JPH04373399A - Excessive sound output limiting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for limiting excessive audio output in an audio amplifier circuit.

0002

2. Description of the Related Art Conventionally, as a technique in this field, there has been a clip circuit as shown in FIG. 6, which uses a diode or the like provided at the input stage of an audio amplifier circuit. As shown in this figure, when the amplitude of the input signal becomes larger than the forward voltage of the diode, the output waveform is clipped and the excessive signal is limited, as shown in Fig. 6c. It was said that it would be done.

0003

[Problem to be Solved by the Invention] However, with the circuit configured as described above, when a signal with an amplitude greater than the forward voltage is input, the output waveform always remains distorted, making it difficult to obtain a sound quality that is not very pleasing to the ear. The problem was that there was no.

SUMMARY OF THE INVENTION An object of the present invention is to provide an excessive audio output limiting circuit which eliminates the above-mentioned problems, suppresses waveform distortion, and reduces deterioration of sound quality.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention controls a voltage-controlled volume control integrated circuit using the amplitude of the output signal, thereby controlling only excessive signals. To attenuate the signal amplitude itself without clipping.

[0006]

[Operation] According to the present invention, as described above, the amplitude of the output signal is converted into a DC voltage, and the voltage is used to control the volume balance control terminal or the volume control terminal of a voltage-controlled volume control integrated circuit. Therefore, even if an excessive signal is input, the volume is controlled in the direction of attenuation, so that the signal waveform does not continue to be output with a distorted shape. Therefore, even if an excessive signal continues to be input, the output waveform will not continue to be distorted, and the audible distortion can be eliminated.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an excessive sound output limiting circuit showing an embodiment according to claim 1 of the present invention, and FIG. 2 shows an excessive sound output limiting circuit showing an embodiment according to claim 2 of the present invention. FIG.

In FIG. 1, 10 is a voltage-controlled integrated circuit for volume control, 11 is a circuit for detecting and amplifying the output signal from the integrated circuit, 12 is a circuit for rectifying and smoothing the signal from 11, and 13a and 13b. is an input terminal of the integrated circuit 10, but the channel on the 13b side is not used; 14 is a volume control terminal; and 15 is a volume balance control terminal to which the DC signal from 12 is applied. FIG. 3 shows the control characteristics by the terminal 15 of the integrated circuit 10.

First, in a normal state, since the output of the circuit 12 does not exceed a in FIG. 3, the amount of attenuation in this circuit is determined by the voltage of the volume control terminal 14. When the output signal 12 increases and the output of 12 exceeds a in FIG. 3, the attenuation section with the volume balance control characteristic operates to attenuate the amplitude of the output signal and suppress output of an excessive signal. At this time, the amount of attenuation in this circuit is greater than that determined by the voltage at the volume control terminal 14.

Similarly, in FIG. 2, 10 is a voltage-controlled integrated circuit for volume control, 11 is a circuit for detecting and amplifying the output signal from the integrated circuit 10, and 20 is the larger signal of the two input systems. 21 is a circuit that controls the current drawn according to the magnitude of the DC signal from 20; 22 is a terminal that applies a volume control voltage; FIG. 4 shows the control characteristics of terminal 14 of integrated circuit 10; 5 shows the drawing current control characteristic according to 21.

First, in the normal state, since the output of the terminal 20 does not exceed a in FIG. 5, the voltage at the terminal 22 is directly applied to the terminal 14.
However, if an excessive signal is input and the amplitude of the output signal increases, and the output of 20 exceeds a in FIG.
Due to the voltage drop across R1 and R2 of 1, the voltage applied to terminal 14 becomes lower than the voltage applied from terminal 22, and from FIG. Hold the signal output.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0014]

As described in detail above, according to the present invention, the following effects can be achieved. 1. Since the amplitude of the output signal is detected and the amount of attenuation is controlled accordingly, even if excessive signals are continuously input, the signal waveform can be output without continuing to be distorted. 2. Since the signal waveform is not clipped during excessive input, deterioration in auditory sound quality is suppressed.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an excessive audio output limiting circuit in an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an excessive audio output limiting circuit in an embodiment of the present invention.

[Figure 3] Volume balance control characteristic diagram of integrated circuit for volume control

[Figure 4] Volume control characteristic diagram of integrated circuit for volume control

[Figure 5]
Drawing current control characteristic diagram of 21 circuits in Figure 2

[Figure 6] (
a) Schematic diagram of the conventional amplitude limiting circuit (b) Output waveform diagram of the same

[Explanation of symbols]

10 Volume control integrated circuit 11 Audio signal amplification circuit 12 Rectification and smoothing circuit 13a, 13b Audio signal input terminal 1 of integrated circuit
4 Integrated circuit volume control terminal 15 Integrated circuit volume balance control terminal 20
2-system input rectifier and smoothing circuit 21 Voltage-current conversion circuit 22 Volume control terminal

Claims (2)

[Claims] 1. A voltage-controlled volume control integrated circuit comprising two channels of input/output terminals, a volume control terminal, and a volume balance control terminal between the two channels; connected to a circuit having a function of rectifying and smoothing the signal, using only one channel of the two channels of the integrated circuit, and connecting the input of the rectifying and smoothing circuit to the output of the channel being used. However, this output is connected to the volume balance control terminal of the integrated circuit, and if an excessive signal is output from the integrated circuit,
Excessive audio output limiting circuit that works with the attenuation function of balance control to prevent excessive signals from continuing to be output. 2. The volume control integrated circuit, the rectifying and smoothing circuit, and a circuit that is connected to the output of the rectifying and smoothing circuit and can control the current flowing into the output terminal according to the voltage thereof;
The output of the voltage/current conversion circuit is connected to the volume control terminal of the integrated circuit, and when an excessive signal is output from the integrated circuit, the output of the voltage/current conversion circuit is connected to the output terminal of the voltage/current conversion circuit. An excessive audio output limiting circuit that allows current to flow into the volume control terminal and lowers the volume control voltage applied to the volume control terminal to prevent excessive signals from continuing to be output.