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Negative Voltage Regulator

Discussion in 'Off Topic [BG]' started by John Davis, Sep 16, 2002.


  1. John Davis

    John Davis Guest

    Mar 27, 2001
    Houston, Texas
    I need some help with this....I've been looking around but have yet to find any schematics for a negative voltage regulator that operates at -13.5v. Me and a friend are powering a graphical LCD, and I'm having a bit of trouble with this bit.

    Can anyone help?
     
  2. multiply 13.5 by -1... there must be some cirquit to do that..
     
  3. Mike N

    Mike N Missing the old TB

    Jan 28, 2001
    New York
    Could you take a regulator out of a car alternator and wire it backwards?
     
  4. lneal

    lneal

    Apr 12, 2002
    Lee County, Alabama
    Strange. How much current? Also, with the LM series voltage regulators, its a no-brainer. Seems like one of those would get close enough to get you by. They jump from -12 to -15 volts in the standard values, but adjustable ones are also available. Go HERE Good luck!
     
  5. John Davis

    John Davis Guest

    Mar 27, 2001
    Houston, Texas
    Thanks, Ineal. I want to build this out of as many discrete parts as possible, to limit down on money spent.

    Here's the "low-down": I'm powering a graphic LCD, which means I can't vary that many volts and still have it working. BTW, It's running at 3 mA.

    I've never had to work with negative voltages before, it's a bit difficult at the moment.
     
  6. lneal

    lneal

    Apr 12, 2002
    Lee County, Alabama
    All the more reason to use the LM regulators. Cheap, reliable as a brick and widely available.
     
  7. John Davis

    John Davis Guest

    Mar 27, 2001
    Houston, Texas
    Ah, all right. I'm checking around the site now.
     
  8. The LM series is by far your best bet. You can get an adjustable regulator and control the output with a pot. Find an ecg manual, you can find the right regulator and it will show you how to connect it with a pot or rheostat to get the desired voltage.
     
  9. I just finished doing Regulated Power Supplies as a module as of yesterday.

    You want it -13.5 volts @ 3 mA?

    give me until tomorrow.

    :D:D

    Merls
     
  10. Ok here's what i came up with. Try it. If it doesnt work, let me know.

    Remember Vdc(in) is from your rectified voltage or batteries etc.
    [​IMG]


    :D:D
    Merls
     
  11. John Davis

    John Davis Guest

    Mar 27, 2001
    Houston, Texas
    Wow, thanks Merls....
     
  12. Please let me know if it doesnt work, i did it from my notes I took in a lecture. But it gives us something to start with.

    :D:D

    Merls
     
  13. Yup, impressive, Merls, you even accounted for the supply current of the 7912 !

    JOhn, You could even do without a negative unregulated supply. Take an ICL7660. It converts a positive voltage to a negative one. Sadly, it only operate up to (down to) 10 volts.