Vehicle-mounted MIC conversion circuit

Abstract

This application relates to an in-vehicle microphone (MIC) conversion circuit. The in-vehicle MIC conversion circuit includes: a MIC input amplifier circuit, a MIC signal conversion circuit, and a noise reduction circuit; the MIC input amplifier circuit amplifies the MIC signal and outputs an amplified first signal; the MIC signal conversion circuit is connected to the MIC input amplifier circuit, and processes the first signal to obtain a second signal with an AC component opposite to the first signal; the noise reduction circuit is connected to the MIC signal conversion circuit. The solution provided by this application has lower cost and higher amplification factor, voltage adaptability, and adjustability.

Description

Technical Field

[0001] This application relates to the field of new energy vehicle technology, and in particular to on-board microphone conversion circuits. Background Technology

[0002] In related technologies, existing automotive single-ended MIC input circuits typically use dedicated CODEC chips to amplify and convert MIC signals. However, CODEC chips are expensive, resulting in a higher overall price. Furthermore, the signal amplitude output by CODEC chips is limited, and the signal amplitude is generally relatively small. Summary of the Invention

[0003] To address or partially address the problems existing in related technologies, this application provides an in-vehicle microphone conversion circuit that can reduce costs and offers higher amplification, voltage adaptability, and adjustability.

[0004] This application provides an in-vehicle microphone conversion circuit, which includes a microphone input amplifier circuit, a microphone signal conversion circuit, and a noise reduction circuit. The microphone input amplifier circuit is used to amplify the microphone signal and output an amplified first signal. The microphone signal conversion circuit is connected to the microphone input amplifier circuit and is used to process the first signal to obtain a second signal with an AC component opposite to the first signal. The noise reduction circuit is connected to the microphone signal conversion circuit.

[0005] Further, the MIC input amplifier circuit includes a MIC input terminal, an operational amplifier power supply VCC, capacitors C1 and C2, resistors R1, R2, R3, and R4, a bias voltage Vbia1, an operational amplifier U1, and a Zener diode D1. Capacitor C1 is connected to the MIC input terminal and one end of resistor R1. The operational amplifier power supply VCC is connected to the power supply terminal of operational amplifier U1. The non-inverting terminal of operational amplifier U1 is connected to the other end of resistor R1, resistor R2, and Zener diode D1. The other end of resistor R2 is connected to the bias voltage Vbia1. The inverting terminal of operational amplifier U1 is connected to one end of resistor R3 and resistor R4. Capacitor C2 is connected to the other end of resistor R3 and Zener diode D1. The other end of resistor R4 is connected to the output terminal of operational amplifier U1.

[0006] Furthermore, the bias voltage Vbia1 should be greater than half the sum of the voltage at the MIC input terminal and the voltage at the operational amplifier power supply VCC.

[0007] Furthermore, the maximum value of the voltage of the first signal is less than or equal to the voltage of the operational amplifier power supply VCC.

[0008] Furthermore, the resistance value of the resistor R1 is less than or equal to 4.7K ohms.

[0009] Furthermore, the MIC signal conversion circuit includes an operational amplifier U2 and a bias voltage Vbia2, with the non-inverting terminal of the operational amplifier U2 connected to the bias voltage Vbia2.

[0010] Furthermore, the MIC signal conversion circuit also includes resistors R5, R6, and R7. The inverting terminal of the operational amplifier U2 is connected to one end of resistor R5 and one end of resistor R6, respectively. The other end of resistor R5 is connected to the output terminal of the MIC input amplifier circuit. Resistor R7 is connected to the bias voltage Vbia2 and the non-inverting terminal of the operational amplifier U2, respectively. The output terminal of the operational amplifier U2 is connected to the other end of resistor R6.

[0011] Furthermore, the noise reduction circuit includes capacitor C5 and capacitor C6. Capacitor C5 is connected to capacitor C6 and the output terminal of operational amplifier U2, respectively, and the other end of capacitor C6 is used for grounding.

[0012] Furthermore, the resistance value of the resistor R5 is less than 10K ohms.

[0013] Furthermore, the noise reduction circuit includes capacitor C3 and capacitor C4. Capacitor C3 is connected to capacitor C4 and the output terminal of the MIC input amplifier circuit, respectively, and the other end of capacitor C4 is used for grounding.

