Latitude 7490 USB-C power output to external display

If you had configured your laptop with USB-C, it will provide video signals but does not have power delivery.

If the optional thunderbolt 3 was configured, the port will provide video signals and power delivery.

@Chino de Oro​ The only marking near the port is a "D" DisplayPort logo.   According to https://www.displayport.org/displayport-over-usb-c/, DisplayPort over USB-C supports up to 100W.  I cannot find any Dell documentation stating exactly what the power output is on the port of this machine.  It clearly isn't 100W.  But I'd like to know if it is supposed to be at least  the 10W needed by my display.  If it is less, then I understand the limitation.  If it is supposed to be more then 10W, then something is either not functioning properly on my machine.  Or perhaps there is a setting to increase the power output I can change.

Try to see if changing Power Option to high performance (in Control Panel) may help with increasing power to the port.

The Dell Latitude 7490's USB-C port with the DisplayPort label supports 65W power delivery, not per port but for the entire system. This is enough to power your Viewsonic VA1655 display which only requires 10W.

Here's a breakdown of the information:

• Dell Latitude 7490 USB-C port: 65W Power Delivery (PD)
• Viewsonic VA1655 "margin: 0;">While the TB4 cable shouldn't be the bottleneck, the issue with inconsistent brightness might be due to:
  1. Power Delivery Negotiation: The laptop and display might not always agree on the optimal power delivery during connection. This can lead to the display receiving less power than it needs for full brightness.
  2. Dell Latitude 7490 Power Management: There might be a setting in the BIOS or Dell power management software that limits USB-C power output under certain conditions.

  Here are some things you can try:

  • Update BIOS and Drivers: Ensure you have the latest BIOS and drivers installed for your Dell Latitude 7490. These updates might include improvements to USB-C power delivery.
  • Check BIOS for Power Delivery Settings: Look for any USB-C or Power Delivery settings in the BIOS that might be limiting power output.
  • Dell Power Management Software: Check the Dell power management software for any settings related to USB-C power delivery or display power. You might find options for prioritizing performance or battery life, which could impact power delivery to the display.
  • Try a Different USB-C Cable: While unlikely, there's a slight chance the current TB4 cable might have an issue. Try using a different USB-C cable that supports Power Delivery (PD).