I replaced fluorescent lights in our kitchen with LEDs. I can see an occasional flicker with the LEDs. Is the flicker caused by the way the bulb(s) was made or the AC input to the bulb? I haven't been able to get info from LED mfgs (customer service staff), they have all responded that they do not have any data as to the refresh rate of their bulbs. ???
The LED lights flicker if the power supply is not constant. There could be many reasons for this:
One kind of fluorescent replacement puts a string of LEDs into a fluorescent fixture. The ballast of such a fixture will make light pulses at 120 Hz, if it is an iron ballast, and several kilohertz if it is electronic.
One kind of LED power supply makes unfiltered (pulsed) power, usually 120 Hz, but possibly 60 Hz. This is inexpensive, but poor design. It is possible, too, to fit an AC fixture with LED lamps intended for DC power. That's worse than poor design, it's malfunction.
If the fixture has an LED constant-current-source regulator, it is possible that there's electrical interference with some nearby appliance (a microwave oven, or an induction range).
There could be a bad switch (or loose wiring) causing the lights to flicker.