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JP2009284072

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DESCRIPTION JP2009284072
An object of the present invention is to suppress the amount of current consumption while
suppressing the mounting area of a noise cancellation circuit. A noise cancellation circuit 50
converts an analog signal n1 output from a speaker 70 into a digital noise signal dn, an A / D
conversion circuit 56, and a first digital audio signal dL and a second digital audio signal dR. A
multiplexed digital audio signal dX is supplied from the outside, and a digital signal receiver 51
that separates and outputs one digital audio signal d, and an operation is performed so as to
cancel external noise, and a driving digital signal dT And a class D amplifier circuit 55 for driving
the speaker 70 based on the control signal P having a pulse width corresponding to the driving
digital signal dT. [Selected figure] Figure 2
Noise cancellation circuit and headphones
[0001]
The present invention relates to a noise cancellation circuit and headphones.
[0002]
2. Description of the Related Art A noise cancel circuit is known that drives external noise based
on a signal obtained by subtracting external noise collected by a microphone from an audio
signal, thereby canceling external noise.
For example, in Patent Document 1, external noise collected by a noise pickup microphone is A /
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1
D converted and added to a DSP (Digital Signal Processor), and the DSP D / A converts a signal
obtained by subtracting an external noise signal from a digital audio signal. Output to converter
circuit. Then, a signal (digital value) obtained by subtracting the external noise signal from the
digital audio signal is converted into an analog signal by the D / A conversion circuit and output
to the speaker. Japanese Patent Application Laid-Open No. 10-11901
[0003]
In Patent Document 1, there is a problem that the circuit scale is large and the amount of current
consumption is large because a D / A conversion circuit is required to convert a digital signal
calculated by the DSP into an analog signal so as to cancel external noise. there were. In view of
the above circumstances, the present invention aims to solve the problem of suppressing the
amount of current consumption while suppressing the circuit size of the noise cancellation
circuit.
[0004]
In order to solve the above problems, the noise cancellation circuit according to the present
invention is an analog signal (for example, a diagram shown in FIG. 1) output from a sound
collecting device (eg, a noise pickup microphone 60 shown in FIG. A conversion circuit (for
example, an A / D conversion circuit 56 shown in FIG. 2) for converting the analog signal n1
shown in FIG. 2 into first digital data (for example, digital noise signal dn shown in FIG. 2) A
separate digital audio signal in which the second digital audio signal is multiplexed is supplied
from the outside, and is separated and outputs one designated digital audio signal of the first
digital audio signal and the second digital audio signal. A circuit (for example, the digital signal
receiver 51 shown in FIG. 2), first digital data output from the conversion circuit, and output
from the separation circuit Arithmetic circuit (for example, DSP 53 shown in FIG. 2) that
performs an operation to cancel external noise based on the digital audio signal to generate the
second digital data (for example, driving digital signal dT shown in FIG. 2) And a class D amplifier
circuit for driving a sound emitting device (for example, the speaker 70 shown in FIGS. 1 and 2)
based on a control signal of a pulse width corresponding to the second digital data. According to
this aspect, the D / A converter circuit is a class D amplifier circuit that drives the sound emission
device based on the control signal of the pulse width corresponding to the second digital data
calculated by the arithmetic circuit so as to cancel external noise. Therefore, the amount of
current consumption can be suppressed while suppressing the circuit scale.
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[0005]
As a preferable aspect of the noise cancellation circuit according to the present invention, the
conversion circuit, the separation circuit, the arithmetic circuit, and the class D amplifier circuit
are mounted on a single integrated circuit. According to this aspect, since the noise cancellation
circuit is formed by one IC chip, there is an advantage that the circuit scale can be reduced.
[0006]
A headphone according to the present invention includes a sound collecting device, a sound
emitting device, the above-described noise cancellation circuit, a data transmission line to which
multiple digital audio signals are serially supplied, and a reference potential line to which a
reference potential is supplied. , And a wiring group connected to the noise cancellation circuit
(for example, the wiring group 40 shown in FIG. 1 or FIG. 8, the first wiring group 42a or the
second wiring group 42b shown in FIG. 3, the second wiring shown in FIG. Characterized in that
the group 44b or the third wiring group 44c, the second wiring group 410b or the third wiring
group 410c shown in FIG. 10, the second wiring group 420b or the third wiring group 420c
shown in FIG. Do. According to this aspect, only one wire is required to transmit the first digital
audio signal and the second digital audio signal. Therefore, there is an advantage that the
number of wires forming the wire group can be reduced.
