JP2009246659

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DESCRIPTION JP2009246659
An object of the present invention is to set an appropriate vibration width according to the
amplitude of a drive signal flowing through a conductor line of a movable plate, regardless of
which direction the movable plate vibrates. A flat type speaker according to the present invention
has first to third flat plates 2a, 2b and 2c on which conductor lines 4a, 4b and 4c having
meander lines of the same pattern are respectively formed. The face plates 2a, 2b, 2c are
arranged in parallel at a predetermined interval so that the opposing conductor lines 4a, 4b, 4c
are directly opposed. The second flat plate 4b is a movable plate displaceable in the direction
orthogonal to the plate surface, and the first and second flat plates 4a and 4c are fixed plates
fixed undisplaceably in the direction orthogonal to the plate surface. is there. Two driving
currents flowing in the conductor lines 4a and 4c of the two fixed plates 4a and 4c with respect
to the conductor line 4b of the movable plate by supplying a drive current of a predetermined
direction based on the audio signal to the conductor line of each plane plate The current causes
attraction and repulsion, and these combined forces cause the movable plate to vibrate. [Selected
figure] Figure 1
Flat-type speaker, audio amplifier and speaker system for driving the same
[0001]
The present invention relates to a flat loudspeaker, an audio amplifier for driving the flat
loudspeaker, and a loudspeaker system including the flat loudspeaker and the audio amplifier.
[0002]
Conventionally, a speaker as an audio device has, for example, a substantially conical diaphragm,
and the diaphragm is vibrated by supplying a drive current to a voice coil provided on the
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movable plate, and so-called cone is output. There is a type speaker.
[0003]
As an audio amplifier for driving this cone type speaker, for example, a switching amplifier which
pulse-width modulates the original audio signal is known.
In this switching amplifier, switching elements such as a MOS-FET are alternately turned on and
off by a modulation signal obtained by modulating an audio signal and an inverted modulation
signal obtained by inverting the modulation signal, and harmonic components are removed by a
low pass filter. Drive current is supplied to the cone type speaker.
[0004]
On the other hand, in recent years, according to the amplitude of the audio signal to the
conductor line, for example, a drive current based on the audio signal is supplied to the
conductor lines formed on the pair of plane plates, provided with a pair of plane plates arranged
facing each other. There has been proposed a flat type speaker which generates an
electromagnetic force and thereby vibrates one of a pair of flat plates to output sound (see, for
example, Patent Document 1).
[0005]
Patent No. 3349647 gazette
[0006]
Further, the applicant of the present application has proposed a speaker system including the
above-mentioned flat type speaker and a switching amplifier for driving the same in Japanese
Patent Application No. 2006-284478.
FIG. 12 and FIG. 13 are diagrams showing a schematic structural view of a planar speaker and
pulse signals (control pulse signal and drive pulse signal) for driving the planar speaker.
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[0007]
According to these figures, the planar speaker has, for example, a pair of flat plates 31a and 31b
on which the conductor lines 32a and 32b are respectively formed, and the conductor lines 32a
and 32b have a high level and a low level at constant intervals. By supplying a control pulse
signal that repeats alternately and a drive pulse signal whose duty ratio changes according to the
amplitude of the audio signal, an attractive force and a repulsive force are generated between the
pair of flat plates 31a and 31b.
[0008]
FIG. 12 is a diagram showing the case where an attractive force is generated between the pair of
flat plates 31a and 31b, but when the control pulse signal and the drive pulse signal are at the
same level as each other (see shaded area) The directions of the current flowing through the
conductor line 32a 31a and the current flowing through the conductor line 32b of the other flat
plate 31b are the same, and an attractive force is generated between the pair of flat plates 31a
and 31b.
[0009]
On the other hand, FIG. 13 is a diagram showing the case where a repulsive force is generated
between the pair of flat plates 31a and 31b, but when the control pulse signal and the drive
pulse signal are at different levels (see shaded area) The directions of the current flowing
through the conductor line 32a of the face plate 31a and the current flowing through the
conductor line 32b of the other flat plate 31b are opposite to each other, and a repulsive force is
generated between the pair of flat plates 31a and 31b.
Therefore, in the planar speaker, by attracting and repulsive force generated between the pair of
flat plates 31a and 31b, either one of the pair of flat plates 31a and 31b is vibrated with an
amplitude according to the amplitude of the audio signal ( In FIG. 12 and FIG. 13, the flat plate
31a is used as a movable plate to vibrate, and the flat plate 31b is used as a fixed plate not to
vibrate) and the audio signal is converted into voice and output.
[0010]
As described above, the planar speaker generates an audio signal by utilizing an attraction or
repulsion based on Fleming's left-hand rule in both conductor lines when current flows in a pair
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of parallel conductor lines. It is converted to).
As well known, when currents I1 and I2 respectively flow in a pair of parallel conductor lines, r
between the conductor lines is r, and magnetic permeability at the arrangement position of the
conductor lines is μ, the force F acting on each conductor line is It is expressed by F = μI1 · I2 /
(2πr), and changes according to the distance r between the conductor lines.
[0011]
Therefore, when an attractive force is generated between the movable plate 31a and the fixed
plate 31b of the flat panel speaker, the movable plate 31a approaches the fixed plate 31b and
the distance r becomes smaller. Therefore, the attractive force acting on the movable plate 31a
Increases as the movable plate 31a approaches the fixed plate 31b.
On the other hand, when a repulsive force is generated between the movable plate 31a and the
fixed plate 31b of the planar speaker, the movable plate 31a is moved away from the fixed plate
31b and the distance r is increased. Therefore, the repulsive force acting on the movable plate
31a is It decreases as the movable plate 31a moves away from the fixed plate 31b.
