Application Of SiC MOSFET In Bridge Converter

The constant pursuit of higher power density and volume miniaturization of power electronic devices urgently requires the switching frequency of power electronic devices to continue to increase.Third-generation semiconductor devices based on silicon carbide and gallium nitride have raised the limits of secondgeneration semiconductor materials based on silicon.The research on silicon carbide devices is in the initial development stage.At present,the application research on silicon carbide devices is mainly focused on modeling and characteristic testing,and the actual application research is not much.Based on this background,this paper studies the practical application of SiC MOSFET,parasitic oscillation,loss calculation and crosstalk effects in bridge circuits.For the influence of parasitic parameters on the oscillation effect of SiC MOSFET switching process.Analyze each stage of the SiC MOSFET switch process at the circuit level to derive the peak and frequency formulas of the on-going current oscillation and the peak and frequency formulas of the voltage oscillations during the turn-off process.A double-pulse test circuit is built in the LTspice simulation platform to verify the influence of the parameters involved in the above formula on the parasitic oscillation effect.Finally,according to the suggestions given above,a double-pulse test circuit is designed,which proves that it can better control the oscillation effect during the switching process of SiC MOSFET under reasonable application.For the calculation of the switching loss of SiC MOSFET,the fundamental problem is to explore the effect of the output capacitance of SiC MOSFET on the switching loss of SiC MOSFET.In view of this,from the theoretical level,the internal current flow of the device during the turn-on and turn-off process is analyzed respectively.It is found that the output capacitance of the SiC MOSFET repeatedly stores and releases the charge during the switching process,but does not consume the charge,so there is no loss.A dynamic loss test circuit is built in the LTspice simulation platform,which proved that the output capacitance of the SiC MOSFET did not affect the switching loss of the SiC MOSFET.To solve the problem of the cross-talking effect through SiC MOSFETs' highfrequency switching in the phase-leg configuration,the operation conditions and switching situations of SiC MOSFETs in the phase-shift converter are in-depth analysed,and the parsing expressions of cross-talking effect in both leading leg and lagging leg are derived.A conclusion that cross-talking effect in leading leg is slightand only positive cross-talking effect exists in lagging leg is presented.On this basis,an active miller clamp circuit which can reduce the cross-talking effect in phase-leg configuration well is adopted.Finally,the driver of SiC MOSFET is completely designed.On the basis of theoretical analysis and simulation verification,a 800 V / 100 A double-pulse test circuit is built,and an experimental prototype with an output of6 k W / 300 V and a switching frequency of 50 k Hz is produced,and the above research contents are verified by experiments.The experimental results show that the proposed method can work normally under the target power condition and verify the correctness of the theoretical analysis.