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JP2006270663

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DESCRIPTION JP2006270663
PROBLEM TO BE SOLVED: To reliably prevent an electric shock accident without causing a drop
in output sound pressure in a condenser headphone which is used by applying a high
polarization voltage to a diaphragm. SOLUTION: A polarization voltage is applied to the
diaphragm 10 from a predetermined DC power supply 40 including a diaphragm 10 and fixed
poles 20F and 20R consisting of a porous plate arranged as a left / right pair on both sides
thereof In a capacitor headphone in which a signal voltage for sound reproduction is applied to
the poles 20F and 20R from a sound signal source, fixed electrode foils are formed on both sides
of each of the fixed poles 20F and 20R as nonconductive one another. Signal voltage is applied to
one of the fixed electrode foils 23Fb and 22Ra facing the diaphragm 10 of each double-sided
printed circuit board, and the other fixed electrode foil 22Fa disposed on the ear E side of the
user is connected to the ground . [Selected figure] Figure 1
コンデンサヘッドホン
[0001]
The present invention relates to condenser headphones, and more particularly, to a technique for
preventing electric shock to a user wearing headphones.
[0002]
For example, as described in Patent Document 1, a condenser headphone is provided with an
electroacoustic transducer in which fixed poles are disposed as a left and right pair on both sides
of a diaphragm.
10-05-2019
1
In this type of condenser headphone, while applying a polarization voltage of about 500 V to the
diaphragm, the diaphragm is vibrated to output sound by applying a signal voltage for sound
reproduction to each fixed pole. The level of audio output is proportional to the polarization
voltage and the signal voltage.
[0003]
Normally, the polarization voltage and the signal voltage are supplied from a headphone
additional device called an adapter or a dedicated headphone amplifier, but the signal voltage
applied to each fixed pole is about 600 V in peak value at the maximum sound pressure output.
Become.
[0004]
Generally, it is said that reducing the volume from the diaphragm to the tympanic membrane is
effective to increase the output sound pressure of headphones, but in the case of condenser
headphones, it is necessary to vibrate to increase the output sound pressure. To reduce the
volume from the plate to the tympanic membrane, a fixed pole will be placed near the ear.
Therefore, there is a risk of electric shock due to the signal voltage.
[0005]
The risk of this electric shock can be solved by interposing an electrically insulating perforated
plate between the unit including the fixed pole and the ear, but in this case, between the unit and
the perforated plate, the perforated plate and the ear Because an acoustically appropriate space
is required between the two, the volume between the unit and the ear increases and the output
sound pressure decreases.
[0006]
In addition, in the condenser headphone, in order to prevent insulation deterioration of the unit
due to perspiration of the human body, a moisture-proof film made of a plastic film is inserted
between the fixed electrode and the ear. Since the thickness is only about 1 to 2 μm, no effect
can be expected to prevent electric shock.
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2
[0007]
Japanese Patent Publication No. 58-27720
[0008]
Therefore, it is an object of the present invention to reliably prevent an electric shock accident
without causing a drop in the output sound pressure in a condenser headphone which is used by
applying a high polarization voltage to the diaphragm and to use it with confidence. It is about
being able to do it.
[0009]
In order to prevent the above problems, the present invention includes a diaphragm and fixed
electrodes consisting of a porous plate arranged as a pair on the left and right sides of the
diaphragm, and the polarization voltage is applied to the diaphragm from a predetermined DC
power supply. In a capacitor headphone to which a signal voltage for sound reproduction is
applied from the audio signal source to each of the fixed poles, a fixed electrode foil is formed on
both sides of each fixed pole so as to be nonconductive to each other. Is used, the signal voltage
is applied to one of the fixed electrode foils facing the diaphragm of each double-sided printed
circuit board, and the other fixed electrode foil of the double-sided printed circuit board disposed
on the ear of the user is grounded It is characterized by being connected to.
[0010]
In the present invention, the other fixed electrode foil of the double-sided printed circuit board
may be connected to the ground so as to have substantially the same potential as the human
body of the user (headphone wearer). The side winding is connected between the middle point of
the secondary winding of the input transformer connected to the audio signal source and the
diaphragm, and the one fixed electrode foil of each of the fixed poles is the secondary In the case
of a push-pull type connected to each one end of the side winding, it is preferable to be
connected to the ground together with the middle point of the secondary side winding.
[0011]
According to the condenser headphone of the present invention, since the fixed electrode foil
disposed close to the user's ear is grounded, there is no risk of electric shock even if the
headphone unit is brought close to the ear.
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3
Further, since the headphone unit can be brought close to the ear, the output sound pressure can
be increased.
In addition, by adopting a double-sided printed circuit board as the fixed electrode, it is possible
to produce a fixed electrode of uniform quality at low cost.
[0012]
Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3,
but this embodiment does not limit the present invention.
FIG. 1 is a schematic view showing the main part of a condenser headphone according to the
present invention, FIG. 2 is an enlarged sectional view of a fixed electrode applied to the present
invention, and FIGS. It is a top view which shows a field.
