### 27High current LED driver using FET

This led driver uses a constant current circuit using N-channel power mosfet. What this driver do is it delivers constant current through the LED thus protecting it from damage and at the same time maintaining the output power and output light of the LED. The magnitude of current is controlled  by R2 and the voltage of base-emitter of transistor Q1. In equation form:
Current(in LED) = 0.7/R2  or R2 =0.7/Current; where this current is the operating current of the LED.
 LED driver  schematic
Part List:
R1- 1 kilo-ohms resistor 1/2W
Q1- 2N2222 NPN transistor or similar
Q2- IRF530 power mosfet, or similar
DC- 9V to 15V DC
See values of R2 on every LED current and power rating in resistance table below. R2(actual) is the value used in actual circuit.

 R2 resistance  table
Transistor pinouts:
 IRF530 pinout
 2N2222 pinout
Paralleling Power LEDs
If you are planning to use more than 2 LEDs, lets say about 16 power LEDs. We can modify the circuit by simply adding some resistors in our original driver. The value of R is 0.33 ohms 1/2W to 1W. The value of R2 is dependent on the LED current rating and the same values in resistance table above.
How it is done:
For example you have 16pcs of  1W power leds. The leds will be arranged 8 rows with 2 series led per row. You will need also 8 resistors R and 8 resistors  R2. The value of R2 is 1 ohm @ 1W based on the table above. R2 will be connected in parallel together, same as diagram below.
 LED driver with parallel LEDs
Other LED drivers:
1. LED driver using 7805 regulator –one of the cheapest and simplest driver
2. Simple LED driver using LM317 regulator – simplest using 2 main electronic parts, resistor and IC
3. Cheap Power LED Driver – cheapest, uses only resistor, transistor and diode

1. Hi there,

Sorry to bother again, but I'm having trouble sourcing an equivalent for the IRF530 Mosfet. (I don't have time to order from the web, unfortunately.

Is the STP60NE06L-16:
www.datasheetcatalog.org/datasheet/stmicroelectronics/7039.pdf

appropriate, or am I not even in the ballpark?

Cheers, and thanks again for your help.

2. The STP60NE06L-16 Mosfet is more than enough. Its a good replacement for IRF530.
Don't hesitate on asking any question or posting any comment. Raising your concern can help also other readers.
Thnx!

3. Thanks. Worked well.

4. Can you please explain how to wire Q1 and Q2? I have an idea but want to make sure I'm correct as I'm new to building complex circuits like this.
Also does this circuit produe a lot of heat?

5. Here is the figure on
connecting Q1 and Q2
Heating is normal, just add heatsink. But if you observe excessive heating, the problem might be the incorrect connection of the pins.

6. Hi, i like to power a seoul p7 led:
the dc input is 12V
led current is 2,8A and led voltage is 3,6V
how i can modify your schematic for my application?
thanks.

7. Using the formula R2 = 0.7/2.8 =0.25
Replace R2 with 0.25 ohms minimum 2W rating.
If the value is not available in your place, just parallel 4pcs of 1 ohm resistor rated 1/2W each.
Since the supply is 12v and the LED forward voltage is only 3.6V, excessive heating might happen.
I suggest drop the voltage supply to 6V. Or use 3 of that LED in seies across the 12V supply.

8. Hi there,
THanks for a great write up. If I was to run 10W Cree XML T6 LEDs (3.6V; 3A) R2 would be 0.23ohm.

I want to run approx 10 LEDs though (5s2p) what value would you suggest for R (fig2). Or would you recommend using 3LEDs in series like above with the SSC P7? (3s3p or 3s4p)

Also would STP60NF06L be ok for Q2?

9. sorry - supposed to be 2s5p, not 5s2p

for LED is 10W (3.6V @ 3A) just follow the changes below

3 LED in series:(i recommend)
R – 0.27 ohm 1W
R1 – 1 kilo ohms 1/2W
R2 – 0.23 ohm 1W
Q1 – 2N2222
Q2 – STP60NF06L
DC – 12V DC

2 LED in series:
R – 0.27 ohm 1W
R1 – 1 kilo ohms 1/2W
R2 – 0.23 ohm 1W
Q1 – 2N2222
Q2 – STP60NF06L
DC – 9V DC

If using 12V DC just replace R = 1 ohm 5W

All versions are working but using 2 LED in series is inefficient specially if you are using 12V DC (unless your using 9V as supply)

11. Hi,
I would like to build 4 rows of leds, each row has 3 leds( 1W 0.350mA, 2.8V). So R1 = 1 kilo ohms, R2= 0.7/0.35 = 2 ohms or R2 =0.7 /(0.35 x 4(rows)) = 0.5 ohms? How's about resistor R/ Would 0.27 ohm 1 W is sufficient enough?
ND

R2 - 2 ohms rated 1W (you need 4 of this)
R1 - 1 kilo ohms 1/4W minimum
R - 0.27 ohms 1/4W minimum (you need 4 of this)

13. Thanks so much!

14. Hi i want to make a RGB driver with this circuit so i am building 3 independent drivers ,but how to switch them because i want to switch them from my micro controller, normally i switch with a ULN2803 relay driver by giving 5v to the ULN ic and that in turn will drive a trasister base but here i cant disturb the FET gate right how to do this ? say if somebody want PWM how to do?

TM

15. I have 10 LEDs A1 watt, 3.2-3.4 volt, 3 watt - 350 ma.

What are materials I need and how to build the scheme? And the driver please if I may.

16. Hi there,
thanks again for your input and directions. I have a quick question - I've been looking around and I can't find resistors under 1ohm. Can you recommend a website where I could buy them?

Thanks!

17. If you cant find resistors below 1 ohm, you can parrallel resistors to obtain the the value you need. example paralling two 1-ohm makes 1/2 ohm.
four 1-ohm makes 0.25 ohms
in short
Resulting resistance = Resitance value/ number of resistor to parallel

18. Hi !

i am planing to drive 6 pcs XML T6 LEDs,similar like ADAM, but 6 pcs.

They are rated 10W- 3,35V, 3A (not 3,6V like Adam wrote)
Since i must go 3 in series + paralel to 3 in series combination
what values of resistors must be ?
I am little confused :)

I am making this for automotive application, so input will be from cca. 11-14,5 Volts , gues that this difference in Volts will not be problem ?

I assume that STP60NF06L will be enough?

Thank YOu very much !!!

19. i have this model available RFP50N06 , it says 50 A that will be enought i assume ...

RFP50N06
50A, 60V, 0.022 Ohm, N-Channel Power MOSFETs

20. Hi, would it be possible to control the led brightness by putting a small variable resistor in series with R2? Would I need to do anything to R1 and Q1 if this is a possibility.

I plan on using 3 cree xm-l t6 leds in series with a 12v supply.

Thanks

21. Yes you can , but it is hard to find variable resistor that wattage and value

22. HI, please recommend few replacements for 2n2222 that i can use in place of it.
Also, How to calculate the value of R when paralleling the LED's.
Isn't the same circuit as shown in:
http://www.instructables.com/id/Circuits-for-using-High-Power-LED-s/

By Dan Goldwater

23. HI,please help me guys how to drive an 18watts with 1600lumens 1.8 amperes and an 24watts with 2200lumens 3.5amperes @ 12-14 volts motorcycle power supply. thanks in advance.

24. sorry i am talking about smd leds