Detailed PFC (power factor correction) and active and passive PFC analysis comparison

1. What is power factor correction (PFC)?

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 important for electronics that require a certain amount of power, otherwise the power consumed by the power system may exceed its specifications and most likely interfere with other electronic devices 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.

2. Why do we need PFC?

The benefits of power factor correction include:

1. Save electricity costs

2. Increase power system capacity

3. Stable current

Low power factor means low power efficiency. The lower the power factor, the higher the proportion of power is consumed in the distribution network. If the lower power factor is not corrected, the power company provides the power in addition to the effective power. Work unrelated virtual work, which leads to the need for larger generators, converters, conveyors, cables and additional distribution systems that can be omitted in order 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.

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.

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 on the water and ground lines of the same system. [Note: The US power cord has 3 pins, which is (Live, FireWire) - (Neutral, Waterline) - (Ground, Ground)]

Which countries have PFCs as standard equipment for electronic equipment?

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 (EN 61000-3-2)] The harmonic interference generated by the test object to 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; It is a future trend to start researching various options for saving electricity. I believe that other countries will follow suit in the near future.