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DESCRIPTION JP2014027370

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DESCRIPTION JP2014027370
Abstract: To prevent an excessive volume output when replacing headphones and the like, and an
excessive volume output when shifting from the power-off to the power-on. A mute control
circuit (10) includes a switch (14) for detecting the insertion of headphones and a switch (12) for
detecting a volume position. When the insertion of the headphone is not detected, it shifts to the
mute state where the audio signal is not output, and when the insertion of the headphone is
detected and the volume position is not detected to the silent state or near the silent state The
state is maintained, and the mute state is released when it is detected that the silent state or the
vicinity of the silent state is set. [Selected figure] Figure 1
Audio device with mute function
[0001]
The present invention relates to audio devices, and more particularly to a mute function.
[0002]
Conventionally, in an audio apparatus provided with a headphone output, a mute function is
designed to operate so as not to output a click noise at power ON / OFF.
In addition, there is also proposed a function of limiting so that excessive volume is not output
when a headphone plug is inserted into a jack.
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[0003]
Patent Document 1 below describes that the audio output is automatically set to mute or low
level according to the removal of the headphone plug, and the volume is automatically set to zero
when the headphone plug is removed, It is described that when the headphones are inserted, the
volume control is performed manually from the volume zero.
[0004]
Patent Document 2 describes that the audio level is automatically muted in response to the
removal of the headphone plug, and then automatically returned to the normal audio level, and
after the audio level is muted, the volume by the user is reduced. It is described that the mute
state is maintained until the setting is made.
[0005]
JP-A-11-136789 JP-A-2002-010389
[0006]
By the way, due to the impedance and efficiency of the headphones, a large level difference may
occur even with the same output, and if the headphones are replaced while the volume is
increased, an excessive volume may be output.
According to Patent Document 1, it is possible to prevent excessive volume by automatically
setting the volume of the electronic volume to zero (electrically setting the signal output level to
zero) at the time of headphone extraction, but It can be a problem if.
Further, mute control at the time of power ON / OFF is not particularly described, and if the
power is turned from OFF to ON with the headphones inserted, an excessive volume may be
output depending on the setting status of the volume.
[0007]
On the other hand, in Patent Document 2, since the mute state is maintained until volume setting
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is performed, there is a problem that voice output can not be confirmed until volume setting is
completed.
Also, if the volume setting is incorrect, there is a problem that an excessive volume is output
when the mute is released.
[0008]
The above problems may occur not only when headphones are replaced but also when the input
source is switched.
[0009]
An object of the present invention is to provide an audio apparatus capable of preventing an
excessive volume output when replacing headphones and switching an input source, and also
preventing an excessive volume output when transitioning from power OFF to power ON. is
there.
[0010]
The audio apparatus having the mute function according to the present invention comprises a
first detection means for detecting the insertion of headphones, a second detection means for
detecting the volume position, and a power on state, and the insertion of the headphones by the
first detection means. When the first detection means detects that the insertion of the headphone
is detected, the second detection means sets the volume position to a silent state or near a silent
state. The mute state is maintained when it is not detected, and the insertion of the headphones is
detected by the first detection means, and the volume position is set to the silent state or near the
silent state by the second detection means Control means for canceling the muted state when it
detects that.
[0011]
Further, according to the present invention, the first detection means for detecting the switching
of the input source, the second detection means for detecting the volume position, and the power
ON state, wherein the switching of the input source is detected by the first detection means. In
this case, a transition is made to the mute state in which no audio signal is output, and the
switching of the input source is not detected by the first detection means, and the volume
position is set to the silent state or near silent state by the second detection means. And the first
detection means does not detect the switching of the input source, and the second detection
means sets the volume position to a silent state or near a silent state. It is characterized by
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comprising control means for canceling the mute state when it is detected.
[0012]
Further, according to the present invention, in the case where the first detection means for
detecting the insertion and removal of the headphones, the second detection means for detecting
the volume position, and the power ON state, the insertion and removal of the headphones are
not detected by the first detection means. It shifts to a mute state where no audio signal is
output, and it is detected that the first detection means detects the insertion and removal of
headphones, and the second detection means detects that the volume position is set to a silent
state or near a silent state. When not in use, the mute state is maintained, and the first detection
means detects insertion / removal of headphones, and the second detection means detects that
the volume position is set to a silent state or near a silent state And control means for releasing
the mute state.
