JP2009198265A - Electrostatic capacitance type detection device and acceleration and angular velocity detection device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accomplish S/N ratio improvement, sensitivity enhancement, and miniaturization of a detection device by making the device include a CV conversion circuit for converting capacitance changes in an electrostatic capacitance type sensor unit into detection voltages. <P>SOLUTION: In this electrostatic capacitance type detection device, the sensor unit is provided with a driving unit having a vibrator 71 displaceable in X, Y and Z-axis directions and a pair of driving electrodes 75(Cd1, Cd2), a pair of first capacitive elements Cs1, Cs6 and second capacitive elements Cs2, Cs7 which are provided on and under the vibrator 71 so as to interpose it between, and changes and increases/decreases capacitances in mutually reverse directions in response to a displacement of the vibrator 71 in the X-axis direction, and a pair of third capacitance elements Cs3, Cs8 and fourth capacitance element Cs4, Cs9 which changes and increases/decreases capacitances in mutually reverse directions in response to a displacement in the Y-axis direction of the vibrator 71. By connecting detecting electrodes 72a1, 72b1 and 73a1, 73b1 facing the vibrator 71 to an IC respectively, multi-axis acceleration and angular velocity components become detectable through the use of the one vibrator. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a capacitance type detection device and an acceleration / angular velocity detection device using the same, and more specifically, a capacitance type sensor unit and a capacitance / conversion unit that converts a capacitance change of the sensor unit into a detection voltage. The present invention relates to a capacitance type detection device including a voltage (CV) conversion circuit and an acceleration / angular velocity detection device using the same.

  A conventional acceleration / angular velocity detection device using a capacitive electro mechanical system (MEMS) includes a signal processing circuit that simultaneously detects acceleration and angular velocity, and uses two reciprocating vibrators to accelerate the acceleration. Is detected by separating the in-phase and angular velocities as outputs of opposite phases, and CV conversion connects the potential of the vibrator to the input of the differential pair.

  This type of acceleration / angular velocity detection device, for example, as disclosed in Patent Document 1, supports a pair of vibrators on a substrate so as to be displaceable in the XY axis directions orthogonal to each other and vibrates in the X axis direction. By detecting the displacement of each vibrator in the Y-axis direction based on the change in the capacitance of the capacitor, the acceleration in the Y-axis direction acting on the substrate and the angular velocity around the Z-axis orthogonal to the XY axis are detected simultaneously. .

  FIG. 1 is a configuration diagram for explaining an acceleration / angular velocity detection device using a conventional capacitive MEMS, and is a schematic configuration diagram of FIG. 5 shown in Patent Document 1 described above.

  At the first and second time division timings T1 and T2, the voltage application circuit 11 applies the first voltage signal V1 whose polarity is inverted to both ends of the capacitors C1 and C2, and also has the same phase as the first voltage signal V1. A two-voltage signal V2 is applied across the capacitors C3 and C4. Therefore, a set of voltage signals output from the charge amplifier 12 at the first time division timing T1 and the second time division timing T2 cause the displacements in opposite directions in the Y-axis direction of the two vibrators to differ from each other. By canceling out, only the displacement in the same direction in the Y-axis direction of the two vibrators is represented. The sample hold circuits 14a and 14b sample and hold the voltage signals from the charge amplifier 12 at the first and second time division timings T1 and T2, respectively. Reference numeral 13 denotes a sampling timing control circuit for controlling the sample hold circuits 14a to 14d.

  The displacement in the same direction in the Y-axis direction of the two vibrators is the acceleration in the Y-axis direction that acts on the substrate 10. Therefore, the difference between the voltage signals sampled and held by the sample hold circuits 14 a and 14 b represents the magnitude of acceleration in the Y-axis direction that acts on the substrate 10. Then, the calculator 15 calculates and outputs the difference between the sampled and held voltage signals, and an output voltage indicating the magnitude of the acceleration is taken out from the calculator 15.

  In addition, at the third and fourth time division timings, the voltage application circuit 11 applies the first voltage signal V1 whose polarity is inverted to both ends of the capacitors C1 and C2, and has a phase opposite to that of the first voltage signal V1. A two-voltage signal V2 is applied across the capacitors C3 and C4. Therefore, a set of voltage signals output from the charge amplifier 12 at the third time division timing T3 and the fourth time division timing T4 cause the displacements of the two vibrators in the same direction in the Y-axis direction to differ from each other. By canceling out, only the opposite displacements in the Y-axis direction of the two vibrators are represented. The sample and hold circuits 14c and 14d sample and hold the voltage signals from the charge amplifier 12 at the third and fourth time division timings T3 and T4, respectively.

