Audio input conditioning circuit and electronic device

Abstract

The application relates to an audio input adjusting circuit and an electronic device. The audio input adjusting circuit comprises a signal access circuit, a first gain circuit, a volume adjusting circuit and a second gain circuit connected in sequence. The signal access circuit is used for outputting a preset attenuated audio signal. The first gain circuit is used for configuring an input impedance, improving the driving capability of a front-stage circuit, outputting the audio signal after first gain or second gain, and outputting the audio signal after third gain according to a volume adjusting signal. The second gain circuit is used for outputting the audio signal after limiting and / or attenuating the audio signal output by the volume adjusting circuit. Two sets of different first gain circuits and second gain circuits with different gains are arranged, the audio input dynamic range is improved, and the volume adjusting circuit is arranged between the first gain circuit and the second gain circuit, so that the gain adjusting range is improved.

Description

Technical Field

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

[0002] Currently, the main way to improve audio input dynamics in audio equipment on the market is by increasing the power supply to the operational amplifier (op-amp). However, this method is limited for battery-powered portable devices due to the limited power supply. Furthermore, the circuit selection for the subsequent stage of the op-amp in this method needs to meet the peak output of the op-amp, but the gain is generally adjusted by resistors and potentiometers. The gain adjustment range is small and non-linear, leading to saturation distortion and even damage to the subsequent circuitry. Utility Model Content

[0003] The purpose of this application is to provide an audio input adjustment circuit and an audio device, which aims to solve the problem of limited input dynamic range adjustment and gain adjustment of audio devices in related technologies.

[0004] In a first aspect, embodiments of this application provide an audio input adjustment circuit, including...

[0005] A signal input circuit is connected to an audio interface for receiving audio signals and outputting them after a first preset attenuation. The audio signal is a differential signal. A first gain circuit, connected to the signal access circuit, is used to configure the input impedance and output the audio signal after applying a first gain or a second gain to the audio signal output by the signal access circuit. A volume adjustment circuit, connected to the first gain circuit, is used to adjust the third gain of the audio signal output by the first gain circuit according to the volume adjustment signal. The second gain circuit, connected to the volume adjustment circuit, is used to limit and / or attenuate the audio signal output by the volume adjustment circuit before outputting it.

[0006] In one embodiment, the first gain circuit and the second gain circuit constitute at least one instrumentation amplifier.

[0007] In one embodiment, the signal access circuit includes: The first voltage divider circuit is connected to the audio interface and is used to receive the first audio differential signal, and to divide the first audio differential signal and output the first audio voltage divider signal. The second voltage divider circuit is connected to the audio interface and is used to receive the second audio differential signal, and to divide the second audio differential signal and output the second audio voltage divider signal. The first coupling capacitor is connected to the first voltage divider circuit and is used to couple the first audio voltage divider signal out. The second coupling capacitor is connected to the second voltage divider circuit and is used to couple the second audio voltage divider signal out. The first audio differential signal and the second audio differential signal constitute a pair of differential signals.

[0008] In one embodiment, the first gain circuit includes: The first operational amplifier circuit has its first input terminal connected to the first coupling capacitor, which is used to output the first audio voltage divider signal as a follower or to output a gain signal. The second operational amplifier circuit has its first input terminal connected to the second coupling capacitor, which is used to output the second audio voltage divider signal as a follower or as a gain output. A gain resistor and a switching switch are connected in series between the second input terminal of the first operational amplifier circuit and the second input terminal of the second operational amplifier circuit. When the switching switch is off, the first operational amplifier circuit and the second operational amplifier circuit are configured to operate at the first gain to follow the output. When the switching switch is on, it is used to configure the first operational amplifier circuit and the second operational amplifier circuit to operate at the second gain to gain the output.

[0009] In one embodiment, the volume adjustment circuit includes a volume regulator having a gain adjustment terminal and multiple gain channels. The gain adjustment terminal is connected to the volume adjustment signal to adjust the third gain of each of the gain channels. The first gain circuit and the second gain circuit are connected by one or more gain channels in series.

