CN212875753U - AGC control circuit and voice acquisition device based on audio output - Google Patents
AGC control circuit and voice acquisition device based on audio output Download PDFInfo
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- CN212875753U CN212875753U CN202021070773.4U CN202021070773U CN212875753U CN 212875753 U CN212875753 U CN 212875753U CN 202021070773 U CN202021070773 U CN 202021070773U CN 212875753 U CN212875753 U CN 212875753U
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Abstract
The embodiment of the utility model discloses AGC control circuit and pronunciation collection system based on audio output, AGC control circuit includes: the device comprises a band-pass filter, an audio amplification circuit, an envelope detection circuit, an inverting amplifier circuit, an audio signal primary amplification circuit, an audio signal secondary amplification circuit and the like. The embodiment of the utility model provides a can abandon complicated VAD algorithm and high-cost DSP application, can realize the AGC of audio output with very cheap hardware circuit.
Description
Technical Field
The utility model relates to the field of electronic technology, especially, relate to a AGC control circuit and pronunciation collection system based on audio output.
Background
Automatic Gain Control (AGC) is an Automatic Control method for automatically adjusting the Gain of an amplifier circuit according to the signal intensity. Automatic gain control is one type of limited output that adjusts the output signal of a speech signal using an efficient combination of linear amplification and compressed amplification. When a weak signal is input, the linear amplification circuit works to ensure the strength of the output signal; when the input signal reaches a certain intensity, the compression amplifying circuit is started to reduce the output amplitude. That is, the AGC function can automatically control the magnitude of the gain by changing the input-output compression ratio. AGC is subdivided into input and output automatic gain control AGCi and AGCo.
In the prior art, digital processing is basically adopted, namely, the digital gain of voice amplitude is adjusted through a DSP (digital signal processor), so that the aim of AGC (automatic gain control) is fulfilled, and the dynamic range of a sound pick-up is ensured. The prior art is effective in realizing the function, but to realize the function, the following functions are ensured: the DSP speed can be matched to the corresponding AGC gain requirements and a more complex voice VAD detection algorithm is employed. And the adoption of DSP to realize AGC gain results in high overall cost, for example, the design of elevator intercom terminal with high cost performance is greatly limited.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to overcome prior art not enough, the utility model provides a AGC control circuit and voice acquisition device based on audio output, it can abandon complicated VAD algorithm and costly DSP and use, can realize the AGC of audio output with very cheap hardware circuit.
In order to solve the above problem, the utility model provides a AGC control circuit based on audio output, AGC control circuit includes: band-pass filter, audio frequency amplifier circuit, envelope detection circuit, inverting amplifier circuit, audio signal one-level amplifier circuit and audio signal second grade amplifier circuit, wherein:
the band-pass filter is used for filtering low-frequency and high-frequency interference signals in the audio signals;
the audio amplifying circuit is connected with the output end of the band-pass filter and is used for amplifying the voltage amplitude of the output signal of the band-pass filter;
the envelope detection circuit is connected with the output end of the audio amplification circuit and used for extracting the amplitude characteristic of the audio signal and outputting the envelope characteristic of the audio signal amplitude;
the inverting amplifier circuit is connected with the output end of the envelope detection circuit and is used for enabling the output result to be in inverse proportion to the amplitude of the audio signal output by the envelope detection circuit and outputting the output result to the audio signal primary amplification circuit;
the audio signal primary amplifying circuit is connected with the output end of the band-pass filter and the output end of the inverting amplifier circuit, and is used for carrying out AGC control on the basis of the output result of the inverting amplifier circuit and the output signal of the band-pass filter and outputting the AGC result to the audio signal secondary amplifying circuit;
and the audio signal secondary amplifying circuit outputs audio based on the AGC result.
The band-pass filter comprises a low-pass filter, a high-pass filter and an operational amplifier, wherein: the low-pass filter is connected with the high-pass filter, and the high-pass filter is connected with the operational amplifier.
