It is a heat issue. Short of fixing it, go to the power control settings and tell it to run at the low power saving speed while on AC power. Here are some troubleshooting steps that may help.
- Start by testing the AC adapter if it's supplying the correct voltage in your laptop.
- Do also try a different AC adapter that has the same voltage with yours and see if the same problem will persist or not.
- Next is to do a clean install of the graphics card driver.
- Go to Device Manager and uninstall the Nvidia graphics card driver.
- Next is to open Programs and Features the uninstall anything related to Nvidia.
- Once done, download and install the latest driver.
- Here's the link: nvidia.com/Download/index.aspx
- Reboot the laptop after installing the latest driver.
- After the reboot set Nvidia as the default GPU and change the Power Management option as well.