Control circuit and method for maintaining high efficiency in a buck-boost switching regulator

A method for controlling a buck-boost switching regulator circuit to supply a regulated output voltage at an output node, the buck-boost switching regulator comprising an inductor, a first switch coupled between an input voltage and a first terminal of the inductor, a first diode with an anode coupled to GROUND and a cathode coupled to the first terminal of the inductor, a second switch coupled between a second terminal of the inductor and GROUND, and a second diode with an anode coupled to the second terminal of the inductor and a cathode coupled to the output node, the method comprising:

• generating a feedback signal that is proportional to the output voltage of the switching regulator;
• controlling the duty cycle of the first switch with a first drive signal generated in response to the feedback signal;
• and
• controlling the duty cycle of the second switch with a second drive signal generated in response to the feedback signal so that the duty cycle of the first switch is not equal to the duty cycle of the second switch during the time that the output voltage at the output node is regulated.

A method for controlling a buck-boost switching regulator circuit to supply a regulated output voltage at an output node, the buck-boost switching regulator comprising an inductor, a first switch coupled between an input voltage and a first terminal of the inductor, a second switch coupled between the first terminal of the inductor and GROUND, a third switch coupled between a second terminal of the inductor and GROUND, and a diode with an anode coupled to the second terminal of the inductor and a cathode coupled to the output node, the method comprising:

• generating a feedback signal that is proportional to the output voltage of the switching regulator;
• controlling the duty cycle of the first switch with a first drive signal generated in response to the feedback signal;
• controlling the duty cycle of the second switch with a second drive signal generated in response to the feedback signal so that the second switch is OFF when the first switch is ON, and the first switch is OFF when the second switch is ON;
• and
• controlling the duty cycle of the third switch with a third drive signal generated in response to the feedback signal so that the duty cycle of the first switch is not equal to the duty cycle of the third switch during the time that the output voltage at the output node is regulated.

A method for controlling a buck-boost switching regulator circuit to supply a regulated output voltage at an output node, the buck-boost switching regulator comprising an inductor, a first switch coupled between an input voltage and a first terminal of the inductor, a diode with an anode coupled to GROUND and a cathode coupled to the first terminal of the inductor, a second switch coupled between a second terminal of the inductor and GROUND, and a third switch coupled between the second terminal of the inductor and the output node, the method comprising:

• generating a feedback signal that is proportional to the output voltage of the switching regulator;
• controlling the duty cycle of the first switch with a first drive signal generated in response to the feedback signal;
• controlling the duty cycle of the second switch with a second drive signal generated in response to the feedback signal so that the duty cycle of the first switch is not equal to the duty cycle of the second switch during the time that the output voltage at the output node is regulated;
• and
• controlling the duty cycle of the third switch with a third drive signal generated in response to the feedback signal so that the second switch is OFF when the third switch is ON, and the third switch is OFF when the second switch is ON.

A control circuit for controlling a buck-boost switching regulator circuit for supplying a regulated output voltage at an output node, the buck-boost switching regulator comprising an inductor, a first switch coupled between an input voltage and a first terminal of the inductor, a second switch coupled between the first terminal of the inductor and GROUND, a third switch coupled between a second terminal of the inductor and GROUND, and a fourth switch coupled between the second terminal of the inductor and the output node, the control circuit comprising:

• signal generator circuitry comprising an input node coupled to the output node of the switching regulator circuit, a waveform generator providing a periodic waveform at an waveform output node, and first, second, third, and fourth output nodes, the first and second output nodes coupled to the input node of the signal generator circuitry, the third and fourth output nodes coupled to the waveform output node of the waveform generator;
• a first comparator circuit comprising a first and second inputs coupled to the first and third output nodes, respectively, of the signal generator circuitry;
• a second comparator circuit comprising a first and second inputs coupled to the second and fourth output nodes, respectively, of the signal generator circuitry;
• and
• logic circuitry comprising logic gates, the logic circuitry having a first input coupled to an output of the first comparator circuit, a second input coupled to an output of the second comparator circuit, and first, second, third, and fourth outputs coupled to the first, second, third, and fourth switches, respectively, wherein the first switch is OFF when the second switch is ON, the second switch is OFF when the first switch is ON, the third switch is OFF when the fourth switch is ON, and the fourth switch is OFF when the third switch is ON.

