In KDE system settings it's called "screen locker", and I don't have it active even.
Still when I don't use a mouse or keyboard for some 15 minutes it just blanks the screen.
I really don't want it to turn off the desktop because I might be just off to the kitchen to make some coffee or so; it would be a drag to have to reboot every time
EDIT: I found in Power Management that there's "dim display" set for 10 minutes, and "screen energy saver" for 15 minutes.
I could set them longer, but I still wonder about the difference with other pc's.
Reactivating the screen takes about 4 seconds - no drama of course, but strange just the same.