Chopped triangular wave PWM quantizer

Patent metadata

Field	Value
Publication number	US-10659029-B2
Application number	US-201816163638-A
Country	US
Kind code	B2
Filing date	Oct 18, 2018
Priority date	Oct 14, 2018
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

An apparatus in a PWM modulator includes a triangular wave generator that generates a triangular wave and a comparator that is responsive to a signal input to generate a signal output. An output of the PWM modulator is responsive to the comparator signal output. A polarity inversion circuit, coupled between the triangular wave generator and the comparator, is configured in one of the following ways: to provide the triangular wave to the comparator when the triangular wave has a first slope polarity and to provide a polarity-inverted version of the triangular wave to the comparator when the triangular wave has a second slope polarity opposite the first slope polarity; and to provide the signal input to the comparator when the triangular wave has the first slope polarity and to provide a polarity-inverted version of the signal input to the comparator when the triangular wave has the second slope polarity.

First claim

The invention claimed is:

1. An apparatus in a pulse width modulation (PWM) modulator, comprising:
a triangular wave generator that generates a triangular wave;
a comparator that is responsive to a signal input to generate a signal output, wherein an output of the PWM modulator is responsive to the comparator signal output;
a polarity inversion circuit coupled to the comparator;
wherein the polarity inversion circuit is configured in one of the following ways:
to provide the triangular wave to the comparator when the triangular wave has a first slope polarity and to provide a polarity-inverted version of the triangular wave to the comparator when the triangular wave has a second slope polarity opposite the first slope polarity; and
to provide the signal input to the comparator when the triangular wave has the first slope polarity and to provide a polarity-inverted version of the signal input to the comparator when the triangular wave has the second slope polarity; and

wherein the polarity-inversion circuit comprises a de-chopping switch.

2. The apparatus of claim 1 ,
wherein the triangular wave generator generates the triangular wave having a period; and
wherein the polarity inversion circuit provides the triangular wave/signal input and the polarity-inverted version of the triangular wave/signal input to the comparator during respective halves of the period.

3. The apparatus of claim 2 ,
wherein the triangular wave period corresponds to twice a period of a PWM signal generated by the PWM modulator.

4. The apparatus of claim 2 ,
wherein the triangular wave generator comprises a chopping switch that selectively couples respective opposite polarity reference current sources to respective opposite polarity inputs of an operational amplifier on alternating periods of the triangular wave.

5. The apparatus of claim 4 ,
wherein the triangular wave generator is configured to reset the inputs of the operational amplifier to a common mode voltage at a beginning and at a middle of the period of the triangular wave.

6. The apparatus of claim 2 ,
wherein the triangular wave comprises a differential voltage having positive and negative portions; and
wherein the triangular wave generator is configured to reset the positive and negative portions of the triangular wave differential voltage to respective positive and negative reference voltages on alternating periods of the triangular wave.

7. A method, comprising:
in a pulse width modulation (PWM) modulator including a triangular wave generator that generates a triangular wave, a comparator that is responsive to a signal input to generate a signal output, wherein an output of the PWM modulator is responsive to the comparator signal output, and a polarity inversion circuit coupled to the comparator:
performing one of the following actions by the polarity inversion circuit:
providing the triangular wave to the comparator when the triangular wave has a first slope polarity and providing a polarity-inverted version of the triangular wave to the comparator when the triangular wave has a second slope polarity opposite the first slope polarity; and
providing the signal input to the comparator when the triangular wave has the first slope polarity and providing a polarity-inverted version of the signal input to the comparator when the triangular wave has the second slope polarity; and

wherein the polarity-inversion circuit comprises a de-chopping switch.

8. The method of claim 7 , further comprising:
generating, by the triangular wave generator, the triangular wave having a period; and
providing, by the polarity inversion circuit, the triangular wave/signal input and the polarity-inverted version of the triangular wave/signal input to the comparator during respective halves of the period.

9. The method of claim 8 ,
wherein the triangular wave period corresponds to twice a period of a PWM signal generated by the PWM modulator.

10. The method of claim 8 , further comprising:
wherein the triangular wave generator comprises a chopping switch; and
selectively coupling, by the chopping switch, respective opposite polarity reference current sources to respective opposite polarity inputs of an operational amplifier on alternating periods of the triangular wave.

11. The method of claim 10 ,
resetting, by the triangular wave generator, the inputs of the operational amplifier to a common mode voltage at a beginning and at a middle of the period of the triangular wave.

12. The method of claim 8 , further comprising:
wherein the triangular wave comprises a differential voltage having positive and negative portions; and
resetting, by the triangular wave generator, the positive and negative portions of the triangular wave differential voltage to respective positive and negative reference voltages on alternating periods of the triangular wave.

13. An apparatus in a pulse width modulation (PWM) modulator, comprising:
a triangular wave generator that generates a triangular wave;
a comparator that is responsive to a signal input to generate a signal output, wherein an output of the PWM modulator is responsive to the comparator signal output;
a polarity inversion circuit coupled to the comparator;
wherein the polarity inversion circuit is configured in one of the following ways:
to provide the triangular wave to the comparator when the triangular wave has a first slope polarity and to provide a polarity-inverted version of the triangular wave to the comparator when the triangular wave has a second slope polarity opposite the first slope polarity; and
to provide the signal input to the comparator when the triangular wave has the first slope polarity and to provide a polarity-inverted version of the signal input to the comparator when the triangular wave has the second slope polarity; and

wherein the triangular wave generator generates the triangular wave having a period;
wherein the polarity inversion circuit provides the triangular wave/signal input and the polarity-inverted version of the triangular wave/signal input to the comparator during respective halves of the period; and
wherein the triangular wave generator comprises a chopping switch that selectively couples respective opposite polarity reference current sources to respective opposite polarity inputs of an operational amplifier on alternating periods of the triangular wave.

14. The apparatus of claim 13 ,
wherein the triangular wave period corresponds to twice a period of a PWM signal generated by the PWM modulator.

15. The apparatus of claim 14 ,
wherein the triangular wave generator is configured to reset the inputs of the operational amplifier to a common mode voltage at a beginning and at a middle of the period of the triangular wave.

16. The apparatus of claim 13 ,
wherein the triangular wave comprises a differential voltage having positive and negative portions; and
wherein the triangular wave generator is configured to reset the positive and negative portions of the triangular wave differential voltage to respective positive and negative reference voltages on alternating periods of the triangular wave.

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Zanbaghi Ramin
• Parsi Anuradha
• Lee Kyehyung
• Melanson John L

Classifications

• H03F2200/331

  Sigma delta modulation being used in an amplifying circuit · CPC title

• H03F3/187 Primary

  in integrated circuits · CPC title

• H03M3/442

  by restricting the swing within the loop, e.g. gain scaling · CPC title

• H03F3/217

  Class D power amplifiers; Switching amplifiers · CPC title

• H03F3/185

  with field-effect devices (H03F3/187 takes precedence) · CPC title