CONTROL CIRCUIT FOR A SYNCHRONOUS RECTIFICATION CIRCUIT, LLC RESONANT CONVERTER AND ASSOCIATED METHOD

摘要

A control circuit for a synchronous rectification circuit, a LLC resonant converter and a control method. The control circuit has a first comparing circuit, a second comparing circuit, a blanking circuit, a first logic circuit and a second logic circuit. The blanking circuit is configured to provide a first blanking signal and a second blanking signal to avoid one or more repeated conduction of a first synchronous rectifier and a second synchronous rectifier respectively, and the first blanking signal and the second blanking signal are logic complementary.

主权项

1. A control circuit for a synchronous rectification circuit, wherein the synchronous rectification circuit has a first synchronous rectifier and a second synchronous rectifier, and wherein each of the first synchronous rectifier and the second synchronous rectifier has a drain, a source and a gate, the control circuit comprises:
a first comparing circuit having an input terminal and an output terminal, wherein the input terminal of the first comparing circuit is configured to receive a first drain-source voltage signal of the first synchronous rectifier, and wherein the first comparing circuit is configured to compare the first drain-source voltage signal with a threshold voltage and to provide a first comparing signal at the output terminal; a second comparing circuit having an input terminal and an output terminal, wherein the input terminal of the second comparing circuit is configured to receive a second drain-source voltage signal of the second rectifier, and wherein the second comparing circuit is configured to compare the second drain-source voltage signal with the threshold voltage and to provide a second comparing signal at the output terminal; a blanking circuit having a first input terminal, a second input terminal, a first output terminal and a second output terminal, wherein the first input terminal of the blanking circuit is coupled to the output terminal of the first comparing circuit for receiving the first comparing signal, and wherein the second input terminal of the blanking circuit is coupled to the output terminal of the second comparing circuit for receiving the second comparing signal, and wherein the blanking circuit is configured to conduct a logic operation to the first comparing signal and the second comparing signal so as to provide a first blanking signal and a second blanking signal respectively at the first output terminal and the second output terminal, and wherein the first blanking signal and the second blanking signal are logic complementary; a first logic circuit having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the first logic circuit is coupled to the output terminal of the first comparing circuit for receiving the first comparing signal, and wherein the second input terminal of the first logic circuit is coupled to the first output terminal of the blanking circuit for receiving the first blanking signal, and wherein the first logic circuit is configured to conduct a logic operation to the first comparing signal and the first blanking signal so as to provide a first driving signal at the output terminal of the first logic circuit, and wherein the first driving signal is coupled to the gate of the first synchronous rectifier to control an on and off switching of the first synchronous rectifier; and a second logic circuit having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the second logic circuit is coupled to the output terminal of the second comparing circuit for receiving the second comparing signal, and wherein the second input terminal of the second logic circuit is coupled to the second output terminal of the blanking circuit for receiving the second blanking signal, and wherein the second logic circuit is configured to conduct a logic operation to the second comparing signal and the second blanking signal so as to provide a second driving signal at the output terminal of the second logic circuit, and wherein the second driving signal is coupled to the gate of the second synchronous rectifier to control an on and off switching of the second synchronous rectifier.