[0013]
According to the present invention, when the headphones are replaced or the input source is
switched, the headphones are temporarily switched to the mute state when the headphones are
inserted and removed, and the mute state is maintained unless the volume position is set to the
silent state or near the silent state. Since the volume position is set to the silent state or near the
silent state and the mute state is released to enable audio output, it is possible to reliably prevent
unintended excessive audio output.
[0014]
It is a circuit block diagram of embodiment.
In embodiment, when headphones are inserted, it is state explanatory drawing in case a volume
is except-位置 position.
In embodiment, when headphones are inserted, it is state explanatory drawing in case a volume
is-位置 position.
In embodiment, it is state explanatory drawing at the time of extracting a headphone.
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It is a circuit block diagram of other embodiment.
It is a circuit block diagram of other embodiment.
[0015]
Hereinafter, embodiments of the present invention will be described based on the drawings.
[0016]
FIG. 1 shows a circuit configuration of the audio device in the present embodiment.
[0017]
The audio apparatus includes a mute (MUTE) control circuit 10, which controls mute on / off.
[0018]
The mute control circuit 10 includes a volume position detection switch 12 that detects the
volume position of the analog volume 13, a headphone detection switch 14 that detects that a
headphone plug is inserted into the headphone jack, an OR gate 16, and an AND gate 20. And a
power supply circuit 18.
The output of the mute control circuit 10, that is, the output of the AND gate 20 is supplied to
the mute switch 24 to control ON / OFF of the mute.
[0019]
The mute switch 24 is a switch for switching whether the output of the amplifier 22 for
amplifying an audio signal is output to the headphones 26 (mute OFF: mute release state) or the
output of the amplifier 22 is shut off (mute ON).
When the mute switch 24 is ON, the mute release state is established, and an audio signal is
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output to the headphones 26. When the mute switch 24 is OFF, the audio signal is not output to
the headphones 26 when the mute switch 24 is OFF.
[0020]
The volume position detection switch 12 is a switch for detecting the position of the analog
volume 13, and specifically, detects that the position of the analog volume 13 is at the -∞
(silence state) position.
When the position of the analog volume 13 is at the −∞ position, the detection switch is turned
off, inverted by the inverter, and the Hi signal is output.
When the position of the analog volume 13 is other than the −∞ position, the detection switch
is turned ON, inverted by the inverter, and outputs a Low signal. A detection signal from the
volume position detection switch 12 is supplied to the OR gate 16.
[0021]
The headphone detection switch 14 is a switch that detects that a headphone plug has been
inserted into the jack, and outputs a Hi signal when the headphone plug is inserted, and outputs
a Low signal otherwise. The detection signal from the headphone detection switch 14 is supplied
to the AND gate 20.
[0022]
The detection signal from the volume position detection switch 12 is supplied to one terminal of
the OR gate 16, and the output signal from the AND gate 20 is supplied to the other terminal.
The OR gate 16 calculates the logical sum of the two input signals and outputs it to the AND gate
20.
[0023]
The power supply circuit 18 includes an AC plug, a rectifier circuit, a power supply voltage
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detection circuit, a delay circuit, a power failure detection circuit, and an inverter.
[0024]
The power supply voltage detection circuit and the delay circuit detect that the power is turned
on, and secure a fixed time until the circuit is stabilized as a delay time to output a Hi signal.
Also, the power failure detection circuit and the inverter detect that the power is turned off and
output a low signal. In other words, it detects that the power is not turned off and outputs a Hi
signal. Two signals from the power supply circuit 18 (a signal for detecting that the power is
turned on and a signal for detecting that the power is not turned off) are supplied to the AND
gate 20.
[0025]
The AND gate 20 calculates the logical product of the four outputs of the output from the OR
gate 16, the output from the headphone detection switch 14 and the two outputs from the power
supply circuit 18, and supplies the calculation result to the mute switch 24. Control the mute on
/ off. The output of the AND gate 20 is Hi when all of the output from the OR gate 16, the output
from the headphone detection switch 14, and the output from the power supply circuit 18 are Hi.
