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LED Industry Innovations: 6 Trends to Follow
3/19/2014

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Light-emitting diodes have been around for 50 years, but they have only developed to the point of being suitable for general-purpose lighting in the last 10. The field is undergoing rapid evolution mapped by the LED equivalent of Moore's Law.
 This is Haitz's Law, and it states that in every decade, the cost per lumen (unit of useful light emitted) falls by a factor of 10, and the amount of light generated per LED package increases by a factor of 20 for a given wavelength of light.

If LEDs are to be used as a source for lighting, more is involved than the LED dice themselves. An LED-powered lamp or luminaire (i.e., fixture) requires phosphors, optics, a heat sink for thermal management, and driver electronics, as well as packaging for all of these parts. The worldwide switchover to LED lighting, replacing the woefully inefficient incandescent technology, is driving rapid improvements in all of these areas. Prices for LED lighting products, once astronomical, are falling into the range of feasibility.

Essentially all of the LEDs used in lighting are based on the semiconductor gallium nitride, GaN. This is bonded to a substrate, which in the majority of LEDs today is either sapphire or silicon carbide. Other substrates are under development, as we'll see below.

LEDs are inherently more versatile and potentially far more efficient than any other light source yet devised. An incandescent filament source has a 'luminous efficacy' of around 15 lumens of light for every Watt of electricity input. The rest is wasted as heat. Fluorescents typically run in the range from 45 to 75 lm/W. Metal halide achieves up to 115 lm/W and high-pressure sodium up to 150 lm/W. LEDs can theoretically achieve a maximum of between 260 and 300 lm/W. Current commercial examples run in the high 100s, and the numbers are rising every year.

All LEDs produce heat, but they don't radiate it out the front with the light. They accumulate it at the p-n junction, and the heat has to be removed if an LED is to achieve its designed lifetime. This is accomplished with the aid of a heat sink and a known thermal path to ambient.

LEDs produce light in proportion to the current flowing through them, and most are fed by a DC power supply and a driver circuit that holds the current constant. Early experimentation with driving LEDs directly from AC line current has matured, and AC drivers for LEDs, with their simpler circuitry and lower component count, are claiming a place at the table.

The versatility of LEDs leads to explorations of what they can do for us besides producing white light. Our understanding of the effects of light on humans (and other living things) is increasing rapidly. LED lighting is being asked to contribute to human health, well-being, alertness, attention, the food supply, and more.

Light-emitting diodes have been around for 50 years, but they have only developed to the point of being suitable for general-purpose lighting in the last 10. The field is undergoing rapid evolution mapped by the LED equivalent of Moore's Law.

This is Haitz's Law, and it states that in every decade, the cost per lumen (unit of useful light emitted) falls by a factor of 10, and the amount of light generated per LED package increases by a factor of 20 for a given wavelength of light.

If LEDs are to be used as a source for lighting, more is involved than the LED dice themselves. An LED-powered lamp or luminaire (i.e., fixture) requires phosphors, optics, a heat sink for thermal management, and driver electronics, as well as packaging for all of these parts. The worldwide switchover to LED lighting, replacing the woefully inefficient incandescent technology, is driving rapid improvements in all of these areas. Prices for LED lighting products, once astronomical, are falling into the range of feasibility.

Essentially all of the LEDs used in lighting are based on the semiconductor gallium nitride, GaN. This is bonded to a substrate, which in the majority of LEDs today is either sapphire or silicon carbide. Other substrates are under development, as we'll see below.

LEDs are inherently more versatile and potentially far more efficient than any other light source yet devised. An incandescent filament source has a "luminous efficacy" of around 15 lumens of light for every Watt of electricity input. The rest is wasted as heat. Fluorescents typically run in the range from 45 to 75 lm/W. Metal halide achieves up to 115 lm/W and high-pressure sodium up to 150 lm/W. LEDs can theoretically achieve a maximum of between 260 and 300 lm/W. Current commercial examples run in the high 100s, and the numbers are rising every year.

All LEDs produce heat, but they don't radiate it out the front with the light. They accumulate it at the p-n junction, and the heat has to be removed if an LED is to achieve its designed lifetime. This is accomplished with the aid of a heat sink and a known thermal path to ambient.

LEDs produce light in proportion to the current flowing through them, and most are fed by a DC power supply and a driver circuit that holds the current constant. Early experimentation with driving LEDs directly from AC line current has matured, and AC drivers for LEDs, with their simpler circuitry and lower component count, are claiming a place at the table.

