Physical quantity detection circuit and physical quantity detection device

Abstract

To provide a physical quantity detection circuit that can generate a signal available for fault diagnosis of wiring connected with a physical quantity detection element, while reducing the possibility that the accuracy in detecting a physical quantity may be reduced due to a vibration leakage component.SOLUTION: A physical quantity detection circuit has: a driving circuit that applies, to a driving electrode of a physical quantity detection element, a driving signal including a first frequency component and a second frequency component with a frequency different from the frequency of the first frequency component; a physical quantity detection signal output circuit that outputs a physical quantity detection signal based on a first physical quantity component output from a first detection electrode of the physical quantity detection element and a second physical quantity component output from a second detection electrode of the physical quantity detection element; and a first signal for fault diagnosis output circuit that outputs a first signal for fault diagnosis generated based on a first electrostatic leakage component in which the second frequency component propagates to the first detection electrode and a second electrostatic leakage component in which the second frequency component propagates to the second detection electrode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a physical quantity detection circuit and a physical quantity detection device. [Background technology]

[0002] Currently, various physical quantity detection devices, such as gyro sensors for detecting angular velocity and accelerometers for detecting acceleration, are widely used in various systems and electronic devices. In recent years, methods have been proposed to diagnose whether or not a physical quantity detection device has malfunctioned, in order to achieve high reliability in systems using physical quantity detection devices.

[0003] For example, Patent Document 1 describes a physical quantity sensor that diagnoses faults in parallel with detecting physical quantities. In the physical quantity sensor described in Patent Document 1, the physical quantity detection circuit applies a drive signal to the drive electrodes of the physical quantity detection element, causing the two drive vibration arms to bend and vibrate. When a physical quantity is applied, the first and second physical quantity components generated at the two detection electrodes due to the bending and vibrating of the two detection vibration arms are converted into voltages using two charge amplifier circuits, further differentially amplified, and then synchronously detected to generate a physical quantity detection signal. Furthermore, the physical quantity detection circuit converts the first and second vibration leakage components generated at the two detection electrodes due to the bending and vibrating of the two drive vibration arms into voltages using the two charge amplifier circuits, further summation amplified, and then synchronously detected to generate a vibration leakage signal, and fault diagnosis is performed based on the vibration leakage signal. Therefore, according to the physical quantity sensor described in Patent Document 1, if a break or short circuit occurs in the wiring connecting the physical quantity detection element and the physical quantity detection circuit, the magnitude of the vibration leakage signal will fall outside a predetermined range, allowing for a fault diagnosis. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-180785 [Overview of the Initiative]

Problems to be Solved by the Invention

[0005] However, in the physical quantity sensor described in Patent Document 1, if the vibration leakage component is zero or close to zero, there is almost no difference in the magnitude of the vibration leakage signal before and after the wiring connecting the physical quantity detection element and the physical quantity detection circuit is disconnected, so there is a risk of misdiagnosing a failure. Therefore, it is necessary to deliberately tune so that the balance of the bending vibration of the physical quantity detection signal is disrupted to generate a first vibration leakage component and a second vibration leakage component that are relatively large. However, due to the characteristics of the two charge amplifier circuits described above, a part of the vibration leakage component may be superimposed on the physical quantity detection signal, and there is a risk that the detection accuracy of the physical quantity will decrease.

Means for Solving the Problems

[0006] One aspect of the physical quantity detection circuit according to the present invention is a drive circuit that applies a drive signal including a first frequency component for driving the physical quantity detection element to a drive electrode of the physical quantity detection element for detecting a physical quantity; a physical quantity detection signal output circuit that outputs a physical quantity detection signal corresponding to the physical quantity based on a first physical quantity component included in a first signal output from the first detection electrode of the physical quantity detection element and a second physical quantity component included in a second signal output from the second detection electrode of the physical quantity detection element when the drive signal is applied to the physical quantity detection element; and a first failure diagnosis signal output circuit. The drive signal includes a second frequency component having a frequency different from the frequency of the first frequency component. The first signal includes a first electrostatic leakage component that is a component in which the second frequency component propagates to the first detection electrode through a first electrostatic coupling capacitance between the drive electrode and the first detection electrode. The second signal includes a second electrostatic leakage component that is a component in which the second frequency component propagates to the second detection electrode through a second electrostatic coupling capacitance between the drive electrode and the second detection electrode. The first failure diagnosis signal output circuit outputs a first failure diagnosis signal generated based on the first electrostatic leakage component and the second electrostatic leakage component.

[0007] One aspect of the physical quantity detection device according to the present invention is one aspect of the physical quantity detection circuit, and the physical quantity detection element.

Brief Description of the Drawings

[0008] [Figure 1] Functional block diagram of the physical quantity detection device of the first embodiment. [Figure 2] Plan view of the vibrating piece of the physical quantity detection element. [Figure 3] Diagram showing a configuration example of the drive circuit in the first embodiment. [Figure 4] Diagram showing a configuration example of the detection circuit in the first embodiment. [Figure 5] Diagram showing an example of waveforms of various signals with respect to the physical quantity component in the first embodiment. [Figure 6] Diagram showing an example of waveforms of various signals with respect to the electrostatic leakage component in the first embodiment. [Figure 7] Functional block diagram of the physical quantity detection device of the second embodiment. [Figure 8] Diagram showing a configuration example of the drive circuit in the second embodiment. [Figure 9] Diagram showing a configuration example of the detection circuit in the second embodiment. [Figure 10] Diagram showing an example of waveforms of various signals with respect to the physical quantity component in the second embodiment. [Figure 11] Diagram showing an example of waveforms of various signals with respect to the electrostatic leakage component in the second embodiment. [Figure 12] Diagram showing an example of waveforms of various signals with respect to the vibration leakage component in the second embodiment.

Modes for Carrying Out the Invention

[0009] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. The embodiments described below are not intended to unduly limit the scope of the present invention as described in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0010] In the following explanation, we will use a physical quantity detection device, specifically an angular velocity detection device, as an example to explain how to detect angular velocity as a physical quantity.

[0011] 1. First Embodiment 1-1. Configuration of the physical quantity detection device Figure 1 is a functional block diagram of the physical quantity detection device of the first embodiment. As shown in Figure 1, the physical quantity detection device 1 of the first embodiment includes a physical quantity detection element 100 for detecting physical quantities and a physical quantity detection circuit 200.

[0012] The physical quantity detection element 100 has a vibrating piece on which a drive electrode and a detection electrode are arranged. Generally, in order to reduce the impedance of the vibrating piece as much as possible and increase the oscillation efficiency, the vibrating piece is sealed in an airtight package. In this embodiment, the physical quantity detection element 100 has a so-called double T-shaped vibrating piece having two T-shaped drive vibrating arms.

[0013] Figure 2 is a plan view of the vibrating element of the physical quantity detection element 100 in this embodiment. The physical quantity detection element 100 has a double T-shaped vibrating element formed from, for example, a Z-cut quartz substrate. A vibrating element made of quartz has the advantage of being able to improve the accuracy of angular velocity detection because the fluctuation of the resonant frequency with respect to temperature changes is extremely small. Note that the X, Y, and Z axes in Figure 2 represent the axes of the quartz.

[0014] As shown in Figure 2, the vibrating piece of the physical quantity detection element 100 has two drive bases 104a and 104b from which drive vibrating arms 101a and 101b extend in the +Y axis direction and the -Y axis direction, respectively. Drive electrodes 112 and 113 are formed on the side and top surfaces of drive vibrating arm 101a, respectively, and drive electrodes 113 and 112 are formed on the side and top surfaces of drive vibrating arm 101b, respectively. Drive electrode 112 is connected to the DG terminal of the physical quantity detection circuit 200 shown in Figure 1 by wiring not shown, and drive electrode 113 is connected to the DS terminal of the physical quantity detection circuit 200 shown in Figure 1 by wiring not shown.

[0015] The drive bases 104a and 104b are connected to the rectangular detection base 107 via connecting arms 105a and 105b that extend in the -X axis direction and the +X axis direction, respectively.

[0016] The detection vibration arm 102 extends from the detection base 107 in the +Y axis direction and the -Y axis direction. Detection electrodes 114 and 115 are formed on the upper surface of the detection vibration arm 102, and a common electrode 116 is formed on the side surface of the detection vibration arm 102. The detection electrodes 114 and 115 are connected to the detection circuit 30 via the S1 terminal and S2 terminal of the physical quantity detection circuit 200 shown in Figure 1, respectively. The common electrode 116 is grounded.

[0017] When an AC voltage is applied as a drive signal between the drive electrodes 112 and 113 of the drive vibration arms 101a and 101b, the tips of the two drive vibration arms 101a and 101b repeatedly move closer to and further apart from each other in directions A and A' due to the inverse piezoelectric effect. Hereafter, the bending vibration of the drive vibration arms 101a and 101b may also be referred to as "excited vibration".

[0018] In this state, when an angular velocity with the Z axis as the axis of rotation is applied to the vibrating piece of the physical quantity detection element 100, the driving vibrating arms 101a and 101b receive a Coriolis force in a direction perpendicular to both the direction of the bending vibration and the Z axis. As a result, the two connecting arms 105a and 105b vibrate in opposite directions, B and B'. At this time, the two detection vibrating arms 102 attempt to maintain balance and therefore perform bending vibrations in opposite directions, C and C'. The bending vibration of the detection vibrating arm 102 due to this Coriolis force and the bending vibration of the driving vibrating arms 101a and 101b are out of phase by 90°.

[0019] Then, due to the piezoelectric effect, alternating current charges based on these bending vibrations are generated on the detection electrodes 114 and 115 of the detection vibration arm 102. Here, the alternating current charges generated based on the Coriolis force change according to the magnitude of the Coriolis force, that is, the magnitude of the angular velocity applied to the physical quantity detection element 100.

[0020] The tips of the drive vibration arms 101a and 101b are formed with rectangular weights 103 that are wider than the drive vibration arms 101a and 101b. By forming weights 103 at the tips of the drive vibration arms 101a and 101b, the Coriolis force is increased and the desired resonance frequency can be obtained with relatively short vibration arms. Similarly, the tip of the detection vibration arm 102 is formed with weights 106 that are wider than the detection vibration arm 102. By forming weights 106 at the tip of the detection vibration arm 102, the alternating current charge generated at the detection electrodes 114 and 115 can be increased.

[0021] Furthermore, through the first electrostatic coupling capacitance C1 between the drive electrode 113 and the detection electrode 114 and the second electrostatic coupling capacitance C2 between the drive electrode 113 and the detection electrode 115, the frequency components of the AC contained in the drive signal supplied to the drive electrode 113 propagate to the detection electrodes 114 and 115, and an AC charge based on these frequency components is generated. However, as will be described later, this AC charge will not be mistakenly detected as angular velocity.

[0022] Incidentally, if the magnitude of the vibration energy or the amplitude of the vibration when the drive vibration arms 101a and 101b undergo flexion vibration is equal for both drive vibration arms 101a and 101b, then the vibration energy of the drive vibration arms 101a and 101b is balanced, and the detection vibration arm 102 does not flex when no angular velocity is applied to the physical quantity detection element 100. However, if the balance of the vibration energy of the two drive vibration arms 101a and 101b is disrupted, flexion vibration occurs in the detection vibration arm 102 even when no angular velocity is applied to the physical quantity detection element 100. This flexion vibration is called leakage vibration, and like vibration based on the Coriolis force, it is a flexion vibration in the C and C' directions, and alternating charges based on leakage vibration are generated at the detection electrodes 114 and 115. Since the phase of leakage vibration is shifted by 90° from vibration based on the Coriolis force, as will be described later, these alternating charges will not be misdetected as angular velocity, but in order to improve the accuracy of angular velocity detection, it is preferable that leakage vibration does not occur.

[0023] For example, by tuning the weights of the four weights 103 such that the vibration energies of the two drive vibration arms 101a are equal, the vibration energies of the two drive vibration arms 101b are equal, and the sum of the vibration energies of the two drive vibration arms 101a is equal to the sum of the vibration energies of the two drive vibration arms 101b, leakage vibration can be almost completely eliminated. The weight tuning of the weights 103 can be done, for example, by irradiating the weights 103 with a laser to remove a portion of them.

