JPH067313U - Bus control circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a bus control circuit for automatically controlling the low-frequency level of an audio signal. [Structure] The audio signal Sin is input to the tone control circuit 1 and the LPF 11. LPF11 to smoothing circuit 14
Detects the low-frequency level of the audio signal Sin and outputs the low-frequency level detection signal S1. The adder circuit 16 adds the low-frequency level detection signal S1 and the control voltage S2 set by the user and outputs a control voltage S3. The control voltage S3 is supplied to the tone control circuit 1 via the limiter circuit 17. The tone control circuit 1 controls the low-frequency level of the audio signal Sin according to the control voltage S3, and outputs the audio signal Sout.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a bus control circuit for controlling a low tone (bus) of an audio signal in a television receiver, an audio device or the like.

[0002]

[Prior art]

 Conventionally, in a television receiver, an audio device, etc., a tone control circuit is used to control a low tone (bus) of an audio signal. It is common to apply a DC voltage to the control terminal provided in the tone control circuit and vary the DC voltage to control the bass level.

FIG. 4 is a block diagram showing an example of a conventional bus control circuit using a tone control circuit. In FIG. 4, the left and right (L, R) audio signals are input to the tone control circuit 1. The control terminal of the tone control circuit 1 is supplied with a control voltage set by the user by the control voltage generating circuit 2, and the low frequency level of the input audio signal is amplified (emphasized) according to this control voltage. The bass control circuit including the tone control circuit 1 and the control voltage generation circuit 2 controls the level of the low frequency band of the audio signal, the power amplifier 3 amplifies the signal, and the sound is then emitted from the speakers 4 and 4.

FIGS. 5A and 5B are circuit diagrams showing a specific configuration example of the control voltage generation circuit 2. In the circuit shown in FIG. 5A, the reference voltage from the reference power source is adjusted by the variable resistor 5 to obtain the control voltage. The circuit shown in FIG. 5B changes the duty of the pulse supplied from the microcomputer and smoothes the pulse by the smoothing circuit of the resistor 6 and the capacitor 7 to obtain the control voltage.

[0005]

In the above-described conventional bass control circuit, the bass (low frequency) level is fixed in a state set by the user, so that the bass of the audio signal is emphasized at a constant level. Therefore, when the bass level of the input audio signal is high, or conversely, when the bass level is low, the user has to set the bass level each time. The present invention has been made in view of the above problems, and automatically suppresses the level of an input audio signal when the low frequency level is large, and conversely, when the level is low, the level is automatically suppressed. The aim is to provide a bus control circuit that emphasizes.

[0006]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems of the conventional technology, the present invention provides a tone control circuit for controlling and outputting a low frequency level of an input voice signal and a low frequency level of the input voice signal. A low-frequency level detection circuit that detects and outputs a low-frequency level detection signal corresponding to the low-frequency level of the input audio signal; the low-frequency level detection signal and a first control voltage set by the user. Is added to output a second control voltage, the second control voltage is supplied to the tone control circuit, and the input audio signal of the input audio signal is supplied in accordance with the second control voltage. The present invention provides a bus control circuit characterized by being configured to control the level of a low frequency band.

[0007]

【Example】

 The bus control circuit of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of the bus control circuit of the present invention, FIG. 2 is a circuit diagram showing a specific configuration of FIG. 1, and FIG. 3 is a waveform diagram for explaining the bus control circuit of the present invention. . In FIG. 1, the same parts as those in FIG. 4 are designated by the same reference numerals.

In FIG. 1, the input audio signal Sin is input to the tone control circuit 1. Here, as shown in FIG. 4, the audio signal is not divided into two systems of left and right signals, but is shown only in one system. The input audio signal Sin is also input to the low pass filter (LPF) 11. As shown in FIG. 2, the LPF 11 is composed of resistors R111 to R116, capacitors C111 to C114, and an operational amplifier 111. The LPF 11 is a third-order low-pass filter whose cutoff frequency is set to about 100 Hz, and the LPF 11 detects a low-frequency signal of 100 Hz or less.

The output of the LPF 11 is input to the amplifier 12 and amplified to a level at which the rectifier circuit 13 in the subsequent stage operates sufficiently. As shown in FIG. 2, the amplifier 12 includes resistors R121 to R125, capacitors C121 to C123, and an operational amplifier 121. The rectifier circuit 13 is composed of a resistor R131 and diodes D131 and D132. The signal output from the amplifier 12 is rectified by the diodes D1 31 and D132 of the rectifier circuit 13. The output of the rectifier circuit 13 is input to the smoothing circuit 14. As shown in FIG. 2, the smoothing circuit 14 is composed of resistors R141 and R142 and a capacitor C141. The resistor R141 and the capacitor C141 are a low-pass filter and have a large time constant. The signal input to the smoothing circuit 14 is output as a DC voltage S1. This DC voltage S1 is a low-frequency level detection signal that decreases when the low-frequency level of the audio signal Sin rises and increases when the low-frequency level of the audio signal Sin decreases. Therefore, the LPF 11 to the smoothing circuit 14 are detection circuits that detect the low-frequency level of the input audio signal Sin.

