Research On Microarc Oxidation Pulsed Power Supply Based On SiC MOSFET

The microarc oxidation pulsed power supply is not only a key piece of equipment,but also a key factor which influences and restricts the development of the microarc oxidation technology.However,the microarc oxidation pulsed power supply has some shortcomings at the present stage,and there are few studies on the characteristics improvement of this power supply.Based on this background,a microarc oxidation pulsed power supply prototype is developed in this paper,which adopts the PS-FB-ZVZCS converter with active clamp circuit as its main circuit,the second order PWM SMVC as its control method,and the SiC MOSFET as its switching device.Based on this prototype,some characteristic researches of the microarc oxidation pulsed power supply such as cross-talking effect and impulse-load characteristics are analysed.To solve the problem of serious parasitic oscillation existing in secondary output rectifier diode of the full-bridge converter,a method of adding an active clamp circuit to secondary side of the power transformer is adopted,which can not only realize zero current switching for switches of lagging leg,but also reduce the parasitic oscillation at output rectifier diode.This paper analysed the soft switching principle of this converter and modeled the equivalent circuits of the converter and diode.On the latter basis,the production and reduction principles of parasitic oscillation are both in-depth analysed.Besides,the influence on reduction and the design considerations of several key parameters are discussed in detail.To solve the problem of the cross-talking effect through SiC MOSFETs' high-frequency 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 slight and 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.To meet the demand for output voltage stability of the pre-stage converter while the impulse load is working,two methods for improving the impulse-load characteristics of pre-stage converter are proposed.One is improving the main circuit structure and blocking the PWM drive signal with no-load,which both can eliminate the overvoltage at no-load of pre-stage converter.The other is adopting second order PWM SMVC as its control method,which can improve the dynamic response rate and stability of pre-stage converter.Effectiveness of the above methods is verified by PSIM simulation analysis.On the basis of theoretical and simulation analysis,a 6k W/300 V,50k Hz experimental prototype was built.The experimental results show that the experimental prototype meets the requirements of the expected target with the proposed methods,which verifies the correctness of theoretical analysis.