In this case, the mute switch 24 is ON. Mute is released. On the other hand, when any of the
output from the OR gate 16, the output from the headphone detection switch 14, and the output
from the power supply circuit 18 is low, the output of the AND gate 20 becomes low. In this case,
the mute switch 24 It is turned off and muted.
[0026]
The output of the AND gate 20 is also supplied to one terminal of the OR gate 16 as described
above. Therefore, when the output of the AND gate 20 is Hi, the Hi signal is output from the OR
gate 16 even if the detection signal from the volume position detection switch 12 is Low. This
state is held until the output of the AND gate 20 becomes low.
[0027]
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Next, the operation of the mute control circuit 10 according to the present embodiment will be
specifically described.
[0028]
(1) Power-off state In the power-off state, the signal from the power supply circuit 18 is a low
signal, so the output of the AND gate 20 is low, the mute switch 24 is turned off and the mute
state is maintained (power off Since the state is a state where power is not supplied, it can be said
that all output states are Low).
[0029]
(2) A state in which the headphone plug is not inserted into the jack in the power-on state When
the power is turned on, the power supply circuit 18 outputs a Hi signal after a predetermined
delay time.
However, since a headphone plug is not inserted into the jack from the headphone detection
switch 14 and a low signal is output, the output of the AND gate 20 is low, the mute switch 24 is
turned off and the mute state is maintained.
[0030]
(3) A state in which the headphone plug is inserted into the jack while the power is on When the
power is turned on and the headphone plug is inserted into the jack, a Hi signal is output from
the headphone detection switch 14 (switched from Low to Hi).
Therefore, ON / OFF of mute is determined by the signal from the volume position detection
switch 12.
[0031]
That is, when the analog volume 13 is other than the −∞ position, for example, when the analog
volume position is at a fixed level position (any level position other than − 以外 position), the
volume position detection switch 12 outputs a low signal. Therefore, the output of the AND gate
20 is low, and even if the headphone plug is inserted into the jack, the mute switch 24 is turned
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off and the mute state is maintained.
[0032]
On the other hand, when the analog volume 13 is at the −∞ position, the Hi signal is outputted
from the volume position detection switch 12, so the output of the AND gate 20 becomes Hi, the
mute switch 24 is turned ON, and the mute is released.
However, even if the mute is released, since the analog volume 13 is at the -∞ position in this
state, no audio signal is immediately output. From this state, when the user operates the analog
volume 13 and raises it to a certain level, the Low signal is output from the volume position
detection switch 12, but the Hi signal of the output of the AND gate 20 is output to the other
terminal of the OR gate 16. As it is supplied, the output of the OR gate 16 is maintained at Hi,
and the output of the AND gate 20 is also maintained at Hi. Accordingly, with the mute switch 24
also kept ON, the mute release state is maintained, and an audio signal of the level set by the
analog volume 13 is output from the headphone 26.
[0033]
FIGS. 2 and 3 show the input / output state of the AND gate 20 and the state of the mute switch
24 when the headphone plug is inserted into the jack in the power ON state.
[0034]
FIG. 2 shows a state in which the position of the analog volume 13 is a position other than −∞.
Among the inputs of the AND gate 20, the signal from the volume position detection switch 12 is
a low signal (indicated by L in the figure), so the output of the AND gate 20 becomes low and the
mute switch 24 is turned off. Become. Therefore, even if the analog volume 13 is set to a
constant level, no audio signal is output.
[0035]
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FIG. 3 shows a state in which the user turns the analog volume 13 to the −∞ position. Among
the inputs of the AND gate 20, the signal from the volume position detection switch 12 also
becomes a Hi signal (indicated by H in the figure), so the output of the AND gate 20 becomes Hi
and the mute switch 24 is turned ON. Become. Therefore, when the user turns the analog volume
13 to set a certain level from this state, an audio signal amplified at that level is output.
[0036]
(4) In order to replace the headphones in the power ON state, the headphone plug is removed
from the jack and then reinserted. When the headphone plug is removed from the jack, the Low
signal is output from the headphone detection switch 14. The output becomes Low, and the mute
switch 24 is turned off to shift to the mute state.
[0037]
FIG. 4 shows the input / output state of the AND gate 20 and the state of the mute switch 24 in
this case.
