Charger light circuit


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?

Best Answer

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: -

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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.