24v to 12v DC step down converter

Discussion in 'General Electronics Chat' started by Tuffe, Nov 10, 2011.

  1. Tuffe

    Thread Starter New Member

    Mar 9, 2011
    Hello everybody. :)

    I wonder if some of you have a scheme for 24v to 12v DC step down converter who can manage 20 - 30 Ampere?
    I have a Bus who runs with 24v DC, but the stereo broke down beyond repair, so I am hoping to use my current 12v player and power amps, instead of buying new stuff..
    I am a hobby newbie to this, so I am not capable of designing one myself..

    Regards. Tuffe
  2. Adjuster

    Late Member

    Dec 26, 2010
    Really you should buy a commercial unit made to do this job. They are made for the use of people like lorry drivers (truck drivers), who often need to run 12V gear from 24V.

    This is no project for a newbie, and in any case automotive projects cannot be discussed here.
    Tuffe likes this.
  3. Tuffe

    Thread Starter New Member

    Mar 9, 2011
    Okay... There you see how much of a newbie I am :) I did not realize it was that difficult…
    I have etched pcb`s and made several projects from scratch, only having schemes, but I am not skilled enough to make my own drawings.. And yes, I intend to use it inside an auto, but I thought it could be considered kind of a general electronic issue anyhow.
    I did not know that the environment should influent that much..
    What I had in mind, was something like this drawing I have attached, if one skip the rectifier and transformer… But if you say it will not work, I`ll of course accept so :)
  4. SgtWookie


    Jul 17, 2007
    The problem is heat due to power dissipation. With 13.8v out, that's ~28v (when running) so you have 14.2v to drop across the regulator. 20A*14.2V = 284 Watts of power to dissipate; with 30A out, it's 426 Watts. With 6 transistors in the circuit, that's 71 Watts/transistor. That's a LOT of heat to get rid of.

    Switching converters will dissipate very little power by comparison.
    Tuffe likes this.
  5. Tuffe

    Thread Starter New Member

    Mar 9, 2011
    Thank you very much for your answer! It was very clarifying and helps me a lot in my learning process :)
  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Making one is not easy when talking about the huge amount of current.

    You are better off trying ebay for switched mode converters.
    Helps you save a lot of space and heat dissipation, and it will be smaller too.