Switching regulator and control circuit thereof, and method for determining on-time in switchng regulator

A control circuit for controlling a switching regulator to convert an input voltage to an output voltage by operating at least one power transistor switch, the power transistor switch having a terminal coupled to a node with non-constant voltage level, the control circuit comprising:

• a pin receiving a signal from the node with non-constant voltage level;
• a PWM generation circuit for generating a duty signal in a normal operation mode according to a feedback signal relating to the output voltage;
• a pulse skipping circuit for determining On-time in a pulse skipping mode according to the signal from the node;
• and
• a driver circuit for generating a driver signal according to one of the outputs from the PWM generation circuit and the pulse skipping circuit.

A method for determining On-time in a switching regulator which converts an input voltage to an output voltage by operating at least one power transistor switch, the power transistor switch having a terminal coupled to a node with a non-constant voltage level, the method comprising the steps of:

• generating a signal relating to an average of a signal from the node;
• generating a sawtooth wave signal according to the signal from the node, wherein the slope of the sawtooth wave signal relates to the input voltage;
• and
• determining On-time in the pulse skipping mode by comparing the signal relating to the average of the signal from the node with the sawtooth wave signal.