JPH10126182A - Clip preventing device for amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily control the sound volume through a speaker, despite the reduction in value of the voice signal by setting the input level of a power amplifier circuit, in response to the level of the voice input signal and the gain of an electronic volume. SOLUTION: The output value B of an arithmetic means 12 is initialized to 1, and the gain Gv of an electronic volume 16 and the gain Ga of a power simplifier 17 are fetched. Then the peak level INp is fetched from a sample hold circuit 11 within a unit time of the voice input signal. The means 12 calculates X=INp.Gv.Ga and compares it with the click level C of the amplifier 17. If X<=C is satisfied, the prescribed value α is added to the output value B to satisfy B=B+α. If this new value B is larger than 1, it is kept at 1. If X>C is satisfied, the value B is set at C/X, and the new output value is outputted to a multiplier 14. This operation is repeated, for example, for the newly sampled peak level INp after 100ms. As a result, the generated sound volume is always satisfactory and is not distorted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a clip prevention device for an amplifier.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional amplifier.

[0003] The amplifier shown in FIG.
, A gain adjustment resistor 22, a power amplification circuit 17, and a speaker 18. The compressor 21 raises the low-pitched sound level of the audio input signal, suppresses the high-pitched sound level, and thereby makes it easier to listen to the music. The signal passed through the compressor 21 is applied to the gain adjusting resistor 22, By adjusting the value of the gain adjusting resistor 22, the input level in the power amplifier circuit 17 is adjusted.

In the conventional example shown in FIG. 3, if the resistance value of the gain adjustment resistor 22 is reduced, the volume generated by the speaker 18 can be increased. When the level of the input signal exceeds a predetermined value, there is a problem that the sound output from the speaker 18 is distorted.

FIG. 4 shows a conventional clip prevention device CP11.
FIG.

The clip prevention device CP11 has a gain adjustment resistor 31 similar to the gain adjustment resistor 22, and a clip detection circuit 32 provided after the power amplifier circuit 17. Is detected, it automatically acts to increase the resistance value of the gain adjustment resistor 31, the signal level input to the power amplifier circuit 17 is suppressed, and therefore, distortion of the sound output from the speaker 18 is prevented. You.

[0007]

However, in the clip prevention device CP11, the distortion of the sound output from the speaker 18 is prevented, but when the value of the audio input signal decreases, the volume generated from the speaker 18 decreases. There is a problem of being unsatisfactory.

That is, in the above conventional example, the sound volume generated from the speaker 18 is satisfactory even if the value of the audio input signal becomes small. The sound output from the speaker 18 is not distorted even if an audio amplifier in which the sound output from the speaker 18 is distorted or the value of the input signal exceeds a certain level is used. Becomes smaller, there is no other choice but to select an audio amplifier that makes the volume generated from the speaker 18 unsatisfactory. Therefore, even if the value of the audio input signal decreases, the audio signal is generated from the speaker 18. Even if the volume is satisfactory and the value of the input signal exceeds a certain level,
There is a problem that it is not possible to obtain an audio amplifier in which the sound output from the speaker is not distorted.

According to the present invention, even if the value of the audio input signal is small, the volume generated from the speaker is satisfactory, and even if the value of the input signal exceeds a certain level,
An object of the present invention is to provide a clip prevention device in an amplifier capable of obtaining an audio amplifier in which sound output from a speaker is not distorted.

[0010]

According to the present invention, there is provided an audio circuit having an electronic volume for controlling the value of an audio input signal, and a power amplifier circuit for amplifying an output signal of the electronic volume. And a clip prevention device that sets the input level of the power amplification circuit according to the gain of the electronic volume.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a clip prevention device CP1 in an amplifier according to one embodiment of the present invention.

The clip prevention device CP1 comprises an A / D conversion circuit 10, a sample and hold circuit 11,
, Delay circuit 13, multiplier 14, D / A conversion circuit 1
5, an electronic volume 16, a power amplifier circuit 17, and a speaker 18.

The A / D conversion circuit 10 is a circuit for converting an audio input signal into a digital signal. The sample and hold circuit 11 is a circuit for converting a digital audio input signal converted by the A / D conversion circuit 10 into a predetermined unit time. a circuit for holding a peak level iN _p in.

