Taiwan-based LED chip maker Epistar says it expects to be “the first company in the world to ship AC-LED chips in volume,” starting in the second quarter of 2009, according to a report in LEDs magazine.

The company has been developing AC-LED chips since 2004 and has filed more than 10 patent applications in related fields. Last year, the company obtained a patent license from ITRI, the Taiwan-based Industrial Technology Research Institute .

The company 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.

The company 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 10 W power, such as MR16 or AR111 replacements. Meanwhile, says Epistar, DC-LEDs are suitable for high-brightness applications such as street lamps or automotive headlights.