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.
Wrapping up
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.
i need 21volts and 350m amperes output for 6 1W LEDs.
how is that possible to draw 21 volts @ 350mA ?????
Please reply soon.
With Regards
Use a 0-24V transformer and a LM317T basic circuit for limiting output voltage to 21Volts.
hai we r doing a led display with 8*24 matrix so please give me a guidence for driver circuit for that.....its very urgent
Can you please suggest me a super bright LED diagram for my bike head light for 12V supply... ? please
I thnik there is not yet perfect method with us for operating 1 or 3 watts led So why the pwm base driver more brighter and long life
I am planning to make a drive lamp to my motor bike with 5Watt power LED. My input source is 12Volt DC from battery/regulator. Can you help me for making a regulating/controlling circuit for the light assembly.
Thanks
Jinudas
Palakkad
You should use the LM317 circuit for LED driving I've included in the LED driver article.
I've used an LED driver using the LM 317, http://www.reuk.co.uk/LM317-Current-Calculator.htm, i made two circuit one is 32 LEDs and other one is 18 LEDs, my problem is on the 1st time the 32LEDs are bright but now are dim and others are now already busted,the time of usage of 32 LEDs sometimes 24hours a day. the 18LEDs are good and bright and the time of usage is 1 hour maximum. ive seen your circuit the difference is my circuit has no capacitors, i've search it on the net. What do you think the problem? thanks. this is the site http://www.ae5d.com/led-1.html
Better luck next time with capacitors.
Look at LM317 datasheet. Capacitor is required for line stability and control.
thanks, what is the computation or how did you get the 5.3 Ohms resistor? maybe i can get it through test of the output voltage of pin three and ground and use voltage divider principle, but the one i need is the exact formula. I will also try the constant output voltage using LM317 in driving the LEDs just try if it will works and observe the output life of the LEDs.Thanks
For any LED, if the forward voltage is V1 volts and the supply is V2 volts, then the voltage across the resistor is V2-V1 volts. If the LED consumes A1 amperes of current, then by Kirchhoff's law, the same aount of current flows by the resistor. Now, since V=IR, or R=V/I; we get resistor value by (V2-V1)/A1. And the wattage is calculated by W=VI=(V2-V1)xA1.
Example: If a LED consumes 500mA at 3V, then the resistor will be (5-3)/0.5 = 4Ohms. And the wattage of the resistor will be (5-3)x0.5=1Watts.
I would like to build emergency light based on the normal cfl emergency light but use 3*1watt power led instead of 9 watt cfl and the circuit should have least losses (input and output)
pls help in this regard
thank you
What's the battery voltage in the emergency light? If it's 6V, you need a 3Watt LED driver to drive 3x1Watt LEDs in parallel.
you are right the battery is 6 volts 4.5 amp/hr, now it has cfl tube inside it. I want to convert the circuit to led how can i do it changing the present circuit with minimal changes
thankyou
Why don't you take 2 LEDs (pairs) in series and connect to battery directly. This will be the easiest way to do this.
also what is a pulse width modulation?
It's a technique to (digitally) control the power to LEDs(mostly).
hi i am vishwendra i am working to make my own led home lighting i used 7805 circuit but the regulator gets heated and thus the power gets lost.so what can i do for perfectness i am ready to afford the cost but i need a efficient circuit can you help me please
Use a DC-DC converter and set O/P voltage to the needed one. there will be much less heat and power loss.
hi
i have mobile battery (3.7 volt , 900ma)
Can I plug my battery directly to the 1 watt or 3 watt power led ?
please help me
thanks
Yes, you can plus it directly without any possible danger.
can you add the part 240ac to 6dc converter for this circuit (without transformer)
That would be too complex. Use transformer.
if we want 30-40w LED to connect in this ckt that is possible.if that is not possible means plz give solution. thank you
For 30-40W LED, you need a complex circuit.
If you want to discuss with me about making it, then give a shout by the “Wish a Circuit” form and we can discuss it.
Dear Arup,
i want to use 20 leds of high bright with 3.6v & 300ma.
kindly let me know the cct for this
That simply means 20Watts of LED. Connect them in series and give 72Volts which should be the easy way to do it.
I Tried it, But after some time all led's get's dull, Please ,Let me know the Reason,
s.kannan.
Probably LEDs are not of high quality.
Note that if LEDs are heating, you need to add heatsink.