The power factor refers to the relationship between the effective power and the total power consumption (apparent power), that is, the ratio of the effective power divided by the total power consumption (apparent power).
Basically, the power factor can measure the extent to which power is effectively utilized. When the power factor is larger, it means that the power utilization rate is higher. The power factor corrector on the switching power supply operates on the principle of controlling the time and waveform of the AC current input so that it is as consistent as possible with the DC voltage waveform, allowing the power factor to approach. This is very important for electronic equipment with a large demand for electricity.
Otherwise, the power consumed by the power equipment system may exceed its specifications and is likely to interfere with other electronic equipment in the copper system. Under normal circumstances, when the electronic device does not have Power Factor Correction (PFC), its PF value is only about 0.5.
PFC English is called "power factor Correction", which means "power factor correction". Power factor refers to the relationship between effective power and total power consumption (apparent power), that is, the effective power divided by the total power consumption. The ratio of the amount (apparent power).
Basically, the power factor can measure the degree to which power is effectively utilized. When the power factor value is larger, it represents the higher the power utilization rate. The computer switching power supply is a capacitive input type circuit, and the phase difference between current and voltage causes loss of switching power. At this time, the PFC circuit is required to increase the power factor. There are two types of PFCs today, one is passive PFC (also called passive PFC) and the active PFC (also called active PFC).
PFC makes an image analogy: the volume of a beer mug is certain, it is like the power, but when you pour beer, it is very fierce, it is a lot of foam, this is the reactive power, the bottom of the beer In fact, very few, these are active power. At this time, the utilization rate of the wine glass is very low, which is equivalent to the power factor of the power supply is very small. The addition of PFC is to reduce the reactive power on the input side and improve the utilization rate of the power grid. For ordinary industrial power, the phase of the current and the phase of the voltage are adjusted together. For the switching power supply, it is severely distorted. The AC side input current becomes sinusoidal, and there is also the function of lowering the lower harmonics because the input current is sinusoidal.
The benefits of power factor correction include:
(1) Saving electricity costs (2) Increasing power system capacity (3) Stabilizing current Low power factor means low power efficiency, and the lower the power factor, the higher the proportion of power is consumed in the distribution network, if lower power The factors are not corrected and the power company, in addition to the effective power, also provides virtual work that is not related to the work, which leads to the need for larger generators, converters, conveyors, cables and additional distribution systems. Omitted facilities to compensate for the lack of wear and tear. The PFC-enabled electronic equipment can help improve its energy use rate and reduce electricity bills. PFC is also an environmentally-friendly technology that can effectively reduce harmonics that cause power pollution and is a useful function for all of society.
3 How does the PFC power supply help save energy?
By reducing the voltage-current that your power equipment must transmit to provide at least the amount of power required by a power supply. Because less unwanted harmonics are generated (which only adds unnecessary burden to the AC transport system), power consumption is reduced.
4 What is harmonic? Harmonics are a form of noise that is essentially caused by the combination of a composite 60-cycle sine wave. They usually occur in power supplies and other frequency-related machines, including computers. Harmonics can distort the basic sine wave pattern and cause high currents in the water and ground lines of the same system.
[Note: US power cord, there are 3 pins]
In January 2001, the EU officially detailed the harmonics of electronic equipment, stipulating that electronic equipment products with output ranging from 75W to 600W must pass the harmonic test [Harmonics test (EN61000-3-2)]. The harmonic interference generated by the measuring object on the power system; since May 2002, China has regulated the power factor correction (PFC) as the standard equipment function of electronic equipment since the electronic equipment purchased by government agencies; Japan has begun It is a future trend to develop various plans for saving electricity. I believe that other countries will follow suit in the near future.
6 What is Active/Passive Power Factor Correction (Active/Passive PFC)? Passive PFC uses a combination of inductors, capacitors, etc. to reduce harmonic currents. The input current is 50Hz to 60Hz at low frequencies, so a large amount of inductors and capacitors are required. And its power factor correction is only 75%~80%. Active PFC uses active components [control sine conductor On/Off switch]. The basic operation principle is to adjust the input current waveform to make it as similar as possible to the input voltage waveform. Nearly 100%.