[0014] The technical solution provided in this application may include the following beneficial results: the MIC signal is amplified by the MIC input amplifier circuit, and the amplified MIC signal is differentially converted by the MIC signal conversion circuit. Compared with the method of using CODEC chip to realize the amplification and conversion of MIC signal, this application has lower cost, higher amplification factor, voltage adaptability and adjustability, and can match various input signals by setting bias voltage and operating voltage.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0016] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0017] Figure 1 This is a schematic diagram of the structure of the vehicle-mounted MIC conversion circuit shown in the embodiments of this application. Detailed Implementation

[0018] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While embodiments of this application are shown in the drawings, it should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0019] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. 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.

[0020] Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] In related technologies, existing automotive single-ended microphone input circuits typically amplify and convert microphone signals using dedicated CODEC chips. However, CODEC chips are expensive, leading to a higher overall price, and their output signal amplitude is limited, generally being relatively small. To address these issues, this application provides an automotive microphone conversion circuit that reduces costs and offers higher amplification, voltage adaptability, and adjustability.

[0022] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0023] See Figure 1The vehicle-mounted microphone (MIC) conversion circuit includes a MIC input amplifier circuit, a MIC signal conversion circuit, and a noise reduction circuit. The MIC input amplifier circuit receives the MIC signal; after receiving it, it amplifies the signal to form a first signal, which it then outputs. The MIC signal conversion circuit is connected to the MIC input amplifier circuit. It receives the first signal and processes it to obtain a second signal with an AC component opposite to the first signal. The noise reduction circuit is also connected to the MIC signal conversion circuit. It receives the second signal and is used to isolate the DC component and reduce noise in both the first and second signals.

[0024] This application amplifies the MIC signal through a MIC input amplifier circuit and performs differential conversion on the amplified MIC signal using a MIC signal conversion circuit. Compared with the method of using a CODEC chip to amplify and convert the MIC signal, this application has a lower cost and higher amplification factor, voltage adaptability and adjustability. It can match various input signals by setting the bias and operating voltage.

[0025] The MIC input amplifier circuit includes a MIC input terminal, an operational amplifier power supply VCC, capacitors C1 and C2, resistors R1, R2, R3, and R4, a bias voltage Vbia1, an operational amplifier U1, and a Zener diode D1. Capacitor C1 is connected to the MIC input terminal and one end of resistor R1. The operational amplifier power supply VCC is connected to the power supply terminal of operational amplifier U1. The non-inverting terminal of operational amplifier U1 is connected to the other end of resistor R1, resistor R2, and Zener diode D1. The other end of resistor R1 is connected to the bias voltage Vbia1. The inverting terminal of operational amplifier U1 is connected to one end of resistor R3 and resistor R4. Capacitor C2 is connected to the other end of resistor R3 and Zener diode D1. The other end of resistor R4 is connected to the output terminal of operational amplifier U1.

[0026] Capacitor C1 can be used as an isolation capacitor; specifically, it isolates the DC component in the MIC_IN+ signal. Resistor R1 serves as the equalization resistor for operational amplifier U1, optimizing its operating parameters. Resistor R2 is a bias resistor; the bias voltage Vbia1, used in conjunction with R2, adds a DC bias to the input MIC signal, ensuring the overall level of the input MIC signal is above 0V, thus guaranteeing proper recognition by operational amplifier U1. Operational amplifier U1, resistors R3 and R4, and capacitor C2 together form the non-inverting amplifier circuit of the operational amplifier. The amplification factor of the operational amplifier can be changed by adjusting the values ​​of resistors R3 and R4.

[0027] Zener diode D1 and resistor R1 work together to protect the input voltage of operational amplifier U1 from exceeding the voltage value of the operational amplifier power supply VCC. Under automotive conditions, the power supply may be shorted at the MIC input terminal. In this case, due to the bootstrap effect of capacitor C1, a voltage greater than the operational amplifier power supply VCC may be generated at the input of operational amplifier U1, causing damage to operational amplifier U1. Therefore, by using Zener diode D1 and resistor R1 to limit the input voltage of operational amplifier U1 from exceeding the voltage value of the operational amplifier power supply VCC, the damage to operational amplifier U1 due to shorting of the power supply at the MIC input terminal can be prevented.

