Patent US4649565A successfully refreshed from Google Patents.
US4649565A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electro-acoustic converter with compensated frequency response characteristic
Assignee: US Philips Corp
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Filing: 1984-11-05
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Granted: 1987-03-10
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Expires: 2004-11-05
Abstract
Abstract A device for converting an electric signal into an acoustic signal, which comprises an electro-acoustic transducer unit (2) having a quality factor (Q) less than unity. The device further comprises an amplifier circuit (3) for driving the transducer unit. The amplifier circuit has a frequency-dependent gain characteristic (6) which increases towards the lower frequencies, starting from f 2 , in a frequency range between a first and a second frequency (f 1 and f 2 ), f 1 being the resonant frequency of the transducer unit (2) and f 2 being greater than f 1 . The efficiency can be increased if amplifier the circuit includes a special amplifier such as a switched amplifier, for example, a class-D amplifier, or an amplifier with a power supply that provides a DC voltage that depends on the drive level of the amplifier.
Inventors
- 👤 Adrianus J. M. Kaizer
- 👤 Frederik L. J. Sangster
- 👤 Cornelis A. M. Wesche
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 14:15
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/02; H03F1/0205; H03F1/0211; H03F1/0216; H03F1/0233; H03F1/0244; H03F3/00; H03F3/20; H03F3/21; H03F3/217; H03F3/2171; H04; H04R; H04R3/00; H04R3/04
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
189 words
A device for converting an electric signal into an acoustic signal comprising, an input terminal for receiving an electric input signal, an electro-acoustic transducer unit, and an amplifier circuit for driving the electro-acoustic transducer unit, said amplifier circuit having an input coupled to the input terminal and an output coupled to the electro-acoustic transducer unit, the electro-acoustic transducer unit having a quality factor less than unity, the amplifier circuit having a frequency dependent gain factor with a frequency response characteristic which rolls off in a frequency range betwen a first frequency, which is substantially equal to the resonant frequency of the transducer unit, and a second frequency which lies above the first frequency, said roll-off being substantially the inverse of the shape of the frequency-response characteristic of the transducer unit in said frequency range, characterized in that the amplifier circuit exhibits, an electrical efficiency which is higher than that of a conventional class B amplifier having a fixed supply voltage in at least a sub-region lying in a region of low drive levels, wherein the sub-region lies at higher drive levels in the said region of low drive levels.
Claim 2
Independent Claim
189 words
A device for converting an electric signal into an acoustic signal comprising, an input terminal for receiving an electric input signal, an electro-acoustic transducer unit, and an amplifier circuit for driving the electro-acoustic transducer unit, said amplifier circuit having an input coupled to the input terminal and an output coupled to the electro-acoustic transducer unit, the electro-acoustic transducer unit having a quality factor less than unity, the amplifier circuit having a frequency dependent gain factor with a frequency response characteristic which rolls off in a frequency range betwen a first frequency, which is substantially equal to the resonant frequency of the transducer unit, and a second frequency which lies above the first frequency, said roll-off being substantially the inverse of the shape of the frequency-response characteristic of the transducer unit in said frequency range, characterized in that the amplifier circuit exhibits, an electrical efficiency which is higher than that of a conventional class B amplifier having a fixed supply voltage in at least a sub-region lying in a region of low drive levels, wherein the sub-region lies at higher drive levels in the said region of low drive levels.
Claim 3
Dependent Claim
21 words
A device as claimed in claim 1, wherein the quality factor of the electro-acoustic transducer unit is between 0.2 and 0.8.
Claim 4
Dependent Claim
37 words
A device as claimed in claim 1, wherein the electro-acoustic transducer unit comprises an electro-acoustic transducer accommodated in a bass-reflex cabinet, characterized in that the quality factor of the electro-acoustic transducer unit is between 0.1 and 0.6.
Claim 5
Dependent Claim
38 words
A device as claimed in claim 1 wherein the frequency-response characteristic of said amplifier circuit in a frequency range below said first frequency is at least substantially flat or rolls-off towards lower frequencies from approximately said first frequency.
Claim 6
Dependent Claim
15 words
A device as claimed in claim 1 wherein the amplifier circuit comprises a switched amplifier.
Claim 7
Dependent Claim
14 words
A device as claimed in claim 5 wherein the amplifier is a class-D amplifier.
Claim 8
Dependent Claim
27 words
A device as claimed in claim 1 wherein said amplifier circuit comprises an amplifier having a power-supply voltage that depends on the drive level of the amplifier.
Claim 9
Dependent Claim
27 words
A device as claimed in claim 1 wherein the amplifier circuit gain factor varies inversely with frequency in the frequency range between said first and second frequencies.
Claim 10
Dependent Claim
18 words
A device as claimed in claim 1 wherein the quality factor of the electro-acoustic transducer unit is 0.4.
Claim 11
Dependent Claim
29 words
A device as claimed in claim 1 wherein the amplifier circuit comprises a switched amplifier, and the quality factor of the electro-acoustic transducer unit is between 0.2 and 0.8.
Claim 12
Dependent Claim
136 words
An electro-acoustic converter system comprising: an input terminal for receiving an electric input signal, an electro-acoustic transducer unit, and an amplifier circuit for driving the electro-acoustic transducer unit, said amplifier circuit having an input coupled to the input terminal and an output coupled to the electro-acoustic transducer unit, the electro-acoustic transducer unit having a quality factor less than unity, the amplifier circuit having a frequency-dependent gain factor with a frequency-response characteristic which rolls-off in a frequency range between a first frequency, which is substantially equal to the resonant frequency of the transducer unit, and a second frequency which lies above the first frequency, wherein the roll-off is substantially the inverse of the shape of the frequency-response characteristic of the transducer unit in said frequency range, characterized in that the amplifier comprises a class D amplifier circuit.
