12V @ 120mA Transformerless Power Supply

  • 11147
  • medium
  • Non tested

The circuit provided here is a transformer-less non-isolated power supply which is capable of delivering an output of 12V at 120mA current for an input voltage varying from 85VAC-265VAC. The LNK304 is the heart of this circuit which supports buck boost and flyback topologies. This project is low in cost and simple when compared other tramsformer-less power supplies.


  • Input(V): 85V AC to 265V AC
  • Output(V): 12V DC
  • Output load: 120mA
  • PCB:75mm X 35mm


  1. The above circuit deals with lethal AC voltage levels. Its very dangerous to work with it, without proper experience and precautions!
  2. Extreme caution is advised while experimenting/building this circuit as the output isn’t isolated from mains.
  3. The components are close to what shown in the 3D preview
  4. Use heat sink for components wherever applicable


Parts List

Drill Chart


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I think it should be noted that it not only deals with dangerous voltages by itself, but also the 12V output is not isolated. Anything you connect to this power supply will also have a dangerous voltage level with respect to Earth.

The circuit itself is fine, but many people will think that a 12V output can’t be dangerous.


the BOM is very bad, not readable completely, C5 should be 470uF, L2 capable of 400V, layout to small for R5 (regular 2 watts resistor designs)


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