PFC power factor correction circuit - Home Appliances

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PFC is an abbreviation of PowerFactorCorrection, translated as power factor correction. According to the relevant requirements of the state, LCD TVs with a total power greater than 75W should be equipped with PFC circuits. The purpose is to improve the utilization of the mains and enhance the anti-jamming performance of the switching power supply.
The PFC circuit is also called a boosted POST circuit. A parallel switching power supply is added between the rectifying element and the filter capacitor.

When VT1 is turned on, the voltage of the bridge rectifier BD1 rectified output is grounded through the energy storage inductor L1.VT1, and the electric energy is stored in the inductor L1 in the form of magnetic energy, and the induced electromotive force is left positive and right negative.
When VT1 is turned off, the induced electromotive force on the inductor L1 is reversed, and the magnetic energy is converted into electric energy, and the left and right are positive. This voltage is superimposed with the voltage of the bridge rectifier output, and a voltage of about +380V is formed to supply power to the storage capacitor C1.
When VT1 is turned on again, the above process is repeated, but at this time, since the voltage stored in the capacitor C1 is higher than the voltage at the positive terminal of the diode D1, D1 is turned off, so the operation of the diode D1 is intermittent. Since the bridge rectifier BD1 voltage and the voltage on the large inductor L1 simultaneously supply power to the load, the output voltage is as high as +375V to +400V. When the grid voltage is 220V, this voltage value is +380V, so the PFC output voltage is commonly known as +380V.