blank screen when connecting to external power

Hi,

I have a windows 7 64 bit HP Envy 13 laptop. I love the laptop and it works well for what I use it for. However, when I am using it and I connect it to external power, the screen goes blank. I have to put it on standby and wake it up again for the screen to come back on. Not sure what to do about it and I've just been living with it but figured its time to take a look and see whats going on.

Please let me know if you would like specific information and i'll be happy to share.

Thanks!