A Study Of Fast Drive Circuit For High-Voltage SiC BJT Applied In Pulse Power Technology

This paper focuses on a fast drive circuit of the bipolar semiconductor device SiC BJT which is used in pulsed power system,and pursue a high rate of current rise di/dt on SiC BJT base in this pulsed power technology.The drive circuit can not only be used for SiC BJT, but also enlightening for SiC GTO drive circuit.The thesis mainly include the following aspects:In the first part,researehed the development,background and significance of pulsed power technology;Stuy the composition of pulse power system, and the characteristics of SiC power devices;Researched literature of driver circuits for power BJT and GTO.In the second part,a scheme which SiC BJT’s drive circuit and the pulse discharging circuit based on capacitor energy storage were proposed. When pulse discharging, the entire circuit is isolated from the civil grid. The charging part of the drive circuit is designed in the form of Darlington structure. The driver circuit includes silicon MOSFET and silicon BJT, which was used to increase the current of the optocoupler. The entire circuit design process was developed by two steps,the initial design aimed to reduce the circuit inductance to increase the current rate of rise, and the drive current need 30ns to increase from 0 to 100mA;In order to further shorten the time of drive current from 0 to 100mA,on the basis of the initial design the drive circuit was improved,and several major factors that affect the rate of current rise were summed up:the drive circuit capacitor voltage and the driver circuit impedance optimization, I-V characteristics of semiconductor devices in drive circuit, and the speed of the former drive circuit. Experimental results show that time of drive current in the base of SiC BJT from off-state to on-state time was 6ns when pulse discharging. The drive circuit design idea is meaningful in other high-voltage bipolar power semiconductor devices to achieve fast switching. It is also instructive in the discharging research related.In the third part, discharging experiments proved that the circuit scheme could rapidly drive SiC BJT. Experimental results show that when the same voltage of the high voltage discharge capacitor, the higher voltage of the drive circuit capacitor, the faster the rate of rise of the driving current, and the faster of the discharging current;the same voltage of the drive capacitor, the higher discharge voltage of the capacitor, the faster the rate of rise of the driving current, and the faster of the discharging current.