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User:Juventas/Power supply unit (computer)

An ATX12V revision 1.3 power supply
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.

Desktops

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An installed power supply (top right) with internal power wires connected to components

Common attributes

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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

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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.

Form factors

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Form Factor Introduction Creator Motherboard Connectors Design Power (W) Outer Face (mm)
PC 1981 IBM two 6-pin 63.5-130 100 × 222
AT 1984 IBM two 6-pin 192 150 × 213
Baby AT 1985 IBM two 6-pin 150 × 165
LPX Western Digital two 6-pin 86 × 150
ATX 1995 Intel 20-pin 160–300 86 × 150
SFX 1997 Intel 20-pin[note 1] 135 63.5 × 100
ATX12V 2000 Intel 20/24-pin + 4-pin[note 2] 180–450 86 × 150
SFX12V 2001 Intel 20/24-pin + 4-pin 180–300 63.5 × 100
TFX12V 2002 Intel 20/24-pin + 4-pin 180–300 65 × 85
CFX12V 2003 Intel 24-pin + 4-pin 180–300 86 × 150
LFX12V 2004 Intel 24-pin + 4-pin 180–270 62 × 72
Flex ATX[note 3] 2007 Intel 24-pin + 4-pin 180–270 40.5 × 81.5
  1. ^ An optional 6-pin connector is specified for fan control.
  2. ^ For revisions prior to 2.0, an additional 6-pin connector is specified for high power designs.
  3. ^ Not part of the FlexATX motherboard form factor introduced in 1999.

Internal connectors

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Main article: List of computer power connectors
Common names Pin Arrangement Uses Part Numbers
AT, motherboard two 1 × 6 PC, XT, AT, Baby AT, and LPX motherboards Molex 90331-0001
ATX, motherboard, main, 20-pin 2 × 10 ATX and later motherboards Molex 39-01-2200
SFX 2 × 3 optional fan control Molex 39-01-2060
+12V, P4, 4-pin 2 × 2 ATX12V and later motherboards Molex 39-01-2040
aux 1 × 6 motherboards requiring ATX12V between 1.0 and 1.3
ATX12V2, motherboard, main, 24-pin 2 × 12 motherboards requiring ATX12V 2.0 or similar Molex 39-01-2240
peripheral, molex, drive, 4-pin 1 × 4 PATA drives, SCSI drives, 5.25" floppy drives, some fans Molex 15-24-4048
floppy, berg 1 × 4 3.5" floppy drives, miscellaneous devices Tyco 171822-4
SATA, serial ATA 1 × 15 SATA drives Molex 67582-0000
PCIe, 6-pin 2 × 3 some PCIe video cards
PCIe, 8-pin 2 × 4 some PCIe video cards

Workstations and servers

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A redundant power supply

Comparison to desktops

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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.

Form factors

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Form Factor Introduction Creator Motherboard Connectors Design Power (W) Exterior Face (mm)
WTX (single fan) 1998 Intel 24-pin + 22-pin + 8-pin 350–500 86 × 150
WTX (dual fan) 1998 Intel 24-pin + 22-pin + 8-pin + two 6-pin 500–850 86 × 224
EPS12V 2000 SSI 24-pin + 8-pin[note 1] 400–700 86 × 150
EPS2U 2000 SSI 24-pin + 8-pin[note 1] 400–700 82.2 × 106
ERP2U 2000 SSI 24-pin + 8-pin[note 1] 350–700 83 × 108
EPS1U 2001 SSI 62-pin 125–500 40 × 106
GES 2002 AMD 24-pin + 8-pin
ERP12V SSI
  1. ^ a b c An optional 5-pin connector is specified for SMBus data.

Laptops and netbooks

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A laptop power supply with power cord attached

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

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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.

Certification

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A label from an ATX12V power supply with various certification marks (bottom right)
      • only 80plus is unique

Safety

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Environmental

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Efficiency

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See also

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{{Basic computer components}} [[Category:Power supplies]] [[Category:Computer hardware]]

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