[0024] As described above, the physical quantity detection element 100 outputs an AC charge based on the detected physical quantity and an AC charge based on the drive signal propagating through the first electrostatic coupling capacitor C1 and the second electrostatic coupling capacitor C2 from the detection electrodes 114 and 115. Hereinafter, the AC charge based on the physical quantity will be referred to as the "physical quantity component," and the AC charge based on the drive signal propagating through the first electrostatic coupling capacitor C1 and the second electrostatic coupling capacitor C2 will be referred to as the "electrostatic leakage component." In this embodiment, the physical quantity detected by the physical quantity detection element 100 is the angular velocity corresponding to the Coriolis force.

[0025] Returning to the description of Figure 1, the physical quantity detection circuit 200 includes a reference voltage circuit 10, a drive circuit 20, a detection circuit 30, an analog-to-digital conversion circuit 41, an analog-to-digital conversion circuit 42, a digital signal processing circuit 51, a digital signal processing circuit 52, a fault diagnosis circuit 61, an interface circuit 70, a memory unit 80, and an oscillator circuit 90. The physical quantity detection circuit 200 may be implemented, for example, as a single-chip integrated circuit. Note that the physical quantity detection circuit 200 may also have a configuration in which some of these elements are omitted or modified, or other elements are added.

[0026] The reference voltage circuit 10 generates constant voltages and constant currents, such as the reference voltage which is an analog ground voltage, based on the power supply voltage and ground voltage supplied from the VDD terminal and VSS terminal of the physical quantity detection circuit 200, respectively, and supplies them to the drive circuit 20 and the detection circuit 30.

[0027] The drive circuit 20 applies a drive signal containing a first frequency component to drive the physical quantity detection element 100 to the drive electrode 113 of the physical quantity detection element 100 via the DS terminal. The physical quantity detection element 100 is excited and vibrates by the drive signal. The drive circuit 20 also receives the oscillation current generated at the drive electrode 112 due to the excitation vibration of the physical quantity detection element 100 via the DG terminal and feedback controls the amplitude level of the drive signal so that the amplitude of this oscillation current is kept constant. The drive circuit 20 also generates a detection signal SDET with the same phase as the drive signal, and a detection signal QDET with twice the frequency of the detection signal SDET, and outputs them to the detection circuit 30.

[0028] The detection circuit 30 outputs a physical quantity detection signal SAO corresponding to the physical quantity detected by the physical quantity detection element 100, based on the first physical quantity component contained in the first signal output from the detection electrode 114 of the physical quantity detection element 100 and the second physical quantity component contained in the second signal output from the detection electrode 115 of the physical quantity detection element 100. The first signal is an AC charge input via the S1 terminal of the physical quantity detection circuit 200, and the second signal is an AC charge input via the S2 terminal of the physical quantity detection circuit 200. The detection circuit 30 uses the detection signal SDET to detect a physical quantity component based on the first physical quantity component contained in the first signal and the second physical quantity component contained in the second signal, and generates and outputs a physical quantity detection signal SAO, which is an analog signal with a voltage level corresponding to the magnitude of the detected physical quantity component. Note that the detection electrode 114 is an example of a "first detection electrode," and the detection electrode 115 is an example of a "second detection electrode."

[0029] Furthermore, the detection circuit 30 outputs an electrostatic leakage detection signal QAO based on the first electrostatic leakage component included in the first signal and the second electrostatic leakage component included in the second signal. The drive signal output from the drive circuit 20 includes a second frequency component with a frequency different from the first frequency component. The first electrostatic leakage component is the component of the second frequency component that propagates to the detection electrode 114 via the first electrostatic coupling capacitance C1 between the drive electrode 113 and the detection electrode 114 of the physical quantity detection element 100. Similarly, the second electrostatic leakage component is the component of the second frequency component that propagates to the detection electrode 115 via the second electrostatic coupling capacitance C2 between the drive electrode 113 and the detection electrode 115 of the physical quantity detection element 100. In this embodiment, the frequency of the second frequency component is twice the frequency of the first frequency component, and as will be described later, it is a frequency component that is generated when the drive circuit 20 generates the drive signal. The detection circuit 30 uses the detection signal QDET to detect an electrostatic leakage component based on the first electrostatic leakage component contained in the first signal and the second electrostatic leakage component contained in the second signal, and generates and outputs an electrostatic leakage detection signal QAO, which is an analog signal with a voltage level corresponding to the magnitude of the detected electrostatic leakage component.

[0030] The storage unit 80 has a non-volatile memory (not shown) in which various trimming data for the drive circuit 20 and the detection circuit 30 are stored. The non-volatile memory may be configured as, for example, a MONOS type memory or an EEPROM. MONOS is an abbreviation for Metal Oxide Nitride Oxide Silicon. EEPROM is an abbreviation for Electrically Erasable Programmable Read-Only Memory. Furthermore, the storage unit 80 may have a register (not shown) and may be configured so that when the physical quantity detection circuit 200 is powered on, that is, when the voltage at the VDD terminal rises from 0V to a desired voltage, the various trimming data stored in the non-volatile memory are transferred to and held in the register, and the various trimming data held in the register are supplied to the drive circuit 20 and the detection circuit 30.

[0031] The analog-to-digital conversion circuit 41 operates based on the clock signal ADCLK and converts the physical quantity detection signal SAO, which is an analog signal output from the detection circuit 30, into a digital physical quantity detection signal SDO and outputs it.

[0032] The analog-to-digital conversion circuit 42 operates based on the clock signal ADCLK and converts the electrostatic leakage detection signal QAO, which is an analog signal output from the detection circuit 30, into a digital signal, the electrostatic leakage detection signal QDO, and outputs it.

[0033] The digital signal processing circuit 51 operates based on the master clock signal MCLK, performs predetermined calculations on the physical quantity detection signal SDO output from the analog / digital conversion circuit 41, and outputs the physical quantity detection signal SDOX obtained from the calculations.

[0034] The digital signal processing circuit 52 operates based on the master clock signal MCLK, performs predetermined calculations on the electrostatic leakage detection signal QDO output from the analog / digital conversion circuit 42, and outputs the electrostatic leakage detection signal QDOX obtained from the calculations.

[0035] The fault diagnosis circuit 61 operates in accordance with the master clock signal MCLK and performs fault diagnosis of the physical quantity detection device 1 based on the electrostatic leakage detection signal QDOX. The fault diagnosis circuit 61 then outputs a fault diagnosis result signal QF indicating whether or not the physical quantity detection device 1 is faulty. If the physical quantity detection device 1 is functioning normally, the value of the electrostatic leakage detection signal QDOX falls within a predetermined first range. In contrast, if, for example, a portion of the wiring electrically connected to the detection electrode 114 of the physical quantity detection element 100 is cut or short-circuited, or if a portion of the wiring electrically connected to the detection electrode 115 of the physical quantity detection element 100 is cut or short-circuited, the value of the electrostatic leakage detection signal QDOX falls outside the first range. Therefore, the fault diagnosis circuit 61 may diagnose that the physical quantity detection device 1 is faulty if the value of the electrostatic leakage detection signal QDOX does not fall within the first range. For example, the first range may include a predetermined value that is designed to be normal when the physical quantity detection device 1 is functioning normally, as well as a range that may change from that predetermined value over time. The first range may also be fixed or variable. For example, the first range may be set variably according to a value stored in a register of the memory unit 80 that can be rewritten from outside the physical quantity detection circuit 200.

[0036] The interface circuit 70 outputs the physical quantity detection signal SDOX, which is output from the digital signal processing circuit 51, to the MCU 5 in response to a request from the MCU 5, which is an external device of the physical quantity detection circuit 200. MCU stands for Micro Control Unit. The interface circuit 70 may also output the electrostatic leakage detection signal QDOX, which is output from the digital signal processing circuit 52, to the MCU 5 in response to a request from the MCU 5. In this case, the physical quantity detection circuit 200 does not have a fault diagnosis circuit 61, and the MCU 5 may perform fault diagnosis similar to that of the fault diagnosis circuit 61 based on the electrostatic leakage detection signal QDOX.

[0037] Furthermore, the interface circuit 70 performs processes such as reading data stored in the non-volatile memory and registers of the storage unit 80 and outputting it to the MCU 5 in response to requests from the MCU 5, and writing data input from the MCU 5 to the non-volatile memory and registers of the storage unit 80. For example, the MCU 5 may perform a process to write the aforementioned first range setting value to a predetermined register.

[0038] The interface circuit 70 is, for example, an SPI bus interface circuit. The selection signal, clock signal, and data signal transmitted from the MCU 5 are input to the physical quantity detection circuit 200 via the SS terminal, SCLK terminal, and SI terminal, respectively, and the data signal is output to the MCU 5 via the SO terminal of the physical quantity detection circuit 200. SPI stands for Serial Peripheral Interface. Note that the interface circuit 70 can also be used with various other buses besides the SPI bus, for example, I 2 It may also be an interface circuit compatible with C-bus, etc. 2 C stands for Inter-Integrated Circuit.

[0039] The oscillator circuit 90 generates a master clock signal MCLK and supplies it to the digital signal processing circuits 51 and 52 and the fault diagnosis circuit 61. The oscillator circuit 90 also divides the master clock signal MCLK to generate a clock signal ADCLK and supplies it to the analog-to-digital conversion circuits 41 and 42. The oscillator circuit 90 may generate the master clock signal MCLK using, for example, a ring oscillator or a CR oscillator circuit.

[0040] In the physical quantity detection device 1 of the first embodiment configured as described above, the physical quantity detection element 100 outputs a first signal, which is an alternating current charge generated at the detection electrode 114, and a second signal, which is an alternating current charge generated at the detection electrode 115. The physical quantity detection circuit 200 generates a physical quantity detection signal SDOX corresponding to the physical quantity detected by the physical quantity detection element 100, based on the first and second signals output from the physical quantity detection element 100. The physical quantity detection circuit 200 also generates a fault diagnosis result signal QF indicating whether or not there is a malfunction in the physical quantity detection device 1, based on the first and second signals output from the physical quantity detection element 100.

[0041] 1-2. Drive Circuit Configuration Figure 3 shows an example of the configuration of the drive circuit 20 in the first embodiment. As shown in Figure 3, the drive circuit 20 includes a current-voltage conversion circuit 21, a full-wave rectifier circuit 22, an auto-gain control circuit 23, a drive signal generation circuit 24, a phase shift circuit 25, a buffer circuit 26, and an EXNOR circuit 27. EXNOR is an abbreviation for Exclusive NOR.

[0042] The oscillation current generated in the drive electrode 112 by the excitation vibration of the physical quantity detection element 100 is input to the current-voltage conversion circuit 21 via the DG terminal, and is converted into an AC voltage signal by the current-voltage conversion circuit 21. The AC voltage signal output from the current-voltage conversion circuit 21 is input to the full-wave rectifier circuit 22 and the drive signal generation circuit 24.

[0043] The full-wave rectifier circuit 22 outputs a DC signal by full-wave rectifying the output signal of the current-voltage conversion circuit 21.

[0044] The auto-gain control circuit 23 amplifies the output signal of the full-wave rectifier circuit 22 and outputs a signal of a predetermined voltage. The auto-gain control circuit 23 controls the amplification gain according to the magnitude of the output signal of the full-wave rectifier circuit 22 so that the output signal remains constant at the predetermined voltage.

[0045] The drive signal generation circuit 24 outputs a drive signal obtained by binarizing the output signal of the current-voltage conversion circuit 21. The high-level voltage of this drive signal is the voltage of the output signal of the auto-gain control circuit 23, and remains constant at a predetermined voltage. This drive signal is supplied to the drive electrode 113 of the physical quantity detection element 100 via the DS terminal. The physical quantity detection element 100 can continue to vibrate due to the supply of the drive signal. Furthermore, by keeping the high-level voltage of the drive signal constant, the drive vibration arms 101a and 101b of the physical quantity detection element 100 can obtain a constant vibration velocity. Therefore, the vibration velocity that generates the Coriolis force becomes constant, and the sensitivity can be made more stable.

