Microphone amplifying circuit

Abstract

The utility model discloses a microphone amplifying circuit. Comprising an audio input interface, a first-stage voltage follower, a first filter circuit, a second-stage voltage follower, a second filter circuit, a third-stage voltage follower, a first inverse proportion operation amplification circuit, a fourth-stage voltage follower, a second inverse proportion operation amplification circuit, a fifth-stage voltage follower and a data acquisition card which are connected in sequence. One of the first filter circuit and the second filter circuit is a high-pass filter circuit, and the other one of the first filter circuit and the second filter circuit is a low-pass filter circuit. The system is low in noise, low in distortion, good in stability and anti-interference performance, and stable in work.

Description

Technical Field

[0001] The utility model relates to a microphone sound source amplification circuit. Background Art

[0002] A microphone amplification circuit is a circuit used to amplify microphone signals. A microphone, as a sound sensor, is used to convert sound signals into electrical signals. Since the signals generated by the microphone are weak, an amplification circuit is needed to enhance the signals for subsequent processing or driving other devices.

[0003] Although microphone amplification circuits are very useful in many applications, they also have some disadvantages that need to be considered and solved during design and use. The following are some of the disadvantages of microphone amplification circuits:

[0004] 1. Noise introduction: The amplification circuit itself may introduce noise, especially in the preamplifier section. Since the microphone signals are weak, the amplification circuit needs to have sufficient gain to amplify the signals, but too high gain may cause the noise to be amplified as well, thus reducing the signal quality;

[0005] 2. Distortion: The amplification circuit may introduce distortion when amplifying signals, especially at higher gains. Distortion may be caused by non-linear amplifier characteristics, power supply interference or other factors during the signal processing;

[0006] 3. Feedback problems: The feedback circuit of the amplification circuit may cause stability problems, especially in the high-frequency range. The design of the feedback circuit needs to be carefully handled to ensure that the amplification circuit works stably under various working conditions;

[0007] 4. Power supply noise and interference: Power supply noise and interference may enter the amplification circuit through the power line, affecting the signal quality. Especially when the power supply is unstable or there are other electrical devices near the power line, this problem may be more significant;

[0008] 5. Power consumption and heat: The high gain of the amplifier and the operation of the operational amplifier require power consumption, which may lead to high power consumption and generate a certain amount of heat. This requires considering heat dissipation and energy efficiency issues in the design. Summary of the Invention

[0009] The technical problem to be solved by the utility model is to provide a microphone amplification circuit with low noise, low distortion, good stability and anti-interference ability, and stable operation.

[0010] A microphone amplification circuit according to an embodiment of the present utility model includes an audio input interface, a first-stage voltage follower, a first filter circuit, a second-stage voltage follower, a second filter circuit, a third-stage voltage follower, a first inverse proportional operation amplifier circuit, a fourth-stage voltage follower, a second inverse proportional operation amplifier circuit, a fifth-stage voltage follower, and a data acquisition card connected in sequence; one of the first filter circuit and the second filter circuit is a high-pass filter circuit, and the other of the first filter circuit and the second filter circuit is a low-pass filter circuit.

[0011] For the above-mentioned microphone amplification circuit, the cut-off frequency of the high-pass filter circuit is 500 Hz, and the cut-off frequency of the low-pass filter circuit is 100 KHz.

[0012] For the above-mentioned microphone amplification circuit, the first-stage voltage follower to the fifth-stage voltage follower, the first inverse proportional operation amplifier circuit, and the second inverse proportional operation amplifier circuit are all powered by dual power supplies.

[0013] For the above-mentioned microphone amplification circuit, the microphone amplification circuit includes a Type-C interface, a 5V power supply industrial-grade interface, and a DC-DC conversion circuit. The input end of the DC-DC conversion circuit is electrically connected to the Tpye-C interface and the 5V power supply industrial-grade interface respectively, and is used to convert the 5V voltage output by the Tpye-C interface or the 5V power supply industrial-grade interface into a dual power supply.

