[SOLVED] Earth connections in an isolated offline SMPS system?

[cupoftea]

Supposing you have an isolated offline 20W SMPS on a PCB in an equipment. The equipment has metal walls in its enclosure. -As such, im sure you would agree that this metal case must be earthed.
Also, on the offline SMPS PCB there is also some analog circuitry with microcontroller etc which is supplied by the offline SMPS.

Would you agree that the secondary of the SMPS must be connected to earth to reduce noise problems generally? Also, do you agree that there should be only one earth path from the mains earth, then to the secondary GND, then this earth being wired from there (secondary GND) to the chassis, where earth connects to the chassis in only one single place?
....Would you agree with that?

Also, do you agree that this means that the best way round this would be to connect the incoming mains lead earth to the offline SMPS PCB…..then to run a thickly insulated, thick earth wire from the earth point at the SMPS mains input, to the secondary ground…then to run another earth wire from secondary ground to the metal enclosure (chassis)?

Can you also categorically agree with us that in no circumastance should secondary ground be left floating? (ie, it should be earthed as described?)

 

[std_match]

AC or DC "floating"? To pass EMC testing, it is normally required to connect primary and secondary grounds directly, or via a capacitor.