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DESCRIPTION JPH1051888

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DESCRIPTION JPH1051888
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker device for sound reproduction and an audio reproduction system using the same.
[0002]
2. Description of the Related Art Various types of loudspeakers can be considered and put to
practical use as loudspeakers for sound reproduction.
[0003]
For example, a magnetic circuit having an air gap between the center pole portion of the center
pole yoke and the plate is formed by sandwiching the magnet by the center pole yoke and the
plate, and the center pole portion or A speaker unit in which a primary coil is fixed to a plate and
fixed to a diaphragm so as to face this, and a secondary coil constituting a short coil is disposed
in an air gap of a magnetic circuit is an electromagnetic coupling (electromagnetic induction
type) speaker It has been put to practical use.
[0004]
In this electromagnetically coupled speaker, the secondary current is induced in the secondary
coil by the signal current flowing in the primary coil, and the interaction with the magnetic flux
generated in the air gap of the magnetic circuit causes the secondary coil to The driving force
corresponding to the next current is generated, and the diaphragm to which the secondary coil is
fixed is displaced.
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[0005]
In this electromagnetically coupled speaker, the primary coil through which the signal current
flows is fixed to a center pole portion or a plate made of a magnetic material such as iron, so that
it has excellent heat dissipation and has an advantage of being able to withstand a large input.
Further, if the secondary coil constituting the short coil is formed of a non-magnetic conductive
material such as aluminum and made of a pipe or a cylinder for one turn, distortion can be
reduced.
[0006]
On the other hand, a dynamic (conductive) speaker in which a voice coil is disposed in the air gap
of a magnetic circuit has been put to practical use, and in this dynamic speaker, power is
supplied to the voice coil and it is unnecessary for a vibration system including the voice coil. In
order to prevent vibration and resistance, the voice coil is connected to an input terminal
provided on the speaker frame by a coil lead wire made of a tinsel wire.
[0007]
Also, with this dynamic speaker, the voice coil may be divided into the number of bits of the
digital audio signal, and each coil may be directly driven with data of each bit, corresponding to
each bit of the digital audio signal. It is considered.
[0008]
As described above, the electromagnetically coupled speaker has the advantages of being
excellent in heat dissipation and being able to withstand a large input, and also capable of
reducing distortion.
However, if the length of the air gap of the magnetic circuit is increased, the sensitivity of the
speaker is reduced, so the number of turns of the primary coil and the secondary coil can not be
increased.
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[0009]
Therefore, the inductance of the primary coil and the secondary coil can not be increased, and
the electromagnetic coupling force in which the secondary current is induced in the secondary
coil by the signal current flowing in the primary coil is low in a low frequency range of several
kHz to 1 kHz or less As it becomes smaller, it is impossible to play up to 20 Hz, which is
necessary for playing audio.
Therefore, the electromagnetic coupling speaker is mainly used as a speaker for high-pitched
sound reproduction.
[0010]
On the other hand, as described above, in the dynamic speaker, the voice coil is connected to the
input terminal provided on the speaker frame by the coil lead wire formed of a tinsel wire.
In addition, it has been considered to divide the voice coil into the number of bits of the digital
audio signal using a dynamic speaker and directly drive each coil with data of each bit of the
digital audio signal.
[0011]
However, at present, when digitizing an audio signal, it is common to set the digital audio signal
to 16 bits for faithful reproduction of the audio.
Therefore, in the case of driving a voice coil with a digital audio signal in a dynamic speaker, 16
pairs of coil lead wires are required for one speaker.
[0012]
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However, since the tinsel cords, which are the lead wires of the coils, largely shake with the
vibration of the voice coil, the distance between them can not be reduced. Therefore, it is quite
difficult to provide as many as 16 pairs of tinsel cords in a small speaker.
[0013]
Therefore, in the present invention, reproduction to the low frequency range is enabled by the
electromagnetic coupling speaker.
[0014]
SUMMARY OF THE INVENTION In the present invention, a primary coil is fixed in the vicinity of
the air gap of a magnetic circuit in which the air gap is formed, and is fixed to a diaphragm, and a
secondary coil is disposed in the air gap, A speaker unit in which a secondary current is induced
in the secondary coil by the signal current flowing through the primary coil and the diaphragm is
displaced; a speaker drive circuit for driving the primary coil of the speaker unit by a digital
audio signal; Provide
[0015]
The sampling frequency for digitizing the audio signal is, for example, 44.1 kHz or 48 kHz, which
is a high frequency around 20 kHz, which is said to be the upper limit of the audio frequency.
Therefore, low frequency components such as several kHz to 1 kHz or less of the voice signal
before being digitized are also high frequencies exceeding 20 kHz as the digital voice signal.
[0016]
In addition, the electromagnetic coupling speaker reduces the length of the air gap of the
magnetic circuit so as not to cause a decrease in the speaker sensitivity, and reduces the number
of turns of the primary coil and the secondary coil. When the frequency is as high as 20 kHz or
more, the electromagnetic coupling force does not decrease, and sound can be reproduced.
[0017]
Then, in the speaker device of the present invention configured as described above, since the
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primary coil of the electromagnetic coupling speaker is driven by the digital audio signal, the low
frequency component of the audio signal before being digitized is also the primary. The signal
current flowing through the coil has a high frequency exceeding 20 kHz.