Therefore, even if the magnitude of the current flowing through the conductor line 32a of the
movable plate 31a is the same, the movable plate 31a is different between when the movable
plate 31a approaches the fixed plate 31b and when the movable plate 31a moves away from the
fixed plate 31b. The vibrating width will be different.
[0012]
That is, as shown in FIG. 14, when an attractive force is generated between the movable plate
31a and the fixed plate 31b corresponds to, for example, a drive signal of a sine wave shown in
FIG. The desired vibration width of the movable plate 31a is the waveform W0 having the
maximum amplitude S (see FIG. 14B), but in actuality, it is the vibration width as shown in the
waveform W1 exceeding the maximum amplitude S.
[0013]
On the other hand, if a case where a repulsive force is generated between the movable plate 31a
and the fixed plate 31b causes a sinusoidal drive signal shown in FIG. 14A to be negative, for
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example, the desired movable plate 31a corresponding to the drive signal The vibration width is
the waveform W0 having the maximum amplitude S (see FIG. 14B), but in actuality, it is the
vibration width as shown in the waveform W2 below the maximum amplitude S.
[0014]
Essentially, if the current flowing through the conductor line 32a of the movable plate 31a is the
same, it is desirable that the attractive force and the repulsive force acting on the movable plate
31a be the same. However, as described above, the conventional flat type speaker has a pair of
Since one of the flat plates is the movable plate and the other is the fixed plate, the movable plate
31a is based on the driving principle of the movable plate based on Fleming's left hand rule, even
if the current flowing in the conductor line 32a of the movable plate 31a is the same. The
attraction and repulsion acting on can not be the same.
For this reason, the movable plate 31a can not be vibrated accurately according to the amplitude
of the audio signal, and there is a problem that the sound according to the positive and negative
amplitudes of the audio signal can not be output properly.
[0015]
Further, in the conventional flat type speaker, since one flat plate 31a of the pair of flat plates
31a and 31b is a movable plate and the other flat plate 31b is a fixed plate, among the sound
waves generated by the vibration of the movable plate 31a The sound wave propagating in the
direction of the fixing plate 31b is blocked by the fixing plate 31b, and only the sound wave
propagating in the direction opposite to the direction of the fixing plate 31b is emitted to the free
space.
That is, the conventional flat loudspeaker has a structure in which the radiation direction of the
sound wave is in the direction in which the fixed plate 31b is not present among the two
directions orthogonal to the plate surface of the movable plate 31a. In this structure, of the front
and back surfaces of the movable plate 31a, the surface opposed to the fixed plate 31b can be
protected by the fixed plate 31b, but the surface not opposed to the fixed plate 31b is exposed.
Similar to the baffle plate, the movable plate 31a is vulnerable to external impact, and it is
necessary to provide some kind of protective member.
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[0016]
The present invention has been conceived under the above-mentioned circumstances, and an
object of the present invention is to provide a planar speaker capable of generating an
appropriate vibration according to a drive signal. Another object of the present invention is to
provide an audio amplifier capable of driving this flat speaker.
[0017]
In order to solve the above problems, the present invention takes the following technical
measures.
[0018]
The flat loudspeaker provided by the first aspect of the present invention has a plurality of flat
plates on which conductor traces of the same pattern are formed, and the conductor traces
formed on flat plates adjacent to each other The voice signals are disposed parallel to each other
at a predetermined distance so that they face each other, and a drive current based on voice
signals is supplied to the conductor lines of the flat plates to vibrate one flat plate of the plurality
of flat plates. A flat type speaker for converting sound into sound and outputting, wherein the
plurality of flat plates are disposed so as to sandwich the movable plate and one movable plate
displaceable in a direction orthogonal to the plate surface, It is characterized in that it comprises
two fixed plates fixed non-displaceably in the direction orthogonal to the surface, and at least one
of the two fixed plates is provided with an opening (claim 1). .
[0019]
According to this configuration, the two fixed plates at predetermined intervals with respect to
the front and back surfaces of the movable plate align the conductor lines formed on the
respective fixed plates with the conductor lines formed on the movable plate. It is arranged
opposite to.
Therefore, a conductor line formed on each of two fixing plates (hereinafter, referred to as "fixed
plate side conductor line").
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Current flowing in opposite directions to each other, and the conductor line formed on the
diaphragm (hereinafter referred to as "the movable plate side conductor line"). If current flows in
the same direction as one fixed plate conductor line, the movable plate conductor line generates
an attractive force with one fixed plate conductor line and the other fixed plate conductor line
Repulsion occurs between them. Therefore, a combined force (combined force of attractive force
and repulsive force) acting in the direction of one fixed plate side conductor line acts on the
movable plate side conductor line. Conversely, when current flows in the movable plate
conductor line in the same direction as the other fixed plate conductor line, an attractive force is
generated in the movable plate conductor line with the other fixed plate conductor line, Repulsive
force is generated between the fixed plate side conductor line. Therefore, a combined force
(combined force of attractive force and repulsive force) acting in the direction of the other fixed
plate side conductor line acts on the movable plate side conductor line.
[0020]
The movable plate on which the movable plate side conductor line is formed is moved by the
combined force acting on the movable plate side conductor line, and the distance between the
movable plate side conductor line and one fixed plate side conductor line and the movable plate
side conductor Although the distance between the line and the other fixed plate conductor line
changes, the attractive force and the repulsive force, which are components of the combined
force, change respectively, but the two fixed plate conductor lines are centered on the movable
plate conductor line Because they are disposed at symmetrical positions, the amount of change in
the resultant force based on the amount of movement of the movable plate is substantially the
same regardless of the direction of the current flowing through the movable plate conductor line.