[0046] The fundamental frequency of the drive signal generated in this way matches the frequency f of the bending vibration of the drive vibration arms 101a and 101b of the physical quantity detection element 100. In addition, a second frequency component with frequency 2f is generated by full-wave rectification by the full-wave rectifier circuit 22 and superimposed on the high-level voltage of the drive signal. Therefore, the drive signal contains a first frequency component with frequency f and a second frequency component with frequency 2f.

[0047] The phase shift circuit 25 outputs a signal with the phase of the drive signal output from the drive signal generation circuit 24 advanced by 90°. The buffer circuit 26 outputs a detection signal SDET that is in phase with the drive signal. The EXNOR circuit 27 outputs a detection signal QDET, which is an EXNOR logic signal of the drive signal and the output signal of the phase shift circuit 25. The detection signal SDET is a square wave voltage signal of frequency f, and the detection signal QDET is a square wave voltage signal of frequency 2f. The detection signals SDET and QDET are supplied to the detection circuit 30.

[0048] 1-3. Configuration of the detection circuit Figure 4 shows an example of the configuration of the detection circuit 30 in the first embodiment. As shown in Figure 4, the detection circuit 30 includes charge amplifier circuits 31A, 31B, differential amplifier circuit 32, adder circuit 33, AC amplifier circuits 34A, 34B, synchronous detection circuits 35A, 35B, and smoothing circuits 36A, 36B.

[0049] The charge amplifier circuit 31A receives a first signal via the S1 terminal. As described above, the first signal is an alternating current charge generated at the detection electrode 114 of the physical quantity detection element 100, and includes a first physical quantity component and a first electrostatic leakage component.

[0050] The charge amplifier circuit 31B receives a second signal via the S2 terminal. As described above, the second signal is an alternating current charge generated at the detection electrode 115 of the physical quantity detection element 100, and includes a second physical quantity component and a second electrostatic leakage component.

[0051] In this embodiment, as shown in Figure 2, when angular velocity is applied to the physical quantity detection element 100, the detection vibration arm 102 on which the detection electrode 114 is formed and the detection vibration arm 102 on which the detection electrode 115 is formed bend and vibrate in opposite directions to maintain balance. Therefore, the first physical quantity component included in the first signal and the second physical quantity component included in the second signal are out of phase with respect to each other. Here, the statement that the first physical quantity component included in the first signal and the second physical quantity component included in the second signal are out of phase with respect to each other includes not only the case where the phase difference between the two physical quantity components is exactly 180°, but also the case where the phase difference between the two physical quantity components has a slight difference from 180° due to manufacturing errors in the physical quantity detection element 100, errors in the delay time of the signal propagation path, etc.

[0052] Furthermore, in this embodiment, the first electrostatic leakage component included in the first signal and the second electrostatic leakage component included in the second signal are in phase with each other. Here, the statement that the first electrostatic leakage component included in the first signal and the second electrostatic leakage component included in the second signal are in phase with each other includes not only the case where the phase difference between the two electrostatic leakage components is exactly 0°, but also the case where the phase difference between the two electrostatic leakage components has a slight difference from 0° due to manufacturing errors of the physical quantity detection element 100, errors in the delay time of the signal propagation path, etc.

[0053] The charge amplifier circuit 31A receives the first signal and the reference voltage V generated by the reference voltage circuit 10. ref The second signal is converted into an AC voltage signal based on the reference voltage V and output, and the charge amplifier circuit 31B then takes the second signal and outputs it to the reference voltage V. refIt converts the signal to an AC voltage signal based on the given reference and outputs it.

[0054] The differential amplifier circuit 32 differentially amplifies a signal pair consisting of the output signal of the charge amplifier circuit 31A and the output signal of the charge amplifier circuit 31B. This signal pair is based on the first signal and the second signal. As described above, the first physical quantity component included in the first signal and the second physical quantity component included in the second signal are out of phase with each other, so the physical quantity component is amplified by the differential amplifier circuit 32. On the other hand, the first electrostatic leakage component included in the first signal and the second electrostatic leakage component included in the second signal are in phase with each other, so the electrostatic leakage component is attenuated by the differential amplifier circuit 32. Therefore, the influence of the electrostatic leakage component on the physical quantity component in the output signal of the differential amplifier circuit 32 is reduced. In order to substantially eliminate the influence of the electrostatic leakage component on the physical quantity component in the output signal of the differential amplifier circuit 32, it is preferable that the difference between the first electrostatic leakage component and the second electrostatic leakage component be substantially zero. The statement that the difference between the first and second electrostatic leakage components is substantially zero means that this includes not only cases where the difference is exactly zero, but also cases where the difference is slightly different from zero due to the minimum adjustment resolution of the first and second electrostatic leakage components, or where the measured value is slightly different from zero due to measurement errors in the difference between the first and second electrostatic leakage components.

[0055] The AC amplifier circuit 34A amplifies the output signal of the differential amplifier circuit 32. The output signal of the AC amplifier circuit 34A is input to the synchronous detection circuit 35A.

[0056] The synchronous detection circuit 35A uses the output signal of the AC amplifier circuit 34A as the signal to be detected and performs synchronous detection using the detection signal SDET. This synchronous detection circuit 35A extracts the physical quantity components contained in the output signal of the AC amplifier circuit 34A. That is, the synchronous detection circuit 35A functions as a first synchronous detection circuit that synchronously detects the output signal of the AC amplifier circuit 34A, which is a signal based on the output signal of the differential amplifier circuit 32, and outputs a signal corresponding to the difference between the first physical quantity component contained in the first signal and the second physical quantity component contained in the second signal. For example, the synchronous detection circuit 35A can detect when the voltage level of the detection signal SDET is equal to the reference voltage V ref When it is higher than the reference voltage V, the output signal of AC amplifier circuit 34A is selected, and the voltage level of the detected signal SDET is equal to the reference voltage V. ref When the value is lower than the reference voltage V, the output signal of the AC amplifier circuit 34A is sent to the reference voltage V. ref A switch circuit that selects the inverted signal may also be used.

[0057] The smoothing circuit 36A smooths the output signal of the synchronous detection circuit 35A into a DC voltage signal. The output signal of the smoothing circuit 36A is output from the detection circuit 30 as a physical quantity detection signal SAO. In other words, the smoothing circuit 36A functions as a physical quantity detection signal generation circuit that generates the physical quantity detection signal SAO based on the output signal of the synchronous detection circuit 35A, which is the first synchronous detection circuit.

[0058] Thus, in this embodiment, the charge amplifier circuits 31A, 31B, differential amplifier circuit 32, AC amplifier circuit 34A, synchronous detection circuit 35A, and smoothing circuit 36A function as physical quantity detection signal output circuits that output a physical quantity detection signal SAO corresponding to the physical quantity detected by the physical quantity detection element 100, based on the first physical quantity component included in the first signal and the second physical quantity component included in the second signal.

[0059] The addition circuit 33 adds a signal pair consisting of the output signal of the charge amplifier circuit 31A and the output signal of the charge amplifier circuit 31B. As described above, since the first physical quantity component included in the first signal and the second physical quantity component included in the second signal are in opposite phases to each other, the physical quantity component is attenuated by the addition circuit 33. On the other hand, since the first electrostatic leakage component included in the first signal and the second electrostatic leakage component included in the second signal are in the same phase as each other, the electrostatic leakage component is amplified by the addition circuit 33.

[0060] The AC amplifier circuit 34B amplifies the output signal of the addition circuit 33. The output signal of the AC amplifier circuit 34B is input to the synchronous detection circuit 35B.

[0061] The synchronous detection circuit 35B performs synchronous detection on the output signal of the AC amplifier circuit 34B using the detection signal QDET as the detected signal. By this synchronous detection circuit 35B, the electrostatic leakage component included in the output signal of the AC amplifier circuit 34B is extracted. That is, the synchronous detection circuit 35B functions as a second synchronous detection circuit that synchronously detects the output signal of the AC amplifier circuit 34B, which is a signal based on the output signal of the addition circuit 33, and outputs a signal corresponding to the sum of the first electrostatic leakage component included in the first signal and the second electrostatic leakage component included in the second signal. The synchronous detection circuit 35B is, for example, a switch circuit that selects the output signal of the AC amplifier circuit 34B when the voltage level of the detection signal QDET is higher than the reference voltage V ref and selects a signal obtained by inverting the output signal of the AC amplifier circuit 34B with respect to the reference voltage V ref when the voltage level of the detection signal QDET is lower than the reference voltage V ref .

[0062] The smoothing circuit 36B smooths the output signal of the synchronous detection circuit 35B into a DC voltage signal. The output signal of the smoothing circuit 36B is output from the detection circuit 30 as the electrostatic leakage detection signal QAO. That is, the smoothing circuit 36B functions as a first failure diagnosis signal generation circuit that generates the electrostatic leakage detection signal QAO as a first failure diagnosis signal based on the output signal of the synchronous detection circuit 35B, which is a second synchronous detection circuit.

[0063] Thus, in this embodiment, the charge amplifier circuits 31A, 31B, the adder circuit 33, the AC amplifier circuit 34B, the synchronous detection circuit 35B, and the smoothing circuit 36B function as a first fault diagnosis signal output circuit that outputs an electrostatic leakage detection signal QAO, generated based on the first electrostatic leakage component and the second electrostatic leakage component, as a first fault diagnosis signal. Furthermore, the analog / digital conversion circuit 42, the digital signal processing circuit 52, and the fault diagnosis circuit 61 shown in Figure 1 function as a first fault diagnosis circuit that performs fault diagnosis based on the electrostatic leakage detection signal QAO, which is the first fault diagnosis signal.

[0064] 1-4. Examples of signal waveforms Figure 5 shows an example of the waveforms of various signals corresponding to the physical quantity components contained in the AC charge output from the physical quantity detection element 100. In Figure 5, the waveforms of the signals at points A to D shown in Figure 3 and the waveforms of the signals at points E to L shown in Figure 4 are shown. For each signal waveform, the horizontal axis represents time and the vertical axis represents voltage. Note that Figure 5 is an example where a constant angular velocity is applied to the physical quantity detection element 100.

[0065] The signal at point A is the output signal of the current-voltage conversion circuit 21, and the reference voltage V ref It is a signal with a constant frequency f centered around [a specific point].

[0066] The signal at point B is the output signal of the drive signal generation circuit 24, i.e., the drive signal, which is in phase with the signal at point A and has a constant amplitude V. c This is a square wave voltage signal. The signal at point B includes a first frequency component with frequency f, and a second frequency component with frequency 2f is superimposed on the high-level voltage.

[0067] The signal at point B' is the output signal of buffer circuit 26, i.e., the detected signal SDET, which is in phase with the signal at point A and has a constant amplitude V. d This is a square wave voltage signal.

[0068] The signal at point C is the output signal of the phase shift circuit 25, which has a phase lead of 90° relative to the signal at point B, and has a constant amplitude of V. cThis is a square wave voltage signal. The signal at point C contains a first frequency component with frequency f, and a second frequency component with frequency 2f is superimposed on the high-level voltage.

[0069] The signal at point D is the output signal of the EXNOR circuit 27, i.e., the detected signal QDET, which has twice the frequency of the signal at point A and a constant amplitude V. d This is a square wave voltage signal.

[0070] The signal at point E is the first physical quantity component included in the output signal of the charge amplifier circuit 31A, is in phase with the signal at point A, and is relative to the reference voltage V. ref It is a signal with a constant frequency f centered around [a specific point].

[0071] The signal at point F is the second physical quantity component included in the output signal of the charge amplifier circuit 31B, and its phase is 180° different from the signal at point A, and the reference voltage V ref This is a signal with a constant frequency f centered at point E. The first physical quantity component contained in the signal at point E and the second physical quantity component contained in the signal at point F are out of phase with each other and have substantially the same amplitude.

