power factor correction (power supply) (PFC)

Power Factor Correction (PFC) is a function of power supplies and Power Line Conditioners( PLC) to adapt them to changing power outputs. It involves compensating for the current draw of switching power supplies, which is characterized by a high harmonic content, non-sinusoidal current and short current peaks.

The power consumption of personalcomputers mainly depends on the motherboard and powerful graphics cards. Operational power consumption can lead to additional loads of more than 100 W. Power Factor Correction is intended to compensate for all factors that influence power consumption. It is intended to prevent grid disturbances and reactive power and to ensure that the power grid is loaded with as constant a current as possible. In PFC technology, a distinction is made between passive and active power factor correction.

Passive power factor correction works with capacitors and inductors. Thus, by connecting a capacitor in parallel with an inductive load, the power factor is improved and the supply current is reduced without changing the current or the power consumed by the load. The use of a reactor and an RC element in parallel creates a low- frequency low-pass filter that attenuates voltage spikes occurring in switching power supplies. The power factor value for this method is between 0.7 and 0.8.

The active power factor correction works with thyristors which are controlled by the power consumption. The power factor values are better than for the passive method and are between 0.9 and 1.