[0007]
A headphone according to the present invention comprises a first unit (for example, a headphone
unit 20L for the left shown in FIG. 1) including a sound collecting device and a sound emitting
device and the above-described noise canceling circuit, a sound collecting device and a sound
emitting device A second unit (for example, the headphone unit 20R for the right illustrated in
FIG. 1) including the above-described noise cancellation circuit, and a jack (for example, the jack
30 illustrated in FIG. 1) capable of independently connecting three wires; And a wiring group (for
example, a wiring group 40 shown in FIG. 1) connected to the jack and commonly connected to
the first unit and the second unit, wherein the wiring group is formed by serial multiplex digital
audio signals. It is characterized by comprising a data transmission line to be supplied, a
reference potential line to which a reference potential is supplied, and a power supply line to
which a power supply potential based on the reference potential is supplied. To. According to this
aspect, the first unit is formed by connecting the wiring group including the data transmission
line, the reference potential line, and the power supply line to the jack capable of independently
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connecting the three lines. Because they are commonly connected to the second unit and the
second unit, there is an advantage that the conventional three-wire jack can be diverted. More
specifically, the wiring group according to the above aspect is branched from the first wiring
group (for example, the first wiring group 40a shown in FIG. 1) connecting the jack and the first
unit, and the first wiring group. It is comprised from the 2nd wiring group (for example, 2nd
wiring group 40b shown in FIG. 1) which leads to a 2nd unit.
[0008]
A headphone according to the present invention comprises a first unit (for example, a headphone
unit 20L for the left shown in FIG. 3) including a sound collecting device and a sound emitting
device and the above-mentioned noise canceling circuit, a sound collecting device and a sound
emitting device A second unit (for example, the headphone unit 20R for the right illustrated in
FIG. 3) including the above-described noise cancellation circuit, and a jack (for example, the jack
31 illustrated in FIG. 3) capable of independently connecting two lines; A first wiring group
connecting the jack and the first unit (for example, the first wiring group 42a shown in FIG. 3),
and a second wiring group connecting the first unit and the second unit (for example, the first
wiring group shown in FIG. And the first wiring group includes the first data transmission line to
which the multiplexed digital audio signal is supplied in serial form and the first reference
potential line to which the reference potential is supplied. The first unit includes a battery for
outputting a power supply potential based on a reference potential, and the second wiring group
includes a second data transmission line branched from a first data transmission line, and a first
data transmission line It is characterized by comprising a second reference potential line
branched from the reference potential line and a power supply line to which a power supply
potential is supplied. According to this aspect, the first wiring group connecting the jack and the
first unit includes two of the first data transmission line to which the multiplexed digital audio
signal is serially supplied and the first reference potential line. Since it is composed of wires,
there is an advantage that the conventional two-wire jack can be diverted.
[0009]
A headphone according to the present invention includes a first unit (for example, a headphone
unit 20L for the left shown in FIG. 4) including a sound collecting device and a sound emitting
device and the above-described noise canceling circuit, a sound collecting device and a sound
emitting device A second unit (for example, the headphone unit 20R for the right illustrated in
FIG. 4) including the above-described noise cancellation circuit, and a third unit (for example, the
third unit 21 illustrated in FIG. 4) including the battery; A jack capable of independently
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connecting two wires, a first wiring group (for example, a first wiring group 44a shown in FIG. 4)
connecting the jack and the third unit, a third unit and a first unit And a third wiring group (for
example, a third wiring group 44c shown in FIG. 4) for connecting the third unit and the second
unit (for example, a second wiring group 44b shown in FIG. 4). )When, The first wiring group
includes a first data transmission line to which multiple digital audio signals are serially supplied,
and a first reference potential line to which a reference potential is supplied, and is provided in a
third unit. The output battery outputs the power supply potential based on the reference
potential to the first power supply line (for example, the first power supply line 45a shown in
FIG. 4), and the second wiring group branches from the first data transmission line Second data
transmission line, a second reference potential line branched from the first reference potential
line, and a second power supply line branched from the first power supply line (for example, the
second power supply line shown in FIG. 4) 45b), and the third wiring group includes a third data
transmission line branched from the first data transmission line, a third reference potential line
branched from the first reference potential line, and a first And a third power supply line (for
example, a third power supply line 45c shown in FIG. 4) branched from the power supply line. It
is. According to this aspect, the first wiring group connecting the jack and the third unit includes
two of the first data transmission line to which the multiplexed digital audio signal is serially
supplied and the first reference potential line. Since it is composed of wires, there is an advantage
that the conventional two-wire jack can be diverted.
