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DESCRIPTION JP2016127556

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DESCRIPTION JP2016127556
Abstract: To provide a condenser microphone unit and a condenser microphone capable of
preventing the flow of high frequency current into the inside of the condenser microphone unit.
An electroacoustic transducer (30) comprising a diaphragm (32) and a fixed pole (33)
constituting a capacitor, a circuit board (50) comprising an impedance transducer (40) connected
to the electroacoustic transducer, an electroacoustic transducer and a circuit A bottomed
cylindrical unit case 20 having an opening for receiving the substrate, and a hole 50h through
which the first filter element L is inserted in the thickness direction of the circuit board; It is
characterized in that the element and the impedance converter are connected. [Selected figure]
Figure 1
コンデンサマイクロホンユニットとコンデンサマイクロホン
[0001]
The present invention relates to a condenser microphone unit and a condenser microphone.
[0002]
An electret condenser microphone unit (hereinafter referred to as “unit”).
There exist some in which the field effect transistor (FET: Field Effect Transistor) which
comprises an impedance converter is incorporated.
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[0003]
When a strong electromagnetic wave such as a cellular phone is applied to the unit, a high
frequency current is generated to enter the inside of the unit. At this time, the FET detects a high
frequency current and outputs it as noise. Until now, various proposals have been made to avoid
the generation of this noise (see, for example, "Patent Document 1").
[0004]
One way to avoid the generation of the noise is to attach a capacitor to a printed circuit board
(PCB) incorporated in the unit and short circuit at high frequency. The effect of short-circuiting in
high frequency is dependent on frequency depending on the type of capacitor attached and the
size of capacitance. Therefore, a method of connecting capacitors of different capacitances in
parallel is used.
[0005]
FIG. 9 is a schematic view of a longitudinal section of a conventional unit. The unit 100 includes
a unit case 200, an electroacoustic transducer 30, an impedance transducer 40 of the
electroacoustic transducer 30, and a circuit board 500.
[0006]
Unit case 200 is a bottomed cylindrical shape having an opening on the lower side of the
drawing sheet in the figure, and is made of a press-formed product of a metal material such as
aluminum. A sound wave introduction hole 200 h through which sound waves from a sound
source pass is formed on the opposing surface (upper side of the drawing) of the opening of the
unit case 200.
[0007]
The electroacoustic transducer 30 includes a spacer 31, a diaphragm 32, a fixed electrode 33, a
diaphragm holder 34, and an insulator 35.
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[0008]
The diaphragm 32 and the fixed electrode 33 are disposed to face each other via the spacer 31
to constitute a capacitor.
An air layer having a width corresponding to the thickness of the spacer 31 is formed between
the diaphragm 32 and the fixed electrode 33.
[0009]
For the diaphragm 32, a thin film of synthetic resin having a metal (preferably gold) vapor
deposition film on one side is used. The diaphragm 32 is stretched on the diaphragm holder 34
in a state where a predetermined tension is applied.
[0010]
As the fixed electrode 33, a metal porous plate having a plurality of sound holes 33h through
which sound waves pass is used. The fixed electrode 33 may be provided with an electret
dielectric film. The fixed electrode 33 is fixed to a cylindrical insulator 35 made of synthetic
resin.
[0011]
The disk-shaped circuit board 500 is arranged to cover the opening of the bottomed cylindrical
unit case 200, and is curled (caulked) applied to the rear end edge of the unit case 200 into the
unit case 200. It is fixed. The impedance converter 40 is disposed on the surface of the circuit
board 500 fixed to the unit case 200, which is located inside the unit case 200. A capacitor C1 is
disposed on the surface of the circuit board 500 located outside the unit case 200.
[0012]
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The FET 44 includes a gate electrode 41, a drain electrode 42, and a source electrode 43. The
gate electrode 41 is electrically connected to the fixed electrode 33. Since the drain electrode 42
and the source electrode 43 are at overlapping positions in the figure, only one of them is shown
in the figure.
[0013]
A hole 500 h is formed in the circuit board 500 in the thickness direction (vertical direction in
the drawing) of the circuit board 500. Solder pads (signal lands SL and ground lands GL) in which
the drain electrode 42 and the source electrode 43 are soldered with solder S on the surface of
the circuit board 500 fixed to the unit case 200 on the outside of the unit case 200. Is formed. A
microphone cable (not shown) is connected to the solder pad.
[0014]
FIG. 10 is an equivalent circuit of the conventional unit 100 shown in FIG. The figure shows that
the capacitor C 1 is connected to the impedance converter 40 via the drain electrode 42 and the
source electrode 43 of the FET 44. The capacitor C1 functions as a so-called bypass capacitor,
and the FET 44 can be prevented from detecting the high frequency current by short circuiting
(bypassing) the above-mentioned high frequency current to the ground for removal.
