"Performance test and review of mains to 5V 0.6A Hi-Link HLK-PM01"
http://lygte-info.dk/review/Power Mains to 5V 0.6A Hi-Link HLK-PM01 UK.html

Interesting circuit.
http://www.homemade-circuits.com/2012/03/how-to-make-simple-12-v-1-amp-switch.html

Digchip circuit detail.
http://application-notes.digchip.com/005/5-10593.pdf

This circuit has VIPer22A it is similar with AP8012 of Hi-link.
NTC Resistor for Temperature Protection.
(With NTC, resistance Decreases with temperature to protect against inrush overcurrent conditions. Installed series in a circuit.)

VIPer22A Datasheet:
OVERTEMPERATURE, OVERCURRENT AND OVERVOLTAGE PROTECTION WITH AUTORESTART

It is easier to buy Hilink, but I found it has interesting things.