Loudspeaker protection systems and methods

Patent metadata

Field	Value
Publication number	US-10219074-B2
Application number	US-201815878659-A
Country	US
Kind code	B2
Filing date	Jan 24, 2018
Priority date	Jan 25, 2017
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

A method of thermal protection of a voice coil of a loudspeaker comprises: determining an estimate of a temperature of the voice coil, determining an estimate of a rate of change of the temperature of the voice coil, determining an estimate of power dissipation in the voice coil, and generating a gain control signal for modulating a gain applied to an input signal in a signal path between an input terminal and the loudspeaker. The gain control signal is generated as a function of all of the estimate of the temperature of the voice coil, the estimate of the rate of change of the temperature of the voice coil, and the estimate of the power dissipation in the voice coil.

First claim

The invention claimed is:

1. A method of thermal protection of a voice coil of a loudspeaker comprising:
determining an estimate of a temperature of the voice coil,
determining an estimate of a rate of change of the temperature of the voice coil,
determining an estimate of power dissipation in the voice coil, and
generating a gain control signal for modulating a gain applied to an input signal in a signal path between an input terminal and said loudspeaker,
wherein the gain control signal is generated by:
based on the estimate of the rate of change of the temperature of the voice coil, setting a threshold power value,
based on the threshold power value and on the estimate of the temperature of the voice coil, setting an allowed power value, and
based on the allowed power value and the estimate of power dissipation in the voice coil, generating the gain control signal for modulating the gain applied to the input signal in the signal path between the input terminal and said loudspeaker.

2. A method according to claim 1 , comprising, when the estimate of the rate of change of the temperature of the voice coil is below a threshold value, setting the threshold power value to be a predetermined maximum power value to be applied to said loudspeaker.

3. A method according to claim 1 , comprising:
setting the allowed power value as a result of a predetermined relationship between the threshold power value and the estimate of the temperature of the voice coil.

4. A method according to claim 3 , wherein the predetermined relationship between the threshold power value and the estimate of the temperature of the voice coil is an inverse linear relationship.

5. A method as claimed in claim 1 , wherein said estimate of voice coil temperature is based on:
the difference between the value of said estimated voice coil resistance and a reference resistance value at a known temperature; and
a temperature coefficient for the loudspeaker voice coil.

6. A method as claimed in claim 5 wherein at least one of said temperature coefficient and said reference resistance value is determined in a calibration step.

7. A method as claimed in claim 1 , comprising determining a succession of estimates of the temperature of the voice coil, and determining a succession of estimates of the rate of change of the temperature of the voice coil, wherein each estimate of the rate of change of the temperature of the voice coil is obtained from two successive estimates of the temperature of the voice coil.

8. A method as claimed in claim 1 , wherein said estimate of power dissipation is based on said estimated voice coil resistance and said monitored current.

9. A method as claimed in claim 8 wherein said estimate of power dissipation is determined by multiplying said estimated voice coil resistance by the square of the value of said monitored current.

10. A method as claimed in claim 1 , comprising applying a first transfer function to said estimate of voice coil temperature to determine an allowed power limit, wherein the value of said gain control signal is a function of said allowed power limit.

11. An electronic apparatus comprising a processor, and memory containing suitable software code for performing the method of claim 1 .

12. An electronic apparatus as claimed in claim 11 wherein said apparatus is at least one of: a portable device; a battery power device; a computing device; a communications device; a gaming device; a mobile telephone; a personal media player; a laptop, tablet or notebook computing device.

13. A method of thermal protection of a voice coil of a loudspeaker comprising:
determining an estimate of a temperature of the voice coil,
determining an estimate of a rate of change of the temperature of the voice coil,
determining an estimate of power dissipation in the voice coil, and
generating a gain control signal for modulating a gain applied to an input signal in a signal path between an input terminal and said loudspeaker,
wherein,
when the estimate of the temperature is below a threshold temperature, the gain control signal is generated by:
based on the estimate of the rate of change of the temperature of the voice coil, setting a threshold power value,
based on the threshold power value and on the estimate of the temperature of the voice coil, setting an allowed power value, and
based on the allowed power value and the estimate of power dissipation in the voice coil, generating the gain control signal for modulating the gain applied to the input signal in the signal path between the input terminal and said loudspeaker; and,

when the estimate of the temperature is above a threshold temperature, the gain control signal is generated by:
based on a separate threshold power value and on the estimate of the temperature of the voice coil, setting an allowed power value, and

based on the allowed power value and the estimate of power dissipation in the voice coil, generating the gain control signal for modulating the gain applied to the input signal in the signal path between the input terminal and said loudspeaker.

14. A method of thermal protection of a voice coil of a loudspeaker comprising:
determining an estimate of a temperature of the voice coil,
determining an estimate of a rate of change of the temperature of the voice coil,
determining an estimate of power dissipation in the voice coil, and
generating a gain control signal for modulating a gain applied to an input signal in a signal path between an input terminal and said loudspeaker,
wherein,
(a) when the estimate of the temperature is below a threshold temperature, the gain control signal is generated by:
based on the estimate of the rate of change of the temperature of the voice coil, setting a threshold power value,
based on the threshold power value and on the estimate of the temperature of the voice coil, setting an allowed power value, and
based on the allowed power value and the estimate of power dissipation in the voice coil, generating the gain control signal for modulating the gain applied to the input signal in the signal path between the input terminal and said loudspeaker;

(b) when the estimate of the temperature is above a threshold temperature and the estimate of the rate of change of the temperature of the voice coil is above a rate threshold, the gain control signal is generated by:
based on the estimate of the rate of change of the temperature of the voice coil, setting a threshold power value,
based on the threshold power value and on the estimate of the temperature of the voice coil, setting an allowed power value, and
based on the allowed power value and the estimate of power dissipation in the voice coil, generating the gain control signal for modulating the gain applied to the input signal in the signal path between the input terminal and said loudspeaker; and

(c) when the estimate of the temperature is above a threshold temperature and the estimate of the rate of change of the temperature of the voice coil is below a rate threshold, the gain control signal is generated by:
based on an alternative threshold power value and on the estimate of the temperature of the voice coil, setting an allowed power value, and

based on the allowed power value and the estimate of power dissipation in the voice coil, generating the gain control signal for modulating the gain applied to the input signal in the signal path between the input terminal and said loudspeaker.

15. A method according to claim 14 , comprising:
setting the allowed power value as a result of a predetermined relationship between the threshold power

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Napoli Roberto
• Williams Stefan

Classifications

• H03G3/3005

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

• H04R29/001

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

• G10L25/21

  the extracted parameters being power information · CPC title

• H04R3/007 Primary

  Protection circuits for transducers · CPC title

• H04R29/003

  of the moving-coil type · CPC title