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I have a charger light. It gets charged by 220V AC supply. It can light 5 LEDs. I know that it needs to make the supply 220V AC to DC of lower voltage nearly 5V to 10V. Then it can charge the small battery. But I found no transformer in the circuit. There are simply some diodes resistors and capacitors.

I want to know how the circuit works. I want to know how the small battery can be charged with so high voltage?

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  • \$\begingroup\$ Can't you upload better pictures? They're so much out of focus that you can barely distinguish components. \$\endgroup\$
    – clabacchio
    Oct 15, 2014 at 7:16
  • \$\begingroup\$ Award for making 1600x1200 high-res photos look like 320x200. \$\endgroup\$
    – Rev
    Oct 15, 2014 at 10:22
  • \$\begingroup\$ -1 for the crappy pictures AND using ridiculous resolution in the process. I came across this post in the review queue, so now I'm just going to pile on and vote to close for whatever the handiest reason is. Think about presentation and show a little respect next time. \$\endgroup\$ Oct 15, 2014 at 12:34
  • \$\begingroup\$ I apologize for giving hazy pics. \$\endgroup\$ Oct 15, 2014 at 12:50
  • \$\begingroup\$ Apologizing is pointless since the crappy pictures remain. Fix them instead. And, do it quickly. Only one more close vote to go. \$\endgroup\$ Oct 15, 2014 at 12:55

1 Answer 1

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It uses the large capacitor to "drop" the AC voltage down to a low value that can be rectified and fed (possibly via a resistor for some current limiting) to the battery. It's circuit might be something like this: -

enter image description here

The circuit above is possibly more complex than yours because it provides a semi stable 6.2V dc output (see the zener). I think your circuit will be similar in that there is a capacitor (2.2uF or maybe a slightly different value) that feeds the bridge then, I suspect, the battery will be where the 1000uF is.

The capacitor's impedance at 50/60 Hz will be a few kohms and at the battery's charging current will "lose" most of the AC voltage across it leaving maybe something like 5Vp-p going into the bridge.

The 470kohm resistor may be omitted on your circuit - it's used to discharge the 2.2uF cap when removed from AC - it could give quite a substantial tingle if someone handled the plug and the cap was still charged to a few hundred volts.

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