Computer Power Supply Buying Guide

Many people choose to assemble the circuit by themselves. When choosing a power supply, we must first understand some relevant technical indicators, otherwise we may be cheated without knowing it. Generally, the certification mark will be affixed to the inside of the power supply box (the side where the interface line is connected), and some technical indicators will be affixed to the outside of the power supply box. When purchasing, you must carefully read the mark. The following are some common certifications and technical indicators.

Multinational certification marks: High-quality power supplies have certification marks such as FCC, UR of the United States and China Great Wall. These certifications are professional standards for power supplies formulated by certification agencies based on technical specifications in the industry, including production processes, electromagnetic interference, safety protection, etc. Products that meet certain indicators can use certification marks on packaging and product surfaces after applying for certification. It should be said that they have a certain degree of authority.

Noise and filtering: This indicator needs to be directly quantified by professional instruments. It is mainly that 220V AC is converted into various low-voltage DC through filtering and voltage stabilization of the switching power supply. Noise indicates the smoothness of the output DC. The quality of filtering is directly related to the AC component in the output DC, also known as the ripple coefficient. The smaller the coefficient, the better. At the same time, the capacity and quality of the filter capacitor are also related to the stability of the voltage when the current changes greatly.

Instantaneous response capability: When the input voltage changes significantly in an instant (within the allowable range), the time it takes for the output stable voltage value to return to normal is also the power supply's ability to respond to abnormal situations.

Voltage holding time: Backup UPS accounts for a considerable proportion in PC systems. When the power grid suddenly loses power, the backup UPS will switch the power supply. However, this generally takes 2-10ms to switch (depending on the specific performance of the UPS). Therefore, during this period, the power supply itself needs to be able to rely on the power stored in the energy storage element to maintain a short-term power supply. Generally, the holding time of a high-quality power supply can reach 12-18ms, ensuring normal power supply during UPS switching.

Electromagnetic interference: Due to the working principle of the switching power supply, it has strong electromagnetic oscillation inside and has external radiation characteristics similar to radio waves. If it is not shielded, it may affect other devices. If a mobile phone or wireless communication device is placed near a computer, if the communication quality decreases, it means that it is subject to electromagnetic interference. Therefore, there are strict limits on the amount of this harmful radiation in China. The power supply is generally shielded by the outer iron box and chassis, but leakage is inevitable, it is just a matter of quantity. Since this interference is invisible and intangible, and it costs a lot to resist electromagnetic interference, inferior power supplies ignore this indicator. There are FCCA and FCC B standards internationally, and there are national standard A (industrial grade) and national standard B (household appliance grade) standards in China. High-quality power supplies can pass the B standard.

Power-on delay: This is a new concept. It takes a certain amount of time for the power supply to provide stable output after it is turned on. During this period, it is difficult to ensure the stability of voltage. Therefore, the power supply designer delays the power supply by 100ms-500ms and provides high-quality power to the computer only after the power supply stabilizes.

Overvoltage protection: ATX power supplies have an additional 3.3V voltage group compared to traditional AT power supplies. Some motherboards do not have voltage regulators and directly use 3.3V to power some devices on the motherboard. Even if there are circuits with voltage regulators, there is an upper limit on the input voltage. Once the voltage rises, it may cause serious and irreversible physical damage to the powered devices. Therefore, overvoltage protection of the power supply is very important to prevent problems before they happen.

Power efficiency: Power efficiency is closely related to the power design circuit. A high-efficiency power supply can improve the efficiency of electric energy use and, to a certain extent, reduce the power consumption and heat generation of the power supply itself.

Power supply life: Generally, the life of a power supply is calculated based on the possible failure period of the component in 3-5 years, and the average working time is between 80,000 and 100,000 hours.

Given the current popular configuration, 200W power supplies are already stretched to the limit. In order to ensure safer operation of the system, it is very important to leave a margin. So, how to choose a good power supply? In fact, the real price or choice of a good power supply mainly depends on the following factors:

1. Safety specifications: Domestic and foreign industries have strict safety standards in the selection of power supply components, insulation of materials, flame retardancy, etc. For example, the well-known ones abroad are UL, CSA, TUV, CCIB, etc., and the well-known one in China is CCEE (China Electronic Product Quality Certification). If your power supply has these marks, it means that it has passed these certifications. Since the application time for safety specifications is long, there are strict restrictions and requirements, the cost is quite high, and it is subject to regular and irregular supervision and inspection. Once applied, the components and types of the product cannot be changed, replaced or modified at will. If changed, it must be re-verified. Therefore, the starting point of products with safety specifications will be much higher than that of products without safety specifications.

