Audio circuitry

Abstract

The application provides an audio circuit, which comprises a comparison module and a switch module; an input end of the comparison module is connected to an audio signal, the comparison module is used for obtaining the audio signal and identifying whether the audio signal comprises valid sound; in the case that the audio signal comprises valid sound, the comparison module is used for controlling the switch module to be turned on; when the switch module is turned on, the switch module is used for outputting the audio signal; in the case that the audio signal does not comprise valid sound, the comparison module is used for controlling the switch module to be turned off; when the switch module is turned off, the switch module is used for stopping outputting the audio signal. The application normally outputs the audio signal when the audio signal comprises valid sound, and stops outputting the audio signal when the audio signal does not comprise valid sound and only comprises noise, so that idle-time noise reduction is realized and the background noise in the environment without human voice is reduced.

Description

Technical Field

[0001] This application belongs to the field of audio technology, and in particular relates to an audio circuit. Background Technology

[0002] With the continuous development of technology, cameras are increasingly being used in people's daily lives. For example, cameras are used for security monitoring.

[0003] However, cameras used for security monitoring generally suffer from high background noise. Using software algorithms to eliminate this noise is costly and may not completely eliminate it. Hardware modifications to eliminate the noise are also costly and may not completely eliminate it. Summary of the Invention

[0004] The purpose of this application is to provide an audio circuit that aims to solve the problem of background noise in traditional audio circuits that cannot be completely eliminated.

[0005] To achieve the above objectives, in a first aspect, embodiments of this application provide an audio circuit, including a comparison module and a switching module. The input terminal of the comparison module is connected to an audio signal. The comparison module is used to acquire the audio signal and to identify whether the audio signal contains valid sound. If the audio signal contains valid sound, the comparison module controls the switching module to turn on, and when the switching module is on, the switching module outputs the audio signal. If the audio signal does not contain valid sound, the comparison module controls the switching module to turn off, and when the switching module is off, the switching module stops outputting the audio signal.

[0006] It should be understood that valid sound includes human voice.

[0007] In another possible implementation of the first aspect, the comparison module is used to compare the amplitude of the audio signal with a preset value; when the amplitude of the audio signal is greater than the preset value, it is determined that the audio signal contains valid sound; when the amplitude of the audio signal is less than or equal to the preset value, it is determined that the audio signal is noise that does not contain valid sound.

[0008] In another possible implementation of the first aspect, the audio circuit further includes an amplification module, the input of which is connected to the audio signal, and the output of which is connected to the input of the comparison module. The amplification module is used to amplify the audio signal.

[0009] In another possible implementation of the first aspect, the amplification module includes a third operational amplifier, a second capacitor, a third voltage divider circuit, and a gain adjustment circuit. The non-inverting input of the third operational amplifier is connected to the voltage divider terminal of the third voltage divider circuit, the power supply terminal of the third voltage divider circuit is connected to a power supply, and the ground terminal of the third voltage divider circuit is grounded. The inverting input of the third operational amplifier is connected to the adjustment terminal of the gain adjustment circuit, the input terminal of the gain adjustment circuit is connected to an audio signal through the second capacitor, and the output terminal of the gain adjustment circuit is connected to the output terminal of the third operational amplifier.

[0010] In another possible implementation of the first aspect, the amplification adjustment circuit includes a tenth resistor, an eleventh resistor, and a twelfth resistor. One end of the tenth resistor and one end of the eleventh resistor are both connected to the inverting input of the third operational amplifier. The other end of the tenth resistor is connected to the audio signal through a second capacitor, and the other end of the eleventh resistor is connected to the output of the third operational amplifier through the twelfth resistor.

[0011] In another possible implementation of the first aspect, the audio circuit further includes a volume control module, the input of which is connected to an audio signal, and the output of which is connected to the input of a switch module. The volume control module is used to adjust the volume of the audio signal.

[0012] In another possible implementation of the first aspect, the comparison module includes a first operational amplifier, a first protection device, and a first voltage divider circuit. The non-inverting input of the first operational amplifier is connected to an audio signal through the first protection device, the inverting input of the first operational amplifier is connected to the voltage divider terminal of the first voltage divider circuit, the power supply terminal of the first voltage divider circuit is connected to a power supply, the ground terminal of the first voltage divider circuit is grounded, and the output terminal of the operational amplifier is connected to the input terminal of the switching module.

[0013] In another possible implementation of the first aspect, the comparison module further includes a fourth resistor and a first LC filter circuit. One end of the fourth resistor is connected to the output of the first operational amplifier, and the other end of the fourth resistor is connected to the input of the first LC filter circuit. The output of the first LC filter circuit is connected to the input of the switching module.

[0014] In another possible implementation of the first aspect, the comparison module further includes a second operational amplifier, a second protection device, and a second voltage divider circuit. The non-inverting input of the second operational amplifier is connected to the output of the first operational amplifier through the second protection device, the inverting input of the second operational amplifier is connected to the voltage divider terminal of the second voltage divider circuit, the power supply terminal of the second voltage divider circuit is connected to a power supply, the ground terminal of the second voltage divider circuit is grounded, and the output of the second operational amplifier is connected to the input of the switching module.

[0015] In another possible implementation of the first aspect, the switching module includes an analog switch. A first pin of the analog switch is connected to an audio signal, a second pin is grounded, a third pin is left floating, a fourth pin outputs an audio signal, a fifth pin is connected to a power supply, and a sixth pin is grounded. The sixth pin of the analog switch is used to receive a control signal output by the comparator module. The control signal is used to control the fourth pin and the first pin of the analog switch to conduct, or to control the fourth pin and the third pin of the analog switch to conduct.

[0016] Secondly, embodiments of this application provide a camera that includes the audio circuitry described above.