In addition, the active PFC has another important added value, that is, the power supply input voltage range can be amplified to a global voltage of 90Vdc to 264Vdc, and the power supply does not need to switch voltage as in the past. In contrast, active PFCs are also expensive because of their superior functionality. In addition, consumers should also pay attention to the fact that in general, many passive designs are not placed on the 115V system, because the manufacturer only makes 230V parts, so consumers in the 115V voltage system should pay attention to this problem. It may cost more and buy a power supply that does not have a PFC function at 115V.
Passive PFC generally uses the inductance compensation method to reduce the phase difference between the fundamental current and voltage of the AC input to improve the power factor. The passive PFC includes silent passive PFC and non-silent passive PFC. The power factor of a passive PFC can only reach 0.7 to 0.8, which is generally near the high voltage filter capacitor.
The active PFC is composed of an inductor, a capacitor and an electronic component. The volume is small, and the waveform of the current is adjusted by a dedicated IC to compensate for the phase difference between the current and the voltage. Active PFC can achieve higher power factor - typically up to 98%, but at a relatively high cost. In addition, the active PFC can also be used as an auxiliary power supply. Therefore, in the active PFC circuit, the standby transformer is often not required, and the ripple of the active PFC output DC voltage is small, and the power supply does not have to be filtered with a large capacity. capacitance.
(1) The active PFC increases the power factor value to over 95%, and the passive PFC can only be improved to 75%. In other words, active PFC can save more energy than passive PFC.
(2) The weight of the power supply using the active PFC is much lighter than the passive PFC products with bulky components, and the thinner and thinner products are the inevitable trend in the future 3C market.
The correction effect is much better than the European EN harmonic specification, even if the future specifications are more stringent.
As the demand for IC parts increases, so does the cost.
Less risk of shortage of raw materials.
More passive professional solutions.
It can bring high added value of global voltage at a lower cost.
The power factor is close to 100% perfect, which makes the power utilization extremely excellent and is good for the environment.
In response to the future CPU development trend, the output wattage (electricity) requirements will be higher, and the active PFC will have better competitiveness because the cost does not increase with the increase of the output wattage.
When the harmonic specifications of EN in Europe become more and more strict, the quality of inductive mass production needs to be improved, and the production difficulty will increase.
Heavy weight increases the risk of damage to the power supply during transportation.
The risk of shortage of raw materials is high.
If the internal structure of the power supply is fixed incorrectly, it is easy to generate vibration noise.
When the power supply output exceeds 300 watts, the passive PFC will be less competitive in terms of material cost and product performance.
10 How to distinguish active power factor correction?
Knowing the benefits of Active Power Factor Correction, what users most want to know is how to distinguish between power supplies that really have active power factor correction. Here are a few simple ways to measure:
(1) See the text description:
The accuracy rate is over 90%. Because power factor correction is a very useful feature, manufacturers certainly want to attract consumers, so this feature must be described in words. Therefore, products that see the words "power factor correction", "Power Factor Correct" or "PFC" have power factor correction. In the same way, because the active passive power factor is high, there is no reason for the manufacturer to have a special book, so basically no explanation is that the active power factor correction product must be passive.
(2) Look at the specification:
The accuracy rate is 100%. If there is power factor correction, the value of Power Factor (PF) should be seen in its product specification. We know that the PF value is more than 90% to be the active power factor correction.
(3) Look at the appearance of the power supply:
The accuracy rate is 50%. Under the current known technology, a power supply with active power factor correction does not have a voltage switch (mostly red), and its input voltage must be a full range/universal free input or a fixed voltage. It cannot be a switching voltage. So if you see a voltage switch. There will be no active power factor correction. On the contrary, not all power supply switching switches (mostly red) have active power factor correction, so the accuracy of using this method is only 50%. It is recommended to verify the interaction with the first two pointers.
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