When I first attached a 280 ohm resistor in series with a 5 mm red LED, the word on the street was that LEDs were low power, forever-lasting devices that would just about completely replace incandescent bulbs for simple binary indicators. LEDs spent a brief period as the numerical display device of choice too, until supplanted by the LCD. Regardless, the bottom line was that LEDs were really easy to work with. Just put that resistor in series — usually, you didn’t even need to do the Ohms Law calculation — rules of thumb were good enough.

Well, for simple binary indicators, that still holds true, but the big noise in LEDs these days has little to do with binary indicators. It’s in illumination, and in illumination, all the rules are different.

High-brightness LED illuminations devices are some pretty seriously engineered systems. Most have current regulated power supplies. Portable applications often have buck/boost supplies allowing for constant brightness over the life of the battery. And most have serious thermal design work put into them as well. LED lighting designers not only need to worry about all those power supply issues, but also about heat sinking and exotic design techniques such as metal core PCBs and heavy copper. Though it’s just an LED, the layout and assembly issues are far from trivial.

Duane Benson
Wear shades ’cause when you’re cool, the sun always shines.
Or maybe someone’s just trying to blind you with a bright LED flashlight because your ego got too big

http://blog.screamingcircuits.com/