LED Driver

[almorawaka]

I need to drive 20 serious LEDs using 220V AC power source. please give me a circuit diagram to do this.

 

[Sceadwian]

20 serious LEDS? Do you mean 20 LED's in series? What is the forward voltage of the LED, what is it's forward current, and what is it's maximum reverse voltage?

 

[ronsimpson]

We also need to know what LEDs.
1 watt, 2 watt, 20mA? What total power do you want?

 

[almorawaka]

Each LED need 3.6V to emit full power.A single LED need 20mA. It can't bare more than 5V reverse voltage. If i ware connected all 20 LED's in series they need 72V /20mA.
please give me a better circuit diagram to drive this 20 LEDs using 220V AC power source.

 

[alec_t]

I would suggest a 15Vrms ~3VA transformer, bridge rectifier and fat smoothing cap to give ~ 19V DC supply, then use that to drive 5 strings of 4 LEDs (or 4 strings of 5 LEDs) via a respective dropper resistor for each string.

 

[almorawaka]

View attachment 64466
please look this circuit diagram, this is for a single LED, I need to change C1 & R2 to use 20 LEDs.

 

[Diver300]

You don't need to change C1 or R2 to use 20 LEDs.

The current is controlled by C1, and the voltage and frequency of the supply. Going from 1 to 20 LEDs increases the voltage from 3.6 to 72 V but compared to 220 V either are quite small.

220 nF will give about 15 mA with 220 V and 50 Hz.

R2 is just to discharge C1 once the circuit is unplugged. The value is fairly arbitrary. 1 MΩ will discharge the C1 in less than a second. You could probably use a larger value, but values beyond 1 MΩ may be harder to find.

 

[almorawaka]

Thanks Driver300, If i used use 20 LEDs in serious instead of a single LED, are they light normally..?

 

[Diver300]

Thanks Driver300, If i used use 20 LEDs in serious instead of a single LED, are they light normally..?

You mean " 20 LEDs in series".

Yes, they will light normally.

As that circuit has no isolation, any part could be at voltages that will kill you if you touch it. The suggestion from alec_t is much safer. With a circuit like that, only the primary side of the transformer has any high voltages on it.

 

[almorawaka]

Thanks a lot......