[0010]
As a preferred aspect of the headphone according to the present invention, the noise cancellation
circuit in each unit separates and takes in the digital audio signal to be supplied to the unit
among the multiplex digital audio signals in serial format supplied to the data transmission line. .
[0011]
As a preferable aspect of the headphone according to the present invention, each noise
cancellation circuit includes a non-volatile memory circuit storing at least a sound collecting
device and a parameter according to an acoustic characteristic of the sound emitting device, and
the arithmetic circuit is the memory circuit An operation is performed so as to cancel the noise
using the parameters read out from to generate the second digital data.
[0012]
A: First Embodiment FIG. 1 is a block diagram showing a schematic configuration of a headphone
10 according to a first embodiment of the present invention.
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The headphone 10 has a headphone unit 20L for the left, a headphone unit 20R for the right, a
jack 30 to which three wires can be independently connected, and a wiring group 40 commonly
connected to the headphone units 20L and 20R. .
As shown in FIG. 1, each of the headphone units 20L and 20R includes a noise canceling circuit
50, a noise pickup microphone 60 (sound collecting device) for collecting noise from the outside,
and a speaker (sound emitting device) And 70. As shown in FIG. 1, the wiring group 40 includes a
first wiring group 40a for connecting the jack 30 and the left headphone unit 20L, and a second
wiring branch from the first wiring group 40a to the right headphone unit 20R. It comprises the
wiring group 40b. Each of the first wiring group 40a and the second wiring group 40b includes a
first digital audio signal dL to be supplied to the headphone unit 20L for the left and a second
digital audio signal dR to be supplied to the headphone unit 20R for the right. , A reference
potential line 43 to which a reference potential GND is supplied, and a power supply line to
which a power supply potential VDD based on the reference potential GND is supplied. And 45.
[0013]
FIG. 2 is a block diagram showing the detailed configuration of the noise cancellation circuit 50.
As shown in FIG. As shown in FIG. 2, the noise cancellation circuit 50 includes a digital signal
receiver 51, an analog signal receiver 52, a DSP (Digital Signal Processor) 53 which is an
arithmetic circuit that performs digital signal arithmetic, and a switch SW1. A class D amplifier
circuit 55, an A / D conversion circuit 56 for converting an analog signal output from the noise
pickup microphone 60 into a digital signal, and a non-volatile memory 57 are provided. In the
present embodiment, the A / D conversion circuit 56, the digital signal receiver 51, the analog
signal receiver 52, the DSP 53, the class D amplifier circuit 55, and the non-volatile memory 57
are mounted on a single integrated circuit. Of course, some of these components may be external
circuits. As shown in FIG. 2, the noise cancel circuit 50 is connected to the transmission line 41
and to the reference potential line 43 and the power supply line 45.
[0014]
The switch SW1 shown in FIG. 2 is any one of the output signal of the digital signal receiver 51
and the output signal of the analog signal receiver 52 according to the level of the control signal
S output from the control circuit (not shown). To be supplied to the DSP 53. In the present
embodiment, only the multiplexed digital audio signal dX is assumed as the input signal, so the
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analog signal receiver 52 is not operated. Therefore, as the control signal S, a fixed level for
selecting an output signal of the digital signal receiver 51 is supplied to the noise cancel circuit
50.
[0015]
The digital signal receiver 51 in each headphone unit 20 separates and takes in the digital audio
signal d to be supplied to the headphone unit 20 among multiple digital audio signals dX in serial
format supplied to the transmission line 41. The digital signal receiver 51 in the left headphone
unit 20L separates and takes in the first digital audio signal dL, while the digital signal receiver
51 in the right headphone unit 20R separates the second digital audio signal dR. It is condition of
taking in. The digital audio signal d separated by the digital signal receiver 51 is output to the
DSP 53.
[0016]
The analog signal n1 output from the noise pickup microphone 60 is converted into a digital
noise signal dn by the A / D conversion circuit 56 and output to the DSP 53. The non-volatile
memory 57 stores at least a parameter X according to the acoustic characteristics of the noise
pickup microphone 60 and the speaker 70. The DSP 53 uses the parameter X read from the nonvolatile memory 57 to execute an operation so as to cancel noise from the outside, and generates
a driving digital signal dT. Further details are as follows. The DSP 53 corrects the digital noise
signal dn output from the A / D conversion circuit 56 based on the parameter X read from the
non-volatile memory 57. The corrected digital noise signal dn is a digital signal whose amplitude
is a value obtained by subtracting the amplitude that attenuates while the noise is transmitted in
the headphone 10 from the amplitude of the digital noise signal dn. The DSP 53 subtracts the
corrected digital signal dn from the digital audio signal d output from the digital signal receiver
51 to generate a driving digital signal dT, and outputs the driving digital signal dT to the class D
amplifier circuit 55. Do.
