Microphone circuit

Abstract

The invention provides a microphone circuit, which comprises a charge pump module connected with a first end of a microphone and used for receiving a preset first voltage, generating a first bias voltage according to the first voltage and outputting the first bias voltage to the microphone; the amplification module is connected with the second end of the microphone and used for receiving a voltage signal output by the microphone and amplifying the voltage signal to serve as an output signal of the microphone circuit to be output; and the voltage dividing module is connected with the second end of the microphone and the amplification module, and is used for receiving the first voltage, dividing the first voltage to generate a second bias voltage, outputting the second bias voltage to the microphone, and outputting the second bias voltage as the bias voltage of the amplification module to the amplification module. According to the microphone circuit, the first bias voltage and the second bias voltage change along with the first voltage, that is, the other bias voltage changes along with adjustment of any bias voltage, and the problem that the sensitivity of the MEMS microphone is shifted due to the fact that the difference between the two bias voltages changes due to adjustment of any bias voltage is solved.

Description

[Technical field]

[0001] The present invention relates to the field of circuit technology, and in particular to a microphone circuit. [Background technology]

[0002] The MEMS microphone circuit mainly includes a MEMS microphone (Microelectro Mechanical Systems) and an ASIC (Application-Specific Integrated Circuit) module. The two are electrically connected to convert sound signals into electrical signals to realize the function of the microphone. Specifically, the ASIC module provides a high-voltage high bias voltage and a low-voltage low bias voltage to the MEMS microphone to drive the MEMS microphone to convert sound signals into electrical signals.

[0003] The sensitivity of a MEMS microphone is proportional to the difference between a high bias voltage and a low bias voltage. In the related art, the high bias voltage and the low bias voltage of a MEMS microphone are independent of each other. Adjusting any bias voltage will cause the difference between the high bias voltage and the low bias voltage to change, thereby affecting the sensitivity of the MEMS microphone. The desire to adjust the high bias voltage and the low bias voltage separately to maintain the difference between the high bias voltage and the low bias voltage will increase the complexity of the circuit design. However, when a MEMS microphone operates in a wide power supply voltage range, because the power supply voltage will change, in order to maintain the AOP (Acoustic Overload Point) of the microphone circuit, it is necessary to adjust the output voltage of the MEMS microphone circuit by changing the low bias voltage, so that the output voltage of the MEMS microphone circuit is maintained at half of the power supply voltage of the MEMS microphone, so that the entire MEMS microphone circuit has a better AOP, because the AOP of the MEMS microphone circuit is the largest when its output voltage is half of the power supply voltage. However, changing the low bias voltage will also change the difference between the high bias voltage and the low bias voltage, thereby causing the sensitivity of the MEMS microphone to shift.

[0004] Therefore, it is necessary to provide a new microphone circuit to solve the above technical problems. [Summary of the invention]

[0005] The object of the present invention is to provide a microphone circuit to solve the above technical problem.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a microphone circuit, comprising:

[0008] A charge pump module, connected to a first end of an external microphone, for receiving a preset first voltage, generating a first bias voltage required for the microphone to work according to the first voltage and outputting the first bias voltage to the microphone;

[0009] an amplification module, connected to the second end of the microphone, and configured to receive a voltage signal output by the microphone, and amplify the voltage signal and output it as an output signal of the microphone circuit;

[0010] A voltage divider module is connected to the second end of the microphone and the amplifying module, and is used for receiving the first voltage, dividing the first voltage to generate a second bias voltage required for the microphone to work and outputting it to the microphone, and outputting the second bias voltage to the amplifying module as a bias voltage of the amplifying module.

[0011] In some embodiments, the charge pump module includes at least one stage of charge pumps connected in cascade, the output end of each stage of charge pumps is connected to the input end of the next stage of charge pumps, the input end of the first stage of charge pumps is grounded, and the output end of the last stage of charge pumps is connected to the first end of the microphone;

[0012] The reference voltage of the first-stage charge pump is the first voltage, and the reference voltages of the charge pumps of each stage after the first-stage charge pump are all preset charge pump reference voltages.

