Another Alternative: LED

Published:2011/5/30 1:50:00 Author:Phyllis From:SeekIC

Energy efficiency is a good reason for home owners to turn to LED lights and away from incandescent bulbs. It is still at the early stage to scratch the dimming and color-tuning possibilities of power LEDs. As a matter of fact, the LEDs are not a novelty as they have to fit straight into the sockets vacated by incandescent bulbs and work with no changes to the house wiring.

The current watchword of LED power chip makers is triac-dimmable which means the chip can work with dimmers designed for incandescent bulbs, and the LED will dim in accordance to the switch on the wall. In this chip every task is of vital importance as the intensity curve of a LED is totally different from that of a light bulb so some sort of translation has to be included. NXP was on the scene for a long time with its SSL210x range and there are also drivers from other manufacturers like National Semiconductor, Power Integrations, iWatt and so on.

There are a lot of dimmers, but not all wall dimmers are triac-based. Some have to work with transistors while not all chips are compatible with both types. Some of the dimmers are awful, so before making a dimmer-compatible LED light bulb one had better be prepared to do some wide-ranging testing. Even with great dimmer, a great chip and a great circuit, it is still inevitably to get 100:1 dimming range. Compared with incandescent bulb, this is much better. To achieve the 500:1 or more in the home is still hard. 500:1 might be a complete waste of time in a kitchen, but in a bedroom this range gives you a night light as well brilliance.

A downside of incandescents dimmer in the circuit lies in that they can not work with LEDs at the lower end of the current range, so all the triac-dimmable chips have to bleed, and therefore waste current through the dimmer to keep it operating. The related integrated circuit is KDS120.

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