I am signed up for a Digikey newsletter and there is an article about a new chip for controlling LED lamp replacements for incandescents.

It can give you an idea about what is going on in these things. It sure is more than a string of LEDs and a resistor.

http://reference.digikey.com/TZ/lighting/TZL112.US/WebProject.asp?CodeId=7.4.4.12&pagelabel=55

Greg Fretwell