Therefore, even when the movable plate is vibrated based on the drive signal (AC current)
supplied to the movable plate side conductor line, the symmetry of the positive and negative
vibration widths of the movable plate can be maintained, and the appropriate vibration according
to the drive signal Can occur.
[0021]
In the flat loudspeaker according to the present invention, the conductor lines formed on the
plurality of plane plates are made of meander lines, and the openings provided on the fixing plate
are formed in the gaps between the lines of the meander lines. It is good to have (claim 2).
[0022]
Further, the fixed plate may be configured by a hard member to protect the movable plate (claim
3).
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[0023]
According to a second aspect of the present invention, an audio amplifier includes a conductor
line formed on a movable plate of the flat type speaker according to any one of claims 1 to 3 and
2 formed on two fixed plates. An audio amplifier for supplying a drive current based on an audio
signal to a conductor line of a book, the first power source, a second power source having a
polarity different from that of the first power source, and an audio signal generating the audio
signal Generating means, clock generating means for generating a reference clock, pulse width
modulating means for generating a modulation signal by pulse width modulating the audio signal
based on the reference clock, and dividing the reference clock to obtain the reference Clock
dividing means for generating a first pulse signal having a frequency lower than that of a clock;
and a second one having a frequency lower than that of the modulation signal by dividing the
modulation signal. Modulation signal dividing means for generating a pulse signal, phase
inverting means for generating a third pulse signal by inverting the phase of the first pulse
signal, and the level change of the second pulse signal. First current supply control means for
switching connection of the first power supply and the second power supply to a conductor line
formed on the movable plate and controlling a drive current supplied to the conductor line;
Switching the connection of the first power source and the second power source to the conductor
line formed on one of the fixed plates according to the change in the level of the pulse signal of
1, and driving current supplied to the conductor line Connection to a conductor line formed on
the other of the fixed plate of the first power supply and the second power supply according to
the second current supply control means to control and the change of the level of the third pulse
signal And the drive supplied to the conductor line It is characterized in that it comprises a third
current supply control means for controlling the flow, the (claim 4).
[0024]
In the audio amplifier of the present invention, the third current supply control means is a drive
current in the same direction as the drive current to the movable plate supplied by the second
current supply control means by the first current supply control means. While supplying a drive
current in a direction opposite to the drive current to the movable plate to the other fixed plate
when the second fixed plate is supplying the drive current to the movable plate. When a drive
current in the opposite direction to that in the above is supplied to the one fixed plate, a drive
current in the same direction as the drive current for the movable plate may be supplied to the
other fixed plate (claim 5).
[0025]
A speaker system provided by a third aspect of the present invention is characterized by
comprising the flat type speaker according to any one of claims 1 to 3 and the audio amplifier
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according to claim 5. Claim 6).
[0026]
Other features and advantages of the present invention will become more apparent from the
detailed description given below with reference to the accompanying drawings.
[0027]
Hereinafter, preferred embodiments of the present invention will be specifically described with
reference to the attached drawings.
[0028]
FIG. 1 is a schematic configuration view of a flat loudspeaker according to the present invention,
and FIG. 2 is a schematic perspective view of the flat loudspeaker.
[0029]
The flat speaker 1 is, as shown in FIG. 1, three horizontal oblong rectangles in which first to third
flat plates 2a, 2b and 2c of the same size are arranged at a predetermined interval, and The
second flat plates 2a and 2b face each other, and the second and third flat plates 2b and 2c face
each other.
In FIG. 1, the intervals of the first to third flat plates 2 a, 2 b and 2 c are enlarged for easy
understanding.
The first and third flat plates 2a and 2c, as shown in FIG. 2, are flat plates having a
predetermined thickness, but are illustrated as plane in FIG. 1 for convenience of explanation.
[0030]
The first and third flat plates 2a and 2c are fixed plates that do not vibrate, while the second flat
plate 2b is a movable plate that vibrates.
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That is, the flat plate speaker 1 is configured to sandwich the second flat plate 2b, which is a
movable plate, with the first and third flat plates 2a and 2c, which are fixed plates.
The second flat plate 2b, which is a movable plate, vibrates in a direction substantially
perpendicular to the surface thereof.
[0031]
The first and third flat plates 2a and 2c are made of, for example, a relatively hard insulator such
as a resin, thereby protecting the second flat plate 2b from external impact and the like.
The second flat plate 2 b is made of, for example, ceramic (zirconia, silicon nitride, silicon
carbide, alumina or the like), and the thickness thereof is about 1 to 30 μm.
[0032]
Between the 1st plane board 2a and the 2nd plane board 2b, as shown in Drawing 2, the 1st
spacer 3a distributed as a frame along those circumferences is provided.
Further, also between the second flat plate 2b and the third flat plate 2c, there is provided a
second spacer 3b arranged as a frame along the peripheries thereof.
[0033]
On the surfaces of the first to third flat plates 2a, 2b and 2c, meander line type conductor lines
4a, 4b and 4c are respectively formed.
One end of the conductor line 4a is connected to, for example, the positive electrode terminal (+)
of a pair of terminals provided at one end of the first flat plate 2a in the longitudinal direction,
and the other end of the conductor line 4a is the first plane plate 2a The other end portion in the
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longitudinal direction returns from the other end portion to one end portion and is connected to
the negative electrode terminal (-) provided in the vicinity of the positive terminal.
The configuration of the conductor lines 4b and 4c of the second and third flat plates 2b and 2c
is the same as the configuration of the conductor line 4a of the first flat plate 2a.
