CN106911984B - Sound sensing circuit based on operational amplifier - Google Patents
Sound sensing circuit based on operational amplifier Download PDFInfo
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- CN106911984B CN106911984B CN201710039547.6A CN201710039547A CN106911984B CN 106911984 B CN106911984 B CN 106911984B CN 201710039547 A CN201710039547 A CN 201710039547A CN 106911984 B CN106911984 B CN 106911984B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2420/00—Details of connection covered by H04R, not provided for in its groups
- H04R2420/01—Input selection or mixing for amplifiers or loudspeakers
Abstract
The invention designs an operational amplifier-based sound sensing circuit which is used for detecting sound and generating a sound sensing signal. The sound signal detection circuit generates an electric signal through sound input equipment and transmits the electric signal to the first-stage amplification circuit, the signal is processed through the signal processing circuit after being amplified, specifically, the signal is subjected to alternating current coupling through a capacitor C3 and envelope detection through a capacitor C4, the signal is amplified through the second-stage amplification circuit, and then a shaping signal is generated through a Schmidt shaping circuit in the shaping circuit and is output through an inverter. Through detection, the circuit effectively identifies the sound signals with the frequency below 20kHz, has low power consumption, has the quiescent current of about 250 muA, can control the working state of the circuit by signals due to the circuit with an enable end, and can reduce the whole power consumption when being combined with other chips for application.
Description
Technical Field
The invention belongs to the field of integrated circuits, and particularly relates to an acoustic sensing circuit based on an operational amplifier
Background
Nowadays, the sound sensing circuit is built by discrete elements connected with the outside, the built circuit is very complex, and the accuracy value of the elements is greatly floated and has poor consistency, so that each product needs to be debugged, the cost is high, and the sound sensing circuit is not suitable for mass production.
Disclosure of Invention
The invention aims to provide an operational amplifier-based sound sensing circuit to solve the problems.
In order to achieve the purpose, the invention provides the following technical scheme:
the acoustic sensing circuit based on the operational amplifier is characterized by comprising an acoustic signal detection circuit, a primary amplification circuit, a signal processing circuit, a secondary amplification circuit and a shaping circuit.
The sound signal detection circuit is used for detecting a sound signal and comprises a microphone (microphone) MC, a resistor R1, a capacitor C1 and an NMOS transistor M1 serving as a switch. Specifically, the positive terminal of the microphone MC is connected to the input voltage Vin, the negative terminal is connected to the drain of the M1 through a resistor R1, the M1 source electrode substrate is grounded, the M1 gate is connected to the control signal CE, and the capacitor C1 is connected to the positive terminal of the microphone MC and the M1 source.
The primary amplifying circuit is used for amplifying the detected sound input signal and comprises an operational amplifier 1 controlled by an enabling signal, resistors R2 and R3 and a capacitor C2. The operational amplifier 1 enables a signal CE, a positive input end is connected with a negative end of a Microphone (MC), an output end is connected with a negative input end through a resistor R2, meanwhile, the negative input end is connected with a ground filter capacitor C2 through a bias resistor R3, and the other end of a capacitor C2 is grounded.
The signal processing circuit is used for processing the amplified signal and comprises a coupling capacitor C3, diodes D1 and D2, an envelope detection capacitor C4 and a pull-down resistor R4. The specific processing mode is that the signal firstly filters out direct current components through a coupling capacitor C3, and then envelope detection is carried out on the signal through an envelope detection capacitor C4. Specifically, one end of a coupling capacitor C3 is connected with the output end of the operational amplifier 1, the other end of the coupling capacitor C3 is connected with the negative end of a diode D1, the positive end of a D1 is grounded, one end of an envelope detection capacitor C4 is grounded, the other end of the envelope detection capacitor C4 is connected with the negative end of a diode D2, the positive end of a diode D2 is connected with the negative end of a D1, and a pull-down resistor R4 is connected with.
The second-stage amplifying circuit is used for amplifying the processed signal and comprises an operational amplifier 2 controlled by an enabling signal, resistors R5 and R6. The operational amplifier 2 enables the signal CE, the positive input terminal is connected to the negative terminal of D2, the output terminal is connected to the negative input terminal through the feedback resistor R5, and the negative input terminal is grounded through the resistor R6.
