Cheap Power Supply Pitfalls

[jjoonathan]

There are many like it, but this story is mine.

My first "power supply" was the cheapest I could find, a little 0-40/0-40V boost-buck module that supported CC, CV, and could be easily powered from wall warts I had lying around. See attached image. They're still available for ~$15. Having been warned about cheap power supplies, I checked the turn-on and turn-off waveforms and found them quite satisfactory. Then I attached my DUT and after the second or third power cycle its microprocessor popped. It turns out that if you unplug this thing, regardless of whether or not output is enabled, it dumps its capacitors into the output -- 50W for a few milliseconds. Enough to fry my microprocessor. Bam.

My next power supply had a brand name and has remained trustworthy to this very day

[cepwin]

Thank you for posting this....it's not something I would have expected!