@oscherler the datasheet I found states: "At no load or light load, the converter may operate in pulse skipping mode in order to maintain the output voltage in regulation. "

It should not self-destruct, but the output voltage might be more unstable as desired. Unless whoever built that module did some questionable component selection which is entirely possible for those cheap boards.

One thing that can lead to smoked SMPS ICs is series inductance in the supply lines combined with small input capacitance with low losses (ceramic capacitors) and running it near the maximum voltage. I did some measurements on such a board and the 48V supply had 30V ringing on it (series resonant circuit of parasitic input inductance and input capacitance) with an absolute maximum rating of 60-odd volts that's a big no no and was the cause of that specific issue. Parallel input electrolytic capacitor = oscillations gone = chip survived. (I am a big fan of derating and safety margins so stuff lives longer....)

@stereo4x4 So I put a small load on a new board, a 1.6 V LED with a 1.2 kΩ resistor, which results in 15 mA at 20 V. I tried it with the lab power supply up to 26 V, no problem. I transferred it to my 24 V power supply, turned it on, it smoked immediately.

I checked on the oscilloscope for peaks at power on, but there aren’t. Anyway, I used a switch on the 24 V side when it smoked. >>

cc @diver300

@stereo4x4 @diver300 For the third one, I powered it on the lab power supply up to 30 V with the load. Tuned the output to 12 V. Tested power on and off several times with and without the load. Transferred it to the other supply. It works.

I suspect the culprit is the combination of (1) steep input voltage increase when switching on the 24 V with a rocker switch, compared to turning on the lab PS, (2) low output voltage (around 5 V) at factory settings, and (3) small or no load at the output.