Transormer that i got from my SMPS

I want to use low voltage ac supply for my projects. I have got one from my computer SMPS. But its winding terminals are making me confuse.At one side,there is 2 terminals(in the picture,it is down side),and the resistance across these terminals is 1 ohm. The other side has 6 terminals,with 3rd and 4th one shorted.(in picture up side). The resistance across all those terminals are also nearly 1 ohm. And lastly,there is a projection from the transformer (shown in picture). I don't know ,what the crap it is.

I want to know the exact input and output terminals.

  • 3
    \$\begingroup\$ That is very unlikely to be a conventional mains transformer. \$\endgroup\$ Commented Mar 24, 2013 at 16:53
  • \$\begingroup\$ Do you have a picture of the circuit you got the transformer from? It will probably be helpful in determining the exact use of the transformer. Also if you really must salvage parts, get a transformer from a linear power supply. I personally wouldn't feel safe using that transformer to get low voltage AC, especially since it isn't marked in any way. \$\endgroup\$
    – AndrejaKo
    Commented Mar 24, 2013 at 17:06
  • 3
    \$\begingroup\$ Transformers used in switched mode PSUs are highly specific to the design of the PSU. You can't just extract it and use it in another circuit, unless it is the exact same design. It certainly won't work in a linear PSU at 50/60 Hz, those are iron core not ferrite which would have been chosen for the switching frequency of 20kHz to typically 500kHz, could be even higher. \$\endgroup\$
    – Martin
    Commented Mar 24, 2013 at 17:31
  • \$\begingroup\$ I didn't have the circuit right now. Since I got this one from SMPS, it might be a step-down.. \$\endgroup\$
    – akhil
    Commented Mar 24, 2013 at 17:35
  • 2
    \$\begingroup\$ At 50/60Hz it will not have enough primary inductance to limit the current through it : it will saturate its ferrite core, as well as overheat. It can only be used in another SMPS. \$\endgroup\$
    – user16324
    Commented Mar 24, 2013 at 19:09

1 Answer 1


This is a high frequency transformer. Two terminals are, Primary and other side (6 terminals) is multi output secondary and possibly a reset winding. Since you took it out from SMPS, It could be Flyback or forward transformer.

Note: You might not be able to use it as conventional transformer. It could be dangerous too (Saturation, Heat)

Other stuff at its top could be low quality shield .

Source: I am power electronics engineer with 6 year experience and I have designed several transformers.


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