[0017] In this embodiment, the comparison module is used to acquire an audio signal and to identify whether the audio signal contains valid sound. When the audio signal contains valid sound, the comparison module controls the switch module to turn on, and when the switch module is on, it outputs the audio signal. When the audio signal does not contain valid sound, the comparison module controls the switch module to turn off, and when the switch module is off, it stops outputting the audio signal. This ensures normal audio signal output when valid sound is present, and stops outputting the audio signal when only noise is present, thereby achieving noise reduction during idle time and reducing background noise in environments without human voices.

[0018] Thirdly, embodiments of this application provide an audio circuit, including: an audio input terminal, a first operational amplifier, an LC filter circuit, a second operational amplifier, a switching module, and an audio output terminal. The audio waveform signal acquired by a camera is input to the first operational amplifier via the audio input terminal to generate a pulse level signal. The pulse level signal is filtered by the LC filter circuit and then input to the second operational amplifier to generate a DC level control signal. The DC level control signal includes a high-level signal and a low-level signal. When the DC level control signal is high, the audio waveform signal is transmitted to the audio output terminal via the switching module and output. When the DC level control signal is low, the switching module is open, and the audio waveform signal is blocked. The first operational amplifier is configured such that: the non-inverting input terminal of the first operational amplifier is used to receive the audio waveform signal, and the inverting input terminal of the first operational amplifier is used to obtain a first threshold voltage; when the audio waveform signal is greater than the first threshold voltage, the first operational amplifier outputs a pulse level signal. The second operational amplifier is configured such that its non-inverting input is used to receive the output signal of the LC filter circuit, and its inverting input is used to obtain a second threshold voltage. When the output signal of the LC filter circuit is greater than the second threshold voltage, the second operational amplifier outputs a high-level signal; when the output signal of the LC filter circuit is less than or equal to the second threshold voltage, the second operational amplifier outputs a low-level signal. The first threshold voltage is used to indicate whether the audio waveform signal contains human voice signals. The second threshold voltage is used to control the switching module's on and off states.

[0019] In another possible implementation of the third aspect, the audio circuit further includes an amplification module, wherein the audio waveform signal is input to the amplification module via an audio input terminal for amplification, and the amplified audio signal is input to the non-inverting input terminal of a first operational amplifier, which is used to compare the amplified audio signal with a first threshold voltage.

[0020] In another possible implementation of the third aspect, the switching module includes an analog switch. A first pin of the analog switch is used to receive an audio waveform signal. A sixth pin of the analog switch is connected to the output of a second operational amplifier and is used to receive a DC level control signal. A fourth pin of the analog switch is connected to an audio output terminal and is used to output an audio waveform signal. A third pin of the analog switch is left floating. When the sixth pin of the analog switch receives a high-level signal, the first and fourth pins of the analog switch are connected, and the audio waveform signal is transmitted to the audio output terminal via the first and fourth pins. When the sixth pin of the analog switch receives a low-level signal, the third and fourth pins of the analog switch are connected, and there is no audio output.

[0021] In another possible implementation of the third aspect, the first threshold voltage is generated by dividing the power supply voltage by a first voltage divider circuit. The first voltage divider circuit includes a second resistor and a third resistor connected in series. One end of the second resistor is connected to the power supply voltage, and one end of the third resistor is grounded. The first threshold voltage is the voltage at the common connection point of the second and third resistors. When the amplitude of the audio waveform signal is greater than the first threshold voltage, the pulse level signal output by the first operational amplifier is a high-level signal, indicating that the audio waveform signal contains a human voice signal.

[0022] In another possible implementation of the third aspect, the second threshold voltage is generated by dividing the power supply voltage by a second voltage divider circuit, which includes a sixth resistor and a seventh resistor connected in series. One end of the sixth resistor is connected to the power supply voltage, and one end of the seventh resistor is grounded. The second threshold voltage is the voltage at the common connection point of the sixth and seventh resistors.

[0023] In another possible implementation of the third aspect, the LC filter circuit includes a first inductor and a first capacitor; wherein the output terminal of the first operational amplifier is connected to one end of the first capacitor through the first inductor, the other end of the first capacitor is grounded, and the common connection terminal of the first inductor and the first capacitor is connected to the input terminal of the switching module.

[0024] In another possible implementation of the third aspect, the amplification module includes a third operational amplifier, a tenth resistor, an eleventh resistor, and a twelfth resistor. The inverting input of the third operational amplifier is connected in series with the tenth resistor and then to the audio waveform signal. The inverting input of the third operational amplifier is also connected in series with the eleventh and twelfth resistors and then to the output of the third operational amplifier. The non-inverting input of the third operational amplifier is used to obtain the bias voltage. The voltage at the inverting input of the third operational amplifier is equal to the bias voltage. The amplitude of the audio waveform signal is multiplied by (eleventh resistor + twelfth resistor) / tenth resistor, and then the bias voltage is added to obtain the amplified audio signal at the output of the third operational amplifier.

[0025] In another possible implementation of the third aspect, the bias voltage is generated by dividing the power supply voltage by a third voltage divider circuit, which includes an eighth resistor and a ninth resistor connected in series. One end of the ninth resistor is connected to the power supply voltage, and one end of the eighth resistor is grounded. The bias voltage is the voltage at the common connection point of the eighth and ninth resistors.

[0026] In another possible implementation of the third aspect, the audio circuit further includes a volume adjustment module, the input of which is connected to an audio signal, and the output of which is connected to the input of a switch module; the volume adjustment module is used to adjust the volume of the audio signal.

[0027] Fourthly, embodiments of this application provide a camera, including the camera audio circuit of any of the above-mentioned components.

