DESCRIPTION JP2000347678

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DESCRIPTION JP2000347678
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates in
particular to a tone generation circuit using a magnetic sounder.
[0002]
2. Description of the Related Art Conventionally, a small magnetic sounder is often used to make
a ringing tone etc. of a mobile telephone device, and there is a growing market demand for
simultaneously using two or more tones. There is. FIG. 7 is an electric circuit diagram showing a
configuration of a conventional tone generation circuit 100B. As shown in FIG. 7, when adding
two tones, the conventional tone generation circuit 100B adds the tones Vtn1s and Vtn2s, which
are sin waves output from the two sound sources 31 and 32, by the adder 35. The output
waveform Vout is obtained by
[0003]
SUMMARY OF THE INVENTION However, in the conventional addition waveform of sin waves,
there is a problem that a sufficient sound pressure level can not be obtained when a magnetic
sounder is used. The present invention has been made in view of such problems, and an object
thereof is to provide a tone generation circuit capable of generating a sufficient sound pressure
level when using a magnetic sounder. is there.
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[0004]
[Means for Solving the Problems] In order to solve the above problems, the present invention has
the following constitution. The gist of the invention according to claim 1 is a tone generation
circuit comprising a plurality of sound sources, wherein a sound source A generating an audio
signal A and a sound signal A outputted from the sound source A are compared with a threshold
value. A binary approximation means A for binarizing and outputting, a sound source B for
generating an audio signal B, and a binarization for binarizing by comparing the audio signal B
outputted from the sound source B with a threshold value A tone generating circuit comprising:
means B; and addition means for adding the audio signal A and the audio signal B. According to a
second aspect of the present invention, the binary approximation means A compares the voltage
level of the audio signal A with the level of a reference voltage externally input as a threshold,
and the voltage level of the audio signal A is The voltage comparator outputs H level when the
voltage is higher than the level of the reference voltage, and outputs L level when the voltage
level of the audio signal A is lower than the level of the reference voltage. It exists in the tone
generation circuit. According to a third aspect of the present invention, the binary approximating
means B compares the voltage level of the audio signal B with the level of the reference voltage
input from the outside as a threshold, and determines the voltage level of the audio signal B. The
voltage comparator outputs H level when the voltage of the audio signal B is higher than the
level of the reference voltage, and outputs L level when the voltage level of the audio signal B is
lower than the level of the reference voltage. It exists in the tone generation circuit described in
2. According to a fourth aspect of the present invention, the adding means receives the outputs
of the binary approximating means A and the binary approximating means B at its non-inverting
input terminal, and receives the reference voltage at its inverting input terminal. The tone
generation circuit according to any one of claims 1 to 3, further comprising: an operational
amplifier whose output is connected to the non-inverting input terminal via a feedback resistor. A
gist of the invention according to claim 5 is that a resistor is interposed between the noninverting input terminal of the operational amplifier and the binary approximation means A. It
exists in the generation circuit. The subject matter of the invention according to claim 6 is that a
resistor is interposed between the non-inverting input terminal of the operational amplifier and
the binary approximation means B. Resides in the tone generation circuit of FIG. The gist of the
invention according to claim 7 is that the sound signal A generated by the sound source A and
the sound signal B generated by the sound source B are analog signals. It exists in the tone
generation circuit described in the paragraph.
The gist of the invention according to claim 8 is characterized in that said binary approximation
means A is a code extraction circuit for extracting and outputting only two predetermined values
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of said audio signal A. The tone generation circuit according to any one of. The gist of the
invention according to claim 9 is characterized in that the binary approximation means B is a
code extraction circuit for extracting and outputting only two predetermined values of the audio
signal B. The tone generation circuit according to any one of the above. The gist of the invention
according to claim 10 is characterized in that the addition means adds the output of the binary
approximation means A and the output of the binary approximation means B and outputs as a
ternary digital audio signal output. The tone generation circuit according to claim 8 or 9. The gist
of the invention according to claim 11 is the tone generation circuit according to claim 10,
characterized in that it comprises a digital-to-analog converter for converting the ternary digital
audio signal output outputted from the addition means into an analog audio signal. To be. The
gist of the invention according to claim 12 is that the audio signal A generated by the sound
source A and the audio signal B generated by the sound source B are digital signals. It exists in
the tone generation circuit described in the paragraph. The subject matter of the invention
according to claim 13 resides in an IC provided with the tone generation circuit according to any
one of claims 1 to 12. The gist of the invention according to claim 14 resides in an electric circuit
board provided with the tone generation circuit according to any one of claims 1 to 12. The
subject matter of the invention according to claim 15 resides in a mobile communication
apparatus provided with the tone generation circuit according to any one of claims 1 to 12. The
subject matter of the invention according to claim 16 resides in a mobile phone provided with
the tone generation circuit according to any one of claims 1 to 12. The gist of the invention
according to claim 17 is a tone generation method comprising a plurality of sound sources,
wherein the sound source A generates an audio signal A, and the binary approximation means A
outputs the audio signal A output from the sound source A. The sound source B generates an
audio signal B by comparing with the threshold value and the sound source B generates an audio
signal B, and the binary approximating means B compares the audio signal B output from the
sound source B with a threshold value to binarize. The tone generation method is characterized
in that the audio signal A and the audio signal B are added by the addition means.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described in detail below with reference to the drawings. -Embodiment 1-Fig. 1 is an electric
circuit diagram showing a tone generation circuit 100 in the first embodiment of the present
invention. As shown in FIG. 1, in the case of adding two tones, the tone generation circuit 100
according to the first embodiment has two tones approximating the tones Vtn1 and Vtn2 output
from the two sound sources 1 and 2. , And 4 respectively, and the binary approximate outputs
Vcmp 1 and Vcmp 2 are added by the adder 5 to obtain an output waveform Vout which is a
ternary approximate rectangular wave. The output waveform Vout is an approximate waveform
of a waveform (sin waveform) obtained by directly adding the tones Vtn1 and Vtn2, and includes
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many frequency components the same as those of the two tones. In addition, since the rising /
falling of the waveform is sharp, it is suitable for gaining sound pressure with a magnetic
sounder or the like.
