[Explanation] What is a switching power supply? You can easily understand the switching power supply!


Electronic components mounted on switching power supplies

Many electronic components are used in switching power supplies. Even if you cannot design a circuit, you can understand the power supply circuit block if you understand the part names and roles.

The explanation is based on the electronic components mounted on the 100W board-type power supply.



  • Bridge diode (rectifier diode): A module that packages four diodes into one to convert AC waveform to DC full-wave rectification.
  • Varistor: Used to protect elements such as ICs from static electricity and lightning surges by utilizing the characteristic that the resistance value changes depending on the voltage.
  • Ceramic capacitor (capacitor): An electronic component that stores and discharges electricity (electric charge).
  • X-capacitor (capacitor): It is a role to reduce the normal mode noise of the noise terminal voltage by connecting between the phases (between lines) of the power supply line and short-circuiting the lines at high frequency.
  • Choke coil (inductor): Selects and removes only the common mode component that is the source of radiation noise.
  • MOSFET: Abbreviation for Metal-Oxide-Semiconductor Field Effect Transistor, which translates as “metal oxide semiconductor field effect transistor”. The voltage is controlled by switching with this MOSFET.


  • Photocoupler: An IC package containing an LED and a light receiving element (photodiode). When a current is passed through the LED, the light receiving element turns on. The LED and the light receiving element are electrically insulated.



Example of using a switching power supply

VPN router

 It is a VPN router installed for corporate security measures. It is used in an air-conditioned server room with little dust. A single output board type power supply of about 75W is used as the power supply. No L sheet metal and cover are required to fit in the device case. Previously, it was divided into overseas and domestic, but recently the price difference between the AC100V dedicated input power supply and the AC100 / 200V wide input has become smaller, so the overseas and domestic are common.


control panel

 An electric control panel used to control machines and equipment in factories, buildings, and condominiums. The power supply has a 24V output and is often used by fitting it on a DIN rail. Recently, those with a communication function have also been released.



Platform door

The Ministry of Land, Infrastructure, Transport and Tourism has been actively promoting the introduction to each railway company for about 10 years, and it has become commonplace. It is very effective in preventing accidents where people with poor eyesight accidentally fall onto the railroad tracks. The platform door is divided into a control unit and a sensor unit. The control unit uses a 5V / 24V output that operates the control board and motor, and the sensor unit uses a power supply of about 50 to 150W with a 12V output. There is a lot of dust such as vibration and iron powder, and the environment is not good.


FA machine tool

It is in operation at many factories such as CNC lathes (computer control), machining centers (automatic tool change function), and laser machining machines. Since it may be operated for 24 hours and the line stops when the equipment stops, the performance and reliability of the power supply are more important than the price. The power supply used here is often a unit type 5V or 24V single output power supply.


CT scan

It is installed in the laboratory of a hospital, and the operating time is short, and the environmental conditions of the power supply are very good. The power supply uses a 24V output power supply for driving the motor. The installation space for the power supply is small, and we have devised ways to distribute the power supply of about 600W.



FA robot

Abenomics deregulation a few years ago made it possible to operate a robot next to a worker (Cobot) if regulations such as motor capacity were met. The movement of the human arm in the board assembly process of an electric / electronic manufacturer can be substituted for the horizontal movement of the “double-arm robot”. The robot’s arm is made of soft vinyl chloride, and when a person touches it, the sensor automatically stops it. Due to labor shortages, various types of products are being sold by each robot manufacturer.




Dialysis machine

The environmental conditions are very good as it is used in an air-conditioned hospital room. The power supply uses a multi-output power supply that has acquired the IEC medical standard. The capacity is about 600W, and insulation and low leakage current are required. In addition, the power supply cannot be changed because the entire device has acquired medical standards.


LED sign

LED signboards are sometimes used outdoors, so waterproof and dustproof properties are essential for the power supply. A power supply that has acquired the IP standard and is PSE certified is used. In addition, the environmental conditions are extremely harsh because the signboard is exposed to direct sunlight and the temperature inside the signboard rises. Depending on the type of LED module, both constant current power supply and constant voltage power supply are used as the power supply.



Stadium large-scale vision

These days, it is a large-scale vision installed in most baseball stadiums and stadiums. Since thousands of LED modules are arranged side by side, LED color matching is the most important factor. Domestic LED manufacturers with little variation in LED Vf values are often used, and one power supply is installed in each LED module.



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