[0028] In this embodiment, the audio waveform signal captured by the camera is input to the first operational amplifier via the audio input terminal to generate a pulse level signal. The pulse level signal is then filtered by an LC filter circuit and input to the second operational amplifier to generate a DC level control signal. The DC level control signal includes a high-level signal and a low-level signal. When the DC level control signal is high, the audio waveform signal is transmitted to the audio output terminal via a switching module and output. When the DC level control signal is low, the switching module is open, and the audio waveform signal is blocked. This ensures that the audio signal is output normally when it contains valid sound, and stops outputting the audio signal when it contains only noise and no valid sound, thereby achieving noise reduction during idle time and reducing background noise when there is no human voice in the environment. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of an audio circuit provided in an embodiment of this application;

[0031] Figure 2 This is a schematic diagram of the structure of an audio circuit provided in another embodiment of this application;

[0032] Figure 3 This is a schematic diagram of the structure of an audio circuit provided in another embodiment of this application;

[0033] Figure 4 A circuit diagram of a comparison module provided in an embodiment of this application;

[0034] Figure 5 This is a circuit diagram of an amplification module provided in an embodiment of this application;

[0035] Figure 6 This is a circuit diagram of a switching module provided in an embodiment of this application. Detailed Implementation

[0036] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0038] Currently, traditional audio circuits typically use software algorithms or hardware modifications to reduce or eliminate background noise. However, using software algorithms is costly and may not completely eliminate the noise. Similarly, hardware modifications are also costly and may not completely eliminate the noise.

[0039] To address this issue, this application provides an audio circuit based on the principle that people primarily hear valid human voices when electronic devices emit human voices and are not sensitive to background noise, but become highly sensitive to background noise in quiet environments without human voices. A comparison module compares the amplitude of the audio signal with a preset value. When the amplitude of the audio signal is greater than the preset value, it is determined that the audio signal contains valid sound; otherwise, it is determined that the audio signal is noise. A switching module turns on to output the audio signal when the audio signal contains valid sound and turns off to stop outputting the audio signal when the audio signal is noise, thereby achieving noise reduction during idle periods and reducing background noise in environments without human voices.

[0040] The audio circuit provided in this application will be described exemplarily below with reference to the accompanying drawings.

[0041] Figure 1 This is a schematic diagram of the structure of an audio circuit provided in an embodiment of this application. Figure 1 As shown, by way of example, this application provides an audio circuit 10. The audio circuit 10 includes a comparison module 101 and a switching module 102. An audio signal is received at the input terminal of the comparison module 101. The comparison module 101 is used to acquire the audio signal and to identify whether the audio signal contains a valid sound. The comparison module 101 is also used to control the switching module 102 to be turned on or off based on the comparison result of whether the audio signal contains a valid sound. When the switching module 102 is turned on, the switching module 102 is used to output an audio signal. When the switching module 102 is turned off, the switching module 102 is used to stop outputting the audio signal.

[0042] For example, the audio circuit 10 includes an audio input terminal, a comparison module 101, a switching module 102, and an audio output terminal. The comparison module 101 includes a first operational amplifier, an LC filter circuit, and a second operational amplifier. Specifically, the audio waveform signal acquired by the camera is input to the first operational amplifier via the audio input terminal to generate a pulse level signal. The pulse level signal is filtered by the LC filter circuit and then input to the second operational amplifier to generate a DC level control signal. The DC level control signal includes a high-level signal and a low-level signal. When the DC level control signal is high, the audio waveform signal is transmitted to the audio output terminal via the switching module and output. When the DC level control signal is low, the switching module is open, and the audio waveform signal is blocked.

[0043] Specifically, the first operational amplifier is configured such that its non-inverting input is used to receive an audio waveform signal, and its inverting input is used to acquire a first threshold voltage. When the audio waveform signal exceeds the first threshold voltage, the first operational amplifier outputs a pulse level signal. The first threshold voltage indicates whether the audio waveform signal contains human voice signals.

[0044] Specifically, the second operational amplifier U2 is configured such that its non-inverting input is used to receive the output signal of the LC filter circuit, and its inverting input is used to obtain the second threshold voltage. When the output signal of the LC filter circuit is greater than the second threshold voltage, the second operational amplifier outputs a high-level signal; when the output signal of the LC filter circuit is less than or equal to the second threshold voltage, the second operational amplifier outputs a low-level signal; wherein, the second threshold voltage is used to control the switching module's on and off states.

[0045] It should be understood that when the audio waveform signal captured by the camera contains human voice signals, the first operational amplifier compares the amplitude of the audio waveform signal with a first threshold voltage. If the amplitude of the audio waveform signal is greater than the first threshold voltage, the first operational amplifier outputs a high-level pulse signal. Then, the LC filter circuit filters the high-level pulse signal to obtain a stable DC-level signal. Next, the second operational amplifier compares the DC-level signal with a second threshold voltage. If the DC-level signal is greater than the second threshold voltage, the second operational amplifier outputs a high-level signal. Then, the switching module 102 turns on according to the high-level signal and outputs the audio signal. This ensures normal audio signal output when the audio signal contains valid sound, and stops outputting the audio signal when the audio signal does not contain valid sound and only noise, achieving noise reduction during idle time and reducing background noise when there is no human voice in the environment.

[0046] For example, when the audio signal includes valid sound, the comparison module 101 controls the switch module 102 to turn on, and when the switch module 102 is on, it outputs the audio signal. When the audio signal does not include valid sound, the comparison module 101 controls the switch module 102 to turn off, and when the switch module 102 is off, it stops outputting the audio signal.

[0047] For example, the input terminal of the switch module 102 is connected to the output terminal of the comparison module 101. The comparison module 101 is used to output a first level signal (e.g., a high level signal) to the switch module 102 when it is determined that the audio signal contains valid sound. The first level signal is used to control the switch module 102 to turn on. Therefore, the switch module 102 can be used to turn on when the audio signal contains valid sound to output the audio signal. The comparison module 101 is used to output a second level signal (e.g., a low level signal) to the switch module 102 when it is determined that the audio signal does not contain valid sound. The second level signal is used to control the switch module 102 to turn off. When the audio signal is noise that does not contain valid sound, the switch module 102 turns off to stop outputting the audio signal.

