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DESCRIPTION JP2005130192

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DESCRIPTION JP2005130192
An amplifier and an audio device capable of driving a speaker while achieving cost reduction
without requiring a dedicated power supply circuit for operating the amplifier are realized. An
output transistor (501 to 504) is switched by a 1-bit signal generated by a ΔΣ block (101) to
amplify the 1-bit signal. When driving the headphone 701, it is connected to the positive phase
analog output 511 terminal and the negative phase analog output 512 terminal, amplified by the
first power supply voltage, and the positive phase signal is passed through the first LPF including
the coil 505 and the capacitor 507 to reverse The phase signal is passed through a second LPF
consisting of a coil 506 and a capacitor 508. When driving the speaker, it is connected to the
positive phase digital output terminal 513 and the negative phase digital output terminal 514,
and is amplified by the second power supply voltage larger than the first power supply voltage to
directly output the positive phase signal and the negative phase signal. . This provides an output
sufficient to drive the speaker. [Selected figure] Figure 1
Audio equipment and systems
[0001]
The present invention relates to an audio apparatus and an audio system to which a speaker
whose driving ability is insufficient only by an internal power supply is connected.
[0002]
Conventionally, portable audio devices have been present.
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An audio device is an audio reproduction device such as stereo. Here, portable audio devices are
usually used to listen to sounds using headphones or earphones, and listening to sounds using
speakers has been entrusted to stationary audio devices. However, portable audio devices are
convenient to carry, and it is convenient for users if they can connect to speakers and hear
sounds.
[0003]
In conventional portable audio devices, when using a speaker to reproduce audio externally,
there is a method of connecting a speaker to a headphone terminal of the audio device, driving
the speaker, and playing a sound. However, in this case, the output terminal of the portable audio
device is originally for headphones, and when a speaker is connected, the audio output level of
the portable audio device is low and the speaker can not be sounded sufficiently. Therefore, the
audio output from the headphone terminal was once input to the amplifier, the audio output was
amplified by the amplifier, and the sound was emitted from the speaker. Therefore, in this case, a
power supply circuit for supplying power to the amplifier and the amplifier is required (for
example, Patent Document 1).
[0004]
FIG. 4 shows the configuration shown as a specific conventional example of an audio device, and
a partial change is made to compare "sound source device, portable sound source device and
sound system" (Patent Document 1) with an embodiment of the present invention. It is In the
audio device 10 of FIG. 4, the sound source unit 31 is controlled by the microcomputer 21
supplied with power from the power supply and charging circuit 61, and the sound is emitted by
the headphones 71 connected to the headphone terminal 41 provided in the sound source unit
31. ing.
[0005]
Further, in FIG. 5, the audio device 10 is connected to the external speaker system 80 by the
headphone terminal 41, and amplification is performed by the amplifier circuit 82 built in the
speaker system 80 to drive the speaker 81 to emit sound. It shows the state. The amplifier circuit
82 of FIG. 5 is for amplifying an audio signal, and at the same time, the speaker system 80 is
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provided with a power supply circuit 83 for supplying power to the amplifier circuit 82. At this
time, a charger 85 for charging the power supply / charging circuit 61 is used. As shown in FIG.
5, the audio device 10, the speaker system 80, and the charger 85 are separately separated.
When the charger 85 is not used, the power supply / charging circuit 61 is an internal power
supply isolated from the outside. JP 2001-275260 A (released on October 5, 2001) JP 2002246852 A (released on August 30, 2002)
[0006]
However, in the configuration of the conventional audio apparatus as shown in FIGS. 4 and 5,
when the speaker connected to the headphone terminal is driven without using an amplifier such
as the amplifier circuit 82, the user may hear a desired sound. Can not. This is because the
output terminal of the conventional portable audio device is provided to connect headphones or
earphones, and the output voltage is low.