[0034]
The conductor lines 4a, 4b and 4c formed on the first to third flat plates 2a, 2b and 2c are
arranged such that the conductor lines 4a and 4b and the conductor lines 4b and 4c face each
other. The conductor lines 4a, 4b, 4c are made of, for example, copper, aluminum or the like, and
are formed by attaching a conductor to the first to third flat plates 2a, 2b, 2c. The conductor lines
4a, 4b, 4c may be formed by etching or the like. The conductor line 4b is more preferably light in
weight so as not to inhibit the vibration of the second flat plate 2b.
[0035]
The first flat plate 2a is formed with a plurality of horizontally extending openings 5 in the area
excluding the area where the conductor line 4a is formed. The openings 5 are formed in the gaps
formed in the adjacent lines by folding the conductor lines 4a, and a total of five openings 5 are
formed according to FIG. In addition, the opening 5 similar to the 1st plane board 2a is formed
also in the 3rd plane board 2c. By forming these openings 5, when vibration occurs in the second
flat plate 2b, the vibration (sound wave) of air propagating to both the first flat plate 2a and the
third flat plate 2c caused by the vibration is generated. It is radiated to the outside through the
opening 5. That is, the flat loudspeaker according to the present embodiment has directivity in a
direction perpendicular to both surfaces of the first flat plate 2a and the third flat plate 2c.
[0036]
The amplifier device 10 is connected to the flat type speaker 1, and a drive current output from
the amplifier device 10 flows through each of the conductor lines 4a, 4b and 4c. The driving
current has a direction of flowing from the positive electrode terminal (+) to the negative
electrode terminal (−) shown in FIG. 1 and a direction of flowing from the negative electrode
terminal (−) to the positive electrode terminal (+).
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[0037]
As shown in FIG. 3, when drive current flows in the directions opposite to each other as shown in
FIG. 3, the conductor lines 4a and 4b of the first and second flat plates 2a and 2b, as shown in
FIG. 3 and FIG. Repulsive forces F1 and F2 due to Lorentz force act between the lines 4a and 4b.
More specifically, when the drive current I1 flowing through the conductor line 4a of the first flat
plate 2a and the drive current I2 flowing through the conductor line 4b of the second flat plate
2b are in opposite directions, the first flat plate 2a (fixed Magnetic force lines E2 are generated
counterclockwise around the conductor line 4a of the plate by the drive current I2 flowing
through the conductor line 4b of the second flat plate 2b (movable plate). Therefore, an upward
electromagnetic force (repulsive force) F1 in FIG. 3 is generated in the conductor line 4a of the
first flat plate 2a by the drive current I1 and the magnetic force line E2.
[0038]
In addition, around the conductor line 4b of the second flat plate 2b (movable plate), a magnetic
force line E1 is generated clockwise by the drive current I1 flowing through the conductor line
4a of the first flat plate 2a (fixed plate). Therefore, a downward electromagnetic force F2
(repulsive force) in FIG. 3 is generated in the conductor line 4b of the second flat plate 2b
(movable plate) by the drive current I2 and the magnetic line of force E1. The repulsive force F2
is represented by F2 = μI1 · I2 / (2πr), where r is the distance between the conductor line 4a
and the conductor line 4b and μ is the permeability at the position where the conductor line 4b
is disposed.
[0039]
On the other hand, as shown in FIG. 5, when drive currents flow in the same direction, as shown
in FIG. 5 and FIG. 6, attractive forces by Lorentz forces F1 'and F2' act between the conductor
lines 4a and 4b. That is, when the driving current I1 flowing through the conductor line 4a of the
first flat plate 2a and the driving current I2 flowing through the conductor line 4b of the second
flat plate 2b are in the same direction, the first flat plate 2a (fixed plate) In the conductor line 4a,
a downward electromagnetic force (attractive force) F1 'in FIG. 5 is generated by the drive
current I1 and the magnetic force line E2. Further, in the conductor line 4b of the second flat
plate 2b (movable plate), an upward electromagnetic force (attractive force) F2 'in FIG. 5 is
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generated by the drive current I2 and the magnetic force line E1. The attractive force F2 'is
represented by F2' = μI1 · I2 / (2πr).
[0040]
The relationship between the direction of the drive current in each of the conductor lines 4a and
4b of the first and second flat plates 2a and 2b and the resulting electromagnetic force is the
same as that in each of the conductor lines 4b and 4c of the second and third flat plates 2b and
2c. The relationship is the same as the direction of the drive current and the resulting
electromagnetic force.
[0041]
For example, drive currents I1 and I2 in the directions shown in FIG. 4 are respectively supplied
to the conductor line 4a of the first flat plate 2a (fixed plate) and the conductor line 4b of the
second flat plate 2b (movable plate). When a drive current -I2 in the opposite direction to the
conductor line 4a of the first flat plate 2a (fixed plate) flows through the conductor line 4c of 2c
(fixed plate), the conductor line 4b of the second flat plate 2b The combined force F of the
repulsive force based on the drive current I1 flowing through the conductor line 4a of the first
flat plate 2a and the attractive force based on the drive current -I2 flowing through the
conductor line 4c of the third flat plate 2a acts.
The resultant force F acts on the second flat plate 2b in the direction of moving away from the
first flat plate 2a, so this direction is a positive direction, and the distance between the second flat
plate 2b and the first flat plate 2a Let r1 be the distance between the second flat plate 2b and the
third flat plate 2c be r2, the repulsive force based on the drive current I1 is expressed by μI1 · I2
/ (2πr1), and the attractive force based on the drive current −I2 is Since it is represented by
μI1 · (−I2) / (2πr2), the synthetic force F is represented by F = K / r1 + K / r2. However, it is K
= μI1 · I2 / 2π.