[0014] The present utility model has at least the following advantages and characteristics:

[0015] 1. The embodiment of the present utility model adopts the design of inverse proportional operation amplification, which effectively eliminates the common-mode input signal. Even if the common-mode rejection ratio of the operational amplifier is not high, it ensures that there is no common-mode output, thereby effectively suppressing noise and improving the signal quality collected by the microphone;

[0016] 2. The embodiment of the present utility model adopts the design of dual power supply. Compared with single power supply, the dual power supply makes the total dynamic range, output voltage / current, accuracy, and load anti-interference of the amplification circuit superior to that of single power supply;

[0017] 3. The embodiment of the present utility model adopts the design of band-pass filtering, which effectively isolates the low-frequency signals below 500 Hz and the high-frequency signals above 100 KHz, so that the collected signals are kept within the best general bandwidth;

[0018] 4. The embodiment of the present utility model adopts the design of five voltage followers, which makes the input impedance extremely high, can effectively transmit the input signal to the operational amplifier, ensuring the stability and anti-interference ability of the circuit. At the same time, it makes the output impedance extremely low, improving the load-carrying capacity, avoiding the pull current of the input end of the inverting proportional operation amplifier circuit on the front end, and avoiding the influence of the front and rear stages of the band-pass filter circuit composed of the first-order high-pass filter circuit and the first-order low-pass filter circuit, so that the bandwidth is maintained between 500 Hz and 100 KHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. shows a schematic block diagram of a microphone amplifier circuit according to an embodiment of the present utility model.

[0020] Figure 2 FIG. shows a schematic circuit diagram of a specific embodiment of a microphone amplifier circuit according to an embodiment of the present utility model.

[0021] Figure 3 FIG. shows a schematic circuit diagram of a specific embodiment of a DC-DC conversion circuit according to an embodiment of the present utility model.

[0022] Figure 4 FIG. shows a schematic circuit diagram of a specific embodiment of an audio input interface according to an embodiment of the present utility model.

[0023] Figure 5 FIG. shows a schematic circuit diagram of a specific embodiment of an interface of a data acquisition card according to an embodiment of the present utility model.

[0024] Figure 6 and Figure 7 FIGS. respectively show schematic circuit diagrams of specific embodiments of a Type-C interface and a 5V power supply industrial-grade interface according to an embodiment of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The present utility model will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 FIG. shows a schematic block diagram of a microphone amplifier circuit according to an embodiment of the present utility model. Please refer to Figure 1 . The microphone amplifier circuit according to an embodiment of the present utility model includes an audio input interface 1, a first-stage voltage follower 21, a first filter circuit 31, a second-stage voltage follower 22, a second filter circuit 32, a third-stage voltage follower 23, a first inverting operation amplifier circuit 41, a fourth-stage voltage follower 24, a second inverting operation amplifier circuit 42, a fifth-stage voltage follower 25, a data acquisition card 5, a Type-C interface 61, a 5V power supply industrial-grade interface 62, and a DC-DC conversion circuit 7.

[0027] The audio input interface 1, the first - stage voltage follower 21, the first filter circuit 31, the second - stage voltage follower 22, the second filter circuit 32, the third - stage voltage follower 23, the first inverse - proportion operational amplifier circuit 41, the fourth - stage voltage follower 24, the second inverse - proportion operational amplifier circuit 42, the fifth - stage voltage follower 25 and the data acquisition card 5 are connected in sequence.

[0028] One of the first filter circuit 31 and the second filter circuit 32 is a high - pass filter circuit, and the other of the first filter circuit 31 and the second filter circuit 32 is a low - pass filter circuit. In this embodiment, the first filter circuit 31 is a high - pass filter circuit, and the second filter circuit 32 is a low - pass filter circuit.

[0029] The embodiment of the utility model adopts five - stage voltage followers, making the impedance of the circuit signal input end extremely high and the impedance of the signal output end extremely low. It can be free from the interference of the previous signal, ensuring the signal integrity to the greatest extent, greatly reducing the loss, and improving the load - carrying capacity for the output end.

[0030] The input end of the DC - DC conversion circuit 7 is respectively connected to the Type - C interface 61 and the 5V - powered industrial - grade interface 62, for converting the 5V voltage output by the Type - C interface or the 5V - powered industrial - grade interface into a dual - power supply (i.e., converting a single - power supply into a dual - power supply), and using this dual - power supply to supply power to the first - stage voltage follower to the fifth - stage voltage follower, the first inverse - proportion operational amplifier circuit 41 and the second inverse - proportion operational amplifier circuit 42. In this embodiment, the dual - power supply includes a + 10V power supply and a - 10V power supply.

