Power Supply
Power supply - Internet URL
http://www.pcguide.com/ref/power/sup/index.htm
Purpose of the Power
Supply
• Convert household power into a form the
computer can use.
• Provides power to every device in the
computer.
• The Power Supply converts AC (alternating
current) which is external power to DC (direct
current) internal power that the computer can
use.
• Link to AC/DC Voltage Conversion Information
• How Computer Work Video (Old Version) –
video clip on the power supply.
Roles of the Power Supply
Link to the Role of the Power Supply
• Stability – provides sufficient power to PC.
• Cooling - The power supply contains the main
fan that controls the flow of air through the PC
case.
• Energy Efficiency - Newer PC power supplies
work with components to reduce the amount
of power they consume when idle.
• Expandability - The capacity of your power
supply is one factor that will determine your
ability to add new drives to your system
• A power supply is responsible for 28% of
Household Power &
Problems
• Household Power – the external power source
that comes into the wall.
• Power Problems that may lead to power
supply problems.
– Line Noise
– Surges
– Lightening strikes
– Brownouts
– Blackouts
• Link to Household Power and Problems
Line Noise
• Line Noise - Line noise
consists of small
variations in the voltage
level delivered to the
computer. Noise that
the power supply
cannot handle can
cause it to malfunction
and pass the problem
on to your motherboard
or other internal devices
Surges
• This is a temporary increase of voltage
that can last just a few thousandths of a
second, but in this time the voltage can
increase from 110 to 1,000 volts or even
higher.
• Voltage surges can disrupt or even
damage your computer equipment
Lightening Strike
• Enormous amount of electricity involved
in a storm, a strike near your PC--near
meaning within several miles--can
induce currents in metal objects.
• Any wire that comes in from the outside
and attaches to your PC can become a
conduit for a pulse of destructive energy
such as a telephone line or power cord.
Brownout and Blackout
• Brownout - when a brownout occurs, the
voltage drops from its normal level to a
lower voltage and then returns; in some
ways, it's like the opposite of a surge.
• Blackout - A blackout, of course, is when
the power totally fails.
Basic Electricity
Link to Electrical Basics
• This is an excellent site to link students
to the basics of electricity. This may be
to in depth for the IT Essentials Class. I
did not add this information to the
student worksheet. I added this page in
case instructors would like to teach
additional information about electricity
related to the power supply.
Parts of the Power Supply
Internal Power
Parts of the Power Supply
• Power supplies generate high voltages internally
and can be dangerous.
• Unless you have been specifically trained to work
inside power supplies, you should not open one.
Power Supply Specs
Input Voltages and Tolerances
• Input Voltage Range – acceptable range
of input – 85v-135v AC or 170v-270v AC
• Output Rating (Watts) – output of power
measured in watts
Link to
Calculating Watts
Power Switch
• Power switches to the power supply have
changed over time.
• Older PC/XT form factor– computer was turned
on by a switch in the back of the computer.
• AT form factor – added a remote switch on the
front of the computer connected to the power
supply in the back.
• ATX/NLX form factor – uses an electric switch
connected to the motherboard that uses a
feature called Soft_Power to turn on the
Voltage Selector Switch
• Normally dual
voltage selector to
be set at either
110/220v.
• 110 – Normal
voltage setting
• 220 – For settings
out of the U.S.
• If a 110v is set to
220v damage can
occur.
Motherboard Connector
• Most important
connection.
• Supplies power to
other devices
through the
motherboard.
• Wires are made of
copper.
ATX 20
pin
Older P8 & P9
Or P1 & P2
Motherboard
Connectors
• Colors are used to depict the about of
voltage each wire may carry. (Most but
not all manufactures follow it.)
• The P8 and P9 must be inserted correctly or
the motherboard could be ruined. (Black to
Black your motherboards back, red to red
your motherboards dead.)
• Power supply motherboard connectors are
based on the form factor of the motherboard.
Motherboard Connector
Voltages
P8
ATX
Style
P9
Drive Connectors
• The power supply provides power to internal
hard disk, floppy disk, CD/DVD and other drives
directly, through four-wire connectors that are
designed to attach to the rear of each drive
• The number of connectors that come with a
system may vary.
• There is a specific smaller floppy drive
connector.
• Multiple larger four pin connectors may be used
on hard drives, CD-ROMS, and DVD.
• A Y-Connector may add flexibility to drive
connectors but is not recommended.
Drive connectors
Hard drive
CD-ROM
Floppy drive
Power Supply Fan
• Primary cooling source for the entire
PC.
• Power supply fans may be made of
different components and move
different levels of air.
• The fan is usually the first piece of the
power supply to fail because of dirt in
the air.
• Most computers use additional auxiliary
fans to help cool the entire PC.
Additional Hardware Help
• Sysopt.com
• tomshardware.com
• cnet.com