[0010] In one embodiment, the second gain circuit includes: The third operational amplifier circuit is connected to the volume adjustment circuit, and the third operational amplifier circuit is used to limit the output of the audio signal of the volume adjustment circuit. The fourth operational amplifier circuit is connected to the volume adjustment circuit, and the third operational amplifier circuit is used to output the audio signal output by the volume adjustment circuit after the second preset attenuation.

[0011] In one embodiment, the third operational amplifier circuit includes: A first differential amplifier receives the differential audio signal output from the volume adjustment circuit, and after limiting the differential audio signal based on the power supply voltage, outputs a first differential signal of the first audio signal, wherein the voltage value of the first differential signal is lower than the power supply voltage. The first inverter is connected to the output of the first differential amplifier and is used to invert the first differential signal of the first audio signal to output the second differential signal of the first audio signal.

[0012] In one embodiment, the fourth operational amplifier circuit includes: The second differential amplifier is connected to the differential audio signal output by the volume adjustment circuit, and after performing the second preset attenuation on the differential audio signal, it outputs the first differential signal of the second audio signal. The second inverter is connected to the output of the second differential amplifier and is used to invert the first differential signal of the second audio signal to output the second differential signal of the second audio signal.

[0013] In one embodiment, it further includes: A pull-up circuit, connected to the signal access circuit, the first gain circuit, and the pull-up power supply, is used to set a virtual ground for the audio signal output by the signal access circuit based on the pull-up power supply.

[0014] In one embodiment, it further includes: A control circuit, connected to the first gain circuit and the second gain circuit, is used to control the first gain circuit to operate at the first gain or the second gain based on the audio signal output by the second gain circuit.

[0015] In a first aspect, embodiments of this application provide an electronic device, including the audio input adjustment circuit as described above.

[0016] The beneficial effects of this application embodiment compared with related technologies are as follows: The audio input adjustment circuit provided in this application embodiment includes a signal access circuit, a first gain circuit, a volume adjustment circuit, and a second gain circuit connected in sequence. The signal access circuit is used to output the accessed audio signal after a first preset attenuation; the first gain circuit is used to configure the input impedance and output the audio signal output by the signal access circuit after applying a first gain or a second gain; the volume adjustment circuit is used to adjust the audio signal output by the first gain circuit according to the volume adjustment signal, after applying a third gain; the second gain circuit is used to output the audio signal output by the volume adjustment circuit after limiting the amplitude and after applying a second preset attenuation. The audio input adjustment circuit provided in this application embodiment first attenuates the accessed audio signal through the signal access circuit to reduce the input upper limit. The first gain circuit can configure the input impedance to improve the driving capability of the front-end circuit. Setting two sets of first gain circuits and second gain circuits with different gains improves the dynamic range of audio input. Furthermore, setting a volume adjustment circuit between the first gain circuit and the second gain circuit can improve the gain adjustment range. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of an audio input adjustment circuit provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of an audio input adjustment circuit provided in an embodiment of this application; Figure 3 A circuit diagram of an audio input adjustment circuit provided in an embodiment of this application; Figure 4 This is a schematic diagram of the control circuit in an audio input adjustment circuit provided in an embodiment of this application. Detailed Implementation

[0018] 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.

[0019] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0020] 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.

[0021] Please see Figure 1 One embodiment of this application provides an audio input adjustment circuit, including a signal access circuit 110, a first gain circuit 120, a volume adjustment circuit 130, and a second gain circuit 140 connected in sequence. The audio input adjustment circuit can be applied to electronic devices with audio input functionality. The signal input circuit 110 is connected to the audio interface 10 for inputting an audio signal and outputting it after a first preset attenuation. The audio signal is a differential signal. The first gain circuit 120 is connected to the signal input circuit 110 for configuring the input impedance and outputting the audio signal based on a first or second gain applied to it. The volume adjustment circuit 130 is connected to the first gain circuit 120 for adjusting the audio signal output by the first gain circuit 120 according to a volume adjustment signal, using a third gain adjustment. The second gain circuit 140 is connected to the volume adjustment circuit 130 for limiting and / or attenuating the audio signal output by the volume adjustment circuit 130 before outputting it.

[0022] The audio signal includes a pair of audio differential signals. Therefore, it can be understood that the signal access circuit 110, the first gain circuit 120, the volume adjustment circuit 130, and the second gain circuit 140 all include two signal transmission links, which are used to transmit and process the two differential signals of the audio signal, respectively.