Therefore, the electromagnetic coupling speaker enables reproduction up to the low frequency
range.
[0018]
Further, in the present invention, the primary coil is fixed in the vicinity of the air gap of the
magnetic circuit in which the air gap is formed, fixed to the diaphragm, the secondary coil is
disposed in the air gap, and the signal current flowing in the primary coil A speaker unit in which
a secondary current is induced in the secondary coil and the diaphragm is displaced, and a
speaker drive circuit for driving the primary coil of the speaker unit by an analog audio signal,
and the speaker drive circuit Is to interrupt the analog audio signal at a frequency higher than
the audio frequency.
[0019]
In the speaker apparatus of the present invention thus configured, since the analog audio signal
is intermittently interrupted at a frequency higher than the audio frequency and supplied to the
primary coil of the electromagnetically coupled speaker, the low frequency component of the
analog audio signal is also the primary The signal current flowing through the coil has a high
frequency exceeding 20 kHz.
Therefore, the electromagnetic coupling speaker enables reproduction up to the low frequency
range.
[0020]
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of an audio
reproduction system using a speaker apparatus according to the present invention, which is a
case where audio is reproduced by a digital audio signal from a digital audio output apparatus.
[0021]
The digital audio output device 210 is a CD player or DAT (digital audio tape recorder) or the
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like, and consists of left and right audio signals digitized from its digital output terminal to 16
bits at a sampling frequency of 44.1 kHz or 48 kHz, for example. Stereo audio signals are output
as serial data alternately for every one sample for left and right audio data.
[0022]
The 16-bit digital audio signal of serial data from the digital audio output device 210 is supplied
to the serial-to-parallel converter 220, and the serial-to-parallel converter 220 separates the left
and right digital audio signals and each is parallel The 16-bit left and right digital audio signals
converted into data and converted into parallel data are supplied to the left and right speaker
devices 100L and 100R.
[0023]
In this example, the speaker devices 100L and 100R each include the decoder 70, the speaker
drive circuit 40, and the speaker unit 10, and each of the decoder 70 has 16 bits of digital audio
as parallel data from the serial to parallel converter 220. A control signal as described later is
generated from the signal, and the control signal is supplied to the speaker drive circuit 40, and
the speaker drive circuit 40 drives a primary coil described later of the speaker unit 10.
[0024]
FIG. 2 shows an example of the speaker unit 10.
In the speaker unit 10 of this example, a recess 13 is formed around the tip of the center pole 12
of the center pole yoke 11, and the primary coil 1 is attached to the center pole 12 by being
fitted into the recess 13. .
[0025]
The primary coil 1 is wound as an air core coil and attached to the recess 13 by press fitting and
attached to the center pole 12 or directly wound around the recess 13 to form the center pole
12. (Not shown), it is wound around a magnetic bobbin, and the magnetic bobbin is attached to
the center pole portion 12 by being press-bonded to the recess 13.
[0026]
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An opening (hole) 15 is formed in the flange portion 14 of the center pole / yoke 11 at a position
adjacent to the center pole portion 12 continuously, and a terminal plate 16 is attached to the
rear surface of the flange portion 14.
Then, a coil lead wire 17 made of, for example, a tinsel wire of the primary coil 1 is adhered to
the circumferential surface of the center pole portion 12 and inserted into the opening 15 and
connected to the input terminal 18 on the terminal plate 16 by soldering. Ru.
[0027]
The coil leader lines 17 are respectively provided at the winding start and the winding end of the
primary coil 1 and are respectively connected to separate input terminals.
Also, as described later, when the primary coil 1 is configured by a plurality of coils, the coil
leader 17 of each coil is bonded to the circumferential surface of the center pole portion 12 and
inserted into the opening 15 to form a terminal plate 16 is connected to the input terminal 18.
[0028]
The magnet 21 is adhered to the front surface of the flange portion 14 of the center pole yoke
11, and the plate 22 is adhered to the front surface of the magnet 21. The outer peripheral
surface of the tip of the center pole portion 12 and the inner periphery of the plate 22 A
magnetic circuit 20 is formed having an air gap 23 between it and the surface.
[0029]
In the air gap 23 of the magnetic circuit 20, the secondary coil 2 constituting a short coil is
inserted.
The secondary coil 2 is, in this example, a one-turn pipe or cylinder made of a nonmagnetic
conductive material such as aluminum.
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[0030]
The inner periphery of a cone 32 with an edge 31 on the outer periphery, the center cap 33, and
the inner periphery of a damper 34 are attached to the secondary coil 2.
Further, the speaker frame 35 is attached to the plate 22, the edge 31 of the outer periphery of
the cone 32 and the gasket 36 are attached to the speaker frame 35, and the outer periphery of
the damper 34 is attached to the speaker frame 35.
[0031]
As shown in FIG. 3, a portion of the coil 1 a of the primary coil 1 may be attached to the
circumferential surface of the tip of the center pole 12, and the remaining coil 1 b may be
attached to the inner circumferential surface of the plate 22.
In this case, although the coil leader line of the coil 1b attached to the plate 22 is omitted in the
figure, for example, a terminal inserted between the plate 22 and the magnet 21 and attached to
the outer peripheral surface of the plate 22 Connected to the input terminal on the board.
