Systems and methods for regulating power conversion systems with output detection and synchronized rectifying mechanisms

A system controller for regulating a power conversion system, the system controller comprising:

• a comparator configured to receive an input signal and output a comparison signal based at least in part on the input signal;
• a first signal detector configured to receive the input signal and output a first detection signal based at least in part on the input signal;
• a second signal detector configured to receive the input signal and output a second detection signal based at least in part on the input signal;
• and
• a driver configured to:
• generate a drive signal based on at least information associated with the comparison signal, the first detection signal and the second detection signal;
• and
• output the drive signal to a gate terminal of a transistor to turn on or off the transistor in order to affect a current associated with a secondary winding of the power conversion system, the transistor including the gate terminal, a drain terminal and a source terminal;
• wherein:
• the comparator is further configured to determine whether the input signal is larger than a threshold;
• the first signal detector is further configured to determine whether the input signal includes one or more falling edges;
• the second signal detector is further configured to determine whether the input signal includes one or more rising edges;
• the driver is further configured to, under a discontinuous conduction mode of the power conversion system:
• if the comparison signal indicates the input signal is larger than the threshold, generate the drive signal at a first logic level to turn off the transistor;
• and
• if the first detection signal indicates the input signal includes the one or more falling edges, change the drive signal from the first logic level to a second logic level to turn on the transistor;
• and
• the driver is further configured to, under a continuous conduction mode of the power conversion system:
• if the first detection signal indicates the input signal includes the one or more falling edges, change the drive signal from the first logic level to a second logic level to turn on the transistor, and
• if the second detection signal indicates the input signal includes the one or more rising edges, generate the drive signal at the first logic level to turn off the transistor;
• and
• wherein the discontinuous conduction mode of the power conversion system is different from the continuous conduction mode of the power conversion system;
• wherein:
• the drain terminal is directly connected to a first winding terminal of the secondary winding, the secondary winding further including a second winding terminal;
• the first winding terminal of the secondary winding is also directly connected to a first resistor terminal of a resister, the resistor further including a second resistor terminal;
• the second winding terminal is directly connected to a first capacitor terminal of a capacitor, the capacitor further including a second capacitor terminal;
• the second capacitor terminal is directly connected to the source terminal;
• the second capacitor terminal and the source terminal both are biased to a ground voltage;
• and
• the second resistor terminal is connected to the comparator, the first signal detector and the second signal detector, directly or indirectly through an offset component.