Claim 13
Dependent Claim
136 words
An electro-acoustic converter system comprising: an input terminal for receiving an electric input signal, an electro-acoustic transducer unit, and an amplifier circuit for driving the electro-acoustic transducer unit, said amplifier circuit having an input coupled to the input terminal and an output coupled to the electro-acoustic transducer unit, the electro-acoustic transducer unit having a quality factor less than unity, the amplifier circuit having a frequency-dependent gain factor with a frequency-response characteristic which rolls-off in a frequency range between a first frequency, which is substantially equal to the resonant frequency of the transducer unit, and a second frequency which lies above the first frequency, wherein the roll-off is substantially the inverse of the shape of the frequency-response characteristic of the transducer unit in said frequency range, characterized in that the amplifier comprises a class D amplifier circuit.
Claim 14
Dependent Claim
125 words
An electro-acoustic converter system as claimed in claim 11 wherein said class D amplifier comprises: a differential amplifier having a first input coupled to said input terminal, a high-frequency ramp generator, a comparator having first and second inputs coupled to outputs of the differential amplifier and the ramp generator, respectively, said comparator having an output which supplies a pulse-width modulated binary-type signal, first and second field-effect transistors having a common output terminal coupled to the electro-acoustic transducer unit, means coupling control electrodes of said field-effect transistors to the output of the comparator so that said first and second field-effect transistors are alternately driven into conduction, and a negative feedback circuit coupling an output of the amplifier circuit to a second input of the differential amplifier.
Claim 15
Dependent Claim
82 words
An electro-acoustic converter system as claimed in claim 12 wherein said coupling means comprises, first and second networks connected between the output of the comparator and the control electrodes of the first and second field-effect transistors, respectively, each network comprising, in cascade, a delay circuit and a series-connected RC network coupled to a source of supply voltage via a zener diode, and wherein the common output terminal of the field-effect transistors is coupled to the electro-acoustic transducer unit via a low-pass filter.
Claim 16
Dependent Claim
27 words
An electro-acoustic converter system as claimed in claim 11 wherein said class D amplifier comprises a switched amplifier that is switched dependent on the amplifier drive level.
Claim 17
Dependent Claim
148 words
An electro-acoustic converter system comprising, an input terminal for receiving an electric input signal, an electro-acoustic transducer unit, and an amplifier circuit for driving the electro-acoustic transducer unit, said amplifier circuit having an input coupled to the input terminal and an output coupled to the electro-acoustic transducer unit, the electro-acoustic transducer unit having a quality factor less than unity, the amplifier circuit having a frequency-dependent gain factor with a frequency-response characteristic which exhibits a roll-off in a frequency range between a first frequency, which is substantially equal to the resonant frequency of the transducer unit, and a second frequency which lies above the first frequency, wherein the roll-off is substantially the inverse of the shape of the frequency-response characteristic of the transducer unit in said frequency range, and wherein said amplifier circuit comprises an amplifier having a power-supply voltage that depends on the drive level of the amplifier.
Claim 18
Dependent Claim
148 words
An electro-acoustic converter system comprising, an input terminal for receiving an electric input signal, an electro-acoustic transducer unit, and an amplifier circuit for driving the electro-acoustic transducer unit, said amplifier circuit having an input coupled to the input terminal and an output coupled to the electro-acoustic transducer unit, the electro-acoustic transducer unit having a quality factor less than unity, the amplifier circuit having a frequency-dependent gain factor with a frequency-response characteristic which exhibits a roll-off in a frequency range between a first frequency, which is substantially equal to the resonant frequency of the transducer unit, and a second frequency which lies above the first frequency, wherein the roll-off is substantially the inverse of the shape of the frequency-response characteristic of the transducer unit in said frequency range, and wherein said amplifier circuit comprises an amplifier having a power-supply voltage that depends on the drive level of the amplifier.
Claim 19
Dependent Claim
111 words
An electro-acoustic converter system as claimed in claim 15 wherein the amplifier comprises an operational amplifier having a first input coupled to said input terminal and an output coupled to said electro-acoustic transducer unit, said amplifier circuit further comprising, a DC voltage supply circuit responsive to an output signal at the output of said operational amplifier to supply DC operating voltages to said operational amplifier that change in accordance with the level of said operational amplifier output signal thereby to provide the amplifier with said frequency-dependent gain factor to produce said roll-off in the frequency-response characteristic that varies inversely with the frequency-response characteristic of the transducer unit in said frequency range.
Claim 20
Dependent Claim
75 words
An electro-acoustic converter system as claimed in claim 15 wherein said amplifier comprises an operational amplifier and the amplifier circuit comprises, in cascade, a filter circuit and said operational amplifier coupled between the input terminal and the electro-acoustic transducer unit, and a threshold device coupled to an output of the filter circuit for selectively controlling the DC power supply voltage to the operational amplifier as a function of an output signal of the filter circuit.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-03-09 | 1990-09-08 | 1991-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-03-09 | 1994-09-08 | 1995-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-03-09 | 1998-09-08 | 1999-03-10 | $7700.00 | Window Closed / Lapsed |