Re: Possible High LED current with long life time

On Jan 31, 7:44 am, Spehro Pefhany <speffS...@xxxxxxxxxxxxxxxxxxxxxxx>
wrote:
On Wed, 30 Jan 2008 19:39:38 -0800 (PST), the renowned Pubs





<pubud...@xxxxxxxxx> wrote:
On Jan 30, 8:00 pm, Spehro Pefhany <speffS...@xxxxxxxxxxxxxxxxxxxxxxx>
wrote:
On Wed, 30 Jan 2008 11:12:54 -0800 (PST), the renowned Pubs

<pubud...@xxxxxxxxx> wrote:
Hi,

  I have a application where my LED currents are switched as in a
matrix. My current LED on time is 60 us and off time is 15240 us. The
intensity is problem thus I pump a higher current in that 60 us
(applied potential is arround 9V in that period of time ) and that
gives the required intensity. LED doee not heat up since LED current
duty cyle is extreamly small (rms current is  also very small too). Is
this method will reduce the LED life time ?.
Could some one refer some articles on LED life time dependability with
current.

Thank you.

Pubs

Wow. I don't like to go much beyond 8:1 to 10:1. You're doing 250+:1.
I don't think you'll get away with it unless the peak current is not
much more than 5-10x the allowable DC current (meaning the LEDs will
be relatively dim).

Best regards,
Spehro Pefhany
My design works prefectly. IT gives almost like a continoues current
because that current pulse is repeatedly applied. My concerened was
with the life time.

Yes, yes, I know, 'prefectly'.  So what does the LED data *** say
about the conditions you are subjecting it to? For example, here is a
data *** that specifies maximum PEAK current ("Limits of Safe
Operation") at 25°C of 150mA (only 5 x the maximum DC current) for
pulses of < 10 *microseconds*).

http://www.lumex.com/pdf/SSL-LX5063ID.pdf

It should be derated above 25°C, obviously.

Pubudu

Best regards,
Spehro Pefhany
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Thank you very much for your help.
.