This is very common and happens with most of inexpensive chinese bench power supplies and modules, such as DOYUI, WANPTEK, XY6012, XY6020L and so on.
The symptoms are the following.
Say, I have a led that needs 10V @ 1A.
Set output voltage to 10V and current limit to 0.5A
I connect the led and it starts to flicker.
When measured with scope, I see the output voltage swing from 0 to certain voltage (until current limit kicks in), with sawtooth waveform of relatively low frequency (1-200-300Hz). That frequency is dependent on the current limit - say, if led working current is 1A and I set limit to 0.1A, flicker will be about 10hz, but if I set current limit for same led to say, 0.9A, flicker will have higher frequency - about 30-40Hz. The flicker frequency is also depends on the maximum output voltage - say if I set output voltage to 30 volts instead of 10 volts, it will have approximately 3x times lower frequency. Flicker will be there, as long as CC mode is enabled. If I go to CV mode, there is no flicker.
Adding beefy capacitor at output (even via resistor), does not help at all - of course, it reduces the flickering, because voltage now won't sag that much, but problem is still there.
This is not an issue of particular unit - I tested a whole lot of them, and most of them have these issues. Even modules claimed to be CC led drivers, are having that issue - this one, as example:
https://www.ebay.com/itm/166506482076So is there any way to fix these issues?
I googled for circuits and found this schematic of inexpensive CV/CC module, which has same issues.
Anything can be fixed here?