Loudspeaker protection circuitry and methods

Patent metadata

Field	Value
Publication number	US-9794687-B2
Application number	US-201514867758-A
Country	US
Kind code	B2
Filing date	Sep 28, 2015
Priority date	Sep 28, 2015
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

This application relates to methods and apparatus for thermal protection of a loudspeaker ( 102 ). A controller ( 106 ) is configured to generate a control signal (G mod ) for modulating the gain of a signal processing chain ( 101 ) that drives the loudspeaker. The controller is configured such that the control signal is generated as a function of each of: an indication of voice coil temperature of the loudspeaker (T VC ); an indication of power dissipation in the voice coil of the loudspeaker (P VC ); and an indication of a reservoir temperature (T res ) of a thermal reservoir for heat flow from the voice coil. The reservoir temperature may be an ambient temperature of the environment or a temperature of a component of the loudspeaker or apparatus that acts as a heat sink.

First claim

What is claimed is:

1. A system for thermal protection of a loudspeaker comprising:
a controller configured to generate a control signal for modulating the gain of a signal processing chain driving said loudspeaker,
wherein said controller is configured such that the control signal is generated as a function of each of:
an indication of voice coil temperature of the loudspeaker;
an indication of power dissipation in the voice coil of the loudspeaker; and
an indication of a reservoir temperature of a thermal reservoir for heat flow from the voice coil, and
wherein the controller is configured to receive a signal obtained by monitoring a voltage applied to the loudspeaker and a signal obtained by monitoring a current in the loudspeaker,
wherein the controller is configured to use said received signals to obtain at least one of the indication of voice coil temperature of the loudspeaker, the indication of power dissipation in the voice coil of the loudspeaker, and the indication of a reservoir temperature of a thermal reservoir for heat flow from the voice coil, and
wherein the controller comprises:
a power limit module configured to determine an allowed power function of an allowed power dissipation with voice coil temperature based on said indication of a reservoir temperature; and
a gain calculation module configured to determine a gain setting based on the indication of power dissipation in the voice coil and the allowed power function, and

wherein said control signal is based on said gain setting.

2. A system as claimed in claim 1 comprising an estimation module configured to determine said indication of reservoir temperature based on said indication of power dissipation of the voice coil.

3. A system as claimed in claim 1 wherein the indication of a reservoir temperature is an indication of an ambient temperature for the loudspeaker.

4. A system as claimed in claim 1 wherein the indication of a reservoir temperature is an indication of the temperature of a component of the loudspeaker other than the voice coil.

5. A system as claimed in claim 1 comprising a gain element for applying a gain to the input signal, said gain element being controlled by said controller wherein said controller controls the gain of said gain element based on said control signal and at least one other gain setting.

6. A system as claimed in claim 1 wherein said controller further comprises an excursion limiting module configured to generate a second gain setting for excursion limiting of the loudspeaker.

7. An electronic apparatus comprising a system as claimed in claim 1 .

8. A system as claimed in claim 1 wherein the power limit module is configured to determine the allowed power function such that the allowed power dissipation at a maximum allowed temperature of the voice coil depends on said indication of a reservoir temperature.

9. A system as claimed in claim 8 wherein the power limit module is configured to determine the allowed power function such that the allowed power dissipation at the maximum allowed temperature corresponds to a power dissipation that leads to a substantially steady state temperature of the voice coil at the relevant reservoir temperature.

10. A system as claimed in claim 1 wherein the power limit module is configured to determine the allowed power function for a voice coil temperature range between a threshold temperature and said maximum allowed temperature.

11. A system as claimed in claim 10 wherein the power limit module is configured to determine the allowed power function such that for any voice coil temperature below a the threshold temperature no limit on allowed power is applied.

12. A system as claimed in claim 10 wherein the power limit module is configured to determine the allowed power function such that the allowed power dissipation at the threshold temperature is based on said indication of power dissipation in the voice coil of the loudspeaker.

13. A system as claimed in claim 1 wherein the gain calculation module is configured to determine the gain setting based on an allowed power dissipation determined according to the allowed power function and the indication of power dissipation in the voice coil according to a gain control transfer function,
wherein the gain control transfer function varies the gain setting from a first gain setting at a first value of power dissipation in the voice coil of the loudspeaker to a second gain setting at a second value of power dissipation in the voice coil, wherein the first gain setting corresponds to a maximum gain setting and the second gain setting corresponds to a lower gain setting, and
wherein the second value of power dissipation in the voice coil corresponds to the allowed power dissipation and the second gain setting corresponds to a gain setting that would lead to a power dissipation substantially equal to the allowed power dissipation if an input signal to the signal processing chain driving said loudspeaker was at a maximum level.

14. A system for thermal protection of a loudspeaker comprising:
a controller configured to generate a control signal for modulating the gain of a signal processing chain driving said loudspeaker,
wherein said controller is configured such that the control signal is generated as a function of each of:
an indication of voice coil temperature of the loudspeaker;
an indication of power dissipation in the voice coil of the loudspeaker; and
an indication of a reservoir temperature of a thermal reservoir for heat flow from the voice coil,

wherein the controller comprises:
a power limit module configured to determine an allowed power function of an allowed power dissipation with voice coil temperature based on said indication of a reservoir temperature; and
a gain calculation module configured to determine a gain setting based on the indication of power dissipation in the voice coil and the allowed power function,
wherein said control signal is based on said gain setting.

15. A system as claimed in claim 14 wherein the power limit module is configured to determine the allowed power function such that the allowed power dissipation at a maximum allowed temperature of the voice coil depends on said indication of a reservoir temperature.

16. A system as claimed in claim 15 wherein the power limit module is configured to determine the allowed power function such that the allowed power dissipation at the maximum allowed temperature corresponds to a power dissipation that leads to a substantially steady state temperature of the voice coil at the relevant reservoir temperature.

17. A system as claimed in claim 14 wherein the power limit module is configured to determine the allowed power function for a voice coil temperature range between a threshold temperature and said maximum allowed temperature.

18. A system as claimed in claim 17 wherein the power limit module is configured to determine the allowed power function such that for any voice coil temperature below a the threshold temperature no limit on allowed power is applied.

19. A system as claimed in claim 17 wherein the power limit module is configured to determine the allowed power function such that the allowed power dissipation at the threshold temperature is based on said indication of power dissipation in the voice coil of the loudspeaker.

20. A system as claimed in claim 14 wherein the gain calculation module is configured to determine the gain setting based on an allowed power dissipation determined according to the allowed power fu

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Napoli Roberto
• Lawrence Jason William

Classifications

• H04R3/007 Primary

  Protection circuits for transducers · CPC title

• H04R2430/01

  Aspects of volume control, not necessarily automatic, in sound systems · CPC title

• H03G3/3005

  in amplifiers suitable for low-frequencies, e.g. audio amplifiers (H03G3/32, H03G3/34 take precedence) · CPC title

• H04R29/003

  of the moving-coil type · CPC title

• H03F1/52

  Circuit arrangements for protecting such amplifiers {(monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74)} · CPC title