Buck only circuit for amber HD LS?

Could anyone recommend a buck only circuit for an amber HD Luxeon Star? I want to use 3AA's to power it. The simpler the better. I don't really understand if a simple resistor setup is better, maybe someone can fill me in on that as well. I would like to run it at factory specs of 350ma, I have plenty of aluminum mass for heatsinking.

Forward voltage specs for the amber HD (lambertian) are:

min. 2.31
typical 2.95
max. 3.51

Using 2AA's direct drive with no resistance and voltage of 2.87v I get 107ma. Using 2AA's with 2.90 volts I get 167ma. As I understand forward voltage on luxeons, it is sort of the "throttle" of how much current they will take, as my readings above would indicate. EDIT-I do realize that internal resistance of the batteries can affect this.-EDIT.

Thanking you all in advance for any input/help you can give. /ubbthreads/images/graemlins/smile.gif

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NewsFlash said:
Could anyone recommend a buck only circuit for an amber HD Luxeon Star? I want to use 3AA's to power it. The simpler the better. I don't really understand if a simple resistor setup is better, maybe someone can fill me in on that as well. I would like to run it at factory specs of 350ma, I have plenty of aluminum mass for heatsinking.


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Sure can, Mr Al's LM334 based LDO regulator. Just the ticket for this. Will hold a constant 350 mA (or whatever you set it for) until the battery gives up and gets within about .1 Volt of Vf, then reverts to 'direct drive' for what's left of the battery.

As to the simple part, it's not. But, tell you what, how about I send you the gizzie with four wires (two for the Luxeon, two for the battery), you hook it up, try it out and tell us how it works? Can't get much simpler than that......

Send me a PM and we'll sort out the details.

Doug Owen

Doug,
PM sent.