External monitor with mild flickering while charging

[wilsonseixo]

System: Windows 10
Battery or AC: Both
Model: N56VZ
Frequency of occurrence: Always
Reset OS: Yes
Screenshot or video: Yes
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Detailed description：
When I plug in an external monitor to my laptop ti has some mild flickering to it.
Tested with different monitors and different VGA cables. Also tried plugging in an HDMI to VGA adapter to the pc's HDMI port and the noise continues.
Then I noticed that it happens only with the charger plugged in. I also noticed that the flickering intensity changes if I change the energy plan (weakens with lower consuption). If I remove the charger the problem goes away. With charger, with or without the battery, the problem appears.
@Blake_ASUS I've seen you responding to a similar issue on another topic and decided to tag you here.

[Blake_ASUS]

Hello Wilson,
Well....it does look like electricity interference.
This model is quite old, but we can still try to update BIOS
https://www.asus.com/SupportOnly/N56VZ/HelpDesk_BIOS/
If you BIOS is the latest version, it is very likely that the device need to be repair.
However, I'm afraid that we don't have the spare part anymore.
May I know when did this issue start to happen?
Thank you.