Cree XR-E Thermal Concerns

[Benjammin22250]

I wish I was as smart as Newbie! I guess thats why I'm going to college.

 

[Kinnza]

I calculated again with the more accurate data you provided, Newbie. I obtain 276,5 lm/w of luminous efficacy. I dont know if the last data correspond to a slighty different spectrum. I used a pic of a XR-E spectrum with a color temp of 6402K, and obtained the 310,7lm/w figure, but getting the data directly from the graph (obviously, less accurate). If i understood well, the new data is from a XR-E with a 6600K color temp, corresponding to 276,5 lm/w, so for this more bluish color, same photopic emission correspond to higher efficiency.

This is a pic showing the luminous efficacy obtained depending of chromaticity coordinates. Mixing it with each tint coordinates can provide the range of luminous efficacy of any tint.

I made a Excel sheet to compute the luminous efficacy. Can anybody suggest me a good file server to put it? Anyway, i can send it for mail to anybody wanting to check the procedure used (or just to get the CIE photopic curve per nm values).

BTW, yesterday i saw this: New LED junction temperature tester.

At the bottom, there is a link to the product page, wich explain the procedure used.

 

[NewBie]

If you poke around on the Aglient site (it may have moved over to Avago's site now), they have a paper on how to measure the internal junction temperature with an electrical setup.
Found it:
http://www.molalla.net/~leeper/ledtherm.pdf

Another method:
http://www.elecdesign.com/Articles/Print.cfm?AD=1&ArticleID=11676

 

[NewBie]

Newbie,
Look forward to see the 3 way test results.
Your hard work on this is appreciated

Below is a section of an XR-E.
What looks like a copper connection between top and bottom in the photo
is just the copper 'smearing'.Second photo is a little clearer.
There is no visible to me connection between the die and the bottom rectangular copper pad.

BTW, I wanted to thank you for sacrificing that LED! Nice