48vdc to 12vdc

Discussion in 'The Projects Forum' started by anybisi, Mar 7, 2006.

  1. anybisi

    Thread Starter New Member

    Mar 7, 2006
    pls, i need to convert 48 volts DC to 12 or 24 DC,
  2. lildiesel6075


    Mar 7, 2006

    Hey and How are you, what you need to do to convert 48 volts to 12 volts is to get a 12 volt regulater (LM7812), once you get the regulator test it out on a breadboard


    Stick the regulator in the breadboard this way. [​IMG]

    Then connect the positve Lead from your 48 volts power supply to the input put (The outer left pin) then connect the Ground or negative lead from the power supply to your The common pin of the regulator ( middle pin), and the outpin will produce 12 volts and 1 amp. it will be constant.


  3. hgmjr

    Retired Moderator

    Jan 28, 2005
    If you decide to use a 3-terminal regulator to regulate your 48V power source down to 12V, keep in mind that for every watt consumed by your 12V load 3 watts will need to be dissipated by the regulator. That is because there is 36 volts dropped across the regulator and it has the same current flowing through it that the load is drawing. You will need a heatsink to keep the TO-220 package from overheating for load currents greater than 100 milliamps.

  4. Gadget

    Distinguished Member

    Jan 10, 2006
    Some major problems using an LM7812.
    The 1st is that the Maximum specified input voltage is 35 volts for a LM7812, and 40volts for the 7824 (24 volt version) so you would need a Pre-regulator, or some method to drop the input voltage down to a safe value for the regulator to operate at.
    The next is (as hgmjr said) power dissapation. Just getting a modest current flow is gonna turn the regulator and pre-regulator into heaters.
    Related to the above is efficiency. Going from 48 to 12 with a linear regulator means that 75% of your power is being wasted.. (as heat...see above).
    You don't mention what current is required, or what the application is so it is hard to recommend what to use.
    My choice, for most higher current applications (with the exception of powering a sensitive radio reciever) would be Switch Mode regulation, which involves generating a square wave with a mark space ratio of 1 to 3 and lots of filtering (with perhaps some feedback to adjust the mark space ratio for voltage regulation). This would give good efficiency and low heat dissipation and potential for good current ratings (depending on design). The main dissadvantage is the potential for noise on the output.
  5. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    You could try one of National Semiconductor SMPS chips. The cct will be a little more complex but power dissipation is a lot less for the same current output. The NSC site has a great workbench function where you can design it on the web and actually tells you the parts you need to go with it.
  6. Papabravo


    Feb 24, 2006
    Linear Technology has LTSpice/SwitcherCADIII.
    For free you get a general purpose spice simulator.
    That simulator will simulate Switch Mode Power supplies with their chips
    That simulator will give you a cookbook circuit from your specifications, and SIMULATE it to boot.

    Just Google "LTSpice"
  7. thingmaker3

    Retired Moderator

    May 16, 2005
  8. demonkid

    New Member

    Mar 26, 2006
    price is not an issue
  9. thingmaker3

    Retired Moderator

    May 16, 2005
    Demonkid, I apologise for my ambiguity. I was asking what Anybisi's budget was. The link I provided has boost converters which may or may not be within budget for Anybisi.

    Note - if they work well for you, then you are welcome.
  10. karunanithi_pricol


    Mar 13, 2006

    What will be the output current range or max current?

  11. MrChips


    Oct 2, 2009
    Max, where did you dig up this thread? It's eight years old!
  12. MaxHeadRoom


    Jul 18, 2013