[0023] The signal input circuit 110 first performs a first preset attenuation (which can also be understood as gain adjustment) on the input audio signal, lowering the upper limit of the input and increasing the adjustment range for subsequent gain adjustment of the audio signal, while also improving the dynamic range of the audio input. The first gain circuit 120 can be configured with input impedance, for example, configured with infinite input impedance, which can improve the driving capability of the signal input circuit 110 and further improve the dynamic range of the audio input. The second gain circuit 140 limits the audio signal and performs a second preset attenuation, which can also be understood as gain adjustment. That is, the signal input circuit 110, the first gain circuit 120, the volume adjustment circuit 130, and the second gain circuit 140 in the audio input adjustment circuit can all be used for gain adjustment, which can give the audio signal a wider dynamic input range and gain jump range.

[0024] In some embodiments, the first gain circuit 120 and the second gain circuit 140 constitute at least one instrumentation amplifier. It provides a high common-film rejection ratio and high input impedance. Additionally, it features low DC offset, low drift, low noise, and high open-loop gain.

[0025] Please see Figure 2 In some embodiments, the signal access circuit 110 includes a first voltage divider circuit 111, a second voltage divider circuit 112, a first coupling capacitor C11, and a second coupling capacitor C12.

[0026] The first voltage divider circuit 111 is connected to the audio interface 10, used to receive the first audio differential signal, and output the first audio divided voltage signal after dividing the first audio differential signal; the second voltage divider circuit 112 is connected to the audio interface 10, used to receive the second audio differential signal, and output the second audio divided voltage signal after dividing the second audio differential signal; the first coupling capacitor C11 is connected to the first voltage divider circuit 111, used to couple the first audio divided voltage signal to the output; the second coupling capacitor C12 is connected to the second voltage divider circuit 112, used to couple the second audio divided voltage signal to the output. The first audio differential signal and the second audio differential signal form a differential signal pair. It is understood that the voltage division ratio of the first voltage divider circuit 111 and the second voltage divider circuit 112 is the same. The first coupling capacitor C11 and the second coupling capacitor C12 are used to isolate the DC component of the audio voltage divider signal. It is understood that the first voltage divider circuit 111 and the second voltage divider circuit 112 divide the input audio signal and output the signal, i.e., the output after the first preset attenuation mentioned above.

[0027] Please see Figure 3 In some embodiments, the audio input adjustment circuit further includes coupling capacitor C13, coupling capacitor C14, first inductor L1 and second inductor L2, the first inductor L1 and the second inductor L2 forming a common-mode inductor for filtering out common-mode interference of the audio interface 10.

[0028] For example, the first voltage divider circuit 111 includes a first resistor R1 and a second resistor R2. The first resistor R1 is connected to the audio interface 10 through a coupling capacitor C13 and a first inductor L1, and is connected between the coupling capacitor C13 and the first coupling capacitor C11. The second resistor R2 is connected between the second resistor R1 and ground. The second voltage divider circuit 112 includes a third resistor R3 and a fourth resistor R4. The third resistor R3 is connected to the audio interface 10 through a coupling capacitor C14 and a second inductor L2, and is connected between the coupling capacitor C14 and the second coupling capacitor C12. The fourth resistor R4 is connected between the third resistor R3 and ground.

[0029] Please see Figure 2 In some embodiments, the first gain circuit 120 includes a first operational amplifier circuit 121, a second operational amplifier circuit 122, a gain resistor R0, and a switching switch K1.

[0030] The first input terminal of the first operational amplifier circuit 121 is connected to the first coupling capacitor C11. The first operational amplifier circuit 121 is used to output the first audio voltage divider signal as a follower or to output with gain. The first input terminal of the second operational amplifier circuit 122 is connected to the second coupling capacitor C12. The second operational amplifier circuit 122 is used to output the second audio voltage divider signal as a follower or to output with gain. The gain resistor R0 and the switching switch K1 are connected in series between the second input terminal of the first follower and the second input terminal of the second follower. When the switching switch K1 is off, the first operational amplifier circuit 121 and the second operational amplifier circuit 122 are configured to operate at the first gain to follow the output. When the switching switch K1 is on, the first operational amplifier circuit 121 and the second operational amplifier circuit 122 are configured to operate at the second gain to output with gain.

