Tiny LED Serve in Automobile

It is reported that a tiny new LED power source could serve in applications ranging from automotive interiors to architectural fixtures to television backlights.

The device, measuring a scant 3.5 x 3.5 x 1.2 mm, could carve out a special niche for itself in hybrid vehicles and electric cars, where packaging is tight and power budgets are tighter, its manufacturer says.

“Due to its small size, you can put just one or two of them in an appliance and there’s still plenty of light,” says Rodney Bailey, vice president of optoelectronic components for TT electronics OPTEK Technology, maker of the new power source. “It’s attractive for electric hybrids because those vehicles need to use the bare minimum of current.”

Known as the OVS5MxBCR4 Series LED package, the new product dissipates a half a Watt of power, but is approximately half the size of other half-Watt power sources. Moreover, its low power-draw means it needs no thermal management, Optek engineers say.

“There’s not enough power coming out of it to merit thermal management,” Bailey says.

Optek is positioning the device in a “sweet spot” between 1W packages – which draw twice as much power and need thermal management – and very small devices that don’t offer sufficient light intensity for many interior applications. The company says the device is already been designed into several forthcoming hybrid electric vehicle programs for interior lighting applications. There, the low power requirements are making it an attractive alternative to incandescent bulbs, which can draw as much as 6A. In contrast, the OVS5MxBCR4 Series LED package uses about one-tenth of that. The use of the device in such applications is consistent with a trend toward growing use of LEDs in the auto industry.

Optek says power dissipation for the device at 150 mA is 0.48W for white, warm white and blue LEDs, 0.51W for a green deice and 0.33W for red, amber and yellow packages. Luminous flux for white, warm white, blue and green LEDs is 25, 25, 6 and 25 lm, respectively.

Applications include automotive interiors and exteriors, architectural indoor and outdoor lighting, mobile appliances and display backlighting, especially in televisions.

As the time goes by, the tiny LED should be popular in applications where they need good light.

Philips Find Ways to Closes Yellow LED Gap

The yellow light-emitting diode (LED) gap always trouble Philips till now. Recently, researchers with Philips Lumileds (San Jose, CA) have developed a monochromatic nitride diode to closes the gap. The phosphor-converted (PC) amber LED demonstrated by Regina Mueller-Mach and her colleagues uses the down-conversion of blue light from an indium-gallium-nitride (InGaN) LED to longer-wavelength light by a phosphor, in a variation of a well-established process for producing cold or warm white light from blue LED light (see also “Fluorescent microspheres create white-light LEDs”).

Monochromatic light-emitting diodes cover a large part of the visible spectrum with high efficiency. For blue light, nitride diodes achieve external quantum efficiencies in excess of 65%. For red light, phosphor diodes achieve efficiencies of approximately 50%. However, so far no highly efficient monochromatic LEDs have been available for the “yellow gap” at around 560 nm.

Leveraging previous research on warm white light, the researchers succeeded in down-converting blue LED light into monochromatic amber light with a 595 nm wavelength and a color purity of 98.7%. The external quantum efficiency of the PC amber LED is at 30-40%, depending on temperature. Compared to direct amber LEDs, the new PC amber LED is two to five times as bright. It achieves a light output of 70 lumens at a 350 mA current.

There are numerous applications for the LUXEON Rebel PC Amber LED. It can be used in yellow traffic lights or signals as well as in cars’ turn signals or warning lights for construction sites. They could also be used in consumer electronics and their high efficiency makes them inexpensive.

Salmon DNA LED Bulbs

It is reported that the latest LED breakthrough comes from the University of Connecticut, and it uses salmon DNA to create very long-lasting white LEDs (though they can be tuned to other colors). By now a lot of cool LED technology still needs to make its way from the lab to the store, it’s exciting to see that engineers are still finding new ways to squeeze more performance out of those semiconductor diodes.

Fluorescent dyes (two different ones, spaced between 2 and 10 nanometers from each other) are added to the DNA molecules, which are then spun into nanofibers. These are very durable because DNA is a particularly strong polymer (it has to be!) (they should last 50 times longer than acrylic, for example).

A LED emitting ultra-violet light is then coated with the DNA nanofibers: “When UV light is shined on the material, one dye absorbs the energy and produces blue light. If the other dye molecule is at the right distance, it will absorb part of that blue-light energy and emit orange light.” Using DNA has the benefit of orienting the dyes “in an optimum way for efficient [fluorescence energy transfer] to occur,” according to David Walt, a chemistry professor at Tufts University.

To tune the light quality, all you need to do is vary the ratios of dye. The light can be tuned from cool white to warm white, for example.

Unfortunately, numbers on how many lumens per watt these LEDs produce haven’t been released yet (though that might just be because they’re still improving them), so it’s not clear if the main benefit from these will be the longer life, or if the extra fine tuning will also mean better light quality than other white LED (like those that use quantum dots, for example), or if energy efficiency will also be superior. But it’s a new trick that will no doubt be useful. Maybe someday we’ll have a bit of DNA in our lights.