What is a Desktop Computer SMPS ?

What is a Desktop Computer SMPS ?

(Switched Mode Power Supply)

Introduction

Computer is an state of art device and made to do numerous tasks like calculations, printing, scanning, document making saving and lots of many more. To perform these tasks computer have lots of electronic parts too. These parts works in a sequence to handle the data or various signals. These devices or components need various voltages at various current levels. To meet their power requirements a desktop computer need various voltages at various current levels.  A desktop computer SMPS ( Switched Mode Power Supply) handles these power requirements. this types of power supply comes in some variants also like 250 Watt, 350 Watts or 450 Watts and so. In this blog we will discus about this power supply.

What is a SMPS ?

SMPS ( Switched Mode Power Supply) is a AC to DC converter that changes the AC 230 VDC to various DC voltages. These voltages are as follow.

          

             +12 Volts

            -12 Volts

             +5 Volts

             -5 Volts

           + 3.3 Volts

            -3.3 Volts

To connect these voltages to computer circuit called computer mother board we have two types of power connector . There are two types of power connector that connects SMPS to motherboard . Both connectors are shown in the picture in following . 

20 pin  connector was used in old PCs and 24 pin connector can be found in almost new PCs . The basic difference can be found in the picture. The incoming voltage of a SMPS is 110-230 VAC, and outputs are discussed earlier. So lets see how a SMPS do his job ?

Circuit diagram shown in the picture is a basic idea of a SMPS . SMPS use PWM signal to for controlling of volateg and current for output. The incoming  power is converted in the DC voltage directly by a bridge rectifier and than filters by a strong dc capacitor . The maximum AC part of the voltage is removed hare . After this DC voltage is switched at controlled speed by the switching circuit and fed it to the SMPS transformer through a powerful transistor. This transformer actually works like an regulator of the outputs . It transformed the  various voltages at his secondary windings. After this step voltages formed filterred and fed to the computer motherboard. On another important circuit take care of the regulation that is feedback circuit . It takes some voltage from the output and feed it to the switching circuit. 

The switching of this circuit depends upon the voltage level of the output. This whole circuit is placed in a metal cabinet. As it is a SMPS power supply so this need a starting trigger to starts it functionality so one trigger wire or power ON wire need ti connect with the ground wire. When we connect this SMPS with the motherboard than PC power switch do this job but when we need to run this power supply without any motherboard than we manually need to start the functionality . The method is shown in the picture below. This is the biggest power connector for motherboard it cannects all the DC power  to the mother board too. 

With this power connector we have another power connector that joins the DC power to the mother board. It is shown in the picture below. 

 Various connector ans their works

  SMPS has various connectors to connect output with the computer peripheral device like HDD ( Hard Disk Drive), ODD (Optical Disk Drive ) . These devices need two dc power as 

+12 VDC-------------Yellow Wire

+5 VDC -------------- Red Wire

Ground----------------- Two Black Wire.

These are the most common output connector that are used  to connect hard disk or a optical drive ( CD or DVD writers etc.

These connector can seen any modern computer that these are power connector for SATA device like Hard Disk or DVD writer etc. The Voltage for these device are same as discuss earlier .

Some we need power converter that connects old type of power connector the modern one. 

one SATA power converter connector is shown in the picture.