[0042]
Therefore, when the second flat plate 2b is located at the center of the first flat plate 2a and the
third flat plate 2c, r1 = r2, and therefore r1 = r2 = r, the resultant force F = 2K / It becomes r.
Then, when the above-mentioned combined force F = 2 K / r acts on the second flat plate 2 b to
move the second flat plate 2 b by Δr, the combined force F at that time is F = K / (r + Δr) + K /
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(R−Δr) = K / [r (1 + Δr / r)] + K / [r (1−Δr / r)].
[0043]
Assuming that 1 >> Δr / r, then F ≒ K / r + K / r = 2K / r, so that the force F acting on the
second flat plate 2b is independent of the movement amount Δr of the second flat plate 2b. ,
Becomes almost constant. When the current flowing through the conductor line 4b of the second
flat plate 2b is reverse to the direction shown in FIG. 4, the direction of the resultant force F
changes in the direction to bring the second flat plate 2b closer to the first flat plate 2a. Only by
this, the change characteristic of the resultant force F based on the movement of the second flat
plate 2b becomes F ≒ 2K / r described above. Further, even if the movement amount Δr of the
second flat plate 2b is large and 1 >> Δr / r does not hold, the second flat plate 2b is not affected
by the direction of the current flowing through the conductor line 4b of the second flat plate 2b.
The change characteristic of the synthetic force F based on the movement of 2b is expressed by F
= K / (r + Δr) + K / (r−Δr).
[0044]
Therefore, in the flat loudspeaker according to the present embodiment, the amount of vibration
to the first flat plate 2 a (fixed plate) side and the third flat plate 2 c (fixed plate) based on the
drive signal of the second flat plate 2 b (movable plate) Symmetry with the amount of vibration
to the side is secured.
[0045]
In the present embodiment, when the repulsive forces F1 and F2 occur between the first and
second flat plates 2a and 2b, the attractive forces F1 ′ and F2 ′ occur between the second and
third flat plates 2b and 2c. Driving currents are supplied to the flat plates 2a, 2b and 2c by an
amplifier device 10 described later.
In addition, when attractive forces F1 ′ and F2 ′ are generated between the first and second
flat plates 2a and 2b, the amplifier device 10 is configured so that repulsive forces F1 and F2 are
generated between the second and third flat plates 2b and 2c. The drive current is supplied to
each of the flat plates 2a, 2b and 2c. Then, the second flat plate 2b is vibrated by these
operations, and the sound is output by the vibration.
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[0046]
FIG. 7 is a block diagram of an amplifier device 10 including the planar speaker 1. The amplifier
device 10 is for driving the flat loudspeaker 1 shown in FIG.
[0047]
The amplifier device 10 includes an audio signal generation source 11, a pulse width modulation
(PWM) unit 12, a clock generation unit 13, first and second edge trigger units 14a and 14b, a
phase inversion unit 15, and The sixth level shift units 16a to 16f, the first to sixth driving units
17a to 17f, and the first to sixth switching elements 18a to 18f are schematically configured.
[0048]
The audio signal generation source 11 generates an audio signal as an input signal.
The audio signal generated from the audio signal generation source 11 is input to the pulse
width modulation unit 12.
[0049]
The pulse width modulation unit 12 pulse width modulates the audio signal output from the
audio signal generation source 11, and generates and outputs a modulation signal that is a pulse
signal of a fixed cycle in which the duty ratio changes according to the amplitude of the audio
signal. It is As a modulation method in the pulse width modulation unit 12, any of a method
using a sawtooth wave or a triangular wave, a method using charge and discharge of a capacitor,
or any other method may be used. The modulation signal output from the pulse width
modulation unit 12 is input to the first edge trigger unit 14a.
[0050]
The clock generation unit 13 generates a reference clock signal which is a clock signal having a
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duty ratio of approximately 50%. The reference clock signal is used as a reference clock for
generating a modulation signal in the pulse width modulation unit 12 and is used for frequency
division in the second edge trigger unit 14b.
[0051]
The first edge trigger unit 14a detects a falling or rising edge of a modulation signal which is a
pulse signal from the pulse width modulation unit 12, and generates a modulation signal having
a frequency twice that of the original modulation signal. It is a divider circuit. The divided
modulated signal from the first edge trigger unit 14a is input to the first and second level shift
units 16a and 16b.
[0052]
The second edge trigger unit 14 b is a divide-by-two circuit that detects the falling or rising of
the reference clock signal from the clock generation unit 13 and generates a clock signal having
a frequency twice that of the original reference clock signal. . The divided clock signal from the
second edge trigger unit 14 b is input to the third and fourth level shift units 16 c and 16 d and
the phase inversion unit 15.
[0053]
The phase inversion unit 15 inverts the phase of the divided clock signal from the second edge
trigger unit 14b. A phase-inverted and divided reference clock signal (hereinafter referred to as
“inverted divided clock signal”). ) Are input to the fifth and sixth level shift units 16e and 16f.
[0054]
The first to sixth level shift units 16a to 16f shift the reference potential of the pulse width
modulation unit 12 and the reference potential of the clock signal to the reference potential for
driving the first to sixth switching elements 18a to 18f. belongs to. The first to sixth level shift
parts 16a to 16f correspond to the first to sixth driving parts 17a to 17f described later and the
first to sixth switching elements 18a to 18f, respectively.
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[0055]
The first to sixth drivers 17a to 17f are for driving the first to sixth switching elements 18a to
18f. The first to sixth driving units 17a to 17f correspond to the first to sixth switching elements
18a to 18f, which will be described later.