A control circuit for controlling a buck-boost switching regulator circuit for supplying a regulated output voltage at an output node, the buck-boost switching regulator comprising an inductor, a first switch coupled between an input voltage and a first terminal of the inductor, a first diode with an anode coupled to GROUND and a cathode coupled to the first terminal of the inductor, a second switch coupled between a second terminal of the inductor and GROUND, and a second diode with an anode coupled to the second terminal of the inductor and a cathode coupled to the output node, the control circuit comprising:

• signal generator circuitry comprising an input node coupled to the output node of the switching regulator circuit, a waveform generator providing a periodic waveform at an waveform output node, and first, second, third, and fourth output nodes, the first and second output nodes coupled to the input node of the signal generator circuitry, the third and fourth output nodes coupled to the waveform output node of the waveform generator;
• a first comparator circuit comprising a first and second inputs coupled to the first and third output nodes, respectively, of the signal generator circuitry;
• a second comparator circuit comprising a first and second inputs coupled to the second and fourth output nodes, respectively, of the signal generator circuitry;
• and
• logic circuitry comprising logic gates, the logic circuitry having a first input coupled to an output of the first comparator circuit, a second input coupled to an output of the second comparator circuit, and first, and second outputs coupled to the first and second switches, respectively.

A control circuit for controlling a buck-boost switching regulator circuit for supplying a regulated output voltage at an output node, the buck-boost switching regulator comprising an inductor, a first switch coupled between an input voltage and a first terminal of the inductor, a second switch coupled between the first terminal of the inductor and GROUND, a third switch coupled between a second terminal of the inductor and GROUND, and a diode with an anode coupled to the second terminal of the inductor and a cathode coupled to the output node, the control circuit comprising:

• signal generator circuitry comprising an input node coupled to the output node of the switching regulator circuit, a waveform generator providing a periodic waveform at an waveform output node, and first, second, third, and fourth output nodes, the first and second output nodes coupled to the input node of the signal generator circuitry, the third and fourth output nodes coupled to the waveform output node of the waveform generator;
• a first comparator circuit comprising a first and second inputs coupled to the first and third output nodes, respectively, of the signal generator circuitry;
• a second comparator circuit comprising a first and second inputs coupled to the second and fourth output nodes, respectively, of the signal generator circuitry;
• and
• logic circuitry comprising logic gates, the logic circuitry having a first input coupled to an output of the first comparator circuit, a second input coupled to an output of the second comparator circuit, and first, second, and third outputs coupled to the first, second, and third switches, respectively, wherein the first switch is OFF when the second switch is ON, and the second switch is OFF when the first switch is ON.

A control circuit for controlling a buck-boost switching regulator circuit for supplying a regulated output voltage at an output node, the buck-boost switching regulator comprising an inductor, a first switch coupled between an input voltage and a first terminal of the inductor, a diode with an anode coupled to GROUND and a cathode coupled to the first terminal of the inductor, a second switch coupled between a second terminal of the inductor and GROUND, and a third switch coupled between the second terminal of the inductor and the output node, the control circuit comprising:

• signal generator circuitry comprising an input node coupled to the output node of the switching regulator circuit, a waveform generator providing a periodic waveform at an waveform output node, and first, second, third, and fourth output nodes, the first and second output nodes coupled to the input node of the signal generator circuitry, the third and fourth output nodes coupled to the waveform output node of the waveform generator;
• a first comparator circuit comprising a first and second inputs coupled to the first and third output nodes, respectively, of the signal generator circuitry;
• a second comparator circuit comprising a first and second inputs coupled to the second and fourth output nodes, respectively, of the signal generator circuitry;
• and
• logic circuitry comprising logic gates, the logic circuitry having a first input coupled to an output of the first comparator circuit, a second input coupled to an output of the second comparator circuit, and first, second, and third outputs coupled to the first, second, and third switches, respectively, wherein the third switch is OFF when the second switch is ON, and the second switch is OFF when the third switch is ON.