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JP2003304124

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DESCRIPTION JP2003304124
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
audio amplifier capable of connecting a plurality of types of external loads to one output
connector, and a notebook personal computer incorporating the audio amplifier as described
above.
[0002]
2. Description of the Related Art In recent years, even notebook personal computers that are
required to be miniaturized are required to be able to connect various multimedia devices. For
this purpose, a plurality of notebook personal computers are connected as external loads. In
many cases, one output connector is shared for different types of devices. That is, in the case of a
notebook personal computer, since the computer main body is required to be miniaturized, the
space for arranging the output connector is small, and only one output connector is provided
where the plurality of output connectors should be arranged individually. In many cases, this is
shared by multiple types of external devices. For example, an audio signal output from an audio
amplifier is output from one output connector that doubles as a headphone output connector and
a line output connector.
[0003]
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1
When the headphone output connector and the line output connector are commonly used in a
small volume audio amplifier, whether it is built in a computer or not, in general, an amplifier
that outputs an audio signal to the output connector The output is provided via a DC blocking
capacitor. The reason is that the average DC voltage in the output signal of the audio amplifier,
that is, the operation reference voltage may be different from the operation reference voltage of
the input circuit of the external load connected to the output connector. The amplifier
corresponds to, for example, an output stage of a headphone amplifier capable of driving a
headphone.
[0004]
FIG. 4 is a block diagram illustrating the main part of a conventional audio amplifier. In the audio
amplifier 60 shown in FIG. 4, reference numeral 15 denotes an amplifier operated with a
unipolar power source, and the output thereof is given to the output connector 23 through a
capacitor 17 for interrupting a DC component and a resistance element 21. The resistance
element 21 is a protective resistance for preventing the amplifier 15 from being broken when the
output side of the output connector 23 is shorted to the return side. The output connector 23 has
an output-side contact, a return-side contact, and a plug insertion / removal detection contact.
The return-side contact is connected to a ground line to which the unipolar power supply is
connected. An external load 50 is connected to the output connector 23 by a plug. The external
load 50 is, for example, a headphone with low impedance, or an input circuit of another audio
device with high input impedance.
[0005]
Assuming that the amplifier 15 in the audio amplifier 60 is driven by the positive / negative
ambipolar power supply, it is easy to set the operation reference voltage in the output signal of
the amplifier to 0 volt (ground level). However, the amplifier 15 is a circuit configuration driven
by a unipolar power supply, and is configured of, for example, a SEPP circuit (Single Ended PushPull Circuit). The operation reference voltage in the output signal of the amplifier 15 is
approximately one half of the power supply voltage Vcc. Therefore, a capacitor 17 for DC cutting
is disposed between the output line P of the amplifier 15 and the output connector 23.
[0006]
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2
As for the capacity of the capacitor 17, in consideration of the connection of low impedance
headphones to the output connector 23, a large capacity capacitor of, for example, about 100
μF is required. However, a large-capacity capacitor has a large volume, which is an obstacle to
miniaturizing a notebook personal computer, or the cut-off frequency of an audio signal to be
given to headphones is inevitable to keep the capacity of the capacitor small. There was a
problem that it became high. Furthermore, when an electric field capacitor that can easily obtain
a large capacity is used as the capacitor 17, there is also a problem that the audio signal given to
the headphone is likely to be distorted.
[0007]
On the other hand, in a laptop personal computer incorporating an audio amplifier in which a
plurality of types of external loads can be connected to one output connector 23 as described
above, the operator determines the type of the external load connected to the output connector
23 And had to set up a personal computer according to the type of external load. The contents to
be set are, for example, the gain of an audio amplifier, the frequency characteristic, and a driver
of an application for reproducing media including an audio signal. For example, in an application
having a surround function, it is necessary to change an algorithm for computing a surround
signal depending on whether the device that outputs surround sound is a headphone, an external
monitor speaker, or a computer built-in speaker. The computer operator needs to determine what
is connected as an external load, and manually set an appropriate driver or program for the
connected device.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve the abovementioned problems, and a first object of the present invention is to allow connection of a
plurality of types of audio devices via one output connector. Audio amplifier, in which the volume
of a large capacity capacitor interposed between the amplifier and the output connector is
reduced, and the second object is that, in a notebook personal computer incorporating an audio
amplifier, a plurality of them are connected via one output connector. It is possible to connect
various types of audio devices and to easily set up a computer according to the connected audio
devices.