Further, as shown in FIG. 4, all the primary coils 1 may be attached to the inner peripheral
surface of the plate 22.
[0032]
By forming the secondary coil 2 by an aluminum pipe or the like for one turn as shown in FIG. 2,
FIG. 3 or FIG. 4, the bobbin around which the secondary coil 2 is wound can be omitted.
[0033]
Then, when the primary coil 1 is configured by a plurality of coils, the 16-bit digital audio signal
from the serial-to-parallel converter 220 of FIG. 1 is a 2's complement code as shown in FIG.
When it is quantized, the primary coil 1 is composed of 15 coils 1A, 1B,... 1N, 1P as shown in
FIGS. 5 and 6, with the MSB (most significant bit) as a sign bit. The coil 1A is made to correspond
to the LSB (least significant bit), for example, 2 turns, hereinafter, the coil 1B, 1C, 1D, 1E, 1F, 1G,
1H, 1I, 1J, 1K, 1L, 1M, 1N, 1P , Corresponding to 15SB, 14SB, 13SB, 12SB, 11SB, 10SB, 9SB, 8SB,
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7SB, 6SB, 5SB, 4SB, 3SB, 2SB, respectively. , 8 turn, 16-turn ... so on, and twice the number of
turns of the number of turns of the coil corresponding to a bit of the next lower.
[0034]
FIG. 7 shows an example of the portion of the decoder 70 and the speaker drive circuit 40 shown
in FIG. 1 in this case, and the speaker drive circuit 40 corresponds to the 15 coils 1A to 1N and
1P of the primary coil 1. There are fifteen coil drive circuits 40A to 40N and 40P.
[0035]
In each of the coil drive circuits 40A to 40N and 40P, constant current sources 41A to 41N and
41P, four FETs 51 to 54 as switching elements, and corresponding coils 1A to 1N and 1P are
bridge-connected. When the FETs 51 and 53 are turned on and the FETs 52 and 54 are turned
off, the current Ia of the corresponding constant current source flows in the corresponding coil in
the positive direction, the FETs 51 and 53 are turned off, and the FETs 52 and 54 are When it is
turned on, the current Ia of the corresponding constant current source is caused to flow in the
corresponding coil in the negative direction.
[0036]
The currents of the constant current sources 41A to 41N and 41P are all made equal as indicated
by the current Ia.
In the same coil drive circuit, when all the FETs 51 to 54 are turned on or off, no current flows in
the corresponding coil.
[0037]
The decoder 70 generates 15 control signals corresponding to the 15 coils 1A to 1N and 1P of
the primary coil 1, that is, 15 bits excluding the MSB of the digital audio signal from the serial-toparallel converter 220. Circuits 70A to 70N and 70P are provided, and control signal generation
circuits 70A to 70N and 70P output MSBs of digital audio signals from serial / parallel converter
220 and control signal generation circuits 70A to 70N and 70P, respectively. Four control signals
G1 to G4 as described later are respectively obtained from corresponding lower bits (LSB to 2SB),
and the control signals G1 to G4 correspond to corresponding coil drive circuits 40A to 40N of
the speaker drive circuit 40. , 40 P are supplied to the gates of the FETs 51 to 54.
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[0038]
The four control signals G1 to G4 are levels at which the control signals G1 and G3 turn on the
FETs 51 and 53 when the MSB of the digital audio signal from the serial to parallel converter
220 is 0 and the corresponding lower bit is 1. When the control signals G2 and G4 turn off the
FETs 52 and 54, when the MSB is 0 and the corresponding lower bit is 0 or the MSB is 1 and the
corresponding lower bit is 1, the control signals G1 to G4 are generated. Is a level to turn off the
FETs 51 to 54, and when the MSB is 1 and the corresponding lower bit is 0, the control signals
G1 and G3 turn off the FETs 51 and 53, and the control signals G2 and G4 enter the FETs 52 and
54. It will be the level to turn on.
[0039]
Therefore, when MSB is 0, current Ia flows in the positive direction to the corresponding primary
coil only when the lower bit is 1, and conversely, when MSB is 1, only when the lower bit is 0 The
current Ia flows in the negative direction to the corresponding primary coil.
[0040]
The driving force F of the vibration system of the electromagnetic coupling speaker is the
secondary current i induced in the secondary coil, the density B of the magnetic flux generated in
the air gap of the magnetic circuit, and the length of the secondary coil in the air gap of the
magnetic circuit Since the magnetic flux density B and the length L are constant expressed as F =
BLi as a product with L, the driving force F of the vibration system is proportional to the
secondary current i induced in the secondary coil Become.
The secondary current i induced in the secondary coil is proportional to the product of the signal
current flowing through the primary coil and the number of turns (impedance) of the primary
coil.
[0041]
Then, in the above-described example, the number of turns of each coil 1A to 1P of the primary
coil 1 is made the number of turns proportional to the weight of each bit excluding the MSB of
the digital audio signal from the serial to parallel converter 220, When current Ia flows as a
signal current in a certain primary coil, secondary coil 2 has a weight of a bit corresponding to
the primary coil in a direction corresponding to the value of the MSB of the digital audio signal
from serial / parallel converter 220. A secondary current of proportional current value is
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induced.
