阅读说明：本技术 应用于mems加速度传感器的c/v转换系统及其控制方法 (C/V conversion system applied to MEMS acceleration sensor and control method thereof ) 是由 齐敏 马玉良 乔东海 于 2020-12-24 设计创作，主要内容包括：本发明公开了一种应用于MEMS加速度传感器的C/V转换系统及其控制方法,包括：第一输入信号Vrp；第二输入信号Vrn；传感电容模块,其与第一输入信号Vrp和第二输入信号Vrn连接；第一开关电容放大模块,其与传感电容模块连接,第一开关电容放大模块对传感电容模块输出的信号进行处理,输出第一输出信号Voutn；第二开关电容放大模块；其与第一开关电容放大模块,第二开关电容放大模块对第一开关电容放大模块输出的信号进行处理,输出第二输出信号Voutp；其中,第二输出信号Voutp与第一输出信号Voutn为差分的互补信号。其形成差分的互补输出信号,加倍了信号范围,提高灵敏度,抑制了电源上由数字电路引入的的共模噪声。(The invention discloses a C/V conversion system applied to an MEMS acceleration sensor and a control method thereof, wherein the C/V conversion system comprises: a first input signal Vrp; a second input signal Vrn; a sense capacitance module connected to a first input signal Vrp and a second input signal Vrn; the first switched capacitor amplification module is connected with the sensing capacitor module, processes the signal output by the sensing capacitor module and outputs a first output signal Voutn; a second switched capacitor amplification module; the second switched capacitor amplification module processes the signal output by the first switched capacitor amplification module and outputs a second output signal Voutp; the second output signal Voutp and the first output signal Voutn are complementary signals of a difference. The differential complementary output signal is formed, the signal range is doubled, the sensitivity is improved, and the common mode noise introduced by a digital circuit on a power supply is restrained.)

1. A C/V conversion system for a MEMS acceleration sensor, comprising:

a first input signal Vrp;

a second input signal Vrn;

the sensor comprises a sensing capacitor module, a first input signal Vrp and a second input signal Vrn, wherein the sensing capacitor module comprises an acceleration sensor capacitor, and the capacitance of the acceleration sensor capacitor changes along with the change of acceleration;

the first switched capacitor amplification module is connected with the sensing capacitor module, processes the signal output by the sensing capacitor module and outputs a first output signal Voutn;

a second switched capacitor amplification module; the second switched capacitor amplification module processes the signal output by the first switched capacitor amplification module and outputs a second output signal Voutp;

the second output signal Voutp and the first output signal Voutn are differential complementary signals.

2. The C/V conversion system applied to a MEMS acceleration sensor according to claim 1, characterized in that the acceleration sensor capacitance comprises a first capacitance Ct and a second capacitance Cb;

a first switch S1 is connected between the first input signal Vrp and the first end of the first capacitor Ct, and a second switch S2 is connected between the second input signal Vrn and the first end of the first capacitor Ct;

a third switch S3 is connected between the first input signal Vrp and the first end of the second capacitor Cb, and a fourth switch S4 is connected between the second input signal Vrn and the first end of the second capacitor Cb.

3. The C/V conversion system applied to the MEMS acceleration sensor of claim 1, wherein the acceleration sensor capacitance includes a first capacitance Ct, a second capacitance Cb, a first selection switch, and a second selection switch;

one end of the first selection switch is connected with a first end of a first capacitor Ct, and a selection end of the first selection switch is connected with a first input signal Vrp or a second input signal Vrn;

one end of the second selection switch is connected to the first end of the second capacitor Cb, and a selection end of the second selection switch is connected to the first input signal Vrp or the second input signal Vrn.

4. The C/V conversion system applied to the MEMS acceleration sensor of claim 2 or 3, wherein the first switch capacitance amplifying module comprises a first operational amplifier U1, a fifth switch S5, a sixth switch S6 and a seventh switch S7;

a negative input end of the first operational amplifier U1 is connected to a second end of the first capacitor Ct, a second end of the second capacitor Cb, and a first end of the third capacitor Cf, a positive input end of the first operational amplifier U1 is grounded, and an output end of the first operational amplifier U1 outputs a first output signal Voutn;

a fifth switch S5 is connected between the negative input end of the first operational amplifier U1 and the output end of the first operational amplifier U1, a seventh switch S7 is connected between the second end of the third capacitor Cf and the output end of the first operational amplifier U1, one end of the sixth switch S6 is connected to the second end of the third capacitor Cf, and the other end of the sixth switch S6 is grounded.

