JP2845596B2 - Audio amplification circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio amplifier circuit, and more particularly to an audio amplifier circuit having a large output used for a television device or the like.

2. Description of the Related Art In recent years, as the number of functions added to a television device has increased, the output of audio has also tended to increase accordingly. That is, in the conventional television device, the speaker and the sound amplification circuit were only for the front, and the sound output was about several W. However, with the recent enhancement of sound equipment, the surround function is now built in. Some of them have been used, and some have audio outputs up to several tens of watts. FIG. 3 shows an example of an audio amplifier circuit of a conventional television device having a built-in surround function. This audio amplifier circuit includes preamplifier circuits 1A and 1B, a surround circuit 2 having an interlocking switch S1, power amplifier circuits 3A and 3B, speaker terminals 5 of front speakers 4A and 4B, and surround speakers 6A, A 6B speaker terminal 7 is provided, and the operation and non-operation of the surround circuit 2 can be switched by an interlock switch S1.

On the other hand, the signal input to the television device is also increasing, and may be input exceeding the allowable maximum input value of the power amplifier circuits 3A and 3B. In response to the increase in the input signal, designs for increasing the power of the power amplifier circuits 3A and 3B and strengthening of the power supply unit have been made, and the manufacturing cost has been increasing accordingly.

However, in the audio amplifier circuit of the above-described conventional configuration, when there is an input exceeding the allowable maximum input value of the power amplifier circuits 3A and 3B, the vicinity of the maximum value of the output waveform is cut off at the time of large output. As a result, there is a problem that a sense of distortion on the auditory sense suddenly appears.
Also, when the surround speakers 6A and 6B are connected to a television device having a built-in surround function, the output load resistance of the power amplifier circuits 3A and 3B is reduced to about half compared to 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 unit increases, and in order to output a large volume without distortion, a considerably strong power supply unit is required. Will be added. In addition, in view of modern general housing conditions, it is not necessary to output sound more than necessary, and it is more important to reduce the distortion at the time of excessive input.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an audio amplifier circuit that can reduce a feeling of distortion at the time of excessive input without increasing a load on a power amplifier circuit and a 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 surround speaker terminal, a power amplifier circuit, and an audio signal compression circuit that gradually reduces the gain as the audio input voltage increases. An audio compression switching means for switching operation / non-operation of the audio signal compression circuit, and an audio signal which is connected to the audio compression switching means and detects when a surround speaker is connected to the surround speaker terminal and detects the audio signal. 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 operated by the forced operation circuit, and the gain is gradually reduced as the audio input voltage increases. Therefore, even if an excessive audio signal is input, the input value to the power amplifier circuit becomes equal to or less than the maximum input set value of the power amplifier circuit, and abrupt distortion is prevented from occurring, so that the audible distortion can be reduced.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of an audio amplifier circuit according to an embodiment of the present invention. The same elements as those of the prior art are denoted by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 1, the audio amplifier circuit is a preamplifier circuit.
1A, 1B, surround circuit 2 having interlocking switch S1, power amplifier circuits 3A, 3B, speaker terminals 5 of front speakers 4A, 4B, speaker terminals 7 of surround speakers 6A, 6B, and an increase in audio input voltage. The audio signal compression circuits 11A and 11B that gradually reduce the gain in accordance with
An interlocking switch S2 as an audio compression switching means for switching between operation and non-operation of 1A and 11B, and is connected to the interlocking switch S2 and detected when the surround speakers 6A and 6B are connected to the surround speaker terminal 7. And a forced operation circuit 12 for operating the audio signal compression circuits 11A and 11B. The relationship between the inputs and outputs of the audio signal compression circuits 11A and 11B is as shown in FIG.
When the signal passes through 11A and 11B, the linearity of input to output at the time of large input deteriorates, but the occurrence of sharp distortion is reduced, and the sense of distortion can be reduced.

With the above configuration, when the surround speakers 6A and 6B are connected to the surround speaker terminal 7, this is detected by the forced operation circuit 12, the interlock switch S2 is closed, and the audio signal compression circuits 11A and 11B are operated. You. As a result, even if an excessive audio signal is input, the input value to the power amplifier circuits 3A and 3B is set to be equal to or less than the maximum input set value of the power amplifier circuits 3A and 3B, and a sudden distortion is prevented from being generated, so that the audible distortion is prevented. Feeling can be reduced. Along with this, the power amplifier circuits 3A and 3B are not forced to operate unnecessarily, and the burden on the power supply unit is reduced at the same time.

When the surround speakers 6A and 6B are not connected, the forced operation circuit 12 does not operate, and the audio signal compression circuits 11A and 11B can be manually switched by the interlock switch S2.

As described above, according to the audio amplification circuit of the present invention, the audio signal compression circuit that gradually reduces the gain as the audio input voltage increases, and the audio that switches the operation and non-operation of the audio signal compression circuit A surround switching means connected to the audio compression switching means and a forced operation circuit for detecting when a surround speaker is connected to the surround speaker terminal and activating the audio signal compression circuit; The input value to the power amplifier circuit becomes less than the maximum input setting value of the power amplifier circuit even if an excessive audio signal is input when using the speaker for the system, so that the power amplifier circuit does not operate unreasonably and the burden on the power supply unit Thus, the cost increase can be suppressed, and the occurrence of abrupt distortion can be prevented, so that the audible distortion can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of an audio amplifier circuit according to an embodiment of the present invention, FIG. 2 is a characteristic diagram of an audio signal compression circuit of the audio amplifier circuit, and FIG. 3 is a block diagram of a conventional audio amplifier circuit. . 2 ... Surround circuit, 3A, 3B ... Power amplifier circuit, 6A, 6B
... surround speakers, 7 ... surround speaker terminals, 11A, 11B ... audio signal compression circuits, 12 ... forced operation circuits, S2 ... interlocking switches (audio compression switching means).

Claims (1)

(57) [Claims] 1. A surround circuit, a surround speaker terminal, a power amplifier circuit, an audio signal compression circuit for gradually reducing a gain with an increase in an audio input voltage, and operation / non-operation of the audio signal compression circuit. A voice compression switching means for switching, and a forced operation circuit connected to the voice compression switching means and for detecting when a surround speaker is connected to the surround speaker terminal and activating the audio signal compression circuit; Amplifier circuit.