Most efficient Luxeon LED?

[KevinL]

I was thinking a little about the relative efficiencies of Luxeon LEDs and looking for the most efficient LED within their "high powered" star/emitter product family.

The bins I'm calculating for take into what is actually obtainable (with a bit of hard work and money) and not theoretical. Tint is not a consideration for this exercise so I will blank out the middle two with dots. Values in ranges have been averaged (Vf, lumens)

Luxeon 1 R..H : 45.75 lumens, 350mA x 3.15V = 1.1025W. 41.5lm/W

Luxeon III U..J : 100.5 lumens, 700mA x 3.39V = 2.373W. 42.35lm/W

Luxeon III T..H : 77.3 lumens, 700mA x 3.15V = 2.205W. 35.05lm/W

Luxeon V WxxT : 169.85 lumens, 700mA x 6.63V = 4.641W. 36.59lm/W


I understand that there are other more efficient ones, but I'm looking at Luxeons because those are what I'm planning to use in a mod. If I'm not wrong, these numbers mean a U..J is awesomely efficient..

PS: One other thing I realize is that "U" bin vs "T" bin, Q vs R, does not seem like a big deal - UNTIL you do these calculations. Both of them translate into a staggering 10lm/W increase in efficiency. The jump from "S" to "T" is equally astounding. 25lm/W to 32lm/W to 42lm/W.

Looks like I gotta go for R or U bins these days...

 

[NewBie]

For those that don't fully understand all this, lets expound on it further.

This only holds true with the high brightness bin combined with the low Vf bin.

A UxxL wouldn't be great.

100.5 lumens, 700mA x 3.87V = 2.709 W 100.5/2.709= 37.1 lm/W


Remember, you are also using lumen numbers when the die is tested at 25C. Due to die heating, you will easily loose 15-25% of the lumens from the get go. It is worse on a star, due to the increased thermal resistance.


Toss in another 15-30% loss in a cheap boost converter, and the lm/W numbers really head south.


Stack on 7-30% losses for a reflector and lens combo, and things are not looking good at all.


So a nice efficient boost converter, coupled with a nice AR coated UCL, a nice efficient reflector, and a meaty flashlight body with great thermal transfer can go a long way to improving flashlight lumen output, improving runtime, and a reduced primary cell expenditures.

 

[KevinL]

Correct. I'm looking at J bins for the Lux3s and H bins for the Lux1s - kinda drives home how valuable the low-Vf bins are. A T..J Lux3 makes you lose 3 lm/W over a T..H bin. Still, U..L is still preferable to T..J, lottery notwithstanding.

The numbers are taken from LumiLEDs for comparing within their product series, we can assume all will lose some lumens when finally built into the finished light.

 

[BentHeadTX]

Let me check my WX1S Luxeon V

170 lumens at 700mA/6.1V (tested)= 4.27W
39.8 Lumens per watt (I am not complaining)

Here is another thing to do. Check a lumens per watt of power curve and pick the most effecient drive level. I think for the LuxeonIII it is 400 mA. From what I remember, the LuxeonV is most effecient at 500mA.

When they come out with a Y--G LuxeonIII, the WX1S will be replaced.

 

[NewBie]

From what Mr. Krames at LumiLEDs has told me, and also what I've measured, the most efficient point for a Luxeon III is 1-3 mA.

 

[McGizmo]

Newbie,
With all of your test equipment and know how, would you consider taking a Lux III and graphing lumens/ watt against some current levels? Can you do this? I have considered "faking" it by graphing Lux/Watt VS drive current level but I am limited in in test equipment and do not consider myself a good tester! /ubbthreads/images/graemlins/blush.gif

 

[Chop]

I would think that the most efficient and practical luxeon setup would be something in the flavor of an H or J Vf luxeon in the highest flux that you can get running at around 100mA.

 

[GarageBoy]

how does a low vf benefit if you v in is greater than v to led? will a converter solve the need to play the vf matching game? also, will a converter board with a low vf be more efficient?

 

[HarryN]

[ QUOTE ]
GarageBoy said:
how does a low vf benefit if you v in is greater than v to led? will a converter solve the need to play the vf matching game? also, will a converter board with a low vf be more efficient?

[/ QUOTE ]

The converter is able to make current from any excess V, so the lower the Vf, the more efficiently they can supply current to the LED. There are also gains that are not so obvious from the battery pack, as they will usually provide more total amp - hours if the current is drawn more slowly.

As far as which Lux III will be most efficient - In most cases, either a RED or CYAN will be brighter than the white ones. Of course, there is no beating a properly made Red / Orange with a Vf well below 3 V and some serious Lumens / watt, at least if you can keep it cool.

 

[GarageBoy]

that only works with a buck converter, right? what about in the case of a boost?

 

[scudinc]

Usually the converter will either go into direct-drive mode (bad) or just fry itself (worse).