Power converter with synchronous control function and control method thereof

A power converter with synchronous control function, for converting an input voltage to an output voltage at an output terminal of the power converter, the power converter comprising:

• a first transformer;
• a power switch which is coupled to a primary winding of the first transformer and which is configured to be operably turned ON or OFF according to an operation signal, to control the primary winding of the first transformer, so that the input voltage coupled to the primary winding of the first transformer is converted to the output voltage coupled to a secondary winding of the first transformer;
• a switch control unit which is coupled to the power switch and which is configured to operably generate the operation signal according to a feedback signal which is related to the output voltage, and to operably generate a first synchronous signal which is related to the operation signal;
• a signal coupling circuit which is coupled to the switch control unit and which is configured to operably couple the first synchronous signal to generate a second synchronous signal corresponding to the first synchronous signal;
• a synchronous rectifying switch which is coupled between the secondary winding of the first transformer and the output terminal, and which is configured to be operably turned ON or OFF according to a synchronous rectifying switch signal, for synchronous rectification;
• and
• a secondary side control circuit which is coupled to the secondary winding of the first transformer and the synchronous rectifying switch, and which is configured to operably generate the synchronous rectifying switch signal according to a secondary side level detection signal and the second synchronous signal, to control the synchronous rectifying switch;
• wherein the synchronous rectifying switch signal determines a turned-OFF time point of the synchronous rectifying switch according to a level change along a first switching direction of the first synchronous signal, and wherein the operation signal determines a turned-ON time point of the power switch according to a level change along a second switching direction of the first synchronous signal, such that while the power switch is ON, the synchronous rectifying switch is OFF, wherein the first switching direction and the second switching direction are opposite to each other;
• wherein, there is a dead time between the turned-OFF time point of the synchronous rectifying switch and the turned-ON time point of the power switch, and the dead time corresponds to a pulse width of the first synchronous signal.