[0013] In some embodiments, a ratio of a second bias voltage output by the voltage divider module to a first voltage received by the voltage divider module is equal to a ratio of an output voltage of the first-stage charge pump to a first voltage received by the first-stage charge pump.

[0014] In some embodiments, each stage of the charge pump includes an enable terminal, and the enable terminal of each charge pump is respectively used to receive a corresponding enable signal, and each enable signal is respectively used to control the corresponding charge pump.

[0015] When the enable signal is at a first level, the charge pump adjusts the input voltage it receives according to the reference voltage it receives, and outputs the adjusted input voltage as the output voltage; when the enable signal is at a second level, the charge pump outputs the input voltage as the output voltage.

[0016] In some embodiments, the amplification module includes at least one stage of coupled amplifiers, the output end of each stage of the amplifier is connected to the input end of the next stage of the amplifier, and the input end of the first stage of the amplifier is respectively connected to the second end of the microphone and the voltage divider module, and the output end of the final stage of the amplifier is used to output the output signal of the microphone circuit.

[0017] In some embodiments, the microphone circuit further comprises:

[0018] The low voltage difference linear regulator module is used to connect to a power supply, perform voltage stabilization processing on the power supply voltage to obtain the first voltage, and output the first voltage to the charge pump module and the voltage divider module.

[0019] In some embodiments, the low dropout linear regulator module includes:

[0020] A linear voltage stabilizing unit, used for connecting to the power supply, stabilizing the power supply voltage and outputting the first voltage;

[0021] a feedback unit, configured to receive the first voltage and perform voltage division processing on the first voltage to generate a feedback voltage;

[0022] The linear voltage stabilization unit is further configured to receive the feedback voltage and a preset first reference voltage, and linearly regulate the first voltage according to the feedback voltage and the first reference voltage.

[0023] In some embodiments, the low dropout linear regulator module further includes:

[0024] The voltage division and filtering unit is used to connect to a power supply, divide and filter the power supply voltage, and output the first reference voltage.

[0025] In some embodiments, the microphone is a MEMS microphone.

[0026] The beneficial effect of the present invention is that: the microphone circuit provided by the present invention inputs the first voltage into the charge pump module and the voltage divider module respectively to obtain the first bias voltage and the second bias voltage, so that the first bias voltage output by the charge pump module and the second bias voltage output by the voltage divider module will change with the first voltage, thereby realizing that the first bias voltage and the second bias voltage change synchronously with the change of the first voltage, and then the difference between the first bias voltage and the second bias voltage can always remain unchanged. The microphone circuit provided by the present invention can adjust the first bias voltage and the second bias voltage at the same time by adjusting the first voltage, that is, when adjusting any bias voltage, the other bias voltage will change accordingly, solving the technical problem that the difference between the first bias voltage and the second bias voltage is easily changed due to the adjustment of any bias voltage, which causes the sensitivity of the MEMS microphone to shift. In this way, when the power supply voltage of the microphone circuit changes, the second bias voltage can be adjusted by changing the first voltage, and then the voltage of the output signal of the amplification module can be adjusted to about half of the power supply voltage by adjusting the second bias voltage, thereby ensuring that the entire microphone circuit always has a larger acoustic overload point when the power supply voltage changes, and because the first bias voltage will also change with the second bias voltage, the microphone circuit can always keep the difference between the first bias voltage and the second bias voltage unchanged, so that the sensitivity of the microphone will not shift due to adjusting the acoustic overload point.