[0028] In some embodiments, taking the MIC input amplifier circuit amplifying the MIC input terminal by a factor of 2 as an example, according to the virtual short and virtual open principle of the op-amp, the input current at the non-inverting terminal of op-amp U1 is almost zero, the input current at the inverting terminal of U1 is almost zero, the potentials at the non-inverting and inverting terminals of U1 are equal, and the output voltage Vo1 of op-amp U1 is (R3+R4) / R3×Vin1. The required amplification factor is 2 times, so (R3+R4) / R3=2, hence R3=R4. The equalizing resistor R1 = R3 / / R4, so R1 = 0.5 × R3. To minimize the attenuation of Vin1 relative to the MIC input, preferably, the resistance of R2 is greater than or equal to 20 times the resistance of R1. In this case, the attenuation at the MIC input is only 5%. At the same time, to ensure that the Zener diode D1 can operate normally, the resistance of resistor R1 is less than or equal to 4.7K ohms. Preferably, the resistance of resistor R1 is 2K ohms. Thus, R3 = R4 = 4K ohms, R2 = 40K ohms. At this time, Vin1 ≈ Vbia1 + Vmic-in+, Vo1 = 2 × (Vbia1 + Vmic-in+). Therefore, the output signal with an AC component of twice Vmic-in+ can be obtained.

[0029] The bias voltage Vbia1 should be greater than half the sum of the voltage at the MIC input terminal and the voltage of the op-amp power supply VCC. This ensures that the bias voltage Vbia1 can pull the voltage of the MIC_IN+ signal above 0V, facilitating the conversion of the first signal output from the MIC input amplifier circuit by the MIC signal conversion circuit. The maximum value of the first signal voltage should be less than or equal to the voltage of the op-amp power supply VCC to ensure that op-amp U1 can operate normally.

[0030] The MIC signal conversion circuit includes operational amplifier U2 and bias voltage Vbia2. The non-inverting terminal of operational amplifier U2 is connected to the bias voltage Vbia2. Utilizing the inverting amplification principle of operational amplifier U2, the positive terminal of operational amplifier U2 is not grounded, but connected to the bias voltage Vbia2, so that operational amplifier U2 outputs a second signal that is opposite to the AC component of the first signal.

[0031] The MIC signal conversion circuit also includes resistors R5, R6, and R7. The inverting terminal of operational amplifier U2 is connected to one end of resistor R5 and one end of resistor R6, respectively. The other end of resistor R5 is connected to the output terminal of the MIC input amplifier circuit. Resistor R7 is connected to the bias voltage Vbia2 and the non-inverting terminal of operational amplifier U2, respectively. The output terminal of operational amplifier U2 is connected to the other end of resistor R6. Resistors R5, R6, R7, and operational amplifier U2 form the inverting amplifier circuit of operational amplifier U2. The bias voltage Vbia2 is the input voltage of the non-inverting terminal of operational amplifier U2, and the bias voltage Vbia2 is used to control the output of operational amplifier Vo2.

[0032] In some embodiments, taking the MIC input amplifier circuit amplifying the MIC_IN+ signal by 2 times as an example, the MIC signal conversion circuit converts the amplified first signal to obtain a second signal with the opposite AC component to the amplified first signal. The specific implementation is as follows: From the basic principles of operational amplifiers, virtual open circuit and virtual short circuit, we know that Vin2=Vbia2, (Vo1-Vin2) / R5=(Vin2-Vo2) / R6, so we can obtain:

[0033] Vo2=Vbia2×(R5+R6) / R5-Vo1×R6 / R5,

[0034] Since the MIC input amplifier circuit calculates Vo1 = 2 × (Vbia1 + Vmin_in + ), we can obtain:

[0035] Vo2= Vbia2×(R5+R6) / R5-2×Vbia1×R6 / R5-2×Vmic-in+×R6 / R5

[0036] For Vo2 to output 2×(Vbia1-Vmic-in+), it must be able to form a corresponding differential signal with Vo1. Therefore, we can obtain:

[0037] 2Vbia1-2Vmic-in+=Vbia2(R5+R6) / R5-2Vbia1×R6 / R5-2Vmic-in+×R6 / R5

[0038] Therefore, we can obtain: R6=R5, Vbia2=2×Vbia1, and the balancing resistor R7=R5 / / R6, so the balancing resistor R7=0.5×R5. The resistance value of resistor R5 is less than 10K ohms. Preferably, the resistance value of resistor R5 is 5K. Therefore, R5=R6=5K and R7=2.5K.

[0039] The noise reduction circuit includes capacitors C5 and C6. Capacitor C5 is connected to both capacitor C6 and the output terminal of operational amplifier U2. The other end of capacitor C6 is grounded. Capacitor C5 can isolate the DC component and low-frequency noise in the second signal, while capacitor C6 can filter out high-frequency noise in the second signal.