[0007]
The reason why the voltage at the output terminal for headphones or earphones is low is that if
the voltage is high, the headphones or earphones are burdened and there is a risk of failure. Also,
with this type of audio device, the output and power supply time is insufficient for driving the
speaker with the internal power supply of the audio device alone. Therefore, when connecting a
speaker to a portable audio device and listening to the sound, it is necessary to once input the
output from the headphone terminal to an amplifier for the speaker, amplify it by the amplifier,
and then drive the speaker. Furthermore, since the power must be supplied to the amplifier, a
dedicated power supply circuit for that is also required. The power supply circuit 83 of FIG. 5 is a
power supply circuit for this purpose, and is provided separately from the charger 85. Therefore,
there is a problem that the cost is increased to drive the speaker.
[0008]
The present invention has been made in view of the above problems, and its object is to eliminate
the need for a dedicated power supply circuit for operating an external amplifier and an amplifier
provided for a speaker whose driving ability is insufficient only with the internal power supply,
An object of the present invention is to provide an audio device and an audio system capable of
driving a speaker while reducing the cost.
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[0009]
In order to solve the above problems, the audio device according to the present invention does
not pass through the low-pass filter after being generated from the power supply and the first
output terminal that outputs a signal that has been generated from the power supply and then
passed through the low-pass filter. A power supply voltage for generating a signal voltage when
outputting a signal from the first output terminal is a first power supply voltage, and the second
output is provided with two output terminals with a second output terminal for outputting a
signal. When a power supply voltage for generating a signal voltage when a signal is output from
a terminal is a second power supply voltage, the second power supply voltage is made larger
than the first power supply voltage.
[0010]
In order to solve the above problems, an audio device according to the present invention
converts 1-bit signal which converts an audio signal consisting of an analog signal or a digital
signal allocated and expressed by multiple bits into a 1-bit signal allocated by 1 bit. And onephase amplifying means for amplifying one signal of the one-bit signal, and anti-phase amplifying
means for amplifying the other signal of the one-bit signal in the opposite phase to the one
signal. Switching amplification means for amplifying the first phase, a first low pass filter for
passing the low frequency component of the output signal of the positive phase amplification
means, and a second low pass filter for passing the low frequency component of the output
signal of the negative phase amplification means. The first output terminal includes an output of
the first low pass filter and an output of the second low pass filter as output terminals. The
second output terminal has an output of the positive phase amplifying means and an output of
the reverse phase amplifying means as output terminals, and the first power supply voltage is a
signal voltage when the signal is output from the first output terminal. The power supply voltage
is generated by a switching amplification means, and the second power supply voltage is a power
supply voltage for generating a signal voltage when the signal is outputted from the second
output terminal by the switching amplification means. I assume.
[0011]
An audio apparatus according to the present invention is characterized in that an earphone or a
headphone can be connected to the first output terminal and a speaker can be connected to the
second output terminal in order to solve the above-mentioned problems.
[0012]
The audio device according to the present invention is characterized in that, in order to solve the
above problems, a rechargeable battery can be incorporated, and the speaker is provided on a
charging stand for charging the rechargeable battery built in the audio device. I assume.
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[0013]
An audio device according to the present invention is characterized in that, when the audio
device is set on the charging stand, the power supply voltage is the second power supply voltage
in order to solve the above-mentioned problem.
[0014]
An audio device according to the present invention comprises a charging stand detection means
for detecting that the audio device is set on the charging stand, in order to solve the abovementioned problems, and the audio stand detects the charging stand detection means by the
charging stand detection means. The power supply voltage may be used as the second power
supply voltage when it is detected that the battery pack is set on the charging stand.
[0015]
In order to solve the above problems, the audio device according to the present invention does
not pass through the low-pass filter after being generated from the power supply and the first
output terminal that outputs a signal that has been generated from the power supply and then
passed through the low-pass filter. It is characterized by having two output terminals with the
2nd output terminal which outputs a signal.
[0016]
In order to solve the above problems, an audio device according to the present invention
converts 1-bit signal which converts an audio signal consisting of an analog signal or a digital
signal allocated and expressed by multiple bits into a 1-bit signal allocated by 1 bit. And onephase amplifying means for amplifying one signal of the one-bit signal, and anti-phase amplifying
means for amplifying the other signal of the one-bit signal in the opposite phase to the one
signal. Switching amplification means for amplifying the first phase, a first low pass filter for
passing the low frequency component of the output signal of the positive phase amplification
means, and a second low pass filter for passing the low frequency component of the output
signal of the negative phase amplification means. The first output terminal includes an output of
the first low pass filter and an output of the second low pass filter as output terminals. The
second output terminal is characterized in that the output terminal of the output section of the
output unit and the negative-phase amplification means of said positive phase amplification
means.
