Research On Si IGBT/SiC MOSFET Hybrid Switch And Its Application

In recent years,the high power density,large power handling capacity,high efficiency and high reliability of the power electronic devices are required to cope the more and more complex working conditions and application environment.Research and development of new type power electronic devices with high frequency,high reliability,and high current capacity technology plays a vital role in developing our independent innovation device technology and industry.The Si IGBT/SiC MOSFET hybrid device combines the high switching frequency and low switching loss characteristics of SiC MOSFET with the large current carrying capacity and low cost advantages of Si IGBT.It can realize high performance power electronic devices with higher current handling capacity and lower cost,break the technical bottleneck of single Si IGBT and SiC MOSFET power devices,which is ensential to meet the requirements of high reliability,large current capacity,low cost and high voltage power electronic devices for high-performance power electronic equipment.This paper is supported by the National Natural Science Foundation of China.It focuses on the Si IGBT/SiC MOSFET hybrid device and extensively studies the gate control optimization,thermoelectric coupling power loss model,chip sizing optimization and application performance of the hybrid switch,which gives new ideas for the design and manufacture of high performance power devi ces and provides the theoretical and technical support for the high frequency,high reliability,large current capacity and low cost power devices engineering and practical application.The research focus and achievements are mainly reflected in the follow ing aspects:(1)Four specific gate control patterns are proposed for the Si IGBT/SiC MOSFET to achieve the optimal control of the hybrid switch.The novol cost-effective integrated gate driver is proposed and the working principle of the integrated gate driver is analyzed.The prototype of the gate driver is developed and the feasibility and effectiveness of the integrated gate driver are verified through experiments.Finally,the thermoelectric coupling power loss models considering the gate control delay times are developed,and a hybrid switch based DC/DC Buck converter is built to verify the accuracy and validity of the power loss model.(2)The minimum power loss control,balanced junction temperature control and multi-objective optimization control strategy are proposed based on the dynamic gate control delay time adjustment.The minimum power loss control of the hybrid switch can reduce the total power losses of the hybrid switch and improve the conversion efficiency of the hybrid switch based conver ter.The balanced junction temperature control can achieve the balanced junction temperature between the Si IGBT and SiC MOSFET,which help reduce the maximum junction temperature of the hybrid switch and increase the maximum output power handling capacity of the hybrid switch based converter.Finally,the multi-objective optimization control is proposded to achieve high conversion efficiency,large output power handling capability and safe operation of the Si/SiC HyS over a wide load range in power conversion applications.In the hybrid switch based 9kw DC/DC Buck converter application,using the proposed optimal gate control strategy,the hybrid switch shows significant efficiency improvement,maximum junction temperature reduction and maximum out put power handling capacity increment compared to the conventional fixed gate control delay time strategy.(3)Firstly,the influence of the current ratio between the SiC MOSFET and the IGBT inside the hybrid switch on the characteristics of hybrid hybrid switch is analyzed.The experimental results show that the power loss of the hybrid switch is decreased with the increase of the current ratio,while the short circuit withstand capacity of the hybrid switch is not affected by the current ratio.Then a generalized power loss model for the Si/SiC hybrid switches with total power loss and junction temperature as outputs and SiC device size as a continuous input variable is proposed.Based on the power loss model,a methodology to minimize the internal SiC MOSFET's size while optimizing the total power loss of hybrid switch and ensuring its maximum junction temperature still below 150~oC is developed.The proposed loss model and optimization method provide theoretical basis and technical support for the enginee ring and practical application of the new Si IGBT/SiC MOSFET hybrid power electronic devices with high frequency,high reliability,large current capacity and low cost.(4)Contrasitive analysis between the Si IGBT/SiC MOSFET hybrid switch(HyS)and the Si IGBT/SiC diode pair(HyP)in device electrical characteristics,total cost and converter application are presented.The improved power loss model is developed for these two hybrid devices in voltage source inverter(VSI)applications.The experiment results show that the peak efficiency of the HyS is about 0.9%higher than that of the HyP solution.Under a 5k W load,the maximum junction temperature of the HyS is about 60°C lower than that of the HyP device.The maximum output power of HyS is about 40%higher than that of Hyp.When the output power of the VSI is kept to be 2 k W,the switching frequency of the HyS-VSI is 1.5 times to the HyP solution.Simulation and experiments demonstrate that the HyS can achieve higher efficiency,lower device junction temperature,larger output power capacity,and higher switching frequency than conventional HyP solution at comparable cost.It is a very potential power device type in the application of high-performance converter.