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DESCRIPTION JP2007049437

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DESCRIPTION JP2007049437
The present invention provides a highly efficient power superimposing type speaker system
capable of superimposing / separating a power source and an audio signal with a simple circuit
configuration. An audio signal input to a power supply superimposing device 20 is modulated to
a PWM signal by a PWM converter 22, converted to a bipolar PPM signal by a superimposing
circuit 23, and superimposed on a power supply voltage as a superimposed signal. It is output.
The superimposed signal is input to the amplifier built-in speaker 30 and separated into the
original PWM signal and the power supply voltage by the separation and PWM reproduction
circuit 31. The PWM signal is amplified by the PWM driver 32, input to the speaker 34 through
the low pass filter 33, and output as sound. [Selected figure] Figure 1
Speaker system, speaker device and power supply superposing device
[0001]
The present invention relates to a speaker system for audio output, and more particularly to a
system having an amplifier built-in speaker.
[0002]
Conventionally, in a general audio device, the amplifier and the speaker were housed in separate
housings, but with the spread of portable portable players and personal computers, the demand
for speakers with built-in amplifiers that can be connected to them increases (E.g., Patent
Document 1).
[0003]
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1
In order to operate the amplifier built-in speaker, it is necessary not only to input an audio signal
but also to supply power to the amplifier in the speaker.
Therefore, the conventional speaker with a built-in amplifier requires two input lines of a power
supply line and a signal line.
When a plurality of speaker input lines are required as described above, not only the
arrangement of the speakers becomes inconvenient, but it also causes a loss of aesthetics.
[0004]
Therefore, in recent years, an audio signal is superimposed on the power supply voltage, and the
power supply and the audio signal are transmitted to the speaker by a single wiring, thereby
sharing the power supply line and the signal line that the amplifier built-in speaker should have.
Superimposed speaker systems have been developed.
[0005]
JP 2004-229250 A
[0006]
In the power superimposing type speaker system, the circuit for superimposing the audio signal
and the power supply voltage on the transmission side of the audio signal and the circuit for
separating the both again on the speaker side are complicated, which causes an increase in cost.
[0007]
The present invention has been made to solve the above problems, and it is possible to provide a
highly efficient power supply superimposed speaker system which can superimpose / separate a
power supply and an audio signal with a simple circuit configuration. The purpose is.
[0008]
The speaker system according to the present invention comprises a PWM modulator for
modulating an audio signal to a PWM (Pulsed Wave Modulation) signal, and a superimposed
signal obtained by converting the PWM signal to a bipolar PPM (Pulse Position Modulation)
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2
signal and superposing it on a power supply voltage. The signal processing apparatus may
include a superposition circuit that generates a signal, a separation circuit that separates the
PWM signal from the superposition signal, and a speaker that outputs sound based on the PWM
signal obtained by the separation circuit.
[0009]
According to the present invention, since an audio signal is converted to an impulse of a PPM
signal and superimposed on a power supply voltage, there is no need to use a special modulation
/ demodulation circuit as in the case of superposing an analog signal, and it is relatively simple.
The configuration can superimpose / separate the audio signal and the power supply voltage,
which can contribute to the cost reduction of the speaker system.
Further, since the power is amplified and the speaker is driven in the state of the pulse signal
(PWM signal), the power efficiency is higher than that of a conventional speaker system using an
analog amplifier.
[0010]
First Embodiment FIG. 1 is a diagram showing a configuration of a speaker system according to a
first embodiment of the present invention.
As shown in the figure, this speaker system comprises an audio signal source 10, a power source
superimposing device 20, and an amplifier built-in speaker 30.
[0011]
The audio signal source 10 is an apparatus that outputs an audio signal, such as a portable
player or a personal computer.
[0012]
The power supply superimposing device 20 is a device that superimposes an audio signal output
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from the audio signal source 10 on a power supply supplied from a predetermined power supply
line and transmits it to the amplifier built-in speaker 30. The power supply circuit 21 includes
PWM (Pulsed Wave Modulation). ) A converter 22 and a superposition circuit 23 are provided.
The power supply circuit 21 is a circuit that generates a predetermined power supply voltage for
driving the amplifier built-in speaker 30 from the power supply supplied from the power supply
line.
The PWM converter 22 is a circuit that PWM modulates an audio signal and outputs it as a PWM
signal.
The superposition circuit 23 is a circuit that converts a PWM signal into a bipolar (bipolar) PPM
(Pulse Position Modulation) signal and generates a superposition signal in which the signal is
superimposed on a power supply voltage.
[0013]
Here, the bipolar PPM signal is a PPM signal having positive and negative pulses.
When the PWM signal is converted to a PPM signal, for example, the rising edge of each pulse of
the PWM signal is converted to a positive pulse, and the falling edge is converted to a negative
pulse. In that case, the pitch from the positive pulse to the next negative pulse in the converted
PPM signal corresponds to each pulse width of the PWM signal of the conversion source.