[0031] The Type - C interface can be powered by a power adapter, which is small, compact and has a wide application range. Retaining the industrial - grade power supply interface can better meet the needs of the factory to a greater extent. Adopting the dual - power supply mode of + 10V and - 10V can ensure a better total dynamic range of the signal, more stable output voltage and current, higher precision and stronger load anti - interference ability compared with single - power - supply.

[0032] Figure 2The specific circuit structures of the first-stage voltage follower to the fifth-stage voltage follower, the first filter circuit 31, the second filter circuit 32, the first inverse proportional operational amplifier circuit 41, and the second inverse proportional operational amplifier circuit 42 are shown. Among them, the first-stage voltage follower 21 includes the operational amplifier U27B, and the first-stage voltage follower is used to ensure that the signal coming from the microphone will not affect the subsequent circuit. The first filter circuit 31 is a first-order high-pass filter circuit, which is composed of the capacitor C33 and the resistor R51, and can filter out signals below 500 Hz, that is, the cut-off frequency of the high-pass filter circuit is 500 Hz. The second-stage voltage follower 22 includes the operational amplifier U17A, and the second-stage voltage follower is used to ensure that the previous high-pass filter circuit will not affect the subsequent low-pass filter circuit. The second filter circuit 32 is a first-order low-pass filter circuit, which is composed of the resistor R48 and the capacitor C34, and can filter out signals above 100 KHz, that is, the cut-off frequency of the low-pass filter circuit is 100 KHz. By effectively isolating the low-frequency signals below 500 Hz and the high-frequency signals above 100 KHz, the collected signals can be kept within the optimal general bandwidth. The third-stage voltage follower 23 includes the operational amplifier U17B, and the third-stage voltage follower ensures that the previous low-pass filter circuit will not affect the subsequent amplifier circuit. The first inverse proportional operational amplifier circuit 41 is composed of the operational amplifier U18A, the resistor R46, the resistor R49, and the resistor R52, and the amplification factor is 4.3 times. The fourth-stage voltage follower 24 includes the operational amplifier U18B, and the fourth-stage voltage follower ensures that the previous amplifier circuit does not affect the subsequent amplifier circuit. The second inverse proportional operational amplifier circuit 42 is composed of the operational amplifier U19A, the resistor R47, the resistor R50, and the resistor R53, and the amplification factor is 6.8 times. The fifth-stage voltage follower 25 includes the operational amplifier U19B, and the fifth-stage voltage follower ensures that the previous amplifier circuit does not affect the subsequent acquisition card recognition. All of the aforementioned operational amplifiers use the operational amplifier with the model OPA2172 produced by Texas Instruments.

[0033] In the embodiment of the present invention, by using appropriate compensation resistors (resistors R46 and R47), a suitable static bias is provided for the transistors inside the operational amplifier chip, avoiding damage to the operational amplifier and eliminating the influence of the static base current on the output voltage.

[0034] Figure 3The circuit schematic diagram of a specific implementation manner of the DC-DC conversion circuit according to an embodiment of the present invention is shown. In this specific implementation manner, the DC-DC conversion circuit 7 includes a dual-output DC-DC converter chip U34 of model TPS65131 and its peripheral circuit, which boosts 5V to +10V and steps down 5V to -10V, thereby realizing the dual-power supply of +10V and -10V for the aforementioned operational amplifier. Among them, the switching transistor Q1 is responsible for switching the input power supply of 5V. When the pin ENP of the dual-output DC-DC converter chip U34 is at a high level, the switching transistor Q1 is turned off. When the pin ENP is at a low level, the switching transistor Q1 is turned on. The function of the capacitor C39 is to filter out the redundant ripples of the input power supply. The function of the inductor L3 is to suppress the high pulses of the input power supply. The function of the diode D8 is to prevent the high voltage at the output end from being fed back to the input end. The function of the bead R70 is to provide a stable power supply for the input end and a stable voltage state for the pins ENP, PSP, ENN, and PSN. The function of the capacitor C40 is to filter out the redundant ripples of the input power supply. The capacitor C41 plays a bypass role and provides a stable power supply state for the inside of the chip. The resistor R79 and the light-emitting diode D10 form the first LED display part, which lights up when the +10V power supply is powered on and goes out when there is no power; the resistor R80 and the light-emitting diode D11 form the second LED display part, which lights up when the -10V power supply is powered on and goes out when there is no power. The resistors R71, R73, and the capacitor C42 form a +10V output feedback circuit for detecting the power supply voltage in a timely manner; the resistors R72, R74, and the capacitor C44 form a -10V output feedback circuit for detecting the external power supply voltage in a timely manner. The capacitor C48 is a filter and voltage stabilizing capacitor for the +10V power supply output to ensure the stability of the output voltage. The capacitor C43 is a bypass capacitor for the VREF reference power supply pin. The diode D9, the inductor L4, and the capacitor C47 form a -10V output circuit to provide a stable -10V power supply. The capacitor C45 is a compensation capacitor for +10V. The capacitor C46 is a compensation capacitor for -10V.