The shaping circuit is used for shaping the output signal of the secondary amplifying circuit and comprises a Schmitt shaping circuit with an enabling end and an inverter circuit. The Schmitt shaping circuit enables the signal to be CE, the input end of the Schmitt shaping circuit is connected with the output end of the secondary amplifier, the output end of the Schmitt shaping circuit is connected with the input end of the phase inverter, and finally the output end of the phase inverter outputs the sound sensing signal.
The principle and the working mode are as follows:
(1) vin supplies power to all devices in the circuit, and the input voltage range is 3-5V, and the typical value is 3.3V.
(2) The CE signal controls the working states of the sound signal detection circuit, the two amplifying circuits and the shaping circuit, when the CE is 1, the circuit is in the working state, and when the CE is 0, the circuit is in the closing state.
(3) The capacitor C1 connected in parallel with the two ends of the power supply is used for eliminating voltage fluctuation, the resistor R1 is used for controlling the current of the microphone, and the sound signal is sensed by the microphone MC and generates an analog signal which is transmitted to the primary amplifying circuit.
(4) In the primary amplifying circuit, a voltage series negative feedback branch circuit is formed by resistors R2 and R3, an in-phase proportional operational circuit is formed by the resistors and the operational amplifier 1, an input analog signal is amplified by adjusting the resistance values of R2 and R3 and is transmitted to a signal processing circuit, and a capacitor C2 is used for increasing the voltage following capacity, isolating earth elastic interference and adjusting the phase margin to prevent oscillation.
(5) The coupling capacitor C3 is used to ac couple the signal and remove the dc component of the signal, which makes the circuit immune to white noise, and only the ac signal generated when the sound signal is received will pass through the capacitor C3.
(6) The capacitor C4 and the diodes D1 and D2 are used for detecting the envelope of the AC coupled signal, wherein the D1 and D2 are used for carrying out unidirectional filtering on the signal, the D1 filters a negative envelope to the ground, the D2 allows the positive envelope to pass through the capacitor C4, a low-frequency signal is detected and transmitted to a secondary amplifying circuit, and the pull-down resistor R4 is used for inhibiting offset voltage.
(7) In the secondary amplifying circuit, the resistors R5 and R6 form a voltage series negative feedback branch circuit, and form an in-phase proportional operational circuit together with the operational amplifier 2, and the input analog signal is amplified by adjusting the resistance values of R5 and R6 and transmitted to the shaping circuit.
(8) The Schmitt circuit in the shaping circuit is used for converting a signal with slowly changed edges output by the secondary amplifying circuit into a rectangular pulse signal with steep edges, when an input signal is less than 0.7V, the output of the Schmitt circuit is high, when the input signal is more than 0.7V, the output of the Schmitt circuit is low, and the subsequent inverter is matched to logically invert the signal, so that an acoustic sensing signal obtained when the input signal is more than 0.7V is high, and an acoustic sensing signal obtained when the input signal is less than 0.7V is low.
Compared with the prior art, the technical scheme of the invention has the following advantages and effects:
1. because the circuit has the Schmitt shaping circuit, the output waveform of the circuit is more stable.
2. Because the circuit adopts an integral structure instead of being built, the complexity of the circuit is reduced, and the circuit is more stable without a large amount of debugging.
3. The circuit controls the working state by the enabling signal CE, can be opened or closed according to the requirement, and is more convenient to be matched with other circuits for use.
4. The overall circuit power consumption is low, only 250 muA.
Drawings
Fig. 1 is an electrical schematic diagram of the operational amplifier based acoustic sensing circuit of the present invention.
Fig. 2 is a circuit waveform diagram extracted by the finished chip test of the operational amplifier-based sound sensing circuit of the invention.
Fig. 3 is a packaging diagram of SOP14 pins of the operational amplifier-based acoustic sensing circuit chip of the present invention.
Fig. 4 is a packaging diagram of SOP16 pins of the operational amplifier-based acoustic sensing circuit chip of the present invention.
