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JP2009094684

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DESCRIPTION JP2009094684
An electronic device capable of preventing a drive stop caused by a drop in voltage is provided. A
capacitor (25), a current limiting circuit (19) and a current limiting circuit (20) are connected to a
power stage of a power amplifier (24). The CPU 21 monitors the voltage of the capacitor 25 and
performs gain correction of the power amplifier 24 according to the voltage value. In addition,
when the speaker has a plurality of channels, the playback mode such as stereo playback or
monaural playback is switched according to the voltage value. [Selected figure] Figure 5
Electronics
[0001]
The present invention relates to an electronic device capable of instantaneously large power
consumption with a small amount of power supply.
[0002]
2. Description of the Related Art Conventionally, portable USB devices are known that are driven
by bus power.
However, USB bus power can only supply a current of 100 mA (at most about 500 mA), and it is
general to connect an AC adapter to a USB device that consumes a large amount of current.
09-05-2019
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[0003]
Therefore, for example, Patent Document 1 discloses one that receives power supply from two
USB cables using a conversion cable of a DC connector and a USB connector. JP, 2005-141732, A
[0004]
However, the power supply method of Patent Document 1 is not used within the USB standard,
and can not guarantee stable operation. Further, in devices such as power amplifiers that require
a current of about several A instantaneously, the amount of supply is still insufficient. As
described above, when the amount of supply is insufficient, there is a problem that the voltage of
the power amplifier is lowered and the entire apparatus suddenly stops.
[0005]
Then, this invention aims at providing the electronic device which can prevent the driving stop
by a voltage drop.
[0006]
According to the electronic device of the present invention, a gain correction of the main drive
circuit is performed according to a voltage value of the main drive circuit driven by the power
supply input unit receiving power supply, the main drive circuit driven by the current supply
from the power supply input unit, and the main drive circuit. And a controller for performing the
control.
[0007]
In this configuration, gain correction is performed according to the voltage value of the main
drive circuit.
That is, when the voltage value is low, the gain is set small to reduce the power consumption.
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This prevents a sudden stop of the main drive circuit.
[0008]
In the electronic device according to the present invention, a power input unit receiving current,
a power amplifier driven by current supply from the power input unit, and an audio signal
amplified by the power amplifier are input to emit sound. And a control unit configured to
change a supply mode of an audio signal to the power amplifier and the speaker unit according
to a voltage value of the power amplifier.
[0009]
In this configuration, the supply mode of the audio signal is changed according to the voltage
value of the power amplifier.
For example, when the voltage drop is large, monaural reproduction (one-channel reproduction)
is performed, and when the voltage drop is small, stereo reproduction is performed.
[0010]
Further, the invention is characterized by further comprising a storage circuit connected to a
front stage of the main drive circuit, and the control section performs gain correction of the main
drive circuit according to a voltage value of the storage circuit. Do.
[0011]
In this configuration, a storage circuit (capacitor) is connected to the front stage of the main
drive circuit, and power is stored.
When the main drive circuit consumes power equal to or higher than the supply current value,
current is supplied from the storage circuit. Here, the control unit performs gain correction of the
main drive circuit according to the voltage value of the storage circuit. That is, when the voltage
value drops, the gain is set small to reduce the power consumption. This prevents a sudden stop
of the main drive circuit due to a voltage drop.
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[0012]
Further, according to the present invention, the main drive circuit is a power amplifier, and the
control unit corrects the gain of the power amplifier according to a drop in voltage value of the
storage circuit or the main drive circuit. It features.
[0013]
In this configuration, the gain of the power amplifier is corrected.
That is, when the storage circuit drops in voltage, the power consumption is reduced by lowering
the sound emission volume, and sudden stop is prevented.
[0014]
The electronic device according to the present invention further includes a storage circuit
connected to the power stage of the power amplifier, and the control unit is configured to output
an audio signal to the power amplifier and the speaker unit according to a voltage value of the
storage circuit. Changing the supply mode of
[0015]
In this configuration, the supply mode of the audio signal is changed according to the voltage
value of the storage circuit.
For example, when the voltage drop is large, monaural reproduction (one-channel reproduction)
is performed, and when the voltage drop is small, stereo reproduction is performed.
[0016]
Further, according to the present invention, the control unit performs phase control of the audio
signal supplied to the plurality of speaker units when the voltage value of the storage circuit or
the power amplifier is at or near the upper limit, A process of setting a virtual sound source in a
sound space is performed.
