JP2002171592A - Voice input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voice input device that detects no presence of electric conduction but insertion of a plug. SOLUTION: A test signal outputted from an oscillator 154 is fed to an amplifier 148 via a resistor 150. A BPF 156 extracts a test signal component from an output of the amplifier 148. A level detection circuit 158 detects an output level of the BPF 156 and informs a control circuit 168 about the result of detection. When the control circuit 168 detects that an output of the level detection circuit 158 is a prescribed level or below, the control circuit 168 discriminates that an electric device is connected to an R channel input terminal 146 and allows a selector 162 to select a trap filter 160. The trap filter 160 eliminates the test signal component from an output of the amplifier 148 and the output of the filter 160 is fed to an R channel output terminal 166 via the selector 162 and a buffer 164.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a voice input device.

[0002]

2. Description of the Related Art FIG. 3 is a schematic block diagram of a conventional stereo-compatible audio input device. Reference numeral 110 denotes an L-channel RCA input terminal, and reference numeral 112 denotes an R-channel RCA input terminal. The buffer amplifier 114 is connected to the input terminal 110
, And the buffer amplifier 116 amplifies the audio signal from the input terminal 112. The output of the buffer amplifier 114 is applied to the L channel output terminal 118 and one input of the selector 120. The output of the buffer amplifier 116 is applied to the other input of the selector 120. The buffer 122 applies the output of the selector 120 to the R channel output terminal 124.

The input terminal 112 of the R channel is provided with means for detecting whether a plug is inserted. That is, when the plug is inserted, the GN of the plug is
The detection terminal 126 is connected to the GND terminal 1 by the metal part of the D terminal.
28, and the detection terminal 126 is at the GND level.
When the plug is not inserted, the detection terminal 126 is GN
It does not become conductive with the D terminal, and the power supply V
Pulled up to cc. The DC level detection circuit 132 detects the DC level of the detection terminal 126 and outputs a detection result to the control circuit 134. The control circuit 134 controls the selector 120 according to the output of the DC level detection circuit 132. That is, the control circuit 134 outputs the R channel input terminal 1
When a plug is inserted in the selector 12, the selector 12
0 causes the output of the buffer amplifier 116 to be selected, and if no plug is inserted into the R channel input terminal 112, the selector 120 selects the output of the buffer amplifier 114.

[0004]

In the conventional example, a plug insertion detecting means must be provided at the R channel input terminal 110, and there is a problem that usable input terminals are limited.

An object of the present invention is to provide a stereo-compatible audio input device that outputs an L-channel input signal to an R-channel output in a state where only an L-channel input is connected even if the input terminal does not have a connection detection function. Aim.

[0006]

[Means for Solving the Problems]

The audio input device according to the present invention further comprises first and second audio input means for receiving audio signals of a first channel and a second channel of a stereo audio signal, respectively. A first amplifier for amplifying the audio signal of the first amplifier, first audio output means connected to the output of the first amplifier, a second amplifier for amplifying the audio signal from the second audio input means, Test signal output means for applying a test signal via a predetermined resistor between the second audio input means and the input of the second amplifier, and suppressing a component of the test signal from the output of the second amplifier A suppressor, a selector for selecting one of the output of the first amplifier and the output of the suppressor, a second audio output unit connected to the output of the selector, and the test from the output of the second amplifier. signal A test signal extracting means for extracting a component, a level detecting means for detecting an output level of the test signal extracting means, a comparison for comparing an output of the level detecting means with a predetermined reference level, and controlling the selector according to the comparison result And control means for performing the control.

The voice input device according to the present invention further comprises a switch for selectively connecting the test signal output means to the predetermined resistor, and the suppressing means outputs the test signal from the output of the second amplifier. A selective suppression means for selectively suppressing a component, wherein the control means, when connecting the test signal output means to the predetermined resistor, causes the suppression means to output the test signal at the output of the second amplifier. Suppress components.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram of a first embodiment of the present invention. 140 is an L-channel audio input terminal, 142 is an amplifier for amplifying the input audio of the audio input terminal 140, and 144 is an L-channel output terminal.

Reference numeral 146 denotes an R channel audio input terminal;
Reference numeral 48 denotes an amplifier for amplifying the input sound of the audio input terminal 146. The input of the amplifier 148 is also connected to GND via the resistor 150 and the oscillator 154. That is, the oscillator 1
The test signal output from 54 is applied to audio input terminal 146 and amplifier 148 via resistor 150.

Reference numeral 156 denotes a band pass filter (BPF) for extracting a test signal component from the output of the amplifier 148;
8 is a level detection circuit for detecting the level of the test signal component output from the BPF 156, and 160 is an amplifier 148
162 is a selector for selecting the output of the amplifier 142 or the output of the trap filter 160, 164 is the selector 1
This is a buffer for applying the output of R to the R channel output terminal 166. A control circuit 168 controls the selector 162 according to the output of the level detection circuit 158.

