voltage regulator , discrete or lm317

Discussion in 'Power Electronics' started by Niklas Trenneus, Sep 26, 2016.

  1. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    Hi,
    I planning a amplifier build, but my transformer has 2 secondarys,
    but one is giving 83-0-83 ,0,4A and the other 63volt , 6.9A.

    so plan is to find a discrete scematics to build a regulator for best audio.
    but not easy to find...
    need to drop about 13 volts , from 83 to 70v, positive and negative.
    need this to the amplifiers drive stage.
    Any good advice to give me, have tons of mosfet and other components to build with.
    have looked at a regulator with the famous lm317 but i would like to use discrete...
    best regards
    Niklas.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    3,234
    Depending upon the accuracy of the regulation you need, the simplest would be a zener diode shunt regulator driving a MOSFET source-follower.
    What type of regulation accuracy were you looking for?
    For better regulation I would go with a high voltage regulator, such as the TL783, with a booster transistor if needed for higher current.
     
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  3. #12

    Expert

    Nov 30, 2010
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    Audio amps usually don't care much about "dirty" on the power rails.
    (Translation to high tech: Power supply rejection ratio is fairly high for push-pull output stages.)
    What's the problem? 70 volt output transistors?
     
  4. ian field

    Distinguished Member

    Oct 27, 2012
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    The 317 and its negative rail counterpart won't handle such high voltage, and almost certainly won't handle the current for an audio power amplifier.

    Running smoothed unregulated DC to the output stage should give you the best transient response that can be got from that design.

    Integrated regulators may be a valid choice for the signal stages, but you'll have problems with input/output differential unless there's a lower voltage secondary for that end of the amplifier. Some appnotes show how to float the regulator for a higher operating voltage - pretty much the specified application for; http://www.ti.com/lit/ds/symlink/tl783.pdf.

    If you need more current - some appnotes show how to add an external pass transistor.
     
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  5. #12

    Expert

    Nov 30, 2010
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    We have to discover if this is another case of asking for what he wants without knowing what he really needs.
     
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  6. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    It's for the driver stage. i send the link to diyaudio where i did not recieve any help really.

    but its not much current because of its the drive stage, the output transistros has its own feed from the other secondary.
    but looking for a shunt with a mosfet or something,
    do not has to be exactly accurate but a stable voltage is good for the driver stage.
    link to scematic
    http://www.diyaudio.com/forums/powe...-power-supply-regulated-drop.html#post4837199
     
  7. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    never seen this one, looks good, does it work with negative voltage to ?
     
  8. #12

    Expert

    Nov 30, 2010
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    Come on. Help us out here. Without a schematic of the amplifier we are all guessing.

    Next guess: If the driver stage current is low enough, you can just put a 10 volt zener diode in series with the power line to reduce the voltage. But we still can't tell if you need to do that or are you just trying to match a drawing without understanding that an extra 10 volts won't hurt anything? We also don't know how much current the driver stage needs, so we can't tell if a zener diode will be too hot or too wasteful.
     
    Last edited: Sep 26, 2016
  9. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    i put a link to the scematic but here, and thanks, all input is good. :)
    http://www.diyaudio.com/forums/powe...-power-supply-regulated-drop.html#post4837199
     
  10. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The schematic over there can not be shown without a login.
    Can you post the schematic over here?

    Bertus
     
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  11. #12

    Expert

    Nov 30, 2010
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    I found the link in post#1 at diyaudio but I'm not going to join that site just to see the schematic. Post it here.
     
  12. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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  13. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    I in the process to build this Cresendo amplifier, with the modification adviced on the internet.
    But I have 2 dual transformers that give 58-0-58v 0.4a and 44-0-44v at 6.9A, Ac each,
    means 83 v and about 63 v DC.
    I would like as the picture shows, feed the driver stage with 70v and the output stage with 63v.
    so I need to drop about 13 volts on the driver stage.
     
  14. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    i posted it right under :)
     
  15. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    nobody,,, i attached the scematics :) ??

    best regards
    Niklas.
     
  16. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    i might wrote lit wrong, its 83volt DC and want to drop to 70volt about.
    ok.
     
  17. ian field

    Distinguished Member

    Oct 27, 2012
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    Some 317/337 appnotes show how to float the regulator so the input/output differential isn't exceeded - The TL783 is specifically designed to operate that way, but I doubt there's a negative version.

    With that much voltage available; I'd use MOSFET source followers. The gate doesn't draw any current at DC, so the drive circuitry can be really simple.
     
  18. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    any simple samples of that you can share,
    lm317 and mosfet source followers = ?
     
  19. ian field

    Distinguished Member

    Oct 27, 2012
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    Is Google broken again?!!!

    Appnotes are plentiful - and if you can't figure out a source follower, you might as well give up now.
     
  20. Niklas Trenneus

    Thread Starter New Member

    Sep 26, 2016
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    Google never broken, and I will not give up, just sometimes I dont get it right away.
    but thanks. I figure it out eventually.
     
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