5. The C/V conversion system applied to the MEMS acceleration sensor, wherein the second switch capacitance amplifying module comprises a second operational amplifier U2, a fourth capacitor Cd, a fifth capacitor Ce, an eighth switch S8, a ninth switch S9, a tenth switch S10, an eleventh switch S11 and a twelfth switch S12;

a first end of the fifth capacitor Ce is connected to the output end of the first operational amplifier U1 through an eighth switch S8, one end of the ninth switch S9 is connected to the first end of the fifth capacitor Ce, and the other end of the ninth switch S9 is grounded;

a negative input end of the second operational amplifier U2 is connected to a first end of a fourth capacitor Cd and a second end of a fifth capacitor Ce, a positive input end of the second operational amplifier is grounded, and an output end of the second operational amplifier U2 outputs a second output signal Voutp;

a tenth switch S10 is connected between the negative input end of the second operational amplifier U2 and the output end of the second operational amplifier U2, a twelfth switch S12 is connected between the second end of the fourth capacitor Cd and the output end of the second operational amplifier U2, one end of the twelfth switch S12 is connected to the second end of the fourth capacitor Cd, and the other end of the twelfth switch S12 is grounded.

6. The C/V conversion system applied to the MEMS acceleration sensor as recited in claim 5, wherein the fourth capacitance Cd is equal to the capacitance value of the fifth capacitance Ce.

7. A control method of a C/V conversion system, based on the C/V conversion system applied to the MEMS acceleration sensor in claim 5 or 6, is characterized by comprising a first timing signal and a second timing signal for controlling the on and off of different switches;

the first timing signal controls the on and off of a first switch S1, a fourth switch S4, a fifth switch S5, a sixth switch S6, a ninth switch S9, a tenth switch S10 and an eleventh switch S11;

the second timing signal controls the on and off of a second switch S2, a third switch S3, a seventh switch S7, an eighth switch S8 and a twelfth switch S12;

and when the switch controlled by the first timing signal is turned on, the switch controlled by the second timing signal is turned off.

8. The method of controlling a C/V conversion system according to claim 7, wherein the first timing signal is a square waveform.

9. The control method of a C/V conversion system according to claim 8, wherein when the fourth capacitance Cd is equal to a capacitance value of a fifth capacitance Ce,

the first output signal

The second output signal

Technical Field

The invention relates to the field of integrated circuits, in particular to a C/V conversion system applied to an MEMS acceleration sensor and a control method thereof.

Background

The MEMS capacitive acceleration sensor is an acceleration sensor based on the capacitive principle. The acceleration can be represented by the variation of the capacitance value of the capacitor by detecting the variation of the distance between the two polar plates of the capacitor along with the movement, and the acceleration sensor is widely applied to various fields. Because the capacitive acceleration sensor only completes the work of converting the acceleration into the change of the capacitance value, a subsequent C/V conversion circuit is required to complete the work of converting the capacitance value into the analog signal output. Because the conversion circuit chip usually does not only have a reading circuit, but also integrates a signal processing circuit and a digital circuit module, how to reduce the influence of noise introduced by the modules on output signals and further accurately reflect the variable quantity of capacitance values is an important consideration when designing the C/V conversion circuit.

Although the existing single-ended C/V conversion circuit is simple to implement and high in power consumption efficiency, in a high-precision and high-integration MEMS acceleration sensor reading chip, because a large number of digital circuits are integrated on the chip for signal processing and time sequence control, the digital circuits introduce non-negligible noise into a power supply and the ground in the chip, and the noise can be directly reflected on an output port, so that the signal-to-noise ratio of an analog circuit is reduced.

Disclosure of Invention

The invention aims to provide a C/V conversion system applied to an MEMS acceleration sensor and a control method thereof, and the C/V conversion system and the control method thereof

In order to solve the above technical problem, the present invention provides a C/V conversion system applied to a MEMS acceleration sensor, comprising:

a first input signal Vrp;

a second input signal Vrn;

the sensor comprises a sensing capacitor module, a first input signal Vrp and a second input signal Vrn, wherein the sensing capacitor module comprises an acceleration sensor capacitor, and the capacitance of the acceleration sensor capacitor changes along with the change of acceleration;

the first switched capacitor amplification module is connected with the sensing capacitor module, processes the signal output by the sensing capacitor module and outputs a first output signal Voutn;

a second switched capacitor amplification module; the second switched capacitor amplification module processes the signal output by the first switched capacitor amplification module and outputs a second output signal Voutp;

the second output signal Voutp and the first output signal Voutn are differential complementary signals.

