If you would like to provide constant power to your camera you will need a power adapter. They are available for most camera models but not all.
There are many and varied AC adapters and DC couplers available.
The one or ones you need will be based on the camera model and battery type / model number.
To determine which you may need please visit the following resources to help you:
CANON: Canon accessories
FUJI: Fuji accessories
NIKON: Nikon accessories
OLYMPUS: Olympus accessories
PANASONIC: Panasonic accessories
SONY: Sony accessories