how to get a Negative HV from flyback transformer?

Discussion in 'The Projects Forum' started by electronice123, Jun 23, 2009.

  1. electronice123

    Thread Starter Senior Member

    Oct 10, 2008
    302
    0
    I have been wondering lately:

    How can I get a negative high voltage output from a flyback transformer?

    If I connect the primary in reverse polarity will I get a Negative High Voltage?

    What about the diodes in the flyback secondary, will they prevent the negative voltage?

    (My thinking is, diodes only block current flow so a negative HV could be produced simply by reversing the primaries polarity, without having to remove the diodes, am I right?)
     
  2. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,039
    287

    Howdy:

    If you need negative HV in ADDITION to the positive HV, it's a bit of a trick. If you ONLY need -HV, you can just reverse the polarity of the diode string on the output. (If this is a TV flyback system, you may need to do some simple mechanical tweaks.)

    eric
     
  3. electronice123

    Thread Starter Senior Member

    Oct 10, 2008
    302
    0
    It is a flyback from a TV, with only 1 HV output. I've heard the internal diodes are hard to remove. I'm wondering if it would even be worth trying. I know some of the older flybacks did not have diodes but I have not been able to find any.
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    Probably the flyback transformers of black and white TV's still have seperate diodes.
    A color TV most times use a tripler circuit that is molded.

    Greetings,
    Bertus
     
  5. wojwrobel

    New Member

    Dec 26, 2009
    1
    0
    hello KL7AJ

    can you please explain how to get +HV and -HV simultaneously ?
    i have found this schematic but im not sure about -HV
    have a look
    http://members.misty.com/don/hvinvert.htm

    cheers
    wojwrobel

    after hours of searching i found this
    http://www.play-hookey.com/ac_theory/ps_rectifiers.html

    the funny thing is i cant find it anywhere eals !!!! not even wikipedia....intresting.
     
    Last edited: Dec 26, 2009
  6. Externet

    AAC Fanatic!

    Nov 29, 2005
    758
    57
    Check if the other high voltage winding end that does not go to the rectifier is isolated from other windings.
    If isolated that could be your -HV out if the diode cathode is grounded.
     
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