If you're looking for a simple high power LED driver circuit, then it's here.
Driving a high power LED is not that easy. First you've to apply proper voltage to get the maximum possible brightness and you also have to limit the current to avoid LED burn out.
You might have seen other high power LED driver circuits which consists of many parts, like inductors, op-amps, different regulator IC’s , transistor feedback networks even microcontrollers.
Those circuits are more efficient than this one. But the making expense and difficulty is much more high. So I'm showing you the simplest high power LED driver.
Part list and circuit diagram
In market, we can get 1Watt and 3Watt LED easily. 1Watt LEDs have ratings of Forward Voltage 3.2V – 3.6V, and Forward Current 300mA. While the ratings of a 3 watt LED are Forward Voltage: VF 3.4V , Forward Current: 700mA .
So we consider 3.4volts as optimal voltage, and thus the 1 watt LED is running at 3.4×0.3=1.02 watts. For a 3 watt LED it's approximately 2.38 watts.
Finally here’s the simplest high power LED driver circuit diagram.
Here, for a fixed reference supply, LM7805 regulator is used. Which can deliver upto 1Amps of current. In our cases the max required current is 700ma or 0.7Amps, so no problem there. And since the resistor “R” will be eating the extra 1.6 volts(5.0-3.4). So what would be the value of R?
Calculating the value of series resistor R : For the 1 watt model, there’s current of 300mA. So the value of the resistor should be 5.3 Ohms(appx) and wattage should be 0.48. Hence a 5.6Ohms 1/2 watt general purpose resistor will do the job perfectly.
And similarly, for the 3 watt model, the value of R would be 2.2Ohm 1.25 watt, practically you've to choose a 2 watt resistor.
You can feed any voltage greater than 5.5 volts, so we can run this circuit from a 6 volts to 12 volts supply.
As I've said before, this LED driver is not much efficient, you should consider a upgraded driver in your next build, which is more efficient.
There's a good one, DIY LED driver for 5Watt LEDs, and 12V strips from 100-240 VAC .
Have any suggestion or question ? Just drop a comment.