[0017]
The class D amplifier circuit 55 shown in FIG. 2 is a means for driving the speaker 70 based on
the control signal P having a pulse width corresponding to the driving digital signal dT. Further
details are as follows. The class D amplifier circuit 55 includes a signal generation circuit 54a
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and a drive circuit 54b. The signal generation circuit 54 a generates two control signals P 1 and
P 2 by pulse width modulating the drive digital signal dT output from the DSP 53. The drive
circuit 54b drives the speaker 70 in a Bridge Tied Load (BTL) system based on the control signals
P1 and P2. The noise cancellation circuit 50 according to the present embodiment operates so as
to cancel the influence of noise from the outside (feed-forward control operation) before the
influence appears.
[0018]
In the present embodiment, since the D-class amplification circuit 55 for driving the speaker 70
is provided based on the control signal P having a pulse width corresponding to the driving
digital signal dT output from the DSP 53, the driving digital signal dT As compared with the
aspect in which the speaker 70 is driven by converting it into an analog signal by the / A
conversion circuit, there is an advantage that the amount of current consumption can be
suppressed while suppressing the circuit scale.
[0019]
Further, in the present embodiment, since the noise cancel circuit 50 is formed by one IC chip,
there is an advantage that the circuit scale can be reduced.
[0020]
By the way, in an aspect in which each of the first digital audio signal dL and the second digital
audio signal dR is transmitted by separate wires, a transmission line for transmitting the first
digital audio signal dL and the second digital audio signal dR are transmitted. Since it is
necessary to form the wiring group 40 by four lines of the transmission line, the reference
potential line 43 and the power supply line 45, there is a problem that the conventional threewire jack can not be diverted.
On the other hand, in the present embodiment, since the serial digital multiplexed digital signal
dX in which the first digital audio signal dL and the second digital audio signal dR are
multiplexed is transmitted to the transmission line 41, the first digital Only one wire is required
to transmit the audio signal dL and the second digital audio signal dR.
That is, according to the present embodiment, since the wiring group 40 is formed by the three
lines of the transmission line 41, the reference potential line 43, and the power supply line 45,
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the conventional three-wire jack can be diverted. is there. Note that the system for transmitting
the serial digital digital audio signal dX by one transmission line 41 is optional. As a method of
transmitting serial digital data by one wire, there are SPDIF, RS232C, etc., for example.
[0021]
Second Embodiment FIG. 3 is a block diagram showing a schematic configuration of a headphone
10 according to a second embodiment of the present invention. As shown in FIG. 3, the
headphone 10 includes a headphone unit 20L for the left, a headphone unit 20R for the right, a
jack 31 to which two lines can be independently connected, a jack 31 and a headphone unit 20L
for the left. A first wiring group 42a to be connected and a second wiring group 42b to connect
the headphone unit 20L for the left and the headphone unit 20R for the right are provided. Each
of the headphone units 20L and 20R has a noise cancellation circuit 50, a microphone 61 that
converts the sound output from the speaker 70 into an analog electric signal and outputs the
signal to the noise cancellation circuit 50, and the speaker 70. The noise cancellation circuit 50
according to the present embodiment is the same as the configuration shown in FIG. 2, but in the
present embodiment, feedback control is performed to return the sound output from the speaker
70 to the input side of the noise cancellation circuit 50. It differs from the first embodiment.
[0022]
The first wiring group 42a is constituted by two lines of a first transmission line 41a through
which the multiplexed digital audio signal dX is transmitted in serial form and a first reference
potential line 43a to which the reference potential GND is supplied. As shown in FIG. 3, the
headphone unit 20L for the left includes a battery 80 that outputs a power supply potential VDD
based on the reference potential GND. The power supply potential VDD output from the battery
80 is supplied to each noise cancel circuit 50 via the power supply line 45. The second wiring
group 42b is a three-wire system including a second transmission line 41b branched from the
first transmission line 41a, a second reference potential line 43b branched from the first
reference potential line 43a, and a power supply line 45. It consists of
[0023]
Also in this embodiment, the multiplexed digital audio signal dX in serial format in which the first
digital audio signal dL and the second digital audio signal dR are multiplexed is transmitted to
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the transmission line 41, so the first digital audio signal dL and the first digital audio signal dL
(2) A single wiring is sufficient for transmitting the digital audio signal dR. Further, in the present
embodiment, since the battery 80 is built in the left headphone unit 20L connected to the jack 31
via the first wiring group 42a, the first connection is made between the jack 31 and the left
headphone unit 20L. The wiring group 42a can be constituted by two lines of the first
transmission line 41a and the first reference potential line 43a. Therefore, according to the
present embodiment, the conventional two-wire jack can be diverted, and the wiring group 42
can be compared to a mode in which the first digital audio signal dL and the second digital audio
signal dR are transmitted by separate wirings. There is an advantage that the number of wires to
be configured can be reduced. In the present embodiment, the battery 80 is provided in the
headphone unit 20L for the left, but the battery 80 can also be provided in the headphone unit
20R for the right.
