JPH07154309

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DESCRIPTION JPH07154309
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
signal switching circuit which changes the function of an apparatus by adding a circuit having a
function to an apparatus having a circuit.
[0002]
2. Description of the Related Art In circuits that handle alternating current signals, such as
circuits used for audio equipment, additional functions can be added to the functions that the
equipment originally has, by additionally connecting circuits having certain functions, or A
change of the original function is performed. The example is demonstrated using figures.
[0003]
FIG. 7 shows a part of the circuit in the audio device 11, and the changeover switch 24 is
connected to the circuit 21 which is connected between the input terminal 22 and the output
terminal 23 and is scheduled to be added with a function in the future. . The audio device 11 is
also provided with two external terminals 25 and is connected to the input side contact of the
changeover switch 24. When the audio device 11 is shipped, the changeover switch 24 is in the
illustrated state, and the output of the functional circuit 21 is output from the output terminal 23
as it is.
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[0004]
When it is desired to add a function to the audio device 11, the two switches 27 of the additional
circuit 26 having the function are connected to the external terminals 25 of the audio device 11,
and then the changeover switch 24 is switched. As a result, the additional circuit 26 is connected
in series to the circuit 21, and the function of the additional circuit 26 is added to the function of
the circuit 21. FIG. 8 shows an example of a signal switching circuit which replaces the function
of the circuit which the audio device 11 originally has with another circuit having another
function.
[0005]
In this example, the circuit 21 and the additional circuit 26 are respectively connected to the
input side contacts of the changeover switch 24. When the additional circuit 26 is connected to
the audio device 11 and the changeover switch 24 is switched, the circuit 21 originally included
in the audio device 11 is disconnected, and only the additional circuit 26 connected between the
external terminals 25 has the input terminal 22 and the output terminal Connected between 23
As a result, the function of the circuit 21 originally provided to the audio device 11 can be
changed to the function provided to the additional circuit 26.
[0006]
SUMMARY OF THE INVENTION In the conventional signal switching circuit described above, the
terminal 27 of the additional circuit 26 is connected to the external terminal 25 of the audio
device 11 when adding or changing the function. Then, the changeover switch 24 has to be
switched manually. It is inconvenient to operate the changeover switch 24 as described above,
and there is a problem that the function of the additional circuit 26 can not be utilized if the
switching is forgotten.
[0007]
An object of the present invention is to provide a signal switching circuit that switches signals
automatically when a circuit having an additional function is connected to a device.
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[0008]
SUMMARY OF THE INVENTION In order to solve the above problems, the present invention
provides a signal switching circuit for adding a circuit having a certain function to a circuit, an
input terminal, an output terminal, an OP amplifier, and a plurality of circuits. The OP amplifier
has a non-inverting input connected to the input terminal via a resistor, an inverting input and an
output connected via a resistor, an output connected to the output terminal, and The plurality of
external terminals are a first terminal connected to the input terminal, a second terminal
connected to the non-inverting input, a third terminal connected to the inverting input, and a
fourth terminal connected to the power supply. And the fifth terminal connected to the ground.
[0009]
The signal switching circuit is provided in advance in a circuit which is scheduled to add a
function in the future.
Then, to add a function to the circuit, the additional function circuit having the function is
connected to the external terminal of the signal switching circuit.
The additional function circuit has an external terminal corresponding to the external terminal of
the signal switching circuit, and is configured by internally connecting predetermined circuit
elements.
[0010]
When the external terminal of the additional function circuit is connected to the external
terminal of the signal switching circuit, the circuit originally present and the additional function
circuit are switched and connected to the OP amplifier, and the function of the additional
function circuit is automatically provided. It will be added to the function of the circuit originally
present. Since addition of this function is automatically performed by connecting an additional
function circuit, there is no occurrence of an operation mistake or the like of the changeover
switch as in the prior art.
[0011]
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DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an embodiment in which the
signal switching circuit of the present invention is applied to an audio device. The signal
switching circuit 1 is provided on the output side of a circuit 2 having a function provided in the
audio device 11. The input terminal 3 of the signal switching circuit 1 is connected to the noninverting input 5 of the OP amplifier 4 via a resistor 9. The output 7 of the OP amplifier 4 is
connected to the output terminal 8 and is further connected to the inverting input 6 through the
resistor 10.
