Research On The On-off Behavior Of SiC MOSFET And Its Failure Diagnosis

As a new wide band gap semiconductor material,silicon carbide(SiC)power device is attracting more and more attention in power electronics industry due to its excellent physical and electrical properties.The SiC MOSFET module is considered to be the most likely to replace the Si IGBT module which is widely used now because of its low conduction resistance and high switching rate.In this paper,the bsm180d12p3c007-e SiC MOSFET module of Rohm is used to study the switching behavior characteristics and the fault detection methods.SiC MOSFET high-speed switching process is very sensitive to parasitic parameters.The high frequency oscillation and high spikes will bring adverse effects to the electromagnetic compatibility and the efficient and safe operation of devices and power electronic devices.This paper researchs the SiC MOSFET switching behavior and the high frequency oscillation.The simulation and experimental analysis the influence of different gate resistance,gate capacitance,drive voltage and stray inductance to the switching transient of SiC MOSFET may provides support for the application of SiC MOSFET in the future.Short circuit protection is an important aspect of the reliability application of SiC MOSFET.The low short circuit tolerance time requires higher short-circuit protection rate.By analyzes the influence of driver voltage and gate resistance on short circuit current,this paper proposes a method to suppress short circuit current,and then designs a PCB Rogowski coil and its sensing circuit for short circuit protection.Simulation and experiment verify the correctness and validity of the short circuit modulation and protection method.The design of the modulation circuit will reduce the short power loss and the PCB Rogowski coil sensor circuit can reproduce drain source transient current well and cut down the short circuit time to 2us.The voltage endurance capability of SiC MOSFET gate oxide is poor.Under high driving voltage,the high frequency oscillation caused by SiC MOSFET high-speed switching process is likely to cause gate failure,and jeopardize the safe operation of the system.So far,there are few studies on gate fault principle and its detection methods.In this paper,the factors cause gate fault are discussed,which are divided into gate short circuit fault and gate open fault.A method based on gate charge detection is proposed to quickly diagnose and identify the fault behavior according to the change of gate charge when the gate fault occurs.The simulation and experiment show that the method can diagnose gate fault quickly and identify the fault category in a switching period.