27v dc 4A to 12v dc 4A

Discussion in 'The Projects Forum' started by vgpl, May 8, 2013.

  1. vgpl

    Thread Starter New Member

    May 8, 2013
    6
    0
    hello,
    i have a transformer which gives 27v 4A as it's output.
    I want to reduce the output to 12v without the loss of amperes .
    I want to use it as a power supply for an audio amplifier project which use two la4440 ic . So how can i build a circuit to serve my need ,using commonly available parts ?
    Hope you guys can help me with this.
     
    Last edited: May 8, 2013
  2. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,030
    It'd be a lot easier to start with the right transformer.

    It's easy to regulate the voltage at 12V using, for instance, a 7812 voltage regulator, but this would be very inefficient. You would also need a few in parallel, or a high current alternative, to get to 4A.
     
    vgpl likes this.
  3. edwardholmes91

    Member

    Feb 25, 2013
    181
    18
    You wouldn't get a loss on current, you would get a gain in current if you used a second transformer surely?
     
  4. vgpl

    Thread Starter New Member

    May 8, 2013
    6
    0
    can you plz suggest a high current alternative ?
    Or if i use 7812 regulators, how many of them will be needed in parellel to get the desired result ?
    Sorry for being a noob in this.
     
  5. vgpl

    Thread Starter New Member

    May 8, 2013
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    edward i have a step down transformer (27v,4A output). Just want to regulate the output to 12v 4A ,to use with an audio amp project.
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Does your transformer have a center-tap connection?
    Then you can use a full wave 2-rectifier configuration.

    For an audio amp you do not need regulation.
     
  7. vgpl

    Thread Starter New Member

    May 8, 2013
    6
    0
    yes it has centre tap. And you mean i can directly apply the rectified output from a 27v transformer ,to the supply pin of LA4440 IC ???
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    Usually a transformer is rated for voltage across the secondary winding.
    If it is 27VAC then it is likely to be 13.5V from the center tap.
    This will give about 18VDC after rectification.
    The LA4440 is rated to 18VDC max.
     
  9. vgpl

    Thread Starter New Member

    May 8, 2013
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    But unfortunately it is a 27-0-27 transformer.
     
  10. MrChips

    Moderator

    Oct 2, 2009
    12,421
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    Can you get a 12-0-12 transformer instead?
     
  11. vgpl

    Thread Starter New Member

    May 8, 2013
    6
    0
    well that's not the aim of this thread.
    But since experienced guys like you are asking like this, now i think it is better to get a 12v one. :)
     
  12. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
  13. Ramussons

    Active Member

    May 3, 2013
    557
    92
    Can you lay your hands on a surplus PC power supply?

    Ramesh
     
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