阅读说明：本技术 一种mems麦克风偏置电路及mems麦克风 (MEMS microphone bias circuit and MEMS microphone ) 是由 刘洋 王艳梅 于 2021-06-29 设计创作，主要内容包括：本公开涉及一种MEMS麦克风偏置电路,其特征在于,包括：振荡器、时钟幅度调节模块、基准电压模块和电荷泵组,所述振荡器的输出端连接所述时钟幅度调节模块的输入端,所述振荡器用于向所述时钟幅度调节模块发送时钟信号；所述时钟幅度调节模块的输出端连接所述电荷泵组,所述时钟幅度调节模块用于调节所述时钟信号的幅度；所述基准电压模块连接所述电荷泵组,用于为所述电荷泵组的运行提供输入电压；所述电荷泵组包括前级电荷泵和输出级电荷泵,所述前级电荷泵位于所述电荷泵组的输入端,所述输出级电荷泵位于所述电荷泵组的输出端,所述电荷泵组用于输出待处理的偏置电压。能够输出稳定的偏置电压,使MEMS麦克风具有很好的灵敏度。(The present disclosure relates to a MEMS microphone bias circuit, comprising: the output end of the oscillator is connected with the input end of the clock amplitude adjusting module, and the oscillator is used for sending a clock signal to the clock amplitude adjusting module; the output end of the clock amplitude adjusting module is connected with the charge pump group, and the clock amplitude adjusting module is used for adjusting the amplitude of the clock signal; the reference voltage module is connected with the charge pump group and is used for providing input voltage for the operation of the charge pump group; the charge pump group comprises a preceding stage charge pump and an output stage charge pump, the preceding stage charge pump is located at the input end of the charge pump group, the output stage charge pump is located at the output end of the charge pump group, and the charge pump group is used for outputting to-be-processed bias voltage. The MEMS microphone can output stable bias voltage, so that the MEMS microphone has good sensitivity.)

1. A MEMS microphone biasing circuit, comprising: an oscillator, a clock amplitude adjusting module, a reference voltage module and a charge pump group,

the output end of the oscillator is connected with the input end of the clock amplitude adjusting module, and the oscillator is used for sending a clock signal to the clock amplitude adjusting module;

the output end of the clock amplitude adjusting module is connected with the charge pump group, and the clock amplitude adjusting module is used for adjusting the amplitude of the clock signal;

the reference voltage module is connected with the charge pump group and is used for providing input voltage for the operation of the charge pump group;

the charge pump group comprises a preceding stage charge pump and an output stage charge pump, the preceding stage charge pump is located at the input end of the charge pump group, the output stage charge pump is located at the output end of the charge pump group, and the charge pump group is used for outputting to-be-processed bias voltage.

2. The bias circuit of claim 1, wherein the pre-charge pump comprises a first pre-charge pump to an Nth pre-charge pump connected in sequence, where N is an integer greater than or equal to 1.

3. The MEMS microphone biasing circuit of claim 1, wherein the clock amplitude adjustment module comprises a clock amplitude doubling circuit and a frequency halving circuit,

the first output end of the clock amplitude doubling circuit is connected with the input end of the frequency halving circuit, and the second output end of the clock amplitude doubling circuit is connected with the first input end of the output-stage charge pump;

and a first output end of the frequency-halving circuit is connected with the first preceding stage charge pump, and a second output end of the frequency-halving circuit is connected with a second input end of the output stage charge pump.

4. The MEMS microphone biasing circuit of claim 1, wherein the reference voltage module comprises a bandgap reference circuit and a voltage regulator,

the band-gap reference circuit is connected to the charge pump group through the voltage stabilizer.

5. A MEMS microphone biasing circuit according to claim 1, wherein the reference voltage block is further connected to the clock amplitude adjustment block, wherein the reference voltage block is connected to a clock amplitude doubling circuit for providing a supply voltage to the clock amplitude doubling circuit.

6. The MEMS microphone biasing circuit of claim 1, further comprising a low pass filter, wherein the output terminal of the output stage charge pump is connected to the low pass filter, and the low pass filter is configured to perform noise reduction on the bias voltage to be processed.

7. The bias circuit of claim 1, further comprising a power module and a voltage detection module, wherein the power module is connected to the low pass filter through the voltage detection module to provide an operating voltage for the low pass filter.

