Audio transducer

• US 4,809,339 A
• Filed: 01/27/1987
• Issued: 02/28/1989
• Est. Priority Date: 09/12/1985
• Status: Expired due to Fees

• Current Assignee: Kelvin Shih, Peter A Hochstein
• Original Assignee: Kelvin Shih, Peter A Hochstein
• Inventors: Hochstein, Peter A., Shih, Kelvin
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US07/008,073
• Time in Patent Office: 763 Days
• Field of Search: 381/28, 381/77, 381/110
• US Class Current: 381/110
• CPC Class Codes: H03G 3/341 Muting when no signals or only weak signals are present H03G3/344, H03G3/345 take precedence

Abstract

A method and circuit for supplying power from a constantly available power source (20) to an audio power amplifier (14) for a speaker (12) utilizing input leads (16,18) having an audio signal. A pre-amplifier (24) is used for amplifying the audio signal having a difference in potential between the input leads (16,18). A switch (58) powers the audio power amplifier (14) and pre-amplifier (24) from the power source (20) in response to a control signal. The method and circuit is characterized by sensing (26) the existence of a diminished audio signal by determining a greater difference than the predetermined difference between the input leads (16,18) to produce the control signal which operates a relay driver transistor (62) which, in turn, operates a relay switch (66) to supply power to the pre-amplifier (24) and power amplifier (14).

Claims

1. A method of supplying power from a constantly available power source (20) to an audio power amplifier means (14) for an acoustic transducer (12) of the type utilizing first and second input leads (16, 18) having a difference in potential responsive to an audio signal, said method comprising the steps of;

detecting (24) a predetermined audio signal having a difference in potential between the input leads (16,

     18) to produce an amplified output response for driving the amplifier means (14), sensing the presence of an audio signal for selectively supplying power from the constantly available power source (20) to enable the detecting (24) and to supply power to the amplifier means (14), the sensing (26) of the audio signal being further defined as amplifying (28) the audio signal to produce an amplified audio signal and comparing the amplified audio signal to a minimum magnitude reference voltage to produce a control signal, integrating (60) the control signal and a second control signal in response to an audio signal on a second pair of input leads (16,

     18) to form a combined control signal and limiting the potential of the combined control signal to operate the supplying (58) of the power, and closing (58) a power circuit (64) in response to the combined control signal to power the audio power amplifier means (14) and to initiate the detecting (24).

2. A method as set forth in claim 1 further defined as filtering (30, 31) out direct current components of the audio signal to amplify (28) only the alternating current components to produce the control signal.

3. A method as set forth in claim 1 further defined as delaying (82) the opening of the power circuit to discontinue power from the power source (20) to the audio power amplifier means (14) and the pre-amplifying (24) for a period of time after said combined control signal is discontinued as a result of the absence of an audio signal.

4. A power circuit (22, 24) for selectively supplying power from a constantly available power source (20) to an audio amplifier means (14) for an audio transducer (12) of the type utilizing first and second input leads (16, 18) having a difference in potential responsive to an audio signal, said control circuit (22, 24) comprising;

pre-amplifier means (24) for detecting an audio signal on the input leads (16,

     18) to produce an audio amplified response to apply to the audio amplifier (14), sensing means (26) for selectively supplying power from the constantly available power source (20) to said pre-amplifier means (24) and to an amplifier means (28) for amplifying the audio signal on the input leads (16,

     18) to produce an amplified audio signal, and comparator means (42) for comparing said amplified audio signal with a minimum magnitude reference voltage to produce a control signal, integrator means (60) for combining said control signal with a second control signal responsive to a second pair of input leads (16,

     18) driving a second audio amplifier and transducer to form a combined control signal, limiting the potential of said combined control signal, and applying said combined control signal to a closing a power circuit (64) to supply power to said preamplifier means (24) and the amplifier means (14) in response to said combined control signal.

5. A circuit as set forth in claim 4 wherein said sensing means (26) further includes filtering means (30, 31) for filtering out direct current components of the audio signal to amplify only the alternating current components to produce said combined control signal.

6. A circuit as set forth in claim 4 including time-delay means (82) for delaying the opening of the power circuit (64) to discontinue power from the power source (20) to the audio power amplifier means (14) and said pre-amplifier means (24) for a period of time after said combined control signal is discontinued as a result of the absence of the audio signal.

7. A circuit as set forth in claim 4 wherein said differential amplifier means (28) comprises;

a differential amplifier (32), first resistor (34), second resistor (36), third resistor (40), and feedback resistor (38) for establishing a given closed loop gain by receiving the audio signal from the filter means (30,

     31) to produce said amplified audio signal related to the difference between the input leads (16,18).

8. A circuit as set forth in claim 4 wherein said comparator means (42) comprises;

a comparator operational amplifier (44), first resistor (46), second resistor (48), and third resistor (50) to act as a voltage divider so that said comparator (44) receives part of the potential of said amplified audio signal to produce said control signal.