The versatility of LEDs leads to explorations of what they can do for us besides producing white light. Our understanding of the effects of light on humans (and other living things) is increasing rapidly. LED lighting is being asked to contribute to human health, well-being, alertness, attention, the food supply, and more.

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Bert22306
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Government mandates also help lower the price
Bert22306   3/19/2014 4:04:46 PM
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In spite of the strenuous objections from those with libertarian leaning, I was looking forward to the gradual ban on higher powered incandescents. Reason being, this spurs innovation and also guarantees economies of scale. And that in turn would end era of the transitional CFLs sooner rather than later. Browsing though the light bulb shelves at Lowes and Home Depot has become fun again. All good.

I think one very important ingredient in LED development will be to make that power supply circuit as sparse as possible. And it's gratifying to see this happening.

Caleb Kraft
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HCL
Caleb Kraft   3/19/2014 4:27:15 PM
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Is human centric lighting really an advancement in the LED industry? I mean, doesn't most of it apply to incandescents and flourescents as well?

kadawson
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Re: HCL
kadawson   3/19/2014 5:42:29 PM
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True enough, but HCL comes into its own in the LED era. Incandescents and fluorescents can't behave as flexibly as LEDs with respect to control of color (and spectrum). Also, the inherently directional light of LED sources is easier to direct precisely where it's needed, to the benefit of humans, other creatures, and dark skies.

kadawson
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Re: Government mandates also help lower the price
kadawson   3/19/2014 5:44:33 PM
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Agreed, we're going to see increasing focus on the driver side of LED lighting. When luminaires are tested to destruction, often it is the driver that fails first. While we know how to predict the useful lifetime of an LED, the same is not (yet) true of a driver.

LarryM99
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CEO
When does it diverge?
LarryM99   3/19/2014 7:10:00 PM
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The first LED lighting for general consumer use was strictly replacement, built to screw into light sockets. I am starting to see more imaginative use of what is a fundamentally different light source, but it seems like there is room to really diverge. Can we build them into walls, maybe with electronic steering of the beams? Can we paint them onto surfaces and have them change colors as our moods dictate? What else might we want to do with them?

Duane Benson
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Re: When does it diverge?
Duane Benson   3/19/2014 7:32:10 PM
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Larry - I think you've hit on the really revolutionary potential. A big part of the need for the Edison base was simply the frequency that bulbs needed to be replaced. When significantly greater life span is reliably avaialble, the game changes. They can be put in essentially innacessible places and can be used in ways that incendescents never could.

prabhakar_deosthali
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CEO
Supply frequency
prabhakar_deosthali   3/20/2014 3:53:02 AM
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With LEDs working on their own driver circuits at some DC voltage levels, with many of the modern appliances working on inverters that convert AC to DC and aganin back to AC at a desired frequency , I think it is now time to relax those Frequency norms on the grid elelctric supply ( 50 or 60 hz +- 2% ).

 

Does it really now matter at what frequency the grid electricty is supplied? May be I am missing something!

GeniusEE
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Freelancer
Re: Supply frequency
GeniusEE   3/20/2014 6:27:22 AM
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prabhakar_deosthali   3/20/2014 3:53:02 AM: "Does it really now matter at what frequency the grid electricty is supplied? May be I am missing something!"

----------

 

You might want to revisit your freshman year AC Machines class notes

Bob Marso
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LED's and Color
Bob Marso   3/20/2014 1:13:08 PM
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One performance specification that held back CFL's acceptance was their poor ability to correctly illunimate the full spectrum of color in our houses.  Our spouses fought CFL's in the living room because they made the living room look like it had jaundice or some liver disease.  LED's are capable of overcoming this - after all the most accurate color rendering of computer images is obtained on LED backlite displays, not florescent backlite displays.

Knowing the color temperature of a light source (measured in degrees Kelvin) is not sufficient to select a good light bulb. The measurement of how wide a color spectrum a light source can accurately display or illuminate is the Color Rendering Index, or, CRI.  The closer to 100 you get, the better the light source.  CRI's in the low 90's are considered the minimum for good color illumination.  I'd like to see all manufacturers of interior lighting sources, no matter what kind, required to specify the color temperature and CRI on their packaging.  This would allow we the consumers to select the best light source and also up the competition among manufacturers to produce a better product.

BitHead77
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Silicon substrate
BitHead77   3/20/2014 6:47:23 PM
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Wouldn't the use of a silicon substrate also allow some of the drive electronics to be built along side the LED(s) that is(are) being driven?  Could this be used to reduce cost as well?

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