[0042]
Therefore, cone 32 with secondary coil 2 fixed is displaced in the direction according to the value
of the MSB of the digital audio signal from serial / parallel converter 220 by an amount
proportional to the weight of the bit corresponding to that primary coil. In the speaker unit 10,
sound is reproduced faithfully to the digital sound signal from the serial-to-parallel converter
220.
[0043]
In this case, the digital audio signal from serial-to-parallel converter 220 is digitized at a
sampling frequency of 44.1 kHz or 48 kHz, for example, and each coil 1A-1P of primary coil 1 is
a digital signal of the same sampling frequency. Since it is driven, the low frequency component
of the audio signal before being digitized also has a high frequency exceeding 20 kHz as the
signal current flowing to each of the coils 1A to 1P of the primary coil 1.
[0044]
Therefore, the speaker unit 10, which is an electromagnetic coupling speaker, enables
reproduction up to the low frequency range, and a full range speaker that reproduces from bass
to treble can be realized.
[0045]
Like a general speaker, the vibration system of the speaker unit 10 is hard to respond to high
frequencies, and in particular, hardly reproduces high frequency components exceeding 20 kHz.
Therefore, even if each coil 1A to 1P of the primary coil 1 is driven by a digital signal of sampling
frequency of 44.1 kHz or 48 kHz, the sampling frequency component is hardly reproduced.
Even if the sound is reproduced with a very small sound pressure, sounds over 20 kHz can
hardly be heard by the human ear, so no problems occur even when listening to music.
In addition, it is also easy to intentionally form a mechanical filter having a stop band of 20 kHz
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or more and incorporate it into the speaker unit 10.
[0046]
In addition, it is possible to realize a speaker apparatus with small distortion and a large
maximum output, which reproduces the audio directly by the digital audio signal without using
the D / A converter and the power amplifier.
[0047]
The audio reproduction system shown in FIG. 1 integrates, for example, the serial-to-parallel
converter 220 to the speaker drive circuit 40 and connects it to the digital audio output device
210 and connects the speaker unit 10 to this or serial parallel The converter 220 to the speaker
unit 10 can be integrated and configured to be connected to the digital audio output device 210.
[0048]
The switching elements of the coil drive circuits 40A to 40P are not limited to FETs, and other
elements operating at high speed can be used.
[0049]
A bit of the digital audio signal from the serial-to-parallel converter 220 may have a value in
which the signal current flows to the corresponding primary coil in a period of a plurality of
consecutive sampling cycles.
[0050]
That is, when the digital audio signal from serial-to-parallel converter 220 is a 2's compliment
code as shown in FIG. 5, MSB is in period Tp of a plurality of continuous sampling cycles as
shown in FIG. 0, for example, 2SB becomes 1, and MSB may be 1, and for example, LSB may be 0
in the same period Ta, and in such a case, current Ia flows in the positive direction to primary coil
1P in period Tp. The current flows continuously, and in the period Ta, the current Ia flows
continuously in the negative direction to the primary coil 1A.
[0051]
However, in this case, the apparent sampling frequency of the 2SB, LSB data decreases, and
becomes, for example, 1 kHz when the periods Tp, Ta span 1 ms.
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Therefore, the electromagnetic coupling force of the speaker unit 10 is reduced, and the optimal
drive of the speaker unit 10 is not performed.
[0052]
Therefore, in the decoder 70 shown in FIGS. 1 and 7, in the data of each bit except the MSB of
the digital audio signal from the serial-to-parallel converter 220, the signal current does not flow
to the corresponding primary coil every sampling period. The duration of the value is set.
[0053]
FIG. 9 shows an example of a non-driving period setting circuit therefor.
The non-drive period setting circuit 80 is provided for each bit in the decoder 70 except for the
MSB of the digital audio signal from the serial-to-parallel converter 220, but the illustrated one is
for one of those bits. is there.
[0054]
In the non-driving period setting circuit 80, a clock SCLK as shown in FIG. 10, which has a
frequency equal to the sampling frequency of the digital audio signal synchronized with the
digital audio signal from the serial-to-parallel converter 220, The clock DCLK as shown in the
figure delayed by a time shorter than the sampling period Ts of the digital audio signal is
supplied to the exclusive OR circuit 82, and the exclusive OR circuit 82 The signal EX as shown is
obtained, the signal EX and the clock SCLK are supplied to the NAND circuit 83, and the signal
NA as shown in the figure is obtained from the NAND circuit 83, and the signal NA The input
data Di of the input bit is supplied to the AND circuit 84, and the output data Do is output from
the AND circuit 84. It is.
[0055]
The input data Di is the original data when the MSB is 0, and the original data is inverted at the
input side of the non-driving period setting circuit 80 when the MSB is 1.
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Therefore, when the original 2SB and LSB data are as shown in FIG. 8 in relation to the MSB
value, the 2SB and LSB data are used as input data Di of non-driving period setting circuit 80. Are
as shown in FIG. 10 as data Di (2SB) and Di (LSB).
