Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Transformerless 110/220 Volt to 12 Volts 3 amps

Not open for further replies.


Newbie level 3
Oct 10, 2009
Reaction score
Trophy points
Activity points
Hello all,

I am in need of some help. I am in need of a transformerless power supply will allow me to have a universal ac input 110/220 volts and an output of 12 Volts at 3 amps. I had a couple of old monitors around the house that were auto switching. I traced out the ac portion of one of the circuits.

The capacitor is a .33uF not 100nF

:?: I don't really understand the circuit but it works. Now I need a way to reduce the high voltage dc down to 12 volts at 3 amps.

This will be used in a prototype portable, high power, led light source that can be used in developing countries.

Thanks for any help

Not knowing your load characteristics, one can only generalize. Impedance voltage dropping would work if your current draws are consisitant, as voltage regulation would follow flow variation. Angle switching with filter would provide much tighter regulation over variable flow rates. Developing countries shouldn't be deprived of isolation.

you can't get 3 amps from a transformless power supply. period.
it's only for small amps, 50 to 100mA max.


If thats the case explain way you can get a laptop power supply that puts out 19 volts at 3.5 amps. I'm looking at one. A big inductor and a pretty complicated circuit, but no transformer.


sorry but your laptop supply contains a transformer !!!!
you didnt open it seems like ...
there is a high frequancy transformer, a smaller one than in a linear power supply but there is one...

switching power supple (called SMPS) are more efficient than linear supply and so can give more amps in the same volume.

goggle for SMPS ( or here in the forum) and you will get lots of schematics and details about them.

Thanks for the information. I will have to examine some different options.

Any recomendations on developing a 12 V high power led driver? I will need to be able to vary the brightness.

Thanks for the help and pointing me in the right direction.

Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to