Accelerometer, detection method, and program

Abstract

This invention provides an acceleration sensor, a detection method, and a program capable of accurately detecting circuit noise. [Solution] The acceleration sensor A1 comprises a sensor unit 1, a power supply circuit 2, and a detection circuit 3. The detection circuit 3 includes a first selector 6 that outputs one of the first charge signal S3 and the second charge signal S4 as a first select signal S10, a second selector 7 that outputs the remaining signal of the first charge signal S3 and the second charge signal S4 as a second select signal S20, an operation switching unit 30 that switches the operating state of the first selector 6 and the second selector 7, a CV conversion circuit 32 that outputs a first voltage signal S12 and a second voltage signal S22, a third selector 15 that alternately selects one of the voltage signals of the first voltage signal S12 and the second voltage signal S22 according to the pulse signal S0 and outputs the voltage signal as a third select signal S30, and a filter 34 that removes the high-frequency component of the third select signal S30.

Description

Technical Field

[0001] The present disclosure generally relates to an acceleration sensor, a detection method, and a program, and more particularly to an acceleration sensor including a sensor unit, a detection method of the acceleration sensor, and a program of the detection method.

Background Art

[0002] An acceleration detection device (acceleration sensor) described in Patent Document 1 will be exemplified. The acceleration detection device described in Patent Document 1 includes a capacitance detection circuit and an acceleration sensor (sensor unit). The acceleration sensor is a capacitance-type sensor element.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the acceleration detection device described in Patent Document 1, for example, when affected by vibrations in the inspection environment (external disturbances), it is difficult to accurately detect circuit noise caused by an electric circuit (for example, a capacitance detection circuit, etc.).

[0005] An object of the present disclosure is to provide an acceleration sensor, a detection method, and a program capable of accurately detecting circuit noise.

Means for Solving the Problems

[0006] An acceleration sensor according to one aspect of the present disclosure comprises a sensor unit, a power supply circuit, and a detection circuit. The sensor unit is subjected to acceleration. The power supply circuit is electrically connected to the sensor unit. The detection circuit is electrically connected to the sensor unit and detects the acceleration. The power supply circuit includes a signal generator, a non-inverting amplifier circuit, and an inverting amplifier circuit. The signal generator outputs a pulse signal. The non-inverting amplifier circuit amplifies the pulse signal and outputs a non-inverting amplified signal. The inverting amplifier circuit inverts and amplifies the pulse signal and outputs an inverting amplified signal. The sensor unit includes a first input terminal, a second input terminal, a first output terminal, a second output terminal, a first capacitance unit, a second capacitance unit, a third capacitance unit, and a fourth capacitance unit. The first input terminal receives the input of the non-inverting amplified signal. The second input terminal receives the input of the inverting amplified signal. The first output terminal outputs a first charge signal corresponding to the acceleration. The second output terminal outputs a second charge signal that corresponds to the acceleration and is in opposite phase to the first charge signal. The first capacitance unit is provided in the circuit between the first input terminal and the first output terminal. The second capacitance unit is provided in the circuit between the first output terminal and the second input terminal. The third capacitance unit is provided in the circuit between the first input terminal and the second output terminal. The fourth capacitance unit is provided in the circuit between the second output terminal and the second input terminal. The detection circuit includes a first selector, a second selector, an operation switching unit, a CV conversion circuit, a third selector, and a filter. The first selector selects one of the first charge signal and the second charge signal and outputs the one signal as a first select signal. The second selector selects the remaining signal from the first charge signal and the second charge signal and outputs the remaining signal as a second select signal. The operation switching unit switches the operating state of the first selector and the second selector. The CV conversion circuit receives the inputs of the first select signal and the second select signal and outputs a first voltage signal and a second voltage signal. The first voltage signal is the signal obtained by subtracting the second select signal from the first select signal. The second voltage signal is the signal obtained by subtracting the first select signal from the second select signal.The third selector alternately selects either the first voltage signal or the second voltage signal in response to the pulse signal and outputs the voltage signal as the third select signal. The filter removes the high-frequency components of the third select signal.

[0007] A detection method according to one aspect of the present disclosure includes an operation step, a signal output step, an amplification step, a charge selection step, a voltage selection step, an output step, and a rejection step. In the operation step, the control circuit is operated in either an acceleration detection mode for detecting acceleration or a noise detection mode for detecting circuit noise. In the signal output step, a pulse signal is output. In the amplification step, a non-inverting amplified signal obtained by amplifying the pulse signal and an inverting amplified signal obtained by inverting the pulse signal are output to the sensor unit. In the charge selection step, one of the first charge signal and the second charge signal from the sensor unit is output as a first select signal, and the remaining signal of the first charge signal and the second charge signal is output as a second select signal. In the voltage selection step, a first voltage signal is output, which is the signal obtained by subtracting the second select signal from the first select signal, and a second voltage signal is output, which is the signal obtained by subtracting the first select signal from the second select signal. In the output step, one of the voltage signals, the first voltage signal or the second voltage signal, is alternately selected according to the pulse signal, and the voltage signal is output as the third select signal. In the removal step, the high-frequency components of the third select signal are removed. In the charge selection step, if the control mode is the acceleration detection mode, the first charge signal is output as the first select signal, and the second charge signal is output as the second select signal. In the charge selection step, if the control mode is the noise detection mode, the first output state and the second output state are alternately switched according to the pulse signal. The first output state is a state in which the first charge signal is output as the first select signal, and the second charge signal is output as the second select signal. The second output state is a state in which the second charge signal is output as the first select signal, and the first charge signal is output as the second select signal.

[0008] A program according to one aspect of this disclosure causes one or more processors to execute the detection method. [Effects of the Invention]

[0009] According to one aspect of this disclosure, circuit noise can be accurately detected. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a circuit diagram of an acceleration sensor according to an embodiment. [Figure 2] Figure 2 is a timing chart showing the operation of the acceleration sensor in acceleration detection mode. [Figure 3] Figure 3 is a graph showing the frequency characteristics of the acceleration sensor mentioned above. [Figure 4] Figure 4 is a schematic waveform diagram showing the spectrum waveform of the signal output from the sensor unit of the acceleration sensor mentioned above, in acceleration detection mode and noise detection mode. [Figure 5] Figure 5 is a schematic waveform diagram showing the spectrum waveform of the signal output from the CV conversion circuit in acceleration detection mode for the acceleration sensor mentioned above. [Figure 6] Figure 6 is a schematic waveform diagram showing the spectrum waveform of the signal input to the filter in acceleration detection mode for the acceleration sensor mentioned above. [Figure 7] Figure 7 is a schematic waveform diagram showing the spectrum waveform of the signal output from the filter in acceleration detection mode for the acceleration sensor mentioned above. [Figure 8] Figure 8 is a timing chart showing the operation of the acceleration sensor in noise detection mode. [Figure 9] Figure 9 is a schematic waveform diagram showing the spectrum waveform of the signal input to the CV conversion circuit in noise detection mode for the acceleration sensor mentioned above. [Figure 10] Figure 10 is a schematic waveform diagram showing the spectrum waveform of the signal output from the CV conversion circuit in noise detection mode for the acceleration sensor mentioned above. [Figure 11]FIG. 11 is a waveform diagram schematically showing a spectrum waveform of a signal input to a filter in a noise detection mode with respect to the acceleration sensor described above. [Figure 12] FIG. 12 is a waveform diagram schematically showing a spectrum waveform of a signal output from a filter in a noise detection mode with respect to the acceleration sensor described above.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the acceleration sensor according to the embodiment will be described with reference to the drawings. The configuration described in the following embodiments is merely an example of the present disclosure. The present disclosure is not limited to the following embodiments, and various modifications can be made according to the design and the like as long as the effects of the present disclosure can be achieved.

