| 主权项 |
1. A control circuit used in a boost PFC converter, the boost PFC converter is configured to receive an input signal to provide an output signal, the boost PFC converter includes a rectifier, an energy storage component, a first power switch, a second power switch and a zero crossing detector generating a zero crossing detecting signal indicative of a zero crossing condition of a current flowing through the energy storage component, the control circuit comprising:
a peak holding circuit, configured to receive a current sense signal indicative of the current flowing through the energy storage component, and to generate a peak holding signal indicative of the peak current flowing through the energy storage component; a saw-tooth wave generator, configured to generate a saw-tooth wave signal; a first comparator, configured to receive the peak holding signal, the saw-tooth wave signal, and a reference voltage, to generate a comparison signal by comparing the sum of the peak holding signal and the saw-tooth wave signal with the reference voltage; a logical unit, having a first input terminal coupled to the first comparator to receive the comparison signal, a second input terminal configured to receive the zero crossing detecting signal, and an output terminal configured to generate a dead time signal; a logical NOR circuit, having a first input terminal coupled to the output terminal of the logical unit to receive the dead time signal, a second input terminal configured to receive the zero crossing detecting signal, and an output terminal configured to generate the set signal; a voltage converting unit, configured to receive a fixed voltage and the dead time signal, to generate a converting voltage; a voltage-current converter, coupled to the voltage converting unit to receive the converting voltage, and to generate a current signal proportional to the converting voltage; a first charge capacitor and a charge switch, parallel coupled between the voltage-current converter and the reference ground, wherein the charge switch 94 has an opposite switching status to the first power switch; an error amplifier, having a first input terminal configured to receive a feedback signal indicative of the output signal, a second input terminal configured to receive a voltage reference signal, and an output terminal configured to generate a compensation signal by amplifying and integrating the difference between the feedback signal and the voltage reference signal; a second comparator, having a first input terminal configured to receive a voltage across the first charge capacitor, a second input terminal coupled to the output terminal of the error amplifier to receive the compensation signal, and an output terminal configured to generate the reset signal by comparing the voltage across the first charge capacitor with the compensation signal; and a logical circuit, having a set input terminal coupled to the logical NOR circuit to receive the set signal, a reset input terminal coupled to the output terminal of the second comparator to receive the reset signal, and an output terminal configured to generate a switch control signal to control the first power switch. |