[0031] In this embodiment, the first input terminals of the first operational amplifier circuit 121 and the second operational amplifier circuit 122 are non-inverting input terminals, and the second input terminals are inverting input terminals. When the switch K1 is off, the first operational amplifier circuit 121 and the second operational amplifier circuit 122 function as voltage followers or input buffers, providing high input impedance. When the switch K1 is on, the first gain circuit 120 provides gain to the input audio voltage divider signal.

[0032] For example, the switch K1 is a relay or a semiconductor switch. When the amplitude of the audio signal is low, it first undergoes voltage division attenuation through the signal input circuit 110. When the switch K1 is turned on, the gains of the first operational amplifier circuit 121 and the second operational amplifier circuit 122 will cancel out the voltage division attenuation gains of the preceding first voltage divider circuit 111 and the second voltage divider circuit 112, respectively, so that the gain of the audio signal after passing through the signal input circuit 110 and the first gain circuit 120 is 0dB. It can be understood that in this example, the second gain and the first preset attenuation are reciprocals of each other. In other examples, the second gain can be greater than or less than the reciprocal of the first preset attenuation, and the specific value is set according to system requirements.

[0033] For example, please refer to Figure 3The first operational amplifier circuit 121 includes a first operational amplifier U1, a fifth resistor R5, a sixth resistor R6, and a first capacitor C1. The second operational amplifier circuit 122 includes a second operational amplifier U2, a seventh resistor R7, an eighth resistor R8, and a second capacitor C2. The non-inverting input of the first operational amplifier U1 is connected to a first voltage divider circuit 111, and the non-inverting input of the second operational amplifier U2 is connected to a second voltage divider circuit 112. A gain resistor R0 and a switching switch K1 are connected between the inverting inputs of the first and second operational amplifiers U1 and U2, respectively. The first capacitor C1 is connected between the inverting input and output of the first operational amplifier U1, and the second capacitor C2 is connected between the inverting input and output of the second operational amplifier U2. The fifth resistor R5 is connected in series with the output terminal of the first operational amplifier U1, the seventh resistor R7 is connected in series with the output terminal of the second operational amplifier U2, the sixth resistor R6 is connected between the fifth resistor R5 and the inverting input terminal of the first operational amplifier U1, and the eighth resistor R8 is connected between the seventh resistor R7 and the inverting input terminal of the second operational amplifier U2.

[0034] It is understandable that the first operational amplifier circuit 121 and the second operational amplifier circuit 122 serve as the first stage of the instrumentation amplifier. The sixth resistor R6 and the eighth resistor R8 have the same resistance value, for example, both are represented by R6. The second gain is 1 + 2R6 / R0. The first operational amplifier U1 and the second operational amplifier U2 are powered by a 10V positive voltage and a -5V negative voltage, respectively, thereby providing limiting for the output of the first operational amplifier circuit 121 and the second operational amplifier circuit 122.

[0035] Please see Figure 2 In some embodiments, the volume adjustment circuit 130 includes a volume adjuster 132, which has a gain adjustment terminal T and multiple gain channels. The gain adjustment terminal T is connected to a volume adjustment signal to adjust the third gain of each gain channel. The first gain circuit 120 and the second gain circuit 140 are connected by one or multiple gain channels in series.

[0036] For example, please refer to Figure 3 The volume regulator 132 includes multiple input terminals InN and output terminals OutN that are connected to each of the multiple input terminals, where N takes values ​​A, B, C, D, ... , and one input terminal and the connected output terminal form a gain channel. In this embodiment, two gain channels are connected between the first gain circuit 120 and the second gain circuit 140.

[0037] Specifically, the first operational amplifier circuit 121 is connected to the second gain circuit 140 through two gain channels. The two gain channels connected to the second operational amplifier circuit 122 include: channel A, consisting of input terminal InA, output terminal OutA, and input terminal; and channel B, consisting of input terminal InB, and output terminal OutB. Connecting output terminal OutA to input terminal InB results in channel A and channel B being connected in series. The second operational amplifier circuit 122 is also connected to the second gain circuit 140 through two gain channels. The two gain channels connected to the second operational amplifier circuit 122 include: channel C, consisting of input terminal InC, output terminal OutC, and input terminal; and channel D, consisting of input terminal InD, and output terminal OutD. Connecting output terminal OutC to input terminal InD results in channel C and channel D being connected in series.

