Common-mode leakage error calibration for current sensing in a class-D stage using a pilot tone

Patent metadata

Field	Value
Publication number	US-11290070-B2
Application number	US-202016869226-A
Country	US
Kind code	B2
Filing date	May 7, 2020
Priority date	May 7, 2020
Publication date	Mar 29, 2022
Grant date	Mar 29, 2022

Abstract

A system may include a Class-D stage comprising a first high-side switch coupled between a supply voltage and a first output terminal of the Class-D stage, a second high-side switch coupled between the supply voltage and a second output terminal of the Class-D stage, a first low-side switch coupled between a ground voltage and the first output terminal, and a second low-side switch coupled between the ground voltage and the second output terminal. The system may also include current sensing circuitry comprising a sense resistor, such that an output current through a load coupled between the first output terminal and the second output terminal causes a first sense voltage proportional to the output current across the sense resistor. The system may additionally include a modulator for generating a differential pulse-width modulation driving signal to the first high-side switch, the second high-side switch, the first low-side switch, and the second low-side switch and pilot tone injection circuitry configured to inject a periodic pilot tone into the differential pulse-width modulation driving signal at a pilot tone frequency.

First claim

What is claimed is:

1. A system comprising:
a Class-D stage comprising:
a first high-side switch coupled between a supply voltage and a first output terminal of the Class-D stage;
a second high-side switch coupled between the supply voltage and a second output terminal of the Class-D stage;
a first low-side switch coupled between a ground voltage and the first output terminal; and
a second low-side switch coupled between the ground voltage and the second output terminal;

current sensing circuitry comprising a sense resistor, such that an output current through a load coupled between the first output terminal and the second output terminal causes a first sense voltage proportional to the output current across the sense resistor;
a modulator for generating a differential pulse-width modulation driving signal to the first high-side switch, the second high-side switch, the first low-side switch, and the second low-side switch; and
pilot tone injection circuitry configured to inject a periodic pilot tone into the differential pulse-width modulation driving signal at a pilot tone frequency.

2. The system of claim 1 , wherein the sense resistor is coupled between the first output terminal and the second output terminal.

3. The system of claim 1 , wherein:
the modulator comprises ramp generation for generating a periodic triangular waveform signal used to generate the differential pulse-width modulation driving signal; and
the pilot tone injection circuitry is configured to inject the periodic pilot tone into the periodic triangular waveform signal at a pilot tone frequency.

4. The system of claim 1 , wherein the periodic pilot tone has a constant magnitude.

5. The system of claim 1 , wherein the pilot tone frequency is significantly outside a signal frequency for a desired signal played back to the load.

6. The system of claim 1 , wherein injection of the periodic pilot tone causes a modulation of a common mode pulse width of the differential pulse-width modulation driving signal while maintaining a fully-differential pulse width of the differential pulse-width modulation driving signal substantially unchanged as a result of the modulation of the common mode pulse width.

7. The system of claim 1 , further comprising measurement circuitry configured to capture an indication of common-mode leakage of the sense resistor responsive to the periodic pilot tone.

8. A method, in a Class-D stage comprising a first high-side switch coupled between a supply voltage and a first output terminal of the Class-D stage, a second high-side switch coupled between the supply voltage and a second output terminal of the Class-D stage, a first low-side switch coupled between a ground voltage and the first output terminal, and a second low-side switch coupled between the ground voltage and the second output terminal, the method comprising:
sensing current with a sense resistor, such that an output current through a load coupled between the first output terminal and the second output terminal causes a first sense voltage proportional to the output current across the sense resistor;
generating a differential pulse-width modulation driving signal to the first high-side switch, the second high-side switch, the first low-side switch, and the second low-side switch; and
injecting a periodic pilot tone into the differential pulse-width modulation driving signal at a pilot tone frequency.

9. The method of claim 8 , wherein the sense resistor is coupled between the first output terminal and the second output terminal.

10. The method of claim 8 , wherein injecting the pilot tone comprises injecting the periodic pilot tone into a periodic triangular waveform signal used to generate the differential pulse-width modulation driving signal.

11. The method of claim 8 , wherein the periodic pilot tone has a constant magnitude.

12. The method of claim 8 , wherein the pilot tone frequency is significantly outside a signal frequency for a desired signal played back to the load.

13. The method of claim 8 , wherein injection of the periodic pilot tone causes a modulation of a common mode pulse width of the differential pulse-width modulation driving signal while maintaining a fully-differential pulse width of the differential pulse-width modulation driving signal substantially unchanged as a result of the modulation of the common mode pulse width.

14. The method of claim 8 , further comprising capturing an indication of common-mode leakage of the sense resistor responsive to the periodic pilot tone.

15. An amplifier comprising:
an input for receiving an input signal for amplification;
a modulator for receiving the input signal or a signal derived from the input signal and configured to generate a differential pulse-width modulation driving signal as a function of the input signal;
a Class-D stage comprising:
a first high-side switch coupled between a supply voltage and a first output terminal of the Class-D stage;
a second high-side switch coupled between the supply voltage and a second output terminal of the Class-D stage;
a first low-side switch coupled between a ground voltage and the first output terminal; and
a second low-side switch coupled between the ground voltage and the second output terminal;

wherein to the first high-side switch, the second high-side switch, the first low-side switch, and the second low-side switch are configured to receive the differential pulse-width modulation driving signal;
a sense resistor coupled to the Class-D stage, such that an output current through a load coupled between the first output terminal and the second output terminal causes a first sense voltage proportional to the output current across the sense resistor; and
pilot tone injection circuitry configured to inject a periodic pilot tone into the differential pulse-width modulation driving signal at a pilot tone frequency.

16. The amplifier of claim 15 , wherein the sense resistor is coupled between the first output terminal and the second output terminal.

17. The amplifier of claim 15 , wherein:
the modulator comprises a ramp generation circuit for generating a periodic triangular waveform signal used to generate the differential pulse-width modulation driving signal; and
the pilot tone injection circuitry is configured to inject the periodic pilot tone into the periodic triangular waveform signal at a pilot tone frequency.

18. The amplifier of claim 15 , wherein the periodic pilot tone has a constant magnitude.

19. The amplifier of claim 15 , wherein the pilot tone frequency is significantly outside a signal frequency for a desired signal played back to the load.

20. The amplifier of claim 15 , wherein injection of the periodic pilot tone causes a modulation of a common mode pulse width of the differential pulse-width modulation driving signal while maintaining a fully-differential pulse width of the differential pulse-width modulation driving signal substantially unchanged as a result of the modulation of the common mode pulse width.

21. The amplifier of claim 15 , further comprising measurement circuitry configured to capture an indication of common-mode leakage of the sense resistor responsive to the periodic pilot tone.

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Zanbaghi Ramin
• Peterson Cory J
• Kimball Eric

Classifications

• G01R19/0092

  Measuring current only · CPC title

• H03F3/187

  in integrated circuits · CPC title

• H03K7/08 Primary

  Duration or width modulation {; Duty cycle modulation} · CPC title

• H03F2200/351

  Pulse width modulation being used in an amplifying circuit · CPC title

• H03K4/56

  using a semiconductor device with negative feedback through a capacitor, e.g. Miller integrator · CPC title