JPH03295307A - Sound signal output device - Google Patents

Abstract

PURPOSE:To prevent the generation of distortion due to clipping of a low frequency component by the dynamic range of a power amplifier output by controlling a base level by the feedback signal of motional feedback. CONSTITUTION:In a sound signal output device provided with a base level control circuit 4 and a sound signal output circuit 5 using the motional feedback(MFB), the base level control circuit 4 is controlled on the basis of the feedback signal of the motional feedback so that the low frequency band of a sound signal is not distorted by the restriction of the supply voltage to the power amplifier. Thus, the distortion due to the clipping of the low frequency band component by the dynamic range of the power amplifier output can be prevented from occurring.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an audio signal output device in electronic equipment or audio equipment equipped with a small-diameter speaker, such as a television receiver, a radio power recorder, etc. More specifically, the present invention relates to an audio signal output device using MFB (Mono-Local Feedback) for widening the low frequency reproduction band of a speaker.

<Conventional technology> In general, with small-diameter speakers, it is difficult to reproduce low frequencies, so MFB is used to widen the low frequency reproduction frequency band by detecting the operating state of the speaker and feeding back to power up. There are cases where it is used.

For example, there is an MPB shown in FIG. 2 in which impedance changes with respect to the frequency of an audio signal applied to a speaker unit are detected as voltage changes and fed back to power up.

In FIG. 2, 1 is an audio signal control circuit, and this audio signal control circuit 2 includes a volume control circuit 2 that controls the volume level, a treble control circuit 3 that controls the level of the high range, and a treble control circuit 3 that controls the level of the high range. Each of the control circuits 2 to 4 is controlled by a volume level control signal, a low/pull level control signal, and a bass level control signal. That is, each control signal is a DC voltage, and the audio signal is amplified or attenuated depending on the level of this DC voltage.

5 is an audio signal output circuit, and this audio signal output circuit 5
includes an adder circuit 6 that adds the audio signal from the audio signal control circuit l and a low-frequency audio signal as a feedback signal fed back, and an adder circuit 6 that amplifies the audio signal from the adder circuit 6 and outputs it to the speaker 8. A power-up 7, a detection resistor 9, an amplifier circuit 10 for amplifying the audio signal obtained by the detection resistor 9, and a power-up circuit 10 for amplifying the audio signal obtained by the detection resistor 9. A bandpass filter 11 is provided to supply the adder circuit 6.

In general, the impedance of a speaker is not constant;
The impedance varies depending on the frequency, and as shown in the impedance characteristics in FIG. 3, the impedance is high at the lowest resonance frequency f, and the impedance is higher at the lowest resonance frequency r. Yamagata is centered on . Therefore, even if the power-up 7 performs constant voltage amplitude driving regardless of the frequency, the audio signal voltage obtained by the detection resistor 9 described above has a voltage characteristic that is inversely proportional to the impedance characteristic of the speaker 8.

The audio signal obtained by this detection resistor 9 is amplified and only the low frequency components below the lowest resonance frequency f0 are extracted and added to the adder circuit 6.
Since the output of the power-up 7 has a frequency characteristic in which only the low frequency range is amplified, the lowest resonant frequency f of the speaker 8. The following frequency bands,
That is, it becomes possible to widen the low frequency reproduction frequency band.

<Problem to be solved by the invention> However, since the rated output of the small-diameter speaker 8 is limited, the power supply voltage of the power-up 7 is also limited, and the volume level cannot be adjusted close to the upper limit. In such a case, there is a problem in that the low frequency components amplified by the MFB or the output dynamic range due to the power supply voltage of the power-up 7 are clipped and distortion is likely to occur.

The present invention has been made in view of the above points, and includes M.
It is an object of the present invention to prevent clipping distortion of low frequency components from occurring in an audio signal output device using FB.

Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention is configured as follows.

That is, the present invention includes a bass level control circuit that controls the low-frequency level of an input audio signal, and amplifies the audio signal from this bass level control circuit by powering up and outputs it to a speaker. An audio signal output device comprising an audio signal output circuit using an MFB (motional feedback) that widens a low frequency reproduction band by detecting an operating state and feeding back to the power-up, the feedback signal of the MFB being Based on this, the bass level control circuit is controlled so that the low frequency range of the audio signal is not distorted due to the limitation of the power supply voltage for power-up.

