Performance Analysis And Multi-chip Parallel Connection Of SiC Power Devices

Silicon carbide and other power electronic devices have shown great potential in the field of power electronic applications.However,due to the lack of sufficient understanding of the performance characteristics of these new materials,there are still considerable problems in the current practical application.In order to give full play to the advantages of these new materials in the system safely,we need to have a thorough understanding of the dynamic and static characteristics,circuit application performance,long-term operation stability and reliability of these devices.Among the new material power electronic devices,silicon carbide(SiC)MOSFET is widely used in energy,power,electric vehicles and other high-power applications because of its simpler and more reliable driving mode,more prominent performance characteristics and wider application scope.It is the most important new material power electronic device,and considered as an ideal substitute for traditional Si IGBT devices.Due to the limitation of single chip power capacity,multi-chip parallel connection is a common way of SiC MOSFET power module.However,there is a conflict between chip cost and performance requirements in multi-chip parallel connection.Quantitative research is needed to solve these problems,in order to further optimize the number of chips and the efficiency of the module.In addition,the most common basic circuit topology of SiC MOSEFT power module is half-bridge circuit.Crosstalk exists between upper and lower transistors in this circuit structure.The high-speed hard switch of SiC MOSFET aggravates the problem.Therefore,for multi-chip parallel SiC MOSFET power module,we need to further study and improve its basic circuit topology to better suppress crosstalk under high-speed hard switching.Based on the scientific problems in the above-mentioned professional fields,this paper records the following research work of the author:Firstly,the static and dynamic characteristics of commercial SiC diodes,SiC MOSFET,SiC JFET,SiC BJT and GaN HEMT as well as silicon Cool MOS(as a comparison)are tested and analyzed.Their performance characteristics are summarized and compared.At the same time,the author evaluates the change of on-resistance of SiC MOSFET under high temperature through high temperature storage,high temperature operation and self-recovery experiments of SiC MOSFET,and studies the high temperature stability of SiC MOSFET.In particular,in the aspect of the stability of SiC MOSFET,the author carries out the modeling,simulation and experimental verification based on the measured data for the first generation commercial SiC MOSFET device produced by Cree Company,infers its thermal run away temperature,and evaluates the thermal run away temperature of subsequent generations of SiC MOSFET,which provides a quantitative basis for the wide application of these devices in various fields.The safety index has great practical valueNext,the author completes the process of designing,manufacturing,testing and evaluating the multi-chip parallel SiC MOSFET module.Firstly,the design process of material selection,Layout impedance analysis,built-in decoupling capacitance calculation,chip spacing and analysis of a 4-chip parallel SiC MOSFET is introduced in detail.Then,the performance of a 6-chip parallel SiC MOSFET module at different ambient temperatures(simulated vehicle ambient temperature)is tested on a 20 kW Boost test platform,and the ambient temperature is evaluated.Finally,the performance of SiC MOSFET module is evaluated step by step under different chip number,switching frequency,load and case temperature conditions:1.The model of SiC MOSFET is established by using distributed gate impedance instead of traditional centralized gate impedance,and its accuracy is verified by experiments;2.The Rogowski coil is tested by using this model as a standard.The accuracy of switching loss obtained by current loop measurement determines the rationality of data obtained by this method and the establishment of switching loss fitting model;3.Then,combined with the above-mentioned model and conduction loss fitting model,the overall loss fitting data model is obtained;4.The steady-state junction temperature and power consumption fitting data model is established based on the measurement;5.The operational performance of various modules under different power conditions.The loss and thermal stability data fitting model can be tested and verified.6.Finally,the performance of the module is evaluated and predicted based on the above two data fitting models.At the same time,the performance of SiC MOSFET and Si IGBT is compared in terms of efficiency and active area.In the last part of this paper,aiming at the problem of cross-talk between upper and lower tubes in high-speed hard switching of SiC MOSFET half-bridge circuit,the influence of different circuit parameters on gate voltage fluctuation caused by cross-talk and the effect of different clamping circuits on cross-talk suppression are analyzed,and the effect of loop inductance between miller clamping and switching devices on the clamping effect is studied.For the application of multi-chip parallel half-bridge module,this paper proposes a distributed miller clamp driver layout in the integrated module.The experiment proves that this method can not only suppress crosstalk,but also improve the crosstalk consistency of each device paralleled in the half-bridge power module,which greatly improves the overall crosstalk immunity of the hard switch application of the power module.Through the above research work,the author seeks a breakthrough in theory and practice in view of the difficulties encountered in the application of new material power electronic devices represented by SiC MOSFET,and finds out the thermal escape temperature related to the reliability of devices and establishes a closer approach.