Thursday, 27 December 2012

Power supply

A power supply(sometimes known as a  power supply unitor PSU) is a device or system
that supplies electrical or other types of energy to an output load or group of loads. The term is most
commonly applied to electrical energy supplies.
The complete range of power supplies is very broad, and could be considered to include all
forms of energy conversion from one form into another. Conventionally though, the term is usually
confined to electrical or mechanical energy supplies. Constraints that commonly affect power
supplies are the amount of power they can supply, how long they can supply it for without needing
some kind of refueling or recharging, how stable their output voltage or current is under varying
load conditions, and whether they provide continuous power or pulses.
The voltage regulation of power supplies is done by incorporating circuitry to tightly control
the output voltage and/or current of the power supply to a specific value. The specific value is
closely maintained despite variations in the load presented to the power supply's output, or any
reasonable voltage variation at the power supply's input.


A "wall wart" style variable DC power supply with its cover removed. Simpler AC supplies
have nothing inside the case except the transformer.
This term covers the mains power distribution system together with any other primary or
secondary sources of energy such as:
•  Conversion of one form of electrical power to another desired form and  voltage. This
typically involves converting 120 or 240 volt AC supplied by a utility company (see electricity
generation) to a well-regulated lower voltage DC for electronic devices. For examples, see
switched-mode power supply, linear regulator, rectifier and inverter (electrical).
•  Batteries
•  Chemical fuel cells and other forms of energy storage systems
•  Solar power
•  Generators or alternators (particularly useful in vehicles of  all shapes and sizes, where the
engine has rotational power to spare, or in semi-portable units  containing an internal combustion
engine and a generator) (For large-scale power supplies, see  electricity generation.) Low voltage,
low power DC power supply units are commonly integrated with the devices they supply, such as
computers and household electronics.

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