Brief Description of the Drawings

[0027] Figure 1 A schematic diagram of a microphone circuit provided by an embodiment of the present invention;

[0028] Figure 2 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention;

[0029] Figure 3 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention is shown;

[0030] Figure 4 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention is shown;

[0031] Figure 5 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention is shown;

[0032] Figure 6 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention is shown. [Specific implementation method]

[0033] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0034] It should be noted that in the embodiments of the present invention, "connection" can be understood as electrical connection, and the connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be either a direct connection between A and B or an indirect connection between A and B through one or more other electrical components.

[0035] An embodiment of the present invention provides a microphone circuit. Figure 1 A schematic diagram of a microphone circuit provided by an embodiment of the present invention, such as Figure 1 As shown, the microphone circuit provided by the embodiment of the present invention includes a charge pump module, a voltage divider module and an amplification module.

[0036] The charge pump module is connected to the first end of the external microphone, and is used to receive a preset first voltage, and generate a first bias voltage required for the microphone to work according to the first voltage and output it to the microphone. Optionally, the charge pump module is used to boost the first voltage to obtain a high-voltage first bias voltage, and the output end of the charge pump is connected to the first end of the microphone to output the first bias voltage to the first end of the microphone, and the charge pump module receives the first voltage to obtain the first bias voltage according to the first voltage.

[0037] The voltage divider module is connected to the second end of the microphone and the amplifying module, and is used to receive the first voltage, divide the first voltage to generate a second bias voltage required for the microphone to work and output it to the microphone, and output the second bias voltage to the amplifying module as the bias voltage of the amplifying module. Optionally, the output end of the voltage divider module is respectively connected to the second end of the microphone and the input end of the amplifying module to output a low-voltage second bias voltage thereto, and the input end of the voltage divider module receives the first voltage to divide the first voltage to obtain the second bias voltage.

[0038] The amplifier module is connected to the second end of the microphone, and is used to receive the voltage signal output by the microphone, and amplify the voltage signal and output it as the output signal of the microphone circuit. Optionally, the input end of the amplifier module is connected to the second end of the microphone to receive the voltage signal output by the microphone, and the input end of the amplifier module is also connected to the output end of the voltage divider module, so as to receive the bias voltage output by the voltage divider module, and the bias voltage is the input DC voltage of the amplifier module. The output end of the amplifier module amplifies and outputs the voltage signal output by the microphone. For the microphone circuit, when the voltage of the output signal of the amplifier module reaches half of the power supply voltage of the microphone circuit, the entire microphone circuit has a maximum AOP (Acoustic Overload Point). In view of this, the present invention uses the second bias voltage as the bias voltage of the amplifier module, so that when the power supply voltage of the microphone circuit changes, the second bias voltage can be changed by adjusting the first voltage, and then the voltage of the output signal of the amplifier module is adjusted so that it can always maintain about half of the power supply voltage of the microphone circuit.

[0039] In some preferred embodiments, in the microphone circuit provided by the present invention, the external microphone is a MEMS microphone.

[0040] As an implementation mode, in the microphone circuit provided by the embodiment of the present invention, the charge pump module receives the first voltage through the signal input port, and the first bias voltage output by the charge pump module is: VH=Vref×K+V1, and the second bias voltage output by the voltage divider module is: VL=V1×H. The difference between the first bias voltage and the second bias voltage is: VH-VL=Vref×K+V1-V1×H. Among them, VH represents the first bias voltage, Vref represents the reference voltage of the charge pump module, K represents the efficiency factor of the charge pump module, V1 represents the first voltage, VL represents the second bias voltage, and H represents the voltage divider coefficient of the voltage divider module. It can be seen from this that the microphone circuit provided in an embodiment of the present invention can control the difference between the first bias voltage and the second bias voltage to follow the change amplitude of the first voltage by adjusting the value of the voltage divider coefficient H, and when the voltage divider coefficient of the voltage divider module is 1, the difference between the first bias voltage and the second bias voltage will always remain unchanged, thereby achieving in the microphone circuit that the sensitivity of the MEMS microphone does not shift following the bias voltage. When the power supply voltage of the microphone circuit changes, the microphone circuit controls the output voltage of the amplification module to change synchronously by adjusting the second bias voltage. At this time, the sensitivity of the MEMS microphone will not shift following the change of the power supply voltage.

