What are PF and PFC and why are they important in specifying LED drivers?
Power Factor (abbreviated PF) is the ratio of real power to apparent power in an AC power system and is expressed as a number between 0 and 1. Real power is the actual power drawn by the load whereas apparent power is the product of the load current and load voltage. Since the voltage and current may be out of phase this product may be significantly greater than the real power. PFC is the abbreviation for Power Factor Correction. In order to maintain a high power factor, switch mode power supplies (including LED drivers) must employ some form of power factor correction. This is an important issue because a load with a low power factor draws more current than a load with a high power factor for the same amount of real power transferred. Low power factor therefore results in greater power losses in the utility lines. There are a number of standards now in effect requiring certain levels of power factor correction in switch-mode power supplies and/or LED drivers.
