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Voltage regulator

  1. Aug 18, 2008 #1
    hey guys, ive got to make a voltage regulator for a uni project. it has to use hysterisis and produce 9v out from a 16Vrms AC powerpack over a 15 ohm load. It also needs overload protection, ive drawn up the attached circuit, i think it will work and filled in some of the values i know but im stuck for the others, any help would be great.

    circuit.JPG
     
  2. jcsd
  3. Aug 20, 2008 #2

    Redbelly98

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    I'm not qualified to analyze a circuit like that, but what about using a simple 9Vdc regulator after cap C6?
     
  4. Aug 20, 2008 #3

    mgb_phys

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    I think that's cheating!
     
  5. Aug 20, 2008 #4

    berkeman

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    Couple comments:

    -- Usually I would put the current sensing resistor in the + feed, right before Q1. Having it in the negative return complicates the grounding of this non-isolated buck converter.

    -- I'm not sure about the snubber on the flywheel diode. I've never used one, and generally haven't seen them used in bucks. It will lower your efficiency at least. Why do you have it there?

    -- It seems like you should consider putting a bit of hysteresis in your comparator circuit. I'm not generally comfortable with comparator circuits without at least some postitive feedback hysteresis.
     
  6. Aug 20, 2008 #5

    berkeman

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    I get the feeling that the assignment is to design a switching regulator, rather than a linear regulator.
     
  7. Aug 20, 2008 #6

    berkeman

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    -- Also, is there a reason that you are using a Darlington for Q1? That will impact your efficiency pretty significantly.


    Quiz Question: Why?

    .
     
  8. Aug 20, 2008 #7

    Redbelly98

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    Whoops, my bad!
     
  9. Aug 20, 2008 #8

    berkeman

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    Another Quiz Question for the original poster (OP) -- Why do I say this about comparator hysteresis?
     
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