Transducer with Integrated Sensor

• US 20120177215A1
• Filed: 08/19/2011
• Published: 07/12/2012
• Est. Priority Date: 01/06/2011
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Wendell, John H., Bose, Amar G.
• Granted Patent: US 9,049,523 B2
• Time in Patent Office: Days
• US Class Current: 381/74
• CPC Class Codes: G01D 5/2417 by varying separation
• CPC Class Codes: H04R 29/003 of the moving-coil type
• CPC Class Codes: H04R 3/002 Damping circuit arrangements for transducers, e.g. motional feedback circuits

Abstract

An electroacoustic transducer for converting electrical input signals into acoustic output signals includes a diaphragm adapted to move relative to a housing in response to the electrical input signals to produce the acoustic output signals, a displacement sensor, a bias voltage source, and an amplifier. The displacement sensor includes a first electrode adhered to the diaphragm and a second electrode on a first surface of the housing located proximate to the first electrode. A capacitance between the first electrode and the second electrode varies with a displacement of the diaphragm relative to the housing. The bias voltage source is coupled to at least one of the first electrode or the second electrode and provides a fixed charge to the electrode to which it is attached. The amplifier amplifies a change in voltage between the first and second electrodes to produce an output voltage between first and second signal outputs.

Claims

1. An electroacoustic transducer for converting electrical input signals into acoustic output signals, the electroacoustic transducer comprising:

a housing;

a diaphragm located proximate to the housing, adapted to move relative to the housing in response to the electrical input signals to produce the acoustic output signals;

a displacement sensor comprising;

a first electrode adhered to the diaphragm, and

a second electrode on a first surface of the housing located proximate to the first electrode,

wherein a capacitance between the first electrode and the second electrode varies with a displacement of the diaphragm relative to the housing;

a bias voltage source coupled to at least one of the first electrode or the second electrode and providing a fixed charge to the electrode to which it is attached; and

an amplifier amplifying a change in voltage between the first and second electrodes to produce an output voltage between first and second signal outputs.

2. The electroacoustic transducer of claim 1 wherein the second electrode is located proximate to a first region of the first electrode;

the displacement sensor further comprising a third electrode on the first surface of the housing located proximate to a second region of the first electrode;

wherein the first capacitance between the first electrode and the second electrode and a second capacitance between the first electrode and the third electrode each vary similarly with a displacement of the diaphragm relative to the housing;

the bias voltage source is coupled to the second electrode and the third electrode; and

the amplifier amplifies a change in total voltage between the second and third electrodes to produce the output voltage.

3. The electroacoustic transducer of claim 2 wherein the change in distance between a first surface of the housing and the diaphragm resulting from movement of the diaphragm is substantially uniform over the area of the second and third electrodes.

4. The electroacoustic transducer of claim 2 wherein the amplifier comprises a transistor having its gate coupled to the second electrode and its source and drain coupled to the first and second signal outputs.

5. The electroacoustic transducer of claim 4 wherein the bias voltage source comprises an external power source having a first terminal coupled to the drain of the transistor and a second terminal coupled to the third electrode, the bias voltage being applied to the second electrode via gate leakage of the transistor.

6. The electroacoustic transducer of claim 2 wherein:

the transducer comprises a compression-type electroacoustic transducer;

the housing comprises a phase plug; and

the second electrode and third electrode comprise metal on a surface of the phase plug.

7. The electroacoustic transducer of claim 6 wherein:

the phase plug comprises a plurality of distinct parts; and

the second and third electrode comprise layers of metal conforming to non-conducting portions of a surface of one of the plurality of parts of the phase plug.

8. The electroacoustic transducer of claim 6 wherein:

the phase plug comprises a plurality of distinct solid metal parts; and

the second and third electrode comprise portions of one of the plurality of solid metal parts of the phase plug.

9. The electroacoustic transducer of claim 2 wherein the first surface of the housing is a surface of a block of conductive material, and the second and third electrodes comprise portions of the block that are electrically insulated from each other.

