Key Technologies Of High Frequency Gate Driving And Protection For SiC Device

With the development of wide band-gap devices,silicon carbide(SiC)and gallium nitride(Ga N)devices have been widely used in aerospace power supply,solid state transformer,wireless power transmission,and grid-connected inverters.SiC MOSFET is the most widely used among the wide band-gap devices,which has the advantages of high switching frequency,high temperature resistance and small conduction losses.The designing of SiC MOSFET gate driver has become a hot topic of current research.The problems of large gate driving losses,short short-circuit withstand time and bridge arm crosstalk in high frequency driving of SiC MOSFET are studied in this thesis.To solve these problems,this thesis proposed a series of SiC MOSFET gate driver.Firstly,the SiC power device is introduced and the status of SiC MOSFET in SiC power devices is pointed out.On this basic,the rsaonant gate driver technology,shrot-circuit protection technology and phase-leg crosstalk suppression technology at home and aboard have been summaried.According to the problems existing in the current high-frequency driving of SiC MOSFET,this thesis aims to design the high-frequency gate driver and short-circuit protection circuit of SiC MOSFET,and study the working performance of these gate driver.Secondly,the resonant gate driver for SiC MOSFET is studied,and two kinds of resonant gate drive suitable for SiC MOSFET are proposed.The working principle of two kinds of resonant gate driver are introduced,and the key waveforms of each mode are analysed.The components of the gate driving losses of the resonant gate driver are analyzed,and the calculation formulas of the losses of each part are given.The selection of inductance and capacitance of resonant gate drive circuit is introduced at the same time.The simulation model and hardware platform of the resonant gate driver are built.The simulation and experiment results show that the proposed resonant gate drivr can effectively realize the SiC MOSFET drive and greatly reduce the drive losses.Thirdly,the short circuit protection for SiC MOSFET is studied.Two types of short-circuit faults are introduced,and the voltage and current waveforms under the two kind of faults are given.Four short-circuit detection methods are introduced,and their advantages and disadvantages of these detection methods are analyzed at the same time.Due to the poor anti-interference performance of soft turn-off mode under short-circuit fault,the scheme of decreasing gate voltage short-circuit protection is proposed,and the two stage turn-off mode is adopted to realize the short-circuit protection.The short circuit testing platform is built to test the performance of soft turn-off mode and two stage turn-off mode under the hard switching fault.The experimental results show that the two stage turn-off mode can improve the anti-interference performance of the short circuit protection,but also reduce the short circuit energy.Finally,based on the problem of crosstalk phenomenon in SiC MOSFET phase-leg configuration,the source of crosstalk phenomenon is analyzed,and the relationship between crosstalk voltage,gate capacitance and gate resistance is deduced.At the same time,a multi-level gate driver for SiC MOSFET is proposed,which use negative turn-off voltage to suppress the positive crosstalk voltage and zero turn-off voltage to suppress the negative crosstalk voltage.The simulation model and hardware platform are built,and the multi-level gate driver is applied to the synchronous Buck converter.The simulation and experimental results verify that the proposed multi-level gate driver can effectively suppress the phase-leg configuration crosstalk phenomenon.