Power knowledge
How much power to choose a PC power supply?

With the increase of computer speed, the power consumption is also increasing, such as hard disk, graphics card, CPU, etc. are all high power consumption users. Therefore, the requirements for PC power supply are also higher. If the PC power supply does not meet the requirements, the computer often freezes or restarts inexplicably. Then, what kind of PC power supply do we need to make the computer run stably and smoothly?


1. What is the actual power?


How to calculate the power of pc power supply? Many people have questions. Let's take the 300Wpc power supply as an example to explain. We know that pc power supply can be divided into 5V, 3.3V and 12V output. The output power of a pc power supply is equal to the sum of these three powers. If calculated according to power (W) = voltage (V) X current (A), its + The total output power of 5V and -5V is 106.5W; the total output power of +12V and -12V is 123.6W; and the output power of +3.3V is 52.8W. All of these output powers add up to 282.9W, which is clearly marked with it. The 300W does not match, so this cumulative calculation method is completely wrong.


In fact, the above calculation is the maximum power of the PC power supply, but this does not represent the fact. The PC power supply efficiency (that is, the actual power) is the last useful power for work. According to facts, the efficiency of a pc power supply is the ratio of the total output DC power to the input power, which means that the greater the power of the pc power supply, the more power it loses. But according to experience, the loss of +5V, +3.3V and +12V voltage is about 5%, and the loss of -5V and -12V voltage is about 10%. Therefore, the efficiency of ordinary pc power supply is usually 65% to 80%. between. In other words, the theoretical ideal output power of 300W mentioned above is between 188.5W and 232W in actual utilization.


2. How much power does the computer consume?


How much power do we need to choose a PC power supply for us? We need to analyze how much power a computer needs to consume? In fact, it is difficult to accurately calculate the PC power consumption of different components. Some manufacturers will provide the power consumption of products, such as hard disks, mouse keyboards, CPU fans, etc., but some manufacturers’ products do not provide power. We refer to it, so it can only be calculated by estimation. After estimating the overall maximum power according to the actual situation of the system, then according to this data, choose a pc power supply that meets the power supply requirements.


Take the AGP platform in the P4 era as an example. From the table above, the maximum power consumption of the computer is about 299W, and the power consumption when there is no load will exceed 200W. In theory, it is sufficient to buy a 300W pc power supply, but according to our analysis above, only about 232W of 300W is fully utilized. When the computer is not running at full speed, the problem will generally not occur, and the computer can run at this time. But when the whole brain is running at full speed for a long time, or the voltage of the mains is unstable, the voltage will be unstable after the PC power supply is overloaded. At this time, the computer will cause various problems due to insufficient power supply or voltage changes. produced. However, in most cases, computer components will not work at full speed, so many low-power PC power supplies can also work normally.

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