電力電子技術(shù)Chapter-09課件

1、Outline9.1 Gate drive circuit 9.2 Protection of power semiconductor devices 9.3 Series and parallel connections of power semiconductor devices 9.1 Gate drive circuitBasic function of gate drive circuit: Generate gate signals to turn-on or turn-off power semiconductor device according to the commandi

2、ng 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 efficiencyImprove protection and safety of the converterGate drive circuits provided

3、 by power semiconductormanufacturers and Integrated gate drive chips aremore and more widely used.Electrical isolation in the gate drive circuitGate drive circuit usually provides the electrical isolation between control circuit and power stage. Two ways to provide electrical isolationOpticalOptocou

4、pler, fiber opticsTransformerMagneticSchematic of an optocouplerThyristor gate current pulse requirmentsShape of gate current pulse waveform:Enhanced leading partMagnitude requirement (for the enhanced leading part and the other part)Width requirement (for the enhanced leading part and the whole pul

5、se)Power of the triggering signal must be within the SOA of the gate I-V characteristicsIdeal gate current pulse waveform for thyristorsTypical thyristor gate triggering circuitTypical gate signal and gate drive circuit for GTOA typical gate drive circuit for IGBT based on an integrated driver chipM

6、57962L integrated driver chip9.2 Protection of power semiconductor devicesProtection circuitsOvervoltage protectionOvercurrent protectionSnubber circuitsspecific protection circuits that can limit du/dt or di/dtTurn-on snubberTurn-off snubberCauses of overvoltage on power semiconductor devicesExtern

7、al reasonsOvervoltage caused by operation of mechanic swithesOvervoltage caused by thunder lighteningInternal reasonsOvervoltage caused by the reverse recovery of diode or thyristorOvervoltage caused by the turning-off of fully-controlled devicesMeasures to protect power semiconductor devices from o

8、vervoltageLightening arrestorRC or RCD snubbers (will be discussed later)Zener diode, Metal Oxide Varistor (MOV), Break Over Diode (BOD)Measures to protect power semiconductor devices from overcurrentFuse Circuit breakerProtection with current feedback control in the control circuitProtection with o

9、vercurrent detection in the gate drive circuitthe fastest measureFunctions and classifications of snubbersFunctionsLimiting voltages applied to devices during turn-off transientsLimiting device currents during turn-on transientsLimiting device current rising rate (di/dt) at device turn-onLimiting th

10、e rate of rise (du/dt) of voltages across devices during device turn-offShaping the switching trajectory of the deviceClassificationsAccording to different switching transientsTurn-off snubber (sometimes just called snubber)Turn-on snubber According to the treatment of energy Power dissipating snubb

11、erLossless snubberOperation principle of typical snubbersCircuit configurationSwitching trajectoryOther turn-off snubbers9.3 Series and parallel connections of power semiconductor devicesObjectTo increase the capability to deal with voltage or currentIssues and solutionsSeries connectionIssue: even voltage sharingSolutions: Selection of devices that are closer to each other in the characteristicsVoltage sharing circuitParallel connectionIssue: even current sharingSolutions: Selection of devices that are closer to each other in the char