KR890007295Y1 - Control circuit of audio signal output by external noise - Google Patents

Abstract

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Description

Voice output control circuit by external noise

1 is a block diagram according to the present invention.

2 is a detailed circuit diagram of one embodiment of the FIG.

* Explanation of symbols for main parts of the drawings

10: microphone 20, 60: 1-2 amplifier circuit

30: integrating circuit 40: noise level determining circuit

50: switching noise control circuit 70: switching control circuit

The present invention relates to a volume automatic control circuit, and more particularly to a circuit for automatically controlling the volume level of the audio to listen in accordance with the level of external noise.

Conventionally, when listening to audio sound, the audio volume of a device that simply outputs the audio sound is adjusted to an appropriate volume in the current state, and when the listening is uneven due to external noise, the audio level is artificially raised again. Therefore, when irregular noise is intermittently generated, the user has to inconvenience the volume level.

Therefore, it is an object of the present invention to provide a circuit for detecting a sound (noise) generated from the outside and directing the DC, and amplifying the level of the voice by amplifying the output of the voice signal according to its level.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram according to the present invention, and the microphone 10 for converting external noise (here, all audio signals) into an electrical signal, and only the AC signal among the electrical signals output from the microphone 10. The first amplification circuit 20 to amplify, the amplification signal of the first amplification circuit 20 is half-wave rectified and starch, and the integrated circuit 30 called DC leveling, and the DC leveled noise signal with a predetermined reference level. A noise level determining circuit 40 for comparing and outputting a 1-2 logical signal for determining a level of the noise signal, a second amplifying circuit 50 for amplifying the audio signal output from the audio device to a predetermined level; A switching drive 60 which is switched according to the level state of the output first logical signal and outputs an output audio signal or a predetermined amplified audio signal of an audio device to a speaker driving stage, and a level state of the output second logic signal. According to the switch And a switching control signal 70 for adjusting the amplification degree of the second amplification circuit 50. The ASI terminal is an audio signal input terminal output from an audio device, and the NSI external noise input terminal is a noise signal input terminal. ASO is the output stage of the amplified audio signal.

Assuming that the initial noise signal is lower than the set reference level of the noise level determination circuit 40, the 1-2 logic signals are output as "low" level signals, respectively, and the audio signals inputted to the audio channel input terminal ASI are switched. By the operation of the drive 60 is output to the direct speaker driving stage (ASO).

When a predetermined noise is input to the noise signal input terminal while the audio signal is output to the output terminal ASO as described above, it is converted into an electrical signal by the operation of the microphone 10 and input to the first amplification circuit 20. .

Accordingly, the noise signal is amplified by the amplifying operation of the first amplification circuit 20 and input to the integrating circuit 30. The amplified noise is thus input to the noise level determining circuit 40 at a predetermined DC level. .

At this time, the noise level determining circuit 40 determines the 1-2 logical signal according to the noise level by comparing the input noise level with a predetermined reference voltage level. When the noise is a predetermined level, only the first logical signal is “high. "When the level is higher than or equal to the predetermined level, the two levels of the 1-2 logic signal become" high "and" high "states and are output to the switching drive 60 and the switching control circuit 70.

If it is assumed that the noise level determination circuit 40 outputs only the first logic signal in the "high" state, the switching drive 60 is switched to output the audio signal amplified by the second amplification circuit 50 to the speaker driving stage. Output to the audio signal output terminal (ASO).

Therefore, when the noise input to the input terminal NSI is the noise of a predetermined level, it can be seen that the signal in which the audio signal is also amplified is output.

If the electrical signal of the noise output from the microphone 10 is increased during continuous operation as usual, and the 1-2 logic signal of the noise level determination circuit 40 is output as "high" and "high", the switching control circuit 70 is switched to output the amplification control to the second amplification control circuit 50.

Accordingly, the second amplification circuit 50 amplifies the signal output from the audio input terminal ASI by the amplification control signal twice and outputs the signal to the switching drive 60 so that the signal amplified and amplified is output to the output terminal ASO.

FIG. 2 is a detailed circuit diagram of one embodiment of the block diagram of FIG. 1, and includes a microphone 10, a first amplifier circuit 20 configured with resistors R1-R4, capacitors C1-C2, transistors Q1, A noise level determination circuit 40 composed of a diode D1, a resistor R5, and a capacitor C3, and a resistor R6-R9 and a comparator OP1-OP2. A second amplifying circuit 50 composed of R10-R13, capacitors C4-C5, and transistors Q2, a switching drive 60 composed of an analog switch (ASW) and speaker drive (6), and a resistor ( And a switching control circuit 70 composed of R14-R16 and a transistor Q2.

Therefore, in the state in which the audio signal is input to the base of the transistor Q2 through the contact signal a and the capacitor C4 of the analog switch ASW and the audio signal is input to the audio signal input terminal ASI. When a predetermined noise signal is input to the microphone (Mic) 10, the noise signal is converted into an electrical signal and input to the coupling capacitor C1.

