Power Armor would make you more than "man sized".
1st, your problem is a power source that is protected enough that doesn't fail in a battle but powerful enough for your "armor".
2nd, while all your metal plates might protect you against piercing bullets, the gaps between your plates won't protect against concussive blasts such as from an explosive, grenade.
So you'd need a metal (material) strong enough between the gaps in the armor to protect against that flaw.