dividing rectifier voltage

Discussion in 'General Electronics Chat' started by saturatEd, Nov 28, 2008.

  1. saturatEd

    Thread Starter New Member

    Nov 12, 2008
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    Hi there

    If I use a center-tap type full-wave rectifying method (like with diodes) is there any combination of connecting the rectifiers so that their output voltages add up?
    (to use multiple rectifiers of lower voltage rating for a desired voltage output)

    for example, if I had two center tap transformers, each with one rectifier (pair of diodes), and connected the output of first rectifier to the middle tap of the second transformer, and then for total output used center tap of first transformer vs. output of second rectifier, would that work?
     
    Last edited: Nov 28, 2008
  2. leftyretro

    Active Member

    Nov 25, 2008
    394
    2
    No I don't think that would work at all, but you would have to draw it out to say for absolute sure. However if you already have two transformers you can wire their secondary windings in series (and their primary winding in parallel) and use one bridge diode rectifier and obtain double the voltage.

    Make sense?
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    You mean, using the output of one transformer/rectifier as the "ground" reference for the next transformer/rectifier?

    Yes, you could do that; but if the outputs had different current ratings it might be rather inefficient. You'd also incur double the loss via the Vf of the rectifier diodes.

    Usually, the CT is used as the ground reference, and the rectifiers are connected by the anodes to the ends of the winding; both cathodes are connected together.

    Alternatively, a fullwave bridge rectifier could be used on just the ends of the windings, ignoring the center tap.
     
  4. saturatEd

    Thread Starter New Member

    Nov 12, 2008
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    0
    Yes that's what I meant, using the output of one rectifier (it's both cathodes connected to the center tap of the second transformer) as a ground for the second transformer/rectifier.

    Assuming that the current rating is the same for both of them and that the total output does not load this pair of rectifiers above that current rating

    thanks for the answer
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    That's not the way it's normally done, but I suppose you could do it that way.

    Usually, one would simply wire the secondaries in phase, in series, and either use rectifiers at either end and tie the "new" center tap to ground, or just use a fullwave bridge rectifier across the whole thing.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Don't forget voltage doublers (triplers, quads...).
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Voltage doublers/triplers work fairly well, but each time the voltage is not-quite-doubled, the available current drops by more than half. Diodes are cheap, but they're not ideal. The more current you try to get through them, the higher their Vf, thus the voltage loss.
     
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