Stop XPS 27 from sleeping when HDMI in attached

I am using an XPS 27 All-in-one as an external display via the HDMI in port, selecting this via the soft buttons on the front of the display. This works great, except that the Windows computer has to be booted up to use the monitor, and its power saving settings kick in every 15 minutes to shut off the display. So now I have to move the XPS mouse every 14 minutes to prevent the monitor from going to sleep.

Is there a way to prevent the monitor from going to sleep when in HDMI input mode, or is the only way to change the Windows power saving settings (which I would prefer not to do)?

Thanks!