[0072] The signal at point G is a signal obtained by differential amplification of the physical quantity components contained in the output signal of the AC amplifier circuit 34A, namely the first physical quantity component contained in the signal at point E and the second physical quantity component contained in the signal at point F, and is in phase with the signal at point A, and is under reference voltage V ref It is a signal with a constant frequency f centered around [a specific point].

[0073] The signal at point H is detected by the SDET, which is the signal at point B', and the physical quantity component contained in the output signal of the synchronous detection circuit 35A, i.e., the physical quantity component contained in the signal at point G, is the reference voltage V. ref This is a signal that has been full-wave rectified based on [a specific reference point].

[0074] The signal at point I is a physical quantity component included in the output signal of the smoothing circuit 36A, and is a signal with a voltage value V1 corresponding to the physical quantity detected by the physical quantity detection element 100.

[0075] The signal at point J is a signal in which the physical quantity components contained in the output signal of the AC amplifier circuit 34B, namely the first physical quantity component contained in the signal at point E and the second physical quantity component contained in the signal at point F, have been added together and almost completely removed, and the voltage value is the reference voltage V ref This is the signal.

[0076] The signal at point K is detected by the detection signal QDET, which is the signal at point D, and the physical quantity component contained in the output signal of the synchronous detection circuit 35B, i.e., the physical quantity component contained in the signal at point J, is the reference voltage V. ref This is a signal that has been full-wave rectified with respect to the reference voltage V. ref This is the signal.

[0077] The signal at point L is a physical quantity component included in the output signal of the smoothing circuit 36B, and its voltage value is the reference voltage V ref This is the signal.

[0078] Figure 6 shows an example of the waveforms of various signals corresponding to the electrostatic leakage component contained in the AC charge output from the physical quantity detection element 100. In Figure 6, the waveforms of the signals at points A to D shown in Figure 3 and the waveforms of the signals at points E to L shown in Figure 4 are shown, and for each signal waveform, the horizontal axis is time and the vertical axis is voltage.

[0079] In Figure 6, the signals from points A to D are the same as in Figure 5.

[0080] The signal at point E is the first electrostatic leakage component included in the output signal of the charge amplifier circuit 31A, and the reference voltage V ref This is a signal with a constant frequency of 2f centered at point B. The first electrostatic leakage component is the second frequency component of frequency 2f superimposed on the high-level voltage of the signal at point B, which propagates to point E via the first electrostatic coupling capacitance C1 between the drive electrode 113 and the detection electrode 114. Therefore, the first electrostatic leakage component included in the signal at point E is in phase with the second frequency component of frequency 2f included in the signal at point B.

[0081] The signal at point F is the second electrostatic leakage component included in the output signal of the charge amplifier circuit 31B, and the reference voltage V ref The signal is a constant frequency 2f centered at point B. The second electrostatic leakage component is a second frequency component of frequency 2f superimposed on the high-level voltage of the signal at point B, which propagates to point F via the second electrostatic coupling capacitance C2 between the drive electrode 113 and the detection electrode 115. Therefore, the second electrostatic leakage component included in the signal at point F is in phase with the second frequency component of frequency 2f included in the signal at point B. The first electrostatic leakage component included in the signal at point E and the second electrostatic leakage component included in the signal at point F are in phase with each other and have substantially the same amplitude.

[0082] The signal at point G is a signal in which the electrostatic leakage components contained in the output signal of the AC amplifier circuit 34A, namely the first electrostatic leakage component contained in the signal at point E and the second electrostatic leakage component contained in the signal at point F, have been differentially amplified and are almost completely removed, and the voltage value is the reference voltage V ref This is the signal.

[0083] The signal at point H is the electrostatic leakage component contained in the output signal of the synchronous detection circuit 35A, i.e., the electrostatic leakage component contained in the signal at point G, which is the detected signal SDET at point B', and the reference voltage V ref This is a signal that has been full-wave rectified with respect to the reference voltage V. ref This is the signal.

[0084] The signal at point I is the electrostatic leakage component included in the output signal of the smoothing circuit 36A, and its voltage value is the reference voltage V ref This is the signal.

[0085] The signal at point J is the signal obtained by summing and amplified the electrostatic leakage components contained in the output signal of the AC amplifier circuit 34B, i.e., the first electrostatic leakage component contained in the signal at point E and the second electrostatic leakage component contained in the signal at point F. Therefore, the electrostatic leakage component contained in the signal at point J is in phase with the second frequency component of frequency 2f contained in the signal at point B, and the reference voltage V ref It is a signal with a constant frequency of 2f centered on [this point].

[0086] The signal at point K is the electrostatic leakage component contained in the output signal of the synchronous detection circuit 35B, i.e., the electrostatic leakage component contained in the signal at point J, which is the detected signal QDET at point D, and the reference voltage V ref This is a signal that has been full-wave rectified based on [a specific reference point].

[0087] The signal at point L is the electrostatic leakage component included in the output signal of the smoothing circuit 36B, and is a signal with a voltage value V2 corresponding to the electrostatic leakage generated in the physical quantity detection element 100.

[0088] In reality, each signal from point E to point L is the sum of the waveforms in Figure 5 and Figure 6. Here, the signal at point I in Figure 6 has a voltage value equal to the reference voltage V ref Since the signal is such that the output signal of the smoothing circuit 36A, i.e., the physical quantity detection signal SAO, contains almost no electrostatic leakage components and closely matches the signal at point I in Figure 5, resulting in a signal with a voltage level corresponding to the physical quantity components. Thus, since the physical quantity detection signal SAO contains almost no electrostatic leakage components, the adverse effect of electrostatic leakage components on the detection of physical quantities is extremely small. Therefore, the MCU 5 can measure the physical quantity applied to the physical quantity detection device 1 by reading out the physical quantity detection signal SDOX, which is generated based on the physical quantity detection signal SAO.

[0089] Furthermore, the signal at point L in Figure 5 has a voltage value equal to the reference voltage V ref Since the signal is such that the output signal of the smoothing circuit 36B, i.e., the electrostatic leakage detection signal QAO, contains almost no physical quantity components and is almost identical to the signal at point L in Figure 6, resulting in a signal with a voltage level corresponding to the electrostatic leakage component. Thus, since the electrostatic leakage detection signal QAO contains almost no physical quantity components, the adverse effect of physical quantity components on fault diagnosis based on electrostatic leakage components is extremely small. Furthermore, if the wiring of the physical quantity detection element 100 is normal, the voltage of the electrostatic leakage detection signal QAO will be a predetermined value. Therefore, the fault diagnosis circuit 61 can diagnose that the wiring of the physical quantity detection element 100 is faulty if the magnitude of the electrostatic leakage detection signal QDOX generated based on the electrostatic leakage detection signal QAO does not fall within a predetermined first range.

[0090] 1-5. Effects In the physical quantity detection device 1 of the first embodiment, if a fault such as a break or short circuit occurs in the wiring connected to the physical quantity detection element 100, the magnitudes of the first and second electrostatic leakage components, which are propagated to the detection electrodes 114 and 115 respectively by the second frequency component included in the drive signal, change. As a result, the value of the electrostatic leakage detection signal QDOX generated in the physical quantity detection circuit 200 based on the first and second electrostatic leakage components also changes. Therefore, according to the physical quantity detection device 1 of the first embodiment, the physical quantity detection circuit 200 can generate an electrostatic leakage detection signal QDOX that can be used for fault diagnosis of the wiring connected to the physical quantity detection element 100. For example, an external device, such as an MCU 5, can diagnose the fault in the wiring based on the electrostatic leakage detection signal QDOX.

[0091] Furthermore, in the physical quantity detection device 1 of the first embodiment, the physical quantity detection circuit 200 can generate an electrostatic leakage detection signal QDOX that can be used for fault diagnosis of the wiring connected to the physical quantity detection element 100 based on the electrostatic leakage component. Therefore, a physical quantity detection element 100 that has been tuned so that the vibration leakage component is zero or close to zero can be used. Accordingly, the physical quantity detection device 1 of the first embodiment can reduce the risk of the detection accuracy of the physical quantity being reduced due to the vibration leakage component.

[0092] Furthermore, according to the physical quantity detection device 1 of the first embodiment, the full-wave rectifier circuit 22 necessary for generating the drive signal can also be used as a circuit for generating a second frequency component necessary for fault diagnosis based on electrostatic leakage components, thus eliminating the need for a dedicated circuit for generating the second frequency component.

[0093] Furthermore, according to the physical quantity detection device 1 of the first embodiment, the physical quantity detection circuit 200 has a fault diagnosis circuit 61 that performs fault diagnosis based on the electrostatic leakage detection signal QDOX. Therefore, if a fault such as a break or short circuit occurs in the wiring connected to the physical quantity detection element 100, the electrostatic leakage detection signal QDOX changes, making it possible to diagnose the fault in the wiring.

[0094] Furthermore, in the physical quantity detection device 1 of the first embodiment, the physical quantity component included in the first signal output from the detection electrode 114 and the physical quantity component included in the second signal output from the detection electrode 115 are in opposite phases. Therefore, in the physical quantity detection circuit 200, the physical quantity component is amplified by the differential amplifier circuit 32 and attenuated by the adder circuit 33. Accordingly, according to the physical quantity detection device 1 of the first embodiment, the physical quantity detection circuit 200 can generate the physical quantity detection signal SDOX with high accuracy, and the risk of the accuracy of the electrostatic leakage detection signal QDOX being reduced by the physical quantity component is reduced.

[0095] Furthermore, in the physical quantity detection device 1 of the first embodiment, the first electrostatic leakage component included in the first signal and the second electrostatic leakage component included in the second signal are in phase with each other. Therefore, in the physical quantity detection circuit 200, the electrostatic leakage component is amplified by the summing circuit 33 and attenuated by the differential amplifier circuit 32. Accordingly, according to the physical quantity detection device 1 of the first embodiment, the physical quantity detection circuit 200 can generate the electrostatic leakage detection signal QDOX with high accuracy, and the risk of the accuracy of the physical quantity detection signal SDOX being reduced by the electrostatic leakage component is reduced.

[0096] 2. Second Embodiment Regarding the physical quantity detection device 1 of the second embodiment, the same reference numerals are used for components similar to those in the first embodiment, and explanations that overlap with those of the first embodiment are omitted or simplified. The main points to be described are those that differ from the first embodiment.

[0097] Figure 7 is a functional block diagram of the physical quantity detection device of the second embodiment. As shown in Figure 7, the physical quantity detection device 1 of the second embodiment comprises a physical quantity detection element 100 and a physical quantity detection circuit 200. The configuration and function of the physical quantity detection element 100 are the same as in the first embodiment, so a description is omitted.

[0098] As mentioned above, by tuning the weights of the four weights 103 of the physical quantity detection element 100, leakage vibrations will hardly occur if the physical quantity detection element 100 is functioning correctly. However, if the physical quantity detection element 100 fails, for example, if a crack occurs in at least one of the drive vibration arms 101a, 101b and the detection vibration arm 102, the balance of vibration energy of the drive vibration arms 101a and 101b will be disrupted, causing leakage vibrations. Therefore, if the physical quantity detection element 100 fails, it will output an alternating current charge based on leakage vibrations from the detection electrodes 114 and 115. Hereafter, the alternating current charge based on leakage vibrations may also be referred to as the "vibration leakage component."

[0099] As shown in Figure 7, the physical quantity detection circuit 200 in the second embodiment includes, similar to the first embodiment, a reference voltage circuit 10, a drive circuit 20, a detection circuit 30, an analog-to-digital conversion circuit 41, an analog-to-digital conversion circuit 42, a digital signal processing circuit 51, a digital signal processing circuit 52, a fault diagnosis circuit 61, an interface circuit 70, a storage unit 80, and an oscillator circuit 90. Furthermore, the physical quantity detection circuit 200 in the second embodiment includes a selector 40, a control circuit 60, and a fault diagnosis circuit 62. The physical quantity detection circuit 200 may be implemented, for example, as a single-chip integrated circuit. Note that the physical quantity detection circuit 200 may also have a configuration in which some of these elements are omitted or changed, or other elements are added.

