Research On High Reliability Driving Technology Of SiC MOSFET

Due to the physical properties of Si materials,Si-based devices have been unable to meet the performance requirements of power devices in terms of power density and switching loss of charging devices.As a typical representative of the third generation of wideband gap semiconductors,SiC MOSFET has excellent characteristics of high voltage resistance,high temperature resistance and low switching loss.Compared with Si devices,SiC MOSFET applied to charging equipment will greatly reduce the size of the equipment,improve the power density and efficiency of the equipment.However,due to the introduction of stray parameters in the packaging and design of SiC MOSFET,it is easy to generate gate crosstalk voltage in switching transients when it is applied in the bridge arm circuit.At the same time,the rated voltage withstand value of commercial SiC MOSFET is up to 1700V,so it is difficult to be directly applied to medium and high voltage charging equipment.In order to solve the above problems,the main research contents of this paper are as follows:Firstly,the characteristics and development process of SiC devices are described in this paper,and the research status of bridge arm crosstalk and series pressure imbalance in the application field of SiC MOSFET is summarized.Secondly,the influence of the nonlinearity of the internal junction capacitance on the switching characteristics of SiC MOSFET is analyzed.The crosstalk mechanism of SiC MOSFET half-bridge circuit is described,and the crosstalk voltage model is established.The influence of driving parameters such as gate source capacitance and common source inductance on the crosstalk peak is analyzed.At the same time,the cause of pressure imbalance in series SiC MOSFET is analyzed based on the two-tube series half-bridge circuit,and the influence of parasitic inductance on the voltage partitioning characteristics of series SiC MOSFET is analyzed.Then,to solve the crosstalk problem of SiC MOSFET bridge arm,a new high disturbance rejection drive circuit is proposed in this paper.A passive miller clamp circuit with reverse clamping function is designed by passive components and a self-generated negative voltage circuit is designed based on RC parallel voltage divider structure to achieve crosstalk suppression function.The transient model of the proposed drive switch was established to analyze its operating mode in detail,and the parameters of the drive circuit were designed.The performance of the proposed drive was simulated and verified based on LTspice.The experimental platform of high disturbance rejection drive with synchronous Buck converter as the main circuit was built,and the performance of the proposed drive was verified experimentally.Finally,in view of the unbalanced partial voltage in the half-bridge circuit of series SiC MOSFET,this paper modeled and analyzed the pressure imbalance in series operation of SiC MOSFET based on the double-tube series synchronous Buck circuit,and designed an auxiliary voltage equalizer applied to series SiC MOSFET.At the same time,the proposed auxiliary voltage equalizing circuit is combined with the crosstalk suppression circuit of the improved disturbance rejection drive,and an auxiliary voltage equalizing drive scheme applied to the half-bridge circuit of series SiC MOSFET is designed in this paper.Based on the synchronous Buck circuit with two tubes in series,the simulation verifies the crosstalk suppression and voltage equalizing ability of the proposed auxiliary voltage equalizing scheme.