[0041] As another implementation, in the microphone circuit provided by the embodiment of the present invention, the charge pump module receives the first voltage through the reference voltage input port, and the signal input port of the charge pump module receives the input voltage provided by the external circuit. At this time, the first bias voltage output by the charge pump module is VH=V1×K+V0, and the second bias voltage output by the voltage divider module is: VL=V1×H. The difference between the first bias voltage and the second bias voltage is: VH-VL=V1×K+V0-V1×H. Wherein, VH represents the first bias voltage, V1 represents the first voltage, i.e., the reference voltage of the charge pump module, K represents the efficiency factor of the charge pump module, V0 represents the input voltage provided by the external circuit, VL represents the second bias voltage, and H represents the voltage division coefficient of the voltage division module. It can be seen that in this embodiment, the difference between the first bias voltage and the second bias voltage follows the change amplitude of the first voltage, which is determined by the difference between the efficiency factor K of the charge pump module and the voltage division coefficient H of the voltage division module, and when the difference between the efficiency factor K of the charge pump module and the voltage division coefficient H of the voltage division module is zero, the difference between the first bias voltage and the second bias voltage will always remain unchanged, thereby realizing that the sensitivity of the MEMS microphone does not shift with the bias voltage in the microphone circuit, and when the power supply voltage of the microphone circuit changes, the microphone circuit controls the output voltage of the amplification module to change synchronously by adjusting the second bias voltage, and at this time, the sensitivity of the MEMS microphone will not shift with the change of the power supply voltage. Optionally, the embodiment of the present invention does not limit the type and structure of the external circuit, as long as the external circuit can be applied to the microphone circuit.

[0042] As an implementation method, when the microphone operates in a wider power supply voltage range, such as when the power supply voltage range of the microphone is 0.9V to 3.6V, when the power supply voltage changes, the embodiment of the present invention can change the value of the second bias voltage by adjusting the first voltage, because the second bias voltage is also the input DC voltage of the amplifier module, so the change of the second bias voltage will also adjust the voltage of the output signal of the amplifier module, so that it can always be maintained at half of the power supply voltage of the microphone circuit, thereby ensuring that the entire microphone circuit always has a larger acoustic overload point. And because the first bias voltage will also change with the second bias voltage, the microphone circuit can always keep the difference between the first bias voltage and the second bias voltage unchanged, so that the sensitivity of the microphone will not be offset due to the adjustment of the acoustic overload point.

[0043] It is understandable that, in the embodiment of the present invention, the charge pump module, the voltage divider module and the amplifier module are electrically connected to the external MEMS microphone. In addition, the embodiment of the present invention does not limit the source of the first voltage. For example, the first voltage can be set as the power supply voltage of the MEMS microphone circuit, so that when the MEMS microphone works in a wider power supply range, when the power supply voltage changes, the first bias voltage and the second bias voltage will also change with the power supply voltage, and will not have a significant impact on the sensitivity of the MEMS microphone. For example, the first voltage can also be set to be provided by a voltage stabilizing circuit, so as to provide the MEMS microphone circuit with a first bias voltage and a second bias voltage with a good power supply rejection ratio (Power Supply Rejection Ratio). For example, the first voltage can also be set to be provided by a voltage stabilizing circuit, and the voltage stabilizing circuit is used to stabilize the power supply voltage to obtain the first voltage. The above examples are only used to illustrate that the embodiment of the present invention does not limit the source of the first voltage, and does not mean that the first voltage can only be obtained through the above three examples.

