Research On Pulse Circuit Based On CS-MCT Series

Pulse power technology is a new science and technology developed for the needs of national defense research,this technology is a kind of electro physical technology which can release the energy with high density stored slowly to the load in a very short time and form the ultra-high pulse power output.In the pulse power system,the pulse switch is a very important component.It needs the ability of high blocking voltage,high peak current and high di/dt.The traditional pulse switch has some disadvantages,such as slow switch speed,short use time,complex driving circuit and huge device volume.The semiconductor switch device for pulse discharge has the advantages of low cost,small volume and high efficiency,which makes it the best choice to replace the traditional switch device.In the selection of semiconductor switches,power MOSFET cannot be used in high-pulse power fields due to their large resistance when they are turned on.Insulated gate bipolar transistors(IGBT)with conductance modulation effect have low resistance in on state,but the Limited di/dt capability and peak current capability due to current saturation limit its application in many pulse power applications.Traditional SCR and GTO have the ability to deal with ultra-high peak current,but because their conduction is controlled by current,the control circuit is more complex,and the lower di/dt capability is not conducive to its application in the field of high pulse power.In this paper,a kind of MOS controlled thyristor(CS-MCT)with cathode short circuit structure is adopted.It combines the advantages of simple gate control circuit of MOSFET and excellent surge current capability of thyristor,so it can provide high di/dt and high peak current.In practical application,the low voltage level of single device can not be used in high-voltage pulse system.By using the device in series,the voltage level of the pulse system can be effectively improved.Therefore,this paper analyzes the reasons for the series voltage imbalance of the device by simulating the pulse discharge circuit based on the CS-MCT device series.The driving circuit is designed using the synchronous transformer driving principle,which solves the problem of driving signal consistency.The problem of static uneven voltage in series devices was solved by connecting the static voltage equalizing resistors in parallel at both ends of the device.The method of parallel RCD voltage equalization circuit at the two ends of the device was used to solve the problem of dynamic uneven voltage of series devices.By analyzing the results of PCB level drive synchronization test,voltage sharing characteristic test and pulse discharge test,the peak current of discharge test of single device at 1600 V is 2340 A.When two devices are connected in series,the total withstand voltage of the series system is increased to 3200 V,and its peak current is increased to 4400 A.When two devices are connected in series,the peak current capability of the pulse system is increased by 88% compared with that of a single device.When the four devices are connected in series,the peak current capacity of the system is 5190 A when it is tested at 4000 V.It is concluded that the series circuit has the ability of synchronous opening,static and dynamic voltage sharing and high peak current in the application of pulse discharge.