[0017]
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In order to solve the above-mentioned problems, an audio device according to the present
invention is to make a power supply voltage for generating a voltage of a signal output from the
first output terminal and the second output terminal variable using the power supply. It features.
[0018]
An audio system according to the present invention is characterized in that the audio device and
at least one of an earphone, a headphone, and a speaker are combined in order to solve the
above-mentioned problems.
[0019]
In order to solve the above problems, the audio system according to the present invention
includes a combination of the audio device capable of incorporating a rechargeable battery and a
charging stand for charging the rechargeable battery incorporated in the audio device. It
features.
[0020]
As described above, the audio device according to the present invention includes the two output
terminals of the first output terminal and the second output terminal, and the second power
supply voltage is made larger than the first power supply voltage. When driving a speaker whose
driving ability is insufficient only by itself, an amplifier and a dedicated power supply circuit are
not required, and the cost can be reduced.
In addition, even in the case of a portable audio device, it is possible to hear a desired sound from
a speaker.
[0021]
Further, as described above, the audio apparatus according to the present invention includes: 1bit signal conversion means, switching amplification means including positive phase
amplification means and reverse phase amplification means, a first low pass filter, and a second
low pass filter The first output terminal uses the output of the first low pass filter and the output
of the second low pass filter as output terminals, and the second output terminal provides the
output of the positive phase amplification means and the negative phase amplification The
output portion of the means is an output terminal, and the first power supply voltage is a power
supply voltage for generating a signal voltage when the signal is output from the first output
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terminal by the switching amplification means, and the second power supply voltage is It is a
power supply voltage for generating a signal voltage when the signal is output from the second
output terminal by the switching amplification means.
[0022]
As a result, when the speaker is driven, it is possible to reduce the cost by eliminating the need
for a dedicated amplifier and a dedicated power supply circuit separately by using a 1-bit signal
reproduction circuit.
[0023]
Further, as described above, the audio apparatus according to the present invention can connect
an earphone or a headphone to the first output terminal and a speaker to the second output
terminal.
[0024]
As a result, when listening to music with earphones or headphones, a sufficient output can be
obtained with the signal after passing through the LPF.
In addition, a speaker can obtain a sufficient output by raising its voltage by connecting it
directly instead of taking a signal after the LPF.
As a result, one audio device can use headphones or earphones and speakers without using an
amplifier.
[0025]
Further, as described above, the audio device according to the present invention can incorporate
a rechargeable battery, and the speaker is provided in a charging stand for charging the
rechargeable battery built in the audio device.
[0026]
As a result, there is an effect that it is possible to simply listen to music without taking up a space
for placing a speaker and occupying a large area on a desk or the like.
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[0027]
Further, as described above, in the audio device according to the present invention, when the
audio device is set in the charging stand, the power supply voltage is set to the second power
supply voltage.
[0028]
Therefore, when an audio device is connected to a speaker requiring an audio output larger than
that of a headphone or the like, a sufficient power supply is automatically supplied from the
charging stand, so that a high output sound can be sufficiently emitted from the speaker. Thus,
the user's operation is simplified.
[0029]
Further, as described above, the audio equipment according to the present invention uses the
power supply voltage as the second power supply voltage when it is detected by the charging
stand detection unit that the audio equipment is set on the charging stand.
[0030]
As a result, the connection of the speakers can be distinguished from the connection of the
headphones by the connection of the audio device to the charging stand, and the power supply
voltage for generating the signal voltage can be adjusted.
[0031]
Further, as described above, the audio device according to the present invention includes the two
output terminals of the first output terminal and the second output terminal.
[0032]
Thus, the power supply voltage for the second output terminal for generating the signal voltage
is distinguished from that for the first output terminal, and the cost is reduced because the
separate amplifier and the dedicated power supply circuit are not required when the speaker is
driven. The effect is to be an audio device suitable for the configuration that can be performed.
