Research On Hybrid DC/DC Converter Based On SiC Power Device

Electric vehicles have the advantages of zero emissions,high energy conversion efficiency,and low noise,and have become one of the mainstream directions for the development of the automobile industry.Charging power sources as a core device of energy supply for electric vehicles,have received extensive attention from domestic and foreign scholars.This paper focuses on the research of the DC/DC converter topology and soft switching technology in the large-power charging power supply.First of all,this paper aimes at the technical requirements of high power density and wide range output voltage of the large-power charging power supply,based on the analysis of the disadvantages of two DC/DC soft-switching circuit topologies of phase-shifted full-bridge converters and LLC resonant converters,a novel hybrid DC/DC converter is proposed.The proposed converter is composed of an auxiliary half-bridge LLC resonant converter and a phase-shifting full-bridge converter and the phase-shift-frequency control method is used to expand the soft-switching range and voltage regulation range.The phase-shift full-bridge converter is used for main power transmission,and its lagging bridge arm is also used as one bridge arm of the half bridge LLC converter which assists the phase-shift full-bridge commutation process.In addition,the clamp diodes in the primary side of the transformer is adopt to suppress voltage spike oscillation.In this paper,the working principle of the novel hybrid DC/DC converter under two control modes of phase shift and variable frequency is analyzed,and the soft-switching conditions,output voltage gain range,duty cycle loss,voltage spike oscillation of secondary rectifier diodes are analyzed.Secondly,the application of wide bandgap semiconductor devices is studied.The difference between the junction capacitance of SiC MOSFET and Si MOSFET and its effect on the switching characteristics are compared and discussed.The crosstalk issues and suppression methods of the circuit bridge arm under high frequency working conditions are analyzed,and the drive scheme of SiC MOSFET is designedThirdly,on the basis of theoretical analysis,the core circuit parameters of the converter are designed,including the phase-shift full-bridge transformer,resonant inductor and LLC resonant elements.The power devices are calculated and selected,and some peripheral circuits and programs of the control system based on TMS320F2808 are designedFinally,in order to further verify the working principle of the converter and the rationality of the parameter design,the simulation analysis is carried out with the ORCAD16.5 simulation tool,and an experimental prototype is built.The simulation and the experimental results show that the novel hybrid DC/DC converter can effectively extend the range of the soft-switching operation and output voltage regulation.Moreover,it can reduce loss of duty cycle and suppress the voltage spike oscillation of the secondary rectifier diode.