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

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

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.

Form factors

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	135	63.5 × 100
ATX12V	2000	Intel	20/24-pin + 4-pin	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	2007	Intel	24-pin + 4-pin	180–270	40.5 × 81.5

Internal connectors

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

A redundant power supply

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.

Form factors

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	400–700	86 × 150
EPS2U	2000	SSI	24-pin + 8-pin	400–700	82.2 × 106
ERP2U	2000	SSI	24-pin + 8-pin	350–700	83 × 108
EPS1U	2001	SSI	62-pin	125–500	40 × 106
GES	2002	AMD	24-pin + 8-pin
ERP12V		SSI

Laptops and netbooks

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

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

A label from an ATX12V power supply with various certification marks (bottom right)

• • • only 80plus is unique

Safety

• UL mark
• GS mark
• TÜV
• NEMKO
• SEMKO
• DEMKO
• FIMKO
• CCC
• CSA
• VDE
• GOST R
• BSMI

Environmental

• CE mark
• FCC
• C-tick
• RoHS

Efficiency

• 80 PLUS
• Energy Star

See also

• Green computing
• Power management
• Power supply
• List of manufacturers
• Quiet PC
• Active Power Factor Correction (Active PFC)

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