[0044] It is understandable that in the embodiments of the present invention, no corresponding restrictions are set for the specific structure of the voltage divider module, because the voltage divider module is a relatively mature part in the prior art field, and the focus and goal of the embodiments of the present invention are not to innovate or explore the specific structures of these two units. For example, a basic voltage divider module can be configured to include a voltage divider or a voltage divider circuit composed of a resistor element.

[0045] The microphone circuit provided in the embodiment of the present invention can simultaneously adjust the first bias voltage and the second bias voltage by adjusting the first voltage, that is, when any bias voltage is adjusted, the other bias voltage will change accordingly, thereby solving the technical problem that the difference between the first bias voltage and the second bias voltage is easily changed due to the change of the adjustment of any bias voltage, which may cause the sensitivity of the MEMS microphone to shift.

[0046] The microphone circuit provided by the present invention is applied to a microphone circuit with adjustable power supply voltage. In this way, when the power supply voltage of the microphone circuit changes, the second bias voltage can be adjusted by changing the first voltage, and then the voltage of the output signal of the amplification module can be adjusted to about half of the power supply voltage by adjusting the second bias voltage. Because the first bias voltage will also change with the second bias voltage, the microphone circuit of the present invention can ensure that the microphone circuit always maintains a good AOP and ensure that the sensitivity of the microphone will not shift when the power supply voltage changes.

[0047] In some preferred embodiments, Figure 2 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention is as follows: Figure 2 As shown, the charge pump module includes at least one stage of cascade-connected charge pumps, namely, charge pumps 1 to charge pumps i, i≥1, the output end of each stage of charge pumps is connected to the input end of the next stage of charge pumps, and the input end of the first stage of charge pumps, namely, charge pump 1, is grounded GND, and the output end of the last stage of charge pumps, namely, charge pump i, is connected to the first end of the microphone. Among them, the reference voltage of the first stage of charge pumps is the first voltage, and the reference voltages of the charge pumps of each stage after the first stage of charge pumps are all preset charge pump reference voltages. Optionally, as Figure 2 In the microphone circuit shown in FIG. 1 , the first bias voltage output by the charge pump module is: VH = V1 × K1 + V ref ×K2+V ref ×K3+…+V ref ×K N , the second bias voltage output by the voltage divider module is: VL = V1 × H. The difference between the first bias voltage and the second bias voltage is: VH-VL = V1 × K1-V1 × H + V ref ×K2+V ref ×K3+…+V ref ×K N Wherein, VH represents the first bias voltage, V1 represents the first voltage, i.e. the reference voltage of the first-stage charge pump, V ref Represents the preset charge pump reference voltage. For each level of charge pump after the first level, the preset charge pump reference voltage is fixed and provided by an external circuit such as a linear voltage regulator circuit. K i represents the efficiency factor of the i-th stage charge pump, 1≤i≤N, and N is the cascade number of charge pump modules, VL represents the second bias voltage, and H represents the voltage division coefficient of the voltage division module. It can be seen that the microphone circuit of the embodiment of the present invention can determine the variation amplitude of the difference between the first bias voltage and the second bias voltage following the first voltage through the difference between the efficiency factor K1 of the first stage charge pump and the voltage division coefficient H of the voltage division module.

[0048] In some embodiments, in the microphone circuit provided by the embodiment of the present invention, the ratio of the second bias voltage output by the voltage divider module to the first voltage received by the voltage divider module is equal to the ratio of the output voltage of the first-stage charge pump to the first voltage received by the first-stage charge pump. Optionally, the ratio of the second bias voltage output by the voltage divider module to the first voltage received by the voltage divider module is the voltage divider coefficient H of the voltage divider module, the signal input terminal of the first-stage charge pump is grounded, and the first voltage is input to the first-stage charge pump as a reference voltage, that is, the first-stage charge pump has no input voltage, and its output voltage is V1×K1, the ratio of the output voltage of the first-stage charge pump to the first voltage received by the first-stage charge pump is K1, and the difference between the first bias voltage and the second bias voltage is: VH-VL=V1×K1-V1×H+V ref ×K2+V ref ×K3+…+V ref ×K N , when H=K1, VH-VL=V ref ×K2+V ref ×K3+…+V ref ×K N , that is, at this time, the difference between the first bias voltage and the second bias voltage is a fixed value and will not change due to the change of the first voltage.