The low-pass filter is a first-order passive low-pass filter, and the high-pass filter is a first-order passive high-pass filter.
The audio amplification circuit comprises a first triode, and the audio amplification circuit performs voltage amplitude amplification based on the first triode.
The envelope detection circuit is a parallel diode envelope detection circuit, or a series diode peak value detector.
The series diode peak value comprises a detector comprising a diode and a low-pass filter, wherein the diode is connected with the low-pass filter.
The audio signal primary amplifying circuit comprises a second triode, and the audio signal primary amplifying circuit performs AGC control based on the second triode.
The second triode is an NPN triode, the NPN triode adopts a common-emitter cascade connection method, and the base electrode of the NPN triode is connected with the output end of the band-pass filter and the output end of the inverting amplifier circuit; or the second triode is a PNP triode or an MOS tube.
The audio signal secondary amplification circuit is an inverting amplifier.
Correspondingly, the utility model also provides a pronunciation collection system, the elevator intercom system adopts above AGC control circuit based on audio output.
The embodiment of the utility model provides an in AGC control circuit, whole analog circuit schemes that adopt, its triode and operational amplifier circuit etc. through utilizing low-priced, technological maturity realize AGC's purpose, and the input gain of adapter can realize automatically regulated according to the speech intensity based on AGC control circuit, ensures audio signal high-fidelity to have high dynamic range, the circuit still can realize band-pass filtering, its comprehensive cost is lower, the functional.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic diagram of an AGC control circuit structure based on audio output according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of an AGC control circuit based on audio output according to an embodiment of the present invention;
fig. 3 is a schematic diagram of the output characteristics of the triode in the embodiment of the present invention;
fig. 4 is a schematic diagram of the input characteristic of the triode in the embodiment of the present invention;
fig. 5 is a schematic diagram of the gain relationship of the input vs triode in the embodiment of the present invention;
fig. 6 is a schematic diagram of the output relationship of input vs in the embodiment of the present invention;
fig. 7 is a schematic diagram of the filter characteristic in the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
Fig. 1 shows a schematic diagram of an AGC control circuit structure based on audio output in an embodiment of the present invention, the AGC control circuit includes: band-pass filter, audio frequency amplifier circuit, envelope detection circuit, inverting amplifier circuit, audio signal one-level amplifier circuit and audio signal second grade amplifier circuit, wherein:
the signal output end of the band-pass filter is connected with the audio amplification circuit and the audio signal primary amplification circuit;
the signal input end of the audio amplification circuit is connected with the band-pass filter, and the signal output end of the audio amplification circuit is connected with the envelope detection circuit;
the signal input end of the envelope detection circuit is connected with the audio amplification circuit, and the signal output end of the envelope detection circuit is connected with the inverting amplifier circuit;
the signal input end of the inverting amplifier circuit is connected with the audio amplification circuit, and the signal output end of the inverting amplifier circuit is connected with the audio signal primary amplification circuit;
the signal input end of the audio signal primary amplifying circuit is connected with the band-pass filter and the inverting amplifier circuit, and the signal output end of the audio signal primary amplifying circuit is connected with the audio signal secondary amplifying circuit.
The band-pass filter is used for filtering low-frequency and high-frequency interference signals in the audio signals;
the audio amplifying circuit is connected with the output end of the band-pass filter and is used for amplifying the voltage amplitude of the output signal of the band-pass filter;
the envelope detection circuit is connected with the output end of the audio amplification circuit and used for extracting the amplitude characteristic of the audio signal and outputting the envelope characteristic of the audio signal amplitude;
the inverting amplifier circuit is connected with the output end of the envelope detection circuit and is used for enabling the output result to be in inverse proportion to the amplitude of the audio signal output by the envelope detection circuit and outputting the output result to the audio signal primary amplification circuit;
the audio signal primary amplifying circuit is connected with the output end of the band-pass filter and the output end of the inverting amplifier circuit, and is used for carrying out AGC control on the basis of the output result of the inverting amplifier circuit and the output signal of the band-pass filter and outputting the AGC result to the audio signal secondary amplifying circuit;
and the audio signal secondary amplifying circuit outputs audio based on the AGC result.