[0033]
Further, as described above, the audio apparatus according to the present invention includes: 1-
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bit signal conversion means, switching amplification means including positive phase
amplification means and reverse phase amplification means, first low pass filter, and second low
pass filter The first output terminal uses the output of the first low pass filter and the output of
the second low pass filter as output terminals, and the second output terminal provides the
output of the positive phase amplification means and the negative phase amplification Let the
output part of the means be an output terminal.
[0034]
As a result, it is possible to achieve an audio device suitable for a configuration that can reduce
costs without using a dedicated amplifier and a dedicated power supply circuit separately using a
1-bit signal reproduction circuit.
[0035]
In the audio device according to the present invention, as described above, the power supply
voltage is made variable by the power supply for generating the voltage of the signal output from
the first output terminal and the second output terminal.
[0036]
As a result, it is possible to obtain an audio device suitable to increase the power supply voltage
for the second output terminal separately from that for the first output terminal.
[0037]
Further, as described above, in the audio system according to the present invention, the audio
device and at least one of the earphone, the headphone, and the speaker are combined.
[0038]
As a result, it is possible to provide a system configuration suitable for using an audio device that
can achieve cost reduction by eliminating the need for a separate amplifier and a dedicated
power supply circuit when driving a speaker.
[0039]
Further, as described above, in the audio system according to the present invention, the audio
device capable of incorporating a rechargeable battery and a charging stand for charging the
rechargeable battery incorporated in the audio device are combined.
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[0040]
As a result, it is possible to provide a system configuration suitable for using an audio device that
can achieve cost reduction by eliminating the need for a separate amplifier and a dedicated
power supply circuit when driving a speaker.
[0041]
An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.
First, an embodiment of driving a headphone with a portable audio device will be described with
reference to FIG. 1, and next, an embodiment of driving a speaker with a portable audio device
will be described with reference to FIG. Explain the graph of.
[0042]
FIG. 1 shows a configuration of a portable audio device 100 as an audio device according to the
present embodiment, and a state in which the portable audio device 100 drives a headphone
701.
[0043]
First, the internal structure of the portable audio device 100 surrounded by a broken line in FIG.
1 will be described.
The portable audio device 100 is an audio device provided with a digital amplifier (class D
amplifier) for switching and amplifying an audio signal, and the Δ ブ ロ ッ ク block 101 (which
incorporates a Δ 変 換 conversion circuit not shown), a microcomputer It is called
"microcomputer".
201, upper gate drive 301, 302, lower gate drive 401, 402, output transistors 501 to 504, coils
505, 506, capacitors 507, 508, resistance 509, 510 of coils 505, 506, positive phase analog
output terminal A reverse phase analog output terminal 512, a positive phase digital output
terminal 513, a reverse phase digital output terminal 514, a power supply terminal 515, and a
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power supply / charging circuit 601 are provided.
The power supply / charging circuit 601 can incorporate a rechargeable battery.
Furthermore, the portable audio device 100 is combined with the headphones 701 and a
charging stand 800 described later to configure an audio system.
[0044]
Each will be described below.
[0045]
The ΔΣ block (1-bit signal conversion means) 101 includes a not-shown ΔΣ conversion circuit,
and a PDM signal as a series of binary signals from an analog signal or multi-bit digital signal
input to the Δ 入 力 conversion circuit or Create a PWM signal.
Further, the ΔΣ block 101 generates two series of 1-bit signals (positive phase signal and
negative phase signal) based on the generated binary signal (PDM signal, PWM signal).
The positive phase signal is output from the 1-bit positive phase output terminal 102, and the
negative phase signal is output from the 1 bit negative phase output terminal 103.
[0046]
The microcomputer 201 is provided to control the present audio system, and is always supplied
with power from the power supply / charging circuit 601.
The microcomputer and the ΔΔ block 101 are connected by a control signal line CL.
[0047]
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A 1-bit signal output from the 1-bit positive phase output terminal 102 is input to each input
terminal of the upper gate drive 301 and the lower gate drive 401.
