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.
I have light-sensitive eyes, too, as well as light spectrum sensitive. I wear dark glasses in sunlight and sometimes on cloudy days, too. Whether there's a connection between those hadn't occurred to me. Interesting question.
The wonderful thing is that we live in a free country and we don't have to be all the same. Of course some stores that I have seen would not give that impresion. Why should I have only one choice, that of "warm white" light? Is nobody brave enough to offere a product other than what marketing has decided is what the masses will be offered?
William K, I agree. I was always curious about the number of customers wanting warm color lighting versus the cool look while developing LED light kits for Hunter Fans. I personally like white light while working in the lab and at my desk. White light makes desktop and wall surfaces brighter for seeing small color bands on resistors and IC part numbers. Here's a video of the NXP demo presented at this years CES conference. http://www.youtube.com/watch?v=bRieORS6g1w&feature=youtu.be
The "you tube" light demonstration was interesting, and it looks like they have done well in emulating an incandescent light bulb. They are half way there. Now all that is needed is a means to control the whiteness of the light independantly of the intensity. Perhaps they never thought about that option.
Of course, by emulating the light bulb they did avoid having to add more wires. I am probably one of the very few who would be quite willing to revise my wiring to support more flexible colors of lighting. Of course, being qualified, willing, and able is a rare thing in this day and age.
Unfortunately, William K. you are only partially correct. This wouldn't even be such an important discussion if we were allowed to choose the lighting type we wanted based on color, preference, costing, efficiency or whatever is most important to the individual. However, the free market was stepped on with others telling us what those priorities should be...and which "better mousetrap" we HAVE to buy.
Jack, it seems that you are correct. I forgot about our legislative body's decisions that were made based on all of those emotions. They seldom let reason and intellect interfere with their process, and so now we are stuch with that pale orange glow lighting.
Forgive me, I was thinking rationally. I hope that the lighting police are not on their way just yet.
It's not just the old-fashioned fluorescent bulbs that have that awful greenish glow but also the CFLs--those were the ones I was referring to. I agree with William K--there should be variety and choice, not only for different people, but for different uses. The cold white light of LEDs is great for seeing fine details.
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