[0012] Hereinafter, the acceleration sensor according to the embodiment will be described with reference to FIGS. 1 to 12.

[0013] (1) Acceleration Sensor The acceleration sensor A1 according to the embodiment includes, for example, as shown in FIG. 1, a sensor unit 1, a power supply circuit 2, a detection circuit 3, a control circuit 4, and a signal output terminal 5. The acceleration sensor A1 detects acceleration. For example, as shown in FIG. 3, the acceleration sensor A1 detects acceleration in a low frequency region (for example, a range of 0 Hz or more and 1 kHz or less).

[0014] (1.1) Sensor Unit Acceleration is applied to the sensor unit 1 shown in FIG. 1. The sensor unit 1 is a capacitance type, and has, for example, a first input terminal 11, a second input terminal 12, a first output terminal 13, a second output terminal 14, a first capacitance unit C1, a second capacitance unit C2, a third capacitance unit C3, and a fourth capacitance unit C4.

[0015] The first input terminal 11 is electrically connected to the power supply circuit 2 and receives the input of the non-inverting amplification signal S1 described later. The second input terminal 12 is electrically connected to the power supply circuit 2 and receives the input of the inverting amplification signal S2 described later.

[0016] The first output terminal 13 is electrically connected to the detection circuit 3 and outputs a first charge signal S3 to the detection circuit 3. The first charge signal S3 is a signal corresponding to the acceleration applied to the sensor unit 1. More specifically, the first charge signal S3 is a signal corresponding to the increase and decrease of the capacitance of each of the first capacitance unit C1 and the second capacitance unit C2 according to the acceleration applied to the sensor unit 1.

[0017] The second output terminal 14 is electrically connected to the detection circuit 3 and outputs a second charge signal S4 to the detection circuit 3. The second charge signal S4 corresponds to the acceleration applied to the sensor unit 1 and is a signal with an opposite phase to the first charge signal S3. More specifically, the second charge signal S4 corresponds to the increase and decrease of the capacitance of each of the third capacitance unit C3 and the fourth capacitance unit C4 according to the acceleration applied to the sensor unit 1 and is a signal with an opposite phase to the first charge signal S3.

[0018] The first capacitance unit C1 is provided in the circuit between the first input terminal 11 and the first output terminal 13. The second capacitance unit C2 is provided in the circuit between the first output terminal 13 and the second input terminal 12. The third capacitance unit C3 is provided in the circuit between the first input terminal 11 and the second output terminal 14. The fourth capacitance unit C4 is provided in the circuit between the second output terminal 14 and the second input terminal 12. That is, the sensor unit 1 is configured in a full-bridge type.

[0019] The first capacitance unit C1 and the fourth capacitance unit C4 have the same polarity indicating the increase and decrease of the capacitance of each of the first capacitance unit C1 and the fourth capacitance unit C4. For example, when the capacitance of the first capacitance unit C1 increases, the capacitance of the fourth capacitance unit C4 also increases. The directions of the arrows shown for each of the first capacitance unit C1 and the fourth capacitance unit C4 in FIG. 1 represent that the polarities indicating the increase and decrease of the capacitance are the same.

[0020] The second capacitance section C2 and the third capacitance section C3 have the same polarity indicating the increase or decrease in their respective capacitances. For example, if the capacitance of the second capacitance section C2 decreases, the capacitance of the third capacitance section C3 also decreases. Note that the direction of the arrows shown for the second capacitance section C2 and the third capacitance section C3 in Figure 1 indicates that they have the same polarity indicating the increase or decrease in capacitance.

[0021] The first capacitance section C1 and the second capacitance section C2 have opposite polarities, indicating increases and decreases in their respective capacitances. For example, when the capacitance of the first capacitance section C1 increases, the capacitance of the second capacitance section C2 decreases.

[0022] (1.2) Power supply circuit The power supply circuit 2 is electrically connected to the sensor unit 1. The power supply circuit 2 includes, for example, a signal generator 21, a non-inverting amplifier circuit 22, and an inverting amplifier circuit 23.

[0023] The signal generator 21 outputs a pulse signal S0. The pulse signal S0 is a signal in which a period of low signal level (low-level period) T1 and a period of high signal level (high-level period) T2 alternate, as shown in Figure 2, for example. The high-level period T2 is, for example, the same length as the low-level period T1.

[0024] The signal generator 21 shown in Figure 1 is electrically connected to the input terminal of the non-inverting amplifier circuit 22. The signal generator 21 is also electrically connected to the input terminal of the inverting amplifier circuit 23.

[0025] The non-inverting amplifier circuit 22 amplifies the pulse signal S0 and outputs the non-inverting amplified signal S1 to the sensor unit 1. The output terminal of the non-inverting amplifier circuit 22 is electrically connected to the first input terminal 11 of the sensor unit 1.

[0026] The inverting amplifier circuit 23 inverts and amplifies the pulse signal S0 and outputs the inverted amplified signal S2 to the sensor unit 1. The output terminal of the inverting amplifier circuit 23 is electrically connected to the second input terminal 12 of the sensor unit 1.

[0027] Figure 2 illustrates the operation when acceleration is applied to the sensor unit 1 in a direction such that the capacitance of the first capacitance unit C1 becomes greater than the capacitance of the second capacitance unit C2, and the capacitance of the fourth capacitance unit C4 becomes greater than the capacitance of the third capacitance unit C3.

[0028] Furthermore, the voltage value Vp of the non-inverting amplified signal S1 in Figure 2 represents the maximum value (maximum voltage) of the signal level of the non-inverting amplified signal S1. The voltage value Vp of the inverting amplified signal S2 in Figure 2 represents the maximum value (maximum voltage) of the signal level of the inverting amplified signal S2. In other words, the maximum value of the signal level of the inverting amplified signal S2 is the same as the maximum value of the signal level of the non-inverting amplified signal S1.

[0029] The power supply circuit 2 shown in Figure 1 modulates the acceleration signal component (hereinafter referred to as "acceleration signal component") M1 applied to the sensor unit 1 by outputting a non-inverting amplified signal S1 and an inverting amplified signal S2 to the sensor unit 1 (see Figure 4). In other words, the power supply circuit 2 modulates the acceleration signal component M1 of the sensor unit 1 by applying a rectangular wave alternating voltage (AC voltage) to the sensor unit 1.

[0030] In Figure 4, frequency f1 is the modulation frequency of the acceleration signal component M1, and corresponds to the frequencies (driving frequencies) of the non-inverting amplified signal S1 and the inverting amplified signal S2, respectively. Frequency f1 is higher than 1 kHz (for example, 100 kHz). In Figure 4, noise signal component N1 is noise (for example, white noise) caused by the operation of the power supply circuit 2. In Figure 4, frequency f0 represents a frequency lower than frequency f1.

[0031] (1.3) Detection circuit The detection circuit 3 shown in Figure 1 detects the acceleration applied to the sensor unit 1 and outputs the detected signal (hereinafter referred to as the "detection signal") S40 to the signal output terminal 5. The detection circuit 3 is electrically connected to the sensor unit 1. The detection circuit 3 is also electrically connected to the signal output terminal 5.

