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JPH0555699

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPH0555699
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
stereo amplifier, and more particularly to a stereo amplifier that prevents temperature rise.
[0002]
2. Description of the Related Art In a conventional stereo amplifier, as shown in FIG. 5, a switch
for switching according to the impedance of the connected speaker and a switch for switching
the transformer tap are interlocked, and the impedance of the connected speaker is 8 Ω or more.
In some cases, the power transformer tap is connected high, and when the impedance of the
connected speaker is less than 8 Ω, the power transformer tap is connected low.
[0003]
In such a stereo amplifier, if the surround function is turned on when the transformer tap is high,
the power supply unit and the power amplifier unit are used to drive the amplifiers for the rear
and center speakers in addition to the front speaker amplifier. There is a problem that the
temperature rise of the
[0004]
In order to solve the above problems, some microcomputer operations prohibit the surround
function when the transformer tap is high.
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[0005]
[Problems to be Solved by the Invention] The above-described conventional stereo amplifier has a
drawback that the surround function can not be used when a speaker having an impedance of 8
Ω or more is connected.
[0006]
The present invention has been made in view of the above-described point, and its object is to
make it possible to use the surround function even when a speaker having an impedance of 8 Ω
or more is connected, Furthermore, it is providing the stereo amplifier which prevented
temperature rise, such as a power supply part.
[0007]
SUMMARY OF THE INVENTION A stereo amplifier according to the present invention is a stereo
amplifier having a switch switched according to the impedance of a connected speaker and a
surround function, and inputs an audio signal to a power amplifier through an output limiter,
Alternatively, a switch is provided to switch to input the power amplifier without passing through
the output limiter, and when the impedance of the connected speaker is less than 8 Ω and the
surround is on, the audio signal is output to the power amplifier through the output limiter.
Configured to be input
[0008]
Furthermore, in the stereo amplifier according to the present invention, in the stereo amplifier
having a switch for switching according to the impedance of the connected speaker and the
surround function, the impedance of the connected speaker is 8 Ω or more, and when the
surround is off, the power transformer The tap is connected high, otherwise the power
transformer tap is connected low.
[0009]
According to the use of the output limiter of the stereo amplifier of the present invention, when
the impedance of the speaker to be connected is less than 8 Ω and the surround is on, the audio
signal is transmitted through the output limiter to the power amplifier. Therefore, the maximum
power for driving the speaker is limited and the temperature rise of the power supply unit or the
like is prevented.
[0010]
In addition, when the impedance of the speaker to be connected is 8Ω or more and the surround
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2
is off, the power supply transformer tap is connected high, and the one connecting the power
supply transformer tap low is the surround Is on and the impedance of the speaker to be
connected is 8 Ω or more, the power supply transformer tap is connected low, so the power
supply voltage is lowered and the temperature rise of the power supply unit or the like is
prevented.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A stereo amplifier according to an
embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a characteristic portion of a stereo amplifier according to a
first embodiment of the present invention.
In the figure, reference numeral 1 denotes a microcomputer with a built-in ROM and RAM,
according to the program written in the ROM and the signal from the key matrix 2
[0012]
A switch 3 is switched by the impedance of the connected speaker, and its on / off signal is
inputted to the microcomputer 1.
[0013]
Reference numeral 5 denotes an amplifier in which the amplitude of the output signal is limited
to a certain range, that is, an output limiter.
The output signal of the voltage amplifier is selectively input to the output limiter 5 or the power
amplifier by the switch 4 operated by the microcomputer 1.
The power amplifier drives the front speaker.
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[0014]
A switch 6 switches the tap of the power supply transformer 7 to high and low, and is connected
to the high side when the impedance of the connected speaker is 8 Ω or more, and when the
impedance of the connected speaker is less than 8 Ω It is operated by the microcomputer 1 so as
to be connected to the low side.
[0015]
Although the speaker relays such as the surround center speaker or the rear speaker are
operated by the microcomputer 1, these speaker relays are illustrated.
[0016]
Next, with reference to FIG. 2, the characteristic operation of this embodiment in the
microcomputer 1 will be described.
[0017]
The routine shown in FIG. 2 is a routine that is always carried out after the operation of turning
on and off the surround function is performed.
[0018]
When this routine is called, first, in step S1, it is judged whether or not the switch 3 is set to the
side less than the speaker impedance 8 Ω. If it is less than 8 Ω, the process proceeds to step S2.
Otherwise, shift to step S3
[0019]
In step S2, it is determined whether the surround function is turned on. If the surround function
is turned on, the process proceeds to step S4, otherwise the process proceeds to step S3.
[0020]
In step S3, the switch 4 is switched to the power amplifier side to complete this routine, and in
step S4, the switch 4 is switched to the output limiter side to complete this routine.
[0021]
By the above operation, when the impedance of the connected speaker is less than 8 Ω and the
surround is on, the audio signal is input to the power amplifier through the output limiter, and
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the power of the front speaker is limited, so the power supply Temperature rise of
[0022]
FIG. 3 is a block diagram showing a characteristic part of a stereo amplifier according to a second
embodiment of the present invention.
In the figure, reference numeral 1 denotes a microcomputer incorporating a ROM and a RAM,
which operates according to a program written in the ROM and a signal from the key matrix 2.
[0023]
A switch 3 is switched by the impedance of the speaker to be connected, and its on / off signal is
inputted to the microcomputer 1.
[0024]
A switch 6 switches the tap of the power supply transformer 7 to high and low, and is operated
by the microcomputer 1.
[0025]
Although the speaker relays such as the surround center speaker or the rear speaker are
operated by the microcomputer 1, these speaker relays are illustrated.
[0026]
Next, with reference to FIG. 4, the characteristic operation of this embodiment in the
microcomputer 1 will be described.
[0027]
The routine shown in FIG. 4 is a routine that is always carried out after the operation of the
speaker relay is performed.
[0028]
When this routine is called, first, in step S1, it is judged whether or not the switch 3 is set to the
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5
speaker impedance of 8 Ω or more. If it is 8 Ω or more, the process proceeds to step S2.
Otherwise, shift to step S3
[0029]
In step S2, it is determined whether the surround function is turned on. If the surround function
is turned on, the process proceeds to step S3. If not, the process proceeds to step S4.
[0030]
At step S3, the switch 6 is switched to the low side of the power transformer tap to end this
routine, and at step S4, the switch 6 is switched to the high side of the power transformer tap to
end this routine.
[0031]
According to the above operation, the power transformer tap is switched to the high side only
when the impedance of the speaker to be connected is 8 Ω or more and the surround is off, so
that the temperature rise of the power source or the like can be prevented.
[0032]
According to the stereo amplifier of the present invention, the surround function can be used
even when a speaker of less than 8 Ω is connected, and moreover, the temperature rise of the
power supply unit or the like can be prevented.
[0033]
Brief description of the drawings
[0034]
1 is a block diagram showing a characterizing portion of a stereo amplifier according to a first
embodiment of the present invention.
[0035]
2 is a flow chart showing a characteristic portion of the microcomputer operation in the same
embodiment.
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[0036]
3 is a block diagram showing a characteristic portion of a stereo amplifier according to a second
embodiment of the present invention.
[0037]
4 is a flow chart showing a characteristic portion of the microcomputer operation in the same
embodiment.
[0038]
5 is a block diagram showing an example of the power transformer connection portion of the
conventional stereo amplifier.
[0039]
Explanation of sign
[0040]
Reference Signs List 1 microcomputer 2 key matrix 3 impedance changeover switch 4
changeover switch 5 output limiter 6 tap changeover switch 7 transformer
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