The basic principle and structure of switching power supply

　　"Power Supply (PSU)" is actually the abbreviation of "Power Supply Unit". The often mentioned "PC power supply" is actually also an abbreviation. Strictly speaking, "PC power supply" should be called "switching power supply used in PC host". Of course, such a name is too troublesome, so in the following paragraphs, the shortest name "power supply" will be used.

　　For computers, the power supply is an important component. It is the "heart" of the computer, providing long-lasting and stable power support for the CPU, graphics card, hard disk, and other hardware parts, ensuring that we can use the computer normally to perform various tasks. Therefore, if the power supply does not work properly or is damaged, other hardware in the computer will also be affected, and it is likely to cause more serious losses.

　　Therefore, generally speaking, you should buy a good and genuine power supply first, and then choose other hardware configurations. However, most people do the opposite, often choosing other hardware first, and then using the last few dollars to buy a power supply.

　　If you are in the situation just described, we sincerely recommend that you read this article first, because it will be very helpful for you to choose a power supply product, and it may also change your attitude towards "power supply", and let you know how important a role "power supply" plays in a computer.

　　All power supplies currently used in computers can be called "switching power conversion", or "SPC" in English. The principle of switching power supply is actually quite simple, which is to divide the energy obtained from the national power grid into small high-frequency energy packets, and then transfer them through electrical components such as capacitors and inductors. In the end, all the small energy packets are concentrated and integrated together, so that the corrected energy can be smoothly output. Therefore, compared with other power supply forms, switching power supply is smaller and more efficient.

　　Compared with linear power supplies, switching power supplies have two main advantages. Switching power supplies use a completely different design from linear power supplies, so the size and weight of the power supply are greatly reduced, and the power conversion efficiency can easily exceed 90%.

　　On the other hand, the most obvious defect of the switching power supply is that due to the complexity of the switching power supply itself, a large amount of electromagnetic radiation will be generated. Therefore, the current switching power supplies are equipped with EMI filters or RFI shielding.

　　●EMI transient filter (EMI/Transient Filter): Suppresses EMI/RFI during current entry and input, and plays a role in voltage surge peak protection.

　　●Bridge Rectifier: Rectifies the input AC power into DC power.

　　● Active PFC (APFC): Controls the current of the input power supply so that the current waveform becomes proportional to the power supply voltage waveform. (Makes the voltage and current linearly proportional)

　　●Main Switches: Cuts the DC signal into very small high-frequency energy packets.

　　●Transformer: It is independent between the primary side and the secondary side, and reduces the high voltage electricity to low voltage electricity.

　　● Secondary side filtering and rectification (Output Rectifiers & Filters): Filter and rectify the stepped-down DC power.

　　●Protection Circuits: When there is a serious problem with the power supply, the power supply will be turned off in time.

　　●PWM Controller: Periodically adjusts the main switch to maintain a stable output voltage under all loads.

　　●Isolator: Blocks the voltage feedback from the DC output to the PWM control.

　　The part before the transformer in the power circuit is usually called the "primary side", and the part after the transformer is called the "secondary side". Simply put, the primary side is mainly responsible for the high voltage part, and the secondary side is mainly responsible for the low voltage part.