[0048] In one possible embodiment of this application, the comparison module 101 is used to determine whether the audio signal includes valid sound based on the attribute parameters of the audio signal. For example, the attribute parameters of the audio signal may include one or more of the following: frequency, amplitude, and regularity of the audio signal. Generally, the main difference between noise and valid sound is that valid sound has a certain regularity in time, while noise usually does not have a regularity in time. Therefore, the regularity of the audio signal can be used to distinguish whether the audio signal includes valid sound.

[0049] Understandably, the comparison module 101 is used to compare the value of the attribute parameter of the audio signal with the preset attribute parameter value. When the value of the attribute parameter of the audio signal is greater than the preset attribute parameter value, it is determined that the audio signal contains valid sound; when the value of the attribute parameter of the audio signal is less than or equal to the preset attribute parameter value, it is determined that the audio signal is noise.

[0050] The following explanation will use the amplitude value as an example of the attribute parameter of an audio signal.

[0051] In one possible embodiment of this application, the comparison module 101 is used to compare the amplitude of the audio signal with a preset value. When the amplitude of the audio signal is greater than the preset value, it is determined that the audio signal contains valid sound; when the amplitude of the audio signal is less than or equal to the preset value, it is determined that the audio signal is noise.

[0052] It is worth noting that the comparison module 101 can also determine whether the audio signal contains valid sound by comprehensively considering the values ​​of multiple attribute parameters.

[0053] For example, if the values ​​of two or more attribute parameters are greater than the preset attribute parameter values, then valid sound is included; otherwise, valid sound is excluded.

[0054] In this embodiment, when an audio signal is received, the comparison module 101 first compares the amplitude of the audio signal with a preset value. When the amplitude of the audio signal is greater than the preset value, it is determined that the audio signal contains valid sound and can be output normally. It should be understood that valid sound includes human voice. When the amplitude of the audio signal is less than or equal to the preset value, it is determined that the audio signal is noise and can be eliminated. Then, the switching module 102 is turned on when the audio signal contains valid sound to output the audio signal; when the audio signal is noise, it is turned off to stop outputting the audio signal. Thus, the audio signal is output normally when the environment contains valid sound. Since people pay more attention to valid sound and are less sensitive to background noise, the audio signal is stopped when the environment is only noise, thereby stopping the output of background noise, thus realizing the idle noise reduction of the audio circuit.

[0055] Figure 2 This is a schematic diagram of the structure of an audio circuit provided in another embodiment of this application. For example... Figure 2 As shown, exemplarily, in one embodiment provided in this application, the audio circuit 10 may further include an amplification module 103. The input terminal of the amplification module 103 is connected to an audio waveform signal, and the output terminal of the amplification module 103 is connected to the input terminal of the comparison module 101. The amplification module 103 is used to amplify the audio signal.

[0056] In this embodiment, to better compare the audio signal with the preset value, the audio signal can be amplified first. That is, the effective sound and background noise in the audio signal are amplified simultaneously, making it easier for the comparison module 101 to compare the amplified audio signal with the preset value and accurately output the comparison result.

[0057] Figure 3 This is a schematic diagram of the structure of an audio circuit provided in another embodiment of this application. For example... Figure 3 As shown, exemplarily, in one embodiment provided in this application, the audio circuit 10 may further include a volume adjustment module 104. The input terminal of the volume adjustment module 104 is connected to an audio signal, and the output terminal of the volume adjustment module 104 is connected to the input terminal of the switch module 102. The volume adjustment module 104 is used to adjust the volume of the audio signal.

[0058] In this embodiment of the application, the volume adjustment module 104 can adjust the volume of the audio signal to compensate for audio loss during long-distance transmission.

[0059] It should be understood that, in one embodiment provided in this application, the audio circuit 10 may further include an audio input module, an audio output module, and a power supply module. The audio output module is used to protect against and handle external audio interference. The audio output module is used for audio output and can isolate the audio signal from other interference signals. For example, in a camera, it ensures isolation between the speaker ground and the camera. The power supply module supplies power to the comparator module 101, the switch module 102, the amplification module 103, the volume control module 104, the audio input module, and the audio output module.

[0060] Figure 4 This is a circuit diagram of a comparison module provided in an embodiment of this application. Figure 4 As shown, exemplarily, in one embodiment provided in this application, the comparison module 101 includes a first operational amplifier U1. The non-inverting input terminal 1 (e.g., positive (+) phase input terminal) of the first operational amplifier U1 is used to input an audio signal. The inverting input terminal 3 (e.g., negative (-) phase input terminal) of the first operational amplifier U1 is used to obtain a preset value. As an example, this preset value can be a pre-set value or a preset voltage division value obtained based on the power supply VCC.

[0061] It is understood that when the attribute parameter is any other than the amplitude, the inverting input terminal 3 of the first operational amplifier U1 (e.g., the negative (-) phase input terminal) is used to obtain the corresponding preset attribute parameter value. This application embodiment does not limit this.

[0062] Optionally, the comparator module 101 may further include a first protection device, which is connected in series between the audio input port of the comparator module 101 and the non-inverting input terminal 1 of the first operational amplifier U1. By setting the first protection device, excessive current can be prevented from impacting the first operational amplifier U1.

[0063] For example, the first protection device can be a current-limiting device. For instance, the first protection device can be a first resistor R1. For instance, the first protection device can also be a negative temperature coefficient thermistor or a positive temperature coefficient thermistor. For instance, the first protection device can also be a current-limiting device such as a fuse.

[0064] For example, such as Figure 4As shown, the inverting input terminal 3 (e.g., the negative (-) phase input terminal) of the first operational amplifier U1 is connected to the first voltage divider circuit. The power supply terminal of the first voltage divider circuit is connected to the power supply VCC and is used to provide a preset voltage divider value to the inverting input terminal 3 (e.g., the negative (-) phase input terminal) of the first operational amplifier U1 based on the power supply VCC.