The 1-bit signal output from the 1-bit reverse phase output terminal 103 is input to each input
terminal of the upper gate drive 302 and the lower gate drive 402.
The power supply / charging circuit 601 applies power supply voltages to the upper gate drives
301 and 302 and the lower gate drives 401 and 402, respectively, according to the control of the
microcomputer 201.
[0048]
The drains of the output transistors 501 and 502, which are N-channel MOS transistors, are
connected to the power supply terminal 515, respectively.
The source of the output transistor 501 is connected to the drain of the output transistor 503,
and the source of the output transistor 502 is connected to the drain of the output transistor
504.
The sources of the output transistors 503 and 504 are connected to the ground, respectively.
The configuration in which the output transistors 501 to 504 are connected as described above
is a full bridge circuit.
[0049]
The output of the upper gate drive 301 is input to the output transistor 501, the output of the
upper gate drive 302 is input to the output transistor 502, the output of the lower gate drive 401
is input to the output transistor 504, and the output of the lower gate drive 402 Is input to the
output transistor 503.
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The upper gate drives 301 and 302, the lower gate drives 401 and 402, and the output
transistors 501 to 504 constitute switching amplification means.
The upper gate drive 302, the lower gate drive 401, and the output transistors 502 and 504
constitute positive phase signal amplification means for switching and amplifying the positive
phase signal, and the upper gate drive 301, the lower gate drive 402, The output transistors 501
and 503 constitute anti-phase signal amplification means for switching and amplifying the antiphase signal.
[0050]
Two output lines are connected to a connection point of the output transistor 502 and the output
transistor 504.
First, a coil 505 is connected to one output line.
The other side of the coil 505 with respect to the output transistors 502 and 504 is connected to
the positive phase analog output terminal 511 via the resistance 509 of the coil 505.
Also, the positive phase digital output terminal 513 is connected to the other output line.
A capacitor 507 is connected between the load side of the coil 505 and the ground, and the coil
505 and the capacitor 507 constitute an LPF (low-pass filter) (hereinafter referred to as a first
LPF (first low-pass filter)).
[0051]
On the other hand, two output lines are also connected to the connection point of the output
transistor 501 and the output transistor 503.
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First, a coil 506 is connected to one output line.
The other side of the coil 506 with respect to the output transistors 501 and 503 is connected to
the negative phase analog output terminal 512 via the resistance 510 of the coil 506.
Further, the reverse phase digital output terminal 514 is connected to the other output line.
A capacitor 508 is connected between the load side of the coil 506 and the ground, and the coil
506 and the capacitor 508 constitute an LPF (low-pass filter) (hereinafter referred to as a second
LPF (second low-pass filter)) .
[0052]
The positive phase analog output terminal 511 is connected to the common mode output
terminal which is the output portion of the first LPF, and the negative phase analog output
terminal 512 is connected to the common mode output terminal which is the output portion of
the second LPF. It will be.
Furthermore, a headphone 701 is connected between the positive phase analog output terminal
511 and the negative phase analog output terminal 512.
As a result, the signal input to the headphone 701 is in the normal mode.
Thus, the positive phase analog output terminal 511 and the negative phase analog output
terminal 512 constitute a first output terminal.
[0053]
Further, the positive phase digital output terminal 513 is connected to a common mode output
terminal which is an output portion of a circuit composed of the output transistor 502 and the
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output transistor 504, and the negative phase digital output terminal 514 is an output It is
connected to a common mode output terminal which is an output portion of a circuit formed by
the transistor 501 and the output transistor 503.
Further, a speaker 801 is connected between the positive phase digital output terminal 513 and
the negative phase digital output terminal 514 as described later.
As a result, the signal input to the speaker 801 is in the normal mode.
Thus, the positive phase digital output terminal 513 and the negative phase digital output
terminal 514 constitute a second output terminal.
[0054]
The operation of the audio system configured as described above will be described.
[0055]
The ΔΣ block 101 generates a PDM signal or a PWM signal as one series of binary signals from
the input analog signal or multi-bit digital signal.
Further, the ΔΣ block 101 generates two series of 1-bit signals (positive phase signal and
negative phase signal) based on the generated binary signal (PDM signal, PWM signal).
