the Taiwan Industrial Technology Research Institute

The figures demonstrate that although sales of notebook PCs slowed dramatically at the end of last year, those models that were fitted with LEDs became increasingly popular. Notebook PCs have typically used cold-cathode fluorescent lamps to backlight the LCD screen. But trends towards lighter, thinner and more energy-efficient models have opened up this application to white LEDs.The report noted with the new LED notebooks released by some of the industry's leading brands, including Acer, Dell and HP, the sharp uptick in adoption will continue throughout this year. Nearly one-quarter of all notebooks shipped in the first three months of 2009 are now expected to include led high bay light. And by the end of this year, more than half of all notebooks shipped will feature the energy-saving technology.

Epistar has been developing AC-LED chips since 2004 and has filed more than 10 patent applications in related fields. In 2008, the company obtained a patent license from the Taiwan Industrial Technology Research Institute (ITRI). The company says it will join a small number of suppliers that have been at the forefront of AC-LED development, notably Lynk Labs, which build AC-driven modules and light engines, and Seoul Semiconductor, which sells power LEDs that can be connected directly to an AC source.Epistar says that it is aware of the lighting industry’s desire for a “two wire solution” i.e. a light engine without complicated electronics. The AC-LED concept simplifies system design by making the AC-DC converter redundant. For a conventional DC-driven LED design, the AC-DC converter introduces a conversion loss typically in the range of 15% to 30%. Any reliability issues with the converter are also eliminated.

Epistar acknowledges that the luminous efficacy of an AC-LED is lower than that of a DC-LED at the same chip size. However, based on the cost saving from eliminating the AC-DC converter, Epistar is working with a larger chip size, currently 55 mil per side, equivalent to approx. 1.4 mm. Many “one watt class” DC-driven LEDs measure 1 mm (40 mil) per side. Epistar says that its AC-LED chip, when driven at 1 W, has an efficacy of up to 70 lm/W at a color temperature of 5700K. This is equivalent to a DC-driven LED with 85 lm/W efficacy and a converter with 15% conversion loss, claims Epistar.Epistar believes that both AC-LED and DC-LED technologies have their own unique characteristics, and each will be suitable for different applications;led high bay light is best suited for LED spot lights with less than 10 W power, such as MR16 or AR111 replacements. Meanwhile, DC-LEDs are suitable for high-brightness applications such as street lamps or automotive headlights.