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I want to convert 240V AC 50hz to 12V DC without transformer.I want the output (12V) to drive 25 white LEDs.The circuit is giving an output of ~14V DC.But the problem is that it is also giving out ~30V AC.Is it OK to use this for my task or is it harmful (for LED's).What should be done to eliminate the AC component?I even tried using an extra 1N4007 diode at the O/P but no use. Following is the circuit diagram. Circuit diagram

EDIT: My Multimeter shows 0V AC for a 12V 1A power source.So that means my Multimeter is working fine.Is it not?

Roronoa Zoro
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"I want to convert 240V AC 50hz to 12V DC without transformer."

No. You. Don't. Not unless you enjoy getting electrocuted. Regardless what the schematic says, it is not "Mains Isolated". (It's not spike protected worth squat, either, but that's not of immediate concern.)

OK, so you think having 1M resistors is isolation. Problem is, it's not DC you have to worry about, it's AC, and the impedance of your capacitors is ~1600 ohms each. Is your multimeter battery powered? I'd guess not, and your AC reading is partially referenced to the mains - and this should tell you something about the dangers of this circuit.

Plus, although 1600 ohms is quite low enough for you to die, this circuit will only produce a DC current of about 50 mA. I don't know what current limiting resistor you're using on your LEDs, but if you're working at a nominal 10 mA per LED, with the LEDs in strings of 3, you can't count on running more than about 15 LEDs.

And for what it's worth, I've gone to swagatam's website, and the man is a blithering incompetent.

WhatRoughBeast
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  • I want to hang my (5 X 5) LED matrix through ceiling.For that, using a transformer is making the PCB heavy.I want to make the circuit as light as possible.(I could not find PCB transformers anywhere, the ones you can see inside chargers.So I had to use the heavy transformer. Can you suggest me some other way to do it? – Roronoa Zoro Mar 15 '15 at 06:13
  • @RoronoaZoro: Instead of a heavy 50/60 Hz mains transformer, you need to get a lightweight switchmode power supply that's rated for your load. These are readily available from many sources. – Dave Tweed Mar 15 '15 at 11:48
  • Start at the beginning. How much current do you need? You have a 5x5 matrix. Does each LED have a separate drive, or is it multiplexed? And what is the nominal current for each LED? – WhatRoughBeast Mar 15 '15 at 12:50