Delta Sigma Modulator with Unavailable Output Values

• US 20090191837A1
• Filed: 09/30/2008
• Published: 07/30/2009
• Est. Priority Date: 01/30/2008
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John L., Nanda, Kartik
• Granted Patent: US 7,755,525 B2
• Time in Patent Office: Days
• US Class Current: 455/334
• CPC Class Codes: H02M 3/157 with digital control

Abstract

A power control system includes a delta sigma modulator to generate output values for use in controlling a switching power converter. In at least one embodiment, the delta sigma modulator includes two ranges of available output values and a range of one or more unavailable intermediate output values, wherein the range of one or more unavailable intermediate output values represent a gap in available output values. Each unavailable intermediate output value represents an output value that is not generated by the delta sigma modulator. In at least one embodiment, the delta sigma modulator includes a quantizer output remapping module that remaps quantizer output values within the range of one or more unavailable intermediate output values of the delta sigma modulator to new output values within one of the ranges of available output values.

Claims

1. An apparatus comprising:

a delta sigma modulator having two ranges of available output values and a range of one or more unavailable intermediate output values, wherein the range of one or more unavailable intermediate output values represent a gap in available output values and represents output values that are unavailable for use in generating a duty cycle modulated control signal to control a switch of a switching power converter; and

a duty cycle modulator, coupled to the delta sigma modulator, to receive the available output values from the delta sigma modulator and to generate the duty cycle modulated control signal to control the switch of the switching power converter.

2. The apparatus of claim 1 wherein the delta sigma modulator comprises:

a quantizer to generate quantizer output values; and

a remapping module to receive the quantizer output values and to remap quantizer output values having values in the range of unavailable intermediate output values to output values in at least one of the available output value ranges.

3. The apparatus of claim 2 wherein the delta sigma modulator includes a quantizer and the remapping module is further configured to provide remapped quantizer output values as quantizer feedback values.

4. The apparatus of claim 1 wherein each of the one or more unavailable intermediate output values is greater than each available output value in a first of the two ranges of available output values and each of the one or more unavailable intermediate output values is less than each available output value in a second of the two ranges of available output values.

5. The apparatus of claim 1 wherein the range of unavailable intermediate output values corresponds to a zero power zone for the switching power converter.

6. The apparatus of claim 5 wherein the zero power zone is a zone ranging from zero power to a power level that is less than fifty percent of a maximum output power of the switching power converter.

7. The apparatus of claim 1 wherein the delta sigma modulator includes multiple ranges of unavailable intermediate output values.

8. The apparatus of claim 1 wherein the range of unavailable intermediate output values correspond to a range of power output levels of the switching power converter.

9. The apparatus of claim 8 wherein the range of power output levels is from approximately zero power to less than or equal to approximately ten percent of maximum output power of the switching power converter.

10. The apparatus of claim 1 wherein the switching power converter is selected from a group consisting of a boost converter, a buck converter, and a boost/buck converter.

11. The apparatus of claim 1 wherein the delta sigma modulator is a nonlinear delta sigma modulator.

12. The apparatus of claim 1 wherein one of the ranges of available output values consists of a single output value, and the single output value is less than each of the one or more unavailable intermediate output values.

13. A method comprising:

generating output values with a delta sigma modulator, wherein (i) the output values of the delta sigma modulator include two ranges of available output values and a range of one or more unavailable intermediate output values and (ii) the range of one or more unavailable intermediate output values represents a gap in available output values and represents output values that are unavailable for use in generating a duty cycle modulated control signal to control a switch of a switching power converter; and

generating the duty cycle modulated control signal to control the switch of the switching power converter using the available output values of the delta sigma modulator.

14. The method of claim 13 wherein generating output values with a delta sigma modulator further comprises:

generating quantizer output values;

receiving the quantizer output values;

remapping quantizer output values having values in the range of unavailable intermediate output values to output values in at least one of the available output value ranges.

15. The method of claim 14 further comprising:

providing remapped quantizer output values as quantizer feedback values to the delta sigma modulator.

16. The method of claim 13 wherein each of the one or more unavailable intermediate output values is greater than each available output value in a first of the two ranges of available output values and each of the one or more unavailable intermediate output values is less than each available output value in a second of the two ranges of available output values.

17. The method of claim 13 wherein the range of unavailable intermediate output values corresponds to a zero power zone for the switching power converter.

18. The method of claim 17 wherein the zero power zone is a zone ranging from zero power to a power level that is less than fifty percent of a maximum output power of the switching power converter.

19. The method of claim 13 wherein the delta sigma modulator includes multiple ranges of unavailable intermediate output values.

20. The method of claim 13 wherein the range of unavailable intermediate output values correspond to a range of power output levels of the switching power converter.

21. The method of claim 20 wherein the range of power output levels is from approximately zero power to less than or equal to approximately ten percent of maximum output power of the switching power converter.

22. The method of claim 13 wherein the switching power converter is selected from a group consisting of a boost converter, buck converter, and boost/buck converter.

23. The method of claim 13 wherein the delta sigma modulator is a nonlinear delta sigma modulator.

24. The method of claim 13 wherein one of the ranges of available output values consists of a single output value, and the single output value is less than each of the one or more unavailable intermediate output values.

25. An apparatus comprising:

means for generating output values with a delta sigma modulator, wherein the output values of the delta sigma modulator include two ranges of available output values and a range of one or more unavailable intermediate output values, wherein the range of one or more unavailable intermediate output values represents a gap in available output values and represents output values that are unavailable for use in generating a duty cycle modulated control signal to control a switch of a switching power converter; and

means for generating the duty cycle modulated control signal to control the switch of the switching power converter using the available output values of the delta sigma modulator.