[0065] For example, such as Figure 4 As shown, the first threshold voltage is generated by dividing the power supply voltage VCC using a first voltage divider circuit. The first voltage divider circuit includes a second resistor R2 and a third resistor R3 connected in series. One end of the second resistor R2 is connected to the power supply voltage VCC, and one end of the third resistor R3 is grounded. The first threshold voltage is the voltage at the common connection point of the second resistor R2 and the third resistor R3. When the amplitude of the audio waveform signal is greater than the first threshold voltage, the pulse level signal output by the first operational amplifier U1 is a high-level signal, indicating that the audio waveform signal contains human voice signals. When the amplitude of the audio waveform signal is less than or equal to the first threshold voltage, the pulse level signal output by the first operational amplifier U1 is a low-level signal, indicating that the audio waveform signal does not contain human voice signals and is noise.

[0066] In this embodiment, a first voltage divider circuit is formed by the second resistor R2 and the third resistor R3, so that the voltage divided by the third resistor R3 in the first voltage divider circuit is input to the inverting input terminal 3 of the first operational amplifier U1 as the first threshold voltage of the first operational amplifier U1. For example, the power supply VCC can be 3.3V, and the preset value can be 3.3V*R3 / (R2+R3)=1.711V.

[0067] Simultaneously, the first operational amplifier U1 compares the amplitude of the audio signal input at the non-inverting input terminal 1 with a first threshold voltage. When the amplitude of the audio signal is greater than the first threshold voltage, it outputs a first level signal (e.g., a high-level signal). When the amplitude of the audio signal is less than or equal to the first threshold voltage, it outputs a second level signal (e.g., a low-level signal).

[0068] Optionally, the comparison module 101 may further include resistors R101 and R102, with resistor R101 connected across the two ends of the second resistor R2 and resistor R102 connected across the two ends of the third resistor R3. Resistors R101 and R102 are used in conjunction with the second resistor R2 and the third resistor R3 to output a first threshold voltage to the inverting input terminal of the first operational amplifier U1.

[0069] Optionally, the comparison module 101 may further include a first capacitor filter circuit connected in series between the power supply VCC and the power supply terminal of the first operational amplifier U1.

[0070] The specific structure of the first capacitor filter circuit is not limited in the embodiments of this application. Any circuit that can perform the function of filtering the power supply VCC, thereby enabling the power supply VCC to stably output power to the first operational amplifier U1, can be used as the first capacitor filter circuit.

[0071] For example, such as Figure 4 As shown, the first capacitor filter circuit may include capacitors C101 and C102. One end of each capacitor is connected to the power supply VCC and the power supply terminal of the first operational amplifier U1, and the other end of each capacitor is grounded. Capacitors C101 and C102 are used to filter the power supply VCC, thereby ensuring a stable power output from VCC to the first operational amplifier U1.

[0072] For example, such as Figure 4 As shown, in one embodiment provided in this application, the comparison module 101 may further include a fourth resistor R4. One end of the fourth resistor R4 is connected to the output terminal of the first operational amplifier U1. In this embodiment, the transmission speed of the signal at the output terminal of the first operational amplifier U1 is limited by the fourth resistor R4.

[0073] Meanwhile, the audio circuit 10 also has a first LC filter circuit connected to the output of the comparison module 101 to filter the output signal of the first operational amplifier U1.

[0074] As an example, the first LC filter circuit may include a first inductor L1 and a first capacitor C1. The output terminal of the first operational amplifier U1 is connected to one end of the first capacitor C1 via the first inductor L1, the other end of the first capacitor C1 is grounded, and the common connection terminal of the first inductor L1 and the first capacitor C1 is connected to the input terminal of the switching module 102.

[0075] For example, if the comparison module 101 also includes a fourth resistor R4, the other end of the fourth resistor R4 is connected to one end of the first capacitor C1 through the first inductor L1, the other end of the first capacitor C1 is grounded, and the common connection terminal of the first inductor L1 and the first capacitor C1 is connected to the input terminal of the switch module 102.

[0076] Since audio signals are waveform signals, in order to ensure the continuity of the output signal of the comparison module 101, a first LC filter circuit can be formed by the first inductor L1 and the first capacitor C1 to filter the output signal of the first operational amplifier U1.

[0077] Optionally, the circuit provided in this application embodiment may also have a second LC filter circuit connected to the output terminal of the comparison module 101, which is used to cooperate with the first LC filter circuit to filter the output signal of the first operational amplifier U1.

[0078] As an example, the second LC filter circuit includes an inductor L101, a capacitor C103, an inductor L101 connected across the two ends of the first inductor L1, a capacitor C103 connected across the two ends of the first capacitor C1 and ground, and a resistor R103 connected to the output terminal of the first inductor L1. Thus, the inductor L101 and the capacitor C103 form the second LC filter circuit, which, together with the first LC filter circuit formed by the first inductor L1 and the first capacitor C1, filters the output signal of the first operational amplifier U1.

[0079] Optionally, the circuit provided in this application embodiment may also have a reserved resistor connected to the output terminal of the first LC filter circuit for later adjustment of current or voltage, etc.

[0080] As an example, the reserved resistor includes resistor R103, which serves as a reserved resistor to facilitate later adjustment of current or voltage, etc.

[0081] For example, such as Figure 4 As shown, in one embodiment provided in this application, the comparison module 101 further includes a second operational amplifier U2. The non-inverting input terminal 1 (e.g., the positive (+) inverting input terminal) of the second operational amplifier U2 is used to receive an audio signal.

[0082] Optionally, the comparison module 101 may also include a second protection device, which is connected in series between the output terminal of the first operational amplifier U1 and the non-inverting input terminal of the second operational amplifier U2. By setting the second protection device, excessive current can be prevented from impacting the second operational amplifier U2.

[0083] For example, the second protection device can be a current-limiting device. For instance, the second protection device can be a fifth resistor R5. For instance, the second protection device can also be a negative temperature coefficient thermistor or a positive temperature coefficient thermistor. For instance, the second protection device can also be a current-limiting device such as a fuse.

[0084] The inverting input terminal 3 (e.g., the negative (-) phase input terminal) of the second operational amplifier U2 is used to obtain a preset value. As an example, this preset value can be a pre-set value or a preset voltage division value obtained based on the power supply VCC.