Thereafter, the 1-bit digital signal generated by the ΔΣ block 101 is input to the upper gate
drives 301 and 302 and the lower gate drives 401 and 402 through the 1-bit positive phase
output terminal 102 and the 1-bit negative phase output terminal 103. . These signals are
converted by the upper gate drive 301, 302 and the lower gate drive 401, 402 into the
predetermined voltages necessary to operate the output transistors 501, 502, 503, 504 that
constitute the output full bridge circuit. Thus, the output transistors 501 to 504 perform
switching operation.
[0056]
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By this switching operation, an amplified 1-bit signal is obtained, which is a signal generated
from the power supply via the power supply terminal 515 and the ground. A power supply
voltage for obtaining this signal voltage when driving the headphone 701 is taken as a first
power supply voltage. Among the obtained signals, the signal obtained from the connection point
between the output transistor 502 and the output transistor 504 is passed through the first LPF
including the coil 505 and the capacitor 507 and obtained from the connection point between
the output transistor 501 and the output transistor 503. The signal passes through a second LPF
consisting of a coil 506 and a capacitor 508. A headphone 701 with a positive phase analog
output 511 terminal for outputting a positive phase analog signal which is a signal passing
through the first LPF, and a reverse phase analog output 512 terminal for outputting a reverse
phase analog signal which is a signal passing through the second LPF. Can be heard through the
headphones 701.
[0057]
Next, FIG. 2 will be described. FIG. 2 shows a state in which the speaker 801 is driven by the
portable audio device 100. In the following, only differences from FIG. 1 will be described.
[0058]
The internal structure of the portable audio device 100 from the ΔΣ block 101 to the power
supply and charging circuit 601 is the same as that shown in FIG. In FIG. 2, the portable audio
device 100 is connected to an external charging stand 800. The charging stand 800 incorporates
a charging / power supply circuit 901 and a speaker 801, supplies power to the portable audio
device 100, and charges a rechargeable battery incorporated in the portable audio device 100.
[0059]
The charging / power supply circuit 901 performs charging / power supply operation to the
power / charging circuit 601 in the portable audio device 100. The charging / power supply
operation is performed when the portable audio device 100 is set on the charging stand 800.
When outputting audio using the speaker 801, when the portable audio device 100 is placed on
the charging stand 800, the positive phase digital output terminal 513 and the negative phase
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digital output terminal 514 are connected to the speaker 801 by a connector not shown. It has
become so.
[0060]
Also, when the portable audio device 100 is set in the charging stand 800, if the charging stand
detection means (not shown) built in the portable audio device 100 detects that the charging
stand 800 is set, the power supply / charging circuit 601 The supply voltage of the power supply
terminal 515 is increased. That is, by the switching operation of output transistors 501 to 504,
the amplified 1-bit signal is generated from the power supply through power supply terminal
515 and the ground, but the power supply for obtaining this signal voltage when driving speaker
801 If the voltage is a second power supply voltage, the second power supply voltage is larger
than the first power supply voltage.
[0061]
Thus, when the portable audio device 100 is connected to the speaker 801, the portable audio
device 100 distinguishes the connection of the speaker 801 from the connection of the
headphone 701, adjusts the power supply voltage for generating the signal voltage, and Since a
sufficient power supply is automatically performed and the speaker 801 can emit a sound with
high output level sufficiently, the user's operation is simplified. The speaker 801 can be driven
even if the capacity is small only by the power supply / charging circuit 601 which is the internal
power supply and the output and power supply time is insufficient for driving the speaker 801.
[0062]
As described above, the positive phase digital output terminal 513 is connected to the connection
point of the output transistors 502 and 504, and the negative phase digital output terminal 514
is connected to the connection point of the output transistors 501 and 503. When the ΔΣ block
101 operates in this state, the ΔΣ block 101 to the output transistors 501 to 504 operate as
shown in FIG. The positive phase digital signal from the positive phase digital output terminal
513 and the negative phase digital signal from the negative phase digital output terminal 514
are applied to the speaker 801. Thereby, the speaker 801 is driven and the sound is reproduced
by the speaker 801.
