1. Remove any external peripherals connected to the laptop. (Including any docking station)2. Then unplug the power cord from the laptop.3. Press the Power button for 15 seconds to drain any residual power from the motherboard.4. Connect the AC adapter to the laptop.5. Press the power button to test whether the system will power on
From the morning, I need to work on my UNI project, but I always check dell support assist for updates and to see if my device running up to speed. In connection, I see there was a bios update, so I allowed it to update, then dell's support assist asked me to restart my XPS laptop as normal for a bios update. But when updating the bios, there was no screen text, saying there is a bios update. But the fans were loud as normal but no text and no progress bar for the bios update (The XPS 15 was plugin to a power supply). After one hour, no text, no windows 10 login, but the fan are still 100%, still plugin to a power supply and the screen is black showing no results and the laptop is still hot. I really needs this XPS 15 to work, and had this laptop over a year and no issues before. I hope not, that the bios update 1.9.1 didn't kill the motherboard.   Thanks 
Black screen when updating XPS 15 7590 bios version 1.9.1