2. Electromagnetic conducted interference specifications: From the perspective of electromagnetic safety, computers must comply with electromagnetic interference standards. Electromagnetic interference to the power grid will have adverse effects on electronic equipment and will also be harmful to human health. The International Organization for Standardization and most countries in the world have established several standards for electromagnetic interference and radio frequency interference. The standards require electronic equipment manufacturers to reduce the radiation and conducted interference of their products to an acceptable level. The most famous one is "FCC CLASS B". It is the electromagnetic interference standard established by the United States for residential environments. At present, there are only a few power supplies in the domestic market that have passed this test and certification, such as: Huntkey, Parkson, and Great Wall.

3. Load change rate: The output of the computer power supply is multi-channel, and each channel has a certain range and specification. When users use it, various deviations may occur due to different needs or configurations. The power supply should ensure that the output is not unstable or exceeds the specified range due to different loads.

4. Other factors: In addition, there are some other factors such as HOLDTIME, line regulation, and various protections that should also be considered. For example, overvoltage, overcurrent, and short circuit protection are basic power protection functions that all power supplies should have. Only when the computer has a complete and reliable protection function can it avoid burning the computer and the power supply itself. Most power supplies on the market have passed this test.

5. Appearance and performance: A good power supply should be well packaged, finely processed, without bumps or scratches, without foreign matter inside the power supply, with a steady fan speed, no dead angles, no obvious noise, with intact seals, and an ecological balance date. The power supply label should have the main performance indicators of the power supply.

If you suspect that overheating or insufficient power is causing a problem with a new system, it is best to check the power supply before calling a technician: unplug all peripherals (including hard disks and floppy disks) and see if the machine can reach the step of searching for the boot disk. Add one device at a time until the problem occurs. This is the beginning of the power supply problem. If the CPU temperature is very high at this time, it means you need a better heat sink and fan. Be careful to choose high-quality ones when purchasing them, because the good ones are not much more expensive than the bad ones, but there is a significant difference in quality.

The power supply fan is an important component of the power supply, responsible for extracting the hot air inside the power supply (some parts blow air inward). When you open the power supply, you can see two large heat sinks. The performance and limit parameters of the high-power tubes on the heat sinks directly affect the safe carrying power and product cost of the power supply. In addition, the two sockets at the back of the power supply are used to connect to the external power supply and provide sockets for the monitor. Generally, the male socket is the power socket. There is a voltage setting switch between the two sockets for switching between 110V and 220V. The 220V voltage standard is commonly used in China. If it is set to 110V by mistake, it will cause damage to the power supply.

Many ATX power supplies have eliminated the monitor socket and installed a power switch in its place. This is a real physical power cut-off switch, which is fundamentally different from the POWER button on the front of the ATX case. It also reduces the power that the power supply provides to the monitor, thereby extending the life of the power supply and the life of the monitor.

ATX power supplies provide multiple sets of plugs, mainly 20-pin motherboard plugs, 4-pin drive plugs and 4-pin small drive special plugs. There is only one 20-pin motherboard plug and it is directional, which can effectively prevent mis-insertion. The plug also has a fixing device that can hook the socket on the motherboard to prevent the connector from loosening and causing the motherboard to suddenly lose power when it is working. The 4-pin drive power plug is the most widely used. All CD-ROMs, DVD-DOMs, CD-RWs, hard disks and even some fans need it. The 4-pin plug provides two sets of voltages, +12V and +5V. Generally, the red wire represents the +12V power supply, the red wire represents the +5V power supply, and the black wire represents the 0V ground wire. This type of 4-pin plug power supply provides the most. If the user still does not have enough, he can use a one-to-two adapter cable.

The principle of the four-core small drive special plug is the same as the ordinary four-core plug, but the interface form is different. It is specially designed for powering traditional small drives.

There are many version structures of ATX power supply, including ATX 1.0, ATX1.1, ATX2.01, ATX2.02, etc. Currently, ATX2.01 is the main one. For high-end chassis or high-end power supplies purchased separately, there are ATX2.02 version products.