Pin description in fig. 3:
1-CB operational amplifier 1 output pin
2-VINP sound signal input pin
3-VDD Power input Pin
4-GND ground pin
5-NC null pin
6-NC null pin
7-CE enable signal pin
8-RA microphone current control pin
9-NC null pin
10-NC null pin
Negative input terminal pin of 11-CA operational amplifier 1
12-Vout output pin
13-CD operational amplifier 2 positive input pin
14-CC coupling capacitance input pin
Pin description in fig. 4:
1-NC null pin
2-NC null pin
3-NC null pin
4-GND ground pin
5-CE enable signal pin
Current control pin of 6-RA microphone
7-CA operational amplifier 1 negative input end pin
8-Vout output pin
Positive input pin of 9-CD operational amplifier 2
10-CC coupling capacitance input pin
11-CB operational amplifier 1 output pin
12-VINP sound signal input pin
13-VDD Power input Pin
14-NC null pin
15-NC null pin
16-NC null pin
Detailed Description
In order to better understand the technical content of the invention, specific examples are described below with reference to the accompanying drawings.
Fig. 1 shows an electrical schematic diagram of an operational amplifier-based audio sensing circuit according to the present invention. The invention relates to an operational amplifier-based sound sensing circuit which comprises a sound signal detection circuit, a primary amplification circuit, a signal processing circuit, a secondary amplification circuit and a shaping circuit. The enable signal CE controls the operating states of M1, op amp 1, op amp 2, and the schmitt shaping circuit. The positive terminal of the Microphone (MC) is connected with an input voltage Vin, the negative terminal of the Microphone (MC) is connected to the drain electrode of the M1 through a resistor R1, the source electrode of the M1 is grounded, the grid electrode of the M1 is connected with a control signal CE, and a capacitor C1 is connected to the positive terminal of the Microphone (MC) and the source electrode of the NMOS tube M1 in a bridging mode. The operational amplifier 1 has a positive input connected to the negative terminal of the microphone MC, an output connected to the negative input through a feedback resistor R2, a negative input connected to a capacitor C2 through a resistor R3, and the other end of the capacitor C2 connected to ground. One end of a coupling capacitor C3 is connected with the output end of the operational amplifier 1, the other end of the coupling capacitor C3 is connected with the negative end of a diode D1, the positive end of a D1 is grounded, one end of an envelope detection capacitor C4 is grounded, the other end of the envelope detection capacitor C4 is connected with the negative end of a diode D2, the positive end of a diode D2 is connected with the negative end of a D1, and a pull-down resistor R4 is. The operational amplifier 2 has a positive input connected to the negative terminal of D2, an output connected to the negative input through a feedback resistor R5, and a negative input connected to ground through a resistor R6. The input end of the Schmitt shaping circuit is connected with the output end of the secondary amplifier, the output end of the Schmitt shaping circuit is connected with the input end of the phase inverter, and finally the output end of the phase inverter outputs the sound sensing signal.
The working principle of the invention is as follows:
referring to fig. 1 and fig. 2, fig. 2 is a waveform diagram of the operational amplifier-based acoustic sensing circuit according to the present invention.
Vin supplies power to all devices in the circuit, CE signals control the working states of the sound signal detection circuit, the two amplification circuits and the shaping circuit, when CE is 1, the circuit is in the working state, and when CE is 0, the circuit is in the closed state. The capacitor C1 connected in parallel with the two ends of the power supply is used for eliminating voltage fluctuation, the resistor R1 is used for controlling the current of the microphone MC, and the sound signal is sensed by the microphone MC and generates an analog signal which is transmitted to the primary amplifying circuit. In the first-stage amplifying circuit, resistors R2 and R3 form a voltage series negative feedback branch circuit, the voltage series negative feedback branch circuit and the operational amplifier 1 form an in-phase proportional operational circuit, and input analog signals are amplified and transmitted to a signal processing circuit by adjusting resistance values of R2 and R3.
The amplification ratio of the operational amplifier 1 is:
the coupling capacitor C3 is used to ac couple the signal and remove the dc component from the signal. The capacitor C4 and the diodes D1 and D2 are used for carrying out envelope detection on the signals after alternating current coupling and transmitting the signals to the second-stage amplifying circuit, and the pull-down resistor R4 is used for inhibiting offset voltage. The resistors R5 and R6 form a voltage series negative feedback branch circuit, form an in-phase proportional operational circuit together with the operational amplifier 2, amplify the input analog signal by adjusting the resistance values of R5 and R6, and transmit the amplified analog signal to the shaping circuit.
