mosfet driver and Vgs problem

Discussion in 'The Projects Forum' started by mah, Mar 23, 2014.

  1. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    i am using Ir2112 to drive mosfet, i measured between Ho and Vs which is (Vgs ) and it was 12 volt but the signal wasn't pure square there were a little Curvature in the up side and low side of the pulse . i don't know if this curvature is normal or i can enhance the circuit performance to get it pure square .I sent you the complete circuit for dc-dc buck converter which is drived by micro controller , i attached the a picture for the wave

    [​IMG] Attached Thumbnails [​IMG]
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    I don't see the circuit.

    How are you measuring this floating voltage? You should do a differential measurement using two scope inputs with two 10:1 probes. Set both channels to the same voltage sensitivity but invert one of the inputs. That should give a good differential measurement.
     
  3. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    sorry i will attach the circuit later
    i measured it by set the input probe on gate and the ground on source
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,570
    2,380
    Are you using on/off control or PWM?
    Max.
     
  5. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    pwm is used
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    That means the oscilloscope ground and chassis is floating at the source voltage. That may be the problem. Try the differential measurement as I suggested.
     
  7. mah

    Thread Starter Active Member

    Mar 15, 2010
    276
    2
    thank you
    I tried this method and it gives good signal but it is 14 volt is that normal ?
     
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