Laptop underperforming when plugged in

[Kevocalypse]

For some reason when ever I play BF3 when plugged in my cpu speed drops to 1.8 from 2.8. This causes the game to run at 25-30 fps in multiplayer which isn't very smooth. When I unplug however my cpu goes back to 2.8 and my fps goes up to 45-50 and sometimes even 60 in multiplayer. However it randomly drops to 9-12 fps every couple of seconds and skyrockets back up which makes it unplayable. This doesn't really make much sense. My temps aren't high and I'm running on high performance mode for both plugged and unplugged.
CPU: A8-5557m
GPU: 8750m w/ 2gb of vram
8 gb ram
Acer Aspire v5 552g-8632

 

[Imran60]

You should to change the plug of Your laptop.

 

[Meghan54]

Have you checked your power settings in control panel? Make sure your cpu is set to 100% when plugged in. First thing I'd check.