When the AGC control circuit based on audio output shown in figure 1 is applied to a voice acquisition device or an elevator intercom system, audio signals picked up by a sound pickup in the voice acquisition device or the elevator intercom system can pass through a band-pass filter, the band-pass filter has the functions and effects of filtering low-frequency and high-frequency interference signals and then dividing the output signals into two paths for output. One path of output signal of the band-pass filter is subjected to analog processing of an audio amplification circuit, an envelope detection circuit, an inverting amplifier circuit and the like, and then provides bias voltage for an audio signal primary amplification circuit; the other path of audio signal of the band-pass filter is only used as the input of the audio signal primary amplifying circuit, the bias voltage of the audio signal primary amplifying circuit is controlled by the signal output by the inverting amplifier circuit, if the amplitude of the audio signal is increased, the bias voltage is reduced, the gain of the audio signal primary amplifying circuit is reduced, AGC control is realized by the method, and finally the audio signal is output through the audio signal secondary amplifying circuit.
Specifically, fig. 2 shows a schematic circuit diagram of an AGC control circuit based on audio output in an embodiment of the present invention, the AGC control circuit includes: a band-pass filter, an audio amplifying circuit, an envelope detecting circuit, an inverting amplifier circuit, an audio signal primary amplifying circuit, an audio signal secondary amplifying circuit, and the like.
The band-pass filter comprises a low-pass filter, a high-pass filter and an operational amplifier, wherein: the low-pass filter is connected with the high-pass filter, and the high-pass filter is connected with the operational amplifier. The low-pass filter is a first-order passive low-pass filter, and the high-pass filter is a first-order passive high-pass filter.
The embodiment of the utility model provides an in band pass filter is put by a first-order passive low pass filter, a first-order passive high pass filter, an fortune and is constituteed, its frequency response can write into:
where ω is the input angular frequency, ω0Is the center frequency of the band-pass filter, A0For the gain of the band pass filter, A (j ω) is the frequency response function of the band pass filter, j represents the imaginary component, and Q is the quality factor.
The audio amplification circuit amplifies the voltage amplitude of the output signal of the band-pass filter, and the amplified signal is used as the input of the envelope detection circuit. The audio amplification circuit comprises a first triode, and the audio amplification circuit performs voltage amplitude amplification based on the first triode.
The envelope detection circuit may be a parallel diode envelope detection circuit or may also include a detector for the series diode peak.
The embodiment of the utility model provides an envelope detection circuit adopts the tandem type diode peak value to include the wave detector, and the tandem type diode peak value includes that the wave detector includes diode and low pass filter, the diode is connected low pass filter. The envelope detection is also called amplitude detection, and mainly extracts the amplitude characteristic of an audio signal (voice signal) and outputs the envelope characteristic of the amplitude of the audio signal (voice signal). The envelope detection circuit is formed by connecting a diode and a low-pass filter in series, when an input signal is provided to the envelope detection circuit, the current passing through the diode generates an average voltage in the low-pass filter circuit, and the average voltage is reacted on the diode (called average voltage negative feedback effect) to influence the current passing through the diode, thereby realizing linear detection.
The inverting amplifier circuit is connected with the output end of the envelope detection circuit and used for enabling the output result to be in inverse proportion to the amplitude of the audio signal output by the envelope detection circuit and outputting the output result to the audio signal primary amplification circuit. The output voltage of the inverting amplifier circuit is in inverse proportional relation with the output of the envelope detection circuit, and then a bias is provided for the base of the audio signal primary amplifier, and the bias voltage can be written as;
wherein Vcc is the supply voltage for the reverse operational amplifier, K0For constant coefficients, Vin is the input to the microphone, and A (j ω) is the frequency response function of the band pass filter.
