Difference Between an AC Adapter, Power Supply and Charger for Laptop Computers

By Dan Stone

The AC adapter, power supply and charger are all the same thing.
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There is no difference between an AC Adapter, a power supply and a charger in reference to a laptop computer: all three functions are handled by the device's external power device. With laptops, all three names refer to the same device that's commonly referred to as a "power brick." There are other devices that individually serve as internal power supplies, external power supplies and battery chargers; however, all laptop power units provide both power and charging functions from an external source.

The Same Unit

Other electronics use the terms AC adapter, power supply and charger to refer to specific devices that perform certain tasks in exact ways, which makes it unclear that the laptop power device is actually all three. Laptop computers use an external power supply, also known as an AC adapter, to power the computer and to charge the battery. The laptop's battery could also be considered a power supply since, when charged, it serves the same purpose.

Power Supply

A power supply or PSU is a device or component that takes energy from an Alternating Current electricity source and converts it into usable Direct Current for another electronic device. The power supply also makes sure that the computer doesn't receive too much or too little electricity, which could cause the system to fail or break. The term "power supply" is typically associated with desktop computers and refers to a component braced to and housed inside the computer case. Internal power supplies are rectangular or cubed shape and run several inches in all directions; they usually have built-in fan cooling units that expel hot air from the rear side of the computer case.

AC Adapter

The term "AC adapter" refers to any external power supply used by an electronic device. Laptops use external power supplies to decrease the space used by components inside the case because the smaller size is much more important to the portability of a laptop than it is to a desktop computer. Additionally, laptop computers can also run off battery power, meaning that they can go without the AC adapter for several hours at a time. The AC adapter is not always necessary to use with the computer and can weight a few pounds, so there's no need to lug it around with the system at all times.


A charger is a device that replenishes a rechargeable battery; the term charger is used interchangeably with laptop AC adapters. However, "charger" isn't precise, because the laptop's AC adapter does more than just charge batteries. There are other devices for charging batteries also referred to as chargers that do not supply a constant power source for a computer or another electronic device.