Active Power Factor Correction (APFC) is a technique used in power electronics to improve the power factor of an electrical load. Power factor is the ratio of real power (active power) to apparent power in an AC circuit. A low power factor can result in inefficient power utilization and increased energy losses in the system.
In many AC circuits, the current waveform may not be in phase with the voltage waveform, leading to a lagging power factor. This occurs when the load draws current in a non-sinusoidal manner or when there is a phase difference between the voltage and current waveforms.
Active Power Factor Correction involves using electronic components, typically power semiconductor devices like MOSFETs or IGBTs, to actively control the input current drawn by the load. The goal is to shape the current waveform in a way that makes it in-phase with the voltage waveform, thereby achieving a unity power factor (1.0) or close to it.
The APFC circuit monitors the input voltage and current and calculates the phase difference between them. Based on this information, it generates a control signal to adjust the switching of power semiconductor devices to ensure that the load draws a current that is proportional and in-phase with the input voltage. By actively correcting the power factor, APFC reduces the reactive power component of the load, which leads to several benefits:
Reduced energy losses: A higher power factor reduces the amount of reactive power flowing in the system, thus minimizing energy losses in power distribution and transmission.
Increased power system capacity: Improving the power factor allows power distribution systems to handle more loads and reduces the need for oversized equipment.
Compliance with regulations: Some utility providers impose penalties for low power factor, and APFC helps industrial and commercial consumers meet the required power factor levels.
Improved efficiency: With a better power factor, the overall efficiency of power supply systems, especially in AC-DC converters, is enhanced.
APFC is commonly used in various applications, such as switch-mode power supplies (SMPS), motor drives, induction heating systems, and other power electronic systems to improve overall energy efficiency and performance.