Parasitic capacitance across switch

Discussion in 'General Electronics Chat' started by anhnha, Dec 31, 2015.

  1. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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    Could anybody explain this more?
    Why there is a voltage spike during turn-off period?
    Also how it decrease the crossover loss?

    Parasitic capacitance.PNG
     
  2. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
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    I think when the switch is in off position suddenly there is increase in resistance than of conductor because the medium is air now.
    so, the molecule get energized and leave some spark especially in DC!
     
  3. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    If you don't know the answer now. Do not worry, in chapter 5 you will find more about this crossover losses.
    As for the spike what about parasitic inductance?
     
  4. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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    45
    Thanks but actually I need a more detailed answer.

    Thanks Jony. I am waiting for the chapter!
    For inductance it is easier to understand. Because VL = L di/dt, so when switch changes from OFF to ON (here di is large while dt is small) VL is large.
     
  5. crutschow

    Expert

    Mar 14, 2008
    12,981
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    Any voltage spikes are generated by the stray circuit inductance. This inductance tries to keep the current flowing, generating a spike when this flow is interrupted by the switch.
     
  6. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
    2,831
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