[0056]
The first to sixth switching elements 18a to 18f are formed of, for example, power amplification
type field effect transistors such as MOS-FETs. The first and second switching elements 18a and
18b are connected in series between positive and negative power supply voltages + V and -V, and
their middle point is connected to the second flat plate (movable plate) 2b of the planar speaker
1 And constitute a so-called half bridge circuit. The first and second switching elements 18a and
18b are alternately turned on and off based on the divided modulation signal from the first edge
trigger unit 14a.
[0057]
More specifically, the first switching element 18 a is p-type, and is turned on when the divided
modulation signal is at high level to supply a positive power supply voltage + V to the flat
loudspeaker 1 (flat loudspeaker 1 Supply “discharge current” to The second switching element
18b is n-type, and turns on when the divided modulation signal is at low level, and supplies the
negative power supply voltage -V to the planar speaker 1 ("intake current to the planar speaker 1
is Supply).
[0058]
Further, the third and fourth switching elements 18c and 18d are connected in series between
the positive and negative power supply voltages + V and -V, similarly to the first and second
switching elements 18a and 18b, and their middle point is It is connected to the first flat plate
(fixed plate) 2 a of the flat loudspeaker 1 to constitute a half bridge circuit. The third and fourth
switching elements 18c and 18d are alternately turned on and off based on the divided clock
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signal from the second edge trigger unit 14b.
[0059]
More specifically, the third switching element 18c is p-type, and is turned on when the divided
clock signal is at high level to supply positive power supply voltage + V to the flat loudspeaker 1
(flat loudspeaker 1 Supply “discharge current” to The fourth switching element 18d is n-type,
and is turned on when the divided clock signal is at low level, and supplies the negative power
supply voltage -V to the flat panel speaker 1 Supply).
[0060]
The fifth and sixth switching elements 18e and 18f, like the first and second switching elements
18a and 18b and the third and fourth switching elements 18c and 18d, are connected in series
between positive and negative power supply voltages + V and -V. , And their middle points are
connected to the third flat plate 2c (fixed plate) of the planar speaker 1 to constitute a half bridge
circuit. The fifth and sixth switching elements 18 e and 18 f are alternately turned on and off
based on the inverted divided clock signal from the phase inverting unit 15.
[0061]
More specifically, the fifth switching element 18e is p-type, and is turned on when the inverted
divided clock signal is at high level to supply a positive power supply voltage + V to the planar
speaker 1 (into the planar speaker 1 Supply "discharge current"). The sixth switching element
18f is n-type, and is turned on when the inverted divided clock signal is at low level to supply a
negative power supply voltage -V to the planar speaker 1 ("sucking current" to the planar
speaker 1 Supply).
[0062]
Next, the operation of the above configuration will be described with reference to the timing
chart shown in FIG.
[0063]
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The audio signal (see FIG. 8A) as an analog signal output from the audio signal generation source
11 is pulse width modulated in the pulse width modulation unit 12 according to the reference
clock signal output from the clock generation unit 13 , As a digital signal (see FIG. 8C).
The modulation signal output from the pulse width modulation unit 12 is referred to as a
modulation signal (see FIG. 8D, hereinafter referred to as a “division modulation signal”) that is
divided by the first edge trigger unit 14a. Generated as). The divided modulation signal is
supplied to the first and second level shift units 16a and 16b.
[0064]
The divided modulation signal supplied to the first and second level shift units 16a and 16b is
shifted to the reference potential of the first and second switching elements 18a and 18b, and
the first and second drive units 17a and 17b It is converted into a signal for driving the first and
second switching elements 18a and 18b. Then, they are output to the first and second switching
elements 18a and 18b at predetermined timings.
[0065]
The first and second switching elements 18a and 18b are turned on and off based on driving
signals output from the first and second driving units 17a and 17b. That is, as shown in FIG. 8D,
in the high level period T1 of the divided modulation signal, the first switching element 18a is
turned on, while the second switching element 18b is turned off. As a result, the positive power
supply voltage + V is supplied to the second flat plate (movable plate) 2 b of the flat loudspeaker
1.
[0066]
In addition, in the low level period T2 of the divided modulation signal, the first switching
element 18a is turned off while the second switching element 18b is turned on. Thus, the
negative power supply voltage -V is supplied to the second flat plate 2b. That is, a drive current
in the reverse direction flows to the conductor line 4b of the second flat plate (movable plate) 2b
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in the reverse direction to the period T1 in which the divided modulation signal is at the high
level.
[0067]
The reference clock signal (see FIG. 8 (b)) output from the clock generation unit 13 is a clock
signal divided by the second edge trigger unit 14b (see FIG. 8 (e), hereinafter referred to as
"divided clock signal" . Generated as). The divided clock signal is supplied to the third and fourth
level shift units 16c and 16d.
[0068]
The divided clock signal supplied to the third and fourth level shift units 16c and 16d is shifted
to the reference potential of the third and fourth switching elements 18c and 18d, and the third
and fourth driving units 17c and 17d It is converted into a signal for driving the 3rd and 4th
switching elements 18c and 18d. Then, they are output to the third and fourth switching
elements 18c and 18d at predetermined timings.
[0069]
The third and fourth switching elements 18c and 18d are turned on and off based on drive
signals output from the third and fourth drivers 17c and 17d. That is, as shown in FIG. 8E, in the
high level period T3 of the divided clock signal, the third switching element 18c is turned on
while the fourth switching element 18d is turned off. Thereby, the positive power supply voltage
+ V is supplied to the first flat plate (fixed plate) 2 a of the flat loudspeaker 1.
