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From: Victor Roberts
Organization: Roberts Research & Consulting, Inc.
X-Mailer: Mozilla 4.78 [en] (Win98; U)
Subject: Re: luxeon star leds
References: <3DDD9A57.58900EFB@RobertsResearchInc.com> <email@example.com> <3DDDB646.96D0D9D2@RobertsResearchInc.com> <3DDE7264.CD48F4F8@RobertsResearchInc.com> <firstname.lastname@example.org> <3DDEB081.884EC92A@RobertsResearchInc.com> <3DE03D65.932BF9BF@RobertsResearchInc.com> <3DE15871.EF8FF9EA@RobertsResearchInc.com> <3DE224D3.81EFBA3C@RobertsResearchInc.com>
Date: Tue, 26 Nov 2002 22:51:11 GMT
NNTP-Posting-Date: Tue, 26 Nov 2002 14:51:11 PST
Watson 'Atto Parsec' Name wrote:
> In article ,
> email@example.com talked about...
> > Ooops, I missed that. But a luxeon without a heatsink would seem to be a
> > complete waste of an expensive LED. Without a heatsink, it is not possible
> > to push it to anywhere near its intended power level, May as well just use
> > ordinary LEDs.
> The Luxeon has a _built-in_ heatsink. Somewhere I read that it stabilizes
> at 60 deg without any external HS.
I'm not sure I would call the aluminum-core PCB a "heatsink"
since it is designed for connection to a real heatsink, but
it is probably not productive to debate the meaning of
My Luxeon datasheet states that the maximum operating
temperature for the aluminum-core PCB is 105C. There is also
a note on the maximum current specification of 350ma that
"Proper current derating must be observed to maintain
junction temperature below the maximum." I have not
calculated the temperature of the aluminum-core PCB in free
air conditions when it is dissipating 1.1 watts of power,
but this caution from Lumileds leads me to believe that this
device will overheat if operated at full current without use
of an external heatsink.
Even if the maximum junction temperature of 120C is not
exceeded by operating the Luxeon without an external
heatsink, the Luxeon datasheet clearly shows that both the
initial efficacy and the lumen maintenance will be
significantly degraded if the LED junction is operated at
If you have a reference for the statement that the
aluminum-core PCB will stabilize at 60C without an external
heat sink I would be interested finding out where that
information came from.
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