Need help understanding this step-up switching power supply

Discussion in 'General Electronics Chat' started by azone, Nov 17, 2010.

  1. azone

    Thread Starter Member

    Feb 1, 2008
    15
    0
    I am trying to understand this power supply from an old piece of electronics, specifically the step-up based around the transformer. It's a derivation of a flyback converter but I'm having trouble understanding how it works, how it starts up, how the switching is regulated, feedback, etc.. [​IMG]
     
    Last edited: Nov 17, 2010
  2. timrobbins

    Active Member

    Aug 29, 2009
    318
    16
    It's a non-isolated boost, with a feedback winding. Q43 would turn on due to output voltage reaching limit - otherwise W44 is allowed to turn on, but feedback winding would turn it off (v=L di/dt) as inductor saturation of main winding occurs (I reaches limit).

    Ciao, Tim
     
  3. azone

    Thread Starter Member

    Feb 1, 2008
    15
    0
    very nice, thank you very much; was always looking at it as an isolated boost so would get confused with what's going on with the second winding.
     
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