Control of a loudspeaker output

• US 9,485,576 B2
• Filed: 03/19/2015
• Issued: 11/01/2016
• Est. Priority Date: 02/15/2011
• Status: Active Grant

• Current Assignee: Goodix Technology Co., Ltd. (Shenzhen Goodix Technology Co., Ltd.)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Gautama, Temujin, Hedebouw, Bram
• Primary Examiner(s): CHIN, VIVIAN C
• Assistant Examiner(s): Odunukwe, Ubachukwu
• Application Number:
  US14/663,046
• Publication Number:
  US 20160073196A1
• Time in Patent Office: 593 Days
• Field of Search: 381/55, 381/59, 381/96, 381/71.12, 381/71, 381/12, 700/94, 330/85, 330/279
• US Class Current: 1/1
• CPC Class Codes: H04L 25/06 Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
• CPC Class Codes: H04R 3/002 Damping circuit arrangements for transducers, e.g. motional feedback circuits
• CPC Class Codes: H04R 3/007 Protection circuits for transducers

Abstract

A loudspeaker drive circuit comprises an input for receiving an audio signal and a signal processor for processing the audio signal before application to the loudspeaker. The signal processor processes the audio signal to derive a loudspeaker drive signal which results in the loudspeaker membrane reaching its maximum displacement in both directions of diaphragm displacement.

Claims

1. A loudspeaker drive circuit, comprising;

an input to receive an audio signal;

a signal processor to generate a drive signal based on the input audio signal, to output the drive signal to a loudspeaker, the signal processor comprising;

a DC offset unit configured to generate a DC offset that shifts a peak positive diaphragm displacement and a peak negative diaphragm displacement to be symmetrical relative to no positive or negative diaphragm displacement;

an adder connected to add the DC offset from the DC offset unit to the received input audio signal and to output an added signal;

a gain element controlled to apply gain to the added signal such that the peak positive diaphragm displacement and the peak negative diaphragm displacement of the loudspeaker reach respective displacement limits of the loudspeaker.

2. The loudspeaker drive circuit of claim 1, wherein the signal processor is configured to incorporate the DC offset in the drive signal in each direction of excursion of a loudspeaker diaphragm.

3. The loudspeaker drive circuit of claim 2, wherein the signal processor is configured to determine a different amount of the DC offset to be incorporated to the drive signal in each direction asymmetrically.

4. The loudspeaker drive circuit of claim 1, wherein the signal processor is configured to incorporate a zero DC offset if the peak positive and peak negative displacement of the loudspeaker diaphragm will be below a predefined maximum value.

5. The loudspeaker drive circuit of claim 4, wherein the signal processor is configured to set a gain of the drive signal to a fixed value when the zero DC offset is incorporated in the drive signal.

13. The loudspeaker drive circuit of claim 1, wherein the positive and negative displacement limits are predefined displacement distances beyond which the loudspeaker can be immediately damaged or beyond which the expected life-time of the loudspeaker can be considerably reduced.

6. A loudspeaker driver for generating a drive signal for controlling a loudspeaker, the loudspeaker driver, when executed by a processor, performs an operation, the operation includes:

receiving an audio signal;

generating a drive signal based on the audio signal to drive the loudspeaker, wherein generating the drive signal comprises;

generating a DC offset that shifts a peak positive diaphragm displacement and a peak negative diaphragm displacement to be symmetrical relative to no positive or negative diaphragm displacement;

adding the DC offset from the DC offset unit to the received audio signal to generate an added signal; and

applying gain to the added signal such that the peak positive diaphragm displacement and the peak negative diaphragm displacement of the loudspeaker reach respective displacement limits of the loudspeaker.

7. The loudspeaker driver of claim 6, wherein the adding comprises adding the DC offset in each direction of excursion of the diaphragm of the loudspeaker.

8. The loudspeaker driver of claim 7, further including determining a different amount of the DC offset to be incorporated to the drive signal in each direction asymmetrically.

9. The loudspeaker driver of claim 8, including adding a zero DC offset when a displacement of the loudspeaker diaphragm will be below a predefined maximum value.

10. The loudspeaker driver of claim 9, including setting a gain of the drive signal to a fixed value when the zero DC offset is incorporated in the drive signal.

14. The loudspeaker driver of claim 6, wherein the positive and negative displacement limits are predefined displacement distances beyond which the loudspeaker can be immediately damaged or beyond which the expected life-time of the loudspeaker can be considerably reduced.

11. A method for operating a loudspeaker, the method comprising;

receiving an audio signal;

generating a drive signal based on the audio signal to drive a loudspeaker, wherein generating the drive signal comprises;

generating a DC offset that shifts a peak positive diaphragm displacement and a peak negative diaphragm displacement to be symmetrical relative to no positive or negative diaphragm displacement;

adding the DC offset from the DC offset unit to the received audio signal to generate an added signal; and

applying gain to the added signal such that the peak positive diaphragm displacement and the peak negative diaphragm displacement of the loudspeaker reach respective displacement limits of the loudspeaker.

12. The method of claim 11, wherein the positive and negative displacement limits are predefined displacement distances beyond which the loudspeaker can be immediately damaged or beyond which the expected life-time of the loudspeaker can be considerably reduced.