Switching method to improve the efficiency of switched-mode power converters employing a bridge topology

• US 8,415,937 B2
• Filed: 08/31/2010
• Issued: 04/09/2013
• Est. Priority Date: 08/31/2010
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hester, Richard K.
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Quddus, Nusrat
• Application Number:
  US12/872,896
• Publication Number:
  US 20120049818A1
• Time in Patent Office: 952 Days
• Field of Search: 323/222, 323/271, 323282-285
• US Class Current: 323/282
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence

Abstract

Traditionally, buck-boost switching regulators with bridge topologies have been avoided due to their inability to seamlessly transition between buck mode and boost mode. Here, however, a buck-boost switching regulator with a bridge topology has been provided, which has an improved controller. Namely, a processor (such as a digital signals processor or DSP) provides digital control for the bridge to enable it so substantially seamlessly transition between buck mode and boost mode.

Claims

1. An apparatus comprising:

a buck-boost switching regulator having an input terminal, an output terminal, a predetermined buck gain, a predetermined boost gain, a predetermined dead-time, and a predetermined on-time; and

control circuitry that is coupled to at least one of the output terminal and the input terminal and that controls the buck-boost switching regulator, wherein the control circuitry employs a compensation function to determine pulse width modulation (PWM) duty cycles for the buck-boost switching regulator, wherein the control circuitry includes a processor and a storage medium with a computer program product embodied thereon, and wherein the computer program product includes;

computer code for operating the buck-boost switching regulator in a buck mode when an output of the compensation function is less than the predetermined buck gain;

computer code for operating the buck-boost switching regulator in a first bridge mode when the output of the compensation function is between the predetermined buck gain and an intermediate value;

computer code for operating the buck-boost switching regulator in a second bridge mode when the output of the compensation function is between the predetermined boost gain; and

computer code for operating the buck-boost switching regulator in a boost mode when the output of the compensation function is greater than the predetermined boost gain.

2. The apparatus of claim 1, wherein the buck-boost switching regulator further comprises:

a first switch that is coupled between the input terminal and a first switching node;

a second switching that is coupled between the first switching node and ground;

an inductor that is coupled between the first switching node and a second switching node;

a third switch that is coupled between the second switching node and ground; and

a fourth switching that is coupled between the second switching node and the output terminal.

3. The apparatus of claim 2, wherein the computer code for operating the buck-boost switching regulator in the first bridge mode when the output of the compensation function is between the predetermined buck gain and the intermediate value further comprises:

computer code for operating the first switch at a first duty cycle having a value that is the difference between the output of the compensation function and a first constant value; and

computer code for operating the third switch at a second duty cycle that is a second constant value, wherein a gain of buck-boost switching regulator, in the first bridge mode, is the product of a third constant and the value of the first duty cycle.

4. The apparatus of claim 3, wherein the computer code for operating the buck-boost switching regulator in the second bridge mode when the output of the compensation function is between the intermediate value and the predetermined boost gain further comprises:

computer code for operating the first switch at a third duty cycle having a fourth constant value; and

computer code for operating the third switch at a fourth duty cycle having a value that is the difference between the output of the compensation function and a fifth constant value, wherein a gain of the buck-boost switching regulator, in the second bridge mode, is the product of the fourth constant value and a difference between a sixth constant value and the output of the compensation function.

5. The apparatus of claim 4, wherein the control circuitry further comprises:

a voltage divider that is coupled to the output terminal; and

an error amplifier that receives a reference voltage and that is coupled to the voltage divider and the processor.

6. The apparatus of claim 4, wherein the processor is a digital signals processor (DSP).

7. A method comprising:

detecting at least one of an input voltage, an output voltage, an input current, and an output current of a buck-boost switching regulator, wherein buck-boost switching regulator includes a predetermined buck gain, a predetermined boost gain, a predetermined dead-time, and a predetermined on-time, and wherein the buck-boost switching regulator includes;

a first switch that is coupled between the input terminal and a first switching node;

a second switching that is coupled between the first switching node and ground;

an inductor that is coupled between the first switching node and a second switching node;

a third switch that is coupled between the second switching node and ground; and

a fourth switching that is coupled between the second switching node and the output terminal;

operating the buck-boost switching regulator in a buck mode when an output of a compensation function is less than the predetermined buck gain, wherein the compensation function determines PWM duty cycles for the buck-boost switching regulator;

operating the buck-boost switching regulator in a first bridge mode when the output of the compensation function is between the predetermined buck gain and an intermediate value;

operating the buck-boost switching regulator in a second bridge mode when the output of the compensation function is between the intermediate value and the predetermined boost gain; and

operating the buck-boost switching regulator in a boost mode when the output of the compensation function is greater than the predetermined boost gain.

