Detailed analysis of computer power supply selection skills

　　The computer power supply is the power station of the computer. Some unscrupulous merchants will buy cheap power supplies to reduce the cost of the chassis. The price difference of just a few dozen yuan may result in a loss of thousands of yuan, so when purchasing a machine, you should pay special attention to whether the quality of the computer power supply is good.

　　Some understanding of power safety:

　　Generally, regular manufacturers have passed the certification of some safety certification agencies. China's safety certification agency CCEE mainly includes creepage distance requirements , dielectric strength requirements , leakage current requirements, temperature, and electronic interference requirements.

　　The creepage distance requirement refers to the shortest distance between two conductive components or between a conductive component and the device interface measured along the insulation surface.

　　The dielectric strength requirement means that when there is zero voltage between the AC input lines and between the AC input and the casing and the voltage is applied to AC 1500 volts and DC 2200 volts, the quality is qualified if there is no breakdown or arcing.

　　The leakage voltage requirement means that the leakage current of the switching power supply should not exceed 3.5mA at 260V AC input.

　　The temperature requirement means that the internal temperature rise of the chassis power supply should not exceed 65°C.

　　Electronic interference is divided into conducted interference and radiated interference. Conducted interference is transmitted through power lines with a frequency below 30 MHz. It mainly interferes with the audio band. For example, when the power is turned on, nearby televisions, stereos and other household appliances may not work properly. This is the impact of conducted interference. Radiated interference does not have a big impact on the computer host itself due to the shielding effect of the power cover.

　　The actual operation process of purchasing chassis power supply

You can start from the following points:

　　1. Appearance inspection. Since the heat sink plays a huge role in the chassis power supply and affects the efficiency and life of the entire chassis power supply, you should carefully check whether the heat sink of the power supply is large enough. Another point is to check whether the power cable is thick enough, because the output current of the power supply is generally large, and a small resistance value will produce a large voltage drop loss. Good quality power cables are thicker and the quality of the cables is better.

　　2. Check the heat sink material. From the heat sink point of view, good quality brand power supplies generally use aluminum or copper heat sinks, and the heat sinks are large and thick. Although inferior power supplies also use aluminum or copper materials, the heat sinks are small and thin, and sometimes even iron sheets are used as heat sinks. Generally speaking, these are counterfeit and shoddy products.

　　3. Do some simple tests. The first method is to simply test the load voltage drop. Power supplies with smaller voltage drop have better quality. But during the test, you must not do it at +12 volts or -12 volts to avoid burning the power supply. The second method is to touch the power supply shell with your hand when the power supply is not connected to the ground wire (no danger). There should be a numb feeling of electric shock. This is because there is about 110 volts AC voltage on the shell of the power supply after it is powered on. The third method is to listen to the sound of the power supply fan. When the power supply is running at no load, the running sound of the fan is small and uniform (the fan sound increases after the load is connected).

　　4. If possible, open the power supply box, you can find that a good quality power supply uses exquisite materials, such as the use of square GBB capacitors in many places, the input filter capacitance value is generally greater than 470 microfarads, the output filter capacitance value is also relatively large, and there are more internal inductor and capacitor filter network circuits, and there are complete overvoltage and current limiting protection components. At the same time, the circuit board is clearly printed and the wiring is neat.

　　Judging from the feedback from the market, the sales of famous brand power supplies are generally good, such as Great Wall, Galaxy, Parkson, Shunxin, etc. But it is worth noting that there are many imitations and counterfeits of famous brand power supplies, and of course there are many unscrupulous merchants, so when we buy, we must not only open our eyes, but also keep a vigilant heart.