PFC is "power factor" meaning, mainly used to characterize the use of electrical energy efficiency of electronic products. The higher the power factor, the higher the utilization efficiency of electric energy.

There are two types of PFCS: passive PFCS (also known as passive PFCS) and active PFCS (also known as active PFCS). Passive PFC generally adopts inductance compensation method to reduce the phase difference between the AC input fundamental current and voltage to improve the power factor, but the power factor of passive PFC is not very high, only up to 0.7~0.8. Active PFC consists of inductance, capacitance and electronic components, small size, can achieve a high power factor, but the cost is higher than passive PFC.

Active PFC circuit often adopts high integration IC, PC power supply using active PFC circuit, at least has the following characteristics:

1) Input voltage can be from 90V to 270V;

2) Higher than 0.99 line power factor, and has the advantages of low loss and high reliability;

3) IC PFC can also be used as an auxiliary power supply, so in the use of active PFC circuit, often do not need standby transformer;

4) The output does not fluctuate with the input voltage, so a highly stable output voltage can be obtained;

5) Active PFC output DC voltage ripple is very small, and is a sine wave of 100Hz/120Hz (twice the power frequency), so the power supply using active PFC does not need to use a large capacity of filtering capacitor.