I recently installed an Ubuntu 18 on a DELL laptop with an NVIDIA graphic card. I selected during the install process, the installation of proprietary software. Since the installation, it seems that when I am running on battery the brightness of the screen is changing constantly depending on the amount of white there is displayed on the screen. That does not happen when I am plugged-in. Back in the days I had the same issue on windows with an AMD graphic card, it was a "power saving" feature. But I can't find any information about this on NVIDIA under Linux. Does anyone know how to disable it once and for all?