[0056]
Therefore, at this time, the data of 2SB is output data Do of non-driving period setting circuit 80
as shown by data Do (2SB) in FIG. 10, for each delay of delay circuit 81 for each sampling cycle
Ts. In the same manner, as the output data Do of the non-driving period setting circuit 80, the
sampling period Ts is shown as data Do (LSB) in FIG. In each case, a period which becomes 0 for
the delay time in the delay circuit 81 is set.
[0057]
Then, in the decoder 70 shown in FIGS. 1 and 7, the control signals G1 to G4 are generated from
the output data Do of the non-driving period setting circuit 80.
Therefore, control signals G1 to G4 are similarly set to a period of a value for which the signal
current does not flow to the corresponding primary coil for a shorter period of time for each
sampling cycle Ts.
[0058]
Therefore, regardless of the content of the digital audio signal from serial / parallel converter
220, the apparent sampling frequency of the data of each bit of the digital audio signal is
reduced, and the electromagnetic coupling force of speaker unit 10 is reduced. Therefore, the
speaker unit 10 is always driven optimally.
The shorter the value period during which the signal current does not flow is desirable, but it is
determined in relation to the characteristics of the element used.
[0059]
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The coil drive circuits 40A to 40P of the speaker drive circuit 40 can also be configured by
constant voltage sources.
FIG. 11 shows an example in that case, in which a control type constant voltage source 42, four
FETs 51 to 54 as switching elements, and a corresponding coil, that is, a coil 1A in the case of a
coil drive circuit 40A are shown. , Bridged and configured.
[0060]
When the FETs 51 and 53 are turned on and the FETs 52 and 54 are turned off, current flows in
the positive direction to the corresponding coil by the constant voltage source 42, and when the
FETs 51 and 53 are turned off and the FETs 52 and 54 are turned on. The constant voltage
source 42 causes current to flow in the corresponding coil in the negative direction.
[0061]
However, in the case of this constant voltage drive, since the number of turns of each coil 1A to
1P of the primary coil 1 is different, the output impedance of the constant voltage source 42 is
different for each of the coil drive circuits 40A to 40P. Even if the voltage value of the voltage
source 42 is constant, the values of the currents flowing through the respective coils 1A to 1P
are different.
Therefore, the gain of the constant voltage source 42 is adjusted by the adjustment resistor 43 so
that the values of the currents flowing to the respective coils 1A to 1P become equal.
[0062]
The coil drive circuits 40A to 40P can also be configured to control the constant current source
connected to the corresponding primary coil by ternary data from the decoder 70.
[0063]
FIG. 12 shows an example in that case, and from the decoder 70, data Xa to Xp of each bit
excluding the MSB of the digital audio signal from the serial to parallel converter 220 described
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above are obtained as ternary data, The data Xa to Xp are respectively supplied to the positive
input end of the constant current source 44 of the differential type, and the output end of the
constant current source 44 is a resistor 45, corresponding primary coils 1A to 1P, and a resistor
46. The voltage obtained at the connection point between the corresponding primary coils 1A to
1P and the resistor 46 is supplied to the negative input terminal of the constant current source
44.
The resistance value of the resistor 46 is, for example, 0.1 Ω.
[0064]
Data Xa to Xp are positive voltages when the MSB of the digital audio signal from serial / parallel
converter 220 is 0 and the corresponding lower bits (LSB to 2SB) are 1, the MSB is 0, and the
corresponding lower bits are When the bit is 0, or when the MSB is 1 and the corresponding
lower bit is also 1, the ground potential is obtained, and when the MSB is 1 and the
corresponding lower bit is 0, the negative voltage is obtained.
[0065]
Also in this case, as shown in FIG. 13, in data Xa to Xp, the period of the ground potential at
which the signal current does not flow to the corresponding primary coils 1A to 1P for a shorter
time is set for each sampling period Ts. Be done.
[0066]
In this example, when data Xa to Xp are positive voltages, a constant current flows in the positive
direction to the corresponding primary coils 1A to 1P, and when data Xa to Xp are the ground
potential, current to the corresponding primary coils 1A to 1P Does not flow, and when the data
Xa to Xp are negative voltages, a constant current flows in the negative direction to the
corresponding primary coils 1A to 1P.
[0067]
Therefore, as in the example of FIG. 7, when the MSB of the digital audio signal from serial-toparallel converter 220 is 0, signal current flows in the positive direction to the corresponding
primary coil only when a lower bit is 1 Conversely, when the MSB is 1, a signal current flows in
the negative direction to the corresponding primary coil only when a certain lower bit is 0.
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And according to this example, the coil drive circuits 40A to 40P can be simplified without
requiring switching elements such as the FETs 51 to 54.
[0068]
In the example described above, the number of turns of each of the coils 1A to 1P constituting
the primary coil 1 is set to the number of turns proportional to the weight of each bit excluding
the MSB of the digital audio signal from the serial to parallel converter 220. In the case of
reproducing the difference in weight of each bit of the digital audio signal, the number of turns of
each coil 1A to 1P is made the same, and the current of the constant current source 41A to 41P
of the corresponding coil drive circuit 40A to 40P. By changing the value, the difference in
weight of each bit of the digital audio signal from serial to parallel converter 220 can also be
reproduced.
