external display slow to wake up after sleep

I use windows10, 64 bits last version. After a windows update my Dell laptop had the following problem:
the external display does not wake up instantly as the laptop display does. The longer the sleep,
the longer it takes to wake up.
A windows technician repaired this problem, but the price to pay was terrible: all my Office 365 programs outlook,
Word, Excel, ... were no more working and Edge was no more working. Probably, he was a first level technician.
An Office 365 technician restored, after on hour work, Office365 and an other Windows technician restore Edge that did not work even uninstalling and reinstalling!
Now everything is working and has been restored BUT the problem is back.
Any help welcome,
daniel0350

@daniel0350, Welcome to TenForums!

Can you think of any changes that you made just before the problem came back again? Clearly, if the problem was not there and then it suddenly came back, something must have changed to trigger this behavior.

Did you install any updates to display drivers or Windows updates just prior to the problem returning?

Also, could you provide a little bit more detail on the issue? Here are some of the specific items that I would be interested in knowing about:

1) How is the monitor connected (HDMI, DisplayPort, etc)?
2) Is the monitor connected to the laptop directly or to a docking station of some sort?
3) What is model number of both the laptop and the monitor?
4) Does the monitor have a power light on it that changes color or turns off when sleeping? If so, does the power or sleep state light turn on right away or does it also take a long time to turn on?
5) When you say that it takes a long time to turn on, could you provide some more detail? Does it take 5 seconds to turn back on, 30 seconds, one minute? I just want to have a clearer understanding of the symptoms.
6) If your laptop or dock has more than one type of external monitor connection (example, both HDMI and DisplayPort) and you monitor can also accommodate those, have you tried connection via the other connection type?
7) Have you tried another cable? I've seen my fair share of low quality cables causing issues.

The first time the problem occurred it was after a windows 10 update. Then the various windows technicians solved the problem. However, Edge asked me to do an update and then again the problem reappeared.
1. The monitor is connected by cable HDMI.
2. Monitor connected directly to the laptop.
3. the monitor is HP w2207h, the laptop is a Dell XPS 15 9570 , 6 months old.
4. I will check for that in my next contact with you.
5. After a short sleep of few minutes, the laptop display wakes up instantly and the external monitor a few seconds after.
After a long sleep of ten hours, the laptop display wakes up instantly and the external monitor after about one minute.
I shall measure exactly the time and communicate to you tomorrow with my answer to number 4.
6. Only one type of connection.
7. I did not try an other cable.

Thank you so much for your help and I shall try to send you the missing information tomorrow.

I downloaded the user guide for your monitor and there wasn't anything blatantly obvious. You might try disabling the power saving from the monitor menus to see if that helps at all. Also, make sure that your HDMI cable is really well seated both on the computer side and the monitor side.

I'll dig a little more and if I have any other ideas will let you know,

It seems that the situation is not static: it is improving. The delay to open the external display reduces. I shall give exact time figure later.
Thanks,
daniel0350

- - - Updated - - -

Actually, the second external display wakes up after 6 seconds provided I start to enter the Password on the laptop display.
Is this normal?
I do not know but for me, it is OK now.
Thanks so much for your interest,
daniel0350

- - - Updated - - -

My final information is the following:
After a long sleep of ten hours, the laptop display wakes up instantly, the external display only after two minutes and thirty second. However if I start to insert the password in the laptop display, the external display wakes up four seconds later.
Is there an explanation to this mysterious behavior. A last comment, if I wake up from a ten minutes sleep, BOTH displays wakes up instantly!

I don't use an external monitor with my laptop, but I may try to test this later if I have a chance.

I'm just going to take a guess here, but maybe someone using an external monitor can comment.

My guess is that if you are extending your desktop then it would make sense to me that the external monitor might not wake until you have logged on, because you don't have your full desktop until after you have logged on.

But, if you were to setup that external monitor to mirror your laptop display, I wonder if it would not wake up almost immediately (or at least within a few seconds).

I do not use Extend but only Duplicate.
Thanks,
daniel0350

Well, that kills my theory

I may have found the culprit.
In Sign in Options, there is:
"Require Sign in" is set to 15 minutes. So this would explain the difference between a short sleep less than fifteen minutes and a long sleep.
I shall put it to never and see what happens. I shall let you know tomorrow.
Thanks,
daniel0350

- - - Updated - - -

I was completely wrong: this has nothing to do with the problem.
Sorry,
daniel0350

- - - Updated - - -

In order to sum up the situation: the first time this slow opening of the external display occurred was after a windows 10 update.
_a windows first level technician "cleaned up" the laptop and solved the problem. However, the price to pay was terrible:
all my Office 365, Outlook, Word, Excel,..., were no more working as well as Edge. An Office 365 technician worked one hour, uninstalled all Office and reinstalled it. A Windows technician tried to reinstall Edge and could not. Finally he installed an OLD version of Edge and every thing worked fine: Office, Edge and external display opened immediately after a long sleep.
_ Edge asked me to update. I did the update and the problem of the external display waking up slowly after a long sleep reappeared!

My feeling: those updates must disable something that prevents the fast opening of an external display after a long sleep.
What is most mysterious is that short sleep, less than ten minutes do not perturb the opening of the external display.
Any idea, welcome,
Daniel