固态Marx发生器的过流保护研究

具有快速上升沿、低开关损耗的SiC MOSFET已逐渐在固态高压脉冲电源中使用。针对固态Marx发生器中的常见短路故障，分析了SiC MOSFET的过流损坏机制，提出了一种新型的带过流保护的驱动系统。该驱动系统不仅实现了宽驱动信号同步输出，同时能够在整个SiC MOSFET导通期间提供过电流钳制效果。驱动系统中的保护电路利用SiC MOSFET门极电压与漏极电流的关系，通过单个采样电阻和一对反向串联的稳压管将SiC MOSFET门极电压拉低的方式来限制过电流。实验结果表明：当开关管的导通电流较小时，虽然门极电压会有轻微下降，但是SiC MOSFET的导通阻抗仍然很低；而在过电流故障发生时，门极电压会被快速拉低，开关管的导通阻抗急剧上升，从而迅速将导通电流钳制在安全范围内。

Study on over-current protection of solid-state Marx generators

SiC MOSFETs with fast rising time and low switching loss have been gradually used in solid-state pulse generators. In this paper, aiming at protecting solid-state Marx generators from common over-current fault, the damage mechanism of SiC MOSFET is analyzed, and a new driving system with over-current protection is proposed. The drive system not only outputs drive signals with long pulse width, but also provides over-current clamping effect during the whole conducting process of the SiC MOSFET. Based on the relation between gate voltage of SiC MOSFET and drain current, the proposed drive circuit clamps the conducting current amplitude by pulling down the gate voltage of SiC MOSFET with a single sampling resistor and a pair of anti-series zener diodes. Experimental results show that the on-state impedance of the SiC MOSFET remains very low when the conducting current is low and consequently the gate voltage is slightly reduced. When an over-current fault occurs, the conducting current can be quickly clamped through the rapidly rising conducting impedance of the switch since the gate-source voltage is pulled down quickly.