My early 2011 MBP goes to sleep even when Sleep is turned off and the power is plugged in.

Basically, it just decides to go to sleep after a few minutes of it being idle. Searched around but I couldn't find a similar problem. I've already tried resetting the SMC, but that hasn't fixed it.

Any ideas?

It's a early 2011 MBP unibody, running Mavericks.