[0015]
As described above, in order to enhance the effect of preventing the above-described high
frequency current from entering the inside of the unit case 200, it is also conceivable to use an
inductor for connection inside and outside the unit case 200. However, when the inductor is
disposed outside the electrostatic shield of the unit case 200, removal of the high frequency
current becomes incomplete. Therefore, the effect of preventing the inflow of high frequency
current into the inside of unit case 200 is inferior. On the other hand, when the inductor is
disposed inside the unit case 200, the unit size is disadvantageous because the capacity of the air
chamber inside the unit case 200 needs to be secured.
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[0016]
Here, in the case of the nondirectional unit, the circuit board 500 also plays a role of sealing the
air chamber inside the bottomed cylindrical unit case 200, and it is disadvantageous if the circuit
board 500 has an opening. That is, it is desirable that the back surface (air chamber) of the
diaphragm 32 be made airtight without the circuit board 500 leaking air, and the inflow of high
frequency current into the inside of the unit case 200 can be prevented.
[0017]
JP, 2010-288049, A
[0018]
The present invention has been made to solve the problems of the prior art as described above,
and provides a condenser microphone unit and a condenser microphone capable of preventing
the flow of high frequency current into the inside of the condenser microphone unit. The purpose
is
[0019]
The present invention accommodates an electroacoustic transducer provided with a diaphragm
and a fixed pole constituting a capacitor, a circuit board provided with an impedance transducer
connected to the electroacoustic transducer, an electroacoustic transducer, and the circuit board.
A bottomed cylindrical unit case having an opening is provided, and a hole through which the
first filter element is inserted is provided in the thickness direction of the circuit board, and the
first filter element and the impedance converter are connected To be characterized.
[0020]
According to the present invention, it is possible to prevent the inflow of high frequency current
into the inside of the condenser microphone unit.
[0021]
It is a schematic diagram of the longitudinal cross section which shows embodiment of the
capacitor | condenser microphone unit concerning this invention.
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It is a schematic diagram which shows the penetration hole provided in the circuit board of the
said capacitor | condenser microphone unit.
It is a schematic diagram which shows the example of the inductor penetrated by the said
penetration hole.
It is a top view of the above-mentioned condenser microphone unit.
It is a bottom view of the above-mentioned condenser microphone unit. It is an equivalent circuit
of the said capacitor | condenser microphone unit. FIG. 1 is an external view showing an
embodiment of a condenser microphone according to the present invention. It is the components
exploded view of the above-mentioned condenser microphone. It is a schematic diagram of the
longitudinal cross-section of the conventional condenser microphone unit. It is an equivalent
circuit of the conventional condenser microphone unit.
[0022]
Hereinafter, embodiments of a condenser microphone unit and a condenser microphone
according to the present invention will be described with reference to the drawings.
[0023]
Among the members constituting the condenser microphone unit according to the present
invention described below, the same members constituting the conventional condenser
microphone unit shown in FIGS. 9 and 10 are denoted by the same reference numerals.
[0024]
Condenser Microphone Unit FIG. 1 is a condenser microphone unit (hereinafter referred to as
“unit”) according to the present invention.
Is a schematic longitudinal sectional view showing an embodiment of the present invention.
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[0025]
The unit 10 includes a unit case 20, an electroacoustic transducer 30, an impedance converter
40, and a circuit board (PCB) 50.
[0026]
The unit case 20 has a bottomed cylindrical shape and is made of a press-formed product of a
metal material such as aluminum.
The front end side (upper side in the drawing) corresponding to the bottom of the unit case 20 is
the side directed to the sound source side at the time of sound collection.
On the other hand, an opening is formed on the rear end surface side (lower side in the drawing)
of the unit case 20, and the electroacoustic transducer 30 and the impedance converter 40 are
accommodated in the unit case 20 from this opening.
[0027]
The electroacoustic transducer 30 includes a diaphragm 32 and a fixed electrode 33 which are
disposed to face each other via a thin ring-shaped spacer 31 made of synthetic resin or the like.
Between the diaphragm 32 and the fixed electrode 33, an air layer (gap) having a width
corresponding to the thickness of the spacer 31 is formed.
[0028]
The diaphragm 32 is formed of a disc-like thin film made of synthetic resin or the like and is
stretched by a diaphragm holder (diaphragm ring) 34.
[0029]
The fixed pole 33 is in the shape of a disc made of metal, and constitutes a capacitor with the
diaphragm 32 disposed opposite to the fixed pole 33.
