[lightedman]

It only doesn't flicker if there's no power driving circuitry - eg just LEDs and a resistor.

Otherwise, if there is a power IC present, there is flicker, though fast enough for most humans to not perceive normally (you can still check it by waving your hand in front of the light and seeing the strobed afterimage.)

[mnw21cam]

That's not strictly true. The very simplest of DC LED drivers flicker, such as the classic single-transistor battery saver circuit, but a slightly more complex DC LED driver circuit will not. One of the best ways to drive an LED is with a constant current source, which typically involves putting an inductor in series with the LED and switching the supply to that at a reasonably high frequency, which would mean the LED does not flicker at all.

[dv_dt]

If it's hooked directly to AC power, isn't there by definition a flicker? With a power IC, a poorly implemented power circuit will also visibly flicker. With high enough rate and the right power characteristics it should not be noticeable. Do you notice flicker in a quality phone or monitor screen?

[zahirbmirza]

Yes! And this after image is distracting.