LM317 with low volt cut off or simlar

Discussion in 'General Electronics Chat' started by kiwisoundguy, Nov 10, 2010.

  1. kiwisoundguy

    Thread Starter New Member

    Sep 14, 2010
    6
    0
    Hi there,

    I am building a simple DC PSU. 18v DC in 12v DC out. I have been using an LM317 and its been fine. Now I require the output to trun off / cut out if the output or indeed the input voltage drop below 12v. Is there a simple IC or transitor that I can use. My current draw is 200ma max.

    Thanks in advance for your help!
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Shouldn't be too hard to adapt a zener possibly with a transistor into the adjusting leg to set it to minimum should the condition occur, a complete cutoff could also be designed into the 18V coming in line but you'd need a small amount of delay so it would allow the regulator to start up at first.
     
  3. kiwisoundguy

    Thread Starter New Member

    Sep 14, 2010
    6
    0
    Thanks for that. Would you able to suggest said zenner and transistor please?

    Cheers, Ben
     
  4. Artikbot

    Member

    Nov 7, 2010
    45
    1
    I believe any 12.1V Zener will serve the purpose. Since it's just a signal for a comparator, I guess no high power is needed.
     
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