[0038] Since the volume controller 132 only supports single-ended signal adjustment, the two sets of channels (input terminal InA-output terminal OutB and input terminal InC-output terminal OutD) are used to adjust the outputs of the first operational amplifier circuit 121 and the second operational amplifier circuit 122, respectively, to adjust differential signals. The electronic volume controller 132 allows for gain adjustment of -95dB to 31.5dB in 0.5dB steps. The use of multiple gain channels in series in each set of channels increases the gain adjustment range. This example uses two series-connected gain channels, which can increase the gain by up to 63dB.

[0039] For example, please refer to Figure 4 The user inputs audio volume commands to the control circuit 160 via software or a volume switch. The control circuit 160 converts the volume adjustment commands into volume adjustment signals Data and Clk, which are input to the gain adjustment terminal T of the volume regulator 132. The volume regulator 132 then applies a third gain to the audio signal passing through each gain channel.

[0040] Please see Figure 2 In some embodiments, the second gain circuit 140 includes a third operational amplifier circuit 141 and a fourth operational amplifier circuit 142. The third operational amplifier circuit 141 is connected to the volume adjustment circuit 130 and is used to limit the audio signal output by the volume adjustment circuit 130. The fourth operational amplifier circuit 142 is connected to the volume adjustment circuit 130 and is used to perform a second preset attenuation on the audio signal output by the volume adjustment circuit 130 before outputting it.

[0041] In this design, both the third operational amplifier circuit 141 and the fourth operational amplifier circuit 142 are connected to the differential signal pairs of the audio signal output from the audio adjustment circuit, providing two different gain output levels to the subsequent band circuit. It can be understood that both the third operational amplifier circuit 141 and the fourth operational amplifier circuit 142 can serve as the second stage of an instrumentation amplifier. The third operational amplifier circuit 141, together with the first operational amplifier circuit 121 and the second operational amplifier circuit 122, constitutes one instrumentation amplifier, and the fourth operational amplifier circuit 142, together with the first operational amplifier circuit 121 and the second operational amplifier circuit 122, can also constitute one instrumentation amplifier.

[0042] Please see Figure 3 In some embodiments, the third operational amplifier circuit 141 includes a first differential amplifier 1411 and a first inverter 1412.

[0043] The first differential amplifier 1411 receives the differential audio signal (i.e., the first audio voltage divider signal and the second audio voltage divider signal after gain) output from the volume adjustment circuit 130. After limiting the differential audio signal based on the supply voltage VCC, it outputs the first differential signal OUT1-N of the first audio signal. The voltage value of the first differential signal OUT1-N is lower than the supply voltage VCC. The first inverter 1412 is connected to the output terminal of the first differential amplifier 1411 and is used to invert the first differential signal OUT1-N of the first audio signal, outputting the second differential signal OUT1-P of the first audio signal.

[0044] The first differential amplifier 1411 processes the difference between the first audio voltage divider signal and the second audio voltage divider signal. In this embodiment, the gain of the first differential amplifier 1411 is set to 1, and its output is limited using the supply voltage VCC of the first differential amplifier 1411 to match the input range of the subsequent circuit (e.g., an analog-to-digital converter) to prevent damage to the subsequent circuit. For example, the first differential amplifier 1411 is powered by a single power supply, i.e., only a positive power supply (e.g., 5V). The first inverter 1412 is actually used to convert a single-ended signal to a differential signal.