The audio signal primary amplifying circuit is connected with the output end of the band-pass filter and the output end of the inverting amplifier circuit, and is used for carrying out AGC control based on the output result of the inverting amplifier circuit and the output signal of the band-pass filter and outputting the AGC result to the audio signal secondary amplifying circuit. The audio signal primary amplifying circuit comprises a second triode, and the audio signal primary amplifying circuit performs AGC control based on the second triode.
The second triode is an NPN triode, the NPN triode adopts a common-emitter cascade connection method, and the base electrode of the NPN triode is connected with the output end of the band-pass filter and the output end of the inverting amplifier circuit; or the second triode is a PNP triode or an MOS tube. The audio signal secondary amplification circuit is an inverting amplifier.
Correspondingly, the utility model also provides a pronunciation collection system, pronunciation collection system adopts above AGC control circuit based on audio output.
Here, the audio signal primary amplification circuit is exemplified by an NPN transistor, which employs a common emitter connection method. As shown in fig. 3, the output characteristic of the transistor has three operating states, namely, a cut-off region, an amplification region and a saturation region. In the amplification region, the base current Ib and the collector current Ic are linear, and Vbe is 0.7V (for example, a silicon transistor).
The transistor has a critical state in the cut-off region and the amplification region, wherein Vbe is the critical state<0.7V, and meanwhile Vbe is larger than the threshold voltage of BE pole, this area is the conduction area of BE pole of triode, fig. 4 shows the schematic diagram of input characteristic of triode, at this moment, base current Ib is very small, CE pole presents larger impedance, therefore collector current Ic is very weak, and triode along with Vbe increase, Ib also increases, triode current gain increases
And the gain of the triode is a constant value beta, the beta value is determined by the characteristics of each triode, and the triode is a constant value under certain conditions after leaving the factory.
Since the transistor has the critical state of the cut-off region-amplification region, the amplification factor K1 of the transistor in the critical state can be controlled by the base voltage. The embodiment of the utility model provides an in, the Vbias of inverting amplifier circuit output provides voltage bias for the base of common emitter stage amplifier circuit (audio signal one-level amplifier circuit), and along with Vin's increase, Vbias can reduce, consequently K1 also can reduce, and fig. 5 shows input vs triode gain relation schematic diagram, for adopting 2N 5551's measured data. It can be seen from fig. 5 that, along with the increase of input signal amplitude, the triode gain slowly reduces, the negative gain finally appears, and the triode is in the decay state this moment, consequently the utility model provides a AGC function can be realized to the first order audio frequency amplified triode. And then gain of the whole circuit is provided through two-stage audio amplification, so that the output amplitude is in a specific interval.
In order to verify the whole effect, 1kHz audio signal is input from the input end of the whole AGC circuit, the amplitude ranges from 0.5V to 14V, then the Vout amplitude is tested, as shown in a schematic diagram of an input vs output relationship shown in FIG. 6, the input audio signal amplitude increases by 28 times, but the output changes by only 2 times, the output just starts to rise, then slowly falls, finally the output amplitude tends to be flat, and the maximum output and the minimum output show that the input output is not in a linear relationship. Along with the increase of the input amplitude, the input cannot be increased all the time, so that the problem of cut-off distortion caused by close-distance sound pickup of a sound pickup is solved, and the aim of high dynamic range of voice amplitude is fulfilled.
In order to find the output-to-frequency response relationship, by defining the input audio signal amplitude as 2V and changing its frequency, the frequency response can be tested, as shown in the filter characteristic diagram of fig. 7, and it can be seen that the AGC circuit has a band-pass filtering function.