[0009]
SUMMARY OF THE INVENTION In order to achieve the above object, the audio amplifier and the
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3
notebook personal computer of the present invention are configured as follows.
That is, in the audio amplifier according to the first aspect of the invention, an amplifier, an
output connector for connecting an external load, a capacitor for supplying an output of the
amplifier to the output connector, and an impedance of an external load connected to the output
connector are predetermined. Impedance determining means for determining whether or not the
value is less than a value, a switch for shorting both ends of the capacitor when the impedance of
the external load is less than a predetermined value, and the impedance of the external load is
less than the predetermined value And a means for applying a DC bias voltage to the return side
of the output connector.
[0010]
An audio amplifier according to a second aspect of the invention is the audio amplifier according
to the first aspect, wherein an average voltage of the output signal of the amplifier and the DC
bias voltage are approximately half of a voltage of the unipolar power source. It is.
[0011]
An audio amplifier according to a third aspect of the invention is the audio amplifier according to
the first aspect or the second aspect, wherein a resistance element is connected in series to the
capacitor between the amplifier and the output connector, and the impedance determination
means is The present invention is an audio amplifier in which the impedance of the external load
is measured using the voltage applied to the resistance element and the voltage applied to the
external load.
[0012]
A notebook personal computer according to a fourth aspect of the present invention is a
notebook personal computer incorporating an audio amplifier, wherein the audio amplifier
includes an amplifier, an output connector for external load connection, and an output of the
amplifier as the output connector. External load determining means for determining the type of
the external load according to the capacitor to be supplied and the impedance of the external
load connected to the output connector, and the type of the external load determined by the
external load determining means According to another aspect of the present invention, there is
provided a notebook personal computer comprising: a switch short-circuiting terminals of a
capacitor; and means for applying a DC bias voltage to the return side of the output connector
according to the type of the determined external load.
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[0013]
A notebook personal computer according to a fifth invention is the notebook personal computer
according to the fourth invention, wherein both ends of the capacitor are shorted when the
impedance of the external load measured by the external load judging means is equal to or less
than a predetermined value. A notebook type personal computer comprising a switch and means
for applying a DC bias voltage to the return side of the output connector when the impedance of
the external load is less than the predetermined value.
[0014]
A notebook personal computer according to a sixth invention is the notebook personal computer
according to the fifth invention, wherein a resistance element is connected in series to the
capacitor between the amplifier and the output connector, and is applied to the resistance
element. The notebook personal computer is configured to measure the impedance of the
external load using the amplitude of the audio signal and the amplitude of the audio signal
applied to the external load.
[0015]
A notebook personal computer according to a seventh invention is the notebook personal
computer according to any of the fourth invention to the sixth invention, wherein an output
signal of the audio amplifier is output using the determination result of the external load
determining means. It is a notebook personal computer that recognizes a sound output device to
be converted into sound, and switches a part of a program related to application software or an
operation system that handles an audio signal according to the recognized sound output device.
[0016]
An eighth aspect of the present invention is the notebook personal computer according to the
seventh aspect of the present invention, further comprising display means having a display
screen, wherein the display for selecting or confirming one sound output device is displayed.
According to another aspect of the present invention, there is provided a notebook personal
computer wherein a display mode of the display means is changed according to a recognized
sound output device.