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[0017]
In this configuration, when the voltage value is at or near the upper limit (that is, the maximum
charge state), the phases of the audio signal are controlled using a plurality of speaker units, and
the reproduction is performed to set the virtual sound source.
[0018]
According to the present invention, it is possible to prevent the driving stop due to the voltage
drop.
[0019]
Hereinafter, the electronic device according to the present embodiment will be described.
The electronic device of this embodiment is a portable speaker device, and is driven by bus
power by USB connection, self power by AC adapter connection, or both of bus power and self
power.
[0020]
FIG. 1 is a block diagram showing a power supply circuit configuration of the speaker device
according to the present embodiment.
As shown in the figure, the speaker device 1 includes a USB power input circuit 11, an AC
adapter power input circuit 12, a regulator (LDO) 13, a switch (HSSW) 14, a switch (SW) 15, a
switch (SW) 16, DC A DC converter (DC-DC) 17, a regulator (LDO) 18, a current limiting circuit
19, a current limiting circuit 20, a CPU 21, a digital circuit 22, an analog circuit 23, a power
amplifier 24, and a capacitor 25 are provided.
[0021]
The CPU 21 is a control unit that generally controls the speaker device 1.
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The digital circuit 22 and the analog circuit 23 are circuits that perform various audio
processing. The audio signal processed by the digital circuit 22 and the analog circuit 23 is
amplified by the power amplifier 24 and emitted to the outside.
[0022]
The USB power supply input circuit 11 is an interface that receives power supply from an
information processing apparatus (host) such as a PC, and receives power supply of 100 mA or
500 mA. The speaker device 1 performs bus power driving by supplying a current input from the
USB power input circuit 11 to the CPU 21, the digital circuit 22, and the analog circuit 23. The
USB device receives power supply of 100 mA when connected to the host, can receive 500 mA of
power supply after negotiation, and receives 100 mA of power supply if negotiation can not be
performed.
[0023]
The AC adapter power input circuit 12 is an interface that receives power supply from the AC
adapter, and receives, for example, a power supply of about 700 mA. The speaker device 1
performs self-power drive by supplying the current input from the AC adapter power supply
input circuit 12 to the CPU 21, the digital circuit 22, and the analog circuit 23.
[0024]
The LDO 13 is turned on and off in conjunction with the power supply input, and is turned on
when power is supplied from the USB power supply input circuit 11 to stabilize the output
voltage to 3.3V. When power is supplied from the AC adapter power input circuit 12, the power
is turned off.
[0025]
The HSSW 14 is a switch circuit controlled by the CPU 21. The HSSW 14 is turned on when bus
power driving is performed, and turned off otherwise.
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[0026]
The SW 15 is a switch circuit controlled by the CPU 21 and is turned on when performing bus
power driving.
[0027]
The SW 16 is turned on when power is supplied from the AC adapter power input circuit 12.
[0028]
The DC-DC converter 17 transforms the voltage supplied to the digital circuit 22 and the CPU 21
from 5 V to 3.3 V.
[0029]
The LDO 18 is always on and stabilizes the supply voltage to the analog circuit 23 at 3.3V.
[0030]
The current limiting circuit 19 and the current limiting circuit 20 are circuits that limit the
amount of current supplied to the power amplifier 24 and the capacitor 25.
The current limiting circuit 19 limits the output current to 100 mA, and the current limiting
circuit 20 limits the output current to 150 mA.
[0031]
The capacitor 25 is an electric double layer capacitor having a very large capacitance (eg, several
tens of μF or more).
Since the capacitor 25 has a very large electrostatic capacity, the operation of the CPU 21 or the
like can not be performed if all the current supplied from the USB power supply input circuit 11
or the AC adapter power supply input circuit 12 is consumed for charging.
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Therefore, in order to protect various circuits of the speaker device, the current limiting circuit
19 and the current limiting circuit 20 are provided to limit the current.
[0032]
In this embodiment, since the voltage is stored in the capacitor 25, when the speaker device
emits noise that consumes a few watts instantaneously, power can be supplied from the capacitor
25 to the power amplifier 24. is there.
The speaker device 1 of the present embodiment responds to the form of power supply from the
USB power input circuit 11 and the AC adapter power input circuit 12 in order to perform stable
power supply while storing voltage in the large capacity capacitor 25. The LDO 13, HSSW 14,
SW 15, and SW 16 are switched on and off.