Based on the embodiment of the utility model provides an in AGC control circuit, whole analog circuit schemes that adopt, it is through utilizing low-priced, the mature triode of technique and operational amplifier circuit etc. realize AGC's purpose, and the input gain of adapter can realize automatically regulated according to the speech intensity based on AGC control circuit, ensures audio signal high-fidelity to have high dynamic range, the circuit still can realize band-pass filtering, its comprehensive cost is lower, the functional.
The AGC control circuit based on audio output and the elevator intercom system provided by the embodiment of the present invention are introduced in detail, and a specific example is applied to explain the principle and the implementation of the present invention, and the description of the above embodiment is only used to help understand the method and the core idea of the present invention; meanwhile, for the general technical personnel in the field, according to the idea of the present invention, there are changes in the specific implementation and application scope, to sum up, the content of the present specification should not be understood as the limitation of the present invention.
Claims (10)
1. An AGC control circuit based on an audio output, the AGC control circuit comprising: band-pass filter, audio frequency amplifier circuit, envelope detection circuit, inverting amplifier circuit, audio signal one-level amplifier circuit and audio signal second grade amplifier circuit, wherein:
the band-pass filter is used for filtering low-frequency and high-frequency interference signals in the audio signals;
the audio amplifying circuit is connected with the output end of the band-pass filter and is used for amplifying the voltage amplitude of the output signal of the band-pass filter;
the envelope detection circuit is connected with the output end of the audio amplification circuit and used for extracting the amplitude characteristic of the audio signal and outputting the envelope characteristic of the audio signal amplitude;
the inverting amplifier circuit is connected with the output end of the envelope detection circuit and is used for enabling the output result to be in inverse proportion to the amplitude of the audio signal output by the envelope detection circuit and outputting the output result to the audio signal primary amplification circuit;
the audio signal primary amplifying circuit is connected with the output end of the band-pass filter and the output end of the inverting amplifier circuit, and is used for carrying out AGC control on the basis of the output result of the inverting amplifier circuit and the output signal of the band-pass filter and outputting the AGC result to the audio signal secondary amplifying circuit;
and the audio signal secondary amplifying circuit outputs audio based on the AGC result.
2. The audio output based AGC control circuit of claim 1, wherein the band pass filter comprises a low pass filter, a high pass filter, an op amp, and wherein: the low-pass filter is connected with the high-pass filter, and the high-pass filter is connected with the operational amplifier.
3. The audio output based AGC control circuit of claim 2 wherein the low pass filter is a first order passive low pass filter and the high pass filter is a first order passive high pass filter.
4. The audio output based AGC control circuit of claim 1 wherein the audio amplification circuit includes a first transistor, the audio amplification circuit performing voltage amplitude amplification based on the first transistor.
5. The audio output based AGC control circuit of claim 1 wherein the envelope detection circuit is a parallel diode envelope detection circuit or a series diode peak detector.
6. The audio output based AGC control circuit of claim 5 wherein said series diode peak detector comprises a diode and a low pass filter, said diode coupled to said low pass filter.
7. The audio output based AGC control circuit of claim 1 wherein the audio signal stage amplification circuit includes a second transistor, the audio signal stage amplification circuit performing AGC control based on the second transistor.
8. The audio output based AGC control circuit of claim 7 wherein the second transistor is an NPN transistor, the NPN transistor being in cascode connection, a base of the NPN transistor being connected to the output of the band pass filter and the output of the inverting amplifier circuit; or the second triode is a PNP triode or an MOS tube.
9. The audio output based AGC control circuit of any one of claims 1 through 8 wherein the audio signal secondary amplification circuit is an inverting amplifier.
10. A voice acquisition apparatus, characterized in that the voice acquisition apparatus employs the AGC control circuit based on audio output according to any one of claims 1 to 9.
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| CN202021070773.4U CN212875753U (en) | 2020-06-11 | 2020-06-11 | AGC control circuit and voice acquisition device based on audio output |
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| CN202021070773.4U CN212875753U (en) | 2020-06-11 | 2020-06-11 | AGC control circuit and voice acquisition device based on audio output |
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