9. A circuit as set forth in claim 8 wherein said comparator means (42) further includes an output diode (52) connected to said comparator operational amplifier (44), a first capacitor (54) for filtering out direct current components of said amplified audio signal from said differential amplifier (32), and a second capacitor (56) to filter out direct current components from a ground reference.

10. A circuit as set forth in claim 9 wherein said filter means (30, 31) comprises;

a first capacitor (30) and a second capacitor (31) receiving the audio signal from the input leads (16,18).

11. A circuit as set forth in claim 10 wherein said pre-amplifier means (24) comprises;

a differential amplifier (88), first resistor (90), second resistor (92), third resistor (96), fourth resistor (98), and feedback resistor (94) for closed loop gain by receiving part of the potential of the audio signal to produce said amplified output response.

12. A circuit as set forth in claim 11 wherein said switch means (58) comprises;

a transistor (62) configured as a relay driver, contacts (64), and said power circuit (64) comprising a relay (66) controlled by said transistor (62) for operating said contacts (64).

13. A circuit as set forth in claim 12 including a free-wheeling diode (68) in parallel with said relay (66) for protecting said transistor (62).

14. A circuit as set forth in claim 13 wherein said switch means (58) further includes a first diode (70) for protecting said power control circuit (22) against reverse power connections and negative transient power line rejection, a capacitor (74) and (75) as power supply filters, an inductor (76) for filtering the input power from the power source (20) to said circuit (22), and a resistor (78) and light-emitting diode (72) between said contacts (64) and ground reference for visually indicating that said contacts (64) are closed.

15. A circuit as set forth in claim 14 wherein said integrator means (60) comprises;

an input resistor (80) which receives said control signal from either channel or both for limiting the potential of said control signal from either channel to said transistor (62), a capacitor (81) interconnecting said differential amplifier (32) and the ground reference and said time-delay means (82) comprises;

a capacitor (84) and a resistor (86) for discharging said capacitor (84) in a given period of time.

16. An amplified audio speaker assembly (10) comprising;

a transducer means (12) for converting variations of electrical energy in an audio signal into corresponding variations of acoustic energy, audio power amplifier means (14) for supplying an audio signal to said transducer means (12), said assembly including input signal leads (16,

     18) for receiving an audio signal, said assembly including a power lead (20) for attachment to a source of constant power to supply power to said audio power amplifier means (14), and control circuit means (22,

     24) supported by said transducer means (12) including pre-amplifier means (24) for amplifying the audio signal, said control circuit (22,

     24) including sensing means (26) for selectively supplying power from the power lead (20) to said power amplifier means (14) and said pre-amplifier means (24), said sensing means (26) including differential amplifier means (28) for amplifying the audio signal to produce an amplified audio signal and comparator means (42) for comparing said amplified audio signal with a minimum magnitude to produce a control signal, integrator means (60) for combining said control signal with a second control signal responsive to a second pair of input leads (16,

     18) driving a second audio amplifier and transducer to produce a combined control signal, limiting the potential of said combined control signal, and applying said combined control signal to operate a switch means (58) for closing a power circuit (64) to supply power to said pre-amplifier means (24) and said amplifier means (14) in response to said combined control signal.

17. A circuit as set forth in claim 16 including filter means (30, 31) for filtering out direct current components of the audio signal to amplify only the alternating current components to produce said control signal.

18. A circuit as set forth in claim 16 including time-delay means (82) for delaying the opening of the power circuit (64) to discontinue power from the power source (20) to the audio power amplifier means (14) and pre-amplifier means (24) for a period of time after said combined control signal is discontinued as a result of the absence of an audio signal.

19. A power circuit (22, 24) for selectively supplying power from a constantly available power source (20) to an audio amplifier means (14) for an audio transducer of the type utilizing first and second input leads (16, 18) having a difference in potential responsive to an audio signal, said control circuit (22, 24) comprising;

means (24) for detecting an audio signal on the input leads (16,

     18), sensing means (26) for selectively supplying power from the constantly available power source (20) to the audio amplifier means (14), said sensing means (26) including differential amplifier means (28) for amplifying the audio signal on the input leads (16,

     18) to produce an amplified audio signal and comparator means (42) for comparing said amplified audio signal with a minimum magnitude reference voltage to produce a control signal, integrator means (60) for combining said control signal with a second signal responsive to a second pair of input leads (16,

     18) driving a second audio amplifier and transducer to produce a combined control signal, limiting the potential of said combined signal, and applying said combined control signal to operate a switch means (58) for closing a power circuit (62) to supply power to the audio amplifier means (14) in response to said control signal.

20. A circuit as set forth in claim 19 wherein said sensing means (26) further includes filtering means (30,31) for filtering out direct current components of the audio signal to amplify only the alternating current components to produce said combined control signal.

