Patent ID: 7511466

Claim:
A control circuit comprising: a switching circuit for generating a switching signal and an auxiliary signal, wherein the switching signal is used to regulate the switching regulator, and the auxiliary signal is used to control a synchronous rectifier; and an evaluation circuit for generating a timing signal in response to an input signal, a control signal, and the switching signal, wherein the timing signal is used for turning off the synchronous rectifier to prevent a reverse current to the synchronous rectifier, the input signal is related to the input voltage of the switching regulator, and the control signal is related to the output voltage of the switching regulator, wherein the evaluation circuit further comprising: an input circuit for generating a charge signal and a discharge signal in accordance with the input signal and the control signal; and a timer circuit for generating the timing signal in accordance with the charge signal, the discharge signal, and the switching signal, wherein the charge signal and the switching signal generate a charge voltage, and the charge voltage and the discharge signal generate the timing signal when the switching signal is turned off.