  The opposite displacements in the Y-axis direction of the two vibrators are angular velocities around the Z-axis that act on the substrate 10. Therefore, the difference between the voltage signals sampled and held by the sample hold circuits 14 c and 14 d represents the magnitude of the angular velocity around the Z axis acting on the substrate 10. The computing unit 16 computes and outputs the difference between the sampled and held voltage signals, and an output voltage representing the magnitude of acceleration is taken out from the computing unit 16.

  As described above, since the acceleration and the angular velocity can be detected simultaneously by using only the single charge amplifier 12, the acceleration / angular velocity detecting device can be realized with a simple configuration.

FIG. 2 is a block diagram showing a conventional example 1 for comparison with the present invention in consideration of FIG. A connection point between the capacitive element C1 and the capacitive element C2 constituting the sensor unit 21 is connected to the non-inverting input terminal of the operational amplifier 22, and Vref is applied to the inverting input terminal. A resistor R and a capacitive element C _FB are connected in parallel between the non-inverting input terminal and the output terminal. Switching elements SW1 and SW2 can be connected to one capacitive element C1 of the sensor unit 21, and switching elements SW3 and SW4 can be connected to the other capacitive element C2, and the switching elements SW1 and SW3 are interlocked. Thus, the signal Φ1 is supplied to the capacitive element C1 of the sensor unit 21, and the switching element SW2 and SW4 are interlocked so that the signal Φ2 having the opposite phase to the signal Φ1 is supplied to the capacitive element C2 of the sensor unit 21. The In other words, modulation is performed by switching the polarity of Vout by the signals Φ1 and Φ2. Vout at this time is
Vout = ± (C1-C2) / C _FB · 1 / 2VDD
It becomes.

FIG. 3 is a block diagram showing a conventional example 2 for comparison with the present invention. A capacitive element Cs is connected between the non-inverting input terminal of the operational amplifier 32 and GND, and Vref is applied to the inverting input terminal. A resistor R and a capacitive element C _FB are connected in parallel between the non-inverting input terminal and the output terminal.

The amount of charge accumulated in the capacitive element Cs is Q = Cs · Vref, and when acceleration and angular velocity are added and Cs changes, Q = (Cs + ΔC) · Vref. Since the charge balance is maintained at the point S1, a charge of -ΔC · Vref is induced in C _FB . In proportion to the change in Cs, an output of Vout = (ΔC / C _FB ) · Vref is obtained.

  Further, an acceleration sensor including a capacitance type sensor unit for detecting acceleration and angular velocity and a CV conversion circuit capable of changing a CV conversion rate using a switched capacitor circuit is disclosed in, for example, Patent Document 2. ing. In this type of acceleration sensor, at least two switches are connected to a variable capacitance capacitor to be measured in a CV conversion circuit that converts a value representing the capacitance of the capacitor into a voltage with a predetermined CV conversion rate and outputs the voltage. The CV conversion rate is determined according to the ratio between the equivalent resistance value of the switched capacitor circuit and the resistance value of the resistance circuit.

JP 2004-28869 A JP-A-10-170544 JP 2002-31644 A

  However, the one described in Patent Document 1 described above or the one in the conventional example 1 shown in FIG. 2 has a problem that the SN of the angular velocity decreases when acceleration is taken simultaneously. This is because the vibrator driving force is weak because the vibrator potential is ½ VDD reference, and sampling is essential and noise is folded. Further, when the vibrator side is connected to a differential pair, there is a problem that only one axial direction can be detected in principle. This is because the charge is confused between the two axes.

That is, in the conventional CV conversion method for simultaneous measurement of acceleration and angular velocity, the potential of the vibrator becomes 1/2 VDD as in Patent Document 1 or Conventional Example 1 shown in FIG. There is a problem (angular velocity component: Coriolis force is proportional to the amplitude of the vibrator). The potential of the vibrator is Vmass, the potential of the drive electrode is Vdrive = V _DC + V _AC (V _AC : a component of the resonance frequency (Fr) of the vibrator), the capacitance between the drive electrode and the vibrator is C, and the drive electrode And the distance between the transducers is d, the magnitude of the driving force (Coulomb force) applied to the transducers is F = C / 2d · (Vmass−Vdrive) ² , and the component is extracted at an effective resonance frequency. , C / d · (Vmass−V _DC ) · V _AC .

(1) When Vmass = 1/2 · VDD, V _DC = 3/4 · VDD (1/4 · VDD), V _AC = 1/4 · VDD · sin (2πFr · T), and the driving force becomes maximum ,
(2) When Vmass = GND, the driving force is minimized when V _DC = 1/2 · VDD and V _AC = 1/2 · VDD · sin (2πFr · T).