[0049] The microphone circuit provided by the embodiment of the present invention uses the first voltage as the reference voltage input of the first-stage charge pump, so that the difference between the first bias voltage and the second bias voltage will be determined by the difference between the efficiency factor K1 of the first-stage charge pump and the voltage division coefficient H of the voltage division module, and when the efficiency factor K1 of the first-stage charge pump is equal to the voltage division coefficient H of the voltage division module, the difference between the first bias voltage and the second bias voltage will not change with the first voltage, thereby achieving the goal that the sensitivity of the MEMS microphone does not shift with the bias voltage, and solving the problem that the difference between the first bias voltage and the second bias voltage is easily caused by a large change in the adjustment of any bias voltage, which may lead to a sensitivity shift of the MEMS microphone.

[0050] In some embodiments, in the microphone circuit provided by the embodiment of the present invention, each stage of the charge pump includes an enable terminal, and the enable terminal of each charge pump is used to receive a corresponding enable signal, and each enable signal is used to control the corresponding charge pump. When the enable signal is at a first level, the charge pump adjusts the input voltage it receives according to the reference voltage it receives, and outputs the adjusted input voltage as the output voltage. At this time, the output voltage of the charge pump is V out =V in +V ref ×K. When the enable signal is at the second level, the charge pump outputs the input voltage as the output voltage. At this time, the output voltage of the charge pump is V out =V inOptionally, the first level is one of a high level and a low level, and the second level is the other of a high level and a low level.

[0051] It is understandable that the embodiment of the present invention does not limit the source of the enable signal. For example, the enable signal can be generated by an existing level generating circuit.

[0052] In some embodiments, Figure 3 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention is shown. Figure 3 As shown, the amplification module includes at least one stage of coupled amplifiers, namely, coupled amplifiers 1 to j, j≥1, the output end of each stage of the amplifier is connected to the input end of the next stage of the amplifier, and the input end of the first stage amplifier, namely, amplifier 1, is respectively connected to the second end of the microphone and the voltage divider module, and the output end of the final stage amplifier, namely, amplifier j, is used to output the output signal of the microphone circuit. The microphone circuit provided by the embodiment of the present invention can significantly improve the circuit gain and stabilize the signal processing process through multi-stage amplification, and can also be flexibly configured to adapt to different scenarios, optimize the overall performance of the circuit, and enable the output signal to better meet subsequent needs.

[0053] As an implementation manner, in the microphone circuit provided by the embodiment of the present invention, the amplification module includes a two-stage coupled amplifier, so as to perform two-stage amplification and output on the voltage signal output by the microphone.

[0054] In some embodiments, Figure 4 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention is shown. Figure 4 As shown, the microphone circuit of the present invention also includes a low voltage difference linear regulator module, the input end of the low voltage difference linear regulator module is used to connect the power supply VDD, and the output end is respectively connected to the input end of the charge pump module and the input end of the voltage divider module, so that the power supply voltage is stabilized by linear regulation means to obtain a first voltage, and the first voltage is output to the charge pump module and the voltage divider module.

[0055] In the microphone circuit provided by an embodiment of the present invention, the first voltage is obtained by processing the power supply voltage by a low voltage difference linear regulator module. In this way, when the microphone circuit operates in a wide power supply voltage range, the first voltage will also change with the power supply voltage, and then the AOP of the microphone circuit will change synchronously with the power supply voltage change, and at this time, the sensitivity of the microphone circuit will not be offset.

[0056] In some embodiments, Figure 5 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention is shown. Figure 5 As shown, the low voltage dropout linear regulator module includes a linear voltage regulation unit and a feedback unit.