[0069]
FIG. 14 shows an example in this case, and the 15 coils 1A to 1N and 1P constituting the primary
coil 1 are all made to have the same number of turns, for example 10 turns, and correspond to
the coils 1A to 1N and 1P. The currents Ia to In and Ip of the constant current sources 41A to
41N and 41P of the coil drive circuits 40A to 40N and 40P are changed as described later.
Others are the same as the example of FIG.
[0070]
As described above, the driving force F of the vibration system of the speaker unit 10 is
proportional to the secondary current i induced in the secondary coil 2, and the secondary
current i is the signal current flowing through the primary coil 1 and the primary coil It is
proportional to the product of one turn number (impedance).
[0071]
Therefore, in this example, although omitted in FIG. 14, the current Ib of the constant current
source of the coil drive circuit corresponding to the coil 1B corresponding to 15SB of the digital
audio signal from the serial to parallel converter 220 corresponds to the LSB. The current Ia of
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the constant current source 41A of the coil drive circuit 40A corresponding to the coil 1A is
doubled.
すなわち、Ib=2Iaとされる。
[0072]
Of the constant current source of the coil drive circuit corresponding to the coils 1C, 1D, 1E...
Corresponding to 14SB, 13SB, 12SB... Is twice as large as the currents Ib, Ic, Id. Ru.
[0073]
Therefore, as in the example of FIG. 7, in the speaker unit 10, the cone 32 is a bit corresponding
to the primary coil in which the signal current flows in the direction according to the value of the
MSB of the digital audio signal from the serial to parallel converter 220. The voice is reproduced
faithfully to the digital voice signal from the serial-to-parallel converter 220, offset by an amount
proportional to the weight.
[0074]
Furthermore, in the case where the difference in weight of each bit of the digital audio signal is
reproduced by changing the current value of the constant current source in this manner, the
primary coil 1 can be one.
[0075]
FIG. 15 shows an example in that case.
However, in this example, if the 16-bit digital audio signal from the serial-to-parallel converter
220 is a natural binary code, or if the digital audio signal of the 2's complement code as shown in
FIG. This is the case where the parallel converter 220 converts it into a natural binary code.
[0076]
In this example, the primary coil 1 is formed of one coil, and constant current sources 61A, 61B
to 61N of currents Ia, Ib to In, Ip, Iq as described later with respect to the primary coil 1
respectively. , 61P and 61Q are connected via switch circuits 62A, 62B to 62N, 62P and 62Q,
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respectively, and switch circuits 62A, 62B to 62N, 62P and 62Q correspond to digital audio
signals from serial to parallel converter 220. It is switched by bit data.
[0077]
That is, when a certain bit of the digital audio signal from serial / parallel converter 220 is 1, the
corresponding switch circuit is turned on, and the current of the corresponding constant current
source flows through primary coil 1.
The current Ib of the constant current source 61B corresponding to 15SB is twice as high as the
current Ia of the constant current source 61A corresponding to the LSB, and the current of the
constant current source corresponding to each bit is The current of the constant current source
corresponding to the bit is doubled.
[0078]
Therefore, in this example, in the speaker unit 10, the cone 32 is displaced in one direction by an
amount proportional to the weight of each bit of the digital audio signal from the serial to
parallel converter 220. Audio is reproduced faithfully to the digital audio signal.
[0079]
Even if the digital audio signal from serial-to-parallel converter 220 is a 2's complement code as
shown in FIG. 5, coil drive circuits 40A to 40P as shown in FIG. The primary coil 1 can be made
one by making it switch by data of each bit except MSB of an audio | voice signal.
[0080]
Furthermore, by combining the difference in the number of turns of the plurality of primary coils
with the difference in the current values of the plurality of constant current sources, it is possible
to reproduce the difference in weight of each bit of the digital audio signal.
[0081]
FIG. 16 shows an example in that case.
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However, also in this example, when the 16-bit digital audio signal from the serial-to-parallel
converter 220 is a natural binary code, or the digital audio signal of the 2's complement code as
shown in FIG. This is the case where the parallel converter 220 converts it into a natural binary
code.
[0082]
In this example, the primary coil 1 is composed of four coils 1S, 1T, 1U, 1V with a turn ratio as
described later, and constant current sources of currents Ia to Id as described later for the coil
1S. 61A to 61D are respectively connected via switch circuits 62A to 62D, and constant current
sources 61E to 61H of currents Ie to Ih as described later are respectively connected to coil 1T
via switch circuits 62E to 62H. The constant current sources 61I to 61L of the currents Ii to Il as
described later are connected to the coil 1U respectively via the switch circuits 62I to 62L, and
the coil 1V is described later on The constant current sources 61M, 61N, 61P, 61Q of the
currents Im, In, Ip, Iq are switch circuits 62M, 62N, 62P, 62 respectively. Is connected via a
switch circuit 62A, 62B~62N, 62P, 62Q is switched by the corresponding bit data of the digital
audio signal from the serial-parallel converter 220.
[0083]
For example, the turn number ratio of the coils 1S, 1T, 1U, 1V is 1: 4: 16: 64, and the currents IaIn, Ip, Iq of the constant current sources 61A-61N, 61P, 61Q are Ib = 2Ia. , Ic = 22Ia, Id = 23Ia, Ie
= Ic = 22Ia, If = Id = 23Ia, Ig = 24Ia, Ih = 25Ia, Ii = Ig = 24Ia, Ij = Ih = 25Ia, Ik = 26Ia, Il = 27Ia, Im
= Ik = 26 Ia, In = Il = 27 Ia, Ip = 28 Ia, Iq = 29 Ia.
