The PC power supply is the core power-holding component installed inside the computer case, and can be regarded as the "power heart" of the computer. It is mainly responsible for converting the alternating current from the mains power supply into the direct current required by the computer hardware. It is a device specifically designed to supply power to the internal components of the case, such as the motherboard, drives, graphics cards, etc. Most PC power supplies are of the switch-mode type. 

It will convert the 220V alternating current from the mains power supply into different low-voltage direct currents such as +12V, +5V, +3.3V, etc., and then distribute them to the CPU, graphics card, motherboard, memory, hard drive and other computer components, providing stable and specification-compliant power support for these hardware. Currently, most PC power supplies on the market are of the switching type, equipped with protection functions such as overvoltage, overcurrent and overheating, which can effectively prevent hardware from being damaged due to abnormal power supply. 

According to different specifications and usage scenarios, PC power supplies are also divided into various types. Common ones include ATX, BTX, EPS, SFX, etc. Among them, ATX is the mainstream standard for home computers, with a size of 150x140x86mm, while SFX is suitable for small cases and has a size of 125x100x63.5mm. 

The power supply of a PC has a protective circuit. The protective circuit inside the power supply monitors every action of the power supply and is the brain of the power supply. It is responsible for starting the power supply and monitoring and adjusting the voltage/current. At the same time, it automatically provides protection in case of short circuit, open circuit, overvoltage, overcurrent, undervoltage, or undercurrent. Poor-quality power supplies usually simplify this part of the circuit or even do not set a protective circuit at all, and all of these will bring many hidden dangers to the PC system. In addition, high-quality power supplies usually also have output short-circuit protection. This is a very practical function. 

In the circuit part of the PC power supply, in the 3C certification that is mandatory in the country, it is required that a power factor correction circuit must be added inside the power supply to reduce the interference of the switching power supply to the external power grid. This is the PFC circuit that is currently present inside the power supply. Therefore, the latest power supplies that have passed the national CCC certification all have a new component - the PFC circuit. Through the disassembly of dozens of power supplies, it is found that this component is larger than the switching transformer, and it looks very similar to the switching transformer. It is also encapsulated with yellow tape. It is smaller in size but the power factor can be close to one, and the effect is very excellent. 

The heat dissipation part of the PC power supply. The conversion efficiency of the computer power supply is usually between 70% and 80%, which means that 20% to 30% of the energy will be converted into heat. This heat accumulates in the power supply and cannot be promptly dissipated, causing the local temperature of the power supply to be too high, thereby causing unnecessary damage to the power supply. Therefore, any power supply contains a heat dissipation device, and the fan's air intake volume and noise index are also two important indicators of the power supply. Power supply heat dissipation is mainly carried out through the cooperation of heat sinks and power tubes. When we look into the gap, we can see huge heat sinks inside the power supply, and the performance and limit parameters of the large power tubes directly affect the safe carrying power and product cost of the power supply, and are also closely related to the size of the power supply's margin. Therefore, observing the heat sinks and the power tubes on them is also a method to judge whether a power supply is good or not. 

The function of a PC power supply is to convert alternating current into direct current and provide stable and reliable power to all the components inside the computer.