[0100] The functions of the reference voltage circuit 10, analog / digital conversion circuit 41, digital signal processing circuit 51, fault diagnosis circuit 61, memory unit 80, and oscillation circuit 90 are the same as in the first embodiment, so their description is omitted.

[0101] The drive circuit 20 has the same functions as in the first embodiment, and further generates a detection signal VDET that is 90° out of phase with the drive signal, and outputs it to the detection circuit 30.

[0102] The detection circuit 30 has the same functions as the first embodiment, and further outputs a vibration leakage detection signal VAO based on a first vibration leakage component included in the first signal output from the detection electrode 114 of the physical quantity detection element 100 and a second vibration leakage component included in the second signal output from the detection electrode 115 of the physical quantity detection element 100. As described above, the first signal is an AC charge input via the S1 terminal of the physical quantity detection circuit 200, and the second signal is an AC charge input via the S2 terminal of the physical quantity detection circuit 200. The first vibration leakage component is a component based on the vibration of the physical quantity detection element 100 and is included in the first signal when the physical quantity detection element 100 fails. Similarly, the second vibration leakage component is a component based on the vibration of the physical quantity detection element 100 and is included in the second signal when the physical quantity detection element 100 fails. The detection circuit 30 uses the detected signal VDET to detect vibration leakage components based on the first vibration leakage component contained in the first signal and the second vibration leakage component contained in the second signal, and generates and outputs a vibration leakage detection signal VAO, which is an analog signal with a voltage level corresponding to the magnitude of the detected vibration leakage component.

[0103] The selector 40 selects the electrostatic leakage detection signal QAO and the vibration leakage detection signal VAO in a time-division manner according to the control signal output from the control circuit 60 and outputs them to the analog / digital conversion circuit 42.

[0104] The analog-to-digital conversion circuit 42 operates based on the clock signal ADCLK generated by the oscillation circuit 90, and converts the electrostatic leakage detection signal QAO and the vibration leakage detection signal VAO, which are analog signals output in time division from the selector 40, into digital signals QDO and VDO, respectively, in time division division and outputs them.

[0105] The digital signal processing circuit 52 operates based on the master clock signal MCLK generated by the oscillation circuit 90, and performs predetermined calculations on the electrostatic leakage detection signal QDO and vibration leakage detection signal VDO output in time division from the analog / digital conversion circuit 42, and outputs the electrostatic leakage detection signal QDOX and vibration leakage detection signal VDOX obtained from the calculations.

[0106] The fault diagnosis circuit 62 operates using the master clock signal MCLK and diagnoses a fault in the physical quantity detection device 1 based on the vibration leakage detection signal VDOX. The fault diagnosis circuit 62 then outputs a fault diagnosis result signal VF indicating whether or not the physical quantity detection device 1 is faulty. If the physical quantity detection device 1 is functioning normally, the value of the vibration leakage detection signal VDOX falls within a predetermined second range. In contrast, if, for example, a part of the physical quantity detection element 100 is damaged, the value of the vibration leakage detection signal VDOX falls outside the second range. Therefore, the fault diagnosis circuit 62 may diagnose the physical quantity detection device 1 as faulty if the value of the vibration leakage detection signal VDOX does not fall within the second range. For example, the second range may include a predetermined value that is designed to function normally when the physical quantity detection device 1 is functioning normally, as well as a range that may change from that predetermined value over time. The second range may also be fixed or variable. For example, the second range may be set variably according to a value stored in a register of the memory unit 80 that can be rewritten from outside the physical quantity detection circuit 200.

[0107] The control circuit 60 operates in accordance with the master clock signal MCLK and generates control signals to control the operation of the selector 40, as well as enable signals to operate the fault diagnosis circuits 61 and 62, respectively.

[0108] The interface circuit 70 has the same functions as in the first embodiment, and may also output the electrostatic leakage detection signal QDOX and the vibration leakage detection signal VDOX, which are time-division output from the digital signal processing circuit 52, to the MCU 5 in response to a request from the MCU 5. In this case, the physical quantity detection circuit 200 does not have a fault diagnosis circuit 62, and the MCU 5 may perform fault diagnosis similar to that of the fault diagnosis circuit 62 based on the vibration leakage detection signal VDOX. The MCU 5 may also write a value to a predetermined register to set the second range described above.

[0109] In the physical quantity detection device 1 of the second embodiment configured as described above, the physical quantity detection element 100 outputs a first signal, which is an alternating current charge generated at the detection electrode 114, and a second signal, which is an alternating current charge generated at the detection electrode 115. The physical quantity detection circuit 200 generates a physical quantity detection signal SDOX corresponding to the physical quantity detected by the physical quantity detection element 100, based on the first and second signals output from the physical quantity detection element 100. The physical quantity detection circuit 200 also generates fault diagnosis result signals QF and VF indicating whether or not there is a malfunction in the physical quantity detection device 1, based on the first and second signals output from the physical quantity detection element 100.

[0110] Figure 8 shows an example of the configuration of the drive circuit 20 in the second embodiment. As shown in Figure 8, the drive circuit 20 in the second embodiment includes a current-voltage conversion circuit 21, a full-wave rectifier circuit 22, an auto-gain control circuit 23, a drive signal generation circuit 24, a phase shift circuit 25, a buffer circuit 26, an EXNOR circuit 27, and a buffer circuit 28, similar to the first embodiment. The functions of the current-voltage conversion circuit 21, the full-wave rectifier circuit 22, the auto-gain control circuit 23, the drive signal generation circuit 24, the phase shift circuit 25, the buffer circuit 26, and the EXNOR circuit 27 are the same as in the first embodiment, so their description is omitted. The buffer circuit 26 outputs a detection signal VDET that is in phase with the output signal of the phase shift circuit 25. The detection signal VDET is a square wave voltage signal with a frequency f whose phase is 90° ahead of the detection signal SDET, and is supplied to the detection circuit 30 together with the detection signals SDET and QDET.

[0111] Figure 9 shows an example of the configuration of the detection circuit 30 in the second embodiment. As shown in Figure 9, the detection circuit 30 in the second embodiment includes charge amplifier circuits 31A, 31B, differential amplifier circuit 32, adder circuit 33, AC amplifier circuits 34A, 34B, synchronous detection circuits 35A, 35B, and smoothing circuits 36A, 36B, similar to the first embodiment. The functions of the charge amplifier circuits 31A, 31B, differential amplifier circuit 32, adder circuit 33, AC amplifier circuits 34A, 34B, synchronous detection circuits 35A, 35B, and smoothing circuits 36A, 36B are the same as in the first embodiment, so their description is omitted. Furthermore, the detection circuit 30 in the second embodiment includes a synchronous detection circuit 35C and a smoothing circuit 36C.

[0112] The first signal input to the charge amplifier circuit 31A via terminal S1 includes a first physical quantity component and a first electrostatic leakage component, and if the physical quantity detection element 100 fails, it further includes a first vibration leakage component. Similarly, the second signal input to the charge amplifier circuit 31B via terminal S2 includes a second physical quantity component and a second electrostatic leakage component, and if the physical quantity detection element 100 fails, it further includes a second vibration leakage component.

[0113] In this embodiment, when the physical quantity detection element 100 fails, the first vibration leakage component included in the first signal and the second vibration leakage component included in the second signal are in phase with each other. Here, the statement that the first vibration leakage component included in the first signal and the second vibration leakage component included in the second signal are in phase with each other includes not only the case where the phase difference between the two vibration leakage components is exactly 0°, but also the case where the phase difference between the two vibration leakage components has a slight difference from 0° due to manufacturing errors in the physical quantity detection element 100, errors in the delay time of the signal propagation path, etc.

[0114] Since the first vibration leakage component in the first signal and the second vibration leakage component in the second signal are in phase with each other, the vibration leakage component is attenuated by the differential amplifier circuit 32. Therefore, even if the physical quantity detection element 100 fails, the influence of the vibration leakage component on the physical quantity component in the output signal of the differential amplifier circuit 32 is reduced. In order to substantially eliminate the influence of the vibration leakage component on the physical quantity component in the output signal of the differential amplifier circuit 32, it is preferable that the difference between the first vibration leakage component and the second vibration leakage component is substantially zero. The statement that the difference between the first vibration leakage component and the second vibration leakage component is substantially zero means that not only is the difference amount exactly zero, but also that the difference amount has a slight difference from zero due to the minimum adjustment resolution of the first vibration leakage component and the second vibration leakage component, etc., or that the measured value has a slight difference from zero due to the measurement error of the difference amount between the first vibration leakage component and the second vibration leakage component.

[0115] Furthermore, since the first vibration leakage component contained in the first signal and the second vibration leakage component contained in the second signal are in phase with each other, the vibration leakage component is amplified by the summing circuit 33 and further amplified by the AC amplification circuit 34B.

[0116] The synchronous detection circuit 35C uses the output signal of the AC amplifier circuit 34B as the signal to be detected and performs synchronous detection using the detected signal VDET. This synchronous detection circuit 35B extracts the vibration leakage component contained in the output signal of the AC amplifier circuit 34B.

[0117] In other words, the synchronous detection circuit 35C functions as a third synchronous detection circuit that synchronously detects the output signal of the AC amplifier circuit 34B, which is a signal based on the output signal of the summer circuit 33, and outputs a signal corresponding to the sum of the first vibration leakage component contained in the first signal and the second vibration leakage component contained in the second signal. For example, the synchronous detection circuit 35C is configured such that the voltage level of the detected signal VDET is equal to the reference voltage V ref When the voltage level is higher than the reference voltage V, the output signal of the AC amplifier circuit 34B is selected, and the voltage level of the detected signal VDET is equal to the reference voltage V. ref When the value is lower than the reference voltage V, the output signal of the AC amplifier circuit 34B is sent to the reference voltage V. refA switch circuit that selects the inverted signal may also be used.

[0118] The smoothing circuit 36C smooths the output signal of the synchronous detection circuit 35C into a DC voltage signal. The output signal of the smoothing circuit 36C is output from the detection circuit 30 as a vibration leakage detection signal VAO. In other words, the smoothing circuit 36C functions as a second fault diagnosis signal generation circuit that generates the vibration leakage detection signal VAO as a second fault diagnosis signal based on the output signal of the synchronous detection circuit 35C, which is the third synchronous detection circuit.

[0119] Thus, in this embodiment, the charge amplifier circuits 31A, 31B, the adder circuit 33, the AC amplifier circuit 34B, the synchronous detection circuit 35B, and the smoothing circuit 36B function as a first fault diagnosis signal output circuit that outputs an electrostatic leakage detection signal QAO, generated based on the first electrostatic leakage component and the second electrostatic leakage component, as a first fault diagnosis signal. Furthermore, the charge amplifier circuits 31A, 31B, the adder circuit 33, the AC amplifier circuit 34B, the synchronous detection circuit 35C, and the smoothing circuit 36C function as a second fault diagnosis signal output circuit that outputs a vibration leakage detection signal VAO, generated based on the first vibration leakage component and the second vibration leakage component, as a second fault diagnosis signal. In addition, the analog / digital conversion circuit 42, the digital signal processing circuit 52, and the fault diagnosis circuit 61 shown in Figure 7 function as a first fault diagnosis circuit that performs fault diagnosis based on the electrostatic leakage detection signal QAO, which is the first fault diagnosis signal. Furthermore, the analog / digital conversion circuit 42, the digital signal processing circuit 52, and the fault diagnosis circuit 62 shown in Figure 7 function as a second fault diagnosis circuit that performs fault diagnosis based on the vibration leakage detection signal VAO, which is a second fault diagnosis signal.

[0120] Figure 10 shows an example of the waveforms of various signals corresponding to the physical quantity components contained in the AC charge output from the physical quantity detection element 100. In Figure 10, the waveforms of the signals at points A to D shown in Figure 8 and the waveforms of the signals at points E to N shown in Figure 9 are shown. For each signal waveform, the horizontal axis represents time and the vertical axis represents voltage. Note that Figure 10 is an example where a constant angular velocity is applied to the physical quantity detection element 100.