[0032] The detection circuit 3 includes, for example, a first synchronous rectifier circuit 31, an operation switching unit 30, a CV conversion circuit 32, a second synchronous rectifier circuit 33, and a filter 34.

[0033] The first synchronous rectifier circuit 31 includes, for example, a first selector 6 and a second selector 7.

[0034] The first selector 6 selects one of the charge signals (for example, the first charge signal S3) from the first charge signal S3 and the second charge signal S4, and outputs the selected charge signal as the first select signal S10 to the CV conversion circuit 32.

[0035] The first input terminal of the first selector 6 is electrically connected to the first output terminal 13 of the sensor unit 1. The second input terminal of the first selector 6 is electrically connected to the second output terminal 14 of the sensor unit 1. The control terminal of the first selector 6 is electrically connected to the operation switching unit 30. The output terminal of the first selector 6 is electrically connected to the CV conversion circuit 32.

[0036] The second selector 7 selects the remaining charge signal (for example, the second charge signal S4) from the first charge signal S3 and the second charge signal S4, and outputs the selected remaining charge signal as the second select signal S20 to the CV conversion circuit 32.

[0037] The first input terminal of the second selector 7 is electrically connected to the second output terminal 14 of the sensor unit 1. The second input terminal of the second selector 7 is electrically connected to the first output terminal 13 of the sensor unit 1. The control terminal of the second selector 7 is electrically connected to the operation switching unit 30. The output terminal of the second selector 7 is electrically connected to the CV conversion circuit 32.

[0038] The operation switching unit 30 switches the operating state of the first selector 6 and the second selector 7. More specifically, the operation switching unit 30 switches the operating state of the first selector 6 and the second selector 7 so that they operate in either the first operating mode or the second operating mode.

[0039] The first operating mode is an operating mode in which the system alternately switches between two cases in accordance with the pulse signal S0: when the first selector 6 selects the first charge signal S3 as the first select signal S10 and the second selector 7 selects the second charge signal S4 as the second select signal S20 (hereinafter referred to as "the first case") and when the first selector 6 selects the second charge signal S4 as the first select signal S10 and the second selector 7 selects the first charge signal S3 as the second select signal S20 (hereinafter referred to as "the second case").

[0040] Furthermore, "the first selector 6 and the second selector 7 alternately switch between the first and second cases according to the pulse signal S0" means, for example, that at the rising edge of the pulse signal S0 (times t2 and t6 in the example in Figure 2), the first selector 6 and the second selector 7 start operating in the first case, and at the falling edge of the pulse signal S0 (times t4 and t8 in the example in Figure 2), the first selector 6 and the second selector 7 start operating in the second case.

[0041] The second operating mode is one in which the first selector 6 selects the first charge signal S3 as the first select signal S10, and the second selector 7 selects the second charge signal S4 as the second select signal S20.

[0042] The operation switching unit 30 is, for example, an AND circuit. The first input terminal of the operation switching unit 30 is electrically connected to the signal generator 21 of the power supply circuit 2. The second input terminal of the operation switching unit 30 is electrically connected to the control circuit 4. The output terminal of the operation switching unit 30 is electrically connected to the control terminal of the first selector 6. Furthermore, the output terminal of the operation switching unit 30 is electrically connected to the control terminal of the second selector 7.

[0043] The CV conversion circuit 32 is a conversion circuit that converts the increase or decrease (change) in the capacitance of the sensor unit 1 (specifically, the capacitances of the first capacitance unit C1, the second capacitance unit C2, the third capacitance unit C3, and the fourth capacitance unit C4) into a change in voltage. The CV conversion circuit 32 accepts the input of the first select signal S10 and the second select signal S20. The CV conversion circuit 32 also outputs the first voltage signal S12 and the second voltage signal S22, which will be described later, to the second synchronous rectifier circuit 33.

[0044] The CV conversion circuit 32 includes, for example, a first integrator 16, a second integrator 17, and a fully differential amplifier 10.

[0045] The first integrator 16 is configured to output a signal S11 (hereinafter referred to as the "first integrated signal") obtained by integrating the first select signal S10 (see Figures 1 and 2). The first integrator 16 includes, for example, an operational amplifier 8, a capacitor C5, and a switching element SW1.

[0046] The inverting input terminal of the operational amplifier 8 is electrically connected to the output terminal of the first selector 6. The non-inverting input terminal of the operational amplifier 8 is electrically connected to the power supply unit Vr1. The output terminal of the operational amplifier 8 is electrically connected to the non-inverting input terminal of the fully differential amplifier 10. The power supply unit Vr1 is a power supply that outputs, for example, a voltage value Vref (see Figure 2). The voltage value Vref is, for example, half the maximum voltage value Vp of the non-inverting amplified signal S1.

[0047] Note that the power supply unit Vr1 is not limited to a power supply that outputs a voltage value Vref, but may also be, for example, a power supply circuit that outputs a voltage value Vref (hereinafter referred to as the "reference power supply circuit"). The reference power supply circuit may also be included in the power supply circuit 2. In this case, the non-inverting input terminal of the operational amplifier 8 is electrically connected to the power supply circuit 2.

[0048] Capacitor C5 is located in the circuit between the inverting input terminal and the output terminal of the operational amplifier 8. More specifically, the first terminal of capacitor C5 is electrically connected to the inverting input terminal of the operational amplifier 8. The second terminal of capacitor C5 is electrically connected to the output terminal of the operational amplifier 8.

[0049] The switching element SW1 is electrically connected in parallel with the capacitor C5. The switching element SW1 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor). More specifically, the switching element SW1 is, for example, an n-channel MOSFET. The n-channel MOSFET is, for example, a normally-off Si-based MOSFET.

[0050] The first main terminal of the switching element SW1 is electrically connected to the first terminal of the capacitor C5. The second main terminal of the switching element SW1 is electrically connected to the second terminal of the capacitor C5. The control terminal of the switching element SW1 is electrically connected to the control circuit 4.

[0051] The voltage value V1 of the first integrated signal S11 in Figure 2 is expressed by the following equation (1), where C1 is the capacitance of the first capacitance section C1, C2 is the capacitance of the second capacitance section C2, CF is the capacitance of capacitor C5, and Vp is the maximum voltage value Vp of the non-inverting amplified signal S1.

[0052]

number

[0053] The second integrator 17 is configured to output a signal S21 (hereinafter referred to as the "second integrated signal") obtained by integrating the second select signal S20 (see Figures 1 and 2). The second integrator 17 includes, for example, an operational amplifier 9, a capacitor C6, and a switching element SW2. The capacitance of capacitor C6 is, for example, the same as the capacitance of capacitor C5.

[0054] Furthermore, the statement "the capacitance of capacitor C6 is the same as the capacitance of capacitor C5" does not only mean that the capacitance of capacitor C6 is exactly the same as the capacitance of capacitor C5, but also includes cases where, for example, the capacitances of capacitors C5 and C6 have an error of ±20% from their nominal values.

[0055] The inverting input terminal of the operational amplifier 9 is electrically connected to the output terminal of the second selector 7. The non-inverting input terminal of the operational amplifier 9 is electrically connected to the power supply unit Vr1 described above. The output terminal of the operational amplifier 9 is electrically connected to the inverting input terminal of the fully differential amplifier 10. The non-inverting input terminal of the operational amplifier 9 may also be electrically connected to, for example, the reference power supply circuit, similar to the operational amplifier 8.

