# How does this circuit drop 220vac to 12vdc?

#### supak111

##### ★ƃuᴉɯǝɥɔs sʎɐʍlɐ★
Apr 29, 2012
341
This video/circuit shows a guy dropping 220vac to 12vdc without a transformer, I don't get how this works??

I would think he would get 220vac x 1.414 = 310vdc out

#### bertus

Moderator
Nov 8, 2019
3,035
Hello,

The circuit is called wattless voltage dropper.
The orange capacitor is a like a resistor for AC.
As it is directly coupled to the mains, it is very dangerous.
I would not make the circuit.

Bertus

#### supak111

##### ★ƃuᴉɯǝɥɔs sʎɐʍlɐ★
Apr 29, 2012
341
Thanks for the info . Besides being live 220 ac would the same circuit then work for 110vac to 12vdc or to 5vdc? After reading a bit about it it seems that its a very inefficient power supply type

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,338
As it is directly coupled to the mains, it is very dangerous.
I would not make the circuit.
Definitely not recommended!

This kind of circuit is often used in cheap, sealed electronics. It shall by no means be used if there is any chamce of user access to the circuit (e.g. a connector ...)

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,338
This circuit works for any kind of AC input. It uses the impedance of the capacitor (XC = 1 / (2 × Pi × f × C) to limit the current. Due to the phase difference between voltage across and current through the capacitor the power dissipation is greatly reduced in comparison to a resistor.

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