Research On Modeling Method Of Switching Behavior Of Gate-controlled Power Devices In Parallel

In recent years,with the development of the third generation of wide band gap semiconductor materials,Siicon Carbide Metal Oxide Semiconductor Field Effect Transistor(SiC MOSFET)has been initially commercialized.At present the current capability of single-die SiC MOSFET is low due to the low yield of SiC chip.Therefore,devices-parallel is usually adopted to meet the requirements of high-power applications.There are two kinds of devices-parallel solutions.From the perspective of performance,the advantages of high frequency and low on-resistance can be fully exploited by parallel multiple SiC MOSFET.From the aspect of cost-performance,the Si/SiC hybrid switch composed of high-current Si IGBT and low-current SiC MOSFET can achieve a trade-off between cost and performance.In devices parallel application,due to the deviation of device parameters and circuit stray parameters,there is the problem of uneven flow between devices,especially in the switching process;And the switching delay of Si/SiC hybrid switch is also a key factor affecting the switching loss of the device.Therefore,it is of great significance to study the prediction model of switching behavior and loss distribution of parallel devices.In this thesis,a new analysis method is proposed for the switching process of gate-controlled power devices.Taking SiC MOSFET as an example,the switching transient process of gate-controlled power devices is defined as the Voltage Souce Mode(VSM)and Current Souce Mode(CSM)based on the circuit equivalence principle.Based on the principle of Finite State Machine(FSM),a new unified modeling method for the switching behavior analysis of gate-controlled devices in parallel is proposed in this thesis,and the switching behavior models for SiC MOSFETs in parallel and Si/SiC hybrid switch are established respectively.According to the device characteristics and circuit parameters required by the model,this paper proposes an improved SiC MOSFET and IGBT device characteristics and circuit parameters extraction method,which fully considers the device nonlinear junction capacitance characteristics in the wide voltage bias range,to ensure the model has a good accuracy in the whole switching process.In order to verify the effectiveness of the modeling method proposed in this thesis,a double-pulse test experimental platform based on gate-controlled devices in parallel is built.The switching behavior and power loss of SiC MOSFETs in parallel under different working conditions and Si/SiC hybrid switch with different switching delays were tested and analyzed,respectively.Comparison results show the switch voltage waveform and current wave has the very good coincidence,and loss of error remain in an acceptable range,and demonstrate the effectiveness and scalability of the proposed method based on finite state machine,which provides an important reference for the behavior analysis and loss estimation of devices' parallel switches.