[0040] The noise reduction circuit also includes capacitors C3 and C4. Capacitor C3 is connected to capacitor C4 and the output terminal of the MIC input amplifier circuit, respectively. The other end of capacitor C4 is used for grounding. Capacitor C3 can isolate the DC component and low-frequency noise in the first signal, and capacitor C4 can filter out the high-frequency noise in the first signal.

[0041] The solution of this application has been described in detail above with reference to the accompanying drawings. In the above embodiments, the descriptions of each embodiment have different focuses; for parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments. Those skilled in the art should also understand that the actions and modules involved in the specification are not necessarily essential to this application. Furthermore, it is understood that the steps in the method of this application embodiment can be adjusted, combined, and deleted according to actual needs, and the modules in the device of this application embodiment can be combined, divided, and deleted according to actual needs.

[0042] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An on-vehicle MIC conversion circuit characterized by comprising: It includes a MIC input amplifier circuit, a MIC signal conversion circuit, and a noise reduction circuit; the MIC input amplifier circuit is used to amplify the MIC signal and output the amplified first signal; the MIC signal conversion circuit is connected to the MIC input amplifier circuit, and the MIC signal conversion circuit is used to process the first signal and obtain a second signal with the opposite AC component to the first signal; the noise reduction circuit is connected to the MIC signal conversion circuit.

2. The vehicle-mounted MIC conversion circuit according to claim 1, characterized in that: The MIC input amplifier circuit includes a MIC input terminal, an operational amplifier power supply VCC, capacitors C1 and C2, resistors R1, R2, R3, and R4, a bias voltage Vbia1, an operational amplifier U1, and a Zener diode D1. Capacitor C1 is connected to the MIC input terminal and one end of resistor R1. The operational amplifier power supply VCC is connected to the power supply terminal of operational amplifier U1. The non-inverting terminal of operational amplifier U1 is connected to the other end of resistor R1, resistor R2, and Zener diode D1. The other end of resistor R2 is connected to the bias voltage Vbia1. The inverting terminal of operational amplifier U1 is connected to one end of resistor R3 and one end of resistor R4. Capacitor C2 is connected to the other end of resistor R3 and Zener diode D1. The other end of resistor R4 is connected to the output terminal of operational amplifier U1.

3. The vehicle-mounted MIC conversion circuit according to claim 2, characterized in that: The bias voltage Vbia1 should be greater than half the sum of the voltage at the MIC input terminal and the voltage at the op-amp power supply VCC.

4. The vehicle-mounted MIC conversion circuit according to claim 2, characterized in that: The maximum value of the voltage of the first signal is less than or equal to the voltage value of the operational amplifier power supply VCC.

5. The vehicle-mounted MIC conversion circuit according to claim 2, characterized in that: The resistance of the resistor R1 is less than or equal to 4.7 kΩ.

6. The vehicle-mounted MIC conversion circuit according to claim 1, characterized in that: The MIC signal conversion circuit includes an operational amplifier U2 and a bias voltage Vbia2, with the non-inverting terminal of the operational amplifier U2 connected to the bias voltage Vbia2.

7. The vehicle-mounted MIC conversion circuit according to claim 6, characterized in that: The MIC signal conversion circuit further includes resistors R5, R6, and R7. The inverting terminal of the operational amplifier U2 is connected to one end of resistor R5 and one end of resistor R6, respectively. The other end of resistor R5 is connected to the output terminal of the MIC input amplifier circuit. Resistor R7 is connected to the bias voltage Vbia2 and the non-inverting terminal of the operational amplifier U2, respectively. The output terminal of the operational amplifier U2 is connected to the other end of resistor R6.

8. The vehicle-mounted MIC conversion circuit according to claim 7, characterized in that: The noise reduction circuit includes capacitor C5 and capacitor C6. Capacitor C5 is connected to capacitor C6 and the output terminal of operational amplifier U2, respectively. The other end of capacitor C6 is used for grounding.

9. The vehicle-mounted MIC conversion circuit according to claim 7, characterized in that: The resistance value of resistor R5 is less than 10K ohms.

10. The vehicle-mounted MIC conversion circuit according to claim 1, characterized in that: The noise reduction circuit includes capacitor C3 and capacitor C4. Capacitor C3 is connected to capacitor C4 and the output terminal of the MIC input amplifier circuit, respectively. The other end of capacitor C4 is used for grounding.

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