supplying AMC7135 with 12v

[Andreas]

Hi
My project is to build a led headlight for my car.
I am thinking about using the Cree XT-E leds and maybe run them on 1400mA (around 3,3V) (10x leds)

Though my problem is that I have some AMC7135 current regulators, but they are rated for 6v max.
(Going to connect them in paralell in case someone wonders)
But while running the car battery is around 14.4V

I am thinking about 2 solutions, one is to run 3 AMC7135 in series:

the other one is to use voltage regulator like LM350:

However would it be wise and just drop the AMC7135 and go with any other solution? If so what?
I don't have much experience so I do not know what's best to use, when comparing heat etc.

Thanks in advance!

 

[BobK]

You would be better off with a driver intended to take 12V. A boost driver would allow you to run the LEDs in series. You cannot run them in parallel and expect them to share current equally. In fact, they will not, and the one that takes the most will get hotter, which causes it to take more current (thermal runaway).

Bob

 

[KrisBlueNZ]

I agree with BobK. You should connect them all in series and use a boost converter with output current regulation. This device looks perfect: http://www.linear.com/product/LT3795 because it's very robust, but it comes in a 28-pin TSSOP so you would have to make a PCB for it. You might prefer to buy one on eBay. You need about 33V at 1.4A which is 46.2W. Go for a circuit rated for at least 60W to be safe.

 

[Andreas]

Thanks for your replies Then I will find something else