This document discusses computer power supplies, including different types of power supplies, power supply components, power connectors, and power management standards. It covers linear and switched-mode power supplies, AT and ATX form factors, power supply output voltages, the power good signal, advanced power management (APM), and advanced configuration and power interface (ACPI). It also discusses replacing power supplies and includes links for further reading.

1. Copyright © 2007 Heathkit Company, Inc. All Rights Reserved
PC Fundamentals
Power Supply Unit
+ more

2. 2
Power Supply Unit
AKA:
PSU
Power Supply
Power Unit

3. 3
Power Supply Types
 Linear Power Supply
 Switched-Mode Power Supply (SMPS)
o More:
o http://en.wikipedia.org/wiki/Switched-mode_power_supply
 Pros. Cons. and Comparison
o http://en.wikipedia.org/wiki/Switched-
mode_power_supply#Advantages_and_disadvantages

4. 4
The Power Supply.

5. 5
The Power Supply
FAN
AC Receptacle
On/Off Switch

6. 6
Power Supply Input Voltage
 100 to 125 VAC @ 60 Hz
 200 to 250VAC @ 50 Hz

7. 7
Motherboard Form Factors
AT-Type
ATX-Type

8. 8
AT Motherboard
12”
13.5”

9. 9
ATX
Motherboard
9.6 ”
12 ”

10. 10
ATX
Mother-
board

11. AT Power Distribution

12. 12
Power Supply Output Voltages
AT-Type
+5 Volts
+12 Volts
–12 Volts
–5 Volts

13. 13
Power Connector

14. 14
P9P8
Black
Wires
Motherboard Power Connectors

15. Some connectors are held in place
by a latch.
Latch

16. 16
P9
Ground
Ground
+5V
+5V
+5V-5V

17. 17
P8
-12V+12V
Ground
Ground+5V
Power Good

18. ATX Power Distribution

19. 19
Power Supply Output Voltages
ATX-Type
+5 Volts
+12 Volts
–12 Volts
–5 Volts
+3.3 Volts

20. 20
ATX Motherboard
Power Connector

21. 21
20-Pin Power
Connector

22. 22
24-Pin Power
Connector

23. 23
2 X 10 ATX Connector
2 X 2
Connector

24. 24

25. Edge View of Motherboard.

26. 26
A Second 2 X 2
Motherboard Power
Connector Supplies
Processor Core Power
(+12 Volts)

27. 27

28. 28

29. 29
The Power Good Signal
 +5 Volt signal generated by the power
supply.
 It indicates that the power supply has
passed its self test and that its output
voltages have stabilized.
 Usually occurs within first 0.5 seconds.
 Prevents the system from running under
bad or unstable power conditions.

30. Large Molex Connector

31. 31
+5V
+12V
Ground
4-Pin Molex
Connector

32. Berg Connector

33. 33
+5V
+12V
Ground
4-Pin Berg
Connector

34. 34
Grasp the
connector
by the
shell…
Never by
the leads.

35. 35
Power Management
 Hardware Power Management
 Software Power Management

36. 36
Advanced Power Management (APM)
 Eenables the operating system to work with
the BIOS to achieve power management.
 Replaced by ACPI
 Microsoft dropped support for APM in
Windows Vista
More:
http://en.wikipedia.org/wiki/Advanced_power_management

37. 37
Advanced Configuration and Power
Interface (ACPI)
 Successor of APM
 An open standard for device configuration and power
management by the operating system
 ACPI defines platform-independent interfaces for
hardware discovery, configuration, power management
and monitoring.
 The specification is central to Operating System-directed
configuration and Power Management (OSPM), a
system implementing ACPI, which removes device
management responsibilities from legacy firmware
interfaces

38. 38
APM vs. ACPI
 APM vs. ACPI
–http://www.thinkwiki.org/wiki/APM_vs._ACPI
 Difference Between APM and ACPI
– ACPIhttp://www.differencebetween.net/technology/software-
technology/difference-between-apm-and-acpi/
ACPI
http://en.wikipedia.org/wiki/Advanced_Configuration_and_
Power_Interface

39. 39
Power Saving Modes
 Blank (Black) Screen Saver
 Display Off
Sleep
 Hibernate
Power States
http://en.wikipedia.org/wiki/Advanced_Configuration_and_
Power_Interface#Power_states
Hybrid Sleep

40. 40
 Blank Screen Saver

41. 41
 Display Off and Sleep

42. 42
Hybrid Sleep
– http://en.wikipedia.org/wiki/Sleep_mode#Hybrid_sleep
– Sleep and Hibernation: FAQ
 http://windows.microsoft.com/en-sg/windows7/sleep-
and-hibernation-frequently-asked-questions
Sleep (AKA: Stand By, Suspend)

43. 43
Replacing the Power Supply

44. 44
Disconnect the
AC Power Cord.

45. 45
On-Off
Switch

46. 46

47. 47
Power to
Motherboard

48. 48
The Power Supply
is held in place
by four screws.

49. 49
Power
Supply

50. 50
Reinstall the power supply.

51. 51
Links and References
 www.google.lk
o https://www.google.com/search?q=Power+Supply+Unit
 www.duckduckgo.com
o https://duckduckgo.com/?q=Computer+Power+Supply
 www.wikipedia.org
o http://en.wikipedia.org/wiki/Power_supply_unit_(computer)

52. Copyright © 2007 Heathkit Company, Inc. All Rights Reserved
PC Fundamentals
End