Monitors sleeping

Acer aspire 515 51 50y5 laptop

I have dual monitors and shut the laptop lid.

Intermittently, one or both monitors go to sleep. The laptop gives a USB unplugged alert. Wiggling mouse and/or keyboard presses wake it with USB connected alert sound but it takes seconds to redraw. This can happen several times in 5 minutes then not for hours.

I’ve switched power management to never sleep, disabled PC from putting usb devices to sleep in device manager, disabled selective usb suspend, disabled the monitors’ own sleep function.

Any suggestions to stop this happening?

Hello and thank you for posting!

Thank you as well for the detail you provided and the troubleshooting that you have already performed that is much appreciated.

Based on your description, it sounds like you are using our USB 3.0 Universal Laptop Docking Station known as the UD-3900 → Please let me know if I am mistaken.

Assuming for the moment that my impression is correct, based on your description of the behavior the first step is to connect the dock to a different USB 3.0 port within your Acer laptop. Doing so will help rule out the current USB port within the laptop as a contributor to the current behavior.

Please let us know if that helps!

Thank you,

Plugable Technologies

Hi Bob

Thank you for the fast reply. It is the UD-3900.

Unfortunately my laptop only has one USB 3 port. The others are USB 2


Hi Liz,

Thank you for getting back to us so quickly with the product confirmation and additional information, and you are of course most welcome for the help.

For the purposes of our testing, it is okay to temporarily connect the dock to a USB 2.0 port within your laptop (the dock will still work when connected to a USB 2.0 port).

Please let us know if doing so helps, and we will determine the next steps from there.


Ok, switched the ports at 3.35pm uk. I’ll see how it goes for the rest of today.

Thanks Liz!

Please just let us know the results as time allows, and we will move forward from there.

Thank you,


Yay! Worked all day today without a single outage.

The performance on usb 2.0 seems fine, so is there any reason not to just keep using this port?

Hi Liz,

Thank you for getting back to us with the update, and I am glad to hear that the behavior has improved.

In regard to your question, while the dock is connected to a USB 2.0 port within the laptop the dock’s front-mounted USB 3.0 ports will function at the lower USB 2.0 speeds. The performance of the dock’s Ethernet adapter may also be impacted.

If the current level of performance meets your requirements, I would suggest leaving things as they are.

Thank you,


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