[0045] For example, the first differential amplifier 1411 includes a third operational amplifier U3, resistors R9, R10, R11, R12, and R13, and capacitors C3, C4, and C5. The two input terminals of the third operational amplifier U3 are connected to the output terminals OutB and OutD of the volume regulator 132 via resistors R9 and R10, respectively. Capacitor C3 is connected between the inverting input terminal and the output terminal of the third operational amplifier U3. Resistor R11 is connected in series with the output terminal of the third operational amplifier U3. Resistor R12 is connected between the inverting input terminal of the third operational amplifier U3 and resistor R11. The connection point between resistors R12 and R11 serves as the output terminal of the first differential amplifier 1411. Resistor R13 is connected between the non-inverting input terminal of the third operational amplifier U3 and the output terminal of the first inverter 1412. Capacitor C4 is connected in parallel with resistor R13. Capacitor C5 is connected between the output terminal of the first differential amplifier 1411 and the output terminal of the first inverter 1412. Capacitor C5 is used for phase compensation or fine-tuning between the first differential signal OUT1-N and the second differential signal OUT1-P of the first audio signal, so that the two signals are out of phase.

[0046] For example, the first inverter 1412 includes a fourth operational amplifier U4, resistors R14, R15, and R16, and a capacitor C6. The inverting input of the fourth operational amplifier U4 is connected to the output of the first differential amplifier 1411 via resistor R14. Capacitor C6 is connected between the inverting input and output of the fourth operational amplifier U4. The non-inverting input of the fourth operational amplifier U4 is connected to virtual ground 1 / 2VCC. Resistor R15 is connected in series with the output of the fourth operational amplifier U4. Resistor R16 is connected between the inverting input of the fourth operational amplifier U4 and resistor R15. The connection point of resistors R15 and R16 serves as the output of the first inverter 1412. The fourth operational amplifier U4 shares the same power supply as the third operational amplifier U3. Resistors R12 and R15 are used to prevent short circuits.

[0047] For example, resistors R9, R10, R11, and R13 have the same resistance value, making the gain of the first differential amplifier 1411 1. Resistors R14 and R16 have the same resistance value, making the gain of the first inverter 1412 also 1, so that the amplitudes of the first differential signal OUT1-N and the second differential signal OUT1-P of the first audio signal are the same. A 1 / 2VCC voltage is virtually connected to ground, and the function of capacitor C4 and resistor R13 is equivalent to placing the voltage at the non-inverting input of the third operational amplifier U3 on virtual ground as a reference.

[0048] Please see Figure 3 In some embodiments, the fourth operational amplifier circuit 142 includes a second differential amplifier 1421 and a second inverter 1422.

[0049] The second differential amplifier 1421 is connected to the differential audio signal output by the volume adjustment circuit 130, and after performing a second preset attenuation on the differential audio signal, it outputs the first differential signal OUT2-N of the second audio signal; the second inverter 1422 is connected to the output terminal of the second differential amplifier 1421, and is used to invert the first differential signal OUT2-N of the second audio signal, and output the second differential signal OUT2-P of the second audio signal.

[0050] The second differential amplifier 1421 processes the difference between the first and second audio voltage divider signals. In this embodiment, the gain of the second differential amplifier 1421 is set to 1 / 8 to match the input range of the subsequent circuit (e.g., an analog-to-digital converter) to avoid damaging the subsequent circuit. Exemplarily, the second differential amplifier 1421 is also powered by a single power supply. The second inverter 1422 is actually used to convert a single-ended signal to a differential signal.

[0051] For example, the second differential amplifier 1421 includes a fifth operational amplifier U5, resistors R17, R18, R19, R20, and R21, and capacitors C7, C8, and C9. The two input terminals of the fifth operational amplifier U5 are connected to the output terminals OutB and OutD of the volume regulator 132 via resistors R17 and R18, respectively. Capacitor C7 is connected between the inverting input terminal and the output terminal of the fifth operational amplifier U5. Resistor R19 is connected in series with the output terminal of the fifth operational amplifier U5. Resistor R20 is connected between the inverting input terminal of the fifth operational amplifier U5 and resistor R19. The connection point of resistors R19 and R20 serves as the output terminal of the second differential amplifier 1421. Resistor R21 is connected between the non-inverting input terminal of the fifth operational amplifier U5 and the output terminal of the second inverter 1422. Capacitor C8 is connected in parallel with resistor R21. Capacitor C9 is connected between the output terminal of the second differential amplifier 1421 and the output terminal of the second inverter 1422. Capacitor C9 is used for phase compensation or fine-tuning between the first differential signal OUT2-N and the second differential signal OUT2-P of the second audio signal, so that the two signals are out of phase.

