power factor correction circuit

A power factor correction circuit, also known as a PFC (Power Factor Correction) circuit, refers to a circuit designed to improve power quality. Specifically, it is a circuit that aims to bring the power factor as close to 1 as possible. It works to eliminate the phase difference between voltage and current while suppressing harmonic currents.

The suppression of harmonics is regulated by the class definitions of international standard IEC 61000-3-2, which specify the maximum allowable harmonic current. PFC is generally required in related electronic equipment.

Power factor correction circuits can be broadly divided into three types: passive method, semi-switching method, and switching (active) method.

The passive method involves directly inserting a reactor into the power supply and is generally used in low-capacity power circuits. The semi-switching method refers to a method in which a switching element is added to the reactor insertion part of the passive method, and switching operations are performed during half cycles. By turning on the switching element and allowing current to flow even in sections where current previously did not flow, it expands the conduction area of the input current and improves the power factor. The switching (active) method of power factor correction involves inserting a boost converter (boost chopper circuit) between the diode bridge and the load. By controlling the current through on-off operation, it matches the input voltage and phase to improve the power factor. Operating with high-frequency switching using components such as MOSFETs allows for compact design of capacitors and reactors.