[0056] Capacitor C6 is located in the circuit between the inverting input terminal and the output terminal of the operational amplifier 9. More specifically, the first terminal of capacitor C6 is electrically connected to the inverting input terminal of the operational amplifier 9. The second terminal of capacitor C6 is electrically connected to the output terminal of the operational amplifier 9.

[0057] Switching element SW2 is electrically connected in parallel with capacitor C6. Switching element SW2 is, for example, a MOSFET. More specifically, switching element SW1 is, for example, an n-channel MOSFET.

[0058] The first main terminal of the switching element SW2 is electrically connected to the first terminal of the capacitor C6. The second main terminal of the switching element SW2 is electrically connected to the second terminal of the capacitor C6. The control terminal of the switching element SW2 is electrically connected to the control circuit 4.

[0059] The voltage value V2 of the second integrated signal S21 in Figure 2 is expressed by the following equation (2), where C3 is the capacitance of the third capacitance section C3, C4 is the capacitance of the fourth capacitance section C4, CF is the capacitance of capacitor C6, and Vp is the maximum voltage value Vp of the non-inverting amplified signal S1.

[0060]

number

[0061] The fully differential amplifier 10 accepts the inputs of the first integral signal S11 and the second integral signal S21. The fully differential amplifier 10 also outputs the first voltage signal S12 and the second voltage signal S22 to the second synchronous rectifier circuit 33. More specifically, the fully differential amplifier 10 amplifies the difference (difference voltage) between the first integral signal S11 and the second integral signal S21 and outputs the differential signal (first voltage signal S12 and second voltage signal S22) to the second synchronous rectifier circuit 33.

[0062] The first voltage signal S12 is the signal obtained by subtracting the second integral signal S21 from the first integral signal S11. In other words, the first voltage signal S12 is the signal obtained by subtracting the second select signal S20 from the first select signal S10. The second voltage signal S22 is the signal obtained by subtracting the first integral signal S11 from the second integral signal S21. In other words, the second voltage signal S22 is the signal obtained by subtracting the first select signal S10 from the second select signal S20.

[0063] The non-inverting input terminal of the fully differential amplifier 10 is electrically connected to the output terminal of the operational amplifier 8 of the first integrator 16. The inverting input terminal of the fully differential amplifier 10 is electrically connected to the output terminal of the operational amplifier 9 of the second integrator 17. The common-mode voltage input terminal of the fully differential amplifier 10 is electrically connected to the power supply unit Vr1 described above. The inverting output terminal of the fully differential amplifier 10 is electrically connected to the second synchronous rectifier circuit 33 and outputs the second voltage signal S22 to the second synchronous rectifier circuit 33. The non-inverting output terminal of the fully differential amplifier 10 is electrically connected to the second synchronous rectifier circuit 33 and outputs the first voltage signal S12 to the second synchronous rectifier circuit 33.

[0064] The voltage value Vref input to the common-mode voltage input terminal of the fully differential amplifier 10 corresponds to the common-mode voltage value. Furthermore, the common-mode voltage input terminal of the fully differential amplifier 10 may be electrically connected to, for example, a reference power supply circuit, similar to the operational amplifier 8.

[0065] The second synchronous rectifier circuit 33 includes, for example, a third selector 15. The third selector 15 alternately selects either the first voltage signal S12 or the second voltage signal S22 in response to the pulse signal S0, and outputs the selected voltage signal as the third select signal S30 (see Figures 1 and 2).

[0066] Furthermore, the statement "the third selector 15 alternately selects either the first voltage signal S12 or the second voltage signal S22 in response to the pulse signal S0" means, for example, that the third selector 15 selects the first voltage signal S12 at the rising edge of the pulse signal S0 (times t2 and t6 in the example in Figure 2) and selects the second voltage signal S22 at the falling edge of the pulse signal S0 (times t4 and t8 in the example in Figure 2).

[0067] The first input terminal of the third selector 15 is electrically connected to the inverting output terminal of the fully differential amplifier 10. The second input terminal of the third selector 15 is electrically connected to the non-inverting output terminal of the fully differential amplifier 10. The control terminal of the third selector 15 is electrically connected to the signal generator 21 of the power supply circuit 2. The output terminal of the third selector 15 is electrically connected to the filter 34.

[0068] The voltage value V3 of the third select signal S30 in Figure 2 is expressed by the following equation (3), where C1 is the capacitance of the first capacitance section C1, C2 is the capacitance of the second capacitance section C2, C3 is the capacitance of the third capacitance section C3, C4 is the capacitance of the fourth capacitance section C4, CF is the capacitance of capacitors C5 and C6 respectively, Vp is the maximum voltage value Vp of the non-inverting amplification signal S1, and Ga is the gain of the fully differential amplifier 10.

[0069]

number

[0070] Filter 34 removes the high-frequency components of the third select signal S30. Filter 34 is, for example, a low-pass filter. Filter 34 also outputs the signal from which the high-frequency components of the third select signal S30 have been removed as a detection signal S40 (see Figures 1 and 2) to the signal output terminal 5.

[0071] The input terminal of filter 34 is electrically connected to the output terminal of the third selector 15. The output terminal of filter 34 is electrically connected to the signal output terminal 5.

[0072] (1.4) Control circuits The control circuit 4 controls, for example, the operation switching unit 30. In other words, the control circuit 4 outputs, for example, a first control signal to the operation switching unit 30. The first control signal is a signal that causes the operation switching unit 30 to switch the operating state of the first selector 6 and the second selector 7. The first control signal is, for example, a pulse signal.

[0073] Here, the operation switching unit 30 switches the operating state of the first selector 6 and the second selector 7 so that they operate in either the first operating mode or the second operating mode, based on, for example, the first control signal from the control circuit 4.

[0074] For example, the operation switching unit 30 switches the operating state of the first selector 6 and the second selector 7 so that they operate in the first operating mode when the signal level of the first control signal is high. Also, the operation switching unit 30 switches the operating state of the first selector 6 and the second selector 7 so that they operate in the second operating mode when the signal level of the first control signal is low.

[0075] The control circuit 4 is implemented, for example, by a computer system having one or more processors and one or more memories. In other words, the functions of the control circuit 4 are realized by one or more processors executing a program stored in memory. The program may be pre-stored in memory, provided via a telecommunication line such as the Internet, or provided on a non-temporary recording medium such as a memory card.

[0076] The control circuit 4 has, for example, an acceleration detection mode for detecting acceleration and a noise detection mode for detecting noise in an electrical circuit (for example, the detection circuit 3, etc.) (hereinafter referred to as "circuit noise").

[0077] When the control mode is acceleration detection mode, the control circuit 4 sets the signal level of the first control signal to a low level and controls the operation switching unit 30 so that the first selector 6 and the second selector 7 operate in the second operation mode. On the other hand, when the control mode is noise detection mode, the control circuit 4 sets the signal level of the first control signal to a high level and controls the operation switching unit 30 so that the first selector 6 and the second selector 7 operate in the first operation mode.

[0078] Furthermore, the control circuit 4 controls, for example, the switching element SW1 of the first integrator 16. In other words, the control circuit 4 outputs, for example, a second control signal S6 (see Figure 2) to the switching element SW1. The second control signal S6 is a signal for controlling the switching element SW1. More specifically, the second control signal S6 is a signal for switching the switching element SW1 to either an on state or an off state. The second control signal S6 is, for example, a pulse signal.

