PFC Module

PFC stands for Power Factor Correction.

Its core purpose:

To improve electrical energy efficiency and reduce pollution to the power grid.

To meet regulatory requirements (such as electromagnetic compatibility standards like IEC 61000-3-2).

The problems it addresses:

Conventional bridge rectifier capacitor filter circuits transform the alternating current (AC) input into a narrow pulse that only appears near voltage peaks. This causes two issues:

Low power factor:

Current and voltage waveforms are out of sync, exhibiting significant phase shift. Although actual active power consumption is low, the grid must supply greater apparent power, resulting in resource waste.

High Current Harmonics:

This pulsed current contains substantial harmonics that interfere with other devices on the same grid, causing “grid pollution.”

How PFC Modules Work:

The PFC circuit (typically a Boost topology) is positioned between the rectifier bridge and the main capacitor. Using a control chip, it continuously monitors the input voltage and current waveforms. By rapidly switching MOSFETs, it forces the input current waveform to track the input voltage waveform, transforming it into a smooth sine wave.

Primary Functions of PFC Modules:

Corrects the input current waveform into a voltage-in-phase sine wave, elevating the power factor to over 0.95 and approaching unity.

Delivers a stable, adjustable DC bus voltage (e.g., stabilizing a wide-range AC input of 85-265V into a 400V DC voltage), providing an ideal operating platform for downstream LLC modules.

Simple analogy: The PFC module acts like a “traffic cop.” It regulates the current flow (vehicle traffic) coming from the grid (road), organizing it into an orderly and smooth stream. This prevents congestion and chaos, thereby enhancing the transportation efficiency of the road (grid).