Switched-mode power supplies – what makes them so popular among the users?

Power supply

How do the switched-mode power supplies work?

Switched-mode power supplies are electronic supplies which incorporate switching regulators to convert electrical power as efficiently as possible. They are very adaptable and offer great value for money.

Switched-mode power supplies are currently one of the most popular standard electronic components on the market. Their work cycle can be divided in seven steps.

  1. Rectification and filtration of the AC main voltage in order to provide an unregulated high voltage DC bus for delivering power to the DC inverter circuit.
  2. Imposition of a high voltage and high frequency AC waveform on the primary transformer by switchable power transistors in the range from 10 to 100 kHz.
  3. Scaling of the AC pulse voltage by the ratio of the number of turns of the transformer to a value matching the required DC output voltage.
  4. Rectification of the secondary AC voltage of the transformer into pulsating DC voltage.
  5. Averaging of the pulsating DC voltage to the continuous DC voltage at the output of the power supply, conducted by the LC output filter.
  6. Comparing of the DC output voltage to the reference value in order to adjust the output power at the designed setting, conducted by the error amplifier.
  7. Converting of the error amplifier signal into a high frequency, pulse width modulated waveform in order to control the switching power transistors, conducted by the modulator circuit.

Power supply

Application of switched-mode power supply

Switched-mode power supply is an electronic supply used in almost all branches of modern technology, regardless of application, device type and the industry. It is most commonly applied in:

  • personal computers,
  • domestic electronic equipment, such as mobile phone chargers,
  • servers,
  • power stations,
  • extra-low-voltage sources for lighting,
  • security systems,
  • railway systems,
  • factories and industries for power,
  • vehicles, where is used to charge batteries,
  • most of the battery operated equipment, especially the ones where there’s a need for high efficiency and small size components.

What are the advantages of switched-mode power supplies over other devices?

There are a lot of advantages of switched-mode power supplies over other devices which could be used to achieve similar goals.

Small size

Switched-mode power supplies are more compact and use smaller transformers than other devices performing similar, or the same, functions. Due to this feature they are frequently used in electronic devices with limited space.

Light weight

Switched-mode power supplies have an advantage over other otherwise comparable devices thanks to their light weight, that allows them to be implemented in equipment where the mass is an issue.


Switched-mode power supplies are characterized by their higher input voltage and synchronous rectification mode, which make the conversion process more efficient.

Power supply


The switched-mode power supply has high power density and is high-performing – its power efficiency balances on the level between 60 and 70 percent.

As for the other advantages of switched-mode power supplies over other devices which could be used to achieve similar goals, the ones that need to be mentioned are:

  • the use of flexible technology,
  • strong anti-interference,
  • wide range of output,
  • less heat production.

All of the features listed caused an immense popularity of the switched-mode power supplies. In the last decade, this type of electronic supplies fully dominated the power supply market, causing it to change its shape from technical, as well as commercial side. Switched-mode power supplies opened the users a door to more efficient, digitized, reliable, and smaller power sources.