LED 200 Lumens. Voltage Dependant?

I'm buy a CREE P4 bulb to replace the bulb in my Surefire 6P. They say the voltage of this CREE P4 is between 3.x and 9volts.
Q. Is the lumens of the bulb more with a higher voltage, or is there a regulator in the bulb that will keep it the same lumens no matter the voltage? In other words, will I do better putting this bulb in my 6P or my 9P Surefire.
Q. What really is the lumens of the CREE P4? Something tells me it's not really 200 lumens. :laughing:


Thanks for your help. :wave:
Dave

The normal voltage drop for a CREE P4 is somewhere between 3.3 and 4.0 V, and most of them land on about 3.7 V when driven to specifications.

If we are talking about forward voltage drop, Vf, then no, you won't gain more light by finding a LED with a higher Vf.

If we are talking about drive voltage, then yes, if you crank it up, say from 3.7 V and 750 mA to 3.9 V and 2000 mA, then it will be brighter.
However, you just about never voltage-drive a LED, as it is highly nonlinear and it can easily break them.

There are two ways to drive the LED in particular, either with a regulator like you say, which will drive the LED to a constant current, or with a series resistor. A constant current will produce more or less the same amount of light all the time, but it will not regulate to constant light (that would be neat, but difficult do implement), only to constant current. Therefor, as temperature goes up in the LED, the amount of light will decrease.
The resistor version will decrease the output as the batteries discharge.


You can squeeze out 200 lumen from a CREE P4. A U-binned P4 at 2000 mA pumps out 240 lumen.