[0017]
A notebook personal computer according to a ninth aspect of the present invention is the
notebook personal computer according to the eighth aspect of the present invention, wherein the
display means is used as a candidate for a sound output device when selecting or confirming one
sound output device. The notebook personal computer is configured to display a list of the two
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sound output devices and to highlight or blink the recognized one sound output device during
the list display.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION An audio amplifier according to the present
invention comprises an amplifier, an output connector to which a plurality of types of external
loads can be connected, a capacitor for interrupting a direct current component of the output of
the amplifier and supplying it to the output connector. And an impedance determination means
for determining whether or not the impedance of the external load connected to the output
connector is less than or equal to a predetermined value, and when the impedance of the
connected external load is less than or equal to a predetermined predetermined value The switch
is short-circuited at both ends, and a DC bias voltage of, for example, 1/2 of the voltage Vcc of
the unipolar power supply is applied to the return side of the output connector.
The amplifier is an amplifier that outputs an audio signal to the output connector, and
corresponds to, for example, an output stage of a headphone amplifier capable of driving low
impedance headphones.
[0019]
According to the configuration of the present invention described above, when the impedance of
the connected external load is high, the output of the amplifier is applied to the output connector
via a capacitor, and when the impedance of the connected external load is low, the output of the
amplifier is a capacitor Provided to the output connector without passing through.
Therefore, when the load connected to the output connector is an input circuit of an external
audio amplifier, an audio signal is given to the output connector through a capacitor, and the
load connected to the output connector is headphones While an audio signal is supplied to the
output connector without passing through a capacitor, a DC bias voltage is supplied to the return
side of the output connector, and no DC voltage is applied between the terminals of the
headphone.
In addition, since the capacitor is used substantially only when the impedance of the external
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load is large, the cutoff frequency of the audio signal given to the headphone can be sufficiently
lowered even if the capacity of the capacitor is reduced, and the audio The effect is that the
amplifier can be miniaturized.
[0020]
A notebook personal computer according to the present invention is a computer incorporating an
audio amplifier provided with one output connector to which a plurality of types of external
loads can be connected as described above, and is connected to the output connector. A sound
output device comprising external load determination means for determining the type of the
external load according to the impedance of the external load, and converting the output signal
of the audio amplifier into sound using the determination result of the external load
determination means recognize.
Then, according to the recognized sound output device, hardware is set, and setting of
application software and / or an operation system (OS) that handles audio signals is performed.
[0021]
As in the case of the audio amplifier of the present invention described above, when it is
determined that the load connected to the output connector is a headphone, an audio signal is
given to the output connector without passing through a capacitor, and A DC bias voltage is
applied to the return side, and no DC voltage is applied between the headphone terminals.
In addition, since the capacitor between the amplifier and the output connector is substantially
used only when the impedance of the external load is large, the capacity of the capacitor can be
reduced and the computer can be miniaturized, and the computer hardware When setting the
software, the setting according to the sound output device can be made almost automatically and
easily, and when setting the application software and / or the operating system (OS) of the
computer, an application that handles audio signals For the software and / or OS, it is possible to
set the optimum driver or program according to the sound output device almost automatically.
[0022]
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Hereinafter, an embodiment of the present invention will be described with reference to the
drawings.
FIG. 1 is a block diagram showing an embodiment of the audio amplifier of the present invention,
and only one channel is shown to simplify the description.
In the audio amplifier 10 shown in FIG. 1, reference numeral 15 denotes an amplifier operated
by a unipolar power source, and the output thereof is given to the output connector 23 through a
capacitor 17 for blocking a direct current component and a resistance element 21.
The output connector 23 has at least an output side contact piece, a return side contact piece,
and a plug insertion and removal detection contact piece. An external load 50 is connected to the
output connector 23 by a plug. One of a plurality of types of audio devices can be connected as
the external load 50. For example, headphones of low impedance or input circuits of other audio
devices with high input impedance are connected.
[0023]
The amplifier 15 in the audio amplifier 10 is, for example, an SEPP circuit driven by a positive
voltage unipolar power supply, and the operation reference voltage in the output signal of the
amplifier 15 is approximately half the power supply voltage Vcc, and the average DC voltage is
also approximately Vcc. It is / 2. The impedance determination means 33 measures the
impedance of the external load 50, and determines whether the value of the obtained impedance
is less than or equal to a predetermined value. Then, the switch 19 and the switch 29 are
controlled in accordance with the determination result. The resistance value of the resistance
element 21 is a known value, and the impedance of the external load 50 is measured using the
voltage across the resistance element 21 and the voltage across the external load 50 in the
measurement of the impedance in the impedance determination means 33. . Therefore, the
voltage at both ends of the resistance element 21 and the voltage at both ends of the external
load 50 are given to the impedance determination means 33. Further, the output of the external
load connection detection unit 40 is given to the impedance determination unit 33 so that the
operation of the impedance determination unit 33 is started when the external load 50 is
attached and detached. Specifically, the external load connection detection means 40 includes a
jack sense circuit for detecting insertion and removal of a plug to the output connector 23.
