Research On Efficient Use Of High Temperature SiC BJT In DCDC Converter

With the development of power electronics technology,the field of application of power electronics technology has gradually broadened.Power semiconductor switching devices as core components in power electronic systems have also made great progress in recent years,especially the development of third-generation wide band gap semiconductor devices for power electronics systems to high power density,high energy efficiency.The direction of development has laid an important technical foundation.At present,the rapid development of space exploration,deep oil and gas exploration in underground space,electric vehicles,and multi-electric/all-electric aircrafts have increased the demand for new high-performance power electronic systems.In this paper,a 1.15kW 500kHz step-up converter was built using Silicon Carbide(SiC)Bipolar Junction Transistor(BJT).Aiming at the shortcoming of large driving loss of SiC BJT,an intelligent driver is designed to make the driver can accurately follow the change of the collector current in real time to provide suitable drive current when the load changes in the converter.The first chapter makes a detailed comparison of the advantages and disadvantages of SiC and Si materials,and introduces the currently commercialized SiC devices.From the perspectives of reliability,cost,performance and other aspects,this paper finally selected SiC BJT as the research object.The second chapter mainly analyzes the characteristics of SiC BJT.Starting from the output characteristics,temperature characteristics,etc,the basic properties of SiC BJT are studied,which lays a foundation for the later development of SiC BJT converters.The third chapter focuses on the current SiC BJT driving loss,which restricts its widely use.This chapter elaborates the design method and design ideas of the SiC BJT driving circuit at present,and analyzes the loss of each part of the existing driving circuit.,and points out the limitations of different drive schemes.Based on the dual-voltage driver circuit,a new type of intelligent driver is proposed and designed.The collector current of the SiC BJT is acquired by using a current Hall sensor and its output to the base of a small Si BJT to control the Si BJT collector current.Through this loop control,the driver current can accurately follow the collector current in real time.The change causes the driver circuit to provide a suitable driver current when the load changes in the converter,drastically reducing the overdrive current.The experimental results show that the loss of smart driver can be reduced by 83.8%when the collector current is reduced from 6A to 2A compared to the dual-voltage drive circuit.By comparing with the total loss of SiC MOSFETs,under the same conditions,the intelligent driving loss and device loss of SiC BJT are only 7.28%larger than those of SiC MOSFETs.Proved the applicability of the new intelligent drive in the actual circuit.The fourth chapter describes in detail the design process and experimental verification results of a high-temperature high-frequency DC/DC Boost converter.A 100V/240V,500KHz,1.15KW boost converter is built.This paper compares the efficiency of the boost converter when the operating temperature of the SiC BJT in the converter changes from 25 ℃ to 200℃.The results show that the efficiency of Boost converter can reach 97.14%even at 200℃,which proves the stability of SiC BJT under high temperature and high frequency conditions.Finally,the research work of this paper is summarized and prospected.