The frequency of the test signal is set lower than the upper limit of the frequency band of the electric equipment connected to the input terminal 146. When the upper limit of the frequency band at the output of the output terminal 166 of this embodiment can be set lower than the test signal frequency, a low-pass filter for removing the test signal component may be provided instead of the trap filter 160. Setting the frequency of the test signal to a frequency higher than the audible frequency band does not adversely affect the input voice.

The operation of the embodiment shown in FIG. 1 will be described. The audio signal of the L channel is input from an input terminal 140 to an amplifier 142.
, And is amplified and applied to the audio output terminal 144 and one input of the selector 162.

The test signal output from the oscillator 154 is applied to the amplifier 148 via the resistor 150. Amplifier 14
When an electrical device (generally, an audio output device) is connected to the R channel input terminal 146, the test signal level applied to the R. 8 is the resistance value of the resistor 150, the output impedance of the electrical device, and Determined by the input impedance of the amplifier 148, the R channel input terminal 1
If no electrical device is connected to 46, the resistance 150
And the input impedance of the amplifier 148. Therefore, by detecting the level of the test signal component at the output of the amplifier 148, it can be determined whether or not an electric device is connected to the R channel input terminal 146.

The BPF 156 extracts a test signal component from the output of the amplifier 148, and the level detection circuit 158
The output level of F156 is detected, and the detection result is notified to the control circuit 168. When the control circuit 168 detects that the output of the level detection circuit 158 is equal to or less than a predetermined value, it determines that an electric device is connected to the R channel input terminal 146 and selects the trap filter 160 for the selector 162. Let it. The trap filter 160 removes the test signal component from the output of the amplifier 148, and the output is applied to the R channel output terminal 166 via the selector 162 and the buffer 164.

When an electric device is not connected to the R channel input terminal 146, the impedance becomes extremely high when the outside is viewed from the R channel input terminal 146. Therefore, the test signal output from the oscillator 154 is input to the amplifier 148 with almost no attenuation. BPF1
56 extracts a test signal component from the output of the amplifier 148, and the level detection circuit 158 detects the output level of the BPF 156. The test signal level at the output of the BPF 156 is higher when an electric device is not connected to the R channel input terminal 146 than when an electric device is connected to the R channel input terminal 146. When the test signal level detected by the level detection circuit 158 becomes higher than a predetermined value, the control circuit 168 selects the selector 1
Let 62 select the output of the amplifier 142. This allows
The output of the amplifier 142 (L channel audio signal) is also output from the R channel output terminal 166.

As described above, in the embodiment shown in FIG. 1, it is possible to electrically detect the presence or absence of connection to the R channel input terminal without providing a means for detecting the plug insertion by the presence or absence of conduction in the R channel input terminal. If there is no R channel input, the L channel input can be supplied to the R channel output terminal.

FIG. 2 is a schematic block diagram of a second embodiment of the present invention. This embodiment corresponds to a stereo input.

Reference numeral 240 denotes an L channel audio input terminal;
Reference numeral 42 denotes an amplifier for amplifying the input sound of the sound input terminal 240, and reference numeral 244 denotes an L-channel output terminal.

Reference numeral 246 denotes an R channel audio input terminal;
Reference numeral 48 denotes an amplifier for amplifying the input sound of the audio input terminal 246. The input of the amplifier 248 is connected directly to GND via the resistor 250 and the selector 252 or to GND via the oscillator 254. That is, the test signal output of the oscillator 254 can be selectively applied to the input of the amplifier 248 by the selector 252.

Reference numeral 256 denotes a band-pass filter (BPF) for extracting a test signal component from the output of the amplifier 248;
Reference numeral 8 denotes a level detection circuit for detecting the audio output level of the amplifier 248 and the level of the test signal output from the BPF 256; 260, a trap filter for removing a test signal component from the output of the amplifier 248;
A selector 264 for selecting the output of the trap filter 260 or the output of the trap filter 260 is a buffer for applying the output of the selector 262 to the R channel output terminal 266. 268 is
A control circuit that controls the trap filter 260, the selector 262, and the selector 252 according to the output of the level detection circuit 258.

The frequency of the test signal is set lower than the upper limit of the frequency band of the electric device connected to the input terminal 246. If the upper limit of the frequency band at the output of the output terminal 266 of this embodiment can be set lower than the test signal frequency, the trap filter 260 may always be trap-on. If the frequency of the test signal is set to a frequency higher than the audible frequency band, there is no adverse effect on the input voice.

The operation of the embodiment shown in FIG. 2 will be described. Initially, the selector 252 selects GND, and the selector 2
62 selects the output of the trap filter 260, and the level detection circuit 258 detects and monitors the output level of the amplifier 248.

The audio signal of the L channel is supplied to an input terminal 240
To the amplifier 242, where it is amplified and applied to the audio output terminal 244 and one input of the selector 262.

The level detection circuit 258 monitors the output level of the amplifier 248 and outputs the result to the control circuit 268. When the control circuit 268 detects from the output of the level detection circuit 258 that the R-channel input terminal 246 has no signal for a certain period of time, the control circuit 268 sets the selector 252 for a certain period of time.
Is switched to the oscillator 254 side, and the detection target of the level detection circuit 258 is switched to the output of the BPF 256. The switching of the selector 252 causes the test signal output of the oscillator 254 to be applied to the amplifier 248 via the resistor 250.

