sorry, but I don't get the point of what you mean. Maybe you can show the circuit elements that you refer from a picture of the actual PSU.
At least that I can say: there is no such thing as energy flowing back into the AC part. Typical PSUs have the following parts:
- input filtering
- AC -> DC (rectifier plus capacitor)
- optionally active PFC, which is a boost converter sitting between rectifier and capacitor
- high frequency DC -> AC
- transformer
- AC -> DC (rectifier, inductor [in most cases, playing an additional role], capacitor)
- output filtering
plus control circuits.