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[0063]
Generally, a certain amount of output voltage is required to drive a speaker. Further, the coil
constituting the LPF has a DC resistance component as in the resistance component 509 and
510, and the output signal that has passed through the LPF can not make a speaker sound
sufficiently due to the voltage drop due to the resistance. In addition, even if the signal to the
speaker is not taken after the LPF, it is necessary to raise the power supply even if the signal is
directly connected, since the voltage required for the speaker is not satisfied.
[0064]
However, as described above, in this embodiment, as in the positive phase digital output terminal
513 and the negative phase digital output terminal 514, the signal is directly output without
passing through the LPF, and the power supply / charging circuit 601 Is to increase the supply
voltage of the power supply terminal 515. That is, the voltage applied to the power supply
terminal 515 is variable, and the voltage applied to the power supply terminal 515 is increased
when output signals are output from the positive phase digital output terminal 513 and the
negative phase digital output terminal 514. . Therefore, a voltage sufficient to drive the speaker
is output, and a sufficient volume can be maintained. Also, the direct output of the signal without
passing through the LPF means that it is not necessary to configure the coil with a thick wire in
order to reduce the direct current resistance contained in the coil configuring the LPF, and a
small component is used Convenient for portable devices. Therefore, the portable audio device
100 is provided with two types of output terminals for earphones or headphones and for
speakers.
[0065]
Further, in the configuration provided with the two types of output terminals as described above,
the voltage that can be generated and driven in the output bridge circuit and the power supply
circuit has an upper limit, and it is difficult to raise the voltage of the output path passing
through the LPF. In consideration of Attempting to raise the voltage upper limit will lead to an
increase in cost. For this reason, cost reduction can be achieved by using the LPF coil
accompanied by a voltage drop only when it is necessary as in the case of using headphones.
Furthermore, if only the speaker's dedicated output terminal is provided, the voltage is too high
when connecting headphones or earphones to this, the load on the headphones or earphones
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becomes large, and the headphone or earphone output circuit or power supply circuit There is a
risk of failure, but this can also be avoided.
[0066]
Thus, the portable audio device 100 connects the earphone or headphone 701 to the positive
phase analog output terminal 511 and the negative phase analog output terminal 512, and the
speaker 801 to the positive phase digital output terminal 513 and the negative phase digital
output terminal 514. It is possible. As a result, when listening to music with the earphone or the
headphone 701, a sufficient output can be obtained by the signal after passing through the LPF.
Further, the speaker 801 can obtain a sufficient output by raising its voltage by directly
connecting it after the LPF instead of taking a signal. As a result, one audio device can use
headphones or earphones and speakers without using an amplifier.
[0067]
In addition, since the speaker 801 is provided on the charging stand 800, it is possible to simply
listen to music without requiring a space for placing the speaker and occupying much space on a
desk or the like.
[0068]
FIG. 3 shows how speech is output from a pulse.
The pulse of FIG. 3 is obtained by subtracting the voltage between the negative phase digital
output terminal 514 and the ground from the voltage between the positive phase digital output
terminal 513 and the ground, and the maximum value is VCC and the minimum value is VEE. ing.
An audio waveform is extracted from this pulse as shown. Here, in general, the speaker can
operate for the output frequency up to about 20 kHz. On the other hand, the sampling frequency
of the 1-bit signal output from the ΔΣ block 101 of this embodiment is several hundreds kHz to
several MHz. Therefore, the speaker can not respond directly to the frequency component of the
pulse, but can respond only to the low frequency component contained therein. This performs
the same operation as the first LPF including the coil 505 and the capacitor 507 in FIG. 1 and the
second LPF including the coil 506 and the capacitor 508, and only an audio signal with a
frequency of about 20 kHz at maximum is output from the speaker 801.
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[0069]
As described above, according to the portable audio device 100 according to the present
embodiment, when driving a speaker whose driving ability is insufficient only with the internal
power supply, a separate amplifier is used by using a 1-bit signal reproduction circuit. Also, the
need for a dedicated power supply circuit is eliminated, and cost can be reduced. In particular,
there is a great advantage in being able to hear a desired sound from a speaker while being a
portable audio device.