[0121] In Figure 10, the signals from points A to C and from points D to L are the same as in Figure 5.

[0122] The signal at point C' is the output signal of buffer circuit 28, i.e., the detected signal VDET, which has a phase lead of 90° relative to the signal at point A and a constant amplitude V d This is a square wave voltage signal.

[0123] The signal at point M is detected by the detection signal VDET, which is the signal at point C', and the physical quantity component contained in the output signal of the synchronous detection circuit 35C, i.e., the physical quantity component contained in the signal at point J, is the reference voltage V ref This is a signal that has been full-wave rectified with respect to the reference voltage V. ref This is the signal.

[0124] The N-point signal is a physical quantity component included in the output signal of the smoothing circuit 36C, and its voltage value is the reference voltage V ref This is the signal.

[0125] Figure 11 shows an example of the waveforms of various signals corresponding to the electrostatic leakage component contained in the AC charge output from the physical quantity detection element 100. In Figure 11, the waveforms of the signals at points A to D shown in Figure 8 and the waveforms of the signals at points E to N shown in Figure 9 are shown, and for each signal waveform, the horizontal axis is time and the vertical axis is voltage.

[0126] In Figure 11, the signals from points A to C and from points D to L are the same as in Figure 6. Also, the signal at point C' is the same as in Figure 10.

[0127] The signal at point M is the electrostatic leakage component contained in the output signal of the synchronous detection circuit 35C, i.e., the electrostatic leakage component contained in the signal at point J, which is the detected signal VDET at point C', and the reference voltage V ref This is a signal that has been full-wave rectified based on [a specific reference point].

[0128] The signal at point N is the electrostatic leakage component included in the output signal of the smoothing circuit 36B, and is a signal with a voltage value V3 corresponding to the electrostatic leakage generated in the physical quantity detection element 100.

[0129] Figure 12 shows an example of the waveforms of various signals corresponding to the vibration leakage component in the AC charge output from the physical quantity detection element 100 when the physical quantity detection element 100 fails. In Figure 12, the waveforms of the signals at points A to D shown in Figure 8 and the waveforms of the signals at points E to N shown in Figure 9 are shown, and for each signal waveform, the horizontal axis is time and the vertical axis is voltage.

[0130] In Figure 12, the signals from points A to D are the same as those in Figures 10 and 11.

[0131] The signal at point E is the first vibration leakage component included in the output signal of the charge amplifier circuit 31A, which leads the signal at point A by 90° in phase, and is at the reference voltage V ref It is a signal with a constant frequency f centered around [a specific point].

[0132] The signal at point F is the second vibration leakage component included in the output signal of the charge amplifier circuit 31B, which leads the signal at point A by 90° in phase, and is at the reference voltage V ref This is a signal with a constant frequency f centered at point E. The first vibration leakage component in the signal at point E and the second vibration leakage component in the signal at point F are in phase with each other and have substantially the same amplitude.

[0133] The signal at point G is a signal in which the vibration leakage components contained in the output signal of the AC amplifier circuit 34A, namely the first vibration leakage component contained in the signal at point E and the second vibration leakage component contained in the signal at point F, have been differentially amplified and are almost completely removed, and the voltage value is the reference voltage V ref This is the signal.

[0134] The signal at point H is the vibration leakage component contained in the output signal of the synchronous detection circuit 35A, i.e., the vibration leakage component contained in the signal at point G, which is the reference voltage V of the detected signal SDET at point B'. ref This is a signal that has been full-wave rectified with respect to the reference voltage V. ref This is the signal.

[0135] The signal at point I is the oscillating leakage component included in the output signal of the smoothing circuit 36A, and its voltage value is the reference voltage V ref This is the signal.

[0136] The signal at point J is a signal obtained by summing and amplified the vibration leakage component contained in the output signal of the AC amplifier circuit 34B, the first vibration leakage component contained in the signal at point E, and the second vibration leakage component contained in the signal at point F, and its phase leads the signal at point A by 90°, and the reference voltage V ref It is a signal with a constant frequency f centered around [a specific point].

[0137] The signal at point K is the vibration leakage component contained in the output signal of the synchronous detection circuit 35B, i.e., the vibration leakage component contained in the signal at point J, which is the detected signal QDET at point D, and the reference voltage V ref This is a signal that has been full-wave rectified based on [a specific reference point].

[0138] The signal at point L is the oscillating leakage component included in the output signal of the smoothing circuit 36B, and its voltage value is the reference voltage V ref This is the signal.

[0139] The signal at point M is the vibration leakage component contained in the output signal of the synchronous detection circuit 35C, i.e., the vibration leakage component contained in the signal at point J, which is the detected signal VDET at point C', and the reference voltage V ref This is a signal that has been full-wave rectified based on [a specific reference point].

[0140] The signal at point N is the vibration leakage component included in the output signal of the smoothing circuit 36C, and is a signal with a voltage value V4 corresponding to the vibration leakage that occurred in the physical quantity detection element 100.

[0141] In reality, each signal from point E to point N is the sum of the waveforms in Figure 10, Figure 11, and Figure 12. Here, the voltage value of the signal at point I in Figure 11 and the signal at point I in Figure 12 are both the reference voltage V refSince the signal is such that the output signal of the smoothing circuit 36A, i.e., the physical quantity detection signal SAO, contains almost no electrostatic leakage components and vibration leakage components, and is almost identical to the signal at point I in Figure 10, resulting in a signal with a voltage level corresponding to the physical quantity component. Thus, since the physical quantity detection signal SAO contains almost no electrostatic leakage components and vibration leakage components, the adverse effect of these components on the detection of physical quantities is extremely small. Therefore, the MCU 5 can measure the physical quantity applied to the physical quantity detection device 1 by reading out the physical quantity detection signal SDOX, which is generated based on the physical quantity detection signal SAO.

[0142] Furthermore, the voltage values ​​of the signal at point L in Figure 10 and the signal at point L in Figure 12 are both the same as the reference voltage V. ref Since the signal is such that the output signal of the smoothing circuit 36B, i.e., the electrostatic leakage detection signal QAO, contains almost no physical quantity components and vibration leakage components, and is almost identical to the signal at point L in Figure 11, resulting in a signal with a voltage level corresponding to the electrostatic leakage component. Thus, since the electrostatic leakage detection signal QAO contains almost no physical quantity components and vibration leakage components, the adverse effect of the physical quantity components on fault diagnosis based on the electrostatic leakage component is extremely small. Furthermore, if the wiring of the physical quantity detection element 100 is normal, the voltage of the electrostatic leakage detection signal QAO will be a predetermined value. Therefore, the fault diagnosis circuit 61 can diagnose that the wiring of the physical quantity detection element 100 is faulty if the magnitude of the electrostatic leakage detection signal QDOX generated based on the electrostatic leakage detection signal QAO does not fall within a predetermined first range.

[0143] Furthermore, the signals at point N in Figure 10 have voltage values ​​corresponding to the reference voltage V refSince the signal is a static electricity signal, the output signal of the smoothing circuit 36B, i.e., the vibration leakage detection signal VAO, contains almost no physical quantity components. However, since the signal at point N in Figure 11 is a voltage value V3 signal, the vibration leakage detection signal VAO contains an electrostatic leakage component. Therefore, the vibration leakage detection signal VAO becomes a signal with a voltage level corresponding to the vibration leakage component, with the voltage value V3 as the reference. Thus, since the vibration leakage detection signal VAO contains almost no physical quantity components, the adverse effect of the physical quantity components on fault diagnosis based on vibration leakage components is extremely small. Furthermore, although the vibration leakage detection signal VAO contains an electrostatic leakage component, if the wiring of the physical quantity detection element 100 is normal, the magnitude of the electrostatic leakage component is constant, so the adverse effect of the electrostatic leakage component on fault diagnosis based on vibration leakage components is small. And, if the physical quantity detection element 100 is normal, the voltage of the vibration leakage detection signal VAO will be a predetermined value. Therefore, the fault diagnosis circuit 62 can diagnose that the physical quantity detection element 100 is faulty if the magnitude of the vibration leakage detection signal VDOX, which is generated based on the vibration leakage detection signal VAO, does not fall within the second range.

[0144] As described above, in the physical quantity detection device 1 of the second embodiment, if a fault such as a break or short circuit occurs in the wiring connected to the physical quantity detection element 100, the magnitudes of the first electrostatic leakage component and the second electrostatic leakage component, which are propagated to the detection electrodes 114 and 115 respectively by the second frequency component included in the drive signal, change. As a result, the value of the electrostatic leakage detection signal QDOX generated in the physical quantity detection circuit 200 based on the first electrostatic leakage component and the second electrostatic leakage component also changes. Therefore, according to the physical quantity detection device 1 of the first embodiment, the physical quantity detection circuit 200 can generate an electrostatic leakage detection signal QDOX that can be used for fault diagnosis of the wiring connected to the physical quantity detection element 100. For example, an external device, such as an MCU 5, can diagnose a fault in the wiring based on the electrostatic leakage detection signal QDOX.

[0145] Furthermore, in the physical quantity detection device 1 of the second embodiment, the physical quantity detection circuit 200 can generate an electrostatic leakage detection signal QDOX that can be used for fault diagnosis of the wiring connected to the physical quantity detection element 100 based on the electrostatic leakage component. Therefore, a physical quantity detection element 100 that has been tuned so that the vibration leakage component is zero or close to zero can be used. Accordingly, the physical quantity detection device 1 of the second embodiment can reduce the risk of the detection accuracy of the physical quantity being reduced due to the vibration leakage component.

[0146] Furthermore, in the physical quantity detection device 1 of the second embodiment, if a malfunction such as damage occurs in the physical quantity detection element 100, the magnitudes of the first vibration leakage component and the second vibration leakage component generated in the detection electrodes 114 and 115, respectively, based on the vibration of the physical quantity detection element 100 change. As a result, the value of the vibration leakage detection signal VDOX generated in the physical quantity detection circuit 200 based on the first vibration leakage component and the second vibration leakage component also changes. Therefore, according to the physical quantity detection device 1 of the second embodiment, the physical quantity detection circuit 200 can generate a vibration leakage detection signal VDOX that can be used for fault diagnosis of the physical quantity detection element 100. For example, an external device, such as the MCU 5, can diagnose a malfunction of the physical quantity detection element 100 based on the vibration leakage detection signal VDOX.

[0147] Furthermore, according to the physical quantity detection device 1 of the second embodiment, the physical quantity detection circuit 200 has a fault diagnosis circuit 62 that performs fault diagnosis based on the vibration leakage detection signal VDOX. Therefore, if a fault such as damage occurs in the physical quantity detection element 100, the electrostatic leakage detection signal QDOX changes, making it possible to diagnose the fault of the physical quantity detection element 100.

[0148] Furthermore, in the physical quantity detection device 1 of the second embodiment, the physical quantity component included in the first signal output from the detection electrode 114 and the physical quantity component included in the second signal output from the detection electrode 115 are in opposite phases. Therefore, in the physical quantity detection circuit 200, the physical quantity component is amplified by the differential amplifier circuit 32 and attenuated by the adder circuit 33. Accordingly, according to the physical quantity detection device 1 of the second embodiment, the physical quantity detection circuit 200 can generate the physical quantity detection signal SDOX with high accuracy, and the risk of the accuracy of the electrostatic leakage detection signal QDOX and the electrostatic leakage detection signal QDOX being reduced by the physical quantity component is reduced.

[0149] Furthermore, in the physical quantity detection device 1 of the second embodiment, since the first electrostatic leakage component included in the first signal and the second electrostatic leakage component included in the second signal are in phase with each other, in the physical quantity detection circuit 200, the electrostatic leakage component is amplified by the adder circuit 33 and attenuated by the differential amplifier circuit 32. Accordingly, according to the physical quantity detection device 1 of the second embodiment, the physical quantity detection circuit 200 can generate the electrostatic leakage detection signal QDOX with high accuracy, and the risk of the accuracy of the physical quantity detection signal SDOX being reduced by the electrostatic leakage component is reduced.

