PFC is a very important parameter in computer power supply, the full name is computer power factor correction, referred to as PFC.
The computer power supply is responsible for converting alternating current (AC) into direct current (DC) to provide all the power for the host, so its energy conversion efficiency is a very important energy saving indicator. The energy conversion efficiency of the Power supply is not necessarily related to the nominal power size, it is the remaining proportion of the energy of the power supply in the process of dealing with AC to DC transformer, and this efficiency basically depends on the power Factor Correction circuit (PFC, Power Factor Correction) inside the power supply.
There are two main types of PFC, one is called active PFC and the other is called passive PFC.
Active PFC, also called active PFC. Active PFC uses active components [control lines and power sine conductor On\/Off switch], the basic operating principle is to adjust the input current wave shape to make it as similar as possible to the input voltage waveform, and the power factor correction can reach nearly 100%. In addition, an important added value of active PFC is that the input voltage range of the power supply can be expanded to a global voltage range of 90Vdc to 264Vdc, and the power supply does not need to switch voltages as usual. In contrast, active PFC is also more expensive because of its excellent features. In addition, consumers should also note that in general, many passive designs are not placed on 115V systems, because manufacturers only make 230V parts, so consumers under 115V voltage systems need to pay attention to this problem, may spend more money but buy a power supply without PFC function under 115V.
Passive PFCS, whether silent or not, they can be called passive PFCS. Passive PFC generally uses inductance compensation to reduce the phase difference between the fundamental current and voltage of the AC input to improve the power factor, but the power factor of passive PFC is not very high, can only reach 0.7~0.8. Compared with non-silent passive PFC, the silent passive PFC has higher requirements both in terms of cost and manufacturing process. What is also explained here is the reason why PFC produces noise. In principle, the part of the structure we see above is similar to the inductor, in the process of compensating the current and voltage, the process of charging and discharging is always carried out, thus producing magnetism, and eventually the surrounding metal components will produce vibration and then emit noise. The silent PFC is equivalent to the superposition of two non-silent PFC to achieve the purpose of vibration cancelling each other. However, in the means of eliminating noise, whether the installation is proper is also a factor that has a greater impact on the mute effect. In general, the effect of non-silent passive PFC is about the same as that of silent passive PFC, but both are lower than the power factor correction effect of active PFC.
Dynamic PFC is superior to passive PFC, so the power supply with active PFC circuit design must be preferred when choosing an energy-saving power supply.
Active PFC increases the power factor value to more than 95%, while passive PFC can only improve to about 75%. In other words, active PFC saves more energy than passive PFC.
The weight of the power supply using active PFC is much lighter than that of passive PFC products with bulky components, and the product is an inevitable trend of the future 3C market.
Advantages of active PFC:
The correction effect is far better than the European EN harmonics specification, even if the specification is more stringent in the future. As the demand for IC parts increases, the cost will decrease.
Less risk of raw material shortage.
More passive and professional solutions.
High added value for a wide range of voltages at a lower cost.
The power factor is close to perfect 100%, making the utilization of electricity extremely good for the environment.
In response to the future trend of CPU development, the output wattage (power) requirements will be higher, and the active PFC has a better competitiveness because the cost does not rise with the increase of the output wattage.
Disadvantages of passive PFC:
When the harmonics specification of European EN becomes more and more stringent, the quality of inductor mass production needs to be improved, and the production difficulty will be increased.
Heavy weight increases the risk of damage to the power supply during transport.
The risk of raw material shortage is high.
If the internal structure of the power supply is fixed incorrectly, it is easy to produce vibration noise.
When the power supply output exceeds 300 watts, passive PFCS become less competitive in terms of material cost and product performance.
PFC as an important factor to determine the power conversion efficiency, it is mainly divided into active PFC and passive PFC. The former brings a higher power factor but the cost will also have a great increase, the latter although the price is low but the power factor will also decrease.
The active PFC circuit itself consumes more power than the passive PFC circuit, which directly reduces the conversion efficiency of the power supply because more power is not utilized by the actual load. The power factor regulated by the PFC circuit saves energy for the power plant, but does not really save the user.
Active Power Factor Correction (APFC) is a technology designed to improve energy efficiency by improving the power factor of a power supply unit. Power factor refers to the phase relationship between the input current and the input voltage, which can be a good power factor (close to 1) or a poor power factor (close to 0). Good power factor can reduce the loss of useless power and improve the overall energy efficiency. APFC technology controls the phase of the voltage and current to ensure that the phase difference between the input current and the input voltage is as small as possible, so that the power factor is close to 1.
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APFC technology of computer power supply can effectively reduce harmonic interference, improve power conversion efficiency, and avoid load interference to the power grid. By using active PFC power supplies, you can reduce power consumption and power waste, making computer systems more efficient, reliable, and environmentally friendly.