8. The MEMS microphone biasing circuit of claim 7, wherein the voltage detection module is configured to receive a power voltage of the power module, and control the low pass filter to be turned on or off according to the power voltage and a predetermined voltage.

9. The MEMS microphone biasing circuit of claim 8, wherein controlling the low pass filter to be turned on and off according to the magnitude of the power voltage and a predetermined voltage comprises:

controlling the low-pass filter to be started under the condition that the power supply voltage is greater than a preset voltage;

and controlling the low-pass filter to be closed under the condition that the power supply voltage is less than a preset voltage.

10. A MEMS microphone, comprising a housing, a MEMS chip disposed within the housing, and a MEMS microphone biasing circuit of claims 1-9,

the bias circuit is connected with the MEMS chip and used for providing bias voltage for the MEMS chip.

Technical Field

The embodiment of the disclosure relates to the technical field of microphone circuits, and more particularly to an MEMS microphone bias circuit and an MEMS microphone.

Background

A MEMS (Micro-Electro-Mechanical System) microphone needs a stable and low-noise bias voltage to convert the Mechanical deformation generated by the sound pressure acting on the diaphragm of the MEMS chip into an electrical signal with a certain amplitude. The bias voltage is about 10V, which is much larger than the power voltage, so a circuit module is needed to generate a dc level much larger than the power voltage to provide the bias voltage for the MEMS chip.

The stability of the bias voltage directly affects the sensitivity of the microphone, and the noise of the bias voltage also affects the noise of the output electrical signal of the MEMS microphone. Therefore, the stability and low noise of the bias voltage are critical in the design process of the bias voltage. However, the stability of the current bias circuit is not high and there is a noise effect, thereby affecting the sensitivity of the microphone.

Disclosure of Invention

An object of the disclosed embodiments is to provide an MEMS microphone bias circuit and an MEMS microphone, which can solve the problems of unstable signal and low sensitivity of the existing microphone bias circuit.

According to a first aspect of the present disclosure, there is provided a MEMS microphone biasing circuit comprising: the output end of the oscillator is connected with the input end of the clock amplitude adjusting module, and the oscillator is used for sending a clock signal to the clock amplitude adjusting module; the output end of the clock amplitude adjusting module is connected with the charge pump group, and the clock amplitude adjusting module is used for adjusting the amplitude of the clock signal; the reference voltage module is connected with the charge pump group and is used for providing input voltage for the operation of the charge pump group; the charge pump group comprises a preceding stage charge pump and an output stage charge pump, the preceding stage charge pump is located at the input end of the charge pump group, the output stage charge pump is located at the output end of the charge pump group, and the charge pump group is used for outputting to-be-processed bias voltage.

Further, the preceding stage charge pump includes a first preceding stage charge pump to an nth preceding stage charge pump connected in sequence, where N is an integer greater than or equal to 1.

Further, the clock amplitude adjusting module comprises a clock amplitude doubling circuit and a frequency halving circuit,

the first output end of the clock amplitude doubling circuit is connected with the input end of the frequency halving circuit, and the second output end of the clock amplitude doubling circuit is connected with the first input end of the output-stage charge pump;

and a first output end of the frequency-halving circuit is connected with the first preceding stage charge pump, and a second output end of the frequency-halving circuit is connected with a second input end of the output stage charge pump.

Further, the reference voltage module comprises a band gap reference circuit and a voltage stabilizer, and the band gap reference circuit is connected to the charge pump group through the voltage stabilizer.

Further, the reference voltage module is further connected to the clock amplitude adjusting module, wherein the reference voltage module is connected to the clock amplitude doubling circuit and is configured to provide a power supply voltage for the clock amplitude doubling circuit.

Further, the bias circuit further comprises a low-pass filter, an output end of the output stage charge pump is connected with the low-pass filter, and the low-pass filter is used for performing noise reduction processing on the bias voltage to be processed.

Furthermore, the bias circuit further comprises a power supply module and a voltage detection module, wherein the power supply module is connected to the low-pass filter through the voltage detection module and provides working voltage for the low-pass filter.

Further, the voltage detection module is configured to receive a power supply voltage of the power supply module, and control the on and off of the low-pass filter according to the power supply voltage and a preset voltage.

Further, controlling the on and off of the low pass filter according to the magnitude of the power voltage and a preset voltage includes: controlling the low-pass filter to be started under the condition that the power supply voltage is greater than a preset voltage; and controlling the low-pass filter to be closed under the condition that the power supply voltage is less than a preset voltage.

