fig:- working principle of SMPS
fig :- SMPS of computer
From the above figure, we came to know that the function of SMPS in computer which is to convert the high 220V-AC to 0-12V DC.SMPS contain several color of wires which carry the different voltage to the different parts of the computer.The following table shows the different color cables and its carrying voltage.
Step of checking SMPS
- Plug in AC at input of SMPS
- check +5V SB in Purple wire at the output of SMPS
- If +5V is ok then standBy section of SMPS is considered ok. If +5V is not present then the power supply is faulty.
- Also green wire have 5V power supply for power switch ON purpose.
- Now to start SMPS manually short any Black and Green wire.
- SMPS will start & out 3.3V in orange,5V in red & 12V in yellow wires.
- Check all the voltages ,if all are present then power is ok.
- Sometime the vo;tage may be less than its rated value.If measure value are for difference then rated then also power supply may not work.
Output connections of SMPS
- ATX Power connector(20/24 pins)
-It suppilies the voltage to all the section of Motherboard except CPU.eg, RAM,ROM,South Bridge,North Bridge etc.
-It has all types of voltages 3.3,5,12,-12,-5,ps-ON etc.
-If these connector is faulty or not eonnect to the motherboard then the computer will not start.
- ATX 12V connecter:-
-It supply the voltage only to CPU.It supplies only 12V so it is also called 12V connector
- Molex connector:-
It is used to supply voltage to the CD/DVD or Hard disk. Molex connector have different pins.
a> PATA
[ Parellel Advanced Technology Attachment]
It has 4 pins through which it supplies 5V & 12V.
b> SATA
[Serial Advanced Technology Attacchment]
It has 12 to 15pins & it supplies some voltage as PATA but some SATA connectors 3.3V is also provided.
c> Berg connector:-
It is used to supply voltage to floppy drive.It has also 5-12V.