A Study On Driving Circuit For SiC Bipolar Power Semiconductor Devices

Power semiconductor devices based on wide-bandgap semiconductor materials such as SiC(silicon carbide)have made significant progress.Compared with Si-based power devices,SiC power devices are advantagous in terms of high blocking voltage,large current capacity,high switch frequency,and high temperature tolerance.These advantages make SiC power devices gradually replace Si power devices in modern power electronics.The main purpose of this thesis is to design a driving circuit that can drive SiC bipolar power devices short to realize turning on and turning off.This thesis focuses on short rising time and falling time of driving current.In this thesis,I firstly introduces current situation of SiC power semiconductor devices and application of modern power system.Based on analysis of basic structure and working characteristics of SiC BJT and SiC GTO,and comparison of several typical current-driven circuits,design idea of the driving circuit is put forward.I designed a circuit,which composed of capacitors,small power fast silicon BJTs and MOSFETs.Hence,SiC BJT was able to turn on.In order to further shorten the rising time of the drive current when turning on,the drive circuit is improved by increasing the dVGS/dt of gate-source voltage of the MOSFET.The time of the improved drive circuit to generate the drive current from 0 to 200 mA is is reduced doubled.Then,on the basis of the improved driving circuit,another driving circuit which can turn on and turn off SiC BJT is designed by symmetrical complementary structure.The driving circuit is composed of fast optical coupler,MOSFET inverter and Si BJT complementary module.After design of the driving circuit had been completed,circuit with SiC BJT and SiC GTO were added in the experiment.When the drive circuit turns on SiC BJT,the time required to drive the current from 0 to 200 mA is about 20 ns,and the time delay between control signal and SiC BJT working loop is approximately 400 ns,and the time required for the SiC GTO to open is approximately 5μs.When the drive circuit turns off SiC BJT,the time required to drive the current from 200mA to 0 is about 25ns,and the time delay between control signal and SiC BJT working loop is approximately 2.4μs,the time required for the SiC GTO shutdown is approximately 7μs.When the drive circuit makes SiC BJT to turn on and off,the switching frequency as high as 250kHz.The experimental results prove that the driving circuit can realize turning on and turning off processes for SiC BJT and SiC GTO.