Audio distortion compensation

Patent metadata

Field	Value
Publication number	US-10778173-B2
Application number	US-201816169723-A
Country	US
Kind code	B2
Filing date	Oct 24, 2018
Priority date	Jul 25, 2018
Publication date	Sep 15, 2020
Grant date	Sep 15, 2020

Abstract

A method for compensating for a change in back electric motive force in a transducer in a device, wherein the transducer is driven by an output signal output by an amplifier, and a back volume of the transducer is formed by an enclosure within the device. The method comprises: receiving an input signal; determining, based on a characteristic of the transducer that the transducer has moved from an equilibrium position within the device; and based on the determination, adjusting a gain applied to the input signal by the amplifier to generate the output signal.

First claim

The invention claimed is:

1. A method for compensating for a change in back electric motive force in a transducer in a device, wherein the transducer is driven by an output signal output by an amplifier, and a back volume of the transducer is formed by an enclosure within the device, the method comprising:
receiving an input signal, wherein the input signal is connected to drive the transducer through the amplifier;
receiving a monitored signal, and determining based on the monitored signal, a first value of the characteristic of the transducer;
determining a predicted value of the characteristic of the transducer based on the output signal;
comparing the first value to the predicted value;
based on the comparison, determining whether the transducer has moved from an equilibrium position within the device; and
based on the determination, adjusting a gain applied to the input signal by the amplifier to generate the output signal.

2. The method of claim 1 wherein the characteristic comprises an excursion of a diaphragm of the transducer.

3. The method of claim 2 wherein the monitored signal comprises a signal received from a laser device positioned to measure the excursion of the diaphragm of the transducer.

4. The method of claim 2 wherein the monitored signal comprises a current signal across the transducer.

5. The method of claim 4 wherein the monitored signal comprises a voltage signal across the transducer.

6. The method of claim 5 wherein the method further comprises calculating the first value based on the current signal and the voltage signal.

7. The method of claim 1 wherein the characteristic comprises an air pressure level in the back volume.

8. The method of claim 7 wherein the monitored signal comprises a real-time measurement of the air pressure in the back volume.

9. The method of claim 8 wherein the monitored signal is received from a pressure sensor.

10. The method of claim 1 wherein the step of comparing comprises:
determining a difference between the first value and the first predicted value,
comparing the difference to a threshold value,
responsive to the difference being greater than the threshold value, determining that the transducer has moved from the equilibrium position, and
responsive to the difference being less than the threshold value, determining that the transducer has not moved from the equilibrium position.

11. The method of claim 1 wherein the step of adjusting a gain comprises:
determining a second predicted value of the characteristic based on the input signal,
determining a third predicted value of the characteristic by adding an offset based on the comparison to the second predicted value; and
adjusting the gain applied to the input signal by the amplifier based on the third predicted value.

12. The method of claim 1 wherein the step of adjusting the gain comprises:
decreasing the gain applied to the input signal by the amplifier responsive to a determination that the transducer has moved from the equilibrium position.

13. A compensation module for compensating for a back electric motive force change in a transducer in a device, wherein the transducer is driven by an output signal output by an amplifier and a back volume of the transducer is formed by an enclosure within the device, the compensation module comprising:
an input for receiving an input signal, wherein the input signal is connected to drive the transducer through the amplifier;
a determination block configured to:
receive a monitored signal;
determine based on the monitored signal a first value of the characteristic of the transducer;
determine a predicted value of the characteristic of the transducer based on the output signal;
compare the first value to the predicted value; and
based on the comparison, determine whether that the transducer has moved from an equilibrium position within the device; and

a gain adjustment block configured to, based on the determination, adjust a gain applied to the input signal by the amplifier to generate the output signal.

14. The compensation module of claim 13 wherein the characteristic comprises an excursion of a diaphragm of the transducer.

15. The compensation module of claim 13 wherein the monitored signal comprises a signal received from a laser device positioned to measure the excursion of the diaphragm of the transducer.

16. The compensation module of claim 13 wherein the monitored signal comprises a current signal across the transducer.

17. The compensation module of claim 16 wherein the monitored signal comprises a voltage signal across the transducer.

18. The compensation module of claim 17 wherein the determination module is further configured to calculate the first value based on the current signal and voltage signals across the transducer.

19. The compensation module of claim 13 wherein the characteristic comprises an air pressure level in the back volume.

20. The compensation module of claim 19 wherein the monitored signal comprises a real time measurement of the air pressure in the back volume.

21. The compensation module of claim 20 wherein the monitored signal is received from a pressure sensor.

22. The compensation module of claim 13 wherein determination block comprises a comparison block configured to:
determine a difference between the first value and the predicted value, and
compare the difference to a threshold value, wherein
responsive to the difference being greater than the threshold value, the determination block is configured to determine that the transducer has moved from the equilibrium position, and
responsive to the difference being less than the threshold value, the determination block is configured to determine that the transducer has not moved from the equilibrium position.

23. The compensation module of claim 13 wherein the gain adjustment block is configured to:
determine a second predicted value of the characteristic based on the input signal,
determine a third predicted value of the characteristic by adding an offset based on the comparison to the second predicted value; and
adjust the gain applied to the input signal by the amplifier based on the third predicted value.

24. The compensation module of claim 13 wherein the gain adjustment block is configured to:
decrease the gain applied to the input signal by the amplifier responsive to a determination that the transducer has moved from the equilibrium position.

25. An integrated circuit comprising:
a compensation module for compensating for a back electric motive force change in a transducer in a device, wherein the transducer is driven by an output signal output by an amplifier, and a back volume of the transducer is formed by an enclosure within the device, the compensation module comprising:
an input for receiving an input signal, wherein the input signal is connected to drive the transducer through the amplifier;
a determination block configured to:
receive a monitored signal;
determine based on the monitored signal a first value of the characteristic of the transducer;
determine a predicted value of the characteristic of the transducer based on the output signal;
compare the first value to the predicted value; and
based on the comparison, determine whether that the transducer has moved from an equilibrium position within the device; and

a gain adjustment block configured to, based on the determination, adjus

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Zhu Hezi
• Napoli Roberto
• Su Jie
• Eshmawy Waleed

Classifications

• H04R3/002 Primary

  Damping circuit arrangements for transducers, e.g. motional feedback circuits · CPC title

• H03F1/3247

  using feedback acting on predistortion circuits (H03F1/3264 takes precedence) · CPC title

• H04R3/007

  Protection circuits for transducers · CPC title

• H03G3/005

  Control by a pilot signal (H03G3/001 takes precedence) · CPC title

• H04R29/001

  for loudspeakers (H04R29/007 takes precedence) · CPC title