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An electret plate is attached to at least one surface side of the fixed electrode 33, for example, the
opposite surface side to the diaphragm 32, to constitute an electret board.
[0030]
The impedance converter 40 is an impedance converter of the electroacoustic converter 30. A
field effect transistor (FET) constituting the impedance converter 40 includes a gate electrode 41,
a drain electrode 42, and a source electrode 43. The gate electrode 41 is electrically connected to
the fixed electrode 33. Since the drain electrode 42 and the source electrode 43 are at
overlapping positions in the figure, only one of them is shown in the figure.
[0031]
Circuit board 50 has a disk shape having a first surface located on the inner side of unit case 20
and a second surface located on the outer side of unit case 20 when fixed in unit case 20. is
there. The circuit board 50 is arranged to close the opening of the unit case 20 and is fixed in the
unit case 20 by curling (caulking) applied to the rear end edge of the unit case 20. On the circuit
board 50, solder pads (signal lands SL and ground lands GL) to which the drain electrode 42 and
the source electrode 43 are soldered are formed.
[0032]
The circuit board 50 is connected to an audio signal output circuit board PCB (see FIG. 8)
described later via a cable (not shown). For this cable, for example, a two-core shielded wire
having a feeder, a signal wire, and a shielded wire is used. The audio signal from the unit 10 is
output to the audio signal output circuit board PCB via this cable. The feed line is connected to
the drain electrode 42. The signal line is connected to the source electrode 43. The shield
covering wire is connected to the ground pattern (ground land GL) of the circuit board 50. For
example, a phantom power source is used as a power source for supplying power to the drain
electrode 42.
[0033]
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An impedance converter 40 is disposed on the first surface of the circuit board 50. A capacitor
(capacitor element) C1 as a second filter element is disposed on the second surface of the circuit
board 50.
[0034]
FIG. 2 is a schematic view showing an insertion hole provided in the circuit board 50. As shown
in FIG. As shown in the figure, the circuit board 50 is provided with a hole 50 h which is not a
through hole in the thickness direction (vertical direction in the drawing) of the circuit board 50.
When the circuit board 50 is fixed in the unit case 20, the holes 50h provided in the circuit
board 50 communicate the inside of the unit case 20 with the outside.
[0035]
Solder pads are formed on the periphery (periphery) of the hole 50 h on the first surface and the
second surface of the circuit board 50. The capacitor C1, the chip coil, and the impedance
converter 40 are electrically connected by soldering the two ends (upper and lower ends in the
drawing) of the chip coil inserted into the holes 50h to the solder pads.
[0036]
FIG. 3 is a schematic view showing an example of the inductor inserted into the insertion hole
50h. The figure shows that the chip coil (inductor element) L as a first filter element is inserted
into the hole 50 h.
[0037]
After the chip coil L is inserted into the hole 50h, as shown in FIG. 1, the gap between the hole
50h and the chip coil L is sealed by soldering the both ends of the chip coil L with the solder S.
That is, the hole 50 h is sealed by the solder S between the chip coil L inserted into the hole 50 h
and the solder pad. As a result, air does not leak from the hole 50 h, and an air chamber is
formed in the unit case 20.
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[0038]
4 is a plan view of the unit 10, and FIG. 5 is a bottom view of the unit 10. As shown in FIG. 5, the
chip coil L inserted into the insertion hole 50h of the circuit board 50 is soldered with the signal
land SL formed on the periphery of the insertion hole 50h by the solder S and electrically
connected to the capacitor C1. Connecting.
[0039]
On the other hand, on the first surface of the circuit board 50, a capacitor C2 as a third filter
element is disposed. By electrically connecting the chip coil L and the capacitor C2, a π-type
filter is configured by the capacitor C1, the chip coil L, and the capacitor C2.
[0040]
FIG. 6 is an equivalent circuit of a unit 10 incorporating a π-type filter composed of a capacitor
C1, a chip coil L and a capacitor C2. The figure shows that the chip coil L is connected in series to
the impedance converter 40. The capacitor C1 is connected to the impedance converter 40
including the resistor R and the diodes D1 and D2 through the chip coil L inserted into the hole
50h and soldered to the solder pad, or the capacitor C2 Shows that it is connected to the FET 44
through the drain electrode 42 and the source electrode 43. The capacitors C1 and C2 shortcircuit (bypass) the above-mentioned high-frequency current to the ground to remove them,
thereby preventing the FET 44 from detecting the high-frequency current.
[0041]
According to the embodiment described above, since the chip coil L is embedded so as to be
embedded in the circuit board 50, the chip coil L is not disposed outside the electrostatic shield
of the unit case 20, and Inflow into the inside of the unit case 20 can be prevented.
