current consuption????/

at the LEDMUSEUM, he has the lights current consumptions listed.... so what I would like to know is if a light has a higher current consumption, will it have more output?

-David

Current consumption and input voltage have to both be taken into account.

Assuming 100% efficiency, a light with a 1.5v power source drawing 1 amp, pushing 3.4v to the LED would be the same brightness as a 3v light drawing 500mA pushing 3.4v to the same LED.

Circuit efficiency is never 100%, and is often FAR lower. The Fenix L1P circuit for example is about 50% efficient, so current consumption can not be directly translated into brightness, even if you know the input voltage.

Thats not even taking the differences between LED's into consideration.....

Incandescents are a whole other story though, since very very few of them have any sort of electronics. So yes, knowing the input voltage and current of an incandescent flashlight, and multiplying them (3v input at 500mA is 1.5 watts) then you can get a pretty decent idea of brightness.

Then there are other thigns to take into consideration, halogen versus krypton versus xenon....

Yeah, effeciency plays as big a role in 'estimated brightness' as current consumption... I think Craig's numbers are very useful when estimating how long the light will last on a set of cells. Lights with voltage boost (most 1 cell lights and most 2 AA cell lights) tend to be quite a bit less effecient than limiting regulators.

cratz2 said:

Yeah, effeciency plays as big a role in 'estimated brightness' as current consumption... I think Craig's numbers are very useful when estimating how long the light will last on a set of cells. Lights with voltage boost (most 1 cell lights and most 2 AA cell lights) tend to be quite a bit less effecient than limiting regulators.

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That depends. Often a limiting regulator is alot less efficient. But one can create a very narrow set of circumstances where a linear drop regulator (limiting regulator) (works like an automatic adjustable resistor) could be more efficient. In the case of the limiting regulator(linear regulator), they need enough cells to create a battery voltage that is higher than the LED Vf, plus the discharged state of the cells is also higher than, or equal to the LED Vf, plus the dropout voltage of the limiting regulator. The excess voltage is just burned up as power (aka heat) in the limiting regulator.

However, if you do have a battery voltage that is higher than the LED Vf, a buck regulator will actually convert the extra voltage into current, and the switching buck regulator will actually pull less current off the cells than the LED uses.

Often times in flashlights, folks compromise switcher designs alot, due to lack of skill, sqeaking out every cent of profit margin they can, using under spec'd components to make the switcher as small as possible, and other similar issues.

It really isn't all that hard to make a switcher that is 95-98% efficient.

NewBie said:

Often times in flashlights, folks compromise switcher designs alot, due to lack of skill, sqeaking out every cent of profit margin they can, using under spec'd components to make the switcher as small as possible, and other similar issues.

It really isn't all that hard to make a switcher that is 95-98% efficient.

Click to expand...

Do any examples of particularly good, or particularly bad, switcher implementations come to mind?