Replaceable Arc Tube Makes Lamp Greener

Jul 3, 2008
Masaru Yoshida, Nikkei Electronics
Hitachi Lighting's bulb-shaped fluorescent lamp with replaceable arc tube unit (joint development with Seiyu)
Hitachi Lighting's bulb-shaped fluorescent lamp with replaceable arc tube unit (joint development with Seiyu)
[Click to enlarge image]
Due to the enlarged lighting circuit, the new lamp is vertically longer than the existing incandescent bulbs (left).
Due to the enlarged lighting circuit, the new lamp is vertically longer than the existing incandescent bulbs (left).
[Click to enlarge image]
Contact portions for heat dissipation: When the arc tube and lighting circuit units are fitted together, the contact portions on both units (exposed copper parts in the photo) come in contact with each other. Heat is transferred through the contact to the base under the lighting circuit unit.
Contact portions for heat dissipation: When the arc tube and lighting circuit units are fitted together, the contact portions on both units (exposed copper parts in the photo) come in contact with each other. Heat is transferred through the contact to the base under the lighting circuit unit.
[Click to enlarge image]

Hitachi Lighting Ltd and Seiyu Co Ltd jointly developed a new bulb-shaped fluorescent lamp that can be separated into a lighting circuit unit and an arc tube unit.

The lighting circuit unit can be repeatedly used by replacing only the arc tube unit when the tube reaches the end of its life (approximately 10,000 hours). In addition to the power-saving feature, which is the advantage of fluorescent lamps, the new product helps to reduce the amount of waste, which saves resources. Hitachi Lighting intends to sell the new lamp by highlighting those features.

"We hope to replace 30% of the products on the bulb-shaped fluorescent lamp market with the detachable type in the next five years," the company said.

The total flux of the incandescent color (model number: FTH15EL/13/ADE) is 810lm and that of the daylight color (FTH15ED/13/ADE) is 730lm. The company aims to replace 60W incandescent bulbs with the new product. The power consumption of the latest lamp is 13W, which is about 1/4 of that of a 60W incandescent bulb.

The lighting circuit unit has a life of about 30,000 hours. The arc tube can be replaced three times for one lighting circuit unit.

Assuming an operating time of 30,000 hours, the new lamp can reduce the amount of copper used in the lighting circuit unit to 1/5 of that required by the company's existing bulb-shaped fluorescent lamp, which has a life of only 6,000 hours. According to the company, CO2 emissions during production can also be reduced by about 70%.

The company reportedly improved the composition of filler gas in the arc tube so that the lamp becomes bright immediately after it is turned on. But, because the new composition has poor resistance to heat, the company adopted proprietary heat dissipation measures.

Specifically, copper contacts are provided on the arc tube unit and the lighting circuit unit so as to transfer heat to the base unit by heat conduction. The company also employed a technique to extend the life of the lighting circuit.

In general, the discharge voltage in an arc tube increases when the tube reaches closer to the end of its life, and continuous use may damage the lighting circuit. Thus, the company provided a protection circuit to detect the discharge voltage and shut off the current when the arc tube comes close to the end of its life.

With the adoption of the detachable structure and the protection circuit, the new fluorescent lamp is larger than the existing incandescent bulbs. Compared with the existing products (about 130mm long), it has a vertically longer shape (155mm in length), although its diameter (50mm) is equivalent to that of the existing products.

"We hope to make the dimensions comparable with those of the existing products by shrinking the circuits and the arc tube," the company said.

The new lamp is slated for launch Oct 1, 2008. During the first six months, it will only be available at Seiyu stores in Japan.

"The street price for a set of the arc tube unit and the lighting circuit unit will be ¥1,500 (US$14.11, price may vary depending on country) at the highest and that for the replacement arc tube unit will be ¥500 or lower," the company said, although there is no manufacturer's suggested retail price.