[0052] For example, the second inverter 1422 includes a sixth operational amplifier U6 and resistors R22, R23, R16, and capacitor C10. The inverting input of the sixth operational amplifier U6 is connected to the output of the second differential amplifier 1421 through resistor R22. Capacitor C10 is connected between the inverting input and output of the sixth operational amplifier U6. The non-inverting input of the sixth operational amplifier U6 is connected to virtual ground 1 / 2VCC. Resistor R23 is connected in series with the output of the sixth operational amplifier U6. Resistor R24 ​​is connected between the inverting input of the sixth operational amplifier U6 and resistor R23. The connection point of resistors R23 and R24 serves as the output of the second inverter 1422. The sixth operational amplifier U6 shares the same power supply as the fifth operational amplifier U5. Resistors R11, R15, R20, and R23 are used to prevent short circuits.

[0053] For example, resistors R17 and R18 have the same resistance value, as do resistors R20 and R21. Resistor R17 has a resistance eight times that of resistor R20, resulting in a gain of 1 / 8 for the second differential amplifier 1421. Resistors R22 and R24 have the same resistance value, resulting in a gain of 1 for the second inverter 1422, ensuring that the amplitudes of the first differential signal OUT2-N and the second differential signal OUT2-P of the second audio signal are identical. A virtual ground connection of 1 / 2 VCC is used, and capacitor C8 and resistor R21 effectively place the voltage at the non-inverting input of the fifth operational amplifier U5 on a virtual ground for reference.

[0054] The third operational amplifier circuit 141 and the fourth operational amplifier circuit 142 provide the subsequent circuit with two different gain outputs of the audio signal, which improves the saturation distortion caused by the narrow dynamic adjustment range of the audio input.

[0055] Please see Figure 2 In some embodiments, the audio input adjustment circuit further includes a pull-up circuit 150, which is connected to the signal access circuit 110, the first gain circuit 120, and the pull-up power supply. The pull-up circuit 150 is used to set a virtual ground based on the audio signal output by the signal access circuit 110 from the pull-up power supply. Exemplarily, this pull-up power supply is the 1 / 2 VCC voltage connected to the virtual ground. After the signal access circuit 110 outputs the audio voltage-divided signal through coupling capacitors C11 and C12, the pull-up circuit 150 boosts the circuit's stable operating point (or reference point) to 1 / 2 VCC before it enters the subsequent circuit, preventing the signal ground of the signal access circuit 110 from flowing back and affecting the subsequent circuit.

[0056] For example, the pull-up circuit 150 includes resistors R25, R26, R27, and R28. One end of resistor R25 is connected to the first coupling capacitor C11, and the other end of resistor R25 is connected to the first input terminal of the first operational amplifier circuit 121. The other end of resistor R25 is also connected to the pull-up power supply through resistor R26. One end of resistor R27 is connected to the second coupling capacitor C12, and the other end of resistor R27 is connected to the first input terminal of the second operational amplifier circuit 122. The other end of resistor R27 is also connected to the pull-up power supply through resistor R28.

[0057] Please see Figure 4 In some embodiments, the audio input adjustment circuit further includes a control circuit 160, which is connected to the first gain circuit 120 and the second gain circuit 140, and is used to control the first gain circuit 120 to operate at the first gain or the second gain according to the audio signal output by the second gain circuit 140.

[0058] In this embodiment, the control circuit 160 is the controller of the electronic device. It is connected to the two outputs of the second gain circuit 140 via an ADC interface or a mode converter, and receives the first audio signal OUT1 and the second audio signal OUT2. When the first audio signal OUT1 and the second audio signal OUT2 are too low, the control circuit 160 controls the switch K1 to close. When the first audio signal OUT1 and the second audio signal OUT2 are too high, the switch K1 is controlled to open. This can improve the dynamic adjustment to more than 140dB.

[0059] The above-described 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 input adjustment circuit, characterized in that, include: A signal input circuit is connected to an audio interface for receiving audio signals and outputting them after a first preset attenuation. The audio signal is a differential signal. A first gain circuit, connected to the signal access circuit, is used to configure the input impedance and output the audio signal after applying a first gain or a second gain to the audio signal output by the signal access circuit. A volume adjustment circuit, connected to the first gain circuit, is used to adjust the third gain of the audio signal output by the first gain circuit according to the volume adjustment signal. The second gain circuit, connected to the volume adjustment circuit, is used to limit and / or attenuate the audio signal output by the volume adjustment circuit before outputting it.

