PC Power Supply

Power Supply

Block Diagram of Power Supply

The Power Supply Converts AC to DC and regulates the output voltage to a value required by the load

Advanced Technology Standard

A T Standard

BlackGroundP8-6

BlackGroundP8-5

Blue-12P8-4

Yellow+12P8-3

Red+5P8-2

Orange+5P8-1

Standard Color

VoltagePin

Red+5P9-6

Red+5P9-5

Red+5P9-4

White-5P9-3

BlackGroundP9-2

BlackGroundP9-1

Standard Color

VoltagePin

A T StandardOutput Voltages

ATX Power Supply

Power Supply• A power supply (sometimes known as a power supply unit or 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 most common computer power supply is built to conform with the ATX form factor. This enables different power supplies to be interchangeable with different components inside the computer.

At the motherboardAt the Cable

• The ATX (for Advanced Technology Extended) form factor was created by Intel in 1995. It was the first big change in computer case and motherboard design in many years.

• ATX overtook AT completely as the default form factor for new systems. ATX addressed many of the AT form factor's annoyances that had frustrated system builders.

A T X Connector Standard

AT POWER CONNECTOR

- ATX Power

Supply connector- Typical wattages range

from 200 W to 500 W - There are also other,

smaller connectors, most of

which have four wires:

two black,

one red,

one yellow.

“each black wire is a Ground, the red wire is +5 V, and the yellow wire is +12 V.”

A T X Power Connector

A T X

Yellow+ 1210Purple+ 59Gray+ 58BlackGround7Red+ 56BlackGround5Red+ 5 4BlackGround3Orange+ 3.32Orange+ 3.31

Standard ColorVoltagePin

Red+ 520Red+ 519White- 518BlackGround17BlackGround16BlackGround15GreenPS_On14BlackGround13Blue- 1212Orange+ 3.311

Standard ColorVoltagePin

ATX Motherboard Connectors

At the motherboard At the cable

• In 2003, Intel announced the new BTX standard, intended as a replacement for ATX. BTX (for Balanced Technology Extended) is a form factor for PC motherboards, originally slated to be the replacement for the aging ATX motherboard form factor in late 2004 and early 2005.

B T X Connector Standard

24

pin

MOLEX

39-01-2240 connector at the

power

supply

cable

24

pin

MOLEX

39-01-2240 connector at the

power

supply

cable

At the motherboard

Pin Signal Description1 +3.3 VDC 2 +3.3 VDC 3 COM Ground4 +5 VDC 5 COM Ground6 +5 VDC 7 COM Ground8 PWR_OK Power good - indicate that VDC voltages are in range.9 +5 VSB Standby voltage10 +12 VDC

B T X Connector Pin Designation

Pin Signal Description11 +12 VDC 12 +3.3 VDC 13 +3.3 VDC 14 -12 VDC 15 COM Ground16 PS_ON# Active low. TTL compatible (0.1-0.8V low; 2.0 high?). When low -

DC outputs are enabled. When high - power supply should not deliver DC current.

17 COM Ground18 COM Ground19 COM Ground20 N/C 21 +5 VDC 22 +5 VDC 23 +5 VDC 24 COM Ground

B T X Connector Pin Designation

B T X/ATX/AT HDD and FDD Power Connector Pin Designation

Pin Voltage Color

1 + 12 Yellow

2 Ground Black

3 Ground Black

4 + 5 Red

• Can I fit an ATX mainboard in an AT case? - Not really. An AT case and AT power supply can neither power up nor house a new ATX mainboard. ATX and AT are two different form-factors. The AT case was designed before ATX. Most of the computer cases built before late 1996 were AT form-factor. For over 10 years, from about 1985 to 1997, the AT form-factors, founded by the original IBM PC-AT, provided the standard for 90% of the PC industry. Today, the majority of new systems ATX form-factor. The ATX is also known as the Extended AT form-factor.

Question

Why Weight Matters? The more appropriate question is why size matters.

The weight of a power supply is directly related to the quantity, quality, and size of the material (thus cost) used to build the power supply.

Choosing a Power Supply

• Conclusions

This brief study clearly confirms an empirical knowledge: the quality of a power supply can be estimated by its weight.

- The very simple and easy way for ordinary PC users to estimate and compare the quality of a power supply.

Choosing a Power Supply

Identifying Defective Power Supply(Dead set)

• For AT Power SupplyTurn on the main power switch(mechanical) and measure the

presence of the output voltage (±12V and ± 5V) using a voltmeter. If a voltmeter is not available, just observe the functionality of the cooling fan.

• For ATX and BTX Power Supply Simply short the Ps_On terminal and observe the cooling fan.

If the fan works, the power supply is good. You can measure the output voltage of each terminal and compare the reading to the specified values.

• Replacement of a known good Power Supply is the last approach for confirmation.