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From: email@example.com (Tim Shoppa)
Subject: Re: What is maximum current for LED?
Date: 3 Oct 2002 05:30:01 -0700
NNTP-Posting-Date: 3 Oct 2002 12:30:02 GMT
"R. Lewis" wrote in message news:...
> Is there *any* advantageous effect of pulsing leds with a high current like
> It appears that many 'tronics people believe that there is (or should be)
> some perceived enhancement but never manage to give either a plausible
> reason or an authoritative source for it being so.
> Effective intensity (e.g. as per Blundell-Rey) surely becomes virtually
> constant by the time any discrete 'pulses' become inseparable to perception.
> Could someone with knowledge of such matters please comment.
You want to see HP Application Note 1005, "Operational
Considerations for LED Lamps and Display Devices". It states,
in a section subtitled "DC Operation is Better than
Pulsed Operation for Light Output":
It is always
better to drive an LED device with a high DC current to obtain
the necessary light output to be viewed by a human observer
than to pulse drive the LED. Using a high peak current and a
low duty factor to pulse drive an LED device produces less time
average light output than by using a high DC drive current.
Note that there are some cases where you do not want maximum possible
light out of the LED, but want better efficiency at low light output, where
pulsing gives you an advantage with some older LED's.
There are also some secondary effects that you *may* want, like wavelength
shifts, that you can get by pulsing at high currents.
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