Recommended architecture for mains-powered design:
A very specific request!
: Frequent failure points include shorted power MOSFETs in the PFC stage or a faulty start-up resistor feeding the A20112's VCC pin . 12V 1A SMPS Power Supply Circuit Design on PCB a20112 power supply schematic
Measure across C1. You should see ~300V DC (for 230V AC). If zero, check F1, MOV1, DB1. a20112 power supply schematic
provides galvanic isolation while stepping down the voltage. Output Regulation a20112 power supply schematic
Specifically models like the HSP400-5S01.
This is the heart of the unit.