[0024]
C: Third Embodiment FIG. 4 is a block diagram showing a schematic configuration of a
headphone 10 according to a third embodiment of the present invention. As shown in FIG. 4, the
headphone 10 includes a headphone unit 20L for the left, a headphone unit 20R for the right, a
third unit 21 having a battery 80, and a jack 31 to which two lines can be independently
connected. , A first wiring group 44a connecting the jack 31 and the third unit 21, a second
wiring group 44b connecting the third unit 21 and the headphone unit 20L for the left, and the
third unit 21 for the right And a third wiring group 44c for connecting to the headphone unit
20R. Each of the headphone units 20L and 20R has the same configuration as that of the first
embodiment described above.
[0025]
The first wiring group 44a is constituted by two lines of a first transmission line 41c through
which the multiplexed digital audio signal dX is transmitted in serial form and a first reference
potential line 43c to which the reference potential GND is supplied. The battery 80 incorporated
in the third unit 21 outputs the power supply potential VDD based on the reference potential
GND to the first power supply line 45a. The first power supply line 45 a to which the power
supply potential VDD is supplied branches into the second power supply line 45 b and the third
power supply line 45 c and is connected to each headphone unit 20. As shown in FIG. 4, the
second wiring group 44b includes a second transmission line 41d branched from the first
transmission line 41c, and a second reference potential line 43d branched from the first
reference potential line 43c. It comprises three lines with the second power supply line 45b
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branched from the first power supply line 45a. The third wiring group 44c includes a third
transmission line 41e branched from the first transmission line 41c, a third reference potential
line 43e branched from the first reference potential line 45c, and a first power supply line. It
consists of three lines with the third power supply line 45c branched from 45a.
[0026]
Also in this embodiment, the multiplexed digital audio signal dX in serial format in which the first
digital audio signal dL and the second digital audio signal dR are multiplexed is transmitted to
the transmission line 41, so the first digital audio signal dL and the first digital audio signal dL
(2) A single wiring is sufficient for transmitting the digital audio signal dR. Further, in the present
embodiment, since the battery 80 for outputting the power supply potential VDD is built in the
third unit 21 connected to the jack 31 via the first wiring group 44a, the jack 31 and the third
unit 21 are provided. Can be formed by two lines of the first transmission line 41c and the first
reference potential line 43c. Therefore, the conventional two-wire jack can be diverted, and the
number of wires constituting the wire group 44 is reduced as compared with the aspect in which
each of the first digital audio signal dL and the second digital audio signal dR is transmitted by
separate wires. It has the advantage of being able to <D: Modifications> The present invention is
not limited to the above-described embodiments, and the following modifications are possible, for
example. Also, two or more of the modifications described below can be combined.
[0027]
(1) Modified Example 1 In each of the above-described embodiments, the aspect in which only
the multiplexed digital audio signal dX is input to the noise cancellation circuit 50 is illustrated,
but the present invention is not limited thereto. It is also possible that only the multiple analog
audio signal aX is input to. In this case, the level of the control signal S is fixed to a level that
selects the output signal of the analog signal receiver 52. The multiplexed analog audio signal aX
is multiplexed with the first analog audio signal aL and the second analog audio signal aR. The
analog signal receiver 52 separates the first analog audio signal aL or the second analog audio
signal aR from the multiplexed analog audio signal aX, and A / D converts this to output a digital
signal generated to the DSP 53. Alternatively, only one of the first analog audio signal aL and the
second analog audio signal aR may be input to the noise cancel circuit 50 illustrated in FIG. 5.
