Isolated synchronous rectification control circuit, control device, and control method

An isolated synchronous rectification control method, comprising:

• setting a primary side turn-on time constant and obtaining an integral value of the current flowing into a synchronous rectification control circuit;
• comparing the integral value of the current against a pre-configured value and controlling the turn-on of a synchronous rectifier based on a comparison result of a voltage of the synchronous rectification control circuit and a reference source;
• predicting a time required for turning on the synchronous rectifier based on the integral value of the current and providing a shielding time based on the predicted time for turning on the synchronous rectifier;
• when an actual time for turning on the synchronous rectifier exceeds the shielding time and the voltage of the synchronous rectification control circuit is greater than the reference source, controlling to turn off the synchronous rectifier.

An isolated synchronous rectification control device, comprising:

• an isolated synchronous rectification control circuit, including:
• a power supply module, configured to supply a voltage;
• a reference module, configured to generate at least a first and a second reference source;
• a comparator module, including a turn-on comparator configured to compare a voltage at a voltage terminal of the control circuit against the first reference source and a first turn-off comparator configured to compare the voltage at the voltage terminal of the control circuit against the second reference source;
• a primary side turn-on determination unit, configured to obtain an integral value of a current flowing into a time setting terminal of the control circuit and compare the integral value of the current against a pre-configured value;
• a secondary intermittent burst estimation unit, configured to predict a time required for turning on a synchronous rectifier based on the integral value of the current obtained by the primary side turn-on determination unit, to provide a shielding time based on the predicted time for turning on the synchronous rectifier, and to compare the shielding time against an actual time for turning on the synchronous rectifier;
• a logic unit, configured to generate logic control signals for turning the synchronous rectifier based on the comparison results from the turn-on comparator and the primary side turn-on determination unit, and logic control signals for turning off the synchronous rectifier based on the comparison results from the first turn-off comparator and the secondary side intermittent burst estimation unit;
• and
• a driver unit, configured to drive the synchronous rectifier based on the logic control signals generated by the logic unit;
• and
• a transformer, wherein:
• one end of the secondary output winding is connected to a ground terminal of the synchronous rectification control circuit and a bypass capacitor;
• and
• the other end of the secondary output winding is connected to the ground;
• a bypass capacitor connected to a power supply terminal of the synchronous rectification control circuit to provide a stable voltage for the synchronous rectification control circuit;
• a time constant setting resistor connected to a time setting terminal of the synchronous rectification control circuit to configure a primary side turn-on time constant and a secondary intermittent burst time estimation determination;
• and
• an output capacitor connected to a voltage terminal of the rectification control circuit to provide an output capacitance.