[0014]
The amplifier built-in speaker 30 is a speaker device that outputs sound based on the
superimposed signal transmitted from the power supply superimposing device 20, and includes a
separation and PWM reproduction circuit 31, a PWM driver 32, a low pass filter 33, and a
speaker 34. The separation and PWM regeneration circuit 31 is a circuit that receives the
superimposed signal from the power source superposition device 20 and separates the original
power supply voltage and the PWM signal from the superimposed signal. The PWM driver 32 is
an amplifier circuit that amplifies the PWM signal. The low pass filter 33 is a circuit for removing
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an unnecessary high frequency component contained in the PWM signal, and the signal is input
to the speaker 34 through the low pass filter 33.
[0015]
Hereinafter, the operation of this speaker system will be described. The audio signal output from
the audio signal source 10 is input to the PWM converter 22 of the power supply superimposing
device 20. The PWM converter 22 PWM modulates the input audio signal and inputs it to the
superposition circuit 23 as a PWM signal. The superimposing circuit 23 converts the PWM
signal into a bipolar (bipolar) PPM signal and, as shown in FIG. 2, generates a superimposed
signal in which the PPM signal is superimposed on the power supply voltage generated by the
power supply circuit 21. . FIG. 2 shows an example in which PPM conversion is performed in
which the rising edge of the PWM signal is converted to a positive impulse and the falling edge is
converted to a negative impulse. The superposition circuit 23 transmits the generated
superposition signal to the amplifier built-in speaker 30.
[0016]
The superimposed signal input from the power supply superimposing device 20 (superimposing
circuit 23) to the amplifier built-in speaker 30 is input to the separation and PWM regeneration
circuit 31. The separation and PWM regeneration circuit 31 separates the PPM signal (positive
and negative impulses) which is the high frequency component of the superimposed signal,
regenerates the original PWM signal, and inputs it to the PWM driver 32. At the same time, the
DC component of the superimposed signal is supplied to the PWM driver 32 as a power supply
voltage. As a result, as shown in FIG. 2, the power supply voltage and the PWM signal are
separated from the superimposed signal.
[0017]
The PWM driver 32 amplifies the PWM signal obtained by the separation and PWM regeneration
circuit 31. Thus, the PWM signal has power capable of driving the speaker 34. After the
unnecessary high frequency component is removed by the low pass filter 33, the amplified PWM
signal is input to the speaker 34 and output as sound. That is, the speaker 34 according to the
present embodiment is driven by the PWM signal amplified by the PWM driver 32.
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[0018]
According to the present embodiment, since the audio signal is converted to an impulse of the
PPM signal and superimposed on the power supply voltage, there is no need to use a special
modulation / demodulation circuit as in the case of superposing the analog signal. The audio
signal and the power supply voltage can be superimposed / separated with a simple
configuration, which can contribute to the cost reduction of the speaker system. Further, since
the power is amplified and the speaker is driven in the state of the pulse signal (PWM signal), the
power efficiency is higher than that of a conventional speaker system using an analog amplifier.
[0019]
In the present embodiment, the low pass filter 33 is interposed between the PWM driver 32 and
the speaker 34. However, the low pass filter 33 not only removes noise components
accompanying PWM modulation, but also performs so-called unnecessary radiation ( EMC:
Function to remove Electro Magnetic Compatibility. This unnecessary radiation is generated, for
example, by a wiring (a so-called “speaker code”) for transmitting the amplified PWM signal
(so-called “speaker cord”). Is performed close to the speaker 34, unnecessary radiation is
reduced. When the unnecessary radiation is reduced, it can be expected that the low-pass filter
33 can be omitted from the amplifier built-in speaker 30 of the present embodiment, in which
case the cost can be further reduced. When the low pass filter 33 is omitted, the PWM signal
amplified by the PWM driver 32 is directly input to the speaker 34. However, due to the
characteristics of the speaker, it is impossible to output a component having a frequency higher
than a certain level. It is possible to output a normal voice as a result.
[0020]
Also in the PWM driver 32, unnecessary radiation may occur because of high-speed switching of
large power at the time of amplification of the PWM signal. However, in the system according to
the present embodiment, the PWM driver 32 is mounted on the speaker 30 with an amplifier. It
has a structure isolated from other circuits (circuits of the power supply superimposing device
20 and the audio signal source 10). Therefore, the unnecessary radiation countermeasure can be
taken for the PWM driver 32 alone, and there is also an advantage that the countermeasure
against the unnecessary radiation of the whole system becomes easy.
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[0021]
Furthermore, since the transmission of the power supply voltage and the audio signal from the
power supply superimposing device 20 to the amplifier built-in speaker 30 is performed by the
superposition signal, it is possible to perform the transmission of both by a single wiring.
Therefore, when the power supply superimposing device 20 and the amplifier built-in speaker 30
are respectively housed in separate housings, the degree of freedom of the arrangement of the
amplifier built-in speaker 30 is improved, and the deterioration of the appearance of the speaker
system can be suppressed.