According to a second aspect of the present disclosure, there is further provided a MEMS microphone, wherein the microphone includes a housing, a MEMS chip disposed in the housing, and the MEMS microphone bias circuit of the first aspect, and the bias circuit is connected to the MEMS chip and configured to provide a bias voltage to the MEMS chip.

One beneficial effect of the embodiments of the present disclosure is that the present embodiment sets a clock amplitude doubling circuit, an output stage charge pump, and other devices in the bias circuit, so that the bias voltage output by the circuit is more stable, and the noise of the bias voltage is lower, thereby enabling the MEMS microphone to have good stability and sensitivity.

Other features of embodiments of the present disclosure and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which is to be read in connection with the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the disclosure and together with the description, serve to explain the principles of the embodiments of the disclosure.

FIG. 1 is a prior art schematic diagram of the present invention;

fig. 2 is a schematic diagram of a component structure of a MEMS microphone bias circuit provided in this embodiment;

fig. 3 is a schematic structural diagram of a MEMS microphone provided in this embodiment.

In the figure: the circuit comprises an oscillator 01, a clock amplitude adjusting module 02, a charge pump group 03, a pre-stage charge pump 04, an output stage charge pump 05, a clock amplitude doubling circuit 06, a frequency halving circuit 07, a band gap reference circuit 08, a voltage regulator 09, a low-pass filter 10, a voltage detection module 11, a power supply module 12, a reference voltage module 13, a shell 300 and a MEMS chip 20.

Detailed Description

Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.

In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

Before the embodiment is described, an application background of the embodiment is described first, the MEMS microphone includes a diaphragm and a back plate, the diaphragm is mechanically deformed under the action of sound pressure, and the deformation may cause a change in an equivalent capacitance between the diaphragm and the back plate, thereby causing a change in voltage, and realizing a function of converting a sound pressure signal into an electrical signal. However, the MEMS needs a stable and low-noise bias voltage to convert the mechanical deformation generated by the sound pressure acting on the MEMS diaphragm into an electrical signal with a certain amplitude. The bias voltage is about 10V, which is much larger than the power voltage, so a circuit module is needed to generate a dc level much larger than the power voltage to provide bias for the MEMS. Namely, the MEMS microphone bias circuit provided in the present embodiment.

Referring to fig. 1, fig. 1 is a schematic diagram of a conventional MEMS microphone bias circuit, in which a power supply drives an oscillator to generate a clock signal, a reference voltage circuit provides a voltage for a charge pump to operate, the charge pump generates a dc level meeting an MEMS bias voltage under the driving of the clock signal and the voltage signal, and the dc level is filtered by a low-pass filter to remove high-frequency ripples caused by the clock signal and then outputs the bias voltage to an MEMS chip of the MEMS microphone. However, the clock signal generated by the oscillator in the bias circuit shown in fig. 1 and the output voltage of the reference voltage circuit are both directly input to the charge pump, which brings certain noise to the circuit and affects the stability of the signal.

Accordingly, the present embodiment provides a MEMS microphone bias circuit, which, with reference to fig. 2, includes: the MEMS chip comprises an oscillator 01, a clock amplitude adjusting module 02, a reference voltage module 13 and a charge pump group 03, wherein the output end of the oscillator 01 is connected with the input end of the clock amplitude adjusting module 02 and used for sending a clock signal to the clock amplitude adjusting module 02, the output end of the clock amplitude adjusting module 02 is connected with the charge pump group 03 and used for adjusting the amplitude of the clock signal, the charge pump group 03 outputs a bias voltage to be processed according to the adjusted clock amplitude, and the bias voltage to be processed forms a bias voltage meeting the requirements of the MEMS chip after filtering. The reference voltage module 13 is connected to the charge pump group 03, and is configured to provide an input voltage for the operation of the charge pump group 03.

The charge pump is a switched capacitor voltage converter, a DC-DC converter which can store energy by using a capacitor and can increase or decrease the input voltage, and an FET switch array in the charge pump controls the charging and discharging of a flying capacitor in a certain manner, so that the input voltage is multiplied or decreased by a certain factor to obtain the required output voltage. Therefore, in the embodiment, the charge pump group 03 is adopted to perform multi-stage combination, so that the output voltage of the charge pump is increased to achieve the bias voltage required by the MEMS chip.