<Operation> According to the above configuration, since the bass level is controlled by the feedback signal of M F B, some components may be clipped in the low frequency layer 6 due to the output dynamic range of power-up, causing distortion. Is it possible to prevent this?

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
Portions corresponding to the conventional example in the figures are given the same reference numerals.

This audio signal output device is included in, for example, a radio cassette tape recorder.

In FIG. 1, l is an audio signal control circuit, and this audio signal control circuit l is equipped with a volume control circuit 2, a treble level control circuit 3, and a bass level control circuit 4, and each circuit 2 to 4 is , DC voltage volume level control signal,
It is controlled by a treble level control signal and a bass level control signal.

The audio signal output circuit 5 includes an adder circuit 6 that adds the audio signal from the audio signal control circuit 1 and the feedback low-frequency audio signal, and amplifies the audio signal from the adder circuit 6 and outputs it to the speaker 8. A power-up circuit 10, a detection resistor 9, an amplifier circuit 10 for amplifying the audio signal obtained by the detection resistor 9, and a power-up circuit 10 for amplifying the audio signal obtained by the detection resistor 9; and a bandpass filter 11 which is applied to the adder circuit 6.

The above configuration is similar to the conventional example shown in FIG.

In this embodiment, in order to prevent low frequency components from being clipped and distorted by the output dynamic range of the power-up 7, based on the feedback signal of the MPB,
It is configured to control the bus level control circuit 4.

That is, the feedback signal from bandpass filter II is
It is converted into a DC voltage according to the feedback level by the AC-DC conversion circuit I2, and this DC voltage is applied to the inverting input of the calculation circuit 13.
The above-mentioned bus level control signal is applied to the non-inverting input of 3, and the bus level control circuit 4 is controlled by the output of this arithmetic circuit 13, so that low frequency components are amplified or attenuated. .

This arithmetic circuit 13 controls the bus level control circuit 4 regardless of the level of the bus level control signal when the level of the DC voltage from the AC-DC converter circuit 12 exceeds a certain level, thereby reducing the low frequency range. It is designed to reduce the level of only the frequency components. That is, when the output dynamic range of the power-up 7 is at such a level that the low frequency component is clipped, the bass level control circuit 4 lowers the level of the low frequency component to prevent clip distortion from occurring. Further, this arithmetic circuit I3 outputs a control signal corresponding to the bus level control signal l to the bus level control circuit 4 when the DC voltage level from the AC-DC conversion circuit 12 is less than the certain level. It has become.

When the arithmetic circuit 13 operates in this way and the bass level control circuit 4 lowers the level of the low frequency component, the result is that the low frequency component is not amplified relative to the middle and high frequency components. Arithmetic circuit 1
3 is operating, that is, when there is input of low frequency components that exceed the output range of Power Up 7, the attenuation amount of the volume control circuit 2 is small and the volume level is at the upper limit. - In boat fishing, as is known as the equal loudness curve, when the volume level is increased1, even if the amplification effect of the low frequency components is reduced, it feels audible. Never.

<Effects of the Invention> As described above, according to the present invention, the low frequency reproduction band can be expanded by the MFB, and the bass level is controlled by the feedback signal of the MFB. The range prevents low frequency components from being clipped and causing distortion.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional example, and FIG. 3 is a diagram showing the innovation characteristics of a speaker. ■ Audio signal control circuit, 4 Bus level control circuit, 5
Audio signal output circuit, 7 Power up.

Claims (1)

[Claims] (1) A bass level control circuit that controls the low-frequency level of the input audio signal, and amplifies the audio signal from this bass level control circuit by powering up and outputs it to the speaker, and also controls the operating state of the speaker. An audio signal output device comprising an audio signal output circuit using an MFB (motional feedback) that widens a low frequency reproduction band by detecting and feeding back to the power-up, The audio signal output device is characterized in that the bass level control circuit is controlled so that the low frequency range of the audio signal is not distorted due to the power-up power supply voltage limitation.