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HF step up transformer

Discussion in 'Electronic Design' started by Jamie Morken, May 19, 2008.

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  1. Jamie Morken

    Jamie Morken Guest

    Hi,

    For a step up transformer with an input voltage of 60VDC to 125VDC, and
    a fixed output voltage of 420VDC, at 350watts, what is the most
    efficient transformer type to use? I would like to use a flyback but I
    don't know if I can get to 92%+ efficiency with this.

    cheers,
    Jamie
     
  2. Joerg

    Joerg Guest

    Can't use a simple boost topology?
     
  3. Guest

    Never heard of a step up transformer with a DC input.
     
  4. Joerg

    Joerg Guest

    Just be careful with really small loads at high input voltage. Then the
    PWM behaves more like an idling Harley engine with old spark plugs.
     
  5. PeterD

    PeterD Guest


    Not many DC step up transformers around, so your choices will be
    limited.
     
  6. Naa. Flyback ist only good below 100W.
    Go for a transformer with a 7:1 winding

    Rene
     
  7. Joerg

    Joerg Guest


    But his input is only 125V. If he keeps leakage inductance low and uses
    good snubbers/clamps he should get by with lower voltage FETs. In most
    of my half-bridges the FETs don't see much in terms of spikes.
     
  8. Paul

    Paul Guest

    Your circuit would resemble a standard PC power supply. The
    differences would be that instead of low voltages at the output
    (+5,-5,+12), you would need a 400 volt (or so) secondary. For
    efficiency, you would probably want to run synchronous rectifiers
    (using power FET's). Getting passive shottky rectifiers at this
    voltage would be a pain, anyhow. You would need another winding to
    control the synchronous switching of the FET's.
    As a protoype, you could probably scavenge a few PC power supplies,
    rewind the transformers (make sure that you follow safety standards
    with the 400 volts).
    The little experience I've had with these circuits tells me that
    going for >90% efficiency will require a lot of expertise. I would
    recommend you check out the various engineering rags (EDN,
    Electonics), and application notes from the various semiconductor
    houses. Check out Apr 3, 2008, EDN, p47, "Boost efficiency for lowcost
    flyback converters".

    -Paul
     
  9. neon

    neon

    1,325
    0
    Oct 21, 2006
    he is raving tranformer efficiency at 92% at those kind of wattage.good luck.
     
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