Re: about the thermal resistance of LEDs.
- From: Paul Mathews <opto@xxxxxxxxxxx>
- Date: Mon, 17 Sep 2007 17:04:33 -0700
On Sep 17, 11:31 am, "Raymond Chou" <93246...@xxxxxxxxxxxxx> wrote:
Hi all:
I have a question about thermal resistance of LEDs.
For a single LED, is the thermal resistance a constant value?
Further, is the thermal resistance independent on the driving
current and the junction temperature?
Hope your reply, thanks a lots
For DC drive and most types of mounting, a constant thermal resistance
works well over a broad range of temperatures. If the temperature of
anything rises a lot above ambient, then an increasing proportion of
heat loss is through radiation, and the simple model loses accuracy.
Convection can also become more efficient for higher delta T.
For pulse excitation, the system is better modeled using thermal
resistances and capacitances. Some links:
http://www.ledtemp.com/Thermal%20management.pdf
http://www.ledtemp.com/Calculation.htm
http://literature.agilent.com/litweb/pdf/5091-9704E.pdf
among many such
Paul Mathews
.
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