When the PFC inductor is saturated, the power MOSFET is turned on, especially near the peak value of the input sine wave, a very large peak current will be generated, because the current detection of the control IC usually has a certain delay, when the PFC inductor is saturated, the generated The di/dt is very large, even if the delay time of the current detection is very small, it will lead to a very large peak current, which will cause the power MOSFET to be damaged due to overcurrent.
Reduce the peak current of the PFC inductor and power MOSFET at the moment of power-on, prevent the saturation of the PFC inductor and damage the power MOSFET.
The reason for this explanation is: at the moment of power-on, the voltage of the output large capacitor has not yet been established. Since the large capacitor needs to be charged, the current through the PFC inductor is relatively large. At the moment when the power switch is turned on, especially when the input sine wave The PFC inductance may be saturated during the charging process of the output large capacitor. If the PFC circuit works at this time, the current flowing through the power MOSFET is very large, thereby damaging the power MOSFET.