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From: "Spehro Pefhany"
Subject: Re: What is maximum current for LED?
User-Agent: tin/pre-1.4-19990216 ("Styrofoam") (UNIX) (Linux/2.2.14 (i586))
Date: Thu, 03 Oct 2002 17:06:21 GMT
NNTP-Posting-Date: Thu, 03 Oct 2002 13:06:21 EDT
The renowned Malcolm Reeves wrote:
> Surely since diode voltage is constant-ish then the loss is
> proportional to I (ish). Power to light conversion is so low you
> could ignore it for heat purposes.
Okay, looking at the first LED manual on my shelf and the graph that's
easiest to read (GaP green), consider a 4:1 current range.
Vf = 2.08V at 10mA
Vf = 2.50V at 40mA
Power dissipation in LED at 10mA is 20.8mW
Power dissipation in LED at 40mA/25% duty cycle is 100mW peak/25mW average
About a 20% increase.
(I suspect newer low end commodity LEDs may be even worse in this regard
as the trend is to use smaller dice to reduce cost).
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