  In comparison, ((1/2) − (3/4)) · 1/4: (0−1 / 2) · 1/2 = 1: 4. Compared with the case where the vibrator is dropped to GND, the driving force is ¼.

Further, in the circuit like the conventional example 2 shown in FIG. 3, since the HPF (high pass filter) of Fc = 1 / (2πRC _FB ) is obtained, the acceleration component (DC component) cannot be obtained unless modulation is applied. There is.

  Moreover, the thing of patent document 2 also has the problem that SN of acceleration falls. This is because the switched capacitor circuit is regarded as an equivalent resistance, and the acceleration component is not modulated, so that the 1 / f noise of the operational amplifier is taken in as it is.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a capacitive sensor unit and a capacitance / voltage (CV) for converting a change in capacitance of the sensor unit into a detection voltage. It is an object of the present invention to provide a capacitance type detection device and an acceleration / angular velocity detection device using the same that are provided with a conversion circuit to improve the SN ratio and sensitivity, and to reduce the size.

The present invention has been made to achieve such an object. The invention according to claim 1 is a capacitance type sensor unit and a CV that converts a capacitance change from the sensor unit into a detection voltage. In a capacitance-type detection device including a conversion circuit, a capacitive element having at least a pair of detection electrodes provided so as to sandwich a displaceable vibrator constituting the sensor unit, and the detection voltage of the sensor unit And a modulation means for modulating the capacitance element, fixing the vibrator side of the capacitive element to a predetermined potential, and connecting the detection electrode side of the capacitive element to an input portion of the CV conversion circuit. Capacitance type detection device. (Example 1, Example 2, FIG. 8, FIG. 11)
According to a second aspect of the present invention, in the first aspect of the present invention, the CV conversion circuit is a switched capacitor type CV conversion circuit having a switching element connected to the capacitive element. To do. (Example 1, FIG. 8)
According to a third aspect of the present invention, in the first aspect of the present invention, the CV conversion circuit includes an operational amplifier connected to the detection electrode of the capacitive element. It has a capacitor (Cc) that modulates the input potential of the differential pair to a high frequency voltage, and a circuit for applying the high frequency voltage. (Example 2, FIG. 11)
According to a fourth aspect of the present invention, in the first aspect of the present invention, the sensor unit is supported on the substrate and can be displaced in the XYZ axial directions orthogonal to each other, and A drive unit having a pair of drive electrodes that vibrate in the axial direction and upper and lower portions sandwiching the vibrator, and increase or decrease capacitance changes in opposite directions with respect to displacement of the vibrator in the X-axis direction. A pair of first (Cs1, Cs6) and second capacitive elements (Cs2, cs7) and the transducer are provided vertically so as to sandwich the transducer, and change in capacitance with respect to displacement of the transducer in the Y-axis direction. A pair of third (Cs3, Cs8) and fourth capacitive elements (Cs4, Cs9) that increase or decrease in opposite directions are provided above and below to sandwich the vibrator and surround the drive electrode. Arranged in the Z axis of the vibrator Characterized in that it comprises a pair of detecting a change in capacitance with respect to displacement in the direction the fifth capacitive element (Cs5, Cs10). (Fig. 7)
According to a fifth aspect of the present invention, the capacitance type detection device according to any one of the first to fourth aspects is used, and the acceleration in the XYZ-axis direction acting on the vibrator and the angular velocity around the XY axis are determined. It is an acceleration / angular velocity detection device characterized by detecting.

  The invention according to claim 6 is the demodulation according to claim 5, wherein the CV conversion circuit includes an XYZ axis CV conversion circuit and is connected to each of the XYZ axis CV conversion circuits. A low-pass filter that outputs an XYZ-axis acceleration signal connected to each of the demodulation circuits, a high-pass filter that outputs an angular velocity signal of the XY-axis connected to each of the demodulation circuits, and a synchronous detection circuit And a low-pass filter. (Fig. 10)

  According to a seventh aspect of the invention, in the sixth aspect of the invention, a Z-axis CV conversion circuit of the CV conversion circuit, the sensor unit, and an oscillation circuit connected to the synchronous detection circuit are provided. It is characterized by that. (Fig. 10)

  The invention according to claim 8 is the demodulation according to claim 5, wherein the CV conversion circuit includes an XYZ axis CV conversion circuit and is connected to each of the XYZ axis CV conversion circuits. A low-pass filter that outputs an XYZ-axis acceleration signal connected to each of the demodulation circuits, and a low-pass filter that outputs an XY-axis angular velocity signal directly connected to each of the XYZ-axis CV conversion circuits. It is characterized by providing. (Fig. 13)

  The invention according to claim 9 is the invention according to claim 8, further comprising an oscillation circuit connected to the Z-axis CV conversion circuit of the CV conversion circuit, the sensor unit, and the synchronous detection circuit. It is characterized by that. (Fig. 13)

  According to the present invention, a capacitive element having at least a pair of detection electrodes provided so as to sandwich a displaceable vibrator constituting the sensor unit, and a modulation unit that modulates the detection voltage of the sensor unit are provided. Since the vibrator side of the element is fixed to a predetermined potential and the detection electrode side of the capacitive element is connected to the input part of the CV conversion circuit, it can be used for simultaneous detection of acceleration and angular velocity of the capacitive detection type MEMS. Signal processing is possible. Further, acceleration and angular velocity can be separated as separate frequency components with a single vibrator.

