On February 26, 2010, Sharp Corp will release four types of LED light bulbs in Japan. They are two types of E17 small-size bulbs and two types of E26 spherical bulbs and come in two colors (daylight and incandescent colors).

The size of the power supply unit was reduced by using the company's original LED device.

The small-size LED light bulbs

The small-size bulbs are 67mm in length and 35mm in external diameter. The total luminous flux of the daylight color model is 310lm, which is equivalent to that of Sharp's normal LED light bulbs. The company realized the small size and the high brightness at the same time by using its original LED device and scaling down the power supply unit.

This time, Sharp used an LED device made by mounting many LED chips on a substrate and forming distributing terminals on it. The company calls it "Zenigata (coin-shaped) type." It announced the Zenigata-type device, which is as small as 12 x 15mm in size, in December 2009.

The substrate is made with a ceramic material, which prevents age softening better than plastics, Sharp said. It has 40 LED chips. The company said that some of its LED lighting devices are equipped with its in-house LED chips.

Furthermore, Sharp reduced the substrate area of the power supply unit to about half that of its former model (DL-L40AN/AL). Though the company declined to comment on its details, it remodeled the power supply unit to eliminate an electrolytic capacitor. And it is possible to apply this technique to reduce the sizes of existing LED lighting device, the company said.

The daylight color model of the spherical bulb features a total luminous flux of 730lm. The luminance right below the bulb is equivalent to that of a 100W spherical incandescent light bulb. The color temperatures of the daylight color and incandescent color bulbs are 5,000K and 2,850K, respectively. Their designed lifetime is 40,000 hours.