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How does this circuit drop 220vac to 12vdc?

supak111

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Apr 29, 2012
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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

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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

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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

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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

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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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