Preferably, the acceleration sensor capacitance includes a first capacitance Ct and a second capacitance Cb;

a first switch S1 is connected between the first input signal Vrp and the first end of the first capacitor Ct, and a second switch S2 is connected between the second input signal Vrn and the first end of the first capacitor Ct;

a third switch S3 is connected between the first input signal Vrp and the first end of the second capacitor Cb, and a fourth switch S4 is connected between the second input signal Vrn and the first end of the second capacitor Cb.

Preferably, the acceleration sensor capacitance includes a first capacitance Ct, a second capacitance Cb, a first selection switch, and a second selection switch;

one end of the first selection switch is connected with a first end of a first capacitor Ct, and a selection end of the first selection switch is connected with a first input signal Vrp or a second input signal Vrn;

one end of the second selection switch is connected to the first end of the second capacitor Cb, and a selection end of the second selection switch is connected to the first input signal Vrp or the second input signal Vrn.

Preferably, the first switched capacitor amplification module comprises a first operational amplifier U1, a fifth switch S5, a sixth switch S6 and a seventh switch S7;

a negative input end of the first operational amplifier U1 is connected to a second end of the first capacitor Ct, a second end of the second capacitor Cb, and a first end of the third capacitor Cf, a positive input end of the first operational amplifier U1 is grounded, and an output end of the first operational amplifier U1 outputs a first output signal Voutn;

a fifth switch S5 is connected between the negative input end of the first operational amplifier U1 and the output end of the first operational amplifier U1, a seventh switch S7 is connected between the second end of the third capacitor Cf and the output end of the first operational amplifier U1, one end of the sixth switch S6 is connected to the second end of the third capacitor Cf, and the other end of the sixth switch S6 is grounded.

Preferably, the second switched capacitor amplifying module comprises a second operational amplifier U2, a fourth capacitor Cd, a fifth capacitor Ce, an eighth switch S8, a ninth switch S9, a tenth switch S10, an eleventh switch S11 and a twelfth switch S12;

a first end of the fifth capacitor Ce is connected to the output end of the first operational amplifier U1 through an eighth switch S8, one end of the ninth switch S9 is connected to the first end of the fifth capacitor Ce, and the other end of the ninth switch S9 is grounded;

a negative input end of the second operational amplifier U2 is connected to a first end of a fourth capacitor Cd and a second end of a fifth capacitor Ce, a positive input end of the second operational amplifier is grounded, and an output end of the second operational amplifier U2 outputs a second output signal Voutp;

a tenth switch S10 is connected between the negative input end of the second operational amplifier U2 and the output end of the second operational amplifier U2, a twelfth switch S12 is connected between the second end of the fourth capacitor Cd and the output end of the second operational amplifier U2, one end of the twelfth switch S12 is connected to the second end of the fourth capacitor Cd, and the other end of the twelfth switch S12 is grounded.

Preferably, the fourth capacitor Cd is equal to the capacitance value of the fifth capacitor Ce.

The invention discloses a control method of a C/V conversion system, which is based on the C/V conversion system applied to an MEMS acceleration sensor and comprises a first time sequence signal and a second time sequence signal for controlling the on-off of different switches;

the first timing signal controls the on and off of a first switch S1, a fourth switch S4, a fifth switch S5, a sixth switch S6, a ninth switch S9, a tenth switch S10 and an eleventh switch S11;

the second timing signal controls the on and off of a second switch S2, a third switch S3, a seventh switch S7, an eighth switch S8 and a twelfth switch S12;

and when the switch controlled by the first timing signal is turned on, the switch controlled by the second timing signal is turned off.

Preferably, the first timing signal is a square waveform.

Preferably, when the fourth capacitor Cd is equal to the capacitance value of the fifth capacitor Ce,

the first output signal

The second output signal

The C/V conversion system applied to the MEMS acceleration sensor has the beneficial effects that:

1. according to the invention, differential complementary signals are formed, so that on one hand, the signal range can be doubled, and the sensitivity is improved; on the other hand, differential signals suppress well the common mode noise introduced by the digital circuits on the power supply.

2. The circuit provided by the invention has higher signal-to-noise ratio, can be well compatible and integrated with other digital circuits, improves the precision and the integration level of products on one hand, and expands the application range of the MEMS acceleration sensor reading circuit on the other hand.