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[0024]
The switch 29 is a switch for switching the DC voltage on the return side of the output connector
23, and is controlled by the output of the impedance determination means 33. That is, the
common terminal k of the switch 29 is connected to the return side of the output connector 23,
and the terminal k is switched to the terminal j or the terminal i according to the output of the
impedance determination means 33. The terminal j is connected to the ground side line of the
power supply of the amplifier 15, and the terminal i is connected to the ground side line of the
power supply of the amplifier 15 via the bias DC power supply 31. The output of the jack sense
circuit 40 is given to the impedance judging means 33, and when the plug is inserted into the
output connector 23, the impedance judging means 33 starts the impedance measurement of the
external load 50.
[0025]
The operation of the audio amplifier 10 will be described below. When plug insertion and
removal is detected by the external load connection detection means (jack sense circuit) 40, a
sine wave signal for impedance measurement is input to the amplifier 15. The sine wave signal
output from the amplifier 15 is applied to the resistance element 21 and the external load 50 via
the capacitor 17. Assuming that the impedance of the resistance element 21 is z21, the
impedance of the external load 50 is z50, the amplitude of the sine wave signal applied to the
resistance element 21 is e21, and the amplitude of the sine wave signal applied to the external
load 50 is e50, The impedance z50 of the load 50 is calculated as z50 = Z21 × e50 / e21.
[0026]
The impedance of the headphones connected to the output connector 23 is about 16Ω to 150Ω,
and the impedance of the input circuit of the audio device other than the headphones connected
to the output connector 23 is 10 kΩ or more. From this, the impedance determination means 33
outputs L level when the measured value of z50 is 2 kΩ or less, and outputs H level when it is
larger than 2 kΩ. When the output of the impedance determination means 33 is at H level, the
switch 19 opens between the d and e terminals, and the switch 29 connects the terminal k to the
terminal j side.
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[0027]
On the other hand, when the output of the impedance determination means 33 is L level, the
switch 19 connects between the d and e terminals, and the switch 29 connects the terminal k to
the terminal i side. Therefore, when the audio signal to be reproduced is output from the
amplifier 15 after setting the switch 19 and the switch 29 in this manner, the audio signal is
directly output to the output side of the output connector 23 without passing through the
capacitor 17. A DC bias voltage is applied to the return side of the output connector 23 by the
bias DC power supply 31. The bias voltage is made equal to the average voltage of the output
signal of the amplifier 15, that is, the operation reference voltage. In order to maximize the
dynamic range of the amplifier 15, the average voltage of the output signal of the amplifier 15,
that is, the operation reference voltage is 1/2 of the power supply voltage Vcc, and the voltage of
the bias DC power supply 31 is also Vcc / 2. Is preferred.
[0028]
The switch 19 opens the terminals d and e and uses the capacitor 17 substantially only when the
external load 50 is not connected or when the impedance of the external load 50 is larger than a
predetermined value. Therefore, even if the capacitance of the capacitor 17 is reduced, the cutoff
frequency of the audio signal output from the output connector 23 can be sufficiently lowered.
Further, even if the capacitor 17 is not used, a direct current voltage is not superimposed on the
headphone connected to the output connector 23 and the output of the amplifier 15 is given
without passing through the electric field capacitor, thereby outputting a sound with less
distortion. be able to.
