Don K, What's Your Take on this Article - Efficiency of LEDs

[Watson A.Name - \"Watt Su]

Don Klipstein, what's your take on the claims of this article that
"white LEDs are inherently more efficient than .."

http://www.micrographia.com/articlz/artmicgr/lmpideal/lmpi0500.htm

Thanks.

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[Don Klipstein]

In article <107s7so2peo8903@corp.supernews.com>, Watson A.Name - \"Watt
Sun, the Dark Remover\" wrote:

Don Klipstein, what's your take on the claims of this article that
"white LEDs are inherently more efficient than .."

http://www.micrographia.com/articlz/artmicgr/lmpideal/lmpi0500.htm

I saw their mention of 50 lumens/watt!

A few weeks ago someone e-mailed me saying that top bin/ranking of
Lumileds white LEDs get 40-plus lumens/watt. I replied a few days ago,
asking for ways to me independently verify that such ranks/binned parts
are actually available as opposed to the rankings existing, as well as for
how I would go about obtaining such parts. No response!

Meanwhile, I want to add that mid-ranked Lumileds parts at full power
(and with chip temperature 25 degrees C, impossible to achieve for long in
a room temperature environment given the thermal resistance from junction
to outer surface of the heatsinking slug of those parts) is about 25
lumens/watt. Nichia has recently added a higher rank to at least one of
their white LEDs, so I think middle ranks of Nichia ones may achieve about
20 lumens/watt, with "T" rank probably typically achieving mid-20's and
maybe upper 20's (I have yet to test Nichia white LEDs of the middle or
top ranks made within the last year).
Expect overall luminous efficacy to somewhat increase, maybe into the
mid-30's lumens per watt, for mid-grade or upper-middle grade Lumileds
parts and top rank Nichia ones at current around 1/4 that which they are
characterized at. Efficiency starts going down again at lower currents
around or a little over 10% of that at which these LEDs are characterized
at, although may exceed "full power efficiency" until the current drops to
a few percent of that at which these parts are characterized at.

But as for 50 lumens/watt: I consider this pie in the sky!!! Just a
couple months ago a major maker was bragging about white laboratory
prototypes with overall luminous efficacy in the 60's! They have a
datasheet indicating that the top rank of their best blue chips are good
for achieving this, but I have yet to hear where I can buy anything half
as good, either white or blue!

- Don Klipstein (don@misty.com, http://www.misty.com/~don/ledx.html)