Amplifiers

Patent metadata

Field	Value
Publication number	US-10177718-B2
Application number	US-201715858173-A
Country	US
Kind code	B2
Filing date	Dec 29, 2017
Priority date	May 8, 2015
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

This application relates to audio amplifier circuitry (100). An amplifier module (103) is located in a signal path between an input (101) and an output (102). A detection module (106) is configured to detect a characteristic of a load (104) electrically coupled, in use, to the output. A distortion setting controller (107) is provided for selecting one of a plurality of stored distortion settings {pi} based on the detected characteristic of the load; and a pre-distortion module (105) is configured to apply a first transfer function to a signal in the signal path prior to said amplifier module. The first transfer function is based on the selected distortion setting and for at least one of the stored distortion settings the corresponding first transfer function comprises a non-linear distortion function.

First claim

What is claimed is:

1. Audio amplifier circuitry for driving an audio load, comprising
an input for receiving an input audio signal and an output for outputting an output audio signal to an audio load electrically coupled, in use, to the output, wherein, in use, different audio loads may be removably coupled to the output via an audio connector;
a storage module for storing a plurality of distortion settings;
a controller for selecting one of the plurality of distortion settings based on an indication of a characteristic of the audio load coupled, in use, to the output; and
a pre-distortion module applying a distortion function to the input audio signal based on the selected distortion setting.

2. Audio amplifier circuitry as claimed in claim 1 wherein at least one of the stored distortion settings comprises a non-linear distortion function.

3. Audio amplifier circuitry as claimed in claim 1 wherein the distortion function is based on a polynomial function and each of the stored distortion settings comprises a set of one or more distortion coefficients for said polynomial function.

4. Audio amplifier circuitry as claimed in claim 3 wherein each distortion setting comprises a set of distortion coefficients characterised for a particular audio load characteristic.

5. Audio amplifier circuitry as claimed in claim 3 wherein at least some distortion coefficients have an associated phase delay component and wherein the pre-distortion module is configured to apply a distortion component corresponding to each distortion coefficient at a respective delay indicated by the respective phase delay component.

6. Audio amplifier circuitry as claimed in claim 1 wherein for one of the stored distortion settings the corresponding distortion function corresponds to substantially no distortion.

7. Audio amplifier circuitry as claimed in claim 1 wherein said characteristic of the audio load is an impedance of the audio load.

8. Audio amplifier circuitry as claimed in claim 7 wherein the controller is configured to compare the impedance of the audio load with one or more threshold values to determine an impedance band for the audio load and to select one of the stored distortion settings that is appropriate for said impedance band.

9. Audio amplifier circuitry as claimed in claim 1 wherein a detection module is coupled to the output of the amplifier circuitry and is configured to determine the characteristic of the audio load through monitoring of the electrical properties at the output when the audio load is connected; wherein the detection module is configured to detect when the audio load is operably connected to the output and then to determine the characteristic of the audio load.

10. Audio amplifier circuitry as claimed in claim 9 wherein, in response to a detection that the audio load has been operably connected to the output, the amplifier circuitry is configured to apply a test stimulus to the output and the detection module is configured to monitor the electrical properties at the output in response to the test stimulus to determine the characteristic of the audio load.

11. Audio amplifier circuitry as claimed in claim 9 wherein the detection module is configured to, in use, continuously or periodically monitor the characteristic of the audio load.

12. Audio amplifier circuitry as claimed in 32 wherein, when the detection module is monitoring the characteristic of the audio load, the amplifier circuitry is configured to add a pilot tone at a pilot tone frequency to the signal in the signal path and the detection module monitors the electrical properties at the output at said pilot tone frequency.

13. Audio amplifier circuitry as claimed in claim 1 wherein the controller is configured such that the selection of the one of the stored plurality of distortion settings is also based on an indication of at least one operating condition of the amplifier circuitry.

14. Audio amplifier circuitry as claimed in claim 1 wherein the controller is configured to modify the selected distortion setting based on an indication of at least one operating condition of the amplifier circuitry.

15. Audio amplifier circuitry as claimed in claim 14 wherein the at least one operating condition of the amplifier circuitry comprises at least one of: temperature of the amplifier circuitry; a supply voltage; a bias current; an amplifier operating mode.

16. Audio amplifier circuitry as claimed in claim 1 wherein the controller is configured, such that, in the event that the selected distortion setting is changed in use, to transition from the old distortion setting to the new distortion setting via at least one intermediate setting value.

17. An electronic device comprising audio amplifier circuitry as claimed in claim 1 wherein the electronic device is at least one of a communications device; a computing device; a portable device; a battery powered device; a wearable device; a gaming device; a mobile telephone; a laptop, notebook or tablet computer.

18. An electronic device comprising:
audio amplifier circuitry;
a connector configured such that, in use, different audio loads can be removably electrically connected to an output of the audio amplifier circuitry;
the audio amplifier circuitry comprising:
an amplifier module for receiving an input digital audio signal and producing an amplified output analogue audio signal; and
a pre-distortion module for applying a first transfer function to the digital audio input signal upstream of the amplifier module;
wherein the first transfer function is variable based on an indication of the impedance of the audio load removably coupled to the output of the audio amplifier circuitry.

19. An electronic device as claimed in claim 18 wherein the connector comprise a jack socket.

20. Audio amplifier circuitry comprising:
an amplifier module located in a signal path between an input and an output;
a detection module for detecting a characteristic of an audio load electrically coupled, in use, to the output via a removable mating connection;
a distortion setting controller for selecting one of a plurality of stored distortion settings based on the detected characteristic of the audio load; and
a pre-distortion module configured to apply a first transfer function to a signal in the signal path prior to said amplifier module, wherein the first transfer function is based on the selected distortion setting.

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Lesso John Paul
• Hardy Emmanuel Philippe Christian

Classifications

• H03F2201/3233

  Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion · CPC title

• H03F2200/03

  the amplifier being designed for audio applications · CPC title

• H03F3/183

  with semiconductor devices only · CPC title

• H04R5/04

  Circuit arrangements, {e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments (combinations of amplifiers H03F3/68; stereophonic systems H04S)} · CPC title

• H04R29/003

  of the moving-coil type · CPC title