Among the inputs of the AND gate 20, the signal from the headphone detection switch 14 is a
low signal (indicated by L in the figure), so the output of the AND gate 20 becomes low and the
mute switch 24 is turned off to be in the mute state . Therefore, even if the analog volume 13 is
set to a constant level, no audio signal is output.
[0038]
When the headphone plug is reinserted into the jack, the headphone detection switch 14 outputs
a Hi signal. Therefore, mute ON / OFF is determined by the signal from the volume position
detection switch 12 as in the case of (2).
[0039]
That is, when the analog volume 13 is not at the-以外 position, the volume position detection
switch 12 outputs a low signal, so the output of the AND gate 20 is low, and the mute switch is
used even if a headphone plug is inserted into the jack. 24 is turned off and the mute state is
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maintained (see FIG. 2). Therefore, even if the impedance of the headphones 26 before
replacement and the headphones 26 after replacement is different, it is possible to effectively
prevent the excessive volume from being output.
[0040]
On the other hand, when the analog volume 13 is at the −∞ position, the Hi signal is outputted
from the volume position detection switch 12, so the output of the AND gate 20 becomes Hi, the
mute switch 24 is turned ON, and the mute is released. When the user operates the analog
volume 13 and raises it to a certain level, an audio signal of the level set by the analog volume 13
is output from the headphone 26 (see FIG. 3).
[0041]
As described above, in the present embodiment, after the power of the audio apparatus is turned
on, the mute state is maintained until a predetermined time (delay time in the delay circuit)
elapses, and then the mute release can be performed. However, as long as the headphone 26 is
inserted into the jack and the analog volume 13 is not set to the -∞ position, the mute is
maintained, so the analog volume 13 is set to a certain level after the power is turned on. It is
possible to prevent an unexpected excessive volume from being output.
[0042]
Also, even if the headphone 26 is replaced with another headphone 26 having a different
impedance, the headphone 26 is automatically muted when the headphone 26 is pulled out, and
the analog volume 13 is set to the-位置 position even if another headphone 26 is inserted. Since
the muted state is maintained unless it is turned off, it is possible to prevent an excessive volume
from being output due to the difference in impedance.
[0043]
When replacing the headphones 26, a user who has become familiar with the audio device
temporarily turns the analog volume 13 to the-位置 position so as to be silent, then extracts the
headphones 20 and inserts another headphone 26, Although it is general to turn the analog
volume 13 later from the −∞ position to the desired position to set the desired level, the mute
control circuit 10 of this embodiment can be said to be consistent with such operation. .
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That is, for such a user, when replacing the headphone 26, the analog volume 13 is turned from
the -.infin. Position to a desired position and set to a desired level, so the mute state is canceled at
this timing, and the user feels uncomfortable You can enjoy the sound quality etc. with another
headphone 26 without remembering the.
[0044]
Of course, even for a user who is not familiar with the audio device, the mute state is maintained
even if the analog volume 13 remains at a certain level when replacing the headphones 26, so
that excessive volume is surely prevented.
[0045]
This embodiment is particularly effective in an environment where an unspecified number of
users can wear and watch various headphones.
[0046]
In the present embodiment, by supplying the output of the AND gate 20 to the LED, it is possible
to display mute ON / OFF in a visible manner by the LED.
For example, when the output of the AND gate 20 is low, the mute LED is lit to notify the user
that the mute state is in effect.
When the user changes the headphone 26 to another headphone 26 while setting the analog
volume 13 to a certain level, the mute LED lights up to notify the user that the mute state has
been entered.
When the user turns the analog volume 13 to the −∞ position, the mute LED is turned off to
notify the user that voice output is possible.
[0047]
As mentioned above, although embodiment of this invention was described, this invention is not
limited to this, A various change is possible.
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[0048]
For example, in the present embodiment, the mute state is released when the position of the
analog volume 13 is set to the − 位置 position, but the mute is not necessarily strictly set to the
vicinity of −∞ instead of the −∞ position. You may release the state.
Alternatively, the mute state may be canceled by detecting that the analog volume 13 has been
operated significantly toward at least the −∞ position or its vicinity. In short, even if the
impedance and the efficiency of the headphones 26 are different, the mute state may be canceled
using as a trigger that the level of the analog volume is set to a level that does not cause an
excessive volume.
