Abstract: A zero-crossing detection circuit can include: a state judging circuit that generates a judging signal based on whether a body diode of a synchronous power switch is conducting when the synchronous power switch is off; a regulation voltage generator that reduces a regulation voltage when the judging signal indicates that the body diode is conducting, and increases the regulation voltage when the judging signal indicates that the body diode is not conducting, where a detection voltage includes a sum of the regulation voltage and a voltage at a first terminal of the synchronous power switch; and a comparison circuit that compares the detection voltage against a voltage at a second terminal of the synchronous power switch, and generates a zero-crossing detection signal that is activated to turn off the synchronous power switch when the detection voltage equals the voltage at the second terminal of the synchronous power switch.

Abstract: An output over-voltage protection circuit for power factor correction, which includes a chip external compensation network, a chip external resistor divider network, a static over-voltage detection circuit, a dynamic over-voltage detection circuit and a compare circuit; The chip external compensation network is connected between the chip external resistor divider network and the dynamic over-voltage detection circuit, the chip external compensation network converts the dynamic over-voltage signal conversion to the dynamic current signal and conveys it to the dynamic over-voltage detection circuit, the dynamic over-voltage detection circuit detects the dynamic current signal and ultimately produces the dynamic over-voltage signal (DYOVP); The dynamic over-voltage signal (DYOVP) is inputted into the compare circuit, which converts the dynamic over-voltage signal (DYOVP) into a voltage compared with a reference voltage and outputs a over-voltage control signal (OVP), so as to achieve a dynamic over-voltage prote

Abstract: A zero-crossing detection circuit can include: a state judging circuit that generates a judging signal based on whether a body diode of a synchronous power switch is conducting when the synchronous power switch is off; a regulation voltage generator that reduces a regulation voltage when the judging signal indicates that the body diode is conducting, and increases the regulation voltage when the judging signal indicates that the body diode is not conducting, where a detection voltage includes a sum of the regulation voltage and a voltage at a first terminal of the synchronous power switch; and a comparison circuit that compares the detection voltage against a voltage at a second terminal of the synchronous power switch, and generates a zero-crossing detection signal that is activated to turn off the synchronous power switch when the detection voltage equals the voltage at the second terminal of the synchronous power switch.

Abstract: An output over-voltage protection circuit for power factor correction, which includes a chip external compensation network, a chip external resistor divider network, a static over-voltage detection circuit, a dynamic over-voltage detection circuit and a compare circuit; The chip external compensation network is connected between the chip external resistor divider network and the dynamic over-voltage detection circuit, the chip external compensation network converts the dynamic over-voltage signal conversion to the dynamic current signal and conveys it to the dynamic over-voltage detection circuit, the dynamic over-voltage detection circuit detects the dynamic current signal and ultimately produces the dynamic over-voltage signal (DYOVP); The dynamic over-voltage signal (DYOVP) is inputted into the compare circuit, which converts the dynamic over-voltage signal (DYOVP) into a voltage compared with a reference voltage and outputs a over-voltage control signal (OVP), so as to achieve a dynamic over-voltage prote