Design Of 3.3kV Fast Recovery Diode

As one of the core components of IGBT module,Fast Recovery Diode has the advantages of reducing the dynamic loss of the module,avoiding voltage overcharge and oscillation during hard switching,and improving the operating frequency of the system,so as to protect the main switching devices and improve system reliability.In the field of rail transit,the voltage level of traction grade IGBT module is usually above 3.3kV,and the reverse recovery characteristic and avalanche robustness of the diode in the module will have a great influence on the characteristics of IGBT.However,the current domestic research on fast recovery diode is still focused on the consumer electronics field of medium and low voltage,and the high voltage field needs to be developed urgently.Therefore,it is of great significance to design a 3.3kV fast recovery diode.In this thesis,the device structure and working principle of PiN diode are analyzed in detail,and the compromise relationship between static characteristics and reverse recovery characteristics of diode is studied by combining relevant theories and simulation results.Subsequently,a 3.3kV fast recovery diode device with buffer layer structure was proposed,and the floating field limiting ring terminal of the device was designed.It was found that the voltage tolerance level of multiple field limiting rings could be balanced by adjusting the doping position and width of the field limiting ring,and the peak electric field on the terminal surface could be reduced to achieve the best voltage tolerance of the terminal.Then,the avalanche robustness of the diode is studied,and a novel 3.3kV fast recovery diode with local life control and field charge extraction structure is proposed.The control of the carrier concentration distribution in the diode subjected to reverse current is realized.On the basis of ensuring the static characteristics,the peak electric field in the device is significantly reduced,and the avalanche robustness and reverse recovery characteristics are improved.Simulation results show that the on-state voltage drop of the designed fast-recovery diode is1.9V(@128.6A/cm~2)and the breakdown voltage is 4857V.Under typical application conditions,the reverse recovery peak current is 1756A,the reverse recovery time is 1160ns,the reverse recovery softness is 4.5,the recovery charge is 875μC,and the reverse recovery energy is 788mJ,which meet the design requirements.