EP 25 - $0.91 eBay USB Charger

I purchased a USB charger for $0.91 on eBay with free shipping... Is it any good? Let's find out with an oscilloscope output analysis, dynamic load test, hi-pot/megger test, internal teardown, and a complete reverse-engineering analysis!

Spoilers: It's a fairly low-performance charger with a maximum output current of about 0.2 amps at 120 volts input and 0.4 amps at 240 volts input. It passes the hi-pot test, but has no internal RF suppression (and thus may not pass EMI regulations in your area). The circuit itself is actually quite fascinating, and uses only 1 transistor to achieve full-range voltage regulation and transformer oscillation.

Overall I think this charger would work well for small non-critical loads such as Arduino projects, USB-powered night lights, etc. Due to the possibility of regulation failure or even primary-secondary breakdown, however, I would not recommend using this adapter for expensive loads or for loads which may present a shock hazard if they were to become live at mains voltage.

Thanks for watching!

To skip to the teardown and reverse-engineering, skip to 20:42

I purchased this charger from an eBay seller called "zong-hk", in case you'd like to buy one.

[Plan-C]

Thanks. Nice explanation. Keep it up. Subbed ;) At least they went to the bother of a 'fuse' on your one. No such luxuries on mine lol!