The charge pump group 03 comprises a pre-stage charge pump 04 and an output stage charge pump 05, wherein the pre-stage charge pump 04 is located at the input end of the charge pump group 03, and the output stage charge pump 05 is located at the output end of the charge pump group 03, that is, the pre-stage charge pump 04 and the output stage charge pump 05 are sequentially arranged between the input end and the output end of the charge pump group 03. The pre-stage charge pump comprises a first pre-stage charge pump and an Nth pre-stage charge pump which are sequentially connected, wherein N is an integer larger than or equal to 1.

For each stage of charge pump, the low voltage dc level input to the charge pump set 03 can be raised by one clock amplitude, and thus, the number N of the preceding stage charge pumps in this embodiment is determined by the difference between the amplitude of the bias voltage satisfying the operation of the MEMS chip and the clock amplitude input to the charge pump set 03. Since the amplitude of the bias voltage satisfying the operation of the MEMS chip is generally fixed, for example, the bias voltage required by the MEMS chip is generally a high voltage level around 10V, the value of N is determined by the clock amplitude input to the charge pump group 03. In view of this, in the present embodiment, a clock amplitude adjusting module 02 is disposed between the oscillator 01 and the charge pump group 03, and is used to increase the amplitude of the clock signal output by the oscillator 01 to increase the clock amplitude input to the charge pump group 03, so as to reduce the number of pre-stage charge pumps, and reduce power consumption.

As can be seen from fig. 1, in the conventional bias circuit, the driving of the charge pump is controlled by the clock signal of the oscillator 01, however, under the condition of being controlled by the same signal, different transistors in the charge pump have the possibility of being turned on at the same time, that is, the different transistors have the possibility of appearing in phase, so that the charge pump leaks charges to the bias voltage, and noise of the bias voltage is increased. Therefore, referring to fig. 2, the charge pump unit 03 in this embodiment is provided with an output stage charge pump 05, the output stage charge pump 05 is controlled by two sets of clock signals, the two sets of clock signals are clock signals with different frequencies, and it is able to avoid the situation that the clock signals are low at the same time or high at the same time, for example, when the output stage charge pump 05 is a PMOS transistor, the situation that the clock signals are low at the same time may occur, and when the output stage charge pump 05 is an NMOS transistor, the situation that the clock signals are high at the same time may occur. The setting completes the effect that the clocks are not overlapped, the possibility that the output transistors are conducted at the same time can be effectively inhibited, the charge leakage can be effectively reduced, and the noise is reduced.

Therefore, in the present embodiment, the clock amplitude adjusting module 02 includes a clock amplitude doubling circuit 06 and a frequency halving circuit 07, a first output terminal of the clock amplitude doubling circuit 06 is connected to an input terminal of the frequency halving circuit 07, and a second output terminal of the clock amplitude doubling circuit 06 is connected to a first input terminal of the output stage charge pump 05; a first output end of the frequency-halving circuit 07 is connected with the first preceding stage charge pump, and a second output end of the frequency-halving circuit 07 is connected with a second input end of the output stage charge pump 05. The function of the divide-by-two circuit 07 is to convert the same clock signal into a clock signal with a frequency of one half of the input frequency through a certain circuit structure, that is, in this embodiment, the divide-by-two circuit 07 is used to divide the frequency of the clock signal generated by the oscillator 01 to obtain a new clock signal with a frequency of one half of the frequency of the clock signal of the oscillator, and therefore, two sets of signals for controlling the output stage charge pump 05 are the clock signal generated by the oscillator 01 and the set of clock signals output by the divide-by-two circuit 07 respectively.

It should be noted that the clock amplitude doubling circuit 06 increases the amplitude of the clock signal and does not change the duty ratio of the clock signal, and the divide-by-two circuit 07 changes the frequency of the clock signal, so that although the clock signal passed through the clock amplitude doubling circuit 06 is divided by the divide-by-two circuit 07 into 2 clock signals whose frequency is one-half of the input frequency, the amplitude of the clock signal input to the charge pump is not changed.