  Further, the present invention is characterized in that the CV conversion has a structure in which the potential of the vibrator is set to a predetermined potential and the opposing electrode sides are connected to a differential pair. Further, since the acceleration is modulated to the clock frequency, a circuit that demodulates to DC is arranged in the detection stage, so that a high SN with respect to the angular velocity can be obtained. Further, by fixing the potential of the vibrator to the GND potential, there is an effect that the driving force can be increased 4 times and the sensitivity is increased 4 times with respect to 1/2 VDD fixed. In addition, since a combination of one vibrator and a circuit can simultaneously measure two or more axes of acceleration and angular velocity, the size can be reduced.

  Further, the surface of the capacitor facing the vibrator can be input to the differential pair, and the detection can be performed by modulating the potential applied to Cs by using the capacitor (Cc).

Embodiments of the present invention will be described below with reference to the drawings.
4A to 4C are diagrams showing a sensor structure (sensor unit) for explaining the capacitance type detection device of the present invention. This sensor unit can be used as a triaxial sensor unit of the acceleration / angular velocity detection device.

  The sensor unit in the present invention is composed of ten electrostatic capacitance elements with a vibrator interposed therebetween. That is, as shown in FIG. 4B, the sensor unit includes vibrators 52a and 52b provided in the X-axis direction and vibrators 53a and 53b provided in the Y-axis direction at the center of the Si layer 51. And an oscillator 54 provided at the intersection of the X axis and the Y axis, and this oscillator 54 is fixed to the Si layer 51 via a beam 55.

  Further, on the upper surface of the Si layer 51, as shown in FIG. 4A, a detection electrode and a drive electrode are provided on the glass layer 41. In other words, the X-axis detection electrodes 42a and 42b and the vibrators 53a and 53b provided in the Y-axis direction are opposed to the vibrators 52a and 52b provided in the X-axis direction. A drive electrode 45 is provided so as to face the detection electrodes 43a and 43b and the vibrator 54 provided at the intersection of the X axis and the Y axis, and the Z axis detection is performed so as to surround the periphery of the drive electrode 45. A working electrode 44 is provided.

  Similarly, a detection electrode and a driving electrode are provided on the glass layer 61 on the lower surface of the Si layer 51 as shown in FIG. In other words, the X axis detection electrodes 62a and 62b so as to face the vibrators 52a and 52b provided in the X axis direction and the Y axis so as to face the vibrators 53a and 53b provided in the Y axis direction. A drive electrode 65 is provided so as to face the detection electrodes 63a and 63b and the vibrator 54 provided at the intersection of the X axis and the Y axis, and the Z axis detection is performed so as to surround the periphery of the drive electrode 65. A working electrode 64 is provided.

  With such a structure, the X-axis detection electrodes 42a, 42b and the vibrators 52a, 52b provided in the X-axis direction constitute the capacitive elements C1, C2, and the X-axis detection electrodes 62a, 62b and X Capacitance elements C6 and C7 are constituted by the vibrators 52a and 52b provided in the axial direction. The Y-axis detection electrodes 43a and 43b and the vibrators 53a and 53b provided in the Y-axis direction constitute capacitive elements C3 and C4, and the Y-axis detection electrodes 63a and 63b are provided in the Y-axis direction. Capacitance elements C8 and C9 are constituted by the vibrators 53a and 53b. Further, the electrostatic capacitance element C5 is constituted by the Z-axis detection electrode 44 and the vibrator 54 provided at the intersection of the X-axis and the Y-axis, and the intersection of the Z-axis detection electrode 64 and the X-axis and the Y-axis. The capacitive element C <b> 10 is configured by the vibrator 54.

  FIGS. 5A and 5B are diagrams for explaining the principle of acceleration detection by the sensor unit shown in FIGS. 4A to 4C. The acceleration (Fx = max) is the mass of the vibrator. It shows that the DC output is proportional to the acceleration.

