. Stands for Switch Mode Power Supply.
    . Used in computer to supply regulated power to all of its components.
    . It provides reliable output irrespective of variation in input voltage for proper functioning of your computer.
    . In laptops, it is generally 19V and in desktops, it is 12V.

    What it contains?

           . Input Rectifier and Filter
           . Inverter
           . Transformer for voltage conversion
           . Output Regulator

         Input Rectifier:

              . AC input from mains is first rectified into DC using Rectifier in SMPS.
              . It uses full wave rectifier to produce unregulated DC output.
              . Using Filter circuit, it removes unwanted signals of high frequency.


              . In the next stage, it inverts the input DC to AC using power oscillator.
              . Output is connected to Transformer to convert the voltage levels.
              . Switching is done through MOSFET Amplifiers.


              . In this stage, output from inverter is step down to get particular voltage level required by the terminals.
              . To each end, if it needs DC as input, the output from the transformer should be rectified.
              . It is filtered using Capacitors.

        Voltage Regulator:

              . In this stage, the voltage will be maintained constant even if there is variation in the input voltage.
              . It supplies this constant voltage to the components.
              . If it doesn't match, it sends the feedback to inverter to send required voltage to the transformer.

    Different Pins from SMPS:

            . It consists of different output power cable to which it is connected to different components.
            . 20/24  Pin ATX: It allows to turn motherboard on. Early models have 20 pin configuration, modern computers have 24 pin. 

            . 4 Pin ATX:  It plugs into motherboard and exclusively powers on the processor.

            . SATA: Modern power systems has 4 of these to power the drives in SATA standard.

            . MOLEX: Commonly used in systems today. Used to power hard disk and other drives.