Systems and methods for reducing electromagnetic interference by adjusting switching processes

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

• a signal generator configured to receive a feedback signal associated with an output signal of a power conversion system and a current sensing signal associated with a primary current flowing through a primary winding of the power conversion system and generate a modulation signal based on at least information associated with the feedback signal and the current sensing signal;
• and
• a driving component configured to receive the modulation signal and output a drive signal to a switch based on at least information associated with the modulation signal;
• wherein the driving component is further configured to, if the modulation signal changes from a first logic level to a second logic level, change the drive signal in magnitude from a first magnitude value to a second magnitude value during a time period in order to open the switch, the time period being larger than zero.

A driving component for outputting a drive signal to a switch coupled to a primary winding of a power conversion system, the driving component comprising:

• a first diode including a first diode terminal and a second diode terminal;
• a second diode including a third diode terminal and a fourth diode terminal;
• a capacitor including a first capacitor terminal and a second capacitor terminal;
• a current source component including a first source terminal and a second source terminal;
• and
• a first transistor including a first transistor terminal, a second transistor terminal, and a third transistor terminal;
• wherein:
• the second source terminal is coupled to the first transistor terminal;
• the third transistor terminal is coupled to the first diode terminal;
• the second diode terminal is coupled to the third diode terminal and the first capacitor terminal;
• and
• the second capacitor terminal is coupled to the fourth diode terminal.

A driving component for outputting a drive signal to a switch coupled to a primary winding of a power conversion system, the driving component comprising:

• an AND gate component including a first input terminal, a second input terminal and a first output terminal;
• a comparator including a third input terminal, a fourth input terminal and a second output terminal;
• a first transistor including a first transistor terminal, a second transistor terminal and a third transistor terminal;
• and
• a second transistor including a fourth transistor terminal, a fifth transistor terminal and a sixth transistor terminal;
• wherein:
• the first transistor terminal is coupled to the first input terminal;
• the second transistor terminal is coupled to the fifth transistor terminal;
• the third transistor terminal is coupled to the sixth transistor terminal;
• the fourth transistor terminal is coupled to the first output terminal;
• and
• the second output terminal is coupled to the second input terminal.

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

• receiving a feedback signal associated with an output signal of a power conversion system and a current sensing signal associated with a primary current flowing through a primary winding of the power conversion system;
• processing information associated with the feedback signal and the current sensing signal;
• generating a modulation signal based on at least information associated with the feedback signal and the current sensing signal;
• receiving the modulation signal;
• processing information associated with the modulation signal;
• and
• outputting a drive signal to a switch based on at least information associated with the modulation signal;
• wherein the process for outputting a drive signal to a switch based on at least information associated with the modulation signal includes, if the modulation signal changes from a first logic level to a second logic level, changing the drive signal in magnitude from a first magnitude value to a second magnitude value during a time period in order to close the switch, the time period being larger than zero.

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

• receiving a feedback signal associated with an output signal of a power conversion system and a current sensing signal associated with a primary current flowing through a primary winding of the power conversion system;
• processing information associated with the feedback signal and the current sensing signal;
• generating a modulation signal based on at least information associated with the feedback signal and the current sensing signal;
• receiving the modulation signal;
• processing information associated with the modulation signal;
• and
• outputting a drive signal to a switch based on at least information associated with the modulation signal;
• wherein the process for outputting a drive signal to a switch based on at least information associated with the modulation signal includes, if the modulation signal changes from a first logic level to a second logic level, changing the drive signal in magnitude from a first magnitude value to a second magnitude value during a time period in order to open the switch, the time period being larger than zero.