[0079] The control circuit 4 switches the signal level of the second control signal S6 from a low level to a high level at a point in time (times t1 and t5 in the example of Figure 2) prior to the rising edge of the pulse signal S0 (times t2 and t6 in the example of Figure 2). The control circuit 4 switches the signal level of the second control signal S6 from a high level to a low level at the rising edge of the pulse signal S0.

[0080] Furthermore, the control circuit 4 switches the signal level of the second control signal S6 from a low level to a high level at a point earlier than the falling edge of the pulse signal S0 (in the example of Figure 2, points t4 and t8) (in the example of Figure 2, points t3 and t7). The control circuit 4 switches the signal level of the second control signal S6 from a high level to a low level at the falling edge of the pulse signal S0.

[0081] In other words, the control circuit 4 controls the switching element SW1 of the first integrator 16 in response to the pulse signal S0. This allows the first integrator 16 to discharge, for example, the charge stored in the capacitor C5. Therefore, the integration accuracy of the first integrator 16 can be improved in the acceleration sensor A1.

[0082] Furthermore, the control circuit 4 controls, for example, the switching element SW2 of the second integrator 17. In other words, the control circuit 4 outputs, for example, a third control signal S7 (see Figure 2) to the switching element SW2. The third control signal S7 is a signal for controlling the switching element SW2. More specifically, the third control signal S7 is a signal for switching the switching element SW2 to either the on state or the off state. The third control signal S7 is, for example, a pulse signal. Note that the operation of the control circuit 4 to control the switching element SW2 is the same as the operation of the control circuit 4 to control the switching element SW1, only the target switching element is different, so the explanation is omitted.

[0083] The control circuit 4 controls the switching element SW2 of the second integrator 17 in response to the pulse signal S0. This allows the second integrator 17 to discharge, for example, the charge stored in the capacitor C6. Therefore, the integration accuracy of the second integrator 17 can be improved in the acceleration sensor A1.

[0084] In Figure 2, period T3 represents the high-level periods for the second control signal S6 and the third control signal S7, respectively. Period T3 is also the discharge period during which the charge accumulated in capacitors C5 and C6 is discharged.

[0085] (2) Operation of the accelerometer The operation of acceleration sensor A1 will be explained below based on Figure 1. First, the operation of acceleration sensor A1 when its control mode is acceleration detection mode will be explained, followed by the operation of acceleration sensor A1 when its control mode is noise detection mode.

[0086] (2.1) Acceleration detection mode The power supply circuit 2 outputs a non-inverting amplified signal S1 and an inverting amplified signal S2 to the sensor unit 1. In the sensor unit 1, a rectangular wave alternating voltage is applied to a pair of input terminals (first input terminal 11 and second input terminal 12), so that the acceleration signal component (acceleration signal component) M1 applied to the sensor unit 1 is modulated (see Figure 4).

[0087] When the control mode is acceleration detection mode, the control circuit 4 controls the operation switching unit 30 so that the first selector 6 and the second selector 7 operate in the second operation mode.

[0088] The first selector 6 outputs the first charge signal S3 as the first select signal S10 to the CV conversion circuit 32. The second selector 7 outputs the second charge signal S4 as the second select signal S20 to the CV conversion circuit 32.

[0089] The CV conversion circuit 32 converts the first select signal S10 and the second select signal S20 into a first voltage signal S12 and a second voltage signal S22, and outputs the first voltage signal S12 and the second voltage signal S22 to the third selector 15. At this time, in the acceleration sensor A1, noise signal component N1 in Figure 4 is superimposed with noise caused by the operation of the CV conversion circuit 32 (e.g., 1 / f noise) and noise caused by the operation of the detection circuit 3 (e.g., white noise), so in addition to the acceleration signal component M1, a noise signal component N2 is generated (see Figure 5). Note that, as shown in Figure 5, the noise signal component N2 has a peak in the noise caused by the operation of the CV conversion circuit 32 at frequency f0.

[0090] The third selector 15 alternately selects either the first voltage signal S12 or the second voltage signal S22 in response to the pulse signal S0, and outputs the selected voltage signal as the third select signal S30 (see Figure 2). In other words, the third selector 15 remodulates (demodulates) the acceleration signal component M1 and modulates the noise caused by the operation of the CV conversion circuit 32 (see Figure 6). At this time, as shown in Figure 6, the acceleration sensor A1 experiences a peak in the acceleration signal component M1 at frequency f0. Also, the acceleration sensor A1 experiences a peak in noise caused by the operation of the CV conversion circuit 32 at frequency f1.

[0091] Filter 34 removes the high-frequency components of the third select signal S30. More specifically, filter 34 removes the high-frequency region of the noise signal component N2 (particularly noise caused by the operation of the CV conversion circuit 32) at a cutoff frequency fc1 (see Figure 7). As a result, the acceleration sensor A1 outputs a detection signal S40 containing the acceleration signal component M1 and the noise signal component N3 from the signal output terminal 5 (see Figures 2 and 7).

[0092] Note that the noise signal component N3 shown in Figure 7 is the noise signal component obtained by removing the high-frequency region of the noise signal component N2 shown in Figure 6. Also, the cutoff frequency fc1 is a frequency higher than frequency f0 and a frequency much lower than frequency f1.

[0093] (2.2) Noise detection mode The power supply circuit 2 outputs a non-inverting amplified signal S1 and an inverting amplified signal S2 to the sensor unit 1, similar to when the control mode of the control circuit 4 is acceleration detection mode. In the sensor unit 1, a rectangular wave alternating voltage is applied to a pair of input terminals (first input terminal 11 and second input terminal 12), so that the acceleration signal component (acceleration signal component) M1 applied to the sensor unit 1 is modulated (see Figure 4).

[0094] When the control mode is noise detection mode, the control circuit 4 controls the operation switching unit 30 so that the first selector 6 and the second selector 7 operate in the first operation mode.

[0095] The first selector 6 and the second selector 7 alternately switch between the first and second cases according to the pulse signal S0. For example, as shown in Figure 8, at the rising edge of the pulse signal S0 (times t10 and t14 in the example in Figure 8), the first selector 6 selects the first charge signal S3 as the first select signal S10, and the second selector 7 selects the second charge signal S4 as the second select signal S20. Also, at the falling edge of the pulse signal S0 (times t12 and t16 in the example in Figure 8), the first selector 6 selects the second charge signal S4 as the first select signal S10, and the second selector 7 selects the first charge signal S3 as the second select signal S20. In other words, the first selector 6 and the second selector 7 (first synchronous rectifier circuit 31) remodulate (demodulate) the acceleration signal component M1 (see Figure 9).

[0096] At this time, as shown in Figure 9, the acceleration sensor A1 generates a peak in the acceleration signal component M1 at frequency f0. The noise signal component N1 in Figure 9 is the same noise signal component N1 in Figure 4.

[0097] Figure 8 illustrates the operation when acceleration is applied to the sensor unit 1 in a direction such that the capacitance of the first capacitance unit C1 becomes greater than the capacitance of the second capacitance unit C2, and the capacitance of the fourth capacitance unit C4 becomes greater than the capacitance of the third capacitance unit C3.

