Power factor correction

AN4250

8/15

DocID024230 Rev 1

3

Power factor correction

The PFC is a power stage, which can correct the power factor. The circuit target allows the

input current in phase with the main voltage to reduce the harmonic distortion. PF values

are close to 1.

Working on the duty cycle or on the frequency of the switch commutation, the sinusoidal

current shape can be built. The entire system is managed by a microcontroller, which

compares the input main voltage with the output voltage and acts on the duty cycle.

Boost converter features two conduction modes; current waveforms depend on them.

In the DCM, the Power MOSFET of the Boost converter turns on when the inductor current

reaches zero, and turns off when the inductor current meets the desired value.

In the CCM, the Power MOSFET of the Boost converter turns on when the inductor current

is not zero.

Figure 7. Current waveforms on the inductor for the CCM/DCM Boost converter

AM17355v1