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Problem with variable regulated power supply

Discussion in 'Electronic Basics' started by Animesh Maurya, Jul 22, 2004.

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  1. Hi all,

    I'm having two, 317 variable regulated power supply like this one:
    http://www.uoguelph.ca/~antoon/circ/vps.htm

    I thought the supply will simply act like a battery, you put them is
    series their voltage will sum up, but to my surprise this is not
    happening!

    I expected, 15 and 15 will add up to give 30volts, but when I measured
    the voltage it first appeared 19volts and then gradually decayed to
    2.8volts.

    Now what is wrong with his one?

    Thanks

    Best regards,
    AM
     
  2. burbeck

    burbeck Guest

    hi,
    it is possible to have +15 0 -15 in this way but requires separate
    transformers or sepparate secondary windings, for each half of the
    supply. hope that helps
    regards
    bob
     
  3. You have shown the schematic for only one supply. How did you you
    construct two supplies. Does each contain everything shown on this
    schematic, or did you only duplicate part of it?
     
  4. (Animesh Maurya) wrote in message
    Hi all,

    I'm sorry for replying my own post.

    I forgot something crucial, both the regulators are sharing a same
    transformer, in fact I never bothered about this issue. It was my
    foolish assumption.

    Thanks for your time.

    Best regards,
    AM
     
  5. I hope you have figured out how this keeps the two supplies from being
    independent from each other, so that they cannot be stacked in
    series. Either you need a center tapped secondary, with the center
    tap acting as the common between positive and negative supplies (and a
    positive and negative regulator chip) or you need two isolated
    secondaries (or two transformers) so that there is no internal common
    connection, except the one you make o the output of the supplies.
     
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