[0084]
As described above, the driving force F of the vibration system of the speaker unit 10 is
proportional to the secondary current i induced in the secondary coil 2, and the secondary
current i is the signal current flowing through the primary coil 1 and the primary coil It is
proportional to the product of one turn number (impedance).
[0085]
Therefore, in this example, when a certain bit of the digital audio signal from serial / parallel
converter 220 becomes 1, the corresponding ones of switch circuits 62A to 62N, 62P, 62Q are
turned on, and primary coil 1S, With the signal current flowing to 1 T, 1 U or 1 V, the ratio of the
secondary current induced in the secondary coil 2 becomes equal to the ratio of the weight of
each bit of the digital audio signal from the serial-to-parallel converter 220.
10-04-2019
20
[0086]
Therefore, as in the example of FIG. 15, in the speaker unit 10, the cone 32 is displaced in one
direction by an amount proportional to the weight of each bit of the digital audio signal from the
serial to parallel converter 220 The audio is reproduced faithfully to the digital audio signal from
unit 220.
[0087]
And in this example, the ratio of the number of turns between the coil 1S of the minimum
number of turns and the coil 1V of the maximum number of turns can be reduced to 1: 64 = 1:
26 and the minimum The ratio of the current value between the current value Ia and the
maximum current value Iq can be reduced to 1:29.
[0088]
In each of the above-described examples, the digital audio signal for driving the primary coil 1 of
the speaker unit 10 is linearly quantized, and the number of turns of the plurality of coils when
the primary coil 1 is formed of a plurality of coils Digital voice signal that drives primary coil 1,
although the current value of the constant current source corresponding to each bit excluding
MSB or each bit including MSB of digital audio signal can be changed in a geometric progression
When the primary coil 1 is composed of a plurality of coils, the number of turns of the plurality
of coils, or the digital audio signal of The current value of the constant current source
corresponding to each bit excluding the MSB or each bit including the MSB may be changed.
[0089]
FIG. 17 shows another example of an audio reproduction system using the speaker device of the
present invention, wherein an analog audio signal from an analog audio output device is
converted into a digital audio signal, and the digital audio signal is further processed to obtain
audio. Is played back.
[0090]
The analog audio output device 310 is a cassette player or an FM tuner, and left and right analog
audio signals are output from the left and right audio output terminals 311L and 311R, and the
left and right analog audio signals are output from the A / D converter 320L, Each digital signal
is converted into a 16-bit digital audio signal by 320R.
[0091]
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21
The left and right digital audio signals from the A / D converters 320L and 320R are supplied to
an effector 330 using a DSP (digital signal processor) or the like, and localization of a sound
image, formation of a sound field, reverberation sound in the effector 330 Are processed, and 16bit digital audio signals are respectively obtained from the effector 330, and digital audio signals
of the front, rear, left, and right are respectively supplied to the speaker devices.
[0092]
Each of the speaker devices includes decoders 70FL, 70FR, 70BL, 70BR, speaker drive circuits
40FL, 40FR, 40BL, 40BR, and speaker units 10FL, 10FR, 10BL, 10BR, and the decoders 70FL,
70FR, 70BL, 70BR The speaker drive circuits 40FL, 40FR, 40BL, and 40BR are each configured
as the above-described speaker drive circuit 40, and the speaker units 10FL, 10FR, 10BL, and
10BR are each described above. It is configured as a speaker unit 10.
[0093]
According to the audio reproduction system of this example, for example, the A / D converters
320L and 320R to the speaker drive circuits 40FL, 40FR, 40BL and 40BR are integrated and
connected to the analog audio output device 310, and By connecting the speaker units 10FL,
10FR, 10BL and 10BR to one another, or integrating the A / D converters 320L and 320R to the
speaker units 10FL, 10FR, 10BL and 10BR and connecting them to the analog audio output
device 310 By doing this, it is possible to convert the input analog audio signal into a digital
audio signal, process the digital audio signal, and reproduce the audio.
[0094]
Also in the audio reproduction system shown in FIG. 1, the digital audio signal from the serial-toparallel converter 220 can be similarly processed, and the processed digital audio signal can be
supplied to the speaker device.
[0095]
FIG. 18 shows still another example of the audio reproduction system using the speaker device of
the present invention, in which the audio data is separated from the data from the data output
device and the audio is reproduced.
[0096]
The data output device 410 is a personal computer or the like, from which data in which data of
digital audio signals and other data are integrated in a predetermined format is output as serial
data.
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[0097]
Then, the data from the data output device 410 is supplied to the USB decoder 420, and only the
data of the digital audio signal is output as parallel data from the USB decoder 420, and the
digital audio signal is output from the decoder 70 and the speaker drive circuit. 40 and the
speaker unit 10 are supplied to the decoder 70 of the above-described speaker apparatus.
[0098]
According to the audio reproduction system of this example, for example, the USB decoder 420
to the speaker drive circuit 40 are integrated and connected to the data output device 410 and
the speaker unit 10 is connected thereto, or USB By integrating the decoder 420 to the speaker
unit 10 and connecting this to the data output device 410, it is possible to reproduce voice by
audio data present in integrated data from a personal computer or the like.
