Bright future for energy efficient lighting

The chip measures lamp operating qualities, primarily crest factor (the ratio of peak to rms current), to check for faults. A normal crest factor is less than two. When it exceeds four, the chip shuts down the ballast. This condition generally indicates the lamp is at its end of life.

One ballast chip can also run several CFLs simultaneously, says IR, thus providing economies for multiunit installations. And IR's Ribarich thinks the new chips will likely find their way into ballasts for linear fluorescent tubes as well. In this case, ballasts would need external power factor correction, he says.

HALOGEN ICs
Another ballast chip for halogen lamps uses the same basic technology as the CFL driver, but incorporates more sophisticated fault detection. Called the IR2161, it can adapt itself to changing supply voltage, frequency conditions, and lamp conditions.

"This chip must be more sophisticated to catch all the possible fault conditions," explains IR's Ribarich. "That's because the user can connect low-voltage halogen lamps to a track indiscriminately. We've seen cases where buildings burn down because someone hung too many lamps on a converter recessed in a ceiling. It can overheat and fail violently."

IR claims its new halogen ballast chip detects all such fault conditions. If it detects a shorted track, for example, it shuts down the ballast and repeatedly checks to see if the short has disappeared. If it detects too many lamps attached to the track, it blinks the lamps as a signal.

Like the CFL device, the halogen lamp chip reduces ballast part count by 20%, says IR. It also has an active dead time circuit that maintains soft switching regardless of the external conditions. Softstart limits inrush current to the lamp filament to boost lamp life. The chip also is compatible with triac wall-switch light dimmers.

Halogen lamps are not inherently energy efficient, so the motivation for using the ballast ICs is space savings and reliability. But odds are that there will be more ICs in the offing for ballasts. IR's Ribarich says the company is examining the concept of ballast chips for high-intensity discharge lamps. Most HID ballasts are magnetic, partly because they generate a lot of heat. Electronic ballasts for these devices must sit relatively far away from the lamp. And electronic ballasts for HID tend to handle 400 W or less. Today, higher power lamps of 1 kW and above are strictly magnetic.

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