[0029]
FIG. 2 is a block diagram showing an audio output unit in the notebook personal computer of the
present invention, and only one channel is shown to simplify the description. In FIG. 2, the
elements having the same functions and the same functions as those of the audio amplifier
shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is
omitted. The notebook personal computer 20 shown in FIG. 2 incorporates an audio amplifier,
and the output of the amplifier 15 of the audio amplifier is given to the output connector 23
through the capacitor 17 and the resistance element 21. The amplifier 15 is formed of, for
example, SEPP, and is driven by a unipolar power supply of voltage Vcc. In order to enlarge the
dynamic range of the audio signal output from the amplifier 15, it is preferable to set the average
09-05-2019
10
voltage (operating reference voltage) in the output signal of the amplifier 15 to Vcc / 2.
[0030]
The output connector 23 is composed of an output contact piece f, a return contact piece g, and a
plug insertion and removal detection contact piece h. The plug insertion / removal contact h is
connected to the power supply via a pull-up resistor 25. Assuming that the voltage of the DC
power supply 31 for bias is Vcc / 2, the voltage of the plug insertion detection contact h is at the
ground level when the terminal k and the terminal j of the switch 29 are connected, and the
terminal k and the terminal i When and are connected, it is Vcc / 2. Then, when a plug is inserted
into the output connector 23 to connect an external load, the voltage of the plug insertion
detection contact h rises to Vcc by the separation of the plug insertion detection contact h and
the return contact g. , It is detected that the plug has been inserted. The voltage of the plug
insertion detection contact h is given to the jack sense circuit 40.
[0031]
The switch 11, the external load determination means 33b, and the switch 45 are controlled by
the output of the jack sense circuit 40. The external load determination means 33b measures the
impedance of the external load connected to the output connector 23 to determine the type of
the external load, and recognizes the sound output device that outputs sound using the output of
the jack sense circuit 40, The result is given to the MPU 35. The external load determination
means 33b performs the above-described process not only when the OS is started up or during
polling, but also when the jack sense circuit 40 detects that the plug is attached or removed.
[0032]
Connected to the MPU 35 are a keyboard 34 as an input means, a hard disk drive 36 for storing
an OS and application software, and a display means 37. The display means 37 has its display
content controlled by the MPU 35, and displays necessary information on the display screen
according to the operation content of the operator or the setting content of the computer. The
MPU 35 determines the external load when the OS starts up or during polling, or when the jack
sense circuit 40 detects that the plug is attached or detached, and determines a sound output
device (output destination device) such as a speaker or a headphone. Processing is performed. In
this case, the MPU 35 is recognized according to the output of the external load judging means
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33b or based on the connected external load in order to make it easy for the operator of the
computer to select or confirm the sound output device. Depending on the sound output device,
the display mode and the display content on the display means 37 are changed.
[0033]
The switch 11 is a switch for switching a signal input to the amplifier 15. The common terminal c
is connected to the input line of the amplifier 15, and a sine wave signal is given from the
oscillator 13 to the terminal b. Further, an audio signal to be reproduced is given to the terminal
a. In the switch 11, the terminal c and the terminal a are connected except when the setting
relating to the audio amplifier is performed, but when the setting relating to the audio amplifier
is performed, the terminal c is connected to the terminal b.
[0034]
When plug insertion / extraction at the output connector 23 is detected by the jack sense circuit
40, an external load attachment / detachment signal is given to the switch 11, the external load
determination means 33b, and the switch 45 as the external load attachment / detachment
signal. . The notebook personal computer 20 switches the terminal c connected to the terminal c
of the switch 11 from a to b at the time of starting or polling, or when the external load
attachment / detachment signal indicates connection of an external load, and outputs The
impedance of the external load connected to the connector 23 is measured to determine the type
of the external load, and based on the determination result, the sound output device that outputs
the sound of the audio signal is recognized. Furthermore, based on the recognition result, the
driver or program of application software that handles audio signals is switched to one that is
most suitable for the sound output device that recognizes the program.
[0035]
The output of the amplifier 15 is also given to the speaker driving power amplifier 47 and the
switch 45 through the capacitor 41 and the resistor 43. The switch 45 is controlled by the
output of the jack sense circuit 40. When the plug is not inserted into the output connector 23,
the switch 45 is closed to mute the sound output from the computer built-in speaker 51.
