Active power factor correction circuit and starting method thereof

The invention discloses an active power factor correction circuit which comprises a rectifier module, a boost module, a sampling module, a zero-crossing detection module and a controller. The rectifier module is used for rectifying and filtering input alternating current to output direct current to the boost module. The zero-crossing detection module is used for generating a switching signal when the fact that the absolute value of the instantaneous value of alternating current outputted from an alternating current power supply is less than a preset threshold is detected, and outputting the switching signal to the controller. The control module is used for generating a drive signal according to a sampling signal and outputting the drive signal to the boost module when a received switching signal and a received sampling signal sent by the sampling module reach a preset second threshold during the start of the active power factor correction circuit, so as to control the operation mode of the boost module. The invention further provides a starting method of the active power factor correction circuit. According to the embodiment of the invention, the safety of the APFC circuit can be effectively improved.