电力电子技术第5版王兆安英文Chapter09章节.pptVIP

Outline 9.1 Gate drive circuit 9.2 Protection of power semiconductor devices 9.3 Series and parallel connections of power semiconductor devices 9.1 Gate drive circuit Basic function of gate drive circuit: Generate gate signals to turn-on or turn-off power semiconductor device according to the commanding signals from the control circuit. Other functions of gate drive circuit: Reduce switching time (including turn-on time and turn-off time) Reduce switching loss (including turn-on loss and turn-off loss) and improve efficiency Improve protection and safety of the converter Gate drive circuits provided by power semiconductor manufacturers and Integrated gate drive chips are more and more widely used. Electrical isolation in the gate drive circuit Gate drive circuit usually provides the electrical isolation between control circuit and power stage. Two ways to provide electrical isolation Optical Optocoupler, fiber optics Transformer Magnetic Thyristor gate current pulse requirments Shape of gate current pulse waveform: Enhanced leading part Magnitude requirement (for the enhanced leading part and the other part) Width requirement (for the enhanced leading part and the whole pulse) Power of the triggering signal must be within the SOA of the gate I-V characteristics Typical thyristor gate triggering circuit Typical gate signal and gate drive circuit for GTO A typical gate drive circuit for IGBT based on an integrated driver chip 9.2 Protection of power semiconductor 　　 devices Protection circuits Overvoltage protection Overcurrent protection Snubber circuits—specific protection circuits that can limit du/dt or di/dt Turn-on snubber Turn-off snubber Causes of overvoltage on power semiconductor devices External reasons Overvoltage caused by operation of mechanic swithes Overvoltage caused by thunder lightening Internal reasons Overvoltage caused by the reverse recovery of diode or thyristor Overvoltage caused by the turning-off of fully-c