[0022]
Second Embodiment FIG. 3 is a diagram showing a configuration of a speaker system according
to a second embodiment of the present invention. As shown in the figure, this speaker system
comprises an audio signal source 10, a power supply superimposing device 20, and an amplifier
built-in speaker 40. The audio signal source 10 and the power supply superimposing device 20
are the same as those described in the first embodiment, and thus the description thereof is
omitted here.
[0023]
The amplifier built-in speaker 40 is a speaker device that outputs sound based on the
superimposed signal transmitted from the power supply superimposing device 20, and includes a
separation and PWM reproduction circuit 41, a low pass filter 42, an equalizer 43, a PWM
system amplifier 44 and a speaker 45. Have. The separation and PWM regeneration circuit 41 is
a circuit that receives the superimposed signal output from the power source superposition
device 20 and separates the original power supply voltage and the PWM signal from the
superimposed signal. The low pass filter 42 is a circuit that removes high frequency components
from the PWM signal, and in the present embodiment functions as a demodulation circuit that
demodulates the PWM signal into an analog audio signal. The equalizer 43 is a circuit that
adjusts the overall frequency characteristics of the audio signal to correct the sound quality. The
PWM system amplifier 44 is a circuit for amplifying an audio signal, and the speaker 45 is driven
by the audio signal amplified by the PWM system amplifier 44.
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[0024]
The PWM type amplifier has an operation principle different from that of the conventional
analog type amplifier. That is, in the amplifier of the PWM system, the input audio signal is once
modulated to a PWM signal and then amplified, and then it is demodulated by a low pass filter
into an analog audio signal suitable for speaker driving and output. Since the amplification
operation is performed on the pulse signal (PWM signal) as described above, highly efficient
amplification is possible.
[0025]
Hereinafter, the operation of this speaker system will be described. The audio signal output from
the audio signal source 10 is converted into a PWM signal by the PWM converter 22 of the
power supply superimposing device 20 as in the first embodiment. Then, the signal is converted
into a bipolar PPM signal and superimposed on the power supply voltage by the superposition
circuit 23, and is output from the power supply superposition device 20 as a superposition
signal.
[0026]
The superimposed signal transmitted from the power source superimposing device 20 to the
amplifier built-in speaker 40 is input to the separation and PWM regeneration circuit 41. The
separation and PWM regeneration circuit 41 separates the PPM signal (positive and negative
impulses), which is the high frequency component of the superimposed signal, regenerates the
original PWM signal, and inputs it to the low pass filter 42. At the same time, the DC component
of the superimposed signal is supplied to the equalizer 43 and the PWM system amplifier 44 as a
power supply voltage.
[0027]
The PWM signal obtained by the separation and PWM regeneration circuit 41 is demodulated
into an analog audio signal by the low pass filter 42, and is input to the equalizer 43. The
equalizer 43 adjusts the overall frequency characteristics of the input audio signal, and inputs
the adjusted audio signal to the PWM amplifier 44. The PWM system amplifier 44 amplifies the
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audio signal. Thus, the audio signal has power capable of driving the speaker 45. The amplified
audio signal drives the speaker 45, and the speaker 45 outputs audio.
[0028]
Also in this embodiment, since the audio signal is converted to an impulse of the PPM signal and
superimposed on the power supply voltage, the audio signal and the power supply voltage can be
superimposed / separated with a relatively simple configuration, and the cost of the speaker
system It can contribute to the reduction.
[0029]
Further, in the present embodiment, the PWM signal is demodulated to an analog audio signal
prior to amplification, but amplification of the audio signal is performed by an amplifier of the
PWM system, so that the conventional analog is used as in the first embodiment. Power
efficiency is higher than a speaker system using an amplifier.
Further, since the PWM signal is demodulated to the audio signal prior to the amplification, the
equalizer 43 can be interposed, and the advantage that the sound quality can be improved can be
obtained.
[0030]
Furthermore, since the transmission of the power supply voltage and the audio signal from the
power supply superimposing device 20 to the amplifier built-in speaker 40 is performed by the
superposition signal, it is possible to perform the transmission of both by a single wiring.
Therefore, when the power supply superimposing device 20 and the amplifier built-in speaker 40
are housed in separate housings, the degree of freedom in the arrangement of the amplifier builtin speaker 40 is improved, and a decrease in the appearance of the speaker system can be
suppressed.
[0031]
FIG. 1 is a diagram showing a configuration of a speaker system according to Embodiment 1. FIG.
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6 is a diagram for explaining the operation of the speaker system according to the first
embodiment. FIG. 7 is a diagram showing a configuration of a speaker system according to
Embodiment 2.
Explanation of sign
[0032]
DESCRIPTION OF SYMBOLS 3 audio signal source, 20 power supply superimposing apparatus,
21 power supply circuit, 22 PWM converter, 23 superimposing circuit, 30 amplifier built-in
speaker, 31 separation and PWM reproducing circuit, 32 PWM driver, 33 low pass filter, 34
speaker, 40 amplifier built-in speaker , 41 separate and PWM regeneration circuits, 42 low pass
filters, 43 equalizers, 44 PWM amplifiers, 45 speakers.
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