Engineers at NXP Semiconductors say they've found a way to take the "coldness" out of dimmable white light-emitting diode (LED) light.
Using a combination of new technologies that earned the company 15 patents, the company's engineers can reportedly remove the harshness from white LEDs and replace it with the "warmer" combination of yellow and white that's familiar to consumers. Known as "sensorless sensing," the new technology could serve in automotive, architectural, aviation, and industrial LED lighting applications, among others.
"LED lights have always had this cold white -- a hospital white," Radu Sudeanu, senior scientist for NXP, told Design News. "But now we know how to correct it to get the right color."
Using a correction technique, NXP engineers say they can produce a dimmable LED color that lies between amber and white. (Source: NXP Semiconductors)
With its new technology, NXP hopes to make LEDs acceptable to a broader swath of consumers. In the past, some retailers have reportedly received dimmable white LEDs back from unhappy customers, some of whom say the light is too much like that of a fluorescent bulb. "Many people don't like it," Surdeanu told us. "They want the same yellowish light that we've all grown accustomed to for a hundred years with the Edison bulb, and for a thousand years before that with fire."
NXP engineers remove "coldness" from LED light with a three-pronged solution. By combining the black body radiation curve (which relates light wavelength to light intensity) of an incandescent bulb with a logarithmically-based dimming technique, and then correcting for temperature variation, they say they can produce a color that lies between amber and white.
The trickiest and most unique part of the solution is the ability to correct for potential temperature variations, Surdeanu said. The company's scientists accomplished that by measuring the electrical properties -- voltage, in particular -- at the LED's junction. Knowing the voltage, they can predict the temperature of the LED with 1°C in 10 µs. As a result, the system can eliminate potential changes in the wavelength of the emitted light. "Knowing the temperature, we can correct to get the right color," Surdeanu said. "We can do that because we know how LED color shifts with temperature."
Because this "sensorless sensing" technique provides important feedback on the performance of the LED, it is particularly applicable to automotive applications. By "knowing" the temperature at any given time, automotive LED systems can employ the technology, not only for overheating protection, but for aging prediction. As a result, the technique enhances the reliability of LED-based automotive systems. Surdeanu said it will soon be employed by an unnamed automotive OEM.
Surdeanu added that the temperature correction technology can be easily integrated into an LED's driver without the need for additional external components, such as temperature sensors and heat sinks. "When you have those three points -- the black body radiation curve, logarithmic correction, and temperature-effect correction -- that's all you need you to start dimming properly," he said.
This is a great innovation. I personally try to use more energy efficient light bulbs but am one of the people that doesn't like that harsh light--I prefer dim lamp lighting or candles to the "hospital white" mentioned in the article. If I and others like me could have the best of both worlds this would really catch on.
Chuck, this is a good example of an engineered innovation. By putting together these three aspects of the LED lighting they are able to come up with something that consumers actually want. Unlike older lighting technologies, LED lighting is more highly engineered. There are a lot mote parameters that can be controlled.
Elizabeth, I agree - I much prefer the warm yellow light offered by incandescents. I look forward to this technique being offered in the very near future.
This is potential good news for those of us who are sensitive to light color--not everyone is, it turns out. Those greenish CFLs make everyone look like zombies to me, and harsh LEDs give me a headache. But NXP's Surdeanu needs a history lesson: we're used to the warm light of the sun and firelight after a few million--not a thousand--years. And that's what natural spectrum lights are all about--they emphasize the reds we're wired for.
Indeed, Ann, a bit of a history lesson is necessary...I guess I never thought about why many humans are so adverse to harsh light but it certainly makes sense! Not to mention the associations with bright white lighting (hospitals, as mentioned, and to me they also remind me of unpleasant days in a school room!). What is it exactly that makes some of us sensitive to light color and others not so much, do you know?
The history lesson I was referring to was the unit of millions, not a thousand, years: just a few orders of magnitude, that's all! Re what makes some of us more sensitive to colored light than others, I don't know and I'm not sure it's been looked into. There are many variations like that among humans that haven't been studied much. If anyone does know about this one, I'm interested in learning.
Good point, Ann. a similar phenomena can happen with LEDs. NXP told me that if you don't correct for temperature, an LED can give off a pink-ish or blue-ish light.
It's funny, LEDs don't bug me nearly as much. Greenish CFL light makes people look like zombies and I actually find it depressing and/or nauseating. But warm colors are a lot better--that's part of what makes natural spectrum bulbs so efficient in raising mood and lowering blood pressure for some of us.The problem I have with LEDs is they're so harsh--they give me eyestrain pretty quickly.
Yes, for sure, I'd like to know as well. For me, I have been tested to have very light-sensitive eyes in general (I've been a contact lense wearer for 30 years, though I'm not sure that has anything to do with it). I'm not sure if light sensitivity has anything to do with light-spectrum sensitivity in particular, though. Perhaps a Google search is in order! Will report back any pertinent findings...
IT is fine for some folks to prefer the cave-like dim glow, but please don't assume that everybody likes that effect. I have always liked the more frosty white type of light because it allows for seeing things, especially details, much more clearly. The biggest problem that I see right now with LED lighting is the incorrect assumption that everybody likes and must have that yellowish cast light, and that nobody would ever like the frosty white illumination.
But fads come and go and in a while there will be a different shade of light in favor. That is the way things change, and the way that they have been for quite a while.
The other thingthat I see is that for quite a few general illumination applications tere is really no need to make all of the lights exactly the same color spectrum. So there would be a real market for those devices that did not fit into the very narrow bins that seem to be keeping the price of devices higher than they really need to be. How about offering us a line of lights that have a braoder spread of colors, and aloso a lower price. It could be a benefit to a lot of us.
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