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[0036]
The operation of the notebook personal computer 20 shown in FIG. 2 will be described below. In
the notebook personal computer 20, when the impedance of the external load connected to the
output connector 23 is higher than a predetermined value, the type of external load is
determined to be the input circuit of the external audio amplifier, and the sound output device is
externalized. Recognized as a monitor speaker. In this case, the switch 19 is opened, the switch
45 is closed, and the terminal k of the switch 29 is connected to the terminal j side.
[0037]
On the other hand, when the impedance of the external load connected to the output connector
23 is equal to or less than a predetermined value, the type of external load is determined to be
headphones, and the sound output device is recognized to be headphones. In this case, the switch
19 and the switch 45 are closed, and the terminal k of the switch 29 is connected to the terminal
i side. Furthermore, when an external load is not connected to the output connector 23, the
sound output device is recognized as a computer built-in speaker. In this case, the switch 19 and
the switch 45 are opened, and the terminal k of the switch 29 is connected to the terminal j side.
[0038]
FIG. 3 is a flow chart showing a processing procedure of setting of audio equipment and setting
of application software used for reproducing audio media in the notebook personal computer of
the present invention. The processing of the setting of the audio device and the setting of the
application software for reproducing the audio media shown in FIG. 3 is started when the OS of
the notebook personal computer is activated, at the time of polling, or by an interrupt. Here, an
interrupt process performed when plug insertion and removal is detected will be described as an
example.
[0039]
In FIG. 3, when the plug insertion and removal is detected in step S05, the process proceeds to
step S07, and in step S07, the process proceeds to step S09 when the plug is inserted, and the
process proceeds to step S13 when the plug is extracted. In step S13, the sound output
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destination of the audio signal output from the amplifier 15 is recognized as the computer builtin speaker 51, and the process proceeds to step S15. In step S15, the switch 19 is opened, the
terminal k of the switch 29 is connected to the terminal j side, the switch 45 is opened, and the
process proceeds to step S17.
[0040]
In step S09, the switch 45 is closed to mute, the terminal c of the switch 11 is connected to the
terminal b side, and the impedance of the external load connected to the output connector 23 is
measured. The method of measuring the impedance is the same as the method described for the
audio amplifier 10, so the description is omitted here. In step S11, the type of external load
connected to the output connector 23 is determined from the impedance value obtained in step
S09, and a sound output device (output destination device) that converts the audio signal output
from the amplifier 15 into sound Is recognized and the process proceeds to step S17.
[0041]
In step S17, in order to select or confirm the final output destination device (sound output
device), a list of devices to be candidates for the sound output device is popped up on the display
means 37. In step S19, the recognized output destination device is highlighted or blinked so that
the operator can easily identify the recognized output destination device. In step S21, it is
determined whether the operator has selected or confirmed an output device. If the
determination is affirmative, the process proceeds to step S23. If the determination is negative,
the process proceeds to step S17.
[0042]
In step S23, the switch 19 and the switch 29 are appropriately set according to the selected or
confirmed result (sound output device), the terminal c of the switch 11 is connected to the
terminal a side, and the process proceeds to step S25. In step S25, device information suitable for
the selected output device and the application for reproducing the audio media is displayed by
the display means 37, and the computer is actually set, and this flow is ended. The process
proceeds to step S05.
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[0043]
The discrimination recognition process in step S11 is performed as follows. That is, if the
impedance of the external load is a predetermined value, for example, 2 kΩ or less, it is
determined that the type of the external load is a headphone, and the output destination device is
recognized as a headphone. If it is larger than 2 kΩ, the type of external load is determined as
the input circuit of the external audio amplifier, and the output destination device is recognized
as the external monitor speaker. When displaying the "list of output destination candidates" in
step S17, for example, "Please select the type of speaker closest to the current computer" is
displayed on the display screen to prompt the operator to select or confirm, and sound output As
the destination candidate, for example, a computer built-in speaker , a headphone , an
external monitor speaker and the like are displayed in a list.
