PC shutting down when gaming?

Hey guys,

I`m having a bit of a problem with my computer. In several games, when playing for several minutes the computer shuts off. It`s not rebooting and doesnt crash. It shuts off like it would be powered off. After that it can be turned on instantly.

I`m ruling out overheating - temperatures for cpu stays around 70 degress celsius. And gpu had even lower temperature. Also I can play other games no problem. (several months ago I finished GTA V and had no problems whatsoever) Also my roommate played dying light several times (it doesnt run smoothly on my pc and even lags at times, but didnt shut down a single time)

After reading forum posts i`m starting to worry my psu could be at fault here. I have Corsair VS 650 (if im not mistaken, it`s an old model). As the PC has worked almost a year now without problems, i`m ruling out also that I need bigger PSU. 650 is just enough..

But I checked with HWMonitor the readings and when playing it showed that at +12V line the value dropped to 11.2V (but regularlyit was around 11.6) . Some people also said that you have to change psu if it drops belove 11.6. Could this be the problem? And what could have made that happen ?

Also I have a warranty for it. Is this legit reason to go and return it ?