AC to DC converter

Discussion in 'General Electronics Chat' started by ferdowssanehi, Jun 18, 2013.

  1. ferdowssanehi

    Thread Starter New Member

    Jun 18, 2013
    I took my old phone power supplies and opened it up.



    I need help to reverse engineer it because instead of a 5V output, I want a 24V output
    can anyone help me to learn more about this circuit , or sample schematics

    im a second year electrical/computer engineer,
    i dont know why there is a IC chip there , and i dont know about that transformer(yellow component).

    much thanks !
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    They are typically some kind of cheap off line flyback converter using dedicated ASICs made specifically for the application. I wouldn't try to reverse engineer it and I used to design them. I'd go to ebay and buy a cheap 24V cube, probably $5.

    BTW: going from 5V up to 24V would require rewinding the transformer and replacing a lot of components even if it is possible.
    ferdowssanehi likes this.
  3. absf

    Senior Member

    Dec 29, 2010
    If pins 5-8 are all connected together and goes to the primary side of the transformer, there might be a chance that the chip is a Viper22AS, see pdf attached.

    This type of 5V supply normally only gives 500mA like the USB (I guess). So 0.5A x 5V= 2.5W. If you step it up to 25V, then the current would be reduced to 2.5 / 25= 100mA. As bountyhunter has pointed out, you have to rewind the secondary coil and change the values of some of the components. I doubted if it is worth the effort to do all this. But if you just want to experiment with it, then it's OK. :D

    But be really careful... as there is live AC voltages there...

    Last edited: Jun 19, 2013
    ferdowssanehi likes this.
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    You wont be able to do it as the SMPS is designed to give approx 1.8 times the output it needs, so the maximum open circuit voltage would prob be 10V at best.
  5. mrabie007

    New Member

    Aug 28, 2014
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
    As noted, this is a AC line-powered switch-mode power supply. One slip and it can kill you...