[0013]
As shown in FIG. 1, the headphone unit 1 of this condenser headphone includes a diaphragm 10
and fixed poles 20F and 20R disposed on both sides of the diaphragm 10. In this case, one fixed
pole 20F is The fixed pole 20R is a back fixed pole which is a front fixed pole disposed on the
user's ear E side.
The headphone unit 1 is housed in a housing having an ear pad (not shown).
[0014]
For the diaphragm 10, for example, a film member in which a metal deposition film is formed on
a synthetic resin thin film such as PET (polyethylene terephthalate) or PPS (polyphenylene
sulfide) can be used.
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4
The diaphragm 10 is held between the pair of spacer rings 11 and 11 in a state where a
predetermined tension is applied.
[0015]
Both the front side fixed pole 20F and the back side fixed pole 20R are made of a double-sided
printed circuit board having the same configuration, and FIG. 2 shows the double-sided printed
board 20 used as each fixed pole as a cross section.
The double-sided printed circuit board 20 is a porous plate having a large number of holes
(sound holes) 21 for passing sound, and fixed electrode foils 22 and 23 made of, for example, a
copper foil material are formed on both sides thereof.
[0016]
3 (a) and 3 (b) show the pattern shapes of the fixed electrode foils 22 and 23. In practice, after
the fixed electrode foils 22 and 23 are formed as, for example, a circular solid pattern, a large
number of sound holes 21 are formed. It is drilled. Therefore, the sound holes 21 are simply
through holes with no copper foil on the inner surface, and the fixed electrode foils 22 and 23
are nonconductive.
[0017]
Assuming that one fixed electrode foil of the front side fixed electrode 20F is 22Fa and the other
fixed electrode foil is 23Fb, one fixed electrode foil of the back side fixed electrode 20R is 22Ra,
and the other fixed electrode foil is 23Rb, In the side fixed electrode 20F, the fixed electrode foil
23Fb is opposed to the diaphragm 10, and in the back side fixed electrode 20R, the fixed
electrode foil 22Ra is opposed to the diaphragm 10, and the diaphragm is interposed through the
spacer rings 11 and 11, respectively. Assembled on both sides of 10
[0018]
In order to drive the headphone unit 1, an input transformer 30 and a DC power supply 40 for
generating a polarization voltage are used.
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5
The primary winding 31 of the input transformer 30 is connected to an audio signal source (not
shown). A center tap 30 c is drawn out of the secondary winding 32 of the input transformer 30.
The midpoint tap 30c is connected to ground.
[0019]
That is, the secondary winding 32 of the input transformer 30 is divided into two winding
portions 32a and 32b by the middle point tap 30c, and one end of one of the winding portions
32a is a fixed electrode foil of the front side fixed pole 20F. 23Fb, and one end of the other
winding portion 32b is connected to the fixed electrode foil 22Ra of the back side fixed electrode
20R.
[0020]
The DC power supply 40 is connected between the diaphragm 10 and the midpoint tap 30 c and
applies a polarization voltage of, for example, 500 V to the diaphragm 10.
The signal voltage applied to the primary winding 31 of the input transformer 30 from an audio
signal source (not shown) is fixed in such a manner that one of the winding portions 32a and
32b of the secondary winding 32 has positive phase and the other has negative phase. It is added
to the electrode foil 23Fb and the fixed electrode foil 22Ra.
[0021]
Thus, the diaphragm 10 is driven by the push-pull action of the fixed electrode foil 23Fb and the
fixed electrode foil 22Ra, but the signal voltages applied to the fixed electrode foils 23Fb and
22Ra have peak values at the maximum sound pressure output. There is a risk of electric shock
as it will reach about 600V.
[0022]
Therefore, in order to prevent such an electric shock accident, in the present invention, the fixed
electrode foil 22Fa located on the ear E side of the human body on the front side fixed electrode
20F is connected to the ground so that the same potential as the human body is obtained. .
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6
[0023]
In the example of FIG. 1, the fixed electrode foil 22Fa is dropped to the ground together with the
center point tap 30c of the secondary winding 32, but separately, an adapter (not shown) or the
like in which the input transformer 30 and the DC power supply 40 are accommodated It may be
connected to the ground terminal provided in the dedicated headphone amplifier.
[0024]
According to this, since the fixed electrode foil 22Fa located on the human ear E side of the front
side fixed electrode 20F has almost the same potential as the human body, there is a risk of
electric shock even if the headphone unit 1 is brought close to the ear E It disappears.
Moreover, since the headphone unit 1 can be brought close to the ear E, the output sound
pressure can be increased.
The present invention is also applicable to condenser headphones other than the above-described
push-pull.
[0025]
The schematic diagram which shows the principal part of the capacitor ¦ condenser headphone
by this invention.
The expanded sectional view of the fixed pole applied to the present invention. (A) and (b) are top
views which show one side and the other side of a fixed pole.
Explanation of sign
[0026]
DESCRIPTION OF SYMBOLS 1 headphone unit 10 diaphragm 11 spacer ring 20 double-sided
printed circuit board 20F, 20R fixed pole 21 sound hole 22Fa, 23Fb, 22Ra, 23Rb fixed electrode
foil 30 input transformer 31 primary winding 32 secondary winding 32a, 32b winding part 32c
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midpoint tap 40 DC power supply
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8
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