Use of different type of capacitors

[EthanAlef]

From a reference design, there is a 0.47μF capacitor following the LIVE of the power socket.
Its BOM suggests using a film capacitor (CAP .47UF 305VAC Lead Spacing). I want to know what would happen if I use a ceramic capacitor of the same value instead? Thanks!

 

[albert22]

Non isolated power supplies are dangerous. The specs for the capacitor is for safety. I would suggest that you use the suggested BOM, not only for the cap but for all the components that go to the mains. Assuming that the BOM follows the correct design practices for this type of power supplies. I think that you need to include a fuse.

 

[WimRFP]

First consider what happens when the capacitor becomes a short. I am thinking of smoke, fire, shock, blown fuse, etc. A single fault may not result in danger for most consumer equipment.

Though you have a varistor at the input, I still would use an X3 class capacitor rated for your operating mains voltage. You don't need X1 or X2 because when designed well, the varistor will limit the impulse voltage. The film type capacitors have a "self healing" property. If faillure would lead to injury (for example electrical shock), you should use an Y capacitor, or a series circuit of 2, X capacitors to meet safety regulations.

I am not aware of ceramic X capacitors with that large values that you can use at 230Vac. If you find some, make sure that they have qualifications to meet electrical safety requirements, when faillure may lead to danger.

Off topic: Varistors also need safety considerations, as thay age over time and may overheat, explode, etc. At least read some safety application note related to varistors.