Research On Short Circuit And Overload Protection Method And Chip Implementation Of SiC Mosfet

With the development of power electronics technology,traditional power devices based on material performance limitations may not be able to meet the requirements of system efficiency,power density and switching frequency,and the emergence of power electronic devices based on wide band semiconductor materials such as silicon carbide(SiC)and gallium nitride(GaN)has brought a new opportunity.They are widely used in high-voltage,high-frequency and high-power applications due to their high switching frequency,low switching loss and high-voltage resistance,but their weak short-circuit withstand capability make their protection circuits more demanding.Therefore,this thesis investigates a fast and comprehensive,monolithic integrated short-circuit and overload protection scheme from the failure mechanism of SiC MOSFET.Based on the detailed analysis of short circuit characteristics and failure mechanism,this thesis proposes a multi-scale protection method for SiC MOSFET based on dI/dt short circuit protection and energy accumulation based overload protection from the nature of device failure;The overall strategy of protection is determined,using dI/dt detection to achieve short-circuit detection protection for fast protection and energy detection to achieve overload detection protection to avoid long time heat accumulation making device failure;design the corresponding integrated circuit scheme based on the proposed protection method,analyze the principle of the circuit in detail,and then design each unit module of the protection circuit,including bandgap reference,linear regulator,driver circuit module,comparator,latch circuit and other units.A new single BJT branch bandgap reference is proposed in the design of each module cell circuit,where the voltage is generated by the difference between the gate source voltage ΔVGS of two MOS tubes operating in the subthreshold region proportional to the absolute temperature,and the base-emitter voltage VBE of BJT with negative temperature coefficient is added to produce a zero temperature coefficient voltage.Compared with the conventional BGR,the proposed BGR has fewer BJT and passive components,1/3 of the conventional chip area,and 95%lower power consumption.Finally,the whole circuit is designed,simulated,layout drawn and taped-out based on the VIS 0.5μm 700V BCD process platform.The PCB board and test circuit are fabricated and tested on the short-circuit and overload experimental platform to verify the correctness and feasibility of the short-circuit and overload protection method proposed in this thesis.The test results show that when the SiC MOSFET is short-circuited,the circuit can detect the fault at about 150ns and safely shut down the device,when the SiC MOSFET is overloaded,the fault can also be detected in time and shut down,and it can achieve fast and effective protection under different fault conditions,which is fast and comprehensive.