[0012]
Five external terminals 13 (a to e) for connecting the additional function circuit 12 from the
outside are connected to the signal switching circuit 1. The first terminal a of the external
terminal 13 is connected to the input terminal 3 of the signal switching circuit 1, the second
terminal b is connected to the non-inverting input 5 of the OP amplifier 4, and the third terminal
c is connected to the inverting input 6. The fourth terminal d is connected to the power supply +
B in the audio device 11, and the fifth terminal e is connected to the ground GND.
[0013]
When the additional function circuit 12 is not connected to the external terminal 13, the output
signal of the circuit 2 is input to the non-inverting input 5 of the OP amplifier 4 and is output to
the output terminal 8 as it is. When attempting to add a function to this circuit 2, the additional
function circuit 12 is connected to the audio device 11. The additional function circuit 12 is
provided with external terminals 14 (a ′ to e ′) connected to the external terminals 13 of the
audio device 11.
[0014]
A first example of the additional function circuit 12 is shown in FIG. The circuit of this example is
a circuit to which a phase inversion function is added, and a resistor 15 is connected between the
first terminal a 'and the third terminal c', and between the second terminal b 'and the fifth
terminal e' Directly connected. FIG. 3 shows an equivalent circuit of the signal switching circuit 1
to which the circuit of FIG. 2 is connected. With the addition of the circuit of FIG. 2, the inverting
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input 6 of the OP amplifier 4 is connected to the output of the circuit 2 and the non-inverting
input 5 is grounded. Therefore, when the additional function circuit 12 of FIG. 2 is connected to
the audio device 11, the output signal of the circuit 21 is inverted in phase and output from the
output terminal 8, and when the additional function circuit 12 is removed, the phase inversion
function is automatically canceled. Ru. As described above, since switching is automatically
performed only by connecting the additional function circuit 12 to the signal switching circuit 1,
there is no problem such as an operation error of the changeover switch as in the prior art.
[0015]
FIG. 4 shows, as a second example of the additional function circuit 12, a circuit to which a sound
quality adjustment function (graphic equalizer circuit) is added. In the additional function circuit
12 of FIG. 4, a plurality of resistors r are connected in parallel between the second terminal b
'and the third terminal c', and each of the plurality of resistors r and the fifth terminal e '(earth)
The resonant circuit consisting of L, C, and R is connected between them. The addition of the
circuit of FIG. 4 means that the graphic equalizer circuit is connected to the output of the circuit
2.
[0016]
FIG. 5 shows an example of adding an additional circuit 16 having the function of, for example, a
DSP (digital signal processor) controller. The additional function circuit 12 of FIG. 5 is provided
with an additional circuit 16 and an OP amplifier 17, the input of the additional circuit 16 is
connected to the first terminal a ′ of the additional function circuit 12, and the output is an
inversion of the OP amplifier 17. Connect to the input. The noninverting input of the OP
amplifier 17 is connected to the second terminal b 'and the fifth terminal e'. The output of the OP
amplifier 17 is directly connected to the third terminal c 'and connected to the inverting input
through the resistor 18. The power supply of the OP amplifier 17 is connected to the fourth
terminal d '.
[0017]
FIG. 6 shows an equivalent circuit of the signal switching circuit 1 to which the circuit of FIG. 5 is
connected. By the addition of the circuit of FIG. 5, the additional circuit 16 is connected in series
to the output of the circuit 2 and is connected to the inverting input of the OP amplifier 17. Then,
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the signal whose phase is inverted by the OP amplifier 17 is further input to the inverting input 6
of the OP amplifier 4 of the signal switching circuit 1, and the phase is restored. On the other
hand, the noninverting input 5 of the OP amplifier 4 is grounded. Therefore, a signal in which the
function of the additional circuit 16 is added to the function of the circuit 2 is obtained from the
output terminal 8.
[0018]
Although the example in which the signal switching circuit 11 of the present invention is applied
to the audio device 11 has been described above, the present invention is not limited to the audio
device, and can be applied to all circuits that handle AC signals. When the additional function
circuit 12 is connected to the audio device 11, the function of the circuit 2 can be replaced with
the function of the additional function circuit 12 by disabling the circuit 2 by computer software.
[0019]
According to the present invention, signal switching is automatically performed when a circuit
having an additional function is connected to the signal switching circuit, so that the operation
can be simplified and an operation error can be made. It can be prevented.
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