In this embodiment, the reference voltage module 13 includes a bandgap reference circuit 08 and a voltage regulator 09, and the bandgap reference circuit 08 is connected to the charge pump unit 03 through the voltage regulator 09. The bandgap reference circuit 08 can provide a stable voltage irrelevant to the power supply voltage and the temperature for the charge pump unit 03 to be used as the input of the charge pump unit 03, and can ensure the stability of the output voltage of the charge pump unit 03. However, the bandgap reference circuit 08 has high output impedance and poor drivability, so that the output of the bandgap reference voltage is easily affected by the load variation, and it is difficult to drive the charge pump. Therefore, the voltage regulator 09 is disposed between the bandgap reference circuit 08 and the charge pump group 03 in this embodiment to realize the function of impedance conversion, so that the whole reference voltage module 13 has a large input impedance and a small output impedance, and the defect of poor driving performance of the bandgap reference circuit 08 can be effectively overcome. The output of the band-gap reference voltage is not influenced by the load change of the band-gap reference voltage, and the charge pump is driven to work more stably. Moreover, the voltage regulator 09 can increase the level of the output voltage of the bandgap reference circuit 08 to a certain extent, so that the input reference of the subsequent charge pump circuit is increased, and the number of stages of the charge pump can be reduced to a certain extent.

In this embodiment, the reference voltage module 13 is further connected to the clock amplitude adjusting module 02, wherein the reference voltage module 13 is connected to the clock amplitude doubling circuit 06. For providing a supply voltage for the normal operation of the circuits in the clock amplitude adjustment module 02.

In a possible example, the bias circuit further comprises a low pass filter 10, the output terminal of the output stage charge pump 05 is connected to the low pass filter 10, and the low pass filter 10 is used for performing noise reduction processing on the bias voltage to be processed. The clock signal of the charge pump group 03 brings high-frequency ripples, that is, the bias voltage signal to be processed is output by the charge pump group 03, so that the output large-level reference voltage generated by the charge pump group 03 cannot be directly provided to the MEMS chip, and in order to further reduce the noise of the bias voltage, a low-pass filter 10 needs to be added at the output of the charge pump to filter the high-frequency ripples and generate the bias voltage meeting the requirements of the MEMS chip.

In addition, when a problem occurs in power-on of the power supply voltage, for example, the power supply is powered on slowly, or there is a case that the power supply is powered on unstably, because the power supply voltages at which the modules of the circuit start to operate are different, a part of circuits may start to operate, and a part of circuits do not start to operate, the circuits may enter an incorrect state. Therefore, the bias circuit of the present embodiment further includes a power supply module 12 and a voltage detection module 11, and the power supply module 12 is connected to the low pass filter 10 through the voltage detection module 11. The power supply module 12 is used to provide a power supply voltage for each circuit of the bias circuit and an operating voltage for the low pass filter. For example, the power supply voltage supplies voltage for the operation of the oscillator 01 and the low pass filter 10. The voltage detection module 11 is configured to detect whether the power voltage is stably output, receive the power voltage of the power module 12, and control the on/off of the low-pass filter 10 according to the power voltage and a preset voltage. Controlling the low-pass filter 10 to be started under the condition that the power supply voltage is greater than the preset voltage; in case the supply voltage is less than the preset voltage, the low pass filter 10 is controlled to be turned off. The preset voltage is a voltage at which the power supply voltage meets normal operation of all circuits and devices in the bias circuit, and can be specifically set according to device requirements in an actual circuit.

That is, by turning off the low-pass filter 10 before the power supply voltage does not reach the standard value at which all circuits can normally operate, the bias circuit does not supply the bias voltage to the MEMS chip, and the MEMS microphone does not start operating.

By improving the conventional bias circuit, the bias voltage output by the circuit can be more stable, and the noise of the bias voltage is lower, so that the MEMS microphone has good stability and sensitivity.

The MEMS microphone in this embodiment, referring to fig. 3, includes a housing 300, a MEMS chip 20 disposed in the housing, and a MEMS microphone bias circuit in the above embodiment, wherein the MEMS microphone bias circuit is connected to the MEMS chip 20 for providing a bias voltage to the MEMS chip.

The MEMS chip 20 may include a diaphragm and a back plate, and the bias voltage generated by the MEMS microphone bias circuit acts on the diaphragm, so that the diaphragm is mechanically deformed under the action of sound pressure, and this deformation may cause the equivalent capacitance between the diaphragm and the back plate to change, thereby causing the change of voltage, and realizing the function of converting the sound pressure signal into an electrical signal.

Wherein the MEMS microphone bias circuit and the MEMS chip 20 may be integrated on the same circuit board to form a microphone bias voltage integrated device with high sensitivity.

By improving the conventional bias circuit, the bias voltage output by the circuit can be more stable, and the noise of the bias voltage is lower, so that the MEMS microphone has good stability and sensitivity.

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein. The scope of the invention is defined by the appended claims.