Am I correct?

Discussion in 'General Electronics Chat' started by tronicsrookie, Sep 16, 2011.

  1. tronicsrookie

    Thread Starter New Member

    Aug 22, 2011
    My friend has two PCs connected to same UPS. SMPS of one of these broke down while other one is running fine. On opening it, he found the Mosfets are shorted. He asked me as to why did this happen. Had it been a surge etc it should have caused both to die (both of same make).

    I gave him these reasons.

    (1) In any current boost switching circuit, if dead time differs then mosfets will be shorted. This means your SMPS controller IC caused it.
    (2) Could be the thermistor or dried up electrolytic capacitor.

    Am I correct in my reasoning?
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Hmm..U got the technical gene in u.
  3. kubeek


    Sep 20, 2005
    Not necessarily. Not every smps is a half-bridge, and many of them have PFC pre regulator that could fail too.
    The capacitor is more likely, but there could be other reasons like thermal stress if the dead computer had worse cooling than the other, the psu is likely to fail sooner.
  4. tronicsrookie

    Thread Starter New Member

    Aug 22, 2011
    Not really just a newbie.

    Also, yes it could be heat buildup as well, I read that mosfets are temp. sensitive.

    What could be the most probable cause, I just to want to know from the Leets here if I was correct. Btw, my friend just accepted my reasoning, since he knows even less than me :D :D :)