Tuesday, July 17, 2007


Power Supply Unit (MPS) is the component that supplies power to a computer. More specifically, a power supply is typically designed to convert 100-120 V (North America and Japan) or 220-240 V (Europe, Asia and Australia) AC power from the mains to usable low-voltage DC power for the internal components of the computer. Some power supplies have a switch to change between 230V and 115V. Other models have automatic sensors that switch input voltage automatically, or are able to accept any voltage between those limits.
The most common computer power supplies are built to conform with the
ATX form factor. The most recent specification of the ATX standard is version 2.2, released in 2004. This enables different power supplies to be interchangeable with different components inside the computer. ATX power supplies also are designed to turn on and off using a signal from the motherboard (PS-ON wire), and provide support for modern functions such as the standby mode available in many computers.
Wattage
Computer power supplies are rated for certain wattages based on their maximum output power. Typical rated wattages range from 200
W to 500 W, although units used by gamers and enthusiasts usually range from 500 W to 800 W, with the highest end units going up to 1.2 kW for extreme performance computers with multiple processors and graphics cards (ATI CrossFire or NVIDIA SLI).
Appearance
External
Most computer power supplies have the appearance of a square metal box, and have a large bundle of wires emerging from one end. A label on one side of the box lists technical information about the power supply, including maximum wattage.
InternalInside the computer power supply is a complex arrangement of electrical components, including
diodes, capacitors and transformers. Also, most computer power supplies have metal heat sinks and fans to dissipate the heat produced. The speed of the fan is often dependent on the temperature, or less often the power load. It may be dangerous to open a power supply even if it is not connected to an electrical outlet, as high voltages may still be present in charged capacitors. However, for most PSU's this can be fixed by unplugging the PSU and then pressing the power-on button, which will drain the capacitors. Still, care should be taken as some PSU's require a load on the output in order to discharge the capacitors fully. Even when the PC is turned off, a PSU will draw some power from the wall, most of it going to power the 5Vsb (standby) rail.

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