Also, if the power amplifier 24 continuously consumes power by continuously emitting sound,
the voltage of the capacitor 25 may drop and the voltage may fall below the drive limit value (for
example, 2.7 V or less). . Therefore, in the present embodiment, various operations are performed
to suppress the voltage drop.
[0033]
First, FIG. 2 is a diagram showing a state switching list. As shown in the figure, the speaker device
1 performs six state switching. First, in a state where there is no power supply from the USB
power input circuit 11 and the AC adapter power input circuit 12, that is, in a state where
nothing is connected to the speaker device 1, the CPU 21 is not driven and various switches
remain off. There is (state 1).
[0034]
When the speaker device 1 is connected to the host and a current of 100 mA is input from the
USB power supply input circuit 11, power is supplied to the CPU 21 via the LDO 13, and as a
result, the CPU 21 is activated (state 2). Here, the CPU 21 negotiates with the host. If negotiation
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can not be performed, the speaker device can not be driven, the state is switched to state 1 again,
and the power is turned off.
[0035]
If negotiation is established, the CPU 21 determines that the bus power can be driven by 500 mA
input, and sets the HSSW 14 and SW 15 to ON, and the current input from the USB power input
circuit 11 is converted to the digital circuit 22, analog circuit 23, And supply the current limit
circuit 19 (state 3). In addition, 5 V power is supplied to the front stage of the power amplifier 24
(+5 A).
[0036]
Here, the current limiting circuit 19 limits the output current to 100 mA and supplies it to the
power amplifier 24. Also, the capacitor 25 is charged by this current. When the voltage of the
capacitor 25 is boosted to about 2.7 V, sufficient power (current exceeding 100 mA) can be
supplied to the power amplifier 24 even in the case of bus power driving. In practice, driving
may be performed after boosting to about 3 to 3.5 V in consideration of a margin.
[0037]
That is, the power amplifier 24 receives a current of 100 mA from the current limiting circuit 19
and amplifies the audio signal, but depending on the amount of amplification, it may consume a
current of more than 100 mA. . Here, when the power amplifier 24 consumes current exceeding
100 mA, the voltage of the capacitor 25 drops. However, since a current of 100 mA is constantly
supplied from the current limiting circuit 19, charging is performed again when the current
consumption of the power amplifier 24 is reduced. As a result, the speaker device 1 can
instantaneously perform output of about several W even though the bus power is driven, and
stable driving can be performed.
[0038]
Next, when the speaker device 1 is not connected to the host and only the AC adapter is
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connected, a current of about 700 mA is input from the AC adapter power input circuit 12. In
this case, the SW 16 is turned on to supply power to the CPU 21. As a result, the CPU 21 is
activated (state 4). Note that the power supply line of the AC adapter power supply input circuit
12 is monitored by a detection circuit (not shown), and the switch SW16 is turned on when
current is supplied to the power supply line. It has become.
[0039]
The CPU 21 turns off the LDO 13, HSSW 14 and SW 15 after the start. As a result, the current
input from the AC adapter power supply input circuit 12 is supplied to the digital circuit 22, the
analog circuit 23, and the current limiting circuit 20. In addition, 5 V power is supplied to the
front stage of the power amplifier 24.
[0040]
Here, the current limiting circuit 20 limits the output current to 150 mA and supplies it to the
power amplifier 24. Also, the capacitor 25 is charged by this current. Similar to the above, when
the voltage of the capacitor 25 is boosted to about several volts, sufficient power can be supplied
to the power amplifier 24.
[0041]
In the self power drive, the power amplifier 24 receives a current of 150 mA from the current
limiting circuit 20 and amplifies the audio signal, but may consume a current of more than 150
mA depending on the amount of amplification. Make up a minute. Here, when the power
amplifier 24 consumes current exceeding 150 mA, the voltage of the capacitor 25 drops.
However, since a current of 150 mA is always supplied from the current limiting circuit 20,
charging is performed again when the current consumption of the power amplifier 24 decreases.
Thus, the speaker device 1 can perform more stable driving than the bus power driving.
[0042]
Next, when the speaker device 1 is connected to the host in the self-powered state, a current of
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100 mA is input from the USB power input circuit 11. In this case, the CPU 21 negotiates with
the host. If negotiation is not possible, the various switches perform self-power drive as they are
(state 5).
