HOT - LED Lighting...Times Have Changed

[manuellynch]

We have all been told - or you have been told by myself personally in years gone by that you must put a heatsink on an LED and run it cool. Well, coming from the person who has written a few patents pertaining to LED lighting and heatsinks and being involved with a lot of lawsuits for people that were infringing on patents that invented using heatsinks with LEDs.

But - as much as I would like to think I would look good in a leisure suit - maybe bell bottoms - well...times have changed.

In several recent discussions I have had with customers, competitors, and suppliers I think it is not widely known that LED times have changed as well. You use to have to be very careful on how hot an LED ran because you could quickly kill the part. But as with all great technologies things improve. I remember Dane Cardone, the CEO of AoTuroaLED in the USA, telling me that he used to sell mobile phones that fit in a suitcase in the trunk of his car...well I am glad people like Steve Jobs helped us reinvent technology over and over again. Or some of the new BMWs or Mercedes - how long before a tune up or oil change these days.

So - without further delay I have put together a graphic that outlines how White LED efficiencies and operating temperatures have changed over time. This graphic shows that Lumen Per Watt or "Efficacy" has improved dramatically...but at the same time so has the temperature at which LEDs can operate.

So if you have a Nichia or CREE based LED systems in your hand and it is getting hot - you are most likely ok.

The human body runs at 37Celsius and nowadays you can have an LED chip that ran can run at 120-130Celsius... the human being reacts to hot as above 62 Celsius.

Here is a graphic for conversation...times change...but was has not changed is that UL still says that you cannot have a light touching drywall or anything flammable that goes above 90 Celsius...they are being safe!!!

[YYZ]

Just curious where that "62C feels hot" comes from? Some people have trouble with 45C, let alone 60+.

Do you mean "Ouch, that's friggin hot!" or more like "You have to change hands after a while cuz it feels hot", like a cup of coffee?

[manuellynch]

Just curious where that "62C feels hot" comes from? Some people have trouble with 45C, let alone 60+.

Do you mean "Ouch, that's friggin hot!" or more like "You have to change hands after a while cuz it feels hot", like a cup of coffee?

45C is hot??? Come for a weekend in late July to Las Vegas!

Damn Marko - you are now truly a Canadian...its official!!! 62C is "you will pull your hand away hot"

And yes everyone - Marko and I are competitors but we subscribe to the philosophy that there is more to learn from each other. And yes, at Axiom we are friendly with several competitors - hell, my brother and nephew work at one competitor!

Marko - if you are in Las Vegas this week give me a call and we will take you to a Kiwi adventure in Las Vegas - we will freeze your ass off! Lets meet up at the wine event at Nichia LED booth on Thursday night if you are here.

[Erik Sine]

And how much light can we expect to get from an LED at 251 F ? There's enough difference between 70F to 80/85F

[YYZ]

45C is hot??? Come for a weekend in late July to Las Vegas!

Human skin is typically around 34 degrees. 44C is the threshold for causing 2nd and 3rd degree burns as contact time or temperature rises... If you have trouble touching something for more than a few seconds, it's probably around 50 degrees, and 60C would be in the range where you could touch it cause almost instant damage.

Marko - if you are in Las Vegas this week give me a call and we will take you to a Kiwi adventure in Las Vegas - we will freeze your ass off! Lets meet up at the wine event at Nichia LED booth on Thursday night if you are here.

I get in today and stay until Saturday. I've got a lot of things lined up but will be at the Nichia event also. See you there.

And how much light can we expect to get from an LED at 251 F ? There's enough difference between 70F to 80/85F

That's exactly the question to ask. Being able to handle the temperature without failing is one thing, but as junction temp goes up, output goes down.

That Nichia LED Manuel posted info on is currently an exception to the rule, but even an LED system using that LED would perform even better if drive current and temperature are lower, rather than higher - and that's reflected in the results on the GWH and Tightey Whitey tests. Axiom LEDs are really bright, but the efficiency of power to light is just average, due to the higher operating temps. If Axiom was to design for lower operating temps, the efficiency would increase but at some point you'd have to use more LEDs to compensate. The system would cost more, but last longer, but the current arrangement is what Axiom feels is the best compromise between efficiency and system cost, as every LED has that threshold you cross.

It's important to have LEDs that can withstand high temps, especially in lighting products where you have clusters of very hot LEDs in a small fixture with minimal heat sinking, but generally speaking we design systems for 65C max which is WELL below limits of a Nichia or Toyoda based LED. Some stuff we allow to go higher, but anything over 85 will result in reduced output and shorter life. It's up to each manufacturer to determine what life expectancy is acceptable, but basically ANY LED can be made to last a reallllly long time if you sufficiently under-drive and/or keep it very cool, while the opposite is true as temps increase.

Edited May 12, 2010 by YYZ

[Guest Signtiffic]

Damn good insight.... another example of why the syndicate is hands down the number one stop in our industry.

(Isn't technology amazing..... you can get browsing statistics on any website)

[Erik Sine]

Well that's pretty sweet then. Think about some of those regions that may have a short warm season where it could damage a product, but these will bounce back no problem and undamaged

Sent from my iPhone using Tapatalk

[PhillipM]

Human skin is typically around 34 degrees. 44C is the threshold for causing 2nd and 3rd degree burns as contact time or temperature rises... If you have trouble touching something for more than a few seconds, it's probably around 50 degrees, and 60C would be in the range where you could touch it cause almost instant damage.

It is also a matter of how thermally conductive the object is you are touching. One day while the brain was in neutral I shot my infrared temp gun at a piece of steel that was 115ºF (46ºC) and knowing I take neon off the pump at about 125ºF (62ºC) I made a painful mistake and grabbed it. I can assure you I let go quickly!

I remember when the electrical rule of thumb was that you should be able to comfortably hold any component in your hand. Times have changed.

Phillip

[LiteGirl]

Damn good insight.... another example of why the syndicate is hands down the number one stop in our industry.

(Isn't technology amazing..... you can get browsing statistics on any website)

My boss calls this place, The Underground Conduit

[manuellynch]

Surface you mount to and color it is painted make a world of difference

Steel dissipates 60watts/mk

Aluminum dissipates 180watt/mk

Copper dissipates 380 watts/mk

Graphite dissipates 1200 in one direction and 10 in the other

I will respond to Erik and Marko comments in extreme detail tomorrow - discussed with Erik - easier to talk out the science than to write it all down

Marko is right - the Nichia Led we use at Axiom is unusual. The part that Nichia just introduced at Light Fair is even more unusual - 10x brighter and runs almost 20x better in dissipating heat - so light output at higher temps does not change as much

[bigclive]

Although the newer components can run hotter, it's not necessarily a good idea to assume it's OK to run them hot continuously. As with all electronic components the higher temperature WILL shorten their useful lifespan.

[manuellynch]

Although the newer components can run hotter, it's not necessarily a good idea to assume it's OK to run them hot continuously. As with all electronic components the higher temperature WILL shorten their useful lifespan.

You are right - cooler is always better - we have a saying in electronics that there is only one thing in life that operates better the hotter it gets!!! haha