The amplification ratio of the operational amplifier 2 is:
the shaping circuit is used for converting the signal with slowly changing edges output by the secondary amplifying circuit into a rectangular pulse signal with steep edges, so that the acoustic sensing signal obtained when the input signal is more than 0.7V is high, and the acoustic sensing signal obtained when the input signal is less than 0.7V is low. This results in a more clearly perceived sound signal.
The foregoing examples are intended to illustrate rather than limit the invention, which may be modified and varied by those skilled in the relevant art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (1)
1. An operational amplifier-based sound sensing circuit is characterized by comprising a sound signal detection circuit, a primary amplification circuit, a signal processing circuit, a secondary amplification circuit and a shaping circuit;
the sound signal detection circuit is used for detecting a sound input signal and comprises a Microphone (MC), a resistor R1, a capacitor C1 and an NMOS transistor M1 serving as a switch; specifically, the positive terminal of the Microphone (MC) is connected with an input voltage Vin, the negative terminal of the Microphone (MC) is connected to the drain of the M1 through a resistor R1, the source of the M1 and the substrate are grounded, the gate of the M is connected with a control signal CE, and a capacitor C1 is connected across the positive terminal of the Microphone (MC) and the source of the M1;
the primary amplifying circuit is used for amplifying the detected sound input signal and comprises an operational amplifier 1 controlled by an enabling signal, resistors R2 and R3 and a capacitor C2; specifically, the enabling signal of the operational amplifier 1 is CE, the positive input end is connected to the negative end of the microphone MC, the output end is connected to the negative input end through the feedback resistor R2, meanwhile, the negative input end is connected to the ground filter capacitor C2 through the resistor R3, and the other end of the capacitor C2 is grounded;
the signal processing circuit is used for processing the amplified signal and comprises a coupling capacitor C3, diodes D1 and D2, an envelope detection capacitor C4 and a pull-down resistor R4; the specific processing mode is that the signal is firstly filtered to remove direct current components through a coupling capacitor C3, and then envelope detection is carried out on the signal through an envelope detection capacitor C4; specifically, one end of a coupling capacitor C3 is connected with the output end of the operational amplifier 1, the other end of the coupling capacitor C3 is connected with the negative end of a diode D1, the positive end of a D1 is grounded, one end of an envelope detection capacitor C4 is grounded, the other end of the envelope detection capacitor C4 is connected with the negative end of a diode D2, the positive end of a diode D2 is connected with the negative end of a D1, and a pull-down resistor R4 is connected to;
the secondary amplifying circuit is used for amplifying the processed signals and comprises an operational amplifier 2 controlled by an enabling signal, resistors R5 and R6; specifically, the enabling signal of the operational amplifier 2 is CE, the positive input end is connected to the negative end of D2, the output end is connected to the negative input end through a feedback resistor R5, and meanwhile, the negative input end is grounded through a resistor R6;
the shaping circuit is used for shaping the output signal of the secondary amplifying circuit and comprises a Schmitt shaping circuit with an enabling end and an inverter circuit; the Schmitt shaping circuit enables the signal to be CE, the input end of the Schmitt shaping circuit is connected with the output end of the secondary amplifier, the output end of the Schmitt shaping circuit is connected with the input end of the phase inverter, and finally, the output end of the phase inverter outputs the sound sensing signal;
vin supplies power to all devices in the circuit, and the range of voltage which can be input is 3-5V;
the CE signal controls the working states of the sound signal detection circuit, the two amplification circuits and the shaping circuit, when the CE is 1, the circuit is in the working state, and when the CE is 0, the circuit is in the closing state;
the capacitor C1 connected in parallel at two ends of the power supply is used for eliminating voltage fluctuation, the resistor R1 is used for controlling the current of the microphone, and the sound signal is sensed by the microphone MC and generates an analog signal which is transmitted to the first-stage amplifying circuit;