[0035] Figure 4 The schematic diagram of a specific implementation manner of the audio input interface according to an embodiment of the present invention is shown. In this specific implementation manner, the audio input interface 1 adopts a BNC audio input interface J4.

[0036] Figure 5 The schematic diagram of a specific implementation manner of the interface of the data acquisition card (DAQ acquisition card) according to an embodiment of the present invention is shown. In this implementation manner, the interface P1 of the data acquisition card 5 is a 25-pin plug. Figure 6 and Figure 7Schematic diagrams respectively show a specific implementation of a Type-C interface and a 5V-powered industrial-grade interface according to an embodiment of the present invention. In this implementation, the Type-C interface 61 is composed of a Type-C interface U36. The CC1 pin and the SBU1 pin of the Type-C interface U36 are respectively grounded through a pull-down identification resistor R81 and a pull-down identification resistor R82, and after being pulled down, it serves as a power-receiving party (slave). The 5V-powered industrial-grade interface is composed of an industrial-grade power interface J9.

[0037] The microphone sound source input signal is 0.18V, which is input through a BNC interface, passes through a first-order high-pass filter and a first-order low-pass filter, undergoes an inverse proportional operation amplification by 4.3 times, and then undergoes an inverse proportional operation amplification by 6.8 times and outputs 5.263V to the data acquisition card. The host computer can read the signal collected by the data acquisition card for judgment and processing. This microphone amplification circuit has the advantages of simplicity and reliability.

[0038] Embodiments of the present invention solve problems existing in the prior art, such as weak microphone sound sources, noise introduction, distortion, feedback compensation, and high power consumption during the amplification process, by adopting technical means such as dual-power supply, inverting proportional operation amplification of the input, high-impedance input at the input end, and isolation between the power supply end and the signal end.

Claims

1. A microphone amplifier circuit, characterized in that: It includes an audio input interface, a first-stage voltage follower, a first filtering circuit, a second-stage voltage follower, a second filtering circuit, a third-stage voltage follower, a first inverse proportional operational amplifier circuit, a fourth-stage voltage follower, a second inverse proportional operational amplifier circuit, a fifth-stage voltage follower and a data acquisition card which are connected in sequence; One of the first filter circuit and the second filter circuit is a high-pass filter circuit, and the other of the first filter circuit and the second filter circuit is a low-pass filter circuit.

2. The microphone amplifier circuit according to claim 1, characterized in that: The cut-off frequency of the high-pass filter circuit is 500 Hz, and the cut-off frequency of the low-pass filter circuit is 100 KHz.

3. The microphone amplifier circuit according to claim 1 or 2, characterized in that: The first filter circuit is a first-order high-pass filter circuit, and the second filter circuit is a first-order low-pass filter circuit.

4. The microphone amplifier circuit according to claim 1, characterized in that: The first-stage voltage follower to the fifth-stage voltage follower, the first inverse proportional operational amplifier circuit and the second inverse proportional operational amplifier circuit are all powered by dual power supplies.

5. The microphone amplifier circuit according to claim 4, characterized in that: The dual power supply includes a +10V power supply and a -10V power supply.

6. The microphone amplifier circuit according to claim 4 or 5, characterized in that: The microphone amplification circuit includes a Type-C interface, a 5V power supply industrial-grade interface and a DC-DC conversion circuit. The input end of the DC-DC conversion circuit is electrically connected to the Type-C interface and the 5V power supply industrial-grade interface, respectively, to convert the 5V voltage output by the Type-C interface or the 5V power supply industrial-grade interface into the dual power supply.

7. The microphone amplifier circuit according to claim 1, characterized in that: The audio input interface is a BNC audio input interface.

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