PFC circuit is a power factor correction circuit that is an important component used in electronic equipment to improve the power factor of the AC power supply, reducing the negative impact on the network and the power plant, as well as improving the energy efficiency of the equipment.
It consists of three main components: an input filter, a rectifier, and a capacitor lagging compensation network. The input filter reduces input current noise and filters out interferences, providing a clean power standard while keeping the interface boost ratio and overall responsiveness unchanged. The rectifier efficiently converts AC current to DC current, which helps to evenly distribute DC loads and better respond to fast up and down switching load environments. The lagging compensation network improves power factor and reduces total harmonic distortion by adding an operating capacitor to the circuit.
The working principle is composed of inductive capacitors and electronic components, small in size, and special ICs to adjust the waveform of the current and compensate for the phase difference between the current and voltage.
Since the power appliances from the past inductive load (early television, radio and other power supply are used power transformer inductive devices) into a capacitive load with rectifier and filter capacitors, the meaning of its power factor compensation is not only the power supply of the voltage and current in different phases of the problem, the more serious is to solve the problem caused by the power supply current is a strong pulse state of electromagnetic interference (EMI) and electromagnetic compatibility (EMC) problems. EMC (Electromagnetic Interference) and EMC (Electromagnetic Compatibility) problems caused by the strong pulse of the power supply current.
This is a new technology developed at the end of the last century (its background stems from the rapid development and wide application of switching power supply). Its main purpose is to solve the electromagnetic interference (EMl) and electromagnetic compatibility (EMC) problems arising from the severe distortion of the current waveform due to capacitive loads.
So the modern PFC technology is completely different from the past power factor compensation technology, it is for the non-sinusoidal current waveform distortion and take, forcing the AC line current to track the voltage waveform instantaneous changes in trajectory, and make the current and voltage to maintain the same phase, so that the system is a purely resistive technology (line current waveform correction technology), which is the PFC (Power Factor Correction).
It is widely used in areas that require efficient use of energy, such as computers, LED lighting, and automobile engine ignition systems. These application scenarios require very high power factor and efficiency, and PFC circuits can correct low power factor and reduce switching losses while maintaining high efficiency levels. This not only improves the price/performance ratio of the product, but also extends the life of the equipment and reduces environmental pollution.
Currently there are passive PFC (passive PFC) as well as active PFC (active PFC).
There are two types of passive PFC: one is inductive compensation, adding an inductor between the rectifier bridge stack and the filter capacitor (appropriately selected inductance), the principle of operation is to use the inductor to reduce the phase difference between the AC input fundamental current and voltage, thereby improving the power factor; the other is to fill in the valley circuit type, the principle of operation is to use the rectifier bridge behind the fill in the valley of the circuit to increase the rectifier’s on-angle by filling in the Valley, so that the input current from the spike pulse to close to the sinusoidal waveform, the circuit and inductive compensation type compared to the advantages of simple circuit, power factor compensation effect.
Active PFC consists of an inductor-capacitor and its components, through a special IC to adjust the current waveform, the phase difference between the current and voltage compensation, active PFC can be used as an auxiliary power supply, and its output DC voltage ripple is very small.
PFC circuit plays a vital role in electronic equipment due to their unique operating principle and wide range of applications. Whether passive PFC or active PFC, they can effectively improve the power factor of the AC power supply, reduce electromagnetic interference, and enhance the energy efficiency and cost-effectiveness of the equipment.
