I need a constant current of 400-500mA for each color of a 10W rgb LED. Each color consists of 3 1W chip is series. for 3 LEDs in series I'll need about 11 Volts for blue and 8 volts for green.
So far I've successfully used lm317 to create a current source. As I'm going to build several of such drivers I'm looking for a better option. As you know LM317 requires about 3V voltage overhead which is not nice at all (I'll have to use 14V power supply which is not standard, and too much heat is generated).
Is there any other IC with lower voltage overhead?
LM317 is so easy to use and adequately precise for my application, Is there any better option?
After some search I found a few IC's form which I found the following appropriate:
1- onsemi NUD4001 datasheet: http://www.onsemi.com/pub_link/Collateral/NUD4001-D.PDF this one seems very nice but for red color and 12V power supply, the power dissipation of the IC is more than permitted :(
2- onsemi NSM4002MR6 datasheet:http://www.onsemi.com/pub_link/Collateral/NSM4002MR6-D.PDF
I'm not sure about the allowable power dissipation of this IC. This IC is made up of 2 transistors as explaind in How can I efficiently drive an LED? additionally due to dependence of current gain of transistors on temperature how precise do you think these drivers are?
what do you think the best option is?