Epistar To Introduce AC-LED Products In Second Quarter 2009

March 12, 2009 by Jeff Shepard

Media reports state that Taiwan-based LED chip maker Epistar intends to release AC-LED products in the second quarter of 2009. The company is claiming that it expects to be "the first company in the world to ship AC-LED chips."

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. 1.4mm. Many "one watt class" dc-driven LEDs measure 1mm (40 mil) per side. Epistar says that its AC-LED chip, when driven at 1W, 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; AC-LED is best suited for LED spot lights with less than 10W power, such as MR16 or AR111 replacements. Meanwhile, DC-LEDs are suitable for high-brightness applications such as street lamps or automotive headlights.