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JPH0511692

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DESCRIPTION JPH0511692
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker switching circuit.
[0002]
2. Description of the Related Art Conventionally, in an audio system in which an external speaker
and an internal speaker can be used, either the external speaker or the internal speaker is
selectively used depending on the environment in which the audio system is to be used. It is
becoming common to listen to music, radio broadcasts, etc.
[0003]
However, as shown in FIG. 2, the switching system of the external speaker and the internal
speaker in such an audio system is usually a 3-pin type jack 3, and the receiving system of the
jack 3 is usually used. One terminal 6 of the unit 3-1 is connected to, for example, an output of
an audio system, for example, an amplifier (AMP), the terminal 7 is connected to the internal
speaker 2, and the other terminal 8 is grounded. It becomes composition
[0004]
On the other hand, when the insertion portion 3-2 of the jack portion 3 connected to the external
speaker is inserted into the receiving portion 3-1 of the jack 3, the switching piece P connected
to the terminal portion 6 is displaced. The connection 5 between the switching piece P and the
internal end of the terminal 7 connected to the internal speaker 2 is opened to drive the external
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speaker.
[0005]
However, such a 3-pin type jack 3 is not a general one and has problems such as high cost, and is
not used in large quantities, so insertion of 2-pin type in the switching circuit of such a speaker
When using a jack for substitution, since the drive of the internal speaker can not be shut off,
there is a problem that both the external speaker and the internal speaker are driven at the same
time.
[0006]
SUMMARY OF THE INVENTION The object of the present invention is to solve the problems in
the prior art and to efficiently and reliably switch between external and internal speakers using a
2-pin jack. To provide a speaker switching circuit.
[0007]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
adopts the following technical configuration.
That is, in a circuit for switching between an external speaker and an internal speaker using a 2pin type jack, one terminal of the jack receiver is grounded and the other terminal is connected
to the audio amplifier. A circuit for applying a predetermined bias voltage via a bias resistor is
connected, and a voltage detection circuit is provided for connecting the internal speaker to the
connection via an appropriate switch circuit and further detecting the potential at the connection.
The speaker switching circuit is configured such that the switch circuit is controlled according to
the output of the voltage detection circuit.
[0008]
Since the present invention adopts the above-described technical configuration, when the jack of
the external speaker is inserted, the fact that the bias voltage is applied to the terminal portion of
the jack receiving portion is applied. Since the switch circuit for driving and controlling the
internal speaker is cut off based on the detection of the voltage drop, the driving of the internal
speaker is reliably stopped.
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2
[0009]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,
the preferred embodiment of the speaker switching circuit according to the present invention
will be described in detail. FIG. 1 is a block diagram showing a specific example of the speaker
switching circuit according to the present invention. In the circuit for switching the external
speaker 1 and the internal speaker 2 by using the jack 3, one terminal 8 of the jack receiver 3-1
is grounded and the other terminal 6 and the audio output (amplifier) 4 are connected. Is
connected to the circuit 10 for applying a predetermined bias voltage via the bias resistor R to
the connecting portion 9 to which is connected, and the internal speaker 2 is connected to the
connecting portion 9 via the appropriate switch circuit 13; A speaker switching circuit is shown
which is provided with a voltage detection circuit 14 for detecting the potential of the connection
portion 9 and configured to control the switch circuit 13 according to the output of the voltage
detection circuit 14. .
[0010]
In the present invention, a capacitor 11 for cutting an appropriate DC component may be
provided between the audio output unit 4 such as the amplifier and the connection unit 9.
Although the bias voltage in the present invention is not particularly limited, in the case of an onvehicle audio apparatus, for example, 12 V, and in other cases, 5 V to 8 V, for example, is
preferable.
[0011]
Further, the voltage detection circuit 14 used in the present invention is not particularly limited
in its configuration, but it detects the potential of the connection portion 9 and compares it with
a predetermined predetermined threshold value. If the potential drops below the threshold value,
a built-in comparison circuit composed of an appropriate comparator or the like that can output
an output signal
[0012]
Further, the structure of the switch circuit 13 for controlling the drive of the internal speaker 2 is
not particularly limited, but a mechanism capable of electronically turning on / off according to
the on / off signal of the voltage detection circuit 14 Any switching circuit can be used if it is
built-in.
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[0013]
The operation of the speaker switching circuit according to the present invention will now be
described. Now, considering the case where only the internal speaker is driven without using the
external speaker 1, the bias voltage applied from the bias circuit 10 of the connecting portion 9
is considered. Since the voltage maintains a predetermined high voltage, the voltage detection
circuit 14 for detecting the potential of the connection portion 9 outputs an ON signal, that is, an
“H” level signal.
Therefore, since the switching circuit 13 is turned on according to the signal of the “H” level,
the audio output is transmitted to the internal speaker to drive the internal speaker.
[0014]
When the external speaker 1 is used, when the insertion block stage 3-2 of the 2-pin type jack is
inserted into the receiving portion 3-1 of the 2-pin type jack, the internal coil of the external
speaker 1 is used. Is connected to the resistor R of the bias circuit, so if the value of the resistor R
is made sufficiently large, the potential of the connection portion 9 is lowered by the current
flowing to the external speaker.
[0015]
When the external speaker is connected by setting the potential drop of the connection portion 9
due to the voltage drop to be lower than the threshold of the voltage detection circuit 14, the
voltage detection circuit 14 is turned off. Therefore, since the switching circuit 13 is turned off,
the audio output is not transmitted to the internal speaker, and only the external speaker is
driven.
[0016]
According to the present invention, since it is configured as described above, the 2-pin type
conventionally used in large amounts conventionally without using the uncommon 3-pin type
jack. Not only can switching between external and internal speakers be reliably and efficiently
performed by using a jack, but it is convenient because it has commonality with other devices.
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