+- voltage from single transformer?

Discussion in 'General Electronics Chat' started by kubeek, Dec 7, 2007.

  1. kubeek

    Thread Starter AAC Fanatic!

    Sep 20, 2005
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    Is it possible to get one high-current full rectified voltage (positive), and at the same time have also some low-current negative voltage, from a transformer with single winding?
    I mean something similar to voltage doublers and things like that.
    Thanks
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    With just one winding, you'll have to have a complete current path; what comes out one lead of the secondary has to go back in the other lead.

    With that said, it IS possible to "split" the output of the supply using a power op amp!

    Go to National Semiconductor's site:
    http://www.national.com
    and download the datasheet for the LM675, a power operational amplifier. On the bottom of page 2, you'll see a schematic entitled "Generating a Split Supply From A Single Supply". The two 22k resistors on the left establish a voltage divider network; in the schematic they're set up to give you an evenly split supply with a "floating" reference ground.

    HOWEVER - if you change the ratio of the two resistors, you'll change where this "floating ground" appears; you could use a smaller value below and larger value on top so that most of the voltage is positive.

    From there, you could build an oscillator circuit powered by the low-voltage high-current negative portion to drive a voltage doubler/tripler/quadrupler circuit, resulting in a high-voltage low-current negative supply, and a high-voltage high-current positive supply.

    Make sense?
     
  3. mrmeval

    Distinguished Member

    Jun 30, 2006
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  4. kubeek

    Thread Starter AAC Fanatic!

    Sep 20, 2005
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    Thank you mrmeval, the charge pump is what I need. Don´t you know any other chips like the max1044, beacause I need to convert +15v to -15. It doesn´t really have to be a chrage pump, some inductive converter may be even better.
    Thanks
     
  5. kubeek

    Thread Starter AAC Fanatic!

    Sep 20, 2005
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    So this is how it will bw done, it is a product of experimenting with voltage doublers and inverters.
     
  6. techroomt

    Senior Member

    May 19, 2004
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    realize that short of any dc to dc conversions, if your two circuits have floating grounds that you can connect one circuit positive with repect to the other source lead, and the other circuit negative with repect to the other lead.
     
  7. kubeek

    Thread Starter AAC Fanatic!

    Sep 20, 2005
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    Yes that´s true, but it doesn´t bring me any closer to powering a single-ended A-class amp from 15v, and at the same time a few opamps from +-15v.
     
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