What is SMPS? and its Voltage Used

SMPS ( Switch Mode Power Supply)

SMPS is Switching Power Supply , Which Provide Regulated DC Voltage to Motherboard , Hard Disk, DVD Writer etc.

There are two type of SMPS

1-AT (Advanced Technology): This Power Supply has 12 pin and 6,6 pin Two Connector. It is used old Motherboard like  P1, P2 and P3.

2-ATX (Advanced Technology Extended): This Power Supply has 20 or 20+4 pin .It is used new Motherboard like P4, Dual Core (DC), Core 2 Duo (C2D), Core 2 Quad (C2Q) and Core i3, i5, i7.

Different between AT and ATX:

AT

(6+6) Two power connector.

3.3v Absent

Motherboard sensing circuit absent Automatic shutdown not available Less weight

Less Impair

 ATX

20 or 20+4 Pin power connector

3.3v Available

Mother board sensing circuit available Automatic shutdown available

More weight More impair

ATX 20 pin Connector Pin detail

NOTE:

PS_ON activated by pressing and releasing the power button while the power supply is in standby mode.

Activating /PS_ON turns on the power supply.

Pin 9 (standby) supply 5V even when PSU is turned off. Pin 14 goes from 0 to 3.7 when PSU switch is turned on.

Shorting pin 14 (/PS_ON) to GND (COM) causes power supply to switch ON and PWR_OK to change to +5V.