[0099]
FIG. 19 shows an audio reproduction system using another example of the speaker apparatus of
the present invention.
In this example, an analog audio signal Ao from an analog audio output device 510 such as a
cassette player or an FM tuner is supplied to a chopper 520, and as shown by an analog audio
signal Ac in FIG. It is chopped at a high frequency, that is, a frequency fc above 20 kHz, which is
said to be the upper limit of the audio frequency.
[0100]
However, it is desirable that the chopping frequency fc be a high frequency around twice 20 kHz,
for example, 40 kHz.
Further, the time width of the chopping period is sufficiently shorter than the chopping period
Tc, and is set to, for example, 1/10 of the chopping period Tc.
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23
[0101]
Then, the chopped analog audio signal Ac from the chopper 520 is amplified by the power
amplifier 530 and supplied to the primary coil 1 of the speaker unit 10 described above.
However, the speaker unit 10 has one primary coil 1.
[0102]
As described above, the speaker unit 10 which is an electromagnetic coupling speaker has an
electromagnetic coupling force in which the secondary current i is induced in the secondary coil
2 by the signal current flowing through the primary coil 1 in a low frequency range of several
kHz to 1 kHz or less It becomes smaller.
[0103]
However, according to the example of FIG. 19, since the analog audio signal is interrupted at a
frequency fc higher than the audio frequency and supplied to the primary coil 1 of the speaker
unit 10, the low frequency component of the analog audio signal is also the primary coil. The
signal current flowing to 1 has a high frequency exceeding 20 kHz.
Therefore, the reproduction to the low frequency is possible by the speaker unit 10 which is an
electromagnetic coupling speaker.
[0104]
Also in the audio reproduction system of this example, for example, the chopper 520 and the
power amplifier 530 are integrated and connected to the analog audio output device 510, and
the speaker unit 10 is connected to this, or the chopper 520 to the speaker The unit 10 can be
integrated and configured to be connected to the analog audio output device 510.
[0105]
As described above, according to the present invention, the analog voice signal supplied to the
primary coil of the electromagnetic coupling speaker is driven by the audio frequency by driving
the primary coil of the electromagnetic coupling speaker with the digital audio signal.
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Intermittent operation at a high frequency makes it possible to reproduce low frequencies by
means of electromagnetically coupled speakers, and realize a full range speaker that reproduces
from low to high tones.
[0106]
Furthermore, a low-distortion, high-power speaker system can be realized that reproduces audio
directly from digital audio signals without using a D / A converter and a power amplifier.
[0107]
Brief description of the drawings
[0108]
1 is a block diagram showing an example of an audio reproduction system using the speaker
device of the present invention.
[0109]
2 is a cross-sectional view showing an example of a speaker unit.
[0110]
3 is a cross-sectional view showing another example of the speaker unit.
[0111]
4 is a cross-sectional view showing still another example of the speaker unit.
[0112]
5 is a diagram for explaining an example of a digital audio signal.
[0113]
6 is a diagram showing an example of the coil configuration of the speaker unit.
[0114]
7 is a connection diagram showing an example of a speaker apparatus of the present invention.
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25
[0115]
8 is a diagram for explaining the aspect of the data of each bit of the digital audio signal.
[0116]
9 is a diagram showing an example of a non-driving period setting circuit.
[0117]
10 is a diagram for explaining the non-driving period setting circuit of FIG.
[0118]
11 is a connection diagram showing an example of a coil drive circuit using a constant voltage
source.
[0119]
12 is a connection diagram showing another example of the coil drive circuit.
[0120]
13 is a diagram for explaining the coil drive circuit of FIG.
[0121]
14 is a connection diagram showing another example of the speaker device of the present
invention.
[0122]
FIG. 15 is a connection diagram showing still another example of the speaker device of the
present invention.
[0123]
16 is a connection diagram showing still another example of the speaker device of the present
invention.
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26
[0124]
<Figure 17> It is the block diagram which shows the other example of the sound playback system
which uses the speaker device of this invention.
[0125]
FIG. 18 is a block diagram showing still another example of an audio reproduction system using
the speaker device of the present invention.
[0126]
19 is a block diagram showing an audio reproduction system using another example of the
speaker device of the present invention.
[0127]
20 is a diagram for explaining the speaker apparatus of FIG.
[0128]
Explanation of sign
[0129]
10: Speaker unit 1, 1a, 1b, 1A, 1B, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1P, 1Q, 1S, 1T, 1U,
1V ... Primary coil, 2 ... Secondary coil, 20 ... Magnetic circuit, 23 ... Air gap, 32 ... Cone, 40 ...
Speaker drive circuit, 40A-40P ... Coil drive circuit, 41A-41P, 44, 61A-61Q ... Constant current
source 42: constant voltage source, 51 to 54: FET, 62A to 62Q: switch circuit, 70: decoder, 80:
non-drive period setting circuit, 210: digital audio output device, 220: serial parallel converter,
310, 510: Analog voice output device, 320L, 320R ... A / D converter, 330 ... effector, 410 ... data
output device, 420 ... USB decoder, 520 ... chopper
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