[0043]
When the negotiation is established, the CPU 21 turns on the HSSW 14 and supplies the current
input from the USB power input circuit 11 to the current limiting circuit 19 (state 6). As a result,
a current of 100 mA is supplied from the current limiting circuit 19 to the power amplifier 24,
and a current of 150 mA is supplied from the current limiting circuit 20. Therefore, a current of
250 mA is supplied to power amplifier 24 and capacitor 25.
[0044]
When the AC adapter is connected in the bus power driving state (state 3), the CPU 21 turns on
the SW 16 and turns off the LDOs 13 and SW 15 to switch to the above state 6.
[0045]
Next, FIG. 3 is a diagram showing a voltage change of the capacitor 25. As shown in FIG.
As shown in the figure, the capacitor 25 is charged with a voltage of 5 V from the USB power
supply input circuit 11 or the AC adapter power supply input circuit 12 and is charged up to 5 V
at maximum. When the power amplifier 24 does not consume power (or is driven at 100 mA or
150 mA or less), the voltage is kept at 5 V (voltage change 1).
[0046]
Here, when the power amplifier 24 consumes power, a current is supplied from the capacitor 25
and the voltage of the capacitor 25 drops (voltage change 2). When the sound emission of the
sound is stopped and the power consumption of the power amplifier 24 is exhausted, the
capacitor 25 is again supplied with current and charged (voltage change 3).
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[0047]
Since the power consumption increases as the amplification amount of the power amplifier 24
increases (as the volume of the emitted sound increases), the slope of the voltage drop of the
capacitor 25 increases, and the slope of the voltage drop decreases as the amplification amount
decreases. For example, if the voice is emitted at a volume smaller than that of the voltage
change 2 described above, the slope of the voltage drop becomes smaller (voltage change 4). On
the other hand, when the voice is not emitted, the amount of current supplied to the capacitor 25
does not change at 100 mA or 150 mA, and the slope of boosting does not change (voltage
change 5).
[0048]
If the voltage decreases without changing the power consumption, the current consumption
increases. Therefore, when the voltage becomes smaller than a predetermined value (for
example, 2.7 V), the current can not be supplied to the power amplifier 24 and the output of the
power amplifier 24 is reduced (Sound is not emitted). In fact, even if the output of the power
amplifier 24 is down, power is supplied to the CPU 21 from the USB power supply input circuit
11 or the AC adapter power supply input circuit 12, so the entire speaker device 1 does not go
down.
[0049]
In the present embodiment, the following processing is performed to prevent the output of the
power amplifier 24 from being down.
[0050]
(1) Gain Correction FIG. 4 is a diagram showing the concept of gain correction according to the
voltage of the capacitor 25. FIG. 5 is a block diagram showing the processing system of the
speaker device 1. As shown in FIG.
The speaker device 1 includes a signal processing circuit 200 and a speaker 100 (speaker 100A,
speaker 100B) as a processing system, and audio information input from the USB interface (I / F)
101 is processed as a digital audio signal. It is input to the circuit 200. The signal processing
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circuit 200 includes the digital circuit 22 and the analog circuit 23 described above, performs
level correction and phase control of the input digital audio signal, and outputs the result as an
analog audio signal to the power amplifier 24. The analog audio signal amplified by the power
amplifier 24 is emitted from the speaker 100. Although the speaker device 1 actually processes
audio signals of two channels and emits different sounds from the speakers 100A and 100B
(performs stereo reproduction), the explanation is simplified in FIG. Shows a processing system
of one channel.
[0051]
The signal processing circuit 200, the power amplifier 24, and the capacitor 25 are connected to
the CPU 21, and the CPU 21 controls the processing mode of the signal processing circuit 200
and the gain of the power amplifier 24. The voltage of the capacitor 25 is managed by the CPU
21. As shown in FIG. 4, when the voltage of the capacitor 25 is 4.5 to 5 V, the CPU 21 does not
perform gain correction (± 0 dB). Since the voltage of the capacitor 25 is sufficiently high, it is
emitted as it is with the gain specified by the power amplifier 24 without performing the gain
correction.
