Power Supply & SMPS

Techopedia explains Power Supply

Most computer power supplies also have an input voltage switch, which can be set to 110v/115v or 220v/240v, depending on the geographic location. This switch position is crucial because of the different power voltages supplied by power outlets in different countries.

Most computers now use a switched-mode power supply, which changes AC current to DC voltage. This voltage can be switched on and off electronically. A switched- mode power supply can also shut itself down before damage is done when a short is detected.

Most computer power supplies include a number of switched-mode supplies, which operate independently by producing a single voltage. These are linked together so that they shut down as a group in case of a computer fault.

Techopedia explains Switched-Mode Power Supply (SMPS)

Switched-mode power supplies are classified according to the type of input and output voltages. The four major categories are:

  • AC to DC
  • DC to DC
  • DC to AC
  • AC to AC

A basic isolated AC to DC switched-mode power supply consists of:

  • Input rectifier and filter
  • Inverter consisting of switching devices such as MOSFETs
  • Transformer
  • Output rectifier and filter
  • Feedback and control circuit

The input DC supply from a rectifier or battery is fed to the inverter where it is turned on and off at high frequencies of between 20 KHz and 200 KHz by the switching MOSFET or power transistors. The high-frequency voltage pulses from the inverter are fed to the transformer primary winding, and the secondary AC output is rectified and smoothed to produce the required DC voltages. A feedback circuit monitors the output voltage and instructs the control circuit to adjust the duty cycle to maintain the output at the desired level.

There are different circuit configurations known as topologies, each having unique characteristics, advantages, and modes of operation, which determines how the input power is transferred to the output.

Most of the commonly used topologies such as flyback, push-pull, half bridge and full bridge, consisting of a transformer to provide isolation, voltage scaling, and multiple output voltages. The non-isolated configurations do not have a transformer and the power conversion is provided by the inductive energy transfer.

Advantages of switched-mode power supplies:

  • Higher efficiency of 68% to 90%
  • Regulated and reliable outputs regardless of variations in input supply voltage
  • Small size and lighter
  • Flexible technology
  • High power density


  • Generates electromagnetic interference
  • Complex circuit design
  • Expensive compared to linear supplies

Switched-mode power supplies are used to power a wide variety of equipment such as computers, sensitive electronics, battery-operated devices and other equipment requiring high efficiency.

1)AC to DC solutions Output Dc Ranges 5v-1amp to 10 Amp,12v-1Amp to 10 Amps,24v-1mp to 10Amps.

2)DC to DC solutions