Discussion in 'General Electronics Chat' started by taimoorkb, Oct 3, 2007.

  1. taimoorkb

    Thread Starter New Member

    Oct 2, 2007
    how can we convert 220 VAC into 12V dc without using a transformer......i have studied bulk circuitary but is there any other method
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    There may be a way, but the transformer adds safety to the design by isolating you from the line voltage and current. Without some form of galvanic isolation, the idea is potentailly a lethal accident waiting to happen.
  3. cumesoftware

    Senior Member

    Apr 27, 2007
    If you don't use a transformer, one of the output terminals might be "hot" unless you pliug the circuit the right way. You can use a "transformless" PSU (transformless so to speak), which is a power supply that uses a rectifier at the mains, and that DC voltage is pulsed at a higher frequency to supply a high frequency transformer. The advantage of this is that you keep the isolation, but you will use a much smallet transformer.

    Other alternative consists on using an isolation transformer connected to the mains (1:1 ratio), as those are smaller than regular step-down transformers with the same VA rating, and feed the circuit from there.
  4. mrmeval

    Distinguished Member

    Jun 30, 2006
    Well you could convert the AC to light and shine it on a photocell. It does take a few cells but you can get that to 12V pretty easy. Getting the current up is harder.
    *tongue in cheek though it will work*

    If you absolutely HAVE to have that sort of supply:
    Change the zener D7 to get the voltage you want. D6 is a 30V zener, change that to something appropriate for over voltage or remove it and install a fuse.

    BTW the 2nd circuit uses light too! :p