Research On The High Speed Driving Of SiC MOSFET Based On The Bridge Circuit

With the fast development during the past few decades,power electronics technology has been widely applied in industry.As the core component of power electronics converters,the performance of power semiconductors is critical.However,experiencing decades of development,the traditional silicon based power semiconductor devices have approached its physical limitation.Therefore,in order to approach better performance of power electronics converters,the third generation of wide bandgap semiconductor devices represented such as silicon carbide(Si C)have got more and more attention and research.Compared with silicon based power devices,SiC MOSFET has advantages such as high break-down voltage,high junction temperature,high switching speed,high switching frequency and etc..These characteristics which give SiC MOSFET faster switching speed and less switching loss,also lead to more serious oscillations,resulting crosstalk and EMI problem for bridge circuit.The driving circuit plays critical role for the application of pow er devices,so it is essential to research the driving circuit for maximize the properties of SiC MOSFETs.First,the thesis analyzes the structure,working principle and static characteristics of SiC MOSFET.The influence of parasitic parameters on SiC MOSFET switching process is analyzed based on the LTspice simulation.The result shows that the switching speed and loss will be improved with the decrease of the parasitic capacitance,meanwhile,the circuit stress and crosstalk are also intensified.The decrease of parasitic inductance leads to the lower switching loss and oscillation.Taking the spurious triggering problem into account due to the switching oscillation of SiC MOSFET,the tunable negative voltage level shifter driving circuit with passive devices is designed based on the characteristics of SiC MOSFET.The advantages of the driving circuit are fast switching speed and preventing the disturbances.The use of passive devices leads to the lower cost,the simpler structure and easier to integrate.Furthermore,considering the lower threshold gate voltage range and the crosstalk problem in the bridge circuit,the thesis improves the driving circuit based on the structure of the driver and miller clamping,i.e.the passive triggered clamping circuit is proposed.Comparing to the traditional miller clamping circuit,the proposed structure takes advantages of less complexity in control and suppressed the crosstalk problem in the bridge circuit effectively.Finally,the prototype for C3M0065090 J of CREE's SiC MOSFET is built in the lab to verify the fast switching performance and stability of the driver.The double pulse test and cross talk performance of the proposed driver have been done.In addition,the switching speed and reliability of the proposed gate driver under different conditions had been verified,and the influence of the gate resistance is also tested and analyzed.