LED Derating

Hello,

I am trying to figure out exactly how hard I can drive my LED's to achieve a decent longevity while having the LED's super bright. I've read that average longevity for an LED is 50,000 hours. How does current and temperature affect the LED's life is essentially what I'm looking for. Clearly the harder you drive the LED and the hotter the environment the less life you get out of the LED. Any one have a rule of thumb or some calculations I could look at?

Thanks

Are you proposing driving a LED above the Absolute Maximum limits specified on the LED maker's data sheet?

Yes. For example in the spec I have it doesn't directly say 20mA is the max current but if you read the spec it in a way implies 20mA as the max. I'm asking what are the implications of driving the LED at it's maximum forward current = 20mA? By doing this is it drastically going to affect operating life? Does it mean that my LED life will go from 50,000 hours to...25,000 or even lower? I attached what I could find on the datasheet.

Ningbo is an unknown Chinese LED manufacturer. They do not guarantee their LEDs like name-brand companies do. The datasheet does not have a maximum CONTINUOUS current rating and lifetime because they probably DO NOT kNOW! They might last one week (the LEDs or the company?).

On proper datasheets, they make very clear that ABSOLUTE MAXIMUM RATINGS are withstanding ratings only.
You can take them to that limit at a specified temperature (usually 25C) and short period of time without damage.

Exceed EITHER the current/voltage value, the temperature, or the exposure time, and then you are on your own.
The behavior becomes non-linear, and any manufacturing imperfection could cause the unit to avalanche without warning.

Heeding a datasheet's values over all worst case scenarios is a sign of good engineering practice.


A good analogy is a typical V8 engine that in a truck may be rated for 300 HP, whereas that same (although higjly modified) engine can put in excess of 2000 HP in a dragster. The difference being that the engine in the dragster is only expected to put that much power for less than 10 seconds, whereas in your truck it must last 100,000 miles.

Yep, and even the 300hp truck engine will only do 100,000 miles if it is putting out 100hp.

I had a bit of a chuckle over the idea of "derating" a LED by running it above its absolute max specs.

Here is a paper with some life estimate curves.

https://www.electro-tech-online.com/custompdfs/2013/03/guSPIE.pdf

Hi Guys

Here is Osram Semiconductors very best right now. There is the E5 and the E3. The E3 is currently the World Leader in 20 mA LEDS.

Pushing 7 to 8 Lumens per little SMD package. And they are 110 Degree too. Had my little ones on test now for Two Months in their actual working environment with raised ambient temps etc. So far these little guys rock

Duris E3 spec here:

And Duris E3 projected lifespan here:

The Chinese have recently introduced exact E3 copies...that cost more and give less light...without Lifespan predictions.

Go Osram. Hard work and honesty is the name of game. You developed this little beauty. Cost you a packet. And yet...you have brought it to Market cheaper than the Chinese can do simply copying it....

Never again a Chinese rip off for me.

Duris E3 does all Osram claims it can do. Still testing....and looking better every Month.

Bright little buggers that love to work. Day in and day out. The Osram Manager I contacted here gave me a little tip about these LED's. I know they are low power...but there is still a wee bit more heat given out at the Anode compared to the Cathode. Important for PCB design though....

Regards,
tvtech

People should stop buying cheap E-Bay Chinese copies that work poorly and fail soon.
The original Western parts cost a little more but they work well and are reliable.

^^^ Wise words regarding a wide array of products...

I'm with A.G. on this one.

One gets what one pays for.

Now, sometimes you get lucky and receive perfectly good components. But that doesn't mean that it will be the norm.