[0070]
In addition, in the low level period T4 of the divided clock signal, the third switching element 18c
is turned off while the third switching element 18d is turned on. Thereby, negative power supply
voltage -V is supplied to the 1st plane board 2a. That is, in the period T3 in which the divided
clock signal is at the high level, a drive current in the reverse direction flows to the conductor
line 4a of the first flat plate 2a.
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[0071]
The divided clock signal divided in the second edge trigger unit 14 b is referred to as “divided
divided clock signal” hereinafter, with reference to FIG. Generated as). The inverted divided
clock signal is supplied to the fifth and sixth level shift units 16e and 16f.
[0072]
The inverted divided clock signal supplied to the fifth and sixth level shift units 16e and 16f is
shifted to the reference potential of the fifth and sixth switching elements 18e and 18f, and the
fifth and sixth driving units 17e and 17f It is converted into a signal for driving the fifth and sixth
switching elements 18e and 18f. And it outputs to the 5th and 6th switching elements 18e and
18f, respectively at a predetermined timing.
[0073]
The fifth and sixth switching elements 18e and 18f are turned on and off based on drive signals
output from the fifth and sixth driving units 17e and 17f. That is, as shown in FIG. 8F, while the
low level period of the inverted divided clock signal (period in which the divided clock signal is
high level described above) T3, the fifth switching element 18e is turned on, The sixth switching
element 18 f is turned off. Thus, the positive power supply voltage + V is supplied to the third flat
plate 2 c of the flat loudspeaker 1.
[0074]
Further, in the high level period (period in which the divided clock signal is low level) T4 of the
inverted divided clock signal, the fifth switching element 18e is turned off while the sixth
switching element 18f is turned on. Thus, the negative power supply voltage -V is supplied to the
third flat plate 2c. That is, a drive current in the reverse direction flows to the conductor line 4c
of the third flat plate 2c in the period T3 in which the inverted divided clock signal is at the high
level.
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[0075]
Here, referring to FIG. 8G, since the divided clock signal is high level while the divided
modulation signal is low level in period t1, the first and Driving currents in the reverse direction
flow through the conductor lines 4a and 4b of the two flat plates 2a and 2b. As shown in FIGS. 3
and 4, when the drive currents flowing through the conductor lines 4a and 4b are in opposite
directions, repulsive forces F1 and F2 are generated on the first and second flat plates 2a and 2b.
[0076]
In the same period t1, as shown in FIG. 8 (h), while the divided modulation signal is at low level,
the inverted divided clock signal is at low level. Drive currents in the same direction flow through
the conductor lines 4b and 4c of the third flat plates 2b and 2c. As shown in FIGS. 5 and 6, when
the drive currents flowing through the conductor lines 4a and 4b are in the same direction,
attractive forces F1 'and F2' are generated on the second and third flat plates 2b and 2c.
[0077]
Therefore, as shown in FIG. 9, in the period t1, a combined force of the repulsive force F2 and the
attractive force F1 'is generated on the second flat plate 2b. Since this combined force is a force
in the direction in which the second flat plate 2b is brought closer to the third flat plate 2c, the
second flat plate 2b, which is a movable plate, approaches the third flat plate 2c.
[0078]
Further, in period t2, the divided clock signal is also high level while the divided modulation
signal is high level, so the conductor lines of the first and second flat plates 2a and 2b of planar
speaker 1 Drive currents in the same direction flow through 4a and 4b. That is, attractive forces
F1 'and F2' are generated on the first and second flat plates 2a and 2b.
[0079]
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In the same period t2, while the divided modulation signal is high level, the inverted divided
clock signal is low level, so the conductor lines 4b and 4c of the second and third flat plates 2b
and 2c. Drive current flows in the reverse direction. That is, repulsive forces F1 and F2 occur on
the second and third flat plates 2b and 2c.
[0080]
Therefore, as shown in FIG. 10, in period t2, a combined force of attractive force F2 'and
repulsive force F1 is generated on second flat plate 2b, and this combined force brings second
flat plate 2b closer to first flat plate 2a. Because of the force in the direction, the second flat plate
2b, which is a movable plate, approaches the first flat plate 2a.
[0081]
The approaching or separating operation of the second flat plate 2b to the first flat plate 2a and
the third flat plate 2c is similarly performed in the periods t3 and t4 (see FIG. 8), and thereafter
alternately continues. To be done.
[0082]
As described above, as shown in FIGS. 9 and 10, the second flat plate 2b repeats approaching and
separating with respect to the first flat plate 2a and the third flat plate 2c. In the conductor lines
3a, 3b, 3c of the flat plates 2a, 2b, 2c, drive currents having substantially the same magnitude
flow in different flowing directions.
That is, the driving force of the same maximum amplitude value is supplied to the 2nd plane
board 2b.
[0083]
In the related art, in the configuration using only the fixed plate and the movable plate, when the
movable plate has a pulling force that brings the movable plate close to the fixed plate and the
movable plate moves and the movable plate generates a repulsive force that moves away from
the fixed plate, the movable plate moves The amount of movement of the movable plate is
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different, and it has been difficult to cause the movable plate to generate an appropriate vibration
according to the drive signal.
On the other hand, in the present embodiment, two first and third flat plates (fixed plates) 2a and
2c are provided so as to sandwich the second flat plate (movable plate) 2b, and both the first and
third flat plates are fixed. The force is generated from the face plates (fixed plates) 2a and 2c to
the second flat plate (movable plate) 2b, and the second flat plate (movable plate) 2b is vibrated
by the resultant force. Even if the direction of the drive current flowing through the conductor
line 4b of 2b changes and the direction of vibration of the second flat plate (movable plate) 2b
changes, the symmetry of the amount of vibration in both directions of vibration can be
maintained. Therefore, an appropriate vibration can be generated according to the drive current,
and accordingly, a sound according to the positive and negative amplitudes of the audio signal
can be appropriately output.
