Power mitigation for loudspeaker amplifiers

Patent metadata

Field	Value
Publication number	US-10469044-B1
Application number	US-201715850921-A
Country	US
Kind code	B1
Filing date	Dec 21, 2017
Priority date	Dec 21, 2017
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

A power mitigation algorithm in a loudspeaker amplification system that includes a loudspeaker driver, an audio amplifier, and a constant output power, power supply. A power requirement for the amplifier to output an audio signal is determined. A gain adjustment signal is then determined based on a difference between the power requirement and a power budget of the amplifier. Gain of the audio signal is adjusted according to the gain adjustment signal, for output through the loudspeaker driver. As a result, a peak level of the power consumption of the amplifier while outputting the gain-adjusted audio signal becomes less than the power budget. Other embodiments are also described and claimed.

First claim

What is claimed is:

1. A method for performing a power mitigation algorithm at a loudspeaker amplification system that comprises i) a loudspeaker driver for outputting a first audio signal, ii) a first amplifier, and iii) a power supply that provides power to elements of the loudspeaker amplification system including the first amplifier, the method comprising:
receiving, by a processor, a first audio signal;
computing a power requirement, based on processing the first audio signal, for the first amplifier to drive the loudspeaker driver with the first audio signal;
determining a gain adjustment signal based on a difference between the power requirement and a power budget, wherein the power budget is available power from the power supply for the first amplifier to drive the loudspeaker; and
adjusting a gain of the first audio signal according to the gain adjustment signal, to produce a gain-adjusted first audio signal, wherein the gain-adjusted first audio signal is then output through the loudspeaker driver, and wherein power delivered to the first amplifier during outputting of the gain-adjusted first audio signal is less than the power budget of the first amplifier.

2. The method of claim 1 wherein computing the power requirement comprises processing the first audio signal to determine, for each of a plurality of overlapping time intervals of different sizes, an average of a determined plurality of instantaneous power requirements to supply the first amplifier to output the first audio signal over the overlapping time interval.

3. The method of claim 2 wherein the received first audio signal is an audio driver input signal in voltage domain, the method further comprising determining the plurality of instantaneous power requirements by:
applying a loudspeaker driver admittance filter, which represents input admittance of the loudspeaker driver, to transform the audio driver input signal in the voltage domain into an audio driver instantaneous current signal; and
multiplying the audio driver instantaneous current signal by the audio driver input voltage signal.

4. The method of claim 2 , wherein determining the gain adjustment signal comprises
determining, for each of the plurality of overlapping time intervals, a difference between the determined average and the power budget,
wherein the largest determined difference, and not any others of the determined differences, is used to determine the gain adjustment signal.

5. The method of claim 4 , wherein the first audio signal comprises audio in a first frequency band,
wherein the loudspeaker amplification system further comprises a plurality of additional loudspeaker drivers, each configured to output audio in a second frequency band that is higher than the first frequency band.

6. The method of claim 1 , wherein the first audio signal comprises audio in a first frequency band and the loudspeaker amplification system further comprises a plurality of additional loudspeaker drivers each configured for audio output in a second frequency band that is higher than the first frequency band, and wherein the power budget is a first power budget and the gain adjustment signal is a first gain adjustment signal, the method further comprising:
receiving a plurality of second audio signals, one for each of the plurality of additional loudspeaker drivers;
determining, based on the plurality of second audio signals, a total power requirement for the plurality of second amplifiers to drive the plurality of additional loudspeaker drivers with the plurality of second audio signals;
determining a second gain adjustment signal based on a difference between the total power requirement and a second power budget; and
adjusting a gain of each of the plurality of second audio signals according to the second gain adjustment signal to produce a plurality of gain-adjusted second audio signals with which the additional loudspeaker drivers are driven by the second amplifiers.

7. The method of claim 6 wherein determining the total power requirement comprises:
determining for each of a plurality of overlapping time intervals of different sizes an average of a plurality of determined instantaneous total power requirements, to supply the second amplifiers to output the plurality of second audio signals over the overlapping time interval, and
determining, for each of the plurality of overlapping time intervals, a difference between i) the average of the plurality of determined instantaneous total power requirements and ii) the second power budget,
and wherein determining the second gain adjustment signal is based on the largest difference.

8. The method of claim 1 , wherein the first audio signal comprises audio in a first frequency band and the loudspeaker amplification system further comprises a plurality of additional loudspeaker drivers each configured for audio in a second frequency band that is higher than the first frequency band, and wherein the power budget is a first power budget and the gain adjustment signal is a first gain adjustment signal, the method further comprising:
receiving a plurality of second audio signals, one for each of the plurality of additional loudspeaker drivers; and
determining, based on the plurality of second audio signals, a total power requirement for the plurality of second amplifiers to drive the plurality of additional loudspeaker drivers with the plurality of second audio signals,
and wherein the first power budget comprises a difference between i) a constant output power rating of the power supply and ii) the total power requirement for the second amplifiers.

9. An article of manufacture comprising a non-transitory machine-readable medium having instructions stored therein that when executed by a processor of an audio amplification system having i) a loudspeaker driver for outputting an audio signal, ii) a first amplifier, and iii) a power supply that provides power to elements of the loudspeaker amplification system including the first amplifier,
receive an audio signal,
compute a power requirement, based on processing the audio signal, for the first amplifier to drive the loudspeaker driver with the audio signal,
determine a gain adjustment signal based on a difference between the power requirement and a power budget, wherein the power budget is available power from the power supply for the first amplifier to drive the loudspeaker, and
adjust gain of the audio signal according to the gain adjustment signal, to produce a gain-adjusted audio signal that is to be output through the loudspeaker driver.

10. The article of manufacture of claim 9 wherein the received audio signal is an audio driver input voltage signal, and wherein to compute the power requirement the processor is to:
determine a plurality of instantaneous power requirements by applying a loudspeaker driver admittance filter, which represents input admittance of the loudspeaker driver, to transform the audio driver input voltage signal into an audio driver instantaneous current signal, and
multiply the audio driver instantaneous current signal by the audio driver input voltage signal.

11. The article of manufacture of claim 9 , wherein to determine the power requirement, the processor is to:
determine, for each of a plurality of overlapping time intervals of different sizes, an average of a plurality of determined instantaneous power requirements to supply the first amplifier to output the audio signal over the overlapping time interval.

12. The article of manufacture of claim 11 , wherein to determine the gain adjustment signal, the processor is to:
determine, for each of the plurality of overlapping time intervals, a differenc

Assignees

• Apple Inc

Inventors

• Hollabaugh James M
• Breitschaedel Hannes
• Sumberg David A

Classifications

• H04R2430/03

  Synergistic effects of band splitting and sub-band processing · CPC title

• H04R2430/01

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

• H04R2420/07

  Applications of wireless loudspeakers or wireless microphones · CPC title

• H04R2203/12

  Beamforming aspects for stereophonic sound reproduction with loudspeaker arrays · CPC title

• H04R2201/401

  2D or 3D arrays of transducers · CPC title