i have this thing lying around, took apart, exact circuit as shown. mike said about fuse resistor, its actually a bleed resistor for the half bridge cap. yes its using half bridge rectifier. isolation is through the small (hi freq?) transformer, but not sure inside i havent watch mike's video to the end. fuse? i think the whole circuit is a fuse, or some random (weakest) component.
about the half bridge rectifier, the adapter only pulling power when the mains is on +ve side, zero load on -ve. my recent testing using Uni-T UT202 clamp Aac meter registered different current reading from the mains when using between full and half bridge rectifier, same switching volt-regulation circuit, same Adc output reading, same transformer, only different bridge. half bridge showing less efficient power from calculation/comparison, i'm not sure why though, my circuit (different bridge will give different result/output/efficiency?) or the clamp meter that cannot register half loaded mains correctly.
i dont see any problem with the china adapter circuit, in fact i like the design... simple, i would say this is a cheap PS, not crappy (what do you expect from a small and light transformer and cheap product?), or maybe i'm on the low standard side
the only ridiculous thing is the spec written on the product, mine showing INPUT 220-240V 50Hz 350mA, OUTPUT: 5.1V-5.5V, 500mA±50mA, its like the adapter will draw min 5.1V which proved to be a bullshit from Mike's video. but mine is more humble on the current spec, at least it can do 700+mA on short circuit and not blowing to the face right away
just checked the noise, its around 50-200mV on open circuit and 1Vpp at short circuited iirc (i've pulled the output wire apart unintentionally
cant do the retest again for more accurate figure, late nite GTG)