[0085] For example, such as Figure 4 As shown, the inverting input terminal 3 (e.g., the negative (-) phase input terminal) of the second operational amplifier U2 is connected to the second voltage divider circuit. The power supply terminal of the second voltage divider circuit is connected to the power supply VCC and is used to provide a preset voltage divider value to the inverting input terminal 3 (e.g., the negative (-) phase input terminal) of the second operational amplifier U2 based on the power supply VCC.

[0086] For example, such as Figure 4As shown, the second threshold voltage is generated by dividing the power supply voltage VCC by the second voltage divider circuit. The second voltage divider circuit includes a sixth resistor R6 and a seventh resistor R7 connected in series. One end of the sixth resistor R6 is connected to the power supply voltage VCC, and one end of the seventh resistor R7 is grounded. The second threshold voltage is the voltage at the common connection point of the sixth resistor R6 and the seventh resistor R7.

[0087] In this embodiment, a second voltage divider circuit is formed by the sixth resistor R6 and the seventh resistor R7, so that the voltage divided by the seventh resistor R7 in the second voltage divider circuit is input to the inverting input terminal 3 of the second operational amplifier U2 as the preset value of the comparison module 101.

[0088] Simultaneously, the second operational amplifier U2 compares the amplitude of the audio signal input at the non-inverting input terminal 1 with the second threshold voltage. When the amplitude of the audio signal is greater than the second threshold voltage, it outputs a first-level signal (e.g., a high-level signal). When the amplitude of the audio signal is less than or equal to the second threshold voltage, it outputs a second-level signal (e.g., a low-level signal).

[0089] Optionally, the comparator module 101 may further include resistors R104 and R105, with resistor R104 connected across the sixth resistor R6 and resistor R105 connected across the seventh resistor R7. Resistors R104 and R105 are used in conjunction with the sixth resistor R6 and the seventh resistor R7 to output a second threshold voltage to the inverting input of the second operational amplifier U2.

[0090] Optionally, the comparison module 101 may also include a second capacitor filter circuit connected in series between the power supply VCC and the power supply terminal of the second operational amplifier U2.

[0091] The specific structure of the second capacitor filter circuit is not limited in the embodiments of this application. Any circuit that can perform the function of filtering the power supply VCC, thereby enabling the power supply VCC to stably output power to the second operational amplifier U2, can be used as the second capacitor filter circuit.

[0092] For example, such as Figure 4 As shown, the first capacitor filter circuit may include capacitors C104 and C105. One end of each capacitor is connected to the power supply VCC and the power supply terminal of the second operational amplifier U2, and the other end of each capacitor is grounded. Capacitors C104 and C105 are used to filter the power supply VCC, thereby ensuring a stable power output from VCC to the second operational amplifier U2.

[0093] For example, such as Figure 4As shown, in one embodiment provided in this application, the comparison module 101 may further include resistors R106 and R107, and capacitor C106. Resistor R106 limits the transmission speed of the signal at the output terminal of the second operational amplifier U2. Resistor R107 serves as a reserved resistor to adjust the current or voltage in the path. Capacitor C106 is used to filter the signal at the output terminal of the second operational amplifier U2.

[0094] Figure 5 This is a circuit diagram of an amplification module provided in an embodiment of this application. Figure 5 As shown, exemplarily, the amplification module 103 includes a third operational amplifier U3. The non-inverting input terminal 3 (e.g., the negative (-) phase input terminal) of the third operational amplifier U3 is used to connect a bias voltage, which provides a stable voltage to the third operational amplifier U3 so that the third operational amplifier U3 can operate in a stable state.

[0095] As an example, the non-inverting input 3 of the third operational amplifier U3 is connected to a third voltage divider circuit, which provides a bias voltage to the non-inverting input 3 of the third operational amplifier U3.

[0096] For example, such as Figure 5 As shown, the bias voltage is generated by dividing the power supply voltage VCC by the third voltage divider circuit. The third voltage divider circuit includes an eighth resistor R8 and a ninth resistor R9 connected in series. One end of the ninth resistor R9 is connected to the power supply voltage VCC, and one end of the eighth resistor R8 is grounded. The bias voltage is the voltage at the common connection point of the eighth resistor R8 and the ninth resistor R9.

[0097] In this embodiment, a third voltage divider circuit is formed by the eighth resistor R8 and the ninth resistor R9, so that the voltage divided by the eighth resistor R8 is used as the bias voltage of the non-inverting input terminal 3 of the third operational amplifier U3, such as VCC / 2. Then, according to the "virtual short and virtual open" working principle of the third operational amplifier U3, the voltage value of the inverting input terminal 3 of the third operational amplifier U3 is the same as the voltage value of the non-inverting input terminal 2 (such as the positive (+) phase input terminal).

[0098] As an example, the inverting input 2 of the third operational amplifier U3 is connected to a gain adjustment circuit, which is used to adjust the gain of the amplification module 103.

[0099] For example, such as Figure 5As shown, the amplification factor adjustment circuit may include: a tenth resistor R10, an eleventh resistor R11, and a twelfth resistor R12. The inverting input terminal 2 of the third operational amplifier U3 is connected to one end of the tenth resistor R10 and one end of the eleventh resistor R11, respectively. The other end of the tenth resistor R10 is connected to an audio signal, and the other end of the eleventh resistor R11 is connected to the output terminal 1 of the third operational amplifier U3 through the twelfth resistor R12.

[0100] In this embodiment, the voltage at the inverting input terminal 2 of the third operational amplifier U3 is equal to the bias voltage. The amplification factor of the amplification module 103 obtained through the tenth resistor R10, the eleventh resistor R11, and the twelfth resistor R12 is (R11+R12) / R10. Therefore, the amplified audio amplitude at the output terminal of the third operational amplifier U3 is: input audio amplitude * (R11+R12) / R10 + bias voltage.

