Switching power supplies are roughly divided into AC / DC converters and DC / DC converters according to their inputs. They are also called AC / DC power supply and DC / DC power supply, respectively. An AC / DC converter is a device that converts AC (alternating current) to DC (direct current), and a DC / DC converter is a device that converts DC (direct current) to AC (alternating current).

The reason why it is necessary to convert to DC (direct current) is that electricity is distributed from power plants to factories and homes with alternating current (AC) suitable for long-distance transmission, but electronic components operate with direct current (DC). increase. Therefore, it is necessary to convert it to DC (direct current). An AC / DC converter is a device for converting the voltage AC100V / 200V of factory or household outlets into a stable DC voltage.




On the other hand, DC / DC converters are power supplies that convert DC voltage to the same DC voltage, and can be broadly divided into isolated type and non-insulated type. To prevent electric shock and cut noise, the input and output sides of the power supply must be electrically isolated. The isolated DC-DC converter is a type that uses a transformer, and the primary and secondary windings of the transformer are electrically isolated. The non-insulated type is a small type DC-DC converter that does not use a transformer (the output voltage of the non-isolated type is low, so there is no risk of electric shock).

AC / DC power is used to convert AC AC power supplied from home or factory outlets to DC DC power. If there is a distance from the power supply to the load, there are voltage drop and noise issues. Also, in the past, the load voltage was relatively high at 12V, 24V, and 5V, so even if there was a voltage fluctuation, it was not affected much. However, recently, the voltage of the load tends to be as low as 3.3V or 1.2V, and if the distance from the power supply to the load is long, it is easily affected by voltage drop. Therefore, in order to reduce noise and voltage fluctuations as much as possible, a non-isolated DC / DC that temporarily receives a bus voltage such as 24V or 48V of an AC / DC power supply near the load side of electronic components and converts it to the voltage required by the load. The DC converter POL (Point Of Load) is used.