HOW TO STEP DOWN 220Vac to 15Vdc USING BUCK CONVERTER(BATTERY CHARGER)

Discussion in 'The Projects Forum' started by nycokello, Mar 22, 2015.

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  1. nycokello

    Thread Starter Member

    Aug 10, 2009
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    Am designing a battery charger and need some help. these are it's specs:
    -should be non-isolated ,
    -output current -10 A
    -using buck topology
    -capable of stepping down mains AC power to about 15 vdc which is fed to a control loop.

    i know i need to first rectify 220vac to give around 300vdc. this is then fed into the buck.
    now, my first question; can a single buck step down 300v to 15v; or i must use multiple buck converters?
    or is there a site i can find similar circuit diagram???
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You need to use a transformer to step down the voltage to 15V, otherwise your using Thyristor charging with Live mains, highly dangerous.
     
  3. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    As transformerless powersupplies are not allowed here.
    See the ToS for more information.
    I would suggest to use a transformer as Dodgydave also said.
    That way safety is done by isolation of the transformer.

    Bertus
     
  4. nycokello

    Thread Starter Member

    Aug 10, 2009
    12
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    i agree with you all. i understand all dangers poised with non isolated topology ...... but desparate times calls for desparate measures. have been to all major cities in my country, but i cant get ferrite core transformers.
    we still rely on imported electronic goods; but i need a very efficient charger ...not using iron core transformer.
    please, refer me to other websites i may seek assistance.....
     
  5. bertus

    Administrator

    Apr 5, 2008
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  6. nycokello

    Thread Starter Member

    Aug 10, 2009
    12
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    thanks for your replies...
    let me try first before i comment further......
     
  7. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Why not grab an old PC supply and beat it into submission?
    Its cheap (or free even), it's got isolation and it's got plenty of power - just need a small change in the feedback.
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,535
    1,251
    Good point. Search the surplus markets for a 15V, 150 W switching power supply, then put your charger circuit on the output. A big fat stable 15 V source should make the charger much easier to design and control.

    ak
     
  9. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,986
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    one solution could be to modify a laptop charger, they usually give out 18v@ 5amp.
     
  10. nycokello

    Thread Starter Member

    Aug 10, 2009
    12
    0
    First, thanks for your replies. I have confirmed that non-isolated power supplies are obsolete. And they are only used in big power supplies. So am forced to go back to the isolated smps.

    But picking an old pc switcher or 150w power supply may not suffice. To be honest and straight forward, I intend to charge four 12v/70ah lead acid batteries in series. So I need around: 12v by 4 by 10A equals to 600W. So I felt that non isolated smps would be a cheap and simple solution. But , now I have to follow the right procedure.

    And I still have more inquiries concerning isolated smps… first should I start a new thread or I may just continue with this?
     
  11. ScottWang

    Moderator

    Aug 23, 2012
    4,854
    767
    You just start a new thread and this thread will be close.
     
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