Also in this case, the level of the control signal S is fixed to a level at which the output signal of
the analog signal receiver 52 is selected, and the analog signal receiver 52 is a digital signal
generated by A / D converting the input analog signal a. The signal is output to the DSP 53. (2)
Modification 2 As shown in FIG. 6, in the noise cancellation circuit 50, the multiplexed analog
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audio signal aX and the multiplexed digital audio signal dX may be selectively supplied to the
noise cancellation circuit 50 via the jack 30. . In this case, the switch SW2 is disposed in the front
stage of the noise cancellation circuit 50, and the control signal S generated by the control circuit
(not shown) is supplied to the switches SW1 and SW2. Specifically, when the control signal S
designates the multiplexed digital audio signal dX, the switch SW2 operates to electrically
connect the transmission line 41 and the digital signal receiver 51, while the switch SW1 is a
digital signal receiver It operates so as to electrically connect 51 and the DSP 53. Conversely,
when the control signal S designates the multiple analog audio signal aX, the switch SW2
operates to electrically connect the transmission line 41 and the analog signal receiver 52, while
the switch SW1 operates in conjunction with the analog signal receiver 52. It operates so as to
conduct with the DSP 53.
[0028]
(3) Modification 3 FIG. 7 is a block diagram showing an example in which only the analog audio
signal a is input to the noise cancellation circuit 50 according to the present invention. As shown
in FIG. 7, the headphones 10 include headphone units 20L and 20R, a jack 30 to which three
wires can be independently connected, and a first wiring group 46a connecting the headphone
unit 20L for left and the jack 30. , And the second wiring group 46 b connecting the right
headphone unit 20 R and the jack 30. Each of the headphone units 20L and 20R has a noise
cancellation circuit 50, a noise pickup microphone 60, a speaker 70, and a battery 80 for
outputting the power supply potential VDD. The configuration of the noise cancellation circuit 50
is the same as that shown in FIG.
[0029]
The first wiring group 46a is a two-wire transmission line 48a to which the first analog audio
signal aL to be supplied to the headphone unit 20L for the left is supplied and a first reference
potential line 43f to which the reference potential GND is supplied. It consists of On the other
hand, the second wiring group 46b has a transmission line 48b to which the second analog audio
signal aR to be supplied to the headphone unit 20R for the right is supplied, and a second
reference potential branched from the first reference potential line 43f. It consists of two lines
with the line 43g. As shown in FIG. 7, to the jack 30, three lines of transmission lines 48a and
48b and a first reference potential line 43f are connected.
[0030]
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As described above, although the aspect in which the analog audio signal a is input to the noise
cancellation circuit 50 in the headphone unit 20 in which the battery 80 is built in has been
described, for example, as shown in FIG. Alternatively, only the multiple digital audio signal dX
may be input to the noise cancellation circuit 50 in the headphone unit 20. The headphone 10
shown in FIG. 8 has headphone units 20L and 20R, a jack 31 to which two wires can be
connected independently, and a wiring group 40 commonly connected to the headphone units
20L and 20R. Each of the headphone units 20L and 20R has a noise cancellation circuit 50, a
noise pickup microphone 60, a speaker 70, and a battery 80. The configuration of the noise
cancellation circuit 50 is the same as that shown in FIG. The wiring group 40 includes a first
wiring group 40a connecting the jack 31 and the headphone unit 20L for the left, and a second
wiring group 40b branched from the first wiring group 40a to the headphone unit 20R for the
right. Ru. Each of first wiring group 40a and second wiring group 40b is constituted by two lines
of transmission line 41 through which multiplexed digital audio signal dX in serial format is
transmitted and reference potential line 43 to which reference potential GND is supplied. Ru.
[0031]
In the configuration shown in FIG. 8, since the serial digital multiplexed digital signal dX in which
the first digital audio signal dL and the second digital audio signal dR are multiplexed is
transmitted to the transmission line 41, the first digital audio signal dL And, only one wire is
required to transmit the second digital audio signal dR. Further, since the battery 80 is built in
each headphone unit 20, each of the first wiring group 40a and the second wiring group 40b can
be constituted by two lines of the transmission line 41 and the reference potential line 43.
Therefore, according to the configuration shown in FIG. 8, there is an advantage that the
conventional two-wire jack can be diverted and the number of wires forming the wire group 40
can be reduced.
[0032]
In short, the headphone 10 according to the present invention includes the noise cancellation
circuit 50, the noise pickup microphone 60 or the microphone 61, and the speaker 70, and the
transmission line 41 to which the multiplexed digital audio signal dX is supplied in serial format.
It is sufficient that the wiring group 40 including at least two lines with the reference potential
line 43 to which the reference potential GND is supplied be connected to the noise cancellation
circuit 50. As in the first embodiment described above, the power supply line 45 supplied with
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the power supply potential VDD with reference to the reference potential GND may be included
in the wiring group 40, or the power supply line 45 may be connected to the wiring group 40.
Alternatively, the battery unit 80 may be incorporated in the headphone unit 20 in which the
noise cancellation circuit 50 is incorporated.