[0098] Furthermore, the low-level period T1, high-level period T2, discharge period T3, maximum voltage value Vp, voltage value V1, voltage value V2, voltage value Vref, and voltage value V3 in Figure 8 represent the same values ​​as the low-level period T1, high-level period T2, discharge period T3, maximum voltage value Vp, voltage value V1, voltage value V2, voltage value Vref, and voltage value V3 in Figure 2. Also, time points t9, t11, t13, and t15 in Figure 8 represent the same time points t1, t3, t5, and t7 in Figure 2.

[0099] The CV conversion circuit 32 converts the first select signal S10 and the second select signal S20 into a first voltage signal S12 and a second voltage signal S22, and outputs the first voltage signal S12 and the second voltage signal S22 to the third selector 15. At this time, in the acceleration sensor A1, noise signal component N1 in Figure 9 is superimposed with noise caused by the operation of the CV conversion circuit 32 (e.g., 1 / f noise) and noise caused by the operation of the detection circuit 3 (e.g., white noise), so in addition to the acceleration signal component M1, a noise signal component N2 is generated (see Figure 10). Note that, as shown in Figure 10, the noise signal component N2 is caused by the operation of the CV conversion circuit 32 and the peak of the noise occurs at frequency f0.

[0100] The third selector 15 alternately selects either the first voltage signal S12 or the second voltage signal S22 in response to the pulse signal S0, and outputs the selected voltage signal as the third select signal S30 (see Figure 8). In other words, the third selector 15 modulates the acceleration signal component M1 and also modulates the noise caused by the operation of the CV conversion circuit 32 (see Figure 11). At this time, as shown in Figure 11, the acceleration sensor A1 experiences a peak in the acceleration signal component M1 at frequency f1. Also, the acceleration sensor A1 experiences a peak in noise caused by the operation of the CV conversion circuit 32 at frequency f1.

[0101] Filter 34 removes the high-frequency components of the third select signal S30. More specifically, filter 34 removes the acceleration signal component M1 and the high-frequency region of the noise signal component N2 (particularly noise caused by the operation of the CV conversion circuit 32) at a cutoff frequency fc1 (see Figure 12). As a result, the acceleration sensor A1 outputs a detection signal S40 from the signal output terminal 5 that does not contain the acceleration signal component M1 and contains only the noise signal component N3 (see Figures 8 and 12). Note that the noise signal component N3 shown in Figure 12 is the noise signal component obtained by removing the high-frequency region of the noise signal component N2 shown in Figure 11.

[0102] Incidentally, the detection signal S40 in acceleration detection mode includes an acceleration signal component M1, as shown in Figure 7. Furthermore, the signal level of the detection signal S40 in acceleration detection mode (see Figure 2) is proportional to the value of {(C1-C2)-(C3-C4)} in equation (3). Therefore, the detection signal S40 in acceleration detection mode may be affected by factors other than acceleration, such as an increase or decrease (change) in the capacitance of the sensor unit 1. Thus, in acceleration sensor A1 in acceleration detection mode, if there is vibration (disturbance vibration) in the inspection environment, such as inspection equipment, the capacitance of the sensor unit 1 may change, and a noise signal component caused by the disturbance vibration may be superimposed on the acceleration signal component M1. For this reason, in acceleration sensor A1 in acceleration detection mode, it is necessary to suppress the disturbance vibration in the inspection environment to a very low vibration level in order to accurately detect circuit noise.

[0103] On the other hand, the detection signal S40 in noise detection mode does not include the acceleration signal component M1, as shown in Figure 12. Also, the signal level of the detection signal S40 in noise detection mode (see Figure 8) is zero. In other words, the signal level of the detection signal S40 in noise detection mode is not proportional to the value of {(C1-C2)-(C3-C4)} in equation (3). Therefore, the detection signal S40 in noise detection mode is not affected by changes in the capacitance of the sensor unit 1. That is, the acceleration sensor A1 in noise detection mode is not affected by external vibrations even if there are external vibrations in the inspection environment. Therefore, the acceleration sensor A1 in noise detection mode can accurately detect only the noise signal component N3 (see Figure 12). In short, the acceleration sensor A1 can accurately detect circuit noise.

[0104] Furthermore, the acceleration sensor A1 can accurately detect circuit noise (e.g., noise signal component N3) caused by random failures in electrical circuits (e.g., detection circuit 3) that occur during manufacturing and inspection, for example, in noise detection mode, thereby improving reliability.

[0105] Furthermore, since the acceleration sensor A1 does not require suppressing external vibrations in the inspection environment to a very low vibration level, it can detect circuit noise with a simpler configuration than, for example, when equipment is required to suppress external vibrations in the inspection environment to a very low vibration level.

[0106] The first capacitance section C1 and the fourth capacitance section C4 have the same polarity indicating the increase or decrease in their respective capacitances. The second capacitance section C2 and the third capacitance section C3 have the same polarity indicating the increase or decrease in their respective capacitances. The first capacitance section C1 and the second capacitance section C2 have opposite polarity indicating the increase or decrease in their respective capacitances. As a result, the acceleration sensor A1 can improve the acceleration detection accuracy compared to when the sensor section 1 is configured as a half-bridge type.

[0107] The operation switching unit 30 switches the operating states of the first selector 6 and the second selector 7 so that they operate in either the first or second operating mode. As a result, the acceleration sensor A1 can accurately detect circuit noise by changing the operating mode of the operation switching unit 30.

[0108] The control circuit 4 has two control modes: an acceleration detection mode for detecting acceleration and a noise detection mode for detecting circuit noise. When the control mode is acceleration detection mode, the control circuit 4 controls the operation switching unit 30 so that the first selector 6 and the second selector 7 operate in the second operation mode. When the control mode is noise detection mode, the control circuit 4 controls the operation switching unit 30 so that the first selector 6 and the second selector 7 operate in the first operation mode. As a result, the acceleration sensor A1 can accurately detect circuit noise by changing the control mode of the control circuit 4.

[0109] The detection method for acceleration sensor A1 includes an operation step, a signal output step, an amplification step, a charge selection step, a voltage selection step, an output step, and a rejection step. In the operation step, the control circuit 4 is operated in either an acceleration detection mode for detecting acceleration or a noise detection mode for detecting circuit noise. In the signal output step, a pulse signal S0 is output. In the amplification step, a non-inverting amplified signal S1, obtained by amplifying the pulse signal S0, and an inverting amplified signal S2, obtained by inverting the pulse signal S0, are output to the sensor unit 1. In the charge selection step, one of the first charge signal S3 and the second charge signal S4 from the sensor unit 1 is output as the first select signal S10, and the remaining charge signal of the first charge signal S3 and the second charge signal S4 is output as the second select signal S20. In the voltage selection step, a first voltage signal S12, which is obtained by subtracting the second select signal S20 from the first select signal S10, is output, and a second voltage signal S22, which is obtained by subtracting the first select signal S10 from the second select signal S20, is also output. In the output step, one of the voltage signals, the first voltage signal S12 or the second voltage signal S22, is alternately selected according to the pulse signal S0, and the selected voltage signal is output as the third select signal S30. In the removal step, the high-frequency components of the third select signal S30 are removed.

[0110] In the charge selection step, when the control mode is acceleration detection mode, the first charge signal S3 is output as the first select signal S10, and the second charge signal S4 is output as the second select signal S20. Also in the charge selection step, when the control mode is noise detection mode, the first output state and the second output state are alternately switched according to the pulse signal S0. The first output state is when the first charge signal S3 is output as the first select signal S10, and the second charge signal S4 is output as the second select signal S20. The second output state is when the second charge signal S4 is output as the first select signal S10, and the first charge signal S3 is output as the second select signal S20. In other words, the above detection method is a detection method for realizing the acceleration sensor A1 described above. Therefore, the above detection method can accurately detect circuit noise, similar to the acceleration sensor A1 described above.

