SWITCH MODE POWER SUPPLY

A switched-mode power supply or switch-mode power supply or SMPS, is an electronic power supply unit that incorporates a switching regulator that switches power transistors rapidly on and off (typically 40 to 80 thousand times per second) into the primary of a much smaller, more efficient transformer in order to stabilize the output voltage or current. By varying duty cycle, frequency or a relative phase of these transitions average value of output voltage or current is controlled.

 

SMPS converts the input AC voltage to the DC voltages needed by the personal computer. In older computers, AT SMPS were used. Currently ATX 12V SMPS are dominant.

SMPS supplies power to all components of a PC located in the CPU viz. motherboard, hard disk, floppy drive, CD ROM, fans etc. Most computer SMPS's have the appearance of a square metal box. They have a fan installed at one end and a large bundle of wires emerge out from the other end having:

·         One PC Main connector (20 or 24 pins) for power supply to the mother board.

·         4 pin Peripheral connectors for power supply to Hard Disk Drive, CD/DVD Drive etc.

·         One 4 pin floppy connector for power supply to floppy drive.

·         One Serial ATA connector for power supply to SATA devices.

Modern desktop SMPS's produce DC voltages of +/-5V, +3.3V and +/-12V outputs. The DC-DC converters on the motherboard step down SMPS voltage to the CPU core voltage and other low voltages needed for other motherboard components.

Types of SMPS-  SMPS full form is Switching Mode Power Supply. It is a main power supply to power the 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.

1-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.

2-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.

3-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.

SMPS Connectors, voltages and functions-

There are three types of SMPSs. They are AT, ATX, BTX. These three types of SMPSs have different connectors and each wire has different voltages. Here the connectors and its voltages.