Filtering a flickering LED light?

[cds333]

I recently bought some 4ft LED shop lights from Walmart; 10k lumens, 4000k, and has a motion sensor and 3 brightness levels. https://www.walmart.com/ip/4ft-LED-Shop-Light-10-000-Lumen-with-Motion-Steel-Tread-Plate/266849907

Upon turning them on I notice they has a very subtle sporadic flicker (perceived as a rapid change of brightness). Some people may not even notice it but it bothers me enough that I cannot use them. They both do the same thing so not just a single unit that's defective. The LED lights I am replacing, as well as every other LED light in the house, have no such issues.

I'm thinking it is just the cheap Chinese circuitry delivering dirty DC to the LED arrays. However the flicker is not all the time, it comes and goes, so I really have no idea what the problem is. I don't know if it is letting through something from the grid or if the problem is completely internal.

I am looking for some kind of circuit to filter any AC out of the power going to the LEDs, and hoping that is the cause of the flickering.

Thank you!

[dobsonr741]

I would go and open up the case and take a look at the power supply. Perhaps look at the waveform going to the leds, of course after feeding it from a an isolation transformer 

I would look for poor assembly quality or overheating components, get a data sheet of the controller. Then I could make informed decisions on what to do.

[Marco]

Could always just replace the power supply with a fixed voltage or current one depending on what's in it.

If the micro doing the dimming is having some hickups in PWM it will be hard to fix passively.

[Georgy.Moshkin]

I have similar problem with a remote controlled 1.2 meter light. It has constant flicker plus occasional light intensity drops. I tried to add large electrolytic capacitor after single-IC AC to DC circuit, but there was no any improvement. It seems that problem is with the second stupid dimming IC that is somehow modulated by WiFi or cellular signals. The only good thing is that it "freezes" during off states, so LEDs are more safe from being overdriven. I agree that replacing the whole circuit is a good idea because trying to fix it by putting something between LEDs and dimming IC may be dangerous, or simply will wreck it. I haven't found any protection circuit, only two chips and few cheap capacitors. Very interested in replacing this PCB by something else. I thought about measuring current at maximum brightness, and then do some simple PWM plus limit the current of whole thing to 85%. Does it make any sense? I haven't studied this topic yet, so idea may be dumb.

edit: one more thing to note is that LED panel I've bought has three-pin connector, but the third one (ground) isn't connected anywhere. I tried to understand if I can connect ground wire somewhere to see if it helps with dimming glitches, but haven't understand 220 to DC single-chip circuit and assembled panel back. It seems that any grounding will result in short circuit. Annoying intensity dips are still there, it may work smoothly for 15 minutes, then flicker 2-3 times per minute, and so on. Simple LED light bulbs doesn't have such intensity dips, only "standard" flickering

[Marco]

If you're lucky there are standard low voltage LED strips in there, which can then be powered by a standard fixed voltage power supply (possibly with remote+dimming, cheap as chips for LED strips). Or you might be able to bypass the existing dimming and just feed it from the low voltage power supply already in there, if the dimming is the culprit.