Sign & Digital Graphics

April '19

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S I G N & D I G I T A L G R A P H I C S • April 2019 • 59 as the power supply has the highest risk of failure in the system. Increasing run footage reduces power supplies, thus fail- ure points. Technically speaking, most of the performance improvements in LEDs are from a series of breakthroughs in device structure, phosphor technology and crys- tal growth. One of the classic problems with LEDs is inefficiency due to trapped light in these high refractive index semi- conductor materials. Recent advances in light extraction include different die shapes, patterning of the surface and use of mirrors and new optical coatings. The other advance revolves around price and quality. On the quality side, the general illumination market has driven up chip sizes. This has had a benefit to the sign industry, because these larger chips that are being put into mid-power LEDs can handle much higher drive currents. For example, in Principal LEDs Qwik Mod Series, the LEDs are operated at 55 percent of their rated current. This eliminates the need for constant current regulation to ensure that LEDs are not overdriven. On the price side, mid-power LEDs like those used in channel letter modules can be purchased from high-quality man- ufacturers for a few pennies. The LED itself represents as little as 10 percent of Image courtesy of Ellis and Ellis Sign Systems. Image courtesy of Principal LED. Image courtesy of Principal LED.

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