### 17cheap Power LED Driver circuit

Driver for power led can cost you several dollars.We decided to design a very simple driver that is very cheap to construct, but can drive your power led well.
 driver schematic diagram
 2N3055 pin and symbol
materials:
DC-power supply  9V-15V DC
Q1-2N3055 or similar NPN transistor
R1-220-ohms 1W
D1,D2-1N4001 or any  silicon diode
R2 @ 1W LED -2.7ohms 1W
R2 @ 3W LED -1.5-ohms 1W
R2 @ 5W LED -0.6-ohms  or 2 x 1.2-ohms/1W in parallel

The circuit employs a simple constant current circuit that limits the current that will flow through the power led. It is very easy to modify if you change the wattage of your led by just replacing the value of R2. You can use also a DC supply of any voltages from 9V to 15V.
For other LED power rating just use the approximate formula:

Current (I) =0.8/R2; where I is the current specified by LED manufacturer. Maximum value of I in this driver is 10A.
Use the formula  R2 = 0.8/Current(I) to determine R2.
This led driver is used in 12V power LED emergency light circuit, of course with some modification.
Other led drivers:
1. driver using 7805 - simple and cheap
2. LED driver using LM317 - simple and cheap
3. High current LED driver using FET - stable and high current capacity.

1. Hi, nice circuit I want to do similar circuit with 3W RED power LED (900mA 3.4-3.8V). And I need more LEDs I think about 8 LED in row (900mA 3.4-3.8V). I'm think about use of BC639 as transistor. What modification I need to do? If I'm calculating same as in this circuit a get R2 0.8 OHM.

2. To Zajca;
You are right, R2 = 0.8 ohms. If you connect 8 LEDs in series, you will need at least 33V DC supply. The problem is BC639 will over heat. Even though it can handle 1A current, its power dissipation is very low. I suggest using TIP31C or TIP41C or 2N3055 transistor. Of course with heat sink
Tell me what DC supply you have and also the parts so I can able to modify a led driver for you.
Or you can use LM317 LED driver, to make it easier.

3. I don't know DC supply now, my friend promised me some varible DC supply next week I'll know. But I've made quick research of my inventory and found few NPN transistors like KU606 KU607 KUY12 could it be used?
Datasheet: http://katalogy.ic.cz/io6/10.jpg

4. Based on the specs of KU606, KU607 KUY12 NPN transistor its ok. KU601,KU602,KU611 and KU612 are also ok provided that we have a good heatsink.

5. Hi,
Good cheap circuit! This is gonna save me a lot of \$\$.

One question though:
I'm using a 12V DC supply, and the voltage across the LED is 11.55V.
I'm using a Vollong 5W High-power LED, and it works, ie the LED emits light. But the Datasheet for this LED says that the continuous forward voltage range for the LED is 6.5Vmin, 7.0Vtyp, and 7.5V max.
Is this driver safe to use with this LED, or do I need to use the output of the driver as the input voltage for a voltage regulator supplying 7V?
Thanks for the circuit!

6. If the voltage needed is 7.5V, the input DC voltage must be atleast 3V higher. Meaning Using 12V as your supply is ok.

Important!
1. Before you test your led, know first the forward current required. It is in the datasheet.
2. Then solve for the value of R2
R2 =(0.8/forward current)
Wattage of R2 = Current* Current*R2
3.Then assemble the circuit

Know the continuous forward current first. The use of led forward voltage (6.5V to 7.5V) is to give you idea that the input voltage must be higher than that (in this circuit atleast 3V higher)
Or link me your LED Datasheet so i can design it for you!
thnx

7. Thank you for you quick reply!

I want to drive 3 of these 5W LEDs with this circuit.

I can't find the manufacturer's datasheet at the moment, but http://www.superbrightleds.com/moreinfo/component-leds/vollong-5w-white-high-power-leds/898/
has specifications.

I have connected 3 of these LEDs in series, and they all emit, but I'm a total noob when it comes to LEDs, and I'm not sure if I'm getting optimum performance from them, or if the transistor or the LEDs are going to cook. What are the dangers?

Thanks for your help!

8. Based on your specs, you need the following modifications:
R1 - 470 ohms rated 2W minimum
R2 - 1 ohm rated 1W minimum
DC input - 25V (min 25VA if using AC to DC converter)

Heatsink is a must here since around 8W of power becomes heat.
I suggest also to try using High current LED driver using FET. Its more efficient and stable.

9. Awesome.

Thanks again.

10. hi,i want to do similar circuit with 350 mA LED and i need more LEDs,i think about 8 LEDs in row(350 mA), and i am think about use of LM2671-5.0IC. sir what modification i need to do? If I'm calculating same as in this circuit a get R2 0.8 OHM.
i am using 12v lead acid battery n tell me sir how to recharge 112v battery give me circuit for this project i waiting for your repply

11. i suggest use high current led driver since its more stable and can handle higher current. But first know the value of LED forward voltage (and current) for this is one of our bases in our design.. For the charger, try to assemble the 12V charger for your lead acid battery

12. nice sharing sir! LED will ultimately be the future form of light source because of its energy efficiency. This can help people save on their electricity bill and lessen their losses.

13. hi,i liked your circuits,but can you give me LED driver circuit diagram for 40LEDs powered by a 12 volts DC supply....please mail me at siddharthkonwar1@sify.com

14. Hi there
I'm trying to make some new headlamps for my son's scooter, and I found this on Dealextreme: http://www.dealextreme.com/p/t6-waterproof-xml-t6-3-mode-1200-lumen-white-led-bike-light-with-battery-pack-set-904482510
I bought two, replaced the original headlamps, but I need a driver that can drive both lamps. My plan was to use the 12V DC from the scooters battery. Can I use your driver for running both lamp in serial? Here is the data sheet: http://www.cree.com/products/pdf/xlampxm-l.pdf

I love the internet =:-)

Lars BĂ¦kmark

15. to Lars,
Assuming you chose 1500mA as your forward current and the expected voltage across each LED is around 3.1V.
You can connect the two LED in series and replace R2 to 0.5 ohms rated 2W (or parallel two pcs of 1 ohm resistor rated 1W each)

The 2n3055 is high power and high current capacity thus you can use it to your LED driver
tnx

16. sir,
i want to use 3watts white leds with 700ma for my bike head lamp from battery voltage is 12v,2.5amps.any modification to do.one more question what is the differece between drivers and power supply.if i have the constant voltage and current in power supply even though i want to use the drivers.then pls say how u get that vaule 0.8 what is it
pls help me thanks in advance

17. hello sir, could you suggest a way of connecting, a 3watt led to a 6 volt 4.5 ah supply...