[0014] computing means 12, and the level of the audio input signal, in accordance with the gain G _v of the electronic volume 16, FIG. 2
(IN _p G _v G _a = x). The delay circuit 13 is a circuit for delaying the audio input signal by a time during which the operation is performed by the operation means 12.

The multiplier 14 multiplies the value B of the result calculated by the calculating means 12 by the value of the audio input signal passed through the delay circuit 13. D / A conversion circuit 15
Is a part for converting the output signal of the multiplier 14 into an analog signal.

Next, the operation of the above embodiment will be described.

FIG. 2 is a flowchart showing the operation of the arithmetic unit 12 in the clip prevention device CP1.

[0018] First, initialize the output value B of the arithmetic unit 12 to "1" takes the gain G _a gain G _v and the electronic amplifier circuit 17 of the electronic volume 16 (S1), in a unit time of the audio input signal Is _acquired from the sample hold circuit 11 (S2), and IN _p · G _v · G
By calculating _a = x, the value x is calculated (S
3).

Then, the clip level of the power amplifier circuit 17 is compared with the calculated value x (S4). If the calculated value x is equal to or less than the clip level, the output value B of the calculating means 12 up to that point is obtained. Is added to the output value B, and a value α is added to the output value B.
Is added as a new value B (S11). If the new value B is 1 or more (S12), the value B is maintained at 1 (S13), and the value B is output to the multiplier 14. (S14).

It should be noted that the output value B of the arithmetic
Is added to the new value B (S11).
Is smaller than 1 (S12), the value B is output to the multiplier 14 without changing the value B to 1 (S14).

On the other hand, the clip level of the power amplifier circuit 17 is compared with the value x (S4). If the value x is larger than the clip level, a value obtained by dividing the current clip level of the power amplifier circuit 17 by the value x is used. To the value B (S15),
The value B thus changed is output to the multiplier 14 (S
14).

Then, the value B is output to the multiplier 14 (S
14) Later, the next sampled peak level IN _p
, The above operation (S2 to S15) is repeated.

In the above embodiment, for example, "12 V" is set as the clip level of the power amplifier circuit 17, and "0.
05 "is set and the sample-hold circuit 11 is set to" 100ms ", for example, as a predetermined unit time to detect the peak level IN _p.

In the above embodiment, if the value x is larger than the clip level, the value B is changed to a value obtained by dividing the current clip level of the power amplifier circuit 17 by the value x (S15). Is not distorted, and if the value x is equal to or less than the clip level, the value B multiplied by the input signal in the multiplier 14 is set to "1". Is increased by 0.05, for example, up to the upper limit, so that even when the value of the audio input signal decreases, the volume generated from the speaker 18 is maintained at a satisfactory volume.

That is, according to the above embodiment, even if the value of the audio input signal is small, the volume generated from the speaker 18 is a satisfactory volume, and even if the value of the input signal becomes a certain level or more, The sound output from the speaker 18 is not distorted.

In the above embodiment, the predetermined value α to be added to the clip level and the output value B of the power amplifier circuit 17,
As the predetermined unit time sample-hold circuit 11 detects the peak level IN _p, it may be set to a value other than the value.

Further, in the above embodiment, the peak level of the audio input signal per unit time is adopted as the level of the audio input signal. However, the level of the audio input signal is obtained by another method. You may do so.

[0028]

According to the present invention, even if the value of the audio input signal is small, the volume generated from the speaker is a satisfactory volume, and even if the value of the input signal becomes a certain level or more, the sound from the speaker can be obtained. This produces an effect that the output sound is not distorted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a clip prevention device CP1 in an amplifier according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of a calculator 12 in the clip prevention device CP1.

FIG. 3 is a block diagram showing a conventional amplifier.

FIG. 4 is a circuit diagram showing a conventional clip prevention device CP11.

[Explanation of symbols]

 CP1: an anti-clip device in an amplifier, 11: a sample-and-hold circuit, 12: arithmetic means, 13: a delay circuit, 14: a multiplier, 16: an electronic volume, 17: a power amplifier circuit.

Claims (2)

[Claims] 1. An audio circuit comprising: an electronic volume for controlling a value of an audio input signal; and a power amplifying circuit for amplifying an output signal of the electronic volume, wherein: a level of the audio input signal; A clip prevention device for an amplifier, wherein an input level of the power amplification circuit is set according to the following. 2. The apparatus according to claim 1, wherein the level of the audio input signal is a peak level of the audio input signal in a unit time.