Sleep Mode

I'm having trouble figuring out how to set my sleep mode so that it doesn't get triggered if I'm running background processes. It keeps interrupting scans, downloads, uploads, etc. The thing is, I don't want to stop my computer from ever going into sleep mode because I don't want it to just keep running if I'm not using it for anything. Is there a way that I can set it to sleep ONLY if I don't have background stuff running? My old computer just did it automatically and when I looked through the settings (I have the XPS15) I couldn't find any options other than a specific number of minutes or never.