I have seem a number of class 1 AC/DC switching power supply adapters for electronic apparatus. From outlook, it looks similar to class 2 adapter - plastic case. The obvious difference is that there is a grounding pcb containing a large area of copper track soldered on the solder side of master pcb. The side facing to the solder side has no copper track at all. The grounding pcb is connected to the earth terminal of the mains female connector on one end and to the earth of the DC output plug on the other end. I have following queries and seeking advice.
1. Function of the grounding plate The primary and the secondary is reinforced insulation and withstands over 3000Vac. Is this plate to change the whole safety protection system from class 2 to class 1? Or the plate is primarily for EMC suppression? 2. Earth continuity test After the unit is completely assembled, should we conduct the test between the earth terminal of the mains plug and the earth of DC output plug? 3. Hipot test As the unit is classified as class 1, 1,500 Vac is applied between the earth terminal of the mains female connector and the earth of the DC output plug. Actually, the primary and secondary can withstand 3000 Vac. Is it correct test voltage to apply after the unit is completely assembled? Thanks and regards, Raymond Li OSA