[0150] Furthermore, in the physical quantity detection device 1 of the second embodiment, since the first vibration leakage component included in the first signal and the second vibration leakage component included in the second signal are in phase with each other, in the physical quantity detection circuit 200, the vibration leakage component is amplified by the summing circuit 33 and attenuated by the differential amplifier circuit 32. Therefore, according to the physical quantity detection device 1 of the second embodiment, the physical quantity detection circuit 200 can generate the vibration leakage detection signal VDOX with high accuracy, and the risk of the accuracy of the physical quantity detection signal SDOX being reduced by the vibration leakage component is reduced.

[0151] 3. Variant The present invention is not limited to this embodiment, and various modifications can be implemented within the scope of the gist of the present invention.

[0152] For example, in each of the above embodiments, the physical quantity detection device 1 performs the physical quantity detection process and the fault diagnosis signal generation process simultaneously, but the physical quantity detection process and the fault diagnosis signal generation process may be performed exclusively. For example, the physical quantity detection device 1 may perform the physical quantity detection process but not the fault diagnosis signal generation process in normal operation mode, and may perform the fault diagnosis signal generation process without performing the physical quantity detection process in fault diagnosis mode.

[0153] Furthermore, in each of the above embodiments, the physical quantity detection device 1 generates a fault diagnosis signal by detecting an electrostatic leakage component propagated to the detection electrodes 114 and 115, where the second frequency component has a frequency twice that of the first frequency component included in the drive signal. However, it is also possible to generate a fault diagnosis signal by detecting an electrostatic leakage component propagated to the detection electrodes 114 and 115, where the frequency component is an even or odd multiple other than twice that of the first frequency component included in the drive signal.

[0154] Furthermore, in each of the above embodiments, the physical quantity detection circuit 200 outputs the physical quantity detection signal SDOX and the electrostatic leakage detection signal QDOX, which are digital signals, via the interface circuit 70. However, the physical quantity detection signal SAO and the electrostatic leakage detection signal QAO, which are analog signals, may also be output via an external terminal. Similarly, in the second embodiment described above, the physical quantity detection circuit 200 outputs the vibration leakage detection signal VDOX, which is a digital signal, via the interface circuit 70. However, the vibration leakage detection signal VAO, which is an analog signal, may also be output via an external terminal.

[0155] Furthermore, in the first embodiment described above, the analog / digital conversion circuit 41 converts the physical quantity detection signal SAO to the physical quantity detection signal SDO, and the analog / digital conversion circuit 42 converts the electrostatic leakage detection signal QAO to the electrostatic leakage detection signal QDO. However, a single analog / digital conversion circuit may perform the conversion of the physical quantity detection signal SAO to the physical quantity detection signal SDO and the conversion of the electrostatic leakage detection signal QAO to the electrostatic leakage detection signal QDO in a time-division manner. Furthermore, in the second embodiment described above, the analog / digital conversion circuit 41 converts the physical quantity detection signal SAO to the physical quantity detection signal SDO, and the analog / digital conversion circuit 42 performs the conversion of the electrostatic leakage detection signal QAO to the electrostatic leakage detection signal QDO and the conversion of the vibration leakage detection signal VAO to the vibration leakage detection signal VDO in a time-division manner. However, a single analog / digital conversion circuit may perform the conversion of the physical quantity detection signal SAO to the physical quantity detection signal SDO, the conversion of the electrostatic leakage detection signal QAO to the electrostatic leakage detection signal QDO, and the conversion of the vibration leakage detection signal VAO to the vibration leakage detection signal VDO in a time-division manner. Alternatively, the analog / digital conversion circuit 42 may convert the electrostatic leakage detection signal QAO into an electrostatic leakage detection signal QDO, and a different analog / digital conversion circuit from the analog / digital conversion circuits 41 and 42 may convert the vibration leakage detection signal VAO into a vibration leakage detection signal VDO.

[0156] Furthermore, in the first embodiment described above, the digital signal processing circuit 51 performs a predetermined calculation on the physical quantity detection signal SDO to generate the physical quantity detection signal SDOX, and the digital signal processing circuit 52 performs a predetermined calculation on the electrostatic leakage detection signal QDO to generate the electrostatic leakage detection signal QDOX. However, a single digital signal processing circuit may perform the process of generating the physical quantity detection signal SDOX and the process of generating the electrostatic leakage detection signal QDOX in a time-division manner. Furthermore, in the second embodiment described above, the digital signal processing circuit 51 performs a predetermined calculation on the physical quantity detection signal SDO to generate the physical quantity detection signal SDOX, and the digital signal processing circuit 52 performs a predetermined calculation on the electrostatic leakage detection signal QDO to generate the electrostatic leakage detection signal QDOX and a predetermined calculation on the vibration leakage detection signal VDO to generate the vibration leakage detection signal VDOX in a time-division manner. However, a single digital signal processing circuit may perform the process of generating the physical quantity detection signal SDOX, the process of generating the electrostatic leakage detection signal QDOX, and the process of generating the vibration leakage detection signal VDOX in a time-division manner. Alternatively, the digital signal processing circuit 52 may generate an electrostatic leakage detection signal QDOX, and a digital signal processing circuit different from the digital signal processing circuits 51 and 52 may generate a vibration leakage detection signal VDOX.

[0157] Furthermore, in each of the above embodiments, the physical quantity detection device 1 includes a physical quantity detection element 100 that detects angular velocity as a physical quantity, but it may also include a physical quantity detection element that detects physical quantities other than angular velocity. For example, the physical quantity detection device 1 may include a physical quantity detection element that detects physical quantities such as acceleration, angular acceleration, velocity, and force.

[0158] Furthermore, in each of the above embodiments, the physical quantity detection device 1 includes one physical quantity detection element, but it may also include multiple physical quantity detection elements. For example, the physical quantity detection device 1 may include multiple physical quantity detection elements, and each of the multiple physical quantity detection elements may detect a physical quantity using one of two or more mutually orthogonal axes as the detection axis. Alternatively, for example, the physical quantity detection device 1 may include multiple physical quantity detection elements, and each of the multiple physical quantity detection elements may detect one of several types of physical quantities such as angular velocity, acceleration, angular acceleration, speed, and force. In other words, the physical quantity detection device 1 may be a composite sensor.

[0159] Furthermore, in the embodiments described above, examples were given in which the vibrating element of the physical quantity detection element 100 is a double T-shaped quartz vibrating element. However, the vibrating element of a physical quantity detection element that detects various physical quantities may be, for example, a tuning fork type or a comb-tooth type, or a sound-piece type with a triangular prism, square prism, cylindrical shape, etc. Also, instead of quartz (SiO2), piezoelectric materials such as piezoelectric single crystals of lithium tantalate (LiTaO3) or lithium niobate (LiNbO3) or piezoelectric ceramics of lead zirconate titanate (PZT) may be used as the material for the vibrating element of the physical quantity detection element, or silicon semiconductors may be used. In addition, the vibrating element of the physical quantity detection element may have a structure in which a piezoelectric thin film of zinc oxide (ZnO) or aluminum nitride (AlN) sandwiched between driving electrodes is arranged on a part of the surface of a silicon semiconductor. For example, the physical quantity detection element may be a MEMS element. MEMS is an abbreviation for Micro Electro Mechanical Systems.

[0160] Furthermore, although a piezoelectric type physical quantity detection element was exemplified in the above embodiment, the physical quantity detection element for detecting various physical quantities is not limited to piezoelectric type elements, but may also be capacitive type, electrodynamic type, eddy current type, optical type, strain gauge type, etc. Also, the detection method of the physical quantity detection element is not limited to vibration type, but may be optical type, rotation type, fluid type, etc.

[0161] The embodiments and variations described above are examples only and are not limited thereto. For example, each embodiment and each variation can be combined as appropriate.

[0162] The present invention includes configurations substantially identical to those described in the embodiments, for example, configurations with the same function, method, and results, or configurations with the same purpose and effect. Furthermore, the present invention includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as those described in the embodiments. Finally, the present invention includes configurations that add known technology to the configurations described in the embodiments.

[0163] The following can be derived from the embodiments and modifications described above.

[0164] One embodiment of a physical quantity detection circuit is: A drive circuit that applies a drive signal including a first frequency component for driving a physical quantity detection element to the drive electrode of a physical quantity detection element that detects a physical quantity, A physical quantity detection signal output circuit outputs a physical quantity detection signal corresponding to the physical quantity based on the first physical quantity component included in the first signal output from the first detection electrode of the physical quantity detection element and the second physical quantity component included in the second signal output from the second detection electrode of the physical quantity detection element, when the drive signal is applied to the physical quantity detection element. It has a first fault diagnosis signal output circuit, The drive signal includes a second frequency component having a frequency different from that of the first frequency component. The first signal includes a first electrostatic leakage component, which is a component of the second frequency component propagating to the first detection electrode via a first electrostatic coupling capacitance between the drive electrode and the first detection electrode. The second signal includes a second electrostatic leakage component, which is a component obtained when the second frequency component propagates to the second detection electrode via the second electrostatic coupling capacitance between the drive electrode and the second detection electrode. The first fault diagnosis signal output circuit outputs a first fault diagnosis signal generated based on the first electrostatic leakage component and the second electrostatic leakage component.

[0165] In this physical quantity detection circuit, if a fault such as a break or short circuit occurs in the wiring connected to the physical quantity detection element, the magnitude of the first and second electrostatic leakage components, which are propagated by the second frequency component included in the drive signal to the first and second detection electrodes respectively, changes. As a result, the first fault diagnosis signal generated based on the first and second electrostatic leakage components also changes. Therefore, this physical quantity detection circuit can generate a first fault diagnosis signal that can be used to diagnose faults in the wiring connected to the physical quantity detection element. For example, an external device can diagnose a fault in the wiring based on the first fault diagnosis signal.

[0166] Furthermore, this physical quantity detection circuit can generate a first fault diagnosis signal that can be used to diagnose faults in the wiring connected to the physical quantity detection element based on the electrostatic leakage component. Therefore, a physical quantity detection element tuned to have zero or near-zero vibration leakage component can be connected. Consequently, this physical quantity detection circuit can reduce the risk of decreased accuracy in detecting physical quantities due to vibration leakage component.

[0167] One embodiment of the physical quantity detection circuit, The frequency of the second frequency component may be twice the frequency of the first frequency component.

[0168] One embodiment of the physical quantity detection circuit, The drive circuit includes a full-wave rectifier circuit, The second frequency component may be generated by the full-wave rectifier circuit.

[0169] This physical quantity detection circuit allows the full-wave rectifier circuit, which is necessary for generating the drive signal, to also function as a circuit that generates the second frequency component necessary for fault diagnosis based on electrostatic leakage components, thus eliminating the need for a dedicated circuit to generate the second frequency component.

[0170] One embodiment of the physical quantity detection circuit is: The system may further include a first fault diagnosis circuit that performs fault diagnosis based on the first fault diagnosis signal.

[0171] According to this physical quantity detection circuit, if a fault such as a break or short circuit occurs in the wiring connected to the physical quantity detection element, the first fault diagnosis signal changes, allowing for the diagnosis of the fault in that wiring.

[0172] One embodiment of the physical quantity detection circuit, The aforementioned physical quantity detection signal output circuit is A differential amplifier circuit that differentially amplifies a signal pair based on the first signal and the second signal, A first synchronous detection circuit that synchronously detects a signal based on the output signal of the differential amplifier circuit and outputs a signal corresponding to the difference between the first physical quantity component and the second physical quantity component, Includes a physical quantity detection signal generation circuit that generates the physical quantity detection signal based on the output signal of the first synchronous detection circuit, The first fault diagnosis signal output circuit is: An adder circuit that adds the aforementioned signal pairs, A second synchronous detection circuit synchronously detects a signal based on the output signal of the summing circuit and outputs a signal corresponding to the sum of the first electrostatic leakage component and the second electrostatic leakage component, The system may also include a first fault diagnosis signal generation circuit that generates the first fault diagnosis signal based on the output signal of the second synchronous detection circuit.

