Switching converter with pulse skipping mode and control method thereof

A controller used in a switching converter, wherein the switching converter comprises a switching circuit having at least one switch, the controller comprises:

• an error amplifier having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive a reference signal, the second input terminal is configured to receive a feedback signal representative of the output voltage of the switching circuit, and wherein based on the reference signal and the feedback signal, the error amplifier provides a compensation signal at the output terminal;
• an oscillator configured to generate a clock signal and a slope compensation signal periodically;
• a ramp signal generator configured to generate a ramp signal;
• a first comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive a sum of a threshold voltage and the ramp signal, the second input terminal is coupled to the output terminal of the error amplifier to receive the compensation signal;
• a NOT gate having an input terminal and an output terminal, wherein the input terminal of the NOT gate is coupled to the oscillator to receive the clock signal;
• a AND gate having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the output terminal of the first comparator, the second terminal is coupled to the output terminal of the NOT gate;
• a second comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive a sum of the slope compensation signal and a current sensing signal representative of a current flowing through a switch of the switching circuit, the second input terminal is coupled to the output terminal of the error amplifier to receive the compensation signal;
• a OR gate having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the output terminal of the second comparator, the second input terminal is coupled to the output terminal of the AND gate;
• and
• a flip flop having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the oscillator to receive the clock signal, the second input terminal is coupled to the output terminal of the OR gate, wherein based on the clock signal and the output signal of the OR gate, the flip flop provides a control signal to control and ON and OFF switching of the at least one switch at the output terminal.

A control method of a switching converter, wherein the switching converter comprises a switching circuit having at least one switch, the control method comprises:

• generating a control signal to control the ON and OFF switching of the at least one switch, wherein the control signal comprises periodical switching pulses;
• comparing a feedback signal with a reference signal to generate a compensation signal, wherein the feedback signal is representative of the output voltage of the switching circuit;
• generating a ramp signal;
• comparing a sum of a threshold voltage and the ramp signal with the compensation signal to generate a pulse skipping signal;
• and
• skipping one or more switching pulses of the control signal in accordance with the pulse skipping signal.