power factor correction SMPS

Discussion in 'Electronics Resources' started by woollison, Sep 12, 2010.

  1. woollison

    Thread Starter New Member

    Sep 12, 2010
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    I wonder if anyone can help an out of date Electronics man?
    I have some Futaba PSUs out of Olympus microscopes to look at and possibly repair. They are based around the FA5331P chip. I cannot fathom out the logic of this device! Looking at the manufacturer's datasheet it seems to drive an Nchannel MOSFET that in it's on state shortcircuits the output from the main bridge rectifier...via an inductor, I know it pulses this MOSFET but I cannot quite see the principle.
    Can anyone with a better understanding please give me a hand? I am getting the circuit drawn as I go but have fallen over at the first stage.

    I believe the chip needs the AC to be on before I would see an output, can anyone give a testing procedure?

    I am aware of the safety requirements and would use a variac on isolation transformer with a DC psu to power the chip. I would be most grateful if you can help.
     
  2. Ghar

    Active Member

    Mar 8, 2010
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    woollison likes this.
  3. woollison

    Thread Starter New Member

    Sep 12, 2010
    2
    0
    Thank you. That is the principle precisely. I think I might be able to understand that. Never been good at the theory but I used to mend PDP11s down to chip level....you could tell when a chip was blown by its smell.

    Jim
     
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