miller capacitance (igbt)

Discussion in 'General Electronics Chat' started by TAKYMOUNIR, Aug 8, 2012.

  1. TAKYMOUNIR

    Thread Starter Active Member

    Jun 23, 2008
    351
    1
    how can avoid the effect of miller effect in igbt and why we use -ve voltage to turn igbt off
    thanks
     
  2. chrissyp

    Active Member

    Aug 25, 2008
    82
    10
    the gate voltage of the IGBT needs to be purged of residual voltage when turned off, the connection to -ve will do this .It will create a clean/sharp turn off and will also reduce the miller effect by giving a route to ground for the capacitance build up in the semi conductor .
     
    TAKYMOUNIR likes this.
  3. ramancini8

    Member

    Jul 18, 2012
    442
    118
    Miller effect is a collector-base capacitor, and the capacitor value is multiplied by the stage gain. When the transistor is on the capacitor is charged rather rapidly through the low impedance input and collector circuit. When the transistor is turned off the capacitor discharges through the base circuit, and when there is no component pulling the charge out of the capacitor it discharges through the transistor thus causing a slow turn-off and high power dissipation. A negative base voltage speeds up the capacitor discharge causing the transistor to turn off faster. A base-ground resistor helps relieve the problem, but not nearly as much a a negative voltage.
     
  4. TAKYMOUNIR

    Thread Starter Active Member

    Jun 23, 2008
    351
    1
    hi it is possible to draw simple diagram show charging and discharging path in the turn on and turn off(c1,c2) AND I ALSO WHEN THE UPPER IGBT IS ON AND LOWER IS OFF THE LOWER IGBT CAN TURN ON BECUASE THE MILLER CAPACITOR START TO CHARGE AND TURN IT ON AND WHAT IS THE EFFECT IF I INCREASE RG
    THANKS
     
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