[0006]
FIG. 2 is an electric circuit diagram showing an internal configuration of tone generation circuit
100 shown in FIG. In the first embodiment, it comprises only an analog circuit. The sound source
1 and the sound source 2 respectively include an analog sound source 11 and an analog sound
source 12, and the binary approximation circuit 3 and the binary approximation circuit 4
respectively include a comparator 13 and a comparator 14. Further, the adder 5 includes an
analog adder 15.
[0007]
Two different tones Vtn1 and Vtn2 are output from the analog sound sources 11 and 12,
respectively. The tones Vtn1 and Vtn2 are input to the comparators 13 and 14, respectively,
compared with the reference voltage VR, and approximately converted into binary approximation
outputs Vcmp1 and Vcmp2. The binary approximation outputs Vcmp 1 and Vcmp 2 are added by
the analog adder 15 of the inverting amplifier configuration including the operational amplifier
18 and the resistor 16 to obtain a ternary output waveform Vout.
[0008]
Next, the operation of the first embodiment will be described with reference to FIGS.
[0009]
FIG. 3 shows analog waveforms of tones Vtn1 and Vtn2 output from the analog sound sources
11 and 12 of the tone generation circuit 100 according to the first embodiment of this invention.
The tones Vtn1 and Vtn2 are compared with the reference voltage VR by the comparators 13
and 14, respectively, and the value of the reference voltage VR is set to the center value of each
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sound source output. Assuming that the high level voltage output from each of the comparators
13 and 14 is VH and the low level voltage is VL, the waveforms of the binary approximate
outputs Vcmp1 and Vcmp2 are as shown in FIG. When the two outputs (Vcmp 1, Vcmp 2) are
respectively added by the analog adder 15 with a gain of 0.5, the waveform of the output
waveform Vout after the addition becomes as shown by the solid line in FIG. When a waveform
(prior art) in which the tones Vtn1 and Vtn2 are directly added is superimposed here, it becomes
as shown by a dotted line.
[0010]
Comparing the two shown in FIG. 5, the addition output waveform (Vout) according to the
present invention is an approximation of the addition waveform according to the prior art, and
the frequency components of the tones Vtn1 and Vtn2 output from the analog sound sources 11
and 12 It can be seen that it contains a lot of In addition, since the change in rise / fall of the
waveform is sharper than that in the prior art, the waveform is suitable for driving a magnetic
sounder or the like which can not gain sound pressure without rectangular wave driving.
[0011]
Since the tone generation circuit 100 according to the first embodiment is configured as
described above, the following effects can be obtained. The effect of the present invention is that
even when two or more tones are added, the sound can be produced with a high sound pressure
as compared with the prior art using a magnetic sounder or the like.
[0012]
The reason is that, for a magnetic sounder or the like which can acquire sound pressure with a
rectangular wave, driving is performed with a waveform converted into an approximate
rectangular waveform having the same rise / fall as the rectangular wave.
[0013]
Second Embodiment Next, a second embodiment of the present invention will be described with
reference to the drawings.
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In the second embodiment, a case where the present invention is realized by a digital circuit will
be described.
[0014]
FIG. 6 is an electric circuit diagram showing the tone generation circuit 100A in the second
embodiment of the present invention. In the second embodiment, the sound source is a digital
sound source 21, 22, the binary approximation circuit is a code extraction circuit 23, 24, and the
adder is a digital adder 25 as compared with the first embodiment described above. However, a D
/ A converter 26 with a ternary output is added to the output unit. The digital sound sources 21
and 22 output digital tone signals Dtn1 and Dtn2 in 2's complement format having a
predetermined number of bits. The digital tone signals Dtn1 and Dtn2 are signals such that
respective tone waveforms can be obtained by D / A conversion. The code extraction circuits 23
and 24 extract and output only code bits Dcmp1 and Dcmp2 (binary values) of the digital tone
signals Dtn1 and Dtn2. This operation is equivalent to that of the comparators 13 and 14 in the
first embodiment described above. The obtained code bits Dcmp1 and Dcmp2 are passed to the
digital adder 25 and added to be converted into a ternary digital signal, which is converted into
an analog voltage by the D / A converter 26 with a ternary output. A waveform equivalent to that
of the first embodiment is obtained.
[0015]
In the second embodiment, by configuring the central portion of the circuit with a digital circuit,
there is an advantage that the area can be reduced when configured on a semiconductor
integrated circuit or the like.
[0016]
In these embodiments, the present invention is not limited thereto, and can be applied to a form
suitable for applying the present invention.
[0017]
Further, the number, the position, the shape and the like of the component members are not
limited to those in the above-described embodiment, and the number, the position, the shape and
the like suitable for practicing the present invention can be employed.
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[0018]
In the drawings, the same components are denoted by the same reference numerals.
[0019]
Since the present invention is configured as described above, it is possible to obtain an adequate
sound pressure level even when using a magnetic sounder in the tone generation circuit. Play.
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