[0111] The detection method described above is implemented by having one or more processors execute a program (computer program). This program is, for example, a program that causes one or more processors in the control circuit 4 to execute the detection method described above. Therefore, according to the program described above, circuit noise can be accurately detected, similar to the detection method described above.

[0112] (3) Variant The signal generator 21 is located outside the control circuit 4, but it may also be located inside the control circuit 4.

[0113] The control circuit 4 outputs the second control signal S6 to the switching element SW1 of the first integrator 16 and the third control signal S7 to the switching element SW2 of the second integrator 17. However, for example, the second control signal S6 may be output to both the switching element SW1 and the switching element SW2.

[0114] In this embodiment, the first integrator 16 has a switching element SW1, but it does not necessarily have to have a switching element SW1. However, it is preferable that the first integrator 16 has a switching element SW1 in order to improve the integration accuracy.

[0115] In this embodiment, the second integrator 17 has a switching element SW2, but it does not necessarily have to have a switching element SW2. However, it is preferable that the second integrator 17 has a switching element SW2 in order to improve the integration accuracy.

[0116] The embodiments and modifications described above are only a selection of the various embodiments and modifications of this disclosure.

[0117] (Aspect) This specification discloses the following aspects:

[0118] An acceleration sensor (A1) according to the first embodiment comprises a sensor unit (1), a power supply circuit (2), and a detection circuit (3). Acceleration is applied to the sensor unit (1). The power supply circuit (2) is electrically connected to the sensor unit (1). The detection circuit (3) is electrically connected to the sensor unit (1) and detects acceleration. The power supply circuit (2) includes a signal generator (21), a non-inverting amplifier circuit (22), and an inverting amplifier circuit (23). The signal generator (21) outputs a pulse signal (S0). The non-inverting amplifier circuit (22) amplifies the pulse signal (S0) and outputs a non-inverting amplified signal (S1). The inverting amplifier circuit (23) inverts and amplifies the pulse signal (S0) and outputs an inverting amplified signal (S2). The sensor unit (1) includes a first input terminal (11), a second input terminal (12), a first output terminal (13), a second output terminal (14), a first capacitance unit (C1), a second capacitance unit (C2), a third capacitance unit (C3), and a fourth capacitance unit (C4). The first input terminal (11) receives an input of a non-inverting amplified signal (S1). The second input terminal (12) receives an input of an inverting amplified signal (S2). The first output terminal (13) outputs a first charge signal (S3) corresponding to acceleration. The second output terminal (14) outputs a second charge signal (S4) corresponding to acceleration and in opposite phase to the first charge signal (S3). The first capacitance unit (C1) is provided in the circuit between the first input terminal (11) and the first output terminal (13). The second capacitance unit (C2) is provided in the circuit between the first output terminal (13) and the second input terminal (12). The third capacitance unit (C3) is provided in the circuit between the first input terminal (11) and the second output terminal (14). The fourth capacitance unit (C4) is provided in the circuit between the second output terminal (14) and the second input terminal (12). The detection circuit (3) includes a first selector (6), a second selector (7), an operation switching unit (30), a CV conversion circuit (32), a third selector (15), and a filter (34). The first selector (6) selects one of the first charge signal (S3) and the second charge signal (S4) and outputs the one of the signals as the first select signal (S10). The second selector (7) selects the remaining signal from the first charge signal (S3) and the second charge signal (S4), and outputs the remaining signal as the second select signal (S20).The operation switching unit (30) switches the operating state of the first selector (6) and the second selector (7). The CV conversion circuit (32) receives the input of the first select signal (S10) and the second select signal (S20) and outputs the first voltage signal (S12) and the second voltage signal (S22). The first voltage signal (S12) is the signal obtained by subtracting the second select signal (S20) from the first select signal (S10). The second voltage signal (S22) is the signal obtained by subtracting the first select signal (S10) from the second select signal (S20). The third selector (15) alternately selects either the first voltage signal (S12) or the second voltage signal (S22) in response to the pulse signal (S0) and outputs the above voltage signal as the third select signal (S30). The filter (34) removes the high-frequency components of the third select signal (S30).

[0119] According to this embodiment, circuit noise can be accurately detected.

[0120] In the second embodiment of the acceleration sensor (A1), in the first embodiment, the first capacitance section (C1) and the fourth capacitance section (C4) have the same polarity indicating the increase or decrease in capacitance of the first capacitance section (C1) and the fourth capacitance section (C4). The second capacitance section (C2) and the third capacitance section (C3) have the same polarity indicating the increase or decrease in capacitance of the second capacitance section (C2) and the third capacitance section (C3). The first capacitance section (C1) and the second capacitance section (C2) have opposite polarity indicating the increase or decrease in capacitance of the first capacitance section (C1) and the second capacitance section (C2).

[0121] According to this embodiment, the accuracy of acceleration detection can be improved.

[0122] In the third embodiment of the acceleration sensor (A1), in the first or second embodiment, the operation switching unit (30) switches the operating state of the first selector (6) and the second selector (7) so that the first selector (6) and the second selector (7) operate in either the first operating mode or the second operating mode. The first operating mode is an operating mode in which the first selector (6) selects the first charge signal (S3) as the first select signal (S10) and the second selector (7) selects the second charge signal (S4) as the second select signal (S20), and the first selector (6) selects the second charge signal (S4) as the first select signal (S10) and the second selector (7) selects the first charge signal (S3) as the second select signal (S20), and the operation switching unit (30) switches between these two modes in accordance with the pulse signal (S0). The second operating mode is one in which the first selector (6) selects the first charge signal (S3) as the first select signal (S10), and the second selector (7) selects the second charge signal (S4) as the second select signal (S20).

[0123] According to this embodiment, circuit noise can be accurately detected by changing the operating mode of the operation switching unit (30).

[0124] The acceleration sensor (A1) according to the fourth embodiment further comprises a control circuit (4) in the third embodiment. The control circuit (4) controls the operation switching unit (30). Based on the control from the control circuit (4), the operation switching unit (30) switches the operating state of the first selector (6) and the second selector (7) so that the first selector (6) and the second selector (7) operate in either the first operation mode or the second operation mode. The control circuit (4) has an acceleration detection mode for detecting acceleration and a noise detection mode for detecting circuit noise as control modes of the control circuit (4). When the control mode is the acceleration detection mode, the control circuit (4) controls the operation switching unit (30) so that the first selector (6) and the second selector (7) operate in the second operation mode. When the control mode is the noise detection mode, the control circuit (4) controls the operation switching unit (30) so that the first selector (6) and the second selector (7) operate in the first operation mode.

[0125] According to this embodiment, circuit noise can be accurately detected by changing the control mode of the control circuit (4).