[0033]
(4) Modification 4 FIG. 9 is a block diagram showing another example in which only the analog
audio signal a is input to the noise cancellation circuit 50 according to the present invention. As
shown in FIG. 9, the headphone 10 includes headphone units 20L and 20R, a third unit 22
having a noise cancellation circuit 50 and a battery 80 built therein, and a jack 30 capable of
independently connecting three wires. And a first wiring group 400a for connecting the jack 30
and the third unit 22. As shown in FIG. 9, each of the headphone units 20L and 20R has a noise
pickup microphone 60 and a speaker 70. The third unit 22 is a battery that outputs the power
supply potential VDD based on the reference potential GND, the noise cancellation circuit 50L
corresponding to the headphone unit 20L for the left, the noise cancellation circuit 50R
corresponding to the headphone unit 20R for the right And 80. The first wiring group 400a
includes the transmission line 401 to which the analog audio signal aL to be supplied to the
headphone unit 20L for the left, the first reference potential line 403a to which the reference
potential GND is supplied, and the headphones for the right It comprises three lines with the
transmission line 405 to which the analog voice signal aR to be supplied to the unit 20R is
supplied. The first power supply line 407 a supplied with the power supply potential VDD from
the battery 80 is branched into a second power supply line 407 b and a third power supply line
407 c and is connected to each noise cancel circuit 50.
[0034]
As shown in FIG. 9, the second wiring group 400b is connected to the noise cancel circuit 50L.
The second wiring group 400b is a three-line transmission line 401 to which the analog audio
signal aL is supplied, a second reference potential line 403b branched from the first reference
potential line 403a, and a second power supply line 407b. Configured Further, the third wiring
group 400c is connected to the noise cancellation circuit 50R. The third wiring group 400c is a
three-line transmission line 405 supplied with the analog audio signal aR, a third reference
potential line 403c branched from the first reference potential line 403a, and a third power
supply line 407c. Configured The configuration of each noise cancellation circuit 50 is the same
as the configuration shown in FIG.
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[0035]
As described above, in the configuration in which the noise cancellation circuit 50 is
incorporated in the third unit 22 without being incorporated in the headphone unit 20, the
aspect in which only the analog audio signal a is input to the noise cancellation circuit 50 has
been described. As shown in FIG. 10, in the configuration in which the noise cancellation circuit
50 is incorporated in the third unit 22 without being incorporated in the headphone unit 20,
only the multiple digital audio signal dX is input to the noise cancellation circuit 50. It can also
be done. As shown in FIG. 10, noise cancel circuits 50L and 50R, and a first wiring group 410a
for connecting the third unit 22 incorporating the battery 80 and the jack 31 capable of
independently connecting two wires are serial. It comprises two lines of a first transmission line
411a through which a multiplexed digital audio signal dX is transmitted and a first reference
potential line 413a to which a reference potential GND is supplied. The first power supply line
415 a supplied with the power supply potential VDD from the battery 80 is branched into a
second power supply line 415 b and a third power supply line 415 c and is connected to each
noise cancel circuit 50.
[0036]
As shown in FIG. 10, the second wiring group 410b is connected to the noise cancellation circuit
50L. The second wiring group 410b includes a second transmission line 411b branched from the
first transmission line 411a, a second reference potential line 413b branched from the first
reference potential line 413a, and a second power supply line 415b. It consists of three lines.
Further, the third wiring group 410c is connected to the noise cancellation circuit 50R. The third
wiring group 410c includes a third transmission line 411c branched from the first transmission
line 411a, a third reference potential line 413c branched from the first reference potential line
413a, and a third power supply line 415c. It consists of three lines. The configuration of each
noise cancel circuit 50 is the same as the configuration shown in FIG.
[0037]
Also in the configuration shown in FIG. 10, since the serial digital multiplexed digital signal dX in
which the first digital audio signal dL and the second digital audio signal dR are multiplexed is
transmitted to the transmission line 411, the first digital audio signal dL And the second digital
audio signal dR has the advantage of requiring only one wiring.
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[0038]
(5) Modification 5 In the configuration shown in FIG. 10, the battery 80 is incorporated in the
third unit 22. For example, as shown in FIG. 11, the battery 80 is not incorporated in the third
unit 22. It can also be done.
