All About Power Factor Correction (PFC)

Power factor is the ratio of actual power (active: S) to total power consumed (apparent: P) or Apparent Power (P) / Active Power (S) – value is between 0 and 1.

PFC allows power supplies to level-out current peak levels to create a more even distribution of power, which also means more effective power conversion. This slso results in reducing stress on neutrals and transformers. There are two types of PFC - Active PFC and Passive PFC.

Passive vs. Active PFC

Passive Power Factor Correction (Passive PFC) uses a filter to control the apparent power, however it may not be the most efficient method. This is done by using an inductor, capacitor circuitry inductance, to control the harmonic current (red wave) and only allow currents to pass at a pre-determined frequency (e.g. 50 or 60 Hz). The power factor improvement with passive PFC is usually around 75%~80%.

Active Power Factor Correction (Active PFC) uses a circuitry to correct the amount of power drawn to obtain the best ratio of power factor. The circuit also reduces total harmonics and correction for AC input voltages. It is the preferred PFC of choice as it produces a more efficient power frequency, as compared to no PFC or Passive PFC. Active PFC can theoretically produce a power factor of over 95%.

Quick points on benefit of PFC
  • Allow more power units to be operated on the same “bandwidth”.
  • Save cost on power distribution system
  • Conserve energy
Active PFC is included in the following Cooler Master power supplies series:

Real Power Pro / Real Power M series
Silent Pro M series
UCP series with up to 0.99 PF.