JPH04132496

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DESCRIPTION JPH04132496
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
audio amplification circuit, and more particularly to a high output audio amplification circuit
used for a television apparatus or the like. 2. Related Art In recent years, the addition of functions
to television apparatuses has been increasing, and along with that, the output of sound has also
tended to increase. That is, in the conventional television apparatus, the speaker and the audio
amplification circuit are only for the front, and the audio output is about several W, or with the
recent expansion of the audio equipment, the one having the surround function now. There are
also things that can be voice output or even a few lOW. The audio amplification circuit of the
conventional television apparatus incorporating the surround function is, for example, as shown
in FIG. The audio amplification circuit is a front amplification circuit 1A, IB, a surround circuit 2
including an interlock switch S1, power amplification circuits 3A, 3B, and a front speaker 4A. The
speaker terminal 5 of 4B and the speaker terminals 7 of the surround speakers 6A and 6B are
provided, and the operation / non-operation of the surround circuit 2 can be switched by the
interlock switch S1. On the other hand, the signal input to the television set is also becoming
larger and may be input beyond the allowable maximum input value of the power amplification
circuits 3A and 3B. In response to the increase of the input signal, the power amplifier circuit 3A,
3B has been designed to have a large output and the power supply section has been
strengthened, and the manufacturing cost has been increased accordingly. Because of the
problem to be solved by the invention or the like, in the above-mentioned conventional audio
amplifier circuit, if it is human power exceeding the allowable maximum input value of the power
amplifier circuits 3A and 3B, it may be near the maximum value of the output waveform at the
large output It was cut, and there was a problem that the sense of auditory sense of distortion or
sudden appearance. In addition, when the surround speakers 6A and 6B are connected in a
telephonic device with a built-in surround function, the output load resistance of the power
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amplification circuits 3A and 3B is about half that in the case where the surround speakers 6A
and 6B are not connected. Therefore, the burden on the power amplifier circuits 3A and 3B and
the power supply section is increased, and if it is intended to output a large volume without
distortion in this state, a fairly powerful power supply section is required. Cost will be added.
Also, considering the general Japanese housing circumstances of today, it is not necessary to
output voice more than necessary, and it is more important to reduce the sense of distortion at
the time of excessive input. An object of the present invention is to solve the above-mentioned
problems, and to provide an audio amplification circuit capable of reducing the sense of
distortion at the time of excessive human power without increasing the load on the power
amplification circuit and the power supply unit. is there.
Means for Solving the Problems In order to solve the above problems, the present invention
provides a surround circuit, a speaker terminal for surround, a power amplification circuit, and
an audio signal compression circuit that gradually reduces the gain with an increase in audio
input voltage. And an audio compression switching means for switching between operation and
non-operation of the audio signal compression circuit, and an audio signal which is connected to
the audio compression switching means and is connected to the surround speaker terminal when
the surround speaker is connected. And a forced operation circuit for operating the compression
circuit. According to the above configuration, when the surround speaker is connected to the
surround speaker terminal, the audio signal compression circuit is activated by the forced
activation circuit, and the gain is gradually reduced as the audio input voltage rises. Therefore,
even if an excessive voice signal is input, the input value to the power amplifier circuit becomes
lower than the maximum human power setting value of the power amplifier circuit, and the
occurrence of abrupt distortion is prevented and the sense of auditory sense of distortion is
reduced. . Embodiments of the present invention will be described below with reference to the
drawings. FIG. 1 is a block diagram of an audio amplification circuit according to an embodiment
of the present invention. The same reference numerals as in the prior art denote the same parts
as in the prior art, and a description thereof will be omitted. As shown in FIG. 1, the audio
amplification circuit includes a front amplification circuit IA, IB, a surround circuit 2 having an
interlock switch SL, power amplification circuits 3A, 3B, speaker terminals 5 of front speakers
4A, 4B, surround In addition to the speaker terminals 7 of the speakers 6A and 6B, the audio
signal compression circuits 11A and IIB that gradually decrease the gain with the increase of the
audio input voltage, and the audio that switches the operation and non-operation of the audio
signal compression circuits 11A and IIB The interlock switch S2 as compression switching means
and the interlock switch S2 are connected, and when connected to the surround speaker terminal
7 for the surround spin forces 6A and 6B, this is detected to detect the audio signal compression
ports B11A and 11B. And a forced operation circuit 12 to be operated. The relationship between
the input and the output of the audio signal compression circuits 11A and 11B is as shown in
FIG. 2, and the linearity of the input to output at the time of large input becomes worse when
passing through the audio signal compression circuits 11A and 11B. Or, the occurrence of
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sudden distortion is mitigated, and the sense of distortion in the sense of hearing is reduced.
With the above configuration, when the surround speaker 6A or 6B is connected to the surround
speaker terminal 7, this is detected by the forced activation circuit 12 and the interlock switch S2
is closed to activate the audio signal compression circuit IIA or 11B. Be done. As a result, even if
an excessive voice signal is input, the input value to the power amplification circuits 3A and 3B is
made equal to or less than the maximum input setting value of the power amplification circuits
3A and 3B, and occurrence of abrupt distortion is prevented, and auditory distortion I feel less.
Along with this, the power amplification circuits 3A, 3B are not forced to perform an
unreasonable operation, and at the same time, the burden on the power supply unit is also
reduced. When the surround speakers 6A and 6B are not connected, the forced activation circuit
12 does not operate, and the audio signal compression circuit 11A and JIB are manually switched
by the interlock switch S2. As described above, according to the audio amplification circuit of the
present invention, an audio signal compression circuit that gradually reduces the gain with an
increase in audio input voltage, and an audio that switches the operation / non-operation of the
audio signal compression circuit. A compression switching means, and a forced operation circuit
connected to the audio compression switching means, for detecting a surround speaker when
connected to a surround speaker terminal, and operating an audio signal compression circuit, are
provided. Even when an excessive sound signal is input when the surround speaker is used, the
input value to the power amplifier circuit or the maximum input setting value of the power
amplifier circuit becomes equal to or less than the maximum input setting value of the power
amplifier circuit. Also, it is possible to suppress the cost increase, and at the same time, it is
possible to prevent the occurrence of a sudden distortion and to reduce the sense of distortion in
hearing.
[0002]
Brief description of the drawings
[0003]
1 is a block diagram of an audio amplification circuit according to an embodiment of the present
invention, FIG. 2 is a characteristic diagram of an audio signal compression circuit of the audio
amplification circuit, and FIG. 3 is a block diagram of a conventional audio amplification circuit. .
2: Surround circuit, 3A, 3B: Power amplification circuit, 6A, 6B: Speaker for surround, 7: Speaker
terminal for surround, 11A, IIB: Audio signal compression circuit, 12. · Forced operation circuit,
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S2 ... interlocking switch (audio compression switching means).
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