21. A circuit as set forth in claim 19 including time-delay means (82) for delaying the opening of the power circuit (64) to discontinue power from the power source (20) to the audio power amplifier means (14) for a period of time after said combined control signal is discontinued as a result of the absence of the audio signal.

22. A power circuit (22, 24) for selectively supplying power from a constantly available power source (20) to an audio amplifier means (14) for an audio transducer (12) of the type utilizing first and second input leads (16, 18) having a difference in potential responsive to an audio signal, said control circuit (22, 24) comprising;

means (24) connecting the input leads (16,

     18) to the audio amplifier means (14) for transmission of the audio signal thereto, sensing means (26) for selectively supplying power from the constantly available power source (20) to the audio amplifier means (14), said sensing means (26) including differential amplifier means (28) for amplifying the audio signal on the input leads (16,

     18) to produce an amplified audio signal and comparator means (42) for comparing said amplified audio signal with a minimum magnitude reference voltage to produce a control signal, integrator means (60) for combining said control signal with a second signal responsive to a second pair of input leads (16,

     18) driving a second audio amplifier and transducer to produce a combined control signal, and applying said combined control signal to operate a switch means (38) for closing a power circuit (64) to supply power to the amplifier means (14) in response to said combined control signal.

23. A circuit as set forth in claim 22 wherein said sensing means (26) further includes filtering means (30, 31) for filtering out direct current components of the audio signal to amplify only alternating current components to produce said control signal.

24. A circuit as set forth in claim 22 including time-delay means (82) for delaying the opening of the power circuit (64) to discontinue power from the power source (20) to the audio power amplifier means (14) for a period of time after said combined control signal is discontinued as a result of the absence of the audio signal.

25. A method of supplying power from a constantly available power source (20) to an audio amplifier means (14) for an acoustic transducer (12) of the type utilizing first and second input leads (16, 18) having a difference in potential responsive to an audio signal, said method comprising the steps of;

connecting the input leads (16,

     18) to the audio amplifier means (14) for transmission of the audio signal thereto, sensing the presence of an audio signal for selectively supply power to the amplifier means (14), the sensing (26) of the audio signal being further defined as amplifying (28) the audio signal to produce an amplified audio signal and comparing the amplified audio signal to a minimum magnitude reference voltage to produce a control signal, integrating (60) the control signal and a second control signal in response to an audio signal on a second pair input leads (16,

     18) to form a combined control signal, and applying the combined control signal to close a power circuit (64) to power the audio power amplifier means (14).

26. A method as set forth in claim 25 further defined as the connecting including differentially detecting an audio signal on the input leads (16,18) to send to the audio amplifier means.

27. A method as set forth in claim 25 further defined as filtering (30,31) out direct current components of the audio signal to amplify only the alternating current components to produce the combined control signal.

28. A method as set forth in claim 25 further defined as delaying (82) the opening of the power circuit (64) to discontinue power from the power source (20) to the audio amplifier means (14) for a period of time after the combined control signal is discontinued as a result of the absence of the audio signal.

29. A power circuit (22, 24) for selectively supplying power from a constantly available power source (20) to an audio amplifier means (14) for an audio transducer (12) of the type utilizing first and second input leads (16, 18) haing a difference in potential responsive to an audio signal, comprising;

means (24) connecting the input leads (16,

     18) to the audio amplifier means (14) for transmission of the audio signal thereto, sensing means (26) for selectively supplying power from the constantly available power source (20) to the audio amplifier means (14), said sensing means (26) including differential amplifier means (28) for amplifying the audio signal on the input leads (16,

     18) to produce an amplified audio signal and comparator means (42) for comparing said amplified audio signal with a minimum magnitude reference voltage to produce a control signal, said comparator means (42) comprising a comparator operational amplifier (44) having an inverting and noninverting input, first resistor (46) connected to said inverting input and second resistor (48) connected between said inverting and noninverting input and third resistor (50) connected to said noninverting input to act as a voltage divider so that said comparator operational amplifier (44) receives part of the potential of said amplified audio signal to produce said control signal, and switch means (58) for closing a power circuit (64) to supply power to the amplifier means (14) in response to said control signal.

30. A power circuit (22, 24) for selectively supplying power from a constantly available power source (20) to an audio amplifier means (14) for an audio transducer (12) of the type utilizing first and second input leads (16, 18) having a difference in potential responsive to an audio signal, comprising;

means (24) connecting the input leads (16,

     18) to the audio amplifier means (14) for transmission of the audio signal thereto, sensing means (26) for selectively supplying power from the constantly available power source (20) to the audio amplifier means (14), said sensing means (26) including differential amplifier means (28) for amplifying the audio signal on the input leads (16,

     18) to produce an amplified audio signal and comparator means (42) for comparing said amplified audio signal with a minimum magnitude reference voltage to produce a control signal, filter means (54) for receiving said amplified audio signal and filtering out direct current components for said comparator means (42), and switch means (58) for closing a power circuit (64) to supply power to the amplifier means (14) in response to said control signal.