Patent ID: 6995991

Claim:
A pulse width modulation (PWM) controller for a synchronous rectifier of a flyback power converter, comprising: a detection terminal, coupled to a secondary winding of a transformer of the flyback power converter through a detection diode for producing a detection signal; a first threshold-detection terminal; a second threshold-detection terminal, wherein said first threshold-detection terminal and said second threshold-detection terminal are applied to detect a secondary current flowing through said secondary winding of said transformer of the flyback power converter; a timing terminal, coupled to a programming resistor for determining a maximum pulse width of a single-pulse signal, wherein said single-pulse signal raises to high in response to a high state of said detection signal, wherein a high state of said single-pulse signal associates with a low state of said detection signal for generating a synchronous signal; an output terminal, outputting said synchronous signal to drive a MOSFET, wherein said MOSFET operates as a synchronous rectifier, wherein said MOSFET is switched on/off in response to the value of said secondary current and the status of said synchronous signal, wherein said MOSFET is switched on only when said synchronous signal is active and said secondary current is larger than a first threshold value; and a supply terminal; and a ground terminal.