  As shown in FIG. 5A, the vibrators 52a, 54, and 52b provided in the X-axis direction are driven by the drive electrodes 45 and 65. For example, the vibrator 52a side is inclined downward to vibrate. When the child 52b vibrates so as to incline upward, the space between the X-axis detection electrode 42a and the vibrator 52a expands, and the space between the X-axis detection electrode 42b and the vibrator 52b narrows, so that The DC output (Vx) indicating the acceleration Fx is a value proportional to (C1 + C7) − (C2 + C6).

  Further, as shown in FIG. 5B, when the vibrator 54 provided in the Z-axis direction is driven by the drive electrodes 45 and 65, for example, when the vibrator 54 vibrates so as to tilt downward. Thus, the gap between the Z-axis detection electrode 44 and the vibrator 54 widens, the gap between the Z-axis detection electrode 64 and the vibrator 54 narrows, and a DC output (Vz) indicating the acceleration Fz in the Z-axis direction is obtained. The value is proportional to C5 to C10.

  FIGS. 6A and 6B are diagrams for explaining the principle of angular velocity detection by the sensor unit shown in FIGS. 4A to 4C, in which the angular velocity (Fx = 2 mvz · Ωy) is the Coriolis force. It shows that the AC output is synchronized. The Coriolis force is a force generated in a direction orthogonal to the velocity and angular velocity.

  As shown in FIG. 6A, the vibrators 52a, 54, and 52b provided in the X-axis direction are driven by the drive electrodes 45 and 65 so that the vibrators are caused to have a resonance frequency (Fr) by the Coulomb force. When driven, the vibrator vibrates up and down to generate Vz. Further, as shown in FIG. 6B, when the vibrator 52a side and the 52b side vibrate up and down, the AC output (Vx) indicating the angular velocity Fx becomes a value proportional to C1-C2.

  FIG. 7A is a schematic diagram for explaining a sensor structure used in the capacitance type detection device of the present invention, and FIG. 7B is a schematic diagram for explaining a conventional sensor structure for comparison with the present invention. is there. Although not shown in FIG. 7A, Z-axis detection electrodes and drive electrodes are provided above and below the vibrator 71 in the same manner as in FIGS. 4A and 4B.

  With such a structure, the X-axis detection electrodes 72a1 and 72b1 and the vibrator 71 provided in the X-axis direction constitute the capacitive elements Cs1 and Cs2, respectively. And electrostatic capacitance elements Cs6 and Cs7 are respectively configured. Capacitance elements Cs3 and Cs4 are configured by the Y-axis detection electrodes 73a1 and 73b1 and the vibrator 71, respectively. Capacitance elements Cs8 and Cs9 are respectively formed by the Y-axis detection electrode and the vibrator 71 on the back side. Composed. Furthermore, the Z-axis detection electrode 74 and the vibrator 71 constitute a capacitive element Cs5, and the back-side Z-axis detection electrode and the vibrator 71 constitute a capacitive element Cs10.

  In contrast, in the conventional sensor unit, as shown in FIG. 7B, X-axis detection electrodes 702a and 702b and Y-axis detection electrodes 703a and 703b are provided on the vibrator 701. When the vibrator 701 is connected to the IC, charging of all the capacitors is started. Since the CV conversion circuit sees the change in charge when C changes, the change in the X axis and the change in the Y axis cannot be distinguished.

  However, as shown in FIG. 7A, according to the sensor structure used in the present invention, the X-axis detection electrodes 72a1 and 72b1 and the Y-axis detection electrodes 73a1 and 73b1 are provided on the vibrator 71. The X-axis detection electrodes 72a1 and 72b1 and the Y-axis detection electrodes 73a1 and 73b1 are connected to the IC, respectively, and the X-axis CV conversion is performed based on the outputs from the X-axis detection electrodes 72a1 and 72b1. The Y-axis CV conversion is performed based on the outputs from the Y-axis detection electrodes 73a1 and 73b1. In this way, if the detection electrodes 72a1, 72b1 and 73a1, 73b1 facing the vibrator 71 are connected to the IC, multi-axis acceleration and angular velocity components can be detected by one vibrator.

  That is, the sensor unit used in the acceleration / angular velocity detection device of the present invention includes a vibrator 71 supported on a substrate and capable of being displaced in the XYZ-axis directions orthogonal to each other, and a pair for vibrating the vibrator 71 in the Z-axis direction. And a pair of first capacitors that are provided above and below to sandwich the vibrator 71 and increase or decrease capacitance changes in opposite directions with respect to the displacement of the vibrator 71 in the X-axis direction. A pair of elements Cs1 and Cs6 and second capacitor elements Cs2 and cs7, which are provided vertically so as to sandwich the vibrator 71, and increase or decrease capacitance changes in opposite directions with respect to the displacement of the vibrator 71 in the Y-axis direction. The third capacitive elements Cs3 and Cs8 and the fourth capacitive elements Cs4 and Cs9 are provided so as to sandwich the vibrator 71 and are disposed so as to surround the drive electrode. Axial direction And a capacitive element Cs5, Cs 10 of the pair of fifth to detect the change in capacitance with respect to displacement.