[0042]
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Further, since the chip coil L is built in the circuit board 50, the capacity of the air chamber
inside the unit case 20 can be secured, which is advantageous for the downsizing of the unit 10.
Furthermore, since the circuit components of the unit 10 can be three-dimensionally arranged,
the circuit pattern of the unit 10 can be simplified, and the unit 10 is less susceptible to external
noise.
[0043]
Condenser Microphone Next, an embodiment of a condenser microphone according to the
present invention will be described. FIG. 7 is an external view showing an embodiment of a
condenser microphone according to the present invention, and FIG. 8 is an exploded view of
parts of the condenser microphone shown in FIG.
[0044]
The condenser microphone 1 according to the present invention is, for example, a goose neck
type, and includes a cap 2, a microphone case 3A, a microphone case 3B, a goose neck pipe 4A, a
pipe 5, a joint 6, a goose neck pipe 4B, and a connector case 7. , Has. In the following description,
although the goose neck microphone is described as an example, the condenser microphone
according to the present invention is applicable not only to the goose neck microphone, but, for
example, a microphone unit such as a lavelia microphone or a wireless microphone The present
invention is applicable to microphones that are required to be miniaturized.
[0045]
In the microphone case 3A, the condenser microphone unit 10 according to the present
invention described above and the audio signal output circuit board PCB for the condenser
microphone unit 10 are accommodated. At the time of sound collection, the cap 2 is placed on
one end side (the lower side of the paper surface) of the microphone case 3A directed to the
sound source side, and the gooseneck pipe 4A is disposed on the other end side (the upper
surface of the paper surface) of the microphone case 3A via the microphone case 3B. Combined.
The goose neck pipe 4A is coupled to one end side of a pipe 5 made of a metal straight pipe. One
end side of the goose neck pipe 4B is coupled to the other end side of the pipe 5 via the joint 6. A
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connector case 7 incorporating a connector 8 is coupled to the other end of the goose neck pipe
4B.
[0046]
The connector 8 is, for example, an output connector having a first pin for grounding specified in
EIAJ RC-5236 “Latch-lock type round connector for audio equipment” and a second pin on the
hot side of the signal and a third pin on the cold side. It is.
[0047]
The audio signal output circuit board PCB incorporates a balanced transmission circuit.
The audio signal output circuit board PCB and the connector 8 are electrically connected via the
microphone cable 9. The microphone cable 9 is a two-core shield-covered wire having two types
of signal lines and shield-covered wires on the hot (HOT) side and the cold (COLD) side, which
are inserted into the goose neck pipes 4A and 4B and the pipe 5. .
[0048]
The shielded cable of the microphone cable 9 is connected to, for example, the ground (ground
circuit) of the audio signal output circuit board PCB. The ground of the audio signal output circuit
board PCB is connected to the first pin of the connector 8, and the first pin is also connected to a
shield housing (not shown). In the connector 8 and the microphone cable 9, the signal line on the
hot side of the microphone cable 9 is connected to the second pin of the connector 8, and the
signal line on the cold side of the microphone cable 9 is connected to the third pin on the
connector 8. , Shield covering wire is connected to the first pin of the connector 8.
[0049]
The condenser microphone unit 10 has the FET 44 including the gate electrode 41, the drain
electrode 42, and the source electrode 43 as described above. Two types of signal lines of the
microphone cable 9 are connected to the source electrode 43 through the audio signal output
circuit board PCB. The audio signal output from the FET 44 is an unbalanced signal. The audio
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signal output from the FET 44 as an unbalanced signal is converted to a balanced signal by the
audio signal output circuit board PCB and output to the microphone cable 9.
[0050]
Since the condenser microphone unit 10 provided in the condenser microphone 1 is the
condenser microphone unit according to the present invention described above, generation of
noise is prevented by preventing the high frequency current from flowing into the condenser
microphone unit 10 as described above. Can be suppressed.
[0051]
Reference Signs List 1 condenser microphone 2 cap 3 microphone case 4 goose neck pipe 5 pipe
6 joint 7 connector case 8 connector 9 microphone cable 10 microphone unit 20 unit case 20 h
sound wave introduction hole 21 bent portion 30 electroacoustic transducer 31 spacer 32
diaphragm 33 fixed pole 33h sound hole 34 diaphragm holder 35 insulator 40 impedance
converter 41 gate electrode 42 drain electrode 44 source electrode 44 field effect transistor
(FET) 50 circuit board 50h insertion hole C1 capacitor C2 capacitor L chip inductor D1 diode D2
diode R resistance S Solder SL Signal land GL Ground land PCB Audio signal output circuit board
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