2. The audio input adjustment circuit as described in claim 1, characterized in that, The first gain circuit and the second gain circuit constitute at least one instrumentation amplifier.

3. The audio input adjustment circuit as described in claim 2, characterized in that, The signal access circuit includes: The first voltage divider circuit is connected to the audio interface and is used to receive the first audio differential signal, and to divide the first audio differential signal and output the first audio voltage divider signal. The second voltage divider circuit is connected to the audio interface and is used to receive the second audio differential signal, and to divide the second audio differential signal and output the second audio voltage divider signal. The first coupling capacitor is connected to the first voltage divider circuit and is used to couple the first audio voltage divider signal out. The second coupling capacitor is connected to the second voltage divider circuit and is used to couple the second audio voltage divider signal out. The first audio differential signal and the second audio differential signal constitute a pair of differential signals.

4. The audio input adjustment circuit as described in claim 3, characterized in that, The first gain circuit includes: The first operational amplifier circuit has its first input terminal connected to the first coupling capacitor, which is used to output the first audio voltage divider signal as a follower or to output a gain signal. The second operational amplifier circuit has its first input terminal connected to the second coupling capacitor, which is used to output the second audio voltage divider signal as a follower or as a gain output. A gain resistor and a switching switch are connected in series between the second input terminal of the first operational amplifier circuit and the second input terminal of the second operational amplifier circuit. When the switching switch is off, the first operational amplifier circuit and the second operational amplifier circuit are configured to operate at the first gain to follow the output. When the switching switch is on, it is used to configure the first operational amplifier circuit and the second operational amplifier circuit to operate at the second gain to gain the output.

5. The audio input adjustment circuit as described in any one of claims 1 to 4, characterized in that, The volume adjustment circuit includes a volume regulator, which has a gain adjustment terminal and multiple gain channels. The gain adjustment terminal is connected to the volume adjustment signal to adjust the third gain of each of the gain channels. The first gain circuit and the second gain circuit are connected by one or more gain channels in series.

6. The audio input adjustment circuit as described in any one of claims 1 to 4, characterized in that, The second gain circuit includes: The third operational amplifier circuit is connected to the volume adjustment circuit, and the third operational amplifier circuit is used to limit the output of the audio signal of the volume adjustment circuit. The fourth operational amplifier circuit is connected to the volume adjustment circuit, and the third operational amplifier circuit is used to output the audio signal output by the volume adjustment circuit after the second preset attenuation.

7. The audio input adjustment circuit as described in claim 6, characterized in that, The third operational amplifier circuit includes: A first differential amplifier receives the differential audio signal output from the volume adjustment circuit, and after limiting the differential audio signal based on the power supply voltage, outputs a first differential signal of the first audio signal, wherein the voltage value of the first differential signal is lower than the power supply voltage. The first inverter is connected to the output of the first differential amplifier and is used to invert the first differential signal of the first audio signal to output the second differential signal of the first audio signal.

8. The audio input adjustment circuit as described in claim 6, characterized in that, The fourth operational amplifier circuit includes: The second differential amplifier is connected to the differential audio signal output by the volume adjustment circuit, and after performing the second preset attenuation on the differential audio signal, it outputs the first differential signal of the second audio signal. The second inverter is connected to the output of the second differential amplifier and is used to invert the first differential signal of the second audio signal to output the second differential signal of the second audio signal.

9. The audio input adjustment circuit as described in claim 1 or 2, characterized in that, Also includes: A pull-up circuit, connected to the signal access circuit, the first gain circuit, and the pull-up power supply, is used to set a virtual ground for the audio signal output by the signal access circuit based on the pull-up power supply.

10. The audio input adjustment circuit as described in any one of claims 1 to 4, characterized in that, Also includes: A control circuit, connected to the first gain circuit and the second gain circuit, is used to control the first gain circuit to operate at the first gain or the second gain based on the audio signal output by the second gain circuit.

11. An electronic device, characterized in that, Includes the audio input adjustment circuit as described in any one of claims 1 to 10.

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