What is active PFC and what is passive PFC?

PFC can be divided into active type and passive type, which mainly depends on the characteristics of components that control PFC. ..

Passive PFC adopts passive components, which directly connects the inductance between the incoming line of AC power supply or rectifier bridge and the 200V capacitor for filtering, and at the same time converts the correction of switching circuit. The PF value is about 70~80%, and the larger the wattage, the larger the passive PFC volume. The input voltage must be manually switched to 1 15V or 230V. The biggest advantage of passive PFC is low EMI (electromagnetic interference) and simple circuit, so the production cost is low.

Active PFC adopts active components, and switches are inserted between the input rectifier bridge and the 200V capacitor for filtering, so as to control the input current waveform to follow the grid voltage waveform and make the power supply resistive. Active PFC supports a wide range of input voltage from 90 V to 270 V (standard is 220V), and the PF value is above 90%, even reaching 100%. The volume and weight of active components are much lighter, which breaks the traditional concept of heavy power supply. At the same time, after using active PFC, the capacitor with smaller capacity can also be used in DC filtering part. However, active PFC has complex structure and high cost, and is mostly used in high-power switching power supply.