In the PFC switching power supply, switching regulator power supply is a very important part. PFC in the switching regulator power supply function and the ordinary switching regulator power supply is not a huge difference, only in the power supply is different. Common switching regulator power supply needs 220V rectifier power supply, while PFC regulated switching power supply is powered by B+PFC.
After rectifying, no filtering capacitor is added, and the pulsating positive half cycle voltage without filtering is used as the power supply source of the chopper. As a series of "switching" operations of the chopper, the pulsating positive voltage is "chopped" into a current waveform with the following characteristics:
1. The current waveform is discontinuous, and its envelope and voltage waveform are the same, and the envelope and voltage waveform are in the same phase.
2. Due to the action of the chopper, the half wave pulsating DC electricity becomes high frequency (determined by the chopper frequency, about 100KHz) "AC" electricity. The high frequency "AC" electricity must be rectified again before it can be used by the post-stage PWM switch stabilized power supply.
3. From the external power supply, the electrical system achieves the AC voltage and AC current in phase and the voltage waveform and the current waveform are in line with the sinusoidal waveform, which not only solves the power factor compensation problem, but also solves the electromagnetic compatibility (EMC) and electromagnetic interference (EMI) problems.
This high-frequency "AC" power is then rectified by a rectifying diode and filtered into a DC voltage (power supply) to be fed to a backward-stage PWM switching power supply. This DC voltage is referred to in some sources as: B+PFC (TPW-4211 is the case), in the chopper output B+PFC voltage is generally higher than the original 220 AC rectifier filtering +300V, the reason is the choice of high voltage, the inductance of the line diameter is small, the line voltage drop is small, the filter capacitance capacity is small, and the filtering effect is good, low requirements for the post PWM switch tube and many benefits.
