As far as we know, there are currently two types of PFC, one is passive PFC (also called passive PFC), and the other is called active power supply (also called active PFC).
Passive PFC is generally divided into “inductance compensation type” and “valley-filling circuit type”.
“Inductance compensation” is to reduce the phase difference between the fundamental current and voltage of the AC input to improve the power factor. “Inductance compensation” includes silent and non-silent, and the power factor of “inductance compensation” can only Reach 0.7~0.8, which is generally near the high-voltage filter capacitor.
“Valley-filling circuit type” belongs to a new type of passive power factor correction circuit, which is characterized by using the valley-filling circuit behind the rectifier bridge to greatly normalize the conduction angle of the rectifier tube. The pulse becomes a waveform close to a sine wave, and the power factor is increased to about 0.9. Compared with the traditional inductive passive power factor correction circuit, the advantages are that the circuit is simple, the power effect is significant, and there is no need to use a large-volume inductor in the input circuit.
The active PFC is composed of inductors, capacitors, and electronic components. It is small in size and uses a dedicated IC to adjust the current waveform to compensate for the phase difference between the current and voltage keys. Active PFC can achieve a higher power factor, usually up to 98% or more, but the cost is higher. In addition, active PFC can also be used as an auxiliary power supply. Therefore, in the use of active PFC circuits, standby transformers are often not needed, and The ripple of the output DC voltage of the active PFC is very small, and this factor does not need to use a filter capacitor of constant large capacity
Post time: Dec-17-2021