this paper, the mechanism of switching over-voltage of SiC MOSFET is analyzed, especially the influence of stray inductance on its switching characteristics. The absorption loop is studied. The small signal model of pulse switching system is equivalent to the large signal model of switching system Based on this, the influence of absorption capacitance on the over-voltage is analyzed, and the selection scheme of SiC MOSFET high-frequency absorption circuit is proposed. Simulation and experimental results verify the correctness of the conclusions and the validity and feasibility of the proposed scheme.