Design Of Nanosecond Pulse Power Supply Based On SiC MOSFET

At present,The technology of pulse power is widely utilized in military,environmental protection,biotechnology and many other fields,such as desulfurization and denitrification,pulse sterilization,laser tube driver,cathode-ray-tube scanning circuit and so on.The vacuum arc discharge tube,hydrogen thyratron,and spark-gap are the common discharging switches to be utilized in the conventional pulse power supplies,which have the disadvantages of high cost,short lifetime,and complicated peripheral circuits.With the development of power electronics technology,the performance of power MOSFETs and IGBTs has improved significantly.These power semiconductor devices can be connected in series and parallel to form the high-voltage solid-state switches to replace the traditional discharging switches,which implement the high-frequency pulse generator with nanosecond rising edges designed by many scholars.In this thesis,a nanosecond-level pulse power supply based on SiC MOSFET devices has been designed,and the main technical specifications are shown below: the adjustable range of peak output pulse is 0 ~ 30 kV,the adjustable repeating frequency of pulse is from 10 Hz to 1kHz,the maximum output current is 80 A,and the rise time of pulse is less than 100 ns.The main work included in this thesis is indicated as below:The topology of the nanosecond pulse power supply has been designed in a three-stage Marx generator structure.The mechanism of voltage imbalance in static and dynamic characteristics of the SiC MOSFETs in series connection was studied,and the key factors were derived.For the static voltage balancing circuit,the design method of the voltage balancing resistors was clarified.Moreover,for the dynamic voltage balancing circuit,the RCD circuits on load side were used to balance voltage,and the method of selecting proper parameters for components was determined.The advantages and disadvantages of forward driving,half-bridge driving,and flyback driving were compared and analyzed.Then the half-bridge driving was applied as the series driving circuit of SiC MOSFET.This circuit has high isolating strength and simple driving circuit design process.The number of turns of the primary and secondary windings of the driving transformer is 1,which reduces the influence of its distribution parameters.The synchronization of the driving circuits was experimentally tested,and the difference of the driving delay time was less than 10 ns which shows a good capability in synchronization.The Microchip's dsPIC33FJl28MC706 was used as the main controller,and the entire control system can achieve adjustable frequency,adjustable pulse amplitude,and overvoltage and overcurrent protection.After the producing and testing of the prototype,the performance of the power supply was tested under the needle-plate reactor load.The experimental results approve that the power supply meets the design requirements and has desired performance.