The DC voltage S1 output from the smoothing circuit 14 is input to the amplifier 15 and amplified. As shown in FIG. 2, the amplifier 15 is composed of a resistor R151 and an operational amplifier 151. The output of the amplifier 15 is input to the adder circuit 16. As shown in FIG. 2, the adder circuit 16 is composed of resistors R161 to R163, a capacitor C161, and an operational amplifier 161. The control voltage S2 set by the user by the control voltage generation circuit 2 is input to the adder circuit 16. The adder circuit 16 adds the DC voltage input from the amplifier 15 and the control voltage S2 and outputs a control voltage S3.

The output of the adder circuit 16 is input to the limiter circuit 17. As shown in FIG. 2, the limiter circuit 17 is composed of resistors R171 to 175, a capacitor C171, and an NPN transistor Q171. Since the output of the adder circuit 16 is input to the control terminal of the tone control circuit 1 as a result, the limiter circuit 17 prevents the overvoltage from being applied to the control terminal of the control circuit 1. Although not shown in FIG. 1, as shown in FIG. 2, the transistor Q171 of the limiter circuit 17 turns on the operation of the LPF11 to the limiter circuit 17 provided by the present invention via the resistor R175. A control signal for turning off is supplied. When the control signal is low, the LPF11 to limiter circuit 17 operates, and when the control signal is high, the LPF11 to limiter circuit 17 does not operate.

Then, the tone control circuit 1 amplifies (emphasizes) the input audio signal Sin according to the control voltage input from the limiter circuit 17, and outputs the audio signal Sout. The bass control circuit of the present invention thus constructed controls the low-frequency level of the voice signal, which is amplified by the power amplifier 3 and then emitted from the speaker 4. Note that Vcc in FIG. 2 is a reference voltage.

Further, description will be made with reference to the waveform diagram of FIG. 3A to 3D, the horizontal axis represents time t. The waveform shown by the solid line in FIG. 3 (A) shows the change in level of the audio signal Sin at a certain low frequency. By the circuit operation described above, from the smoothing circuit 14, as shown in FIG. 3 (B), when the low frequency level of the audio signal Sin increases, it decreases, and the low frequency level of the audio signal Sin decreases. When it does, the rising DC voltage S 1 is output. FIG. 3C shows the control voltage S2 set by the user, and shows the state where the user raises the control voltage S2 in the middle. FIG. 3D shows the control voltage S3 obtained by adding the DC voltage S1 and the control voltage S2 by the adder circuit 16. Note that in FIGS. 3B to 3D, the vertical axis represents the voltage V.

Since the control voltage S3 output from the adder circuit 16 is supplied to the tone control circuit 1 via the limiter circuit 17, the waveform shown by the solid line in FIG. Controlled as. As a result, the level of the low frequency range of the audio signal Sout output from the tone control circuit 1 is suppressed when the level is high, and conversely, the level is emphasized when the low frequency level is low. As a result, even if the low frequency level fluctuates, the low frequency level of the audio signal is emphasized within a substantially constant range, and the user changes the low frequency level each time the low frequency level changes. No need to set.

[0015]

[Effect of device]

 As described above in detail, the bus control circuit of the present invention detects the low frequency level of the input voice signal and adds the low frequency level detection signal and the first control voltage set by the user. Since the second control voltage is supplied to the tone control circuit to control the low frequency level of the input audio signal, the low frequency (low frequency) of the input audio signal is high when the level is high. The level is automatically suppressed, and conversely, when the level is low, the level is automatically emphasized, and as a result, the low frequency level of the audio signal is emphasized within a substantially constant range. The inconvenience that the user has to set the low frequency level each time the level changes is eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment.

FIG. 2 is a specific circuit diagram of FIG.

FIG. 3 is a waveform diagram for explaining an example.

FIG. 4 is a block diagram showing a conventional example.

5 is a circuit diagram showing a specific configuration example of a control voltage generation circuit 2 in FIG.

[Explanation of symbols]

 1 Tone Control Circuit 3 Power Amplifier 4 Speaker 11 Low Pass Filter (Low Frequency Level Detection Circuit) 12 Amplifier (Low Frequency Level Detection Circuit) 13 Rectifier Circuit (Low Frequency Level Detection Circuit) 14 Smoothing Circuit (Low Frequency Level Detection Circuit) 15 Amplifier 16 adder circuit 17 limiter circuit

Claims (1)

[Scope of utility model registration request] 1. A tone control circuit for controlling and outputting a low-frequency level of an input audio signal, and a low-frequency level of the input audio signal for detecting a low-frequency level of the input audio signal. And a low-frequency level detection circuit that outputs a low-frequency level detection signal according to the level, and an addition that outputs the second control voltage by adding the low-frequency level detection signal and the first control voltage set by the user. And a circuit for supplying the second control voltage to the tone control circuit and controlling the level of the low frequency band of the input audio signal according to the second control voltage. Bus control circuit.