10. The electroacoustic transducer of claim 2 wherein the first surface of the housing is a surface of a block of non-conductive material, and the second and third electrodes comprise layers of metal adhered to the block of non-conductive material.

11. The electroacoustic transducer of claim 2 wherein the first surface of the housing is a surface of a printed circuit board, and the second and third electrodes comprise metal areas on the printed circuit board.

12. The electroacoustic transducer of claim 1 wherein the first electrode is located proximate to a first region of the second electrode;

the displacement sensor further comprising a third electrode adhered to the diaphragm and located proximate to a second region of the second electrode;

wherein the first capacitance between the first electrode and the second electrode and a second capacitance between the third electrode and the second electrode each vary similarly with a displacement of the diaphragm relative to the housing;

the bias voltage source is coupled to the first electrode and the third electrode; and

the amplifier amplifies a change in total voltage between the first and third electrodes to produce the output voltage.

13. The electroacoustic transducer of claim 12 wherein:

the first and third electrode each comprise a layer of metal adhered to a top surface of the diaphragm facing away from the first surface of the housing;

the diaphragm is attached to the housing by a ring surrounding a periphery of the diaphragm; and

electrical connections to the first and third electrodes are made via the ring.

14. The electroacoustic transducer of claim 12 wherein:

the first and third electrode each comprise a layer of metal adhered to a bottom surface of the diaphragm facing towards the first surface of the housing; and

electrical connections to the first and third electrodes are made via the housing where the housing contacts an outer periphery of the diaphragm.

15. The electroacoustic transducer of claim 12 wherein:

the first and third electrode each comprise a layer of metal adhered to a bottom surface of the diaphragm facing towards the first surface of the housing;

the transducer further comprises a voice coil mechanically coupled to the diaphragm; and

electrical connections to the first and third electrodes are made where the voice coil is coupled to the diaphragm.

16. The electroacoustic transducer of claim 1 wherein the amplifier comprises a transistor having its gate coupled to the first electrode and its source and drain coupled to the first and second signal outputs.

17. The electroacoustic transducer of claim 16 wherein the bias voltage source comprises an external power source having a first terminal coupled to the drain of the transistor and a second terminal coupled to the second electrode, the bias voltage being applied to the first electrode via gate leakage of the transistor.

18. The electroacoustic transducer of claim 1 wherein the housing comprises a basket.

19. The electroacoustic transducer of claim 1 wherein the housing comprises a pole piece.

20. The electroacoustic transducer of claim 1 wherein the first electrode comprises a conductive coating on a non-conductive substrate.

21. The electroacoustic transducer of claim 1 wherein the bias voltage source comprises a permanently charged material within the at least one of the electrodes.

22. The electroacoustic transducer of claim 1 wherein the diaphragm is metal and comprises the first electrode.

23. An electroacoustic transducer for converting electrical input signals into acoustic output signals comprising:

a housing;

a moving portion located proximate to the housing, adapted to move relative to the housing in response to the electrical input signals;

a displacement sensor comprising;

a first electrode adhered to the moving portion,

a second electrode on a first surface of the housing located proximate to a first region of the first electrode, and

a third electrode on the first surface of the housing located proximate to a second region of the first electrode,

wherein a first capacitance between the first electrode and the second electrode and a second capacitance between the first electrode and the third electrode each vary similarly with a displacement of the moving portion relative to the housing;

a bias voltage source coupled to the second electrode and the third electrode and providing a fixed charge to the second and third electrodes; and

an amplifier amplifying a change in voltage between the second and third electrodes to produce an output voltage between first and second signal outputs.

24. The electroacoustic transducer of claim 23 wherein the moving portion comprises a diaphragm for producing the acoustic output signals.

25. The electroacoustic transducer of claim 23 wherein the moving portion comprises a voice coil mechanically coupled to a diaphragm for producing the acoustic output signals.

