Screen brightness issue in aspire 5750G

I have this laptop Aspire 5750G, and since yesterday I noticed that thee brightness suddenly drops down to a low level, which I then adjust it to a level as I like it to be. But it fails after a full charge again, about couple of minutes after I unplug it.
I have Windows 7 home premium on this laptop, which is fully updated inclusive their drivers.
I was wondering if anyone know what the cause might be and how to fix it.
thanks in advance

 

Check advanced power settings in Windows for the power-plan you are using. There is an option there to dim a screen to a certain degree You can set it) in a given time (again you can change it) since the notebook has been unplugged.

That might be it.

 

I have two types of power settings on this laptop, and under the one that I usually work with there is a setting under Monitor->Dim view after, and it was already set to 5 minutes, that seems like the one you are referring to. I haven't changed this value before, but does it mean that it will dim the brightness after 5 minutes? Should I set it to 0?

 

It's one way of doing it. The other way is changing the brightness of a dimmed screen to match the one that is not-dimmed. This way even if it insists on changing the brightness it will change it to the same one that you already have.

 

This method I mentioned knew it already and had not changed it, and the other setting is set to show in a higher brightness level. But at this setting it drops to the lowest level.