[0101] Optionally, such as Figure 5 As shown, the amplification module 103 may further include a second capacitor C2, and the inverting input terminal 2 of the third operational amplifier U3 is connected to the audio signal through the second capacitor C2. The second capacitor C2 performs DC blocking and AC passing processing on the input audio signal.

[0102] It should be understood that the amplified noise amplitude at output terminal 1 of the third operational amplifier U3 can be: input noise amplitude * (R11 + R12) / R10 + margin. (This corresponds to the above...) Figure 4 The first threshold voltage of the first operational amplifier U1, 3.3V * R3 / (R2 + R3), should be equal to the input noise amplitude * (R11 + R12) / R10 + margin. Therefore, when the input signal is greater than the first threshold voltage, the first operational amplifier U1 outputs a first-level signal (e.g., a high-level signal), and when the amplitude of the input signal is less than or equal to the first threshold voltage, the first operational amplifier U1 outputs a second-level signal (e.g., a low-level signal). For example, the margin can be a manually estimated 0.02V.

[0103] It should be noted that the resistance values ​​of the second resistor R2, the third resistor R3, the tenth resistor R10, the eleventh resistor R11, and the twelfth resistor R12 can be evaluated based on the measured noise amplitude. For example, when the measured maximum noise is 10mV and the human voice is greater than 50mV, the noise can be amplified by 3 times, with a margin of 20mV. The resistance values ​​of the second resistor R2 and the third resistor R3 are equal, so that the preset value of the first operational amplifier U1 can be 3.3V*R3 / (R2+R3) + 10mV*3 + 20mV = 1.7V.

[0104] Optionally, the amplification module 103 may further include a second protection device and / or a third protection device. The second protection device is connected in series between the non-inverting input terminal 3 of the third operational amplifier U3 and ground. The third protection device is connected in series between the inverting input terminal 2 of the third operational amplifier U3 and the input audio signal.

[0105] For example, the second protection device can be a resistor R201 and the third protection device can be a resistor R202.

[0106] Among them, resistors R201 and R202 can be used as protection resistors for the non-inverting input and inverting input terminals of the third operational amplifier U3.

[0107] Optionally, the amplification module 103 may further include a resistor R203. The resistor R203 can form a voltage divider circuit with the tenth resistor R10 to adjust the voltage in the path of the tenth resistor R10.

[0108] Optionally, the amplification module 103 may further include resistors R204 and R205 connected in series. One end of resistor R204 is connected to the inverting input terminal 2 of the third operational amplifier U3, the other end of resistor R204 is connected to one end of resistor R205, and the other end of resistor R205 is connected to the output terminal 1 of the third operational amplifier U3.

[0109] The branch with resistors R204 and R205 connected in series is connected in parallel with the branch with resistors R11 and R12 connected in series. This allows the amplifier factor of the amplifier module 103 to be adjusted in conjunction with resistors R11 and R12.

[0110] Optionally, the amplification module 103 may further include: resistors R206, R207, R208, and R209, and capacitors C201, C202, C203, and C204. Resistors R206, R207, R208, and R209 can be used as reserved resistors to adjust the current or voltage at the output of the third operational amplifier U3. Capacitors C201, C202, C203, and C204 serve as filter capacitors.

[0111] Figure 6 This is a circuit diagram of a switching module provided in an embodiment of this application. Figure 6As shown, exemplarily, in one embodiment provided in this application, the switch module 102 includes an analog switch U4. The first pin 1 of the analog switch U4 is connected to an audio waveform signal (i.e., the first pin is connected to the output terminal of the comparison module 101), the second pin 2 of the analog switch U4 is grounded, the third pin 3 of the analog switch U4 is floating, the fourth pin 4 of the analog switch U4 is used to output an audio signal, the fifth pin 5 of the analog switch U4 is connected to the power supply VCC and is also grounded, and the sixth pin 6 of the analog switch U4 is grounded. The sixth pin 6 of the analog switch U4 is used to receive a control signal output by the comparison module 101. The control signal (e.g., a first level signal) is used to control the fourth pin and the first pin of the analog switch U4 to conduct, or the control signal (e.g., a second level signal) is used to control the fourth pin and the third pin of the analog switch U4 to conduct.

[0112] Optionally, the switch module 102 may further include a third capacitor C3. One end of the third capacitor C3 is connected to the fourth pin 4 of the analog switch U4, and the other end of the third capacitor C3 serves as the audio output terminal of the switch module 102. The output signal of the fourth pin 4 of the analog switch U4 is filtered by the third capacitor C3.

[0113] Optionally, the switch module 102 may further include a fourth capacitor C4. One end of the fourth capacitor C4 is connected to the fifth pin 5 of the analog switch U4, and the other end of the fourth capacitor C4 is grounded. The power supply VCC at the fifth pin 5 of the analog switch U4 is filtered through the fourth capacitor C4.

[0114] Optionally, the switch module 102 may further include a thirteenth resistor R13. One end of the thirteenth resistor R13 is connected to pin 6 of the analog switch U4, and the other end of the thirteenth resistor R13 is grounded. The thirteenth resistor R13 grounds pin 6 of the analog switch U4.

[0115] In this embodiment, when pin 6 of analog switch U4 receives a first-level signal (e.g., a high-level signal) output by comparator module 101, pins 4 and 1 of analog switch U4 are connected, allowing the audio waveform signal from pin 1 of analog switch U4 to be output through pin 4. When pin 6 of analog switch U4 receives a second-level signal (e.g., a low-level signal) output by comparator module 101, pins 4 and 3 of analog switch U4 are connected. Since pin 3 of analog switch U4 is left floating, pin 4 of analog switch U4 has no audio signal output.

[0116] Optionally, the switch module 102 also includes resistors R301 and R302. Resistor R301 is connected between the third pin 3 of the analog switch U4 and ground, thus ensuring that the third pin 3 of the analog switch U4 is floating. One end of resistor R302 is connected to the fourth pin 4 of the analog switch U4, and the other end of resistor R302 is connected to the audio signal line-in. Therefore, when the user does not need to use the functions of the comparator module 101 and the switch module 102, the input and output of the audio waveform signal can be directly connected. Thus, resistor R302 is usually not powered on.