When an electric device (generally, an audio output device) is connected to the R channel input terminal 246, the test signal level applied to the amplifier 248 is
50, determined by the output impedance of the electrical device and the input impedance of the amplifier 248,
When an electric device is not connected to the R channel input terminal 246, it is determined by the resistance value of the resistor 250 and the input impedance of the amplifier 248. Therefore, by detecting the level of the test signal component at the output of the amplifier 248, it can be determined whether or not an electric device is connected to the R channel input terminal 246.

The BPF 256 extracts a test signal component from the output of the amplifier 248, and the level detection circuit 258
The output level of F256 is detected, and the detection result is notified to the control circuit 268. When the control circuit 268 detects that the output of the level detection circuit 258 is equal to or lower than a predetermined value, it determines that an electric device is connected to the R channel input terminal 246 and selects the trap filter 260 by the selector 262. Let it. The trap filter 260 removes the test signal component from the output of the amplifier 248, and the output is applied to the R channel output terminal 266 via the selector 262 and the buffer 264.

When the test signal is being applied to the amplifier 248, the control circuit
When the test signal removal function at 60 is enabled and the test signal is not applied to the amplifier 248, the pass characteristic of the trap filter 260 is flattened in all bands. If the test signal frequency does not affect the input audio signal, such processing of the trap filter 260 is unnecessary.

When an electric device is not connected to the R channel input terminal 246, the impedance becomes extremely high when the outside is viewed from the R channel input terminal 246. Therefore, the test signal output from the oscillator 254 is input to the amplifier 248 with little attenuation. BPF2
56 extracts a test signal component from the output of the amplifier 248, and the level detection circuit 258 detects the output level of the BPF 256. The test signal level at the output of the BPF 256 is higher when the electric device is not connected to the R channel input terminal 246 than when the electric device is connected to the R channel input terminal 246. When the test signal level detected by level detection circuit 258 becomes higher than a predetermined value, control circuit 268 selects selector 2
62 causes the output of the amplifier 242 to be selected. This allows
The output of the amplifier 242 (L channel audio signal) is also output from the R channel output terminal 266.

As described above, in the embodiment shown in FIG. 2, the presence / absence of connection to the R channel input terminal is electrically detected without providing a means for detecting plug insertion by the presence / absence of conduction in the R channel input terminal. If there is no R channel input, the L channel input can be supplied to the R channel output terminal.

[0032]

As can be easily understood from the above description, according to the present invention, even if the means for detecting the plug insertion based on the presence / absence of electrical continuity is not provided at one input terminal, the electrical connection can be established. Presence or absence can be detected. As a result, for example, R
When there is no channel input, L channel output terminal
A channel input can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a first embodiment of the present invention.

FIG. 2 is a schematic configuration block diagram of a second embodiment of the present invention.

FIG. 3 is a schematic configuration block diagram of a conventional example.

[Explanation of symbols]

 110: L channel input terminal 112: R channel input terminal 114, 116: Buffer amplifier 118: L channel output terminal 120: Selector 122: Buffer 124: R channel output terminal 126: Detection terminal 128: GND terminal 130: Resistance 132: DC Level detection circuit 134: Control circuit 140: L channel audio input terminal 142: Amplifier 144: L channel output terminal 146: R channel audio input terminal 148: Amplifier 150: Resistance 154: Oscillator 156: Band pass filter (BPF) 158: Level Detection circuit 160: Trap filter 162: Selector 164: Buffer 166: R channel output terminal 168: Control circuit 240: L channel audio input terminal 242: Amplifier 244: L channel output terminal 246 R channel audio input terminal 248: amplifier 250: resistance 252: Selector 254: oscillator 256: bandpass filter (BPF) 258: level detecting circuit 260: trap filter 262: Selector 264: Buffer 266: R channel output terminal 268: the control circuit

Claims (2)

[Claims] 1. First and second audio signals of a first channel and a second channel of a stereo audio signal, respectively, are inputted.
Voice input means, and a first amplifying a voice signal from the first voice input means.
Amplifier, first audio output means connected to the output of the first amplifier, and second amplifier for amplifying the audio signal from the second audio input means
A test signal output means for applying a test signal via a predetermined resistor between the second audio input means and the input of the second amplifier; and an output of the test signal from the output of the second amplifier. Suppression means for suppressing a component; a selector for selecting one of the output of the first amplifier and the output of the suppression means; second audio output means connected to the output of the selector; Test signal extracting means for extracting the component of the test signal from the output, level detecting means for detecting the output level of the test signal extracting means, and comparing the output of the level detecting means with a predetermined reference level. Control means for controlling the selector according to the result. And a switch for selectively connecting the test signal output means to the predetermined resistor, wherein the suppression means selectively suppresses a component of the test signal from an output of the second amplifier. 2. The selective suppression means, wherein the control means causes the suppression means to suppress a component of the test signal in an output of the second amplifier when the test signal output means is connected to the predetermined resistor. The voice input device according to claim 1.