User:Juventas/Power supply unit (computer)


 * This article is about standardized computer power supplies. There are many designs that are unique or proprietary.

A computer power supply unit (PSU) is a device that converts electrical power for a personal computer. Typically it is a switched-mode power supply converting mains electricity for one or more loads requiring direct current (DC) voltage.

Desktops, workstations, and servers commonly have internal power supplies that require active cooling and follow a standardized form factor. Laptops and netbooks more commonly have an external power supply that complements a rechargeable battery. Thin clients and nettops can have an internal small form factor power supply or an external power supply.

Common attributes
A desktop power supply is mounted inside the computer, with one outer face. The outer face has a C14 inlet allowing the user to remove or replace the power cord. The outer face also features holes for ventilation, threaded holes for 6-32 machine screws, and in some cases an on-off rocker switch, or a recessed switch for selecting 115 V or 230 V mains electricity. The inner faces also have holes for ventilation, a specifications label, and a hole feeding bundles of wires leading to an assortment of plugs for the computer's internal components.


 * internally, metal case, fans

History
The first standardization of desktop power supplies started with the IBM Personal Computer in 1981. It's power supply design was copied by other manufacturers for what became known as IBM compatibles. IBM changed the size with the IBM Personal Computer/AT, which later included smaller models known as the Baby AT form factor. The basic design of the power supply remained unchanged until 1995 when Intel released the ATX computer form factor.

ATX added support for standby power which allowed software to turn the computer on or off. To accommodate this feature a new power connector for motherboards was created. ATX spawned small form factor designs such as SFX and many proprietary ones using standard connectors. In 2000, in response to changing power requirements it evolved into ATX12V. As of 2010, every desktop power supply incorporates the same basic features of ATX.

Comparison to desktops
Entry-level workstations and servers closely follow desktop power designs with notable exceptions. These exceptions are typically because of increased power consumption or the need for redundancy. Additionally, rackmount servers require form factors that compliment the strict constraints of a 19-inch rack.

The increased power offered in these designs have also made them popular in enthusiast computing, most notably EPS12V.

Laptops and netbooks


Laptop and netbook power supplies are accessories sometimes referred to as power adapters or AC adapters. They complement the device's rechargeable battery to charge the battery, provide power directly, or both simultaneously. They typically provide only one output voltage, with the necessary voltages obtained in the device by the means of a DC-to-DC converter. Smaller power adapters plug directly into the wall outlet without a power cord, whereas larger ones use a C6 or C8 inlet and a power cord.

Thin clients and nettops
Thin clients and nettops have low power requirements and a small form factor. If the power supply is internal and not proprietary, it will use a TFX12V or smaller form factor. If the AC input is less than 2.5 amps, it may use a C6 inlet instead of the usual C14.

In other cases the power supply is external with an internal DC-to-DC converter, similar to a laptop but without a battery.

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