Adaptive on-time control for four-switch switching converter

A control method for a switching converter, wherein the switching converter is configured to receive an input voltage and provide an output voltage, and the switching converter having a first switch, a second switch, a third switch and a fourth switch, the control method comprising:

• providing a first set signal to turn on the first switch based on a reference signal and the output voltage;
• providing a second set signal to turn on the third switch based on the first set signal;
• generating a first on-time period based on the input voltage and the output voltage;
• generating a second on-time period based on the input voltage, the output voltage, a first parameter, and a second parameter;
• turning on the first switch and turning off the second switch when an on-time period of the first switch achieves the first on-time period;
• turning on the third switch and turning off the fourth switch when an on-time period of the third switch achieves the second on-time period;
• increasing the on-time period of the third switch as a difference between the output voltage and the input voltage increases when the output voltage is larger than the input voltage;
• and
• decreasing the on-time period of the third switch as the difference between the input voltage and the output voltage increases when the output voltage is less than the input voltage.

A switching converter, comprising:

• a first switch, having a first end, a second end, and a control end, wherein the first end of the first switch is configured to receive an input voltage;
• a second switch, having a first end, a second end, and a control end, wherein the first end of the second switch is coupled to the second end of the first switch, the second end of the second switch is coupled to a reference ground;
• an inductor, having a first end and a second end, wherein the first end of the inductor is coupled to the second end of the first switch and the first end of the second switch;
• a third switch, having a first end, a second end and a control end, wherein the first end of the third switch is coupled to the second end of the inductor, and the second end of the third switch is coupled to the reference ground;
• a fourth switch, having a first end, a second end and a control end, wherein the first end of the fourth switch is coupled to the second end of the inductor and the first end of the third switch, and the second end of the fourth switch is configured to provide an output voltage;
• and
• a control circuit, configured to provide a first drive signal to control the first switch and a second drive signal to control the second switch based on a first set signal, and provide a third drive signal to control the third switch and a fourth drive signal to control the fourth switch based on a second set signal;
• wherein
• when the output voltage is larger than the input voltage, an on-time period of the third switch is adaptively adjusted according to the input voltage, the output voltage and a first parameter, such that the on-time period of the third switch increases as a difference between the output voltage and the input voltage increases;
• and wherein
• when the output voltage is less than the input voltage, the on-time period of the third switch is adaptively adjusted according to the input voltage, the output voltage and a second parameter, such that the on-time period of the third switch decreases as the difference between the input voltage and the output voltage increases, the second parameter is different from the first parameter.