The control method of the C/V conversion system has the beneficial effects that:

the invention controls the on-off of a first switch S1, a fourth switch S4, a fifth switch S5, a sixth switch S6, a ninth switch S9, a tenth switch S10 and an eleventh switch S11 through a first time sequence signal; the second timing signal controls the on and off of the second switch S2, the third switch S3, the seventh switch S7, the eighth switch S8 and the twelfth switch S12. When the switch controlled by the first time sequence signal is turned on, the switch controlled by the second time sequence signal is turned off, so that differential complementary output signals are formed conveniently, the signal range is doubled, the sensitivity is improved, and common mode noise introduced by a digital circuit on a power supply is suppressed.

Drawings

FIG. 1 is a schematic diagram of a C/V conversion system for a MEMS acceleration sensor according to the present invention;

FIG. 2 is a timing diagram of the C/V conversion system of the present invention.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

Referring to fig. 1, the invention discloses a C/V conversion system applied to a MEMS acceleration sensor, which includes a first input signal Vrp, a second input signal Vrn, a sensing capacitance module, a first switched capacitance amplification module, and a second switched capacitance amplification module.

The sensing capacitor module is connected with a first input signal Vrp and a second input signal Vrn, and comprises an acceleration sensor capacitor, and the capacitance of the acceleration sensor capacitor changes along with the change of acceleration. The capacitance variation of Ct and Cb is used to represent the magnitude of the acceleration, and the function of the circuit is to convert the variation into an analog signal and output the analog signal. Cf represents the capacitance in the readout circuit, which can be adjusted according to the voltage amplitude requirements of the output signal.

The first switch capacitor amplification module is connected with the sensing capacitor module, processes the signal output by the sensing capacitor module and outputs a first output signal Voutn.

The second switch capacitor amplification module processes the signal output by the first switch capacitor amplification module and outputs a second output signal Voutp; the second output signal Voutp and the first output signal Voutn are complementary signals of a difference.

According to the invention, differential complementary signals are formed, so that on one hand, the signal range can be doubled, and the sensitivity is improved; on the other hand, differential signals suppress well the common mode noise introduced by the digital circuits on the power supply.

The circuit provided by the invention has higher signal-to-noise ratio, can be well compatible and integrated with other digital circuits, improves the precision and the integration level of products on one hand, and expands the application range of the MEMS acceleration sensor reading circuit on the other hand.

Specifically, the acceleration sensor capacitance includes a first capacitance Ct and a second capacitance Cb. A first switch S1 is connected between the first input signal Vrp and a first end of the first capacitance Ct, and a second switch S2 is connected between the second input signal Vrn and the first end of the first capacitance Ct. A third switch S3 is connected between the first input signal Vrp and the first end of the second capacitor Cb, and a fourth switch S4 is connected between the second input signal Vrn and the first end of the second capacitor Cb.

The acceleration sensor capacitance includes a first capacitance Ct, a second capacitance Cb, a first selection switch, and a second selection switch. One end of the first selection switch is connected to a first end of the first capacitor Ct, and a selection end of the first selection switch is connected to the first input signal Vrp or the second input signal Vrn. One end of the second selection switch is connected to the first end of the second capacitor Cb, and a selection end of the second selection switch is connected to the first input signal Vrp or the second input signal Vrn.

The first switched-capacitor amplification module includes a first operational amplifier U1, a fifth switch S5, a sixth switch S6, and a seventh switch S7. A negative input end of the first operational amplifier U1 is connected to a second end of the first capacitor Ct, a second end of the second capacitor Cb, and a first end of the third capacitor Cf, a positive input end of the first operational amplifier U1 is grounded, and an output end of the first operational amplifier U1 outputs a first output signal Voutn; a fifth switch S5 is connected between the negative input terminal of the first operational amplifier U1 and the output terminal of the first operational amplifier U1, a seventh switch S7 is connected between the second terminal of the third capacitor Cf and the output terminal of the first operational amplifier U1, one end of a sixth switch S6 is connected to the second terminal of the third capacitor Cf, and the other end of the sixth switch S6 is grounded.

The second switched capacitor amplification module comprises a second operational amplifier U2, a fourth capacitor Cd, a fifth capacitor Ce, an eighth switch S8, a ninth switch S9, a tenth switch S10, an eleventh switch S11 and a twelfth switch S12; a first end of the fifth capacitor Ce is connected with the output end of the first operational amplifier U1 through an eighth switch S8, one end of a ninth switch S9 is connected with the first end of the fifth capacitor Ce, and the other end of the ninth switch S9 is grounded; a negative input end of the second operational amplifier U2 is connected to a first end of the fourth capacitor Cd and a second end of the fifth capacitor Ce, a positive input end of the second operational amplifier is grounded, and an output end of the second operational amplifier U2 outputs a second output signal Voutp; a tenth switch S10 is connected between the negative input end of the second operational amplifier U2 and the output end of the second operational amplifier U2, a twelfth switch S12 is connected between the second end of the fourth capacitor Cd and the output end of the second operational amplifier U2, one end of the twelfth switch S12 is connected with the second end of the fourth capacitor Cd, and the other end of the twelfth switch S12 is grounded.

