Research On Parallel Current Sharing Technology Of SiC MOSFET Power Module

As a wide bandgap material device,silicon carbide devices have the characteristics of low loss,high frequency,high withstand voltage,etc.,and are being increasingly used in electric vehicles,new energy power generation,industrial power and other fields,while SiC MOSFET power modules is gradually becoming the mainstream of high-power applications.Due to the defects of SiC material structure and process,the single-tube current level of SiC MOSFET is much lower than that of Si IGBT.Therefore,SiC MOSFET power modules often use multi-chip parallel packaging to improve the current level of SiC MOSFET power modules.The problem of current unbalance of parallel SiC MOSFETs will lead to unbalanced junction temperature distribution of SiC MOSFETs,which seriously affects the reliability of SiC MOSFET power modules.Therefore,it is of great research value to improve the current sharing performance of SiC MOSFET power modules.This paper mainly studies the current sharing problem of multi-chip parallel SiC MOSFET power modules,aiming to improve the current sharing performance of SiC MOSFET power modules through the chip selection principle and the layout design of SiC MOSFET power modules.The research work of the paper is as follows:(1)The parallel current sharing characteristics of SiC MOSFETs are analyzed,the parallel current sharing model of SiC MOSFETs is established,and the screening principles suitable for SiC MOSFET power modules are proposed.The basic operating characteristics of SiC MOSFETs are analyzed,and the effects of device parameter differences and loop parasitic parameter differences on the transient current sharing of parallel SiC MOSFETs are analyzed through LTspice,and the main factors in each influencing factor are determined.According to the SiC MOSFET switching process,the mathematical model of SiC MOSFET parallel transient current sharing is established,calculating the influence of various influencing factors on the transient current sharing.The screening algorithm and objective function of SiC MOSFET are determined.The SiC MOSFETs in which the transconductance parameters have differentials are parallel to uniformly result in the inconsistency of the parametronic parameters due to the layout design,thereby optimizing the transient current sharing performance of the SiC MOSFET power module.Experiments on discrete SiC MOSFETs to verify the validity of the screening principle.(2)By designing and optimizing the layout of the SiC MOSFET power module,the current sharing capability of the SiC MOSFET power module is improved.First,according to the magnitude relationship of the parasitic parameters affecting the parallel transient current sharing of SiC MOSFETs,the layout design of the SiC MOSFET multi-chip parallel power module is designed,and the three-dimensional modeling is carried out,and the parasitic inductance is extracted by importing 3D model into ANSYS Q3 D.Secondly,the parasitic parameter matrix is imported into LTspice for double-pulse circuit simulation to obtain the transient current distribution of parallel SiC MOSFETs,and the layout design of SiC MOSFET power modules is iteratively optimized according to the simulation results,and a SiC MOSFET power module with better current sharing performance is designed.Finally,the thermal performance of the module is designed,the substrate material and solder material of the power module package are selected,the thermal resistance of the power module is calculated,the thermal simulation of the designed SiC MOSFET power module is carried out,and the thermal performance of the module is evaluated.(3)The effect of screening principle and layout design to improve the current sharing performance of SiC MOSFET power module is verified by experiments.Double-pulse experiments are carried out on the packaged SiC MOSFET power module to verify the effectiveness of the layout design.