Method and apparatus for controlling the maximum output power of a power converter

A controller for a power converter, comprising:

• an input voltage sensor to be coupled to receive an input signal representative of an input voltage of the power converter;
• a current sensor to be coupled to sense a current flowing in a power switch;
• and
• a drive signal generator to be coupled to drive the power switch into an on state for an on time period and an off state for an off time period, wherein the drive signal generator is coupled to adjust a duty cycle of the power switch to be proportional to a value of the input signal multiplied by a time it takes the current flowing in the power switch to change between two current values when the power switch is in the on state.

A controller for a power converter, comprising:

• an input voltage sensor to be coupled to receive an input signal representative of an input voltage of the power converter;
• a current sensor to be coupled to sense a current flowing in a power switch;
• and
• a drive signal generator to be coupled to drive the power switch into an on state for an on time period and an off state for an off time period, wherein the drive signal generator is coupled to adjust a switching cycle period of the power switch in response to a difference between a time it takes the current flowing in the power switch to change between two current values when the power switch is in the on state and a control time period.

A method of controlling a power converter, comprising:

• switching a power switch between an on state and an off state;
• sensing an input signal representative of an input voltage of the power converter;
• sensing a current flowing in the power switch;
• and
• adjusting a switching cycle period of the power switch to be proportional to a value of the input signal multiplied by a time it takes the current flowing in the power switch to change between two current values when the power switch is in the on state.