Contrastive Research Of DC-DC Converters For Cars Based On Different Semiconductor Power Device

In recent years,the development of new energy vehicles industry has received great attention with the emphasis on energy conservation,emission reduction and new energy.Compared to hybrid electric vehicles and fuel cell electric vehicles,all-electric vehicles become more popular because of their lower emission,lower power cost and higher energy conversion capability.However,the shortage of battery technology makes people have to focus on how to improve the efficiency of power converter.In the matter of device research,Si power device is approaching its theoretical limit in power applications.SiC power device is better than the Si power device in many aspects,so it is gradually applied in the field of electric vehicle power converter designing.However,if the electromagnetic compatibility design is not properly designed,the car's power unit and electronic products inside would be damaged seriously.Therefore,on the basis of the higher conversion efficiency the SiC power device brings to,whether it will cause excessive electromagnetic interference is also a key problem deserving research for us.Based on the actual working conditions of electric vehicles,a 400V/12 V DC-DC converter is designed.In order to help the DC-DC converter to obtain ideal conversion efficiency in a wide range of load conditions,the phase-shift full bridge ZVS-PWM circuit is chosen as the main circuit topology.To make the circuit easier to realize and efficient,a resonant inductance and two clamp diodes are added.After selecting the circuit structure,the key parameters of circuit are designed respectively.The control circuit and the driving circuit are determined.Then the SIMPLIS simulation software is used to carry out the simulation analysis.Unlike the imported ideal devices in the simulation,the actual devices have extra features inevitably,and these features will lead to produce all kinds of electromagnetic interference(EMI)and affect the other electronic devices in the car.This thesis emphatically analyzes the EMI caused by the power MOSFET and the output rectifier diode in DC-DC converter.After that,a comparison is finished with the SIMPLIS Fourier analysis function between Si MOSFET and SiC MOSFET.Finally,two model machines are set up respectively based on Si and SiC power devices.The test of conversion efficiency is done.It proves that SiC power devices help improve the efficiency of converter.Also,the converters' component conduction EMI was tested by conduction voltage method.Both converters can pass the EMI standard.