How does a Power Factor Correction (PFC) boost converter work?

PFC boost converter shapes input current to follow rectified line voltage, achieving near-unity power factor and low harmonics. The boost stage operates in continuous or critical conduction mode. Control forces inductor current to track sinusoidal reference. Output voltage (typically 380-400V for universal input) must exceed peak line voltage. Benefits include: compliance with harmonic standards (IEC 61000-3-2), reduced input current for same power, and better utilization of utility infrastructure. Active PFC achieves PF > 0.99 and THD < 5%.