Ölbaum

I bought these buck converters to power a 12V fan with the 24V power supply of my soldering iron, and when I powered one on with 24 V, it immediately smoked. I’m pretty sure I didn’t reverse the polarity (unfortunately, I desoldered it, now,) but I didn’t connect anything to the output, and now I notice that one of the pictures say not to use with no or light load (< 10% of output power.)

Is that really a thing? #Electronics

https://www.amazon.de/dp/B0FZK4249L

Pack of 6 DC-DC Buck Converter, 4.5-28V to 0.8-20V Step Down Converter, MP1584EN 3A Power Downward Adjustable Voltage Regulator Module, Adjustable Converter 24V to 12V, 9V, 5V : Amazon.de: Business, Industry & Science

Pack of 6 DC-DC Buck Converter, 4.5-28V to 0.8-20V Step Down Converter, MP1584EN 3A Power Downward Adjustable Voltage Regulator Module, Adjustable Converter 24V to 12V, 9V, 5V : Amazon.de: Business, Industry & Science

Apr 1 at 7:59pmWeb
Show threadMalin Dixon1d ago
@oscherler Yes, buck regulators have different modes of operation, continuous and intermittent. At low power, the buck regulator may not be able to turn off fast enough to prevent the output voltage rising too high. Those buck converters don't seem to have the big capacitors which would help the stability.
Show threadrawe1d ago

@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....)