Re: low voltage & bulb species

From: Michael M. Butler (
Date: Fri Jul 06 2001 - 00:59:22 MDT

What about 'em? :)

AFAIK, there are two typical ways LEDs/matched LED arrays are powered.

1) The cheap way is to use a DC power supply (there are various degrees of complexity & efficiency) and drop some
fraction of the supplied voltage across a resistor, limiting the current to the LED or matched array. This is relatively
inefficient, but simple. Depending on the power supply type, you could get good or poor behavior. If the voltage the LED
sees is below its "turn-on voltage", you'll see virtually no light. Above that, say at 20-50 mA per LED (a plausible
SWAG), a 10% reduction should still provide reasonable illumination.

2) The sophisticated way is to do active switching regulation in one step, from power source to LED, constant current.
This can be tailored to provide high efficiency at many voltages. But the consequence is that (approximately down to the
voltage where the power supply stops working, whatever that is) power use with LED on is also approximately constant.
Good for the lamp user, not so good for the power utility.

Robert Coyote wrote:
> What about LED's?

This archive was generated by hypermail 2b30 : Fri Oct 12 2001 - 14:39:42 MDT