[0044]
In the display in step S19, the recognized output destination device is displayed so that the
operator can easily recognize it in the pop-up displayed list of output destination device
candidates. For example, one recognized output device is highlighted or blinked, and if the
operator presses the OK button, one previously recognized output device is automatically
selected or confirmed. In this case, if the impedance of the external load is a predetermined
value, for example, 2 kΩ or less, headphones is selected, if it is larger than 2 kΩ, external
monitor speaker is selected, and if nothing is connected to output connector 23, computer
"Internal speaker" is selected. In addition, the operator can further recognize if the display mode
on the display screen is changed according to the determined type of external load or the
recognized sound output device, for example, the icon of the recognized output device is
displayed. It is easy to recognize the output device.
[0045]
As described above, the switch switching process of step S23 is performed as follows. That is,
when the selected output destination device is the computer built-in speaker, the switch 19 and
the switch 45 are opened. When the selected output destination device is a headphone, the
switch 19 and the switch 45 are closed, the terminal k of the switch 29 is connected to the
terminal i side, and a DC bias voltage is applied to the return side of the output connector 23.
Furthermore, when the selected output destination device is an external monitor speaker, the
switch 19 is opened, the switch 45 is closed, and the terminal k of the switch 29 is connected to
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the terminal j side.
[0046]
In the process of step S25, the gain of the audio amplifier is set or the frequency characteristic of
the audio signal is changed according to the selected or confirmed sound output destination
device. In particular, in the setting of an application for reproducing audio media with a surround
effect, the optimum algorithm for obtaining a three-dimensional sound source differs depending
on the output destination device, so the selected output destination device is a headphone or an
external monitor Switch the application software driver or program to the optimal one depending
on whether it is a computer built-in speaker or not. In this switching, part of the operating
system (OS) may be switched.
[0047]
As described above in detail, according to the embodiment of the audio amplifier to which the
present invention is applied, when it is determined that the type of the external load connected to
the output connector is a headphone, the amplifier and the output connector By shorting the
interposed capacitor and applying a DC bias voltage to the return side of the output connector,
the capacitor can be substantially eliminated, thereby reducing the capacitance of the capacitor.
Thus, the audio amplifier can be miniaturized. In addition, since the capacitor is substantially
used only when the impedance of the external load is large, the cutoff frequency of the audio
signal supplied to the headphone can be sufficiently lowered even if the capacity of the capacitor
is reduced.
[0048]
Further, according to the embodiment of the notebook personal computer to which the present
invention is applied, as described for the audio amplifier of the present invention, the capacitance
of the capacitor inserted between the amplifier and the output connector can be reduced. The
computer can be miniaturized, and even if the capacity of the capacitor is reduced, the cutoff
frequency of the audio signal supplied to the headphones can be sufficiently lowered.
[0049]
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Furthermore, the type of external load connected to the output connector is determined, the
sound output device is recognized based on the determination result, and the computer is set
according to the recognition result to set the audio amplifier or audio audio. It becomes possible
to easily set up application software that handles signals and an operating system (OS).
In the flowchart shown in FIG. 3, the processing from step S17 to step S21 can be omitted, and
by omitting the processing, the setting of the computer related to audio can be automated.
[0050]
Brief description of the drawings
[0051]
1 is a block diagram showing an embodiment of the audio amplifier of the present invention.
[0052]
2 is a block diagram showing an audio output unit in the laptop personal computer of the
present invention.
[0053]
FIG. 3 is a flow chart showing a processing procedure of setting of audio equipment and setting
of application software used for reproducing audio media in the notebook personal computer of
the present invention.
[0054]
4 is a block diagram illustrating the main part of the conventional audio amplifier.
[0055]
Explanation of sign
[0056]
11, 19, 29, 45 Switch 13 Oscillator 15 Amplifier 17, 41 Capacitor 21 Resistive element 23
Output connector 31 Biasing DC power supply 33 Impedance discrimination means 33 b
External load discrimination means 35 Microprocessor (MPU) 37 Display means 40 External load
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connection detection Means (jack sense circuit) 47 Speaker drive power amplifier 50 External
load 51 Built-in computer speaker
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