As a preferred signal, the fourth capacitance Cd is equal to the capacitance value of the fifth capacitance Ce.

The invention discloses a control method of a C/V conversion system, which is based on the C/V conversion system applied to an MEMS acceleration sensor and comprises a first time sequence signal and a second time sequence signal for controlling the on-off of different switches; the first timing signal controls the on and off of a first switch S1, a fourth switch S4, a fifth switch S5, a sixth switch S6, a ninth switch S9, a tenth switch S10 and an eleventh switch S11; the second timing signal controls the on and off of the second switch S2, the third switch S3, the seventh switch S7, the eighth switch S8 and the twelfth switch S12. When the switch controlled by the first timing signal is turned on, the switch controlled by the second timing signal is turned off. The first timing signal may be a square waveform.

FIG. 2 is a timing chart of the C/V conversion system of the present invention. Wherein S1/S4/S5/S6/S9/S10/S11 and S2/S3/S7/S8/S12 respectively represent timing signals acting on the corresponding switches; voutp and Voutn respectively represent signals output by the positive end and the negative end.

When the fourth capacitance Cd is equal to the capacitance value of the fifth capacitance Ce,

first output signal

Second output signal

The working principle of the invention is as follows: in the C/V conversion system of the MEMS acceleration sensor in fig. 1, the capacitance variation of Ct and Cb is used to represent the magnitude of the acceleration, and the function of the circuit is to convert the variation into a differential analog signal and output the differential analog signal. Cd. Ce, Cf represent the capacitance in the readout circuit, which can be adjusted according to the voltage amplitude requirement of the output signal. Referring to the timing diagram of the switching circuit, the switches S1, S4, S5, S6, S9, S10 and S11 share the same clock signal, the switches S2, S3, S7, S8 and S12 share another clock signal, and the two clock signals are complementary, that is, the switches S1, S4, S5, S6, S9, S10, S11 and the switches S2, S3, S7, S8 and S12 are alternately turned on (assuming that the switches S1, S4, S5, S6, S9, S10 and S11 are turned off and the switches S2, S3, S7, S8 and S12 are turned on when in the high state).

When the switches S1, S4, S5, S6, S9, S10, and S11 are turned on, the switches S2, S3, S7, S8, and S12 are turned off, and at this time, the high input impedance of the voltage-type operational amplifiers Amp1 and Amp2 is obtained, the voltage difference between the two ends of the capacitors Cf and Ce is 0, and the amount of stored charge is 0. Since the upper plate voltage of the capacitor Ct is Vrp, the lower plate voltage of the capacitor Cb is Vrn, and the upper plate voltage of the contact between Ct and Cb is 0, charges of values Vrp · Ct and Vrn · Cb are stored in the capacitors, respectively. At this time, output signals Voutn and Voutp of Amp1 and Amp2 in the conversion circuit are both 0.

When the switches S1, S4, S5, S6, S9, S10, and S11 are turned off, the switches S2, S3, S7, S8, and S12 are turned on, the upper plate voltage of the capacitor Ct is Vrn, the lower plate voltage of the capacitor Cb is Vrp, and the upper plate voltage of the contact between Ct and Cb is still 0. According to the conservation of charge, the following results are obtained: the charge change on the capacitances Ct and Cb will be reflected on the capacitance Cf. Similarly, since the plate voltage of the capacitor Ce connected to Cd is also 0, the change of Voutn will be reflected at Voutp and in a complementary manner. In conjunction with the conversion circuit diagram and timing, the output signal can be derived as:

the output signals Voutn and Voutp alternate with time sequence as shown in the timing diagram of the above conversion circuit.

The switch device in the invention can be realized by a single N-type or P-type MOSFET tube, or can be formed by combining N-type and P-type MOSFETs.

In the implementation of Amp (operational amplifier) in the circuit of the invention, the amplifier stage number can be one stage, two stages or higher cascade, and the structure is not limited to sleeve type or folding type cascade and simple differential pair.

The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.