The PFC(power factor correction) is a technique of increasing the PF of a power supply. Switching power supplies without PFC draw current in short, high-magnitude pulses. These pulses can be smoothed out by using active or passive techniques. This reduces the input RMS current and apparent input power, thereby increasing the PF.
The PFC shapes the input current in order to maximize the real power from the AC supply. Ideally, electrical equipment should present a load that emulates a pure resistor, meaning that the reactive power would be zero. And the current and voltage waveforms would be the same sine wave and in phase with one another. However, due to the reactive components in a majority of circuits, there is always a power lag that leads to lower PF.
In an ideal system, all the power drawn from the AC mains is utilized in doing useful work. This is only possible when the current is in phase with the voltage. When the phase between the two varies, some of the energy from the AC outlet does not perform useful work and is lost.
The power generating company must therefore produce more power to meet the demand for the useful power and the one that is lost. This means more capital investments in generation, transmission, distribution and control. The costs are passed on to the consumer in addition to contributing to global warming.
PFC tries to push the power factor of the electrical system such as the power supply towards 1, and even though it doesn’t reach this it gets to as close as 0.95 which is acceptable for most applications.