fter the bypass diode D2 is added, the bypass diode D2 charges the output large capacitor, the output voltage is established earlier, the PFC inductor can quickly demagnetize, and the current flowing through the PFC inductor can be reduced. Prevent PFC inductor saturation, reduce the peak current of the power MOSFET, and avoid damage to the power MOSFET.
The rationale for this interpretation is not entirely plausible:
Adding bypass diode D2 does reduce the peak current flowing through the PFC inductor and power MOSFET. However, without bypass diode D2, when the power MOSFET starts to work, even when the power MOSFET is turned on near the peak of the input sine wave, due to The control ICs all have soft-start function. The duty cycle of the power MOSFET does not work at the maximum state at first, but gradually increases from the minimum value. The overcurrent protection circuit OCP of the PFC also limits the maximum peak current of the power MOSFET.