Sign & Digital Graphics

The 2015 LED & EMC Report

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14 • June 2015 • L E D & E M C terms of new materials or unique utiliza- tion of existing chips that could impact the future of the sign industry? Quantum Dots Quantum dots is one such radi- cal technology that could create a new breakthrough to the next level of effi- ciency. Quantum dots are ultra-small crystals that have very unique properties. They can be tuned to emit light through- out the visible spectrum. One character- istic of quantum dots is that due to their quantum-confined state they can theo- retically provide more color options and produce a better white. They can be used as a primary lighting source to activate a phosphor or can be excited and emit light directly. Efficiencies in the labora- tory have already exceeded 300 LM/W. AC LED Chips I believe that AC LED chips have a bright future in the sign industry. When you look at a power supply as part of the LED system, the power supply is the weak link and is a hundred times more likely to fail than the LED semiconductor. Any sign installer or service technician knows this by experience. Over 80 percent of reported service calls for LEDs are related to the power supply, hence a chip that operates directly off of AC should create a more reliable LED system. I am not talking about a module that has a bunch of rectification circuitry on the modules—in this case you are just transferring the failure risk. I am talk- ing about a true AC LED chip. Principal LED (disclaimer: I am a partner) recently released Powerline, a COB true AC LED sign module that runs directly off of primary voltage without the need for a power supply. Other LED manufacturers have recently released SMD components that operate on AC directly. Since they are AC they have the advantage of not being polarity dependent (i.e., you can't wire them backward). As these types of AC LED chips are relatively new, they are still expensive, but they offer tremendous maintenance advantages over traditional systems that must incorporate a power supply, and I believe they will find a home in the sign industry in applications where service- ability is at a premium. New Multi-Color Chip Packages One way to create white light is to mix red, blue, and green (RGB) LEDs. However, anyone that has tried to create white light from an RGB system knows that the color rendering index, which is a measure of the quality of white light is low (i.e., it's really hard to create a "true" white). However, researchers at Cree and other LED manufacturers are exploring the use of RGBA (throwing amber in the mix) to create a superior and more efficient light. The U.S. Department of Energy suggests that RGBA LED lamps theoretically can produce a superior CRI and higher efficiencies than the current blue LED + phosphor technology. In addi- tion, the phosphor material can degrade, so just like the former example—remove the pain point from the system. When packaged in the same SMD lamp with separate contact points, LED color temperature (C C T ), which is a measure of how warm or cool the light is could be readily controlled. From an application and end product manufac- turing perspective, this could allow LED product integrators to use one SMD lamp part and then very accurately dial in the color temperature of the white light by simply changing the resistors or utilizing a constant current IC on the board. Keep in mind that LED technology is still a relatively new field and most developments in LEDs (particularly white LEDs) have occurred in the last 20 years. So I anticipate a lot more innovation to come. With billions of dollars being poured into R&D on new chips and new combinations of chips, I am certain that some of these will make their way into the sign industry soon. After all, we were the first industry to really adopt LEDs as part of our craft and I am certain that will continue in the future. SDG Powerline AC LED sign module. (Photo courtesy of Principal LED) Quantum dots can be "tuned" to release photons of different frequencies. (Photo courtesy of Nanoco Industries Ltd.) Example of an RGBA intra- packaged LED lamp. (Photo courtesy of Cree Inc.) LEDs are semiconductor diodes that emit a yellow colored light when a 10V potential is applied to silicon carbide.

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