  As described above, the capacitance type sensor unit 102 in the acceleration / angular velocity detection device of the present invention has at least a pair of detection electrodes 72 a 1 provided so as to sandwich the displaceable vibrator 71 constituting the sensor unit 102. The capacitive elements Cs1 and Cs6 having 72a2 and a modulation unit that modulates the detection voltage of the sensor unit 102 are fixed. The vibrator side of the capacitive elements Cs1 and Cs6 is fixed at the GND level, and the capacitive elements Cs1 and Cs6 are detected The electrodes 72 a 1 and 72 a 2 are connected to the input part of the CV conversion circuit 103.

  CV conversion in the X-axis direction is performed by connecting the X-axis detection electrodes 72a1 and 72b1 to the input part of the CV conversion circuit 103, and CV conversion in the Y-axis direction is performed by connecting the Y-axis detection electrodes 73a1 and 73b1 to the CV conversion circuit. This is performed by connecting to the input unit 103.

  With such a configuration, it is possible to detect the acceleration in the XYZ axis direction acting on the vibrator 71 and the angular velocity around the XY axis.

  FIG. 8 is a circuit diagram for explaining the first CV conversion system (first embodiment) of the CV conversion circuit in the acceleration / angular velocity detection device according to the present invention, which is an improvement of the conventional example 1 shown in FIG. Correspondingly, the difference from the CV conversion method in FIG. 2 is that the configuration is such that the potential of the vibrator can be set to GND. The CV conversion circuit of the present invention is a switched capacitor type CV conversion circuit having a switching element connected to a capacitive element.

  The potentials on the vibrator side of the capacitive element C1 and the capacitive element C2 constituting the sensor unit 81 are connected to GND, and one capacitive element C1 is composed of switching elements SW1a, SW1b, SW2, and the other capacitive element C2 is switched. It is composed of elements SW3a, SW3b, SW4, and these switching elements constitute modulation means.

By such modulation means, the signals Φ1A and Φ1B are alternately switched from SW1a and SW1b, and the signals Φ1A and Φ1B are alternately switched from SW3a and SW3b. The quantity is supplied to the non-inverting input terminal of the operational amplifier 82. 1.5 V is applied as Vref to the inverting input terminal. Further, SW5 (signal ΦR) and a capacitive element C _FB are connected in parallel between the non-inverting input terminal and the output terminal. SW2 and SW4, SW1a and SW3a, SW1b and SW3b are linked, and modulation is performed by switching the polarity of Vout by these signals Φ1A, Φ1B and signal Φ2.

FIG. 9 is a diagram showing clock control timing indicating signal switching of the modulation means in FIG. When the signal Φ1A is switched to the signal Φ2, the charge amount of the signal Φ1 is Q = VDD · C1, and when the output Vout of the signal Φ2 is obtained by the charge conservation law, VDD · C1 = (1/2) VDD · a (C1 + C2) + (( 1/2) VDD-Vout) · C FB becomes, Vout = (C1-C2) / C FB · (1/2) VDD.
Moreover, switching signals Φ1B the signal .phi.2, Vout = - a _{(C1-C2) / C FB} · (1/2) VDD.

Thus, with the configuration shown in FIG. 8, Vout = ± (C1-C2) / _CFB · (1/2) VDD is obtained, and the potential of the vibrator can be lowered to GND (VDD). The driving force is four times that of 1.

  FIG. 10 is a configuration block diagram for explaining an acceleration / angular velocity detection apparatus using the CV conversion circuit according to the first embodiment. In the figure, reference numeral 101 is an oscillation circuit, 102 is a sensor unit, 103 is a CV conversion circuit, 104 is a demodulation circuit, 105a, 105b and 105c are low-pass filters (LPF), 106a and 106b are high-pass filters (HPF), and 107 is Synchronous detection circuits (demodulation circuits) 108a and 108b are low-pass filters (LPF).

  The oscillation circuit 101 supplies a drive signal to the drive electrode of the sensor unit 102 and supplies a reference signal to the synchronous detection circuit 107. The sensor unit 102 has a configuration as shown in FIG. The CV conversion circuit 103 converts a capacitance change into a detection voltage based on an output signal from the sensor unit 102, and outputs acceleration and angular velocity signals. A specific CV conversion method and circuit diagram in the CV conversion circuit 103 are as shown in FIG.