[0057] The input end of the linear voltage stabilizing unit is used to connect to the power supply VDD, and the output end is respectively connected to the charge pump module and the voltage divider module, so as to stabilize the power supply voltage and output the first voltage to the charge pump module and the voltage divider module. The feedback unit is connected to the linear voltage stabilizing unit, and is used to receive the first voltage to divide the first voltage to generate a feedback voltage. Furthermore, the linear voltage stabilizing unit is also used to receive the feedback voltage and a preset first reference voltage, and linearly adjust the first voltage according to the feedback voltage and the first reference voltage, so that the first voltage can be adjusted in time after the power supply voltage changes. Optionally, in the microphone circuit provided in an embodiment of the present invention, the first voltage can be adjusted by adjusting the value of the first reference voltage and / or the voltage divider coefficient of the feedback unit.

[0058] It should be noted that, in the embodiments of the present invention, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / ", unless otherwise specified, generally indicates that the associated objects before and after are in an "or" relationship.

[0059] It is understandable that in the embodiments of the present invention, no corresponding restrictions are set for the specific structures of the linear voltage stabilizing unit and the feedback unit. This is because the linear voltage stabilizing unit and the feedback unit are both relatively mature parts in the prior art, and the focus and goal of the embodiments of the present invention are not to innovate or explore the specific structures of these two units. For example, a basic linear voltage stabilizing unit can be configured to include an operational amplifier and a transistor, the non-inverting input terminal and the inverting input terminal of the operational amplifier are used to receive the feedback voltage and the first reference voltage respectively, the output terminal of the operational amplifier is connected to the gate of the transistor, the source of the transistor is connected to the power supply, and the drain of the transistor outputs the first voltage. A basic feedback unit can be configured as a voltage divider circuit / voltage divider, so as to divide the first voltage, and output the divided result as the feedback voltage to the operational amplifier. The above is only a structure of the linear voltage stabilizing unit and the feedback unit, and does not mean that the embodiments of the present invention can only realize the functions of the linear voltage stabilizing unit and the feedback unit through this structure.

[0060] In some embodiments, Figure 6 Another schematic diagram of a microphone circuit provided by an embodiment of the present invention is shown. Figure 6As shown, the low-voltage difference linear regulator module also includes a voltage divider filter unit, the input end of the voltage divider filter unit is used to connect the power supply VDD, and the output end is connected to the linear voltage regulator unit, so as to divide and filter the power supply voltage to output the first reference voltage. Optionally, the first reference voltage also changes with the power supply voltage, and the power supply voltage is divided and filtered to obtain a first reference voltage that changes proportionally to the power supply voltage, so that the first voltage output by the linear voltage regulator unit can also change proportionally to the power supply voltage, and the first reference voltage after the voltage divider filter has a certain PSRR (Power Supply Rejection Ratio, power supply rejection ratio), so that the first voltage adjusted by the first reference voltage can also have a good power supply rejection ratio.

[0061] As an implementation mode, in the microphone circuit of the present invention, the first voltage output by the low-dropout linear regulator module 50 is 0.95 times the power supply voltage, the voltage division coefficient of the voltage division module and the efficiency factor of the charge pump module 10 are both 0.5, and the second bias voltage VL=0.95VDD×0.5=0.475VDD, wherein VDD represents the power supply voltage and VL represents the second bias voltage. It can be seen that in the microphone circuit, no matter how the power supply voltage changes, the second bias voltage is close to 0.5 times the power supply voltage, and the second bias voltage is the input DC voltage of the amplifier module, so the voltage of the output signal of the amplifier module 30 will always be close to 0.5 times VDD. It should be clear that the relationship between the first voltage output by the low-dropout linear regulator module and the power supply voltage is determined by the specific design and performance of the low-dropout linear regulator module.

