The term power supply is a bit of a misnomer. Allow me to illustrate my arguments with the following:
Deep Well >> Water Pump >> Pressurized water Tank>>Gate valve >> Pipe >> Faucet
Now, Let the items i.e. water tank, Gate valve, pipe and faucet be a one (1) process called A_unit and let the Water pump be an action or a connector of the two (Deep well & A_Unit).
Now, which of the two units (Deep well and A_unit) supplies/provides water to the household to drink? When I say supplier/provider - that means without it there would be totally no water at all.
From the illustration above, without “A_unit” - Your household would be a mess.
The same with PSU, without PSU - your system will be toasted due to improper voltage supply (a mess in water illustration above) thus, PSU does not supply power but controls and regulates the power supply to avoid the mess.
A PC’s power supply does not actually supply any power. Just as with any electrical appliance, the power for a PC is supplied by the wall socket, which is connected to your local electrical grid., which is supplied electricity by a power company. What the power supply in a PC actually does is act as a step-down transformer. That means that it converts high-voltage alternating current into low-voltage direct current. Generally, a PC uses 12-volt current to power motors on devices like hard drives and CD-ROM drives, and 5-volt and 3.3-volt current to support onboard electronics.
Source (From my Blog site)
Edited by SHENGTON, 03 July 2009 - 08:13 PM.