[0084]
Further, as shown in FIG. 2, the second flat plate 2b is configured to be sandwiched between the
first flat plate 2a and the third flat plate 2c made of resin via the first spacer 3a and the second
spacer 33b. Therefore, the second flat plate 2b can be protected even if there is an external
impact, for example.
[0085]
FIG. 11 is a block diagram showing a modification of the amplifier device 10 including the flat
loudspeaker 1 shown in FIG.
In the configuration of this modification, a signal based on the divided clock signal is supplied to
the second flat plate 2b of the planar speaker 1, and a signal based on the divided modulation
signal is supplied to the first flat plate 2a, This embodiment differs from the above-described
embodiment in that a signal based on the divided and phase-inverted modulation signal is
supplied to the third plane plate 2c.
[0086]
That is, in the above embodiment, the signal based on the modulation signal is supplied to the
second flat plate 2b which is the movable plate, but in this modification, the signal based on the
clock signal is supplied to the second flat plate 2b. A signal based on the modulation signal is
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supplied to the first and second flat plates 2a and 2c which are fixed plates.
[0087]
More specifically, the clock signal from the clock generation unit 13 is input to the first edge
trigger unit 14a, and the divided clock signal is divided into first and second level shift units 16a
and 16b, and first and second drive units. The signals are input to the first and second switching
elements 18a and 18b through 17a and 17b.
Then, signals switched at positive and negative power supply voltages ± V based on the clock
signals phase-inverted from the first and second switching elements 18a and 18b are supplied to
the second flat plate (movable plate) 2b.
[0088]
Further, the modulation signal from the pulse width modulation unit 12 is input to the second
edge trigger unit 14b, and the divided modulation signal is converted to the third and fourth
level shift units 16c and 16d, and the first and second drive units 17c, The signal is input to the
third and fourth switching elements 18c and 18d through 17d. Then, a signal switched at
positive and negative power supply voltages ± V based on the modulation signal divided from
the third and fourth switching elements 18c and 18d is supplied to the first flat plate (fixed plate)
2a.
[0089]
Furthermore, the divided modulation signal from the second edge trigger unit 14b is input to the
phase inversion unit 15, and the divided and phase-inverted modulation signal is converted to
the fifth and sixth level shift units 16e and 16f, and the first And the third and fourth switching
elements 18e and 18f via the second drive units 17e and 17f. Then, a signal switched at positive
and negative power supply voltages ± V based on the modulation signal divided and phaseinverted from the third and fourth switching elements 18e and 18f is supplied to the third flat
plate (fixed plate) 3a . The other configuration is substantially the same as that of the abovedescribed embodiment.
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[0090]
Also in this configuration, since the driving force having the same maximum amplitude value is
supplied to the second flat plate 2b which is the movable plate in the case where the attractive
force is generated and the case where the repulsive force is generated, the upper and lower sides
of the second flat plate 2b are provided. The symmetry of the vibration of can be maintained.
Therefore, an appropriate vibration can be generated according to the drive current.
[0091]
Note that the signals supplied to the first flat plate 2a and the third flat plate 2c may be
interchanged, that is, the signal based on the divided modulation signal is supplied to the third
flat plate 2c, divided and divided. A signal based on the inverted modulation signal may be
supplied to the first flat plate 2a.
[0092]
Of course, the scope of the present invention is not limited to the above-described embodiment,
and the circuit configuration and the block configuration shown in the above embodiment are
merely an example, and various circuit configurations are possible as long as they have
equivalent functions. And block configurations can be applied.
[0093]
It is a schematic block diagram of the flat type speaker which concerns on this invention.
It is a schematic perspective view of a flat type speaker.
It is a schematic block diagram of a planar speaker, and shows the case where repulsive force
arises between conductor tracks. It is an operation principle figure of a flat type speaker, and
shows the case where repulsive force arises between conductor tracks. It is a schematic block
diagram of a planar speaker, and shows the case where an attractive force arises between
conductor tracks. It is an operation principle figure of a flat type speaker, and shows the case
where an attractive force arises between conductor tracks. It is a block block diagram of an
amplifier apparatus. It is a timing chart for explaining the operation of an amplifier device. It is a
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figure for demonstrating the operation | movement of a 1st thru | or 3rd plane board. It is a
figure for demonstrating the operation | movement of a 1st thru | or 3rd plane board. It is a
block block diagram which shows the modification of an amplifier apparatus. It is a figure for
demonstrating the operation principle of a flat type | mold speaker, and shows the case where an
attractive force arises between conductor tracks. It is a figure for demonstrating the operation
principle of a planar speaker, and shows the case where repulsive force arises between conductor
lines. It is a figure for demonstrating the relationship between a drive current and the drive force
supplied to a movable plate.
Explanation of sign
[0094]
DESCRIPTION OF SYMBOLS 1 planar speaker 2a 1st flat board (movable board) 2b 2nd flat
board (fixed board) 2c 3rd flat board (fixed board) 3a 1st spacer 3b 2nd spacer 4a, 4b, 4b
conductor track 5 opening 10 amplifier Device 11 Audio signal source 12 Pulse width
modulation unit 13 Clock generation unit 14a First edge trigger unit 14b Second edge trigger
unit 15 Phase inversion unit 16a First level shift unit 16b Second level shift unit 16c Third level
shift unit 16d Fourth level shift unit 17a First drive unit 17b Second drive unit 17c Third drive
unit 17d Fourth drive unit 18a First switching element 18b Second switching element 18c Third
switching element 18d Fourth switching element
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