led driver hasta 15 A

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.