8. The apparatus of claim 7, wherein the step of operating the buck-boost switching regulator in the first bridge mode when the output of the compensation function is between the predetermined buck gain and the intermediate value further comprises:

operating the first switch at a first duty cycle having a value that is the difference between the output of the compensation function and a first constant value; and

operating the third switch at a second duty cycle that is a second constant value, wherein a gain of buck-boost switching regulator, in the first bridge mode, is the product of a third constant value and the value of the first duty cycle.

9. The apparatus of claim 8, wherein the step of operating the buck-boost switching regulator in the second bridge mode when the output of the compensation function is between the intermediate value and the predetermined boost gain further comprises:

operating the first switch at a third duty cycle having a fourth constant value; and

operating the third switch at a fourth duty cycle having a value that is the difference between the output of the compensation function and a fifth constant value, wherein a gain of the buck-boost switching regulator, in the second bridge mode, is the product of the fourth constant value and a difference between a sixth constant value and the output of the compensation function.

10. An apparatus comprising:

a solar cell;

a buck-boost switching regulator having an input terminal, an output terminal, a predetermined buck gain, a predetermined boost gain, a predetermined dead-time, and a predetermined on-time, wherein the input terminal is coupled to the solar cell; and

control circuitry that is coupled to the output terminal and that controls the buck-boost switching regulator, wherein the control circuitry employs a compensation function to determine PWM duty cycles for the buck-boost switching regulator, wherein the control circuitry includes a processor and a storage medium with a computer program product embodied thereon, and wherein the computer program product includes;

computer code for operating the buck-boost switching regulator in a buck mode when an output of the compensation function is less than the predetermined buck gain;

computer code for operating the buck-boost switching regulator in a first bridge mode when the output of the compensation function is between the predetermined buck gain and an intermediate value;

computer code for operating the buck-boost switching regulator in a second bridge mode when the output of the compensation function is between the intermediate value and the predetermined boost gain; and

computer code for operating the buck-boost switching regulator in a boost mode when the output of the compensation function is greater than the predetermined boost gain.

11. The apparatus of claim 10, wherein the buck-boost switching regulator further comprises:

a first switch that is coupled between the input terminal and a first switching node;

a second switching that is coupled between the first switching node and ground;

an inductor that is coupled between the first switching node and a second switching node;

a third switch that is coupled between the second switching node and ground; and

a fourth switching that is coupled between the second switching node and the output terminal.

12. The apparatus of claim 11, wherein the computer code for operating the buck-boost switching regulator in the first bridge mode when the output of the compensation function is between the predetermined buck gain and the intermediate value further comprises:

computer code for operating the first switch at a first duty cycle having a value that is the difference between the output of the compensation function and a first constant value; and

computer code for operating the third switch at a second duty cycle that is a second constant value, wherein a gain of buck-boost switching regulator, in the first bridge mode, is the product of a third constant value and the value of the first duty cycle.

13. The apparatus of claim 12, wherein the computer code for operating the buck-boost switching regulator in the second bridge mode when the output of the compensation function is between the intermediate value and the predetermined boost gain further comprises:

computer code for operating the first switch at a third duty cycle having a fourth constant value; and

computer code for operating the third switch at a fourth duty cycle having a value that is the difference between the output of the compensation function and a fifth constant value, wherein a gain of the buck-boost switching regulator, in the second bridge mode, is the product of the fourth constant value and a difference between a sixth constant value and the output of the compensation function.

14. The apparatus of claim 13, wherein the control circuitry further comprises:

a voltage divider that is coupled to the output terminal; and

an error amplifier that receives a reference voltage and that is coupled to the voltage divider and the processor.

15. The apparatus of claim 13, wherein the processor is a DSP.

16. The apparatus of claim 13, wherein the solar cell further comprises a plurality of solar cells.