in the primary amplifying circuit, a resistor R2 and a resistor R3 form a voltage series negative feedback branch circuit, the voltage series negative feedback branch circuit and the operational amplifier 1 form an in-phase proportional operational circuit, an input analog signal is amplified by adjusting the resistance values of R2 and R3 and is transmitted to a signal processing circuit, a capacitor C2 is used for increasing the voltage following capacity, isolating earth elastic interference and adjusting the phase margin to prevent oscillation;
the coupling capacitor C3 is used for AC coupling the signal and eliminating the DC component in the signal, which makes the circuit not affected by white noise, only the AC signal generated when receiving the sound signal will pass through the capacitor C3;
the capacitor C4 and the diodes D1 and D2 are used for carrying out envelope detection on the signals after alternating current coupling, wherein the D1 and D2 are used for carrying out unidirectional filtering on the signals, the D1 filters negative envelopes to the ground, the D2 allows the positive envelopes to pass through the capacitor C4, low-frequency signals are detected and transmitted to a secondary amplification circuit, and the pull-down resistor R4 is used for inhibiting offset voltage;
in the secondary amplifying circuit, a voltage series negative feedback branch circuit is formed by resistors R5 and R6, an in-phase proportional operational circuit is formed by the resistors and the operational amplifier 2, and an input analog signal is amplified and transmitted to a shaping circuit by adjusting the resistance values of R5 and R6;
the Schmitt circuit in the shaping circuit is used for converting a signal with slowly changed edges output by the secondary amplifying circuit into a rectangular pulse signal with steep edges, when an input signal is less than 0.7V, the output of the Schmitt circuit is high, when the input signal is more than 0.7V, the output of the Schmitt circuit is low, and the subsequent phase inverter is matched for logically inverting the signal, so that an acoustic sensing signal obtained when the input signal is more than 0.7V is high, and an acoustic sensing signal obtained when the input signal is less than 0.7V is low;
in the first-stage amplifying circuit, resistors R2 and R3 form a voltage series negative feedback branch circuit, the voltage series negative feedback branch circuit and the operational amplifier 1 form an in-phase proportional operational circuit, and input analog signals are amplified and transmitted to a signal processing circuit by adjusting the resistance values of R2 and R3;
the amplification ratio of the operational amplifier 1 is:
the resistors R5 and R6 form a voltage series negative feedback branch circuit, form an in-phase proportional operational circuit together with the operational amplifier 2, amplify the input analog signal by adjusting the resistance values of R5 and R6, and transmit the amplified analog signal to the shaping circuit;
the amplification ratio of the operational amplifier 2 is:
the shaping circuit is used for converting the signal with slowly changed edges output by the secondary amplifying circuit into a rectangular pulse signal with steep edges, so that the acoustic sensing signal obtained when the input signal is more than 0.7V is high, and the acoustic sensing signal obtained when the input signal is less than 0.7V is low, and a clearer acoustic sensing signal is obtained.
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| CN108306637B (en) * | 2018-01-24 | 2021-09-21 | 北京时代民芯科技有限公司 | Charge pump phase-locked loop adopting double-circuit voltage to control voltage-controlled oscillator |
| CN110297275B (en) * | 2019-06-03 | 2020-09-25 | 南京工业职业技术学院 | Take AGC double-circuit to detect electronic fence sensor |
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| CN2307289Y (en) * | 1997-09-01 | 1999-02-10 | 陈英涛 | Sound corrector for pocket computer |
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Effective date of registration: 20221208 Address after: Room 373, Unit 5, Building 1, No. 688, Qiushi Road, Jinshanwei Town, Jinshan District, Shanghai, 200540 Patentee after: Shanghai Jieshun Technical Service Center Address before: 200092 Siping Road 1239, Shanghai, Yangpu District Patentee before: TONGJI University |
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Effective date of registration: 20221216 Address after: 201100 Room A53, Floor 2, Building 6, No. 4299, Jindu Road, Minhang District, Shanghai Patentee after: SHANGHAI TAIXI ELECTRONIC TECHNOLOGY CO.,LTD. Address before: Room 373, Unit 5, Building 1, No. 688, Qiushi Road, Jinshanwei Town, Jinshan District, Shanghai, 200540 Patentee before: Shanghai Jieshun Technical Service Center |
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