Power Factor Correction : Correction Required!

Power Factor Correction or PFC is the latest buzzword to be thrown around by power supply companies. Something they are making quite a lot of fuss about. And why not? There are very few features that differentiate one power supply from another.

Now, a lot has been said about PFC. Unfortunately, many of the explanations are either confusing or misleading. That's why we thought we would take a shot at clearing up the confusion.

What Is PFC?

First, let's take a look at what some manufacturers are saying about PFC. Here is a quote from Zalman :-

"In a conventional power supply with switching regulators, a rectifying circuit that converts an AC input source into a DC source for the primary circuit is used. In this rectifying circuit, a capacitor with a large capacitance is used to soften transient response and reduce ripple so that the switching regulator is not over-stressed.

However, the peak charge of the capacitor becomes greater with greater capacitance, and this leads to non-linear bursts of peak over-current into the primary circuit. Such peaks of current distort output voltage, create harmonic frequencies, and reduce power factor.

There is now an international standard for controlling harmonics (IEC100-3-2) and PFC is mandatory for home appliances consuming 70W or more power in EU nations as of January, 2001."

And here is a cryptic explanation by Enermax :-

"the utility PF rate =95% @ 230Vac at full rated load. From January 1, 2001, two standards¡mEN61000-3-2 (power line harmonics) and EN61000-3-3 (power line flicker)¡ngo into full effect to all EC countries. All products shipped to EC countries or placed on the market in this area must be compliant to these standards."

Confusing, isn't it? Well, let's clear up the confusion.