[0049]
Moreover, although the mute at the time of replacement | exchange of the headphone 26 was
especially demonstrated in this embodiment, it can apply similarly, also when switching an input
source, for example, switching an input source from CD to PC. In this case, instead of the
headphone detection switch 14, a switch detection switch of an input source can be used.
[0050]
The configuration in this case is shown in FIG. The input source switching detection switch 15
interlocks with the switching of the input source, and outputs a Low signal to the AND gate 20 at
the timing when the switching occurs, and outputs a Hi signal to the AND gate 20 otherwise.
When switching of the input source occurs, the signal from the input source switching detection
switch 15 temporarily becomes a low signal, and the output of the AND gate 20 becomes low,
and the mute switch 24 is turned off to transit to the mute state once. . After that (when the input
source switches to a new source and switching is not detected), the signal from the volume
position detection switch 12 is a Low signal unless the analog volume 13 is set at or near the
−− position. Because it remains as it is, the mute state is maintained. As a result, even if the
input source is switched while the position of the analog volume 13 is at a constant level (any
level other than the −∞ position or its proximity position), excessive volume can be prevented.
Needless to say, muting by replacing headphones and switching input sources may be used.
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[0051]
Further, although the headphone amplifier has been described in the present embodiment, the
present invention is also applicable to an amplifier capable of speaker output. In the case of an
amplifier capable of speaker output, in the circuit shown in FIG. 1, when the headphone plug is
pulled out from the jack, the headphone detection switch 14 remains in the state of outputting a
Low signal. Or even if set in the vicinity, the mute is not canceled and the audio is not output
from the speaker. Therefore, as shown in FIG. 6, for example, a headphone output detection
signal is supplied to one input terminal of an EXOR gate (exclusive OR circuit), and a speaker
output detection signal is input to the other input of the EXOR gate via a delay circuit. Connect to
the terminal. The output signal of the EXOR gate is connected to the input terminal of the AND
gate 20. When the headphone plug is inserted into the jack, the headphone output detection
signal is Hi and the speaker output detection signal is Low, so the output of the EXOR gate is Hi.
In this state, when the headphone plug is pulled out from the jack, the headphone output
detection signal becomes Low and the speaker output detection signal becomes Hi, but the delay
circuit delays the input of the Hi signal which is the speaker output detection signal. During the
delay time of the circuit, the inputs of the EXOR gates are both low. Therefore, the output of the
EXOR gate temporarily becomes low, and the output of the AND gate 20 can be made low. When
the delay time elapses, the speaker output detection signal input to the EXOR gate becomes Hi
and the output of the EXOR gate becomes Hi, so it is possible to control mute ON / OFF by the
signal from the volume position detection switch 12 become. The same is true when a headphone
plug is inserted into the jack. That is, when the headphone plug is extracted from the jack, the
headphone output detection signal is Low and the speaker output detection signal is Hi, the
output of the EXOR gate is Hi. In this state, when the headphone plug is inserted into the jack,
the headphone output detection signal becomes Hi and the speaker output detection signal
becomes Low, but the delay circuit delays the input of the Low signal which is the speaker output
detection signal. During the delay time due to, both inputs of the EXOR gate are Hi. Therefore,
during the delay time, the output of the EXOR gate temporarily becomes low, and the output of
the AND gate 20 can be made low.
When the delay time elapses, the speaker output detection signal input to the EXOR gate
becomes Low and the output of the EXOR gate becomes Hi, so it is possible to control mute ON /
OFF by the signal from the volume position detection switch 12 become.
[0052]
The delay circuit may be provided not on the supply line side of the speaker output detection
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signal but on the supply line side of the headphone output detection signal.
[0053]
Alternatively, a change in the speaker output detection signal and / or the headphone output
detection signal may be detected, and a low-level one-shot pulse signal may be supplied to the
input terminal of the AND gate 20 by a monomultivibrator or the like.
[0054]
Further, in the present embodiment, mute control is realized by the circuit configuration shown
in FIG. 1 or FIG. 5, but detection of various switches and mute control can also be realized by a
microcomputer.
[0055]
10 mute (MUTE) control circuit, 12 volume position detection switches, 14 headphone detection
switches, 15 input source switching detection switches, 16 OR gates, 18 power circuits, 20 AND
gates, 22 amplifiers, 24 mute switches, 26 headphones.
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