[0062] It is understandable that in the embodiments of the present invention, no corresponding restrictions are set for the specific structure of the voltage-dividing filter unit, because the voltage-dividing filter unit is a relatively mature part in the prior art field, and the focus and goal of the embodiments of the present invention are not to innovate or explore the specific structures of these two units. Exemplarily, a voltage-dividing filter unit can be configured to include a voltage-dividing circuit / device and a filtering circuit / device.

[0063] The above description is only an implementation mode of the present invention. It should be pointed out that, for ordinary technicians in this field, improvements can be made without departing from the creative concept of the present invention, but these all belong to the protection scope of the present invention.

Claims

1. A microphone circuit, characterized in that: include: A charge pump module, connected to a first end of an external microphone, for receiving a preset first voltage, generating a first bias voltage required for the microphone to work according to the first voltage and outputting the first bias voltage to the microphone; an amplification module, connected to the second end of the microphone, and configured to receive a voltage signal output by the microphone, and amplify the voltage signal and output it as an output signal of the microphone circuit; A voltage divider module is connected to the second end of the microphone and the amplifying module, and is used for receiving the first voltage, dividing the first voltage to generate a second bias voltage required for the microphone to work and outputting it to the microphone, and outputting the second bias voltage to the amplifying module as a bias voltage of the amplifying module.

2. The microphone circuit according to claim 1, characterized in that: The charge pump module comprises at least one stage of charge pumps connected in cascade, the output end of each stage of charge pumps is connected to the input end of the next stage of charge pumps, the input end of the first stage of charge pumps is grounded, and the output end of the last stage of charge pumps is connected to the first end of the microphone; The reference voltage of the first-stage charge pump is the first voltage, and the reference voltages of the charge pumps of each stage after the first-stage charge pump are all preset charge pump reference voltages.

3. The microphone circuit according to claim 2, characterized in that: The ratio of the second bias voltage output by the voltage divider module to the first voltage received by the voltage divider module is equal to the ratio of the output voltage of the first-stage charge pump to the first voltage received by the first-stage charge pump.

4. The microphone circuit according to claim 2, characterized in that: Each stage of the charge pump comprises an enable terminal, and the enable terminal of each charge pump is used to receive a corresponding enable signal, and each enable signal is used to control the corresponding charge pump; When the enable signal is at a first level, the charge pump adjusts the input voltage it receives according to the reference voltage it receives, and outputs the adjusted input voltage as the output voltage; when the enable signal is at a second level, the charge pump outputs the input voltage as the output voltage.

5. The microphone circuit according to claim 1, characterized in that: The amplification module includes at least one stage of coupled amplifiers, the output end of each stage of the amplifier is connected to the input end of the next stage of the amplifier, and the input end of the first stage of the amplifier is respectively connected to the second end of the microphone and the voltage divider module, and the output end of the final stage of the amplifier is used to output the output signal of the microphone circuit.

6. The microphone circuit according to claim 1, characterized in that: Also includes: The low voltage difference linear regulator module is used to connect to a power supply, perform voltage stabilization processing on the power supply voltage to obtain the first voltage, and output the first voltage to the charge pump module and the voltage divider module.

7. The microphone circuit according to claim 6, characterized in that: The low dropout linear regulator module comprises: A linear voltage stabilizing unit, used for connecting to the power supply, stabilizing the power supply voltage and outputting the first voltage; a feedback unit, configured to receive the first voltage and perform voltage division processing on the first voltage to generate a feedback voltage; The linear voltage stabilization unit is further configured to receive the feedback voltage and a preset first reference voltage, and linearly regulate the first voltage according to the feedback voltage and the first reference voltage.

8. The microphone circuit according to claim 7, characterized in that: The low dropout linear regulator module further includes: The voltage division and filtering unit is used to connect to a power supply, divide and filter the power supply voltage to output the first reference voltage.

9. The microphone circuit according to claim 1, characterized in that: The microphone is a MEMS microphone.

Images