[0052]
When the voltage of the capacitor 25 is 4 to 4.5 V, the CPU 21 corrects the gain of the power
amplifier 24 by -3 dB. By performing the gain correction of -3 dB, the volume is reduced, and the
power consumption of the power amplifier 24 is reduced. Therefore, the slope of the voltage
drop is reduced. The CPU 21 performs -6 dB gain correction when the voltage of the capacitor
25 is 3.5 to 4 V, and performs -12 dB gain correction when the voltage of the capacitor 25 is 3 to
3.5 V. As the voltage value decreases, the amount of gain correction increases and the volume
decreases, so the slope of the voltage drop further decreases. Therefore, the voltage drop can be
suppressed. Also, when the voltage is 3 V or less, mute is performed to correct the power
consumption to zero. When the voltage is 3 V or less, the muting is continued until the voltage
recovers to a certain level (for example, 3.5 V). When muting is performed, the power
consumption becomes zero, so that the voltage value is restored immediately, but when the voice
is emitted, there is a possibility that it becomes 3 V or less again. For this reason, the operations
of mute, mute release and mute will be repeated. Therefore, muting is canceled at, for example,
3.5 V or more in consideration of a certain margin.
[0053]
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As described above, since the gain correction of the power amplifier 24 is performed according
to the voltage value of the capacitor 25, the output reduction of the power amplifier 24 can be
prevented.
[0054]
(2) Switching of Reproduction Mode Next, switching of the reproduction mode will be described.
When the speaker device 1 has a two-channel speaker unit as shown in FIG. 5, switching of the
reproduction mode is to perform stereo reproduction, monaural reproduction (one-channel
reproduction), or two speaker units. This is an operation of controlling the phase of the audio
signal to switch whether to perform reproduction for setting a virtual sound source.
[0055]
That is, when the voltage drop of the capacitor 25 is small, the CPU 21 sets the phase control in
the signal processing circuit 200 to perform reproduction for setting the virtual sound source.
Further, when the voltage drops to some extent, the CPU 21 sets the signal processing circuit
200 not to perform phase control, and switches to normal stereo reproduction. When the voltage
drops further, the audio signal supply to one of the speakers is shut off (or one of the channels is
muted), and an operation to switch to monaural reproduction is performed. When setting a
virtual sound source by phase control, a gain of about twice is necessary to secure the same
sound pressure as normal stereo reproduction. Therefore, the slope of the voltage drop is the
largest. On the other hand, in the case of monaural reproduction, since the speaker drive power
for one channel is sufficient, the slope of the voltage drop is the smallest. Therefore, the abovedescribed reproduction mode is switched according to the voltage value to prevent the output of
the power amplifier 24 from being down.
[0056]
Further, the reproduction mode may be switched according to the form of power supply from the
USB power input circuit 11 and the AC adapter power input circuit 12. For example, monaural
reproduction is performed when bus power drive is performed, stereo reproduction is performed
when self power drive is performed, and reproduction in which a virtual sound source is set is
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performed when driving by both bus power and self power.
[0057]
Note that the reproduction mode may be switched while performing gain correction.
[0058]
Although the speaker device is shown as the electronic device in the present embodiment, the
present invention can be applied to any device as long as it performs bus power drive by USB
connection and self power drive by an AC adapter.
[0059]
In the present embodiment, an example is shown in which the current supply mode is switched
between the bus power drive and the self power drive. However, this configuration is not
essential, and a general current supply is performed (the function of switching the current supply
is not provided. It is applicable also to a usual apparatus.
For example, in the case of an apparatus which has a battery and operates only with the battery,
the power supply voltage decreases with the lapse of use time.
If the power supply voltage decreases, the power amplifier output will saturate at a smaller signal
level, or the driving will stop, but by applying the technology disclosed in the present
embodiment, longer time use is also possible. Become.
[0060]
In the present embodiment, although the gain correction and the regeneration mode are
switched according to the voltage value of the capacitor, the gain correction and the regeneration
mode may be switched according to the voltage value of the power amplifier.
[0061]
It is a block diagram which shows the power supply circuit structure of the speaker apparatus
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which concerns on this embodiment.
It is a figure showing a state change list. FIG. 6 is a diagram showing a voltage change of a
capacitor 25. FIG. 6 is a diagram showing the concept of gain control according to the voltage of
a capacitor 25. FIG. 2 is a block diagram showing a processing system of the speaker device 1;
Explanation of sign
[0062]
1-Speaker device 11-USB power supply input circuit 12-AC adapter power supply input circuit
13-regulator (LDO) 14-switch (HSSW) 15-switch (SW) 16-switch (SW) 17-DC-DC converter (DCDC) 18-regulator (LDO) 19-current limiting circuit 20-current limiting circuit 21-CPU 22-digital
circuit 23-analog circuit 24-power amplifier 25-capacitor
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