15-20 minutes of what? in the bios? In some OS? In some application/game? Screen sleep settings? Screen saver?
Tell us more...Motherboard, OS/revision, etc.
This message was posted on behalf of Intel Corporation
In order to address this issue we will need more information, please try to be more specific about the blank screen, also I would like to gather more information in regard to your system, so please download the Download Intel® System Support Utility, and attach it, with this report I will be able to confirm some of that information.