26. The electroacoustic transducer of claim 23 wherein the moving portion comprises a magnet mechanically coupled to a diaphragm for producing the acoustic output signals.

27. An acoustic noise reducing headphone system comprising:

a feedback active noise reduction circuit;

an electroacoustic output transducer coupled to the feedback active noise reduction circuit, the electroacoustic output transducer comprising;

a housing;

a diaphragm located proximate to the housing, adapted to move relative to the housing in response to the electrical input signals to produce the acoustic output signals; and

a displacement sensor comprising;

a first electrode adhered to the diaphragm, and

a second electrode on a first surface of the housing located proximate to the first electrode,

wherein a capacitance between the first electrode and the second electrode varies with a displacement of the diaphragm relative to the housing;

a bias voltage source coupled to at least one of the first electrode or the second electrode of the displacement sensor and providing a fixed charge to the electrode to which it is attached; and

an amplifier amplifying a change in voltage between the first and second electrodes to produce an output voltage between first and second signal outputs.

28. The electroacoustic transducer of claim 27 wherein the second electrode is located proximate to a first region of the first electrode;

the displacement sensor further comprising a third electrode on the first surface of the housing located proximate to a second region of the first electrode;

wherein the first capacitance between the first electrode and the second electrode and a second capacitance between the first electrode and the third electrode each vary similarly with a displacement of the diaphragm relative to the housing;

the bias voltage source is coupled to the second electrode and the third electrode; and

the amplifier amplifies a change in total voltage between the second and third electrodes to produce the output voltage.

29. The electroacoustic transducer of claim 28 wherein the amplifier comprises a transistor having its gate coupled to the second electrode and its source and drain coupled to the first and second signal outputs.

30. The electroacoustic transducer of claim 29 wherein the bias voltage source comprises an external power source having a first terminal coupled to the drain of the transistor and a second terminal coupled to the third electrode, the bias voltage being applied to the second electrode via gate leakage of the transistor.

31. The electroacoustic transducer of claim 27 wherein the bias voltage source comprises a permanently charged material within the at least one of the electrodes.

32. An audio loudspeaker system comprising:

an input for receiving audio signals for reproduction;

an electroacoustic output transducer operably coupled to the input, the electroacoustic output transducer comprising;

a housing;

a diaphragm located proximate to the housing, adapted to move relative to the housing in response to the electrical input signals to produce the acoustic output signals; and

a displacement sensor comprising;

a first electrode adhered to the diaphragm, and

a second electrode on a first surface of the housing located proximate to the first electrode,

wherein a capacitance between the first electrode and the second electrode varies with a displacement of the diaphragm relative to the housing;

a bias voltage source coupled to at least one of the first electrode or the second electrode of the displacement sensor and providing a fixed charge to the electrode to which it is attached; and

an amplifier amplifying a change in voltage between the first and second electrodes to produce an output voltage between first and second signal outputs.

33. The electroacoustic transducer of claim 32 wherein the second electrode is located proximate to a first region of the first electrode;

the displacement sensor further comprising a third electrode on the first surface of the housing located proximate to a second region of the first electrode;

wherein the first capacitance between the first electrode and the second electrode and a second capacitance between the first electrode and the third electrode each vary similarly with a displacement of the diaphragm relative to the housing;

the bias voltage source is coupled to the second electrode and the third electrode; and

the amplifier amplifies a change in total voltage between the second and third electrodes to produce the output voltage.

34. The electroacoustic transducer of claim 33 wherein the amplifier comprises a transistor having its gate coupled to the second electrode and its source and drain coupled to the first and second signal outputs.

35. The electroacoustic transducer of claim 34 wherein the bias voltage source comprises an external power source having a first terminal coupled to the drain of the transistor and a second terminal coupled to the third electrode, the bias voltage being applied to the second electrode via gate leakage of the transistor.

36. The electroacoustic transducer of claim 32 wherein the bias voltage source comprises a permanently charged material within the at least one of the electrodes.