I'm wondering if it is possible to adapt one of the "Roman Black" SMPS voltage regulators to drive a 1Watt Luxeon LED.
The supply voltage is a 6V-4Ah lead acid battery and I need  to drive ONE single LED at 250-300ma (75-80% efficency may be enough). 
This is the link of the Roman Black "current-limited" version:

http://www.romanblack.com/smps/a04.htm

AFAIK, leds don't need constant voltage but constant current.. two months ago I have built an LDO LM334-based constant current regulator for my LED headlamp that's OK for a 3.7V Li-Ion battery supply but don't seems much efficient with input voltage higher than 4.5V, as in this case.


regards
Marco




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