Corsair CS450M experiences

I bought a CS450M PSU a couple months ago, changed from an older VX450W. My first impressions are positive, I was a bit afraid of the GreatWall inside, but it works fine, as quiet as the VX, and consumes 8-10W less than that in Idle, and much less under load! The only strange thing is a clearly hearable "clicking" noise, (like a switching relay) when power off my computer. Is this normal in this model? Cause I haven't experience anything like that in any of my PSU-s before..