The alternating current signal (noise) by the capacitor C1 is input to the base of the transistor Q1 by being overlapped with the voltage divided by the resistors R1-R2, and thus the collector of the transistor Q1 1) amplified by A

The noise signal amplified as shown in Equation 1 is half-wave rectified by the diode D1 through the coupling capacitor C2, and becomes a constant DC level by the constant of the resistor R5 and the capacitor C3, and thus the comparators OP1-OP2. Are input to the non-inverting terminals (+) of

Resistor R6-R7 is connected in series to the non-inverting terminal (-) of the comparator OP1 and inputs the voltage of the resistance divided output (V1) at the node point as a reference voltage as shown in Equation (2) below. To the inverting terminal (-) of OP2), the resistor R8-R9 divides the resistance and inputs the voltage (V2) that is divided into the divided voltages as shown in the following equation (3) to integrally output the resistor R5 and the capacitance C3. Compare the noise signal level.

At this time, since the voltage across the capacitor C3 is proportional to the external noise level, the voltages V1 and V2 input to the inverting terminal (-) of the comparators OP1 and OP2 as comparison voltages are as follows. Should be set to the same voltage as

Setting of the voltage V1: When the audio signal input to the input terminal ASI is required to be amplified in one step in proportion to the voltage applied to the capacitor C3.

Setting of the voltage V2: When the voltage across the capacitor C3 is increased and the audio signal input to the input terminal ASI is required to be amplified more than one step.

Therefore, when the amount of noise input to the noise input terminal NSI is less than the reference voltage V1 input to the inverting terminal (-) of the comparator OP1, the comparator OP1 and OP2 generate the 1-2 logical signal. Each of them outputs as "low", which causes the analog switch (ASW) to remain switched to the contact point (a) so that the signal input from the audio signal input terminal (ASI) can be directly output from the speaker driver. 6) Drive to output terminal (ASO).

As described above, if the noise signal input to the noise input terminal NSI increases while the audio signal is being listened to through the audio output terminal ASO directly through a speaker (not shown), the amplification is performed at the collector of the transistor Q1. The noise that is increased is increased.

Therefore, when the voltage between both ends of the capacitor C3 is increased by the resistor R5 and the capacitor C3, and the voltage of the capacitor C3 increases above the voltage V1 of the above-described second equation, the comparator OP1 sets the first logic signal to "high". By driving the analog switch ASW, the contact point of the switch ASW is switched to (b).

The audio signal inputted to the speaker drive 6 by the switching operation of the analog switch ASW is amplified by the first stage and the audio signal amplified by a predetermined amount than the signal before the noise is input to the output terminal ASO. Is output.

That is, the audio signal input from the audio signal input terminal ASI and the direct current is removed through the capacitor C4 is superimposed on the voltage divided by the resistors R10 and R11 and input to the base of the transistor Q2. As a result, the speaker has amplification gain (G1) as shown in Equation (4) and drives the signal outputted by the collector in one step.

Amplification Gain of Transistor Q2

As described above, when the noise signal input through the microphone 10 is input to a predetermined size, the mite 10 is output in a state in which an audio signal amplified in the first stage is output from an audio output terminal ASO for outputting an electrical signal for driving a speaker. When the noise input through the signal is increased to a predetermined value or more, the amplified signal amplified by the collector of the transistor Q1 also increases, and thus, the DC voltages across the capacitor C3 also increase.

When the DC voltage at both ends of the shunt capacitor C3 is larger than the set voltage V2 as described above, the first-second output logic signals of the comparators OP1 to OP2 all output a "high" state. The so-called analog switch ASW remains in the "on" state, and the transistor Q3 is "turned on" by the bias resistors of the resistors R15-R16.

Therefore, the emitter resistor R13 of the transistor Q2 and the collector resistor R14 of the transistor Q3 are connected in parallel, whereby the emitter resistance of the transistor Q2 is equal to that of the actual resistor R13. By becoming smaller than the value, the amplification gain G2 of the transistor Q2 amplifies the audio signal input from the audio input terminal ASI with a gain larger than that of the fourth amplification as described in the fifth equation below.

Amplification Gain of Transistor Q2

Therefore, when the size of the noise signal input to the microphone 10 is increased, the size of the signal input to the speaker drive 6 through the analog switch ASW is input to the output terminal ASO by inputting the amplified audio signal in two stages. The audio signal input to the speaker is also increased.

As described above, the present invention has an advantage of allowing a user to always hear a constant sound by automatically adjusting and listening to the volume input by a user's setting according to the amount of external noise.

Claims (1)

In the audio output control circuit by the external noise, the microphone 10 for converting the external noise into an electrical signal call, the first amplifier circuit 20 for input-amplifying only the school signal of the electrical signal output from the microphone 10 at all times; An integrating circuit 30 for half-wave rectifying and integrating the amplified output signal of the first amplifying circuit 20 to direct-level the noise signal and outputting the noise signal by comparing the DC-leveled signal with a predetermined reference level. A noise level determination circuit 40 for outputting a 1-2 logic signal for determining the level of the signal, a second amplifier circuit 50 for amplifying and outputting a signal output from an audio device, and a first logic output at all times Switching of the switching drive 60 and the output second logic signal to selectively drive the output audio of the audio device and the audio signal, Is switched by the bell circuit condition, it characterized in that the switch consists of a control circuit 70 for controlling an amplification gain of the second amplifier circuit (50).