[0126] The detection method according to the fifth embodiment includes an operation step, a signal output step, an amplification step, a charge selection step, a voltage selection step, an output step, and a rejection step. In the operation step, the control circuit (4) is operated in either an acceleration detection mode for detecting acceleration or a noise detection mode for detecting circuit noise. In the signal output step, a pulse signal (S0) is output. In the amplification step, a non-inverting amplified signal (S1) obtained by amplifying the pulse signal (S0) and an inverting amplified signal (S2) obtained by inverting the pulse signal (S0) are output to the sensor unit (1). In the charge selection step, one of the first charge signal (S3) and the second charge signal (S4) from the sensor unit (1) is output as a first select signal (S10), and the remaining signal of the first charge signal (S3) and the second charge signal (S4) is output as a second select signal (S20). In the voltage selection step, a first voltage signal (S12), which is obtained by subtracting the second select signal (S20) from the first select signal (S10), is output, and a second voltage signal (S22), which is obtained by subtracting the first select signal (S10) from the second select signal (S20), is output. In the output step, one of the voltage signals, either the first voltage signal (S12) or the second voltage signal (S22), is alternately selected according to the pulse signal (S0), and the above voltage signal is output as the third select signal (S30). In the removal step, the high-frequency components of the third select signal (S30) are removed. In addition, in the charge selection step, if the control mode is acceleration detection mode, a first charge signal (S3) is output as the first select signal (S10), and a second charge signal (S4) is output as the second select signal (S20). Furthermore, in the charge selection step, when the control mode is noise detection mode, the first output state and the second output state are alternately switched according to the pulse signal (S0). The first output state is a state in which the first charge signal (S3) is output as the first select signal (S10) and the second charge signal (S4) is output as the second select signal (S20). The second output state is a state in which the second charge signal (S4) is output as the first select signal (S10) and the first charge signal (S3) is output as the second select signal (S20).

[0127] According to this embodiment, circuit noise can be accurately detected.

[0128] The program according to the sixth embodiment causes one or more processors to execute the detection method according to the fifth embodiment.

[0129] According to this embodiment, circuit noise can be accurately detected. [Explanation of symbols]

[0130] 1. Sensor section 2 Power circuit 3. Detection circuit 4. Control circuits 6. First Selector 7. Second Selector 11 First input terminal 12 Second input terminal 13 First output terminal 14. Second output terminal 15. Third Selector 21 Signal Generator 22 Non-inverting amplifier circuit 23 Inverting Amplifier Circuit 30 Operation switching section 32 CV conversion circuit 34 Filters A1 Accelerometer C1 First capacitance section C2 Second capacitance section C3 Third capacitance section C4 Fourth capacitance section S0 pulse signal S1 Non-inverting amplified signal S2 Inverted Amplified Signal S3 1st charge signal S4 Second charge signal S10 First Select Signal S12 First voltage signal S20 Second Select Signal S22 Second voltage signal S30 Third Select Signal

Claims

1. The sensor unit to which acceleration is applied, A power supply circuit electrically connected to the aforementioned sensor unit, The system comprises a detection circuit electrically connected to the sensor unit for detecting the acceleration, The aforementioned power supply circuit is A signal generator that outputs a pulse signal, A non-inverting amplifier circuit that amplifies the pulse signal and outputs a non-inverting amplified signal, The circuit includes an inverting amplifier that inverts and amplifies the pulse signal to output an inverted amplified signal, The aforementioned sensor unit is A first input terminal that receives the input of the non-inverting amplified signal, A second input terminal that receives the input of the inverting amplifier signal, A first output terminal that outputs a first charge signal corresponding to the acceleration, A second output terminal that outputs a second charge signal corresponding to the acceleration and in opposite phase to the first charge signal, A first capacitance unit is provided in the circuit between the first input terminal and the first output terminal, A second capacitance unit is provided in the circuit between the first output terminal and the second input terminal, A third capacitance unit is provided in the circuit between the first input terminal and the second output terminal, It has a fourth capacitance section provided in the circuit between the second output terminal and the second input terminal, The detection circuit is A first selector that selects one of the first charge signal and the second charge signal and outputs the one signal as a first select signal, A second selector selects the remaining signal from the first charge signal and the second charge signal and outputs the remaining signal as a second select signal, An operation switching unit that switches the operating state of the first selector and the second selector, A CV conversion circuit that receives the input of the first select signal and the second select signal, and outputs a first voltage signal which is the signal obtained by subtracting the second select signal from the first select signal, and a second voltage signal which is the signal obtained by subtracting the first select signal from the second select signal, A third selector that alternately selects either the first voltage signal or the second voltage signal in response to the pulse signal and outputs the voltage signal as a third select signal, A filter that removes the high-frequency components of the third select signal, Accelerometer.

2. The first capacitance section and the fourth capacitance section have the same polarity indicating the increase or decrease in capacitance of the first capacitance section and the fourth capacitance section, The second capacitance section and the third capacitance section have the same polarity indicating the increase or decrease in capacitance of the second capacitance section and the third capacitance section, The first capacitance section and the second capacitance section have opposite polarities indicating the increase or decrease in capacitance of the first capacitance section and the second capacitance section, respectively. The acceleration sensor according to claim 1.

3. The operation switching unit switches the operating state of the first selector and the second selector so that the first selector and the second selector operate in either the first operating mode or the second operating mode. The first operating mode is an operating mode that alternately switches between, in accordance with the pulse signal, a case in which the first selector selects the first charge signal as the first select signal and the second selector selects the second charge signal as the second select signal, and a case in which the first selector selects the second charge signal as the first select signal and the second selector selects the first charge signal as the second select signal. The second operating mode is an operating mode in which the first selector selects the first charge signal as the first select signal, and the second selector selects the second charge signal as the second select signal. The acceleration sensor according to claim 1 or claim 2.

4. The control circuit further comprises the control of the operation switching unit, The operation switching unit switches the operating state of the first selector and the second selector so that the first selector and the second selector operate in either the first operating mode or the second operating mode, based on the control from the control circuit. The aforementioned control circuit is The control mode of the control circuit includes an acceleration detection mode for detecting the acceleration and a noise detection mode for detecting circuit noise. When the control mode is the acceleration detection mode, the operation switching unit is controlled so that the first selector and the second selector operate in the second operation mode. When the control mode is the noise detection mode, the operation switching unit is controlled so that the first selector and the second selector operate in the first operation mode. The acceleration sensor according to claim 3.

5. An operation step in which the control circuit is operated in either an acceleration detection mode for detecting acceleration, or a noise detection mode for detecting circuit noise, A signal output step that outputs a pulse signal, An amplification step which outputs a non-inverting amplified signal obtained by amplifying the pulse signal and an inverting amplified signal obtained by inverting the pulse signal to the sensor unit, A charge selection step in which one of the first charge signal and the second charge signal from the sensor unit is output as a first select signal, and the remaining signal of the first charge signal and the second charge signal is output as a second select signal, A voltage selection step that outputs a first voltage signal which is the signal obtained by subtracting the second select signal from the first select signal, and a second voltage signal which is the signal obtained by subtracting the first select signal from the second select signal, An output step which alternately selects either the first voltage signal or the second voltage signal in response to the pulse signal and outputs the voltage signal as a third select signal, The step includes removing the high-frequency components of the third select signal, In the charge selection step, When the control mode is the acceleration detection mode, the first charge signal is output as the first select signal, and the second charge signal is output as the second select signal. When the control mode is the noise detection mode, the system alternately switches between a first output state in which the first charge signal is output as the first select signal and the second charge signal is output as the second select signal, and a second output state in which the second charge signal is output as the first select signal and the first charge signal is output as the second select signal, in accordance with the pulse signal. Detection method.

6. The detection method described in claim 5 is to be executed by one or more processors. program.

Images