[0117] For example, an embodiment of this application provides a camera, including an audio circuit 10.

[0118] In this embodiment, the audio circuit 10 is located inside the camera. A comparison module compares the amplitude of the audio signal with a preset value. When the amplitude of the audio signal is greater than the preset value, it is determined that the audio signal contains valid sound; otherwise, it is determined that the audio signal is noise. A switching module turns on to output the audio signal when the audio signal contains valid sound and turns off to stop outputting the audio signal when the audio signal is noise, thereby achieving noise reduction during idle time and reducing background noise when there is no human voice in the environment.

[0119] Specifically, the audio circuit 10 is located inside the camera. The audio waveform signal acquired by the camera is input to the first operational amplifier via the audio input terminal to generate a pulse level signal. The pulse level signal is filtered by the LC filter circuit and then input to the second operational amplifier to generate a DC level control signal. The DC level control signal includes a high-level signal and a low-level signal. When the DC level control signal is a high-level signal, the audio waveform signal is transmitted to the audio output terminal via the switching module and output; when the DC level control signal is a low-level signal, the switching module is open, and the audio waveform signal is blocked, thereby achieving noise reduction during idle time and reducing the background noise when there is no human voice in the environment.

[0120] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0121] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above-described camera can be referred to the corresponding process in the foregoing embodiments, and will not be repeated here.

[0122] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0123] Those skilled in the art will recognize that the units of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0124] In the embodiments provided in this application, it should be understood that the disclosed audio circuit can be implemented in other ways. For example, the audio circuit embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another camera, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some multi-interface cameras, devices, or units, and may be electrical, mechanical, or other forms.

[0125] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0126] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0127] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. An audio circuit, characterized by The audio circuit comprises an audio input end, a first operational amplifier, an LC filter circuit, a second operational amplifier, a switch module and an audio output end. The audio signal is input to the first operational amplifier through the audio input end to generate a pulse level signal; the pulse level signal is input to the second operational amplifier after being filtered by the LC filter circuit to generate a direct current level control signal; the direct current level control signal comprises a high level signal and a low level signal; when the direct current level control signal is the high level signal, the audio signal is transmitted to the audio output end through the switch module and is output; when the direct current level control signal is the low level signal, the switch module is disconnected, and the audio signal is blocked. The first operational amplifier is configured such that the non-inverting input end of the first operational amplifier is used to input the audio signal, and the inverting input end of the first operational amplifier is used to obtain a first threshold voltage; when the audio signal is greater than the first threshold voltage, the first operational amplifier outputs the pulse level signal. The second operational amplifier is configured such that the non-inverting input end of the second operational amplifier is used to input the output signal of the LC filter circuit, and the inverting input end of the second operational amplifier is used to obtain a second threshold voltage; when the output signal of the LC filter circuit is greater than the second threshold voltage, the second operational amplifier outputs the high level signal; when the output signal of the LC filter circuit is less than or equal to the second threshold voltage, the second operational amplifier outputs the low level signal. The first threshold voltage is used to indicate whether the audio signal contains a human voice signal. The second threshold voltage is used to control the conduction and shutdown of the switch module. The first threshold voltage is generated by dividing the power supply voltage by a first voltage dividing circuit, the first voltage dividing circuit comprising a second resistor and a third resistor connected in series, one end of the second resistor being connected to the power supply voltage, one end of the third resistor being grounded, and the first threshold voltage being the voltage at the common connection point of the second resistor and the third resistor; when the amplitude of the audio signal is greater than the first threshold voltage, the pulse level signal output by the first operational amplifier is a high level signal, indicating that the audio signal contains a human voice signal.

2. The audio circuit of claim 1, wherein, The second threshold voltage is generated by dividing the power supply voltage by a second voltage dividing circuit, the second voltage dividing circuit comprising a sixth resistor and a seventh resistor connected in series, one end of the sixth resistor being connected to the power supply voltage, one end of the seventh resistor being grounded, and the second threshold voltage being the voltage at the common connection point of the sixth resistor and the seventh resistor.

3. The audio circuit of claim 1, wherein, The audio circuit further comprises an amplification module, the input end of the amplification module being connected to the audio signal, and the output end of the amplification module being connected to the first operational amplifier.

4. The audio circuit of claim 1, wherein, The amplification module is used to amplify the audio signal. The amplification module comprises a third operational amplifier, a second capacitor, a third voltage dividing circuit and an amplification factor adjusting circuit.

5. The audio circuit of claim 4, wherein, ​ The noninverting input end of the third operational amplifier is connected with the voltage division end of the third voltage division circuit, the power supply end of the third voltage division circuit is connected with a power supply, and the grounding end of the third voltage division circuit is grounded; the inverting input end of the third operational amplifier is connected with the adjusting end of the amplification multiple adjusting circuit, the input end of the amplification multiple adjusting circuit is connected with the audio signal through the second capacitor, and the output end of the amplification multiple adjusting circuit is connected with the output end of the third operational amplifier.

6. The audio circuit of claim 5, wherein, The amplification multiple adjusting circuit comprises a tenth resistor, an eleventh resistor and a twelfth resistor. One end of the tenth resistor and one end of the eleventh resistor are both connected with the inverting input end of the third operational amplifier, the other end of the tenth resistor is connected with the audio signal through the second capacitor, and the other end of the eleventh resistor is connected with the output end of the third operational amplifier through the twelfth resistor.

7. An audio circuit as claimed in any one of claims 1 to 6, characterized in that, The audio circuit further comprises a volume adjusting module, the input end of the volume adjusting module is connected with the audio signal, and the output end of the volume adjusting module is connected with the input end of the switch module. The volume adjusting module is used for adjusting the volume of the audio signal.

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