[0173] In this physical quantity detection circuit, the physical quantity components in the first signal and the physical quantity components in the second signal are in opposite phase to each other. Therefore, the physical quantity components are amplified by a differential amplifier circuit and attenuated by an adder circuit. Consequently, this physical quantity detection circuit can generate a physical quantity detection signal with high accuracy, and the risk of the accuracy of the first fault diagnosis signal being reduced by the physical quantity components is minimized.

[0174] Furthermore, in this physical quantity detection circuit, the first electrostatic leakage component contained in the first signal and the second electrostatic leakage component contained in the second signal are in phase with each other. Therefore, the electrostatic leakage component is amplified by the summing circuit and attenuated by the differential amplifier circuit. Consequently, this physical quantity detection circuit can generate the first fault diagnosis signal with high accuracy, and the risk of the accuracy of the physical quantity detection signal being reduced by the electrostatic leakage component is minimized.

[0175] One embodiment of the physical quantity detection circuit is: It further has a second fault diagnosis signal output circuit, The first signal includes a first vibration leakage component based on the vibration of the physical quantity detection element. The second signal includes a second vibration leakage component based on the vibration of the physical quantity detection element, The second fault diagnosis signal output circuit may output a second fault diagnosis signal generated based on the first vibration leakage component and the second vibration leakage component.

[0176] In this physical quantity detection circuit, if a failure such as damage occurs in the physical quantity detection element, the magnitudes of the first vibration leakage component and the second vibration leakage component generated in the first detection electrode and the second detection electrode, respectively, based on the vibration of the physical quantity detection element, change. As a result, the second fault diagnosis signal generated based on the first and second vibration leakage components also changes. Therefore, this physical quantity detection circuit can generate a second fault diagnosis signal that can be used to diagnose a failure in the physical quantity detection element. For example, an external device can diagnose a failure in the physical quantity detection element based on the second fault diagnosis signal.

[0177] One embodiment of the physical quantity detection circuit, The aforementioned physical quantity detection signal output circuit is A differential amplifier circuit that differentially amplifies a signal pair based on the first signal and the second signal, A first synchronous detection circuit that synchronously detects a signal based on the output signal of the differential amplifier circuit and outputs a signal corresponding to the difference between the first physical quantity component and the second physical quantity component, Includes a physical quantity detection signal generation circuit that generates the physical quantity detection signal based on the output signal of the first synchronous detection circuit, The first fault diagnosis signal output circuit is: An adder circuit that adds the aforementioned signal pairs, A second synchronous detection circuit synchronously detects a signal based on the output signal of the summing circuit and outputs a signal corresponding to the sum of the first electrostatic leakage component and the second electrostatic leakage component, The system includes a first fault diagnosis signal generation circuit that generates the first fault diagnosis signal based on the output signal of the second synchronous detection circuit, The second fault diagnosis signal output circuit is: A third synchronous detection circuit that synchronously detects a signal based on the output signal of the summing circuit and outputs a signal corresponding to the sum of the first vibration leakage component and the second vibration leakage component, The system may also include a second fault diagnosis signal generation circuit that generates the second fault diagnosis signal based on the output signal of the third synchronous detection circuit.

[0178] In this physical quantity detection circuit, the physical quantity components in the first signal and the physical quantity components in the second signal are in opposite phase to each other. Therefore, the physical quantity components are amplified by a differential amplifier circuit and attenuated by an adder circuit. Consequently, this physical quantity detection circuit can generate a physical quantity detection signal with high accuracy, and the risk of the accuracy of the first and second fault diagnosis signals being reduced by the physical quantity components is minimized.

[0179] Furthermore, in this physical quantity detection circuit, the first electrostatic leakage component contained in the first signal and the second electrostatic leakage component contained in the second signal are in phase with each other. Therefore, the electrostatic leakage component is amplified by the summing circuit and attenuated by the differential amplifier circuit. Consequently, this physical quantity detection circuit can generate the first fault diagnosis signal with high accuracy, and the risk of the accuracy of the physical quantity detection signal being reduced by the electrostatic leakage component is minimized.

[0180] Furthermore, in this physical quantity detection circuit, the first vibration leakage component included in the first signal and the second vibration leakage component included in the second signal are in phase with each other. Therefore, the vibration leakage component is amplified by the summing circuit and attenuated by the differential amplifier circuit. Consequently, this physical quantity detection circuit can accurately generate the second fault diagnosis signal, and the risk of the accuracy of the physical quantity detection signal being reduced by the vibration leakage component is minimized.

[0181] One embodiment of the physical quantity detection circuit is: The system may further include a second fault diagnosis circuit that performs fault diagnosis based on the second fault diagnosis signal.

[0182] According to this physical quantity detection circuit, if a malfunction such as damage occurs in the physical quantity detection element, the second fault diagnosis signal changes, allowing for the diagnosis of the malfunction in the physical quantity detection element.

[0183] One embodiment of a physical quantity detection device is: One embodiment of the physical quantity detection circuit, The system includes the aforementioned physical quantity detection element.

[0184] In this physical quantity detection device, if a fault such as a break or short circuit occurs in the wiring connected to the physical quantity detection element, the magnitude of the first and second electrostatic leakage components, which are propagated by the second frequency component included in the drive signal to the first and second detection electrodes respectively, changes. As a result, the first fault diagnosis signal generated based on the first and second electrostatic leakage components also changes. Therefore, this physical quantity detection device can generate a first fault diagnosis signal that can be used to diagnose faults in the wiring connected to the physical quantity detection element. For example, an external device can diagnose a fault in the wiring based on the first fault diagnosis signal.

[0185] Furthermore, this physical quantity detection device can generate a first fault diagnosis signal that can be used to diagnose faults in the wiring connected to the physical quantity detection element based on the electrostatic leakage component. Therefore, a physical quantity detection element tuned to have zero or near-zero vibration leakage component can be used. Accordingly, this physical quantity detection device can reduce the risk of decreased detection accuracy of physical quantities due to vibration leakage component. [Explanation of symbols]

[0186] 1...Physical quantity detection device, 5...MCU, 10...Reference voltage circuit, 20...Drive circuit, 21...Current-voltage conversion circuit, 22...Full-wave rectifier circuit, 23...Automatic gain control circuit, 24...Drive signal generation circuit, 25...Phase shift circuit, 26...Buffer circuit, 27...EXNOR circuit, 28...Buffer circuit, 30...Detection circuit, 31A...Charge amplifier circuit, 31B...Charge amplifier circuit, 32...Differential amplifier circuit, 33...Adder circuit, 34A...AC amplifier circuit, 34B...AC amplifier circuit, 35A...Synchronous detection circuit, 35B...Synchronous detection circuit, 35C...Synchronous detection circuit, 36A...Smoothing circuit, 36B...Smoothing circuit, 36C...Smoothing Circuit, 41…Analog / Digital Conversion Circuit, 42…Analog / Digital Conversion Circuit, 51…Digital Signal Processing Circuit, 52…Digital Signal Processing Circuit, 60…Control Circuit, 61…Fault Diagnosis Circuit, 62…Fault Diagnosis Circuit, 70…Interface Circuit, 80…Memory Unit, 90…Oscillation Circuit, 100…Physical Quantity Detection Element, 101a,101b…Drive Vibration Arm, 102…Detection Vibration Arm, 103…Weight Unit, 104a,104b…Drive Base, 105a,105b…Connecting Arm, 106…Weight Unit, 107…Detection Base, 112,113…Drive Electrode, 114,115…Detection Electrode, 116…Common Electrode, 200…Physical Quantity Detection Circuit

Claims

1. A drive circuit that applies a drive signal to drive a physical quantity detection element to the drive electrode of the physical quantity detection element, A detection circuit receives a signal pair based on a first signal output from the first detection electrode of the physical quantity detection element and a second signal output from the second detection electrode of the physical quantity detection element. Includes, The drive signal includes a first frequency component and a second frequency component having a frequency different from that of the first frequency component. The first signal includes a first electrostatic leakage component, which is a component obtained when the second frequency component propagates to the first detection electrode via a first electrostatic coupling capacitance between the drive electrode and the first detection electrode. The second signal includes a second electrostatic leakage component, which is a component obtained when the second frequency component propagates to the second detection electrode via the second electrostatic coupling capacitance between the drive electrode and the second detection electrode. The detection circuit is A physical quantity detection signal output circuit that differentially amplifies the signal pair, performs synchronous detection using a detection signal synchronized with the first frequency component, and outputs a physical quantity detection signal corresponding to the physical quantity, A first fault diagnosis signal output circuit adds the aforementioned signal pair, performs synchronous detection using a detection signal synchronized with the second frequency component, and outputs an electrostatic leakage detection signal generated based on the first electrostatic leakage component and the second electrostatic leakage component as a first fault diagnosis signal. Includes, The detection circuit is a physical quantity detection circuit that simultaneously outputs the physical quantity detection signal and the first fault diagnosis signal without requiring mode switching.

2. In claim 1, The aforementioned physical quantity detection signal is The first physical quantity component included in the first signal, The second physical quantity component included in the second signal, A physical quantity detection circuit that outputs a signal based on the physical quantity detection signal output circuit.

3. In claim 2, The detection circuit is The first charge amplifier circuit to which the first signal is input, The second charge amplifier circuit to which the second signal is input, The output signal of the first charge amplifier circuit and the output signal of the second charge amplifier circuit A differential amplifier circuit that differentially amplifies a pair of signals A first synchronous detection circuit that synchronously detects a signal based on the output signal of the differential amplifier circuit, The output signal from the first synchronous detection circuit is smoothed into a DC voltage signal, and the physical quantity detection signal is obtained. A first smoothing circuit that outputs as, An adder circuit that adds the aforementioned signal pairs, A second synchronous detection circuit that synchronously detects a signal based on the output signal of the summing circuit, The output signal from the second synchronous detection circuit is smoothed into a DC voltage signal, and the electrostatic leakage detection signal A second smoothing circuit that outputs as a number, Includes, The aforementioned physical quantity detection signal output circuit is The first charge amplifier circuit and the second charge amplifier circuit, The differential amplifier circuit, The first synchronous detection circuit and, The first smoothing circuit and, Composed of, The first fault diagnosis signal output circuit is: The first charge amplifier circuit and the second charge amplifier circuit, The aforementioned adding circuit, The above-mentioned second synchronous detection circuit, The above-mentioned second smoothing circuit, A physical quantity detection circuit composed of the following.

4. In claim 3, Includes a first fault diagnosis circuit that performs fault diagnosis based on the electrostatic leakage detection signal, Physical quantity detection circuit.

5. In claim 4, Includes a second fault diagnosis signal output circuit that outputs a vibration leakage detection signal, The first signal includes a first vibration leakage component based on the vibration of the physical quantity detection element. The second signal includes a second vibration leakage component based on the vibration of the physical quantity detection element. The vibration leakage detection signal is, The physical quantity detection cycle is generated based on the first vibration leakage component and the second vibration leakage component. Road.

6. In claim 5, The detection circuit is A third synchronous detection circuit that synchronously detects a signal based on the output signal of the summing circuit, The output signal from the third synchronous detection circuit is smoothed into a DC voltage signal, and the vibration leakage detection signal A third smoothing circuit that outputs as a signal, Includes, The second fault diagnosis signal output circuit is: The first charge amplifier circuit and the second charge amplifier circuit, The aforementioned adding circuit, The above-mentioned third synchronous detection circuit, The above-mentioned third smoothing circuit, A physical quantity detection circuit composed of the following.

7. In claim 6, A physical quantity detection system including a second fault diagnosis circuit that performs fault diagnosis based on the vibration leakage detection signal. circuit.

8. In any one of claims 1 to 7, The frequency of the second frequency component is twice the frequency of the first frequency component, a physical quantity measurement Output circuit.

9. In any one of claims 1 to 7, The drive circuit includes a full-wave rectifier circuit, The second frequency component is generated by the full-wave rectifier circuit, which is a physical quantity detection circuit.

10. A physical quantity detection circuit according to any one of claims 1 to 9, The aforementioned physical quantity detection element, A physical quantity detection device, including one.

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