  The demodulation circuit 104 demodulates the acceleration / angular velocity component modulated to a high frequency by the CV conversion circuit 103 into the original frequency band (acceleration is a DC component and angular velocity is a resonance frequency component).

  Low-pass filters (LPF) 105a, 105b, and 105c cut off the AC component from the acceleration and angular velocity signals from the CV conversion circuit 103 via the demodulation circuit 104 and output acceleration components Ax, Ay, and Az, respectively. . The high-pass filters (HPF) 106 a and 106 b cut off DC components from the acceleration and angular velocity signals from the CV conversion circuit 103 via the demodulation circuit 104. The synchronous detection circuit 107 demodulates the AC signal from the high pass filters (HPF) 106a and 106b into a DC signal. The low-pass filters (LPF) 108 a and 108 b output angular velocity components Ωy and Ωx based on the DC components from the synchronous detection circuit 107, respectively.

  In other words, the CV conversion circuit 103 includes an XYZ axis CV conversion circuit, the demodulation circuit 104 connected to each of the XYZ axis CV conversion circuits, and the XYZ axis acceleration connected to each of the demodulation circuits 104. Low-pass filters 105 a, 105 b, 105 c that output signals, high-pass filters 106 a, 106 b that output angular velocity signals on the XY axes connected to each of the demodulation circuits 104, and low-pass filters 108 a, 108 b via the synchronous detection circuit 107. I have. In addition, the CV conversion circuit 103 includes a Z-axis CV conversion circuit, a sensor unit 102, and an oscillation circuit 101 connected to the synchronous detection circuit 107.

  With such a configuration, signal processing for simultaneous detection of acceleration and angular velocity of the capacitive detection type MEMS is possible. Further, acceleration and angular velocity can be separated as separate frequency components with a single vibrator.

  FIG. 11 is a circuit diagram for explaining a second CV conversion system (second embodiment) of the CV conversion circuit in the acceleration / angular velocity detection device according to the present invention, which is an improvement of the conventional example 2 shown in FIG. Correspondingly, the difference from the CV conversion method in FIG. 3 is that it is configured to detect acceleration. The CV conversion circuit includes an operational amplifier connected to the detection electrode of the capacitive element, a capacitor Cc that modulates the input potential of the differential pair of the operational amplifier into a high frequency voltage, and a high frequency voltage application circuit ( Clock generation circuit) 110.

The output of the sensor unit 111 modulates Vin of the operational amplifier 112 with the clock frequency via the capacitive element Cc (Vin = (1/2) VDD + V _AC ). The difference between the output of the operational amplifier 112, Vout1-Vout2 = (C1- C2) / C FB · Vin = (C1-C2) / C FB · (1/2) VDD + (C1-C2) / C FB · V AC It becomes. (C1-C2) / _CFB · (1/2) VDD is an output corresponding to the angular velocity, and (C1-C2) changes at the resonance frequency, so the angular velocity component becomes the resonance frequency. (C1-C2) / C _FB · _VAC is an output corresponding to acceleration, and is a component modulated by the clock frequency.

  12A and 12B are diagrams showing output waveforms of the angular velocity component and the acceleration component in FIG. The acceleration component is 500 kHz, and the angular velocity component is the resonance frequency (10 kHz).

  As described above, the configuration shown in FIG. 11 enables detection of acceleration with respect to Conventional Example 2, and the potential of the vibrator is set to GND (VDD as in the case of the first CV conversion method shown in FIG. ), The driving force is four times that of Conventional Example 1.

  FIG. 13 is a configuration block diagram for explaining an acceleration / angular velocity detection apparatus using the CV conversion circuit according to the second embodiment. Components having the same functions as those in FIG. 10 are denoted by the same reference numerals.

  The difference from the acceleration / angular velocity detection device shown in FIG. That is, in the acceleration / angular velocity detection device shown in FIG. 10, the demodulation circuit 104 is arranged immediately after the CV conversion circuit 103, whereas in the acceleration / angular velocity detection device shown in FIG. The demodulating circuit 104 is connected to a signal processing system that detects Ax, Ay, and Az. Note that the oscillation circuit 101 and the sensor unit 102 are the same as those in FIG. A specific CV conversion method and circuit diagram in the CV conversion circuit 103 are as shown in FIG.

  The demodulation circuit 104 demodulates the original DC component with respect to the acceleration component modulated to the clock frequency from the CV conversion circuit 103.

  Low-pass filters (LPF) 105a, 105b, and 105c cut off the AC component from the acceleration and angular velocity signals from the CV conversion circuit 103 via the demodulation circuit 104 and output acceleration components Ax, Ay, and Az, respectively. . The synchronous detection circuit 107 demodulates the AC signal from the CV conversion circuit 103 into a DC signal. The low-pass filters (LPF) 108 a and 108 b output angular velocity components Ωy and Ωx based on the DC components from the synchronous detection circuit 107, respectively.

