Patent ID: 8259470

Claim:
A control circuit, comprising: an obtaining sub-circuit, configured to obtain a voltage signal from a reverse surge current when the reverse surge current appears on a primary side of a switch power circuit of a synchronous rectification circuit; a maintaining sub-circuit, configured to continuously output a first control signal in a preset first time period when the voltage signal is greater than a preset first voltage threshold; and a control sub-circuit, configured to control and switch off switch tubes of a secondary side of the switch power circuit of the synchronous rectification circuit according to the first control signal, wherein the maintaining sub-circuit comprises a comparator and a first control sub-circuit; wherein the comparator is configured to compare the voltage signal with the preset first voltage threshold, and output the first control signal when the voltage signal is greater than the first voltage threshold; wherein the comparator is configured with a reset pin, when the reset pin is at a first level, the comparator is in a state of inputting, comparing, triggering and maintaining, and the comparator continuously outputs the first control signal; and when the reset pin is at a second level, the comparator is reset, and recovers a state of inputting, comparing and outputting; and wherein the first control sub-circuit is configured to control and reduce a voltage of the reset pin until the reset pin is at low level after the first time period when the voltage signal is greater than the first voltage threshold and the comparator outputs the first control signal.