If that was the case we would see other problems. Like artifacting while doing some tasks or the card shuttign down during operation instead of at sleep.
Have you tried to hibernate the PC and see if that helps? Or do you have ti set to hibernate after a set period of time? If so try to put it into sleep mode or standby mode not hibernate and see if that resolves the issue.
Also have you don eall the updates?
To check your power settings right click on the Desktop>Properties>ScreenSaver tab. Then under the Advanced or Powe settings.