1. SMPS

2. What is an SMPS
A switched-mode power supply (switching-mode power supply, switch-mode power supply)  is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently.
It is a main power supply which supplies power to each and every component of computer or it converts the main power supply 230volts to 12volts, 5volts, 3volts and distribute to all components of computer.

3. SMPSs are of three types. AT SMPS ATX SMPS BTX SMPS
Types of SMPS
SMPSs are of three types. AT SMPS
ATX SMPS
BTX SMPS

4. AT SMPS:
AT stands for Advanced Technology. These are all old SMPSs. They had 12pin power connector, this is called as AT power connector. They were used in Pentium-I, Pentium-MMX, Pentium-II and Pentium-III CPUs.

5. ATX SMPS:
ATX stands for Advanced Technology eXtended. They had 20pin Power connector, this is called as ATX power connector. They were used in Pentium-III, Pentium-IV and AMD CPUs.

6. Interior view of an ATX SMPS
A: input EMI filtering; A: bridge rectifier; B: input filter capacitors; Between B and C: primary side heat sink; C: transformer; Between C and D: secondary side heat sink; D: output filter coil; E: output filter capacitors.   The coil and large yellow capacitor below E are additional input filtering components that are mounted directly on the power input connector and are not part of the main circuit board.

7. BTX SMPS:
BTX stands for Balanced Technology eXtended. They have 24pin Power connector, this is also called as ATX power connector. It has 15pin SATA power connectors. They are used in Dual core, core2duo, Quad core, i3, i5, i7 and latest AMD CPUs.