A power
supply is an electrical device that supplies electric power to an electrical
load. The primary function of a power supply is to convert electric current
from a source to the correct voltage, current, and frequency to power the load.
As a result, power supplies are sometimes referred to as electric power
converters. Some power supplies are separate standalone pieces of equipment,
while others are built into the load appliances that they power. Examples of
the latter include power supplies found in desktop computers and consumer
electronics devices. Other functions that power supplies may perform include
limiting the current drawn by the load to safe levels, shutting off the current
in the event of an electrical fault, power conditioning to prevent electronic
noise or voltage surges on the input from reaching the load, power-factor
correction, and storing energy so it can continue to power the load in the
event of a temporary interruption in the source power (uninterruptible power
supply).