[0070]
Also, an audio device comprising a first output terminal for outputting a signal generated from a
power supply and then passing through the LPF, and a second output terminal for outputting a
signal generated from the power supply and not passing through the LPF, The portable voltage
can be reduced by making the power supply voltage for the second output terminal generating
the signal voltage distinct from that for the first output terminal and eliminating the need for a
separate amplifier and dedicated power supply circuit when driving the speaker. It is an audio
device suitable for a configuration such as the audio device 100.
[0071]
Further, a 1-bit signal conversion means for converting an audio signal consisting of an analog
signal or a digital signal allocated and expressed by multiple bits into a 1-bit signal allocated by 1
bit, and amplifying one of the 1-bit signals Switching amplification means for amplifying the 1-bit
signal, comprising: positive-phase amplification means and reverse-phase amplification means for
amplifying the other signal of the 1-bit signal that is in anti-phase with the one signal; A first low
pass filter for passing low frequency components of the output signal, and a second low pass
filter for passing low frequency components of the output signal of the negative phase
amplification means, the first output terminal being the first low pass filter And an output of the
second low pass filter as an output terminal, the second output terminal being an output of the
positive phase amplification means, and The audio device using the output section of the reverse
phase amplification means as the output terminal can reduce the cost without using a dedicated
amplifier and a dedicated power supply circuit separately using a 1-bit signal reproduction
circuit. An audio device suitable for such a configuration.
[0072]
Also, an audio device that makes the power supply voltage variable for generating a voltage of a
signal output from the first output terminal and the second output terminal using the power
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supply is a second output terminal as in the portable audio device 100. An audio device suitable
for a configuration in which the power supply voltage of the circuit of FIG.
[0073]
Further, if an audio system in which the portable audio device 100 and at least one of the
earphone, the headphone 701, and the speaker 801 are combined is configured, a system
configuration suitable for using the portable audio device 100 is provided. be able to.
In particular, if the portable audio device 100 and the speaker 801 are combined, the speaker
801 is not accompanied by an amplifier and its dedicated power supply circuit as in the prior art,
which is convenient when the user assembles a system.
[0074]
In addition, if an audio system in which a portable audio device 100 capable of incorporating a
rechargeable battery and a charging stand 800 are combined is configured, a system
configuration suitable for using the portable audio device 100 can be provided.
[0075]
Further, as described above, the speaker 801 is provided in the charging stand 800, so that a
space for placing the speaker is unnecessary and music can be simply listened to without
occupying much space on a desk etc. This is especially true for portable audio devices such as
MD (minidisc) products.
Further, as a further application, there is a mobile phone which is an audio device in terms of
outputting voice, and by setting it on the charging stand 800 and sounding the speaker 801, it is
possible to make a (hand-free) call Become.
[0076]
It can be used for audio equipment and audio systems in general, and is particularly useful for
portable audio equipment and audio systems such as MD products and mobile phones.
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[0077]
It is a block diagram which shows the structure of the portable audio instrument which concerns
on one embodiment of this invention, an audio system, and the drive state of a headphone.
It is a block diagram which shows the structure of the portable audio instrument which concerns
on one Embodiment of this invention, an audio system, and the driving state of a speaker.
It is a graph which shows a mode that an audio | voice is output from a speaker by pulse input.
It is a block diagram which shows the state which is driving headphones by the conventional
portable audio instrument. It is a block diagram which shows the state which is driving the
external speaker in the state which charges the conventional portable audio instrument by a
charging stand.
Explanation of sign
[0078]
100 Portable audio equipment (audio equipment) 101 ΔΣ block (1 bit signal conversion means)
102 1 bit positive phase output terminal 103 1 bit reverse phase output terminal 301, 302
upper gate drive 401, 402 lower gate drive 501 to 504 output transistor 511 Positive Phase
Analog Output Terminal 512 Negative Phase Analog Output Terminal 513 Positive Phase Digital
Output Terminal 514 Negative Phase Digital Output Terminal 515 Power Supply Terminal 601
Power Supply and Charging Circuit 701 Headphone 800 Charging Base 801 Speaker 901
Charging and Power Supply Circuit
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