In the configuration shown in FIG. 11, a jack 30 to which three lines can be independently
connected is provided, and a first wiring group 420a connecting the jack 30 and the third unit
22 is a serial digital digital audio signal dX. Is transmitted by a first transmission line 421a, a first
reference potential line 423a to which a reference potential GND is supplied, and a first power
supply line 425a to which a power supply potential VDD is supplied. As shown in FIG. 11, the
noise cancellation circuit 50L is connected to a second wiring group 420b branched from the
first wiring group 420a. The second wiring group 420b includes a second transmission line 421b
branched from the first transmission line 421a, a second reference potential line 423b branched
from the first reference potential line 423a, and a first power supply line 425a. It comprises
three lines with the branched second power supply line 425b. The third wiring group 420c
branched from the first wiring group 420a is connected to the noise cancellation circuit 50R. The
third wiring group 420c includes a third transmission line 421c branched from the first
transmission line 421a, a third reference potential line 423c branched from the first reference
potential line 423a, and a first power supply line 425a. It comprises three lines with the
branched third power supply line 425c.
[0039]
In short, the headphone 10 according to the present invention includes the noise cancellation
circuit 50, the noise pickup microphone 60 or the microphone 61, and the speaker 70, and the
transmission line to which the multiplexed digital audio signal dX is supplied in serial format, and
the power supply It is sufficient that the wiring group including at least two lines with the
reference potential line to which the reference potential GND serving as the reference of the
potential VDD is supplied be connected to the noise cancel circuit 50. The noise cancellation
circuit 50 may be incorporated in the headphone unit 20, or the noise cancellation circuit 50
may be incorporated in the third unit 22 without being incorporated in the headphone unit 20.
[0040]
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(6) Modification 6 In the above-described embodiments, the headphone units 20L and 20R are
for collecting the sound output from the noise pickup microphone 60 and the speaker 70 for
collecting noise from the outside. Although it is an aspect provided with either of the
microphones 61, for example, as shown in FIG. 12, each of the headphone units 20L and 20R
may be provided with both the noise pickup microphone 60 and the microphone 61. The noise
cancellation circuit 50 in the mode shown in FIG. 12 performs control operation combining
feedforward control and feedback control.
[0041]
(7) Modification 7 In each of the embodiments described above, the non-volatile memory 57
exemplifies a mode in which the parameter X for canceling noise is stored. However, the
parameter X is stored in the non-volatile memory 57 The aspect is optional. For example, the
parameter X may be written in advance in the non-volatile memory 57, or the parameter X may
be transmitted by the transmission line 41 and supplied to the non-volatile memory 57.
[0042]
(8) Modified Example 8 In each of the embodiments described above, the non-volatile memory
57 has at least a parameter X according to the acoustic characteristics of the sound collecting
device (for example, the noise pickup microphone 60) and the sound emitting device (for
example, the speaker 70). Although stored, the parameter is not limited to this but, for example,
parameters according to the position of the noise pickup microphone 60, the shape of the
headphone unit 20, etc. in addition to the acoustic characteristics of the noise pickup
microphone 60 and the speaker 70 in the non-volatile memory 57 It is also possible that X is
stored. Also in this embodiment, the DSP 53 performs an operation using the parameter X read
from the non-volatile memory 57 so as to cancel noise to generate the driving digital signal dT.
[0043]
It is a block diagram showing composition of a headphone concerning a 1st embodiment of the
present invention. It is a block diagram which shows the detailed structure of a noise cancellation
circuit. It is a block diagram showing composition of a headphone concerning a 2nd embodiment
of the present invention. It is a block diagram which shows the structure of the headphones
which concern on 3rd Embodiment of this invention. It is a block diagram which shows the
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detailed structure of a noise cancellation circuit. It is a block diagram which shows the detailed
structure of a noise cancellation circuit. It is a block diagram showing composition of a
headphone concerning a modification of the present invention. It is a block diagram showing
composition of a headphone concerning a modification of the present invention. It is a block
diagram showing composition of a headphone concerning a modification of the present
invention. It is a block diagram showing composition of a headphone concerning a modification
of the present invention. It is a block diagram showing composition of a headphone concerning a
modification of the present invention. It is a block diagram showing composition of a headphone
concerning a modification of the present invention.
Explanation of sign
[0044]
DESCRIPTION OF SYMBOLS 10 ...... Headphones, 20 ...... Headphones unit, 30, 31 ...... Jack, 40 ......
Wiring group, 41 ...... Transmission line, 43 ...... Reference electric potential line, 45 ...... Power
supply line, 50 ...... Noise cancellation circuit, 51: receiver for digital signal 52: receiver for analog
signal 55: class D amplifier circuit 56: A / D converter circuit 57: non-volatile memory 60: noise
pickup microphone 61: ... microphone, 70 ... speaker, 80 ... battery, d ... digital audio signal, dX ...
multiplexed digital audio signal, GND ... reference potential, VDD ... power supply potential.
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