  In other words, the CV conversion circuit 103 includes an XYZ axis CV conversion circuit, the demodulation circuit 104 connected to each of the XYZ axis CV conversion circuits, and the XYZ axis acceleration connected to each of the demodulation circuits 104. Low-pass filters 105a, 105b, and 105c that output signals, and low-pass filters 108a and 108b that output XY-axis angular velocity signals directly connected to each of the XYZ-axis CV conversion circuits via the synchronous detection circuit 107 are provided. Yes. In addition, the CV conversion circuit 103 includes a Z-axis CV conversion circuit, a sensor unit 102, and an oscillation circuit 101 connected to the synchronous detection circuit 107.

  With such a configuration, signal processing for simultaneous detection of acceleration and angular velocity of the capacitive detection type MEMS is possible. Further, acceleration and angular velocity can be separated as separate frequency components with a single vibrator.

  In the first and second embodiments described above, the vibrator potential is set to 0 V. However, the present invention is not limited to this, and may be set to a higher potential in combination with VDD or a booster circuit.

It is a block diagram for demonstrating the acceleration and angular velocity detection apparatus using the conventional electrostatic capacitance type MEMS. It is a block diagram which shows the prior art example 1 for contrast with this invention which considered FIG. It is a block diagram which shows the prior art example 2 for contrast with this invention. (A) thru | or (c) is a figure which shows the sensor structure (sensor part) for demonstrating the electrostatic capacitance type detection apparatus of this invention. (A), (b) is a figure for demonstrating the principle of the acceleration detection by the sensor part shown in FIG. (A), (b) is a figure for demonstrating the principle of the angular velocity detection by the sensor part shown in FIG. It is the schematic for demonstrating the sensor structure used for the electrostatic capacitance type detection apparatus of this invention. It is the schematic for demonstrating the conventional sensor structure for a comparison with this invention. It is a circuit diagram for demonstrating the 1st CV conversion system (Example 1) of the CV conversion circuit in the acceleration and angular velocity detection apparatus which concerns on this invention. It is a figure which shows the clock control timing which shows the signal switching of the modulation | alteration means in FIG. 1 is a configuration block diagram for explaining an acceleration / angular velocity detection device using a CV conversion circuit according to a first embodiment; It is a circuit diagram for demonstrating the 2nd CV conversion system (Example 2) of the CV conversion circuit in the acceleration and angular velocity detection apparatus which concerns on this invention. (A), (b) is a figure which shows the output waveform of the angular velocity component and acceleration component in FIG. It is a block diagram for explaining an acceleration / angular velocity detection apparatus using a CV conversion circuit according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Board | substrate 11 Voltage application circuit 12 Charge amplifier 13 Sampling timing control circuit 14a, 14b, 14c, 14d Sample hold circuit 15, 16 Operation unit 21 Sensor part 22, 32 Operation amplifier 41 Glass layer 42a, 42b, 62a, 62b X-axis detection Electrode 43a, 43b, 63a, 63b Y-axis detection electrode 44, 64 Z-axis detection electrode 45, 65 Drive electrode 51 Si layers 52a, 52b, 53a, 53b, 54 Vibrator 55 Beam 71 Vibrator 72a1, 72b1 X-axis detection electrode 73a1, 73b1 Y-axis detection electrode 74 Z-axis detection electrode 75 Drive electrode 81, 111 Sensor unit 82, 112 Operational amplifier 101 Oscillation circuit 102 Sensor unit 103 CV conversion circuit 104 Demodulation circuits 105a, 105b 105c Low-pass filter (LPF)
107 Synchronous detection circuit (demodulation circuit)
108a, 108b Low-pass filter (LPF)
701 Vibrators 702a and 702b X-axis detection electrodes 703a and 703b Y-axis detection electrodes

Claims (9)

In a capacitance-type detection device including a capacitance-type sensor unit and a CV conversion circuit that converts a capacitance change from the sensor unit into a detection voltage,
A capacitive element having at least a pair of detection electrodes provided so as to sandwich a displaceable vibrator constituting the sensor unit;
Modulation means for modulating the detection voltage of the sensor unit,
An electrostatic capacitance type detection device, wherein the vibrator side of the capacitive element is fixed to a predetermined potential, and the detection electrode side of the capacitive element is connected to an input portion of the CV conversion circuit.   2. The capacitance type detection device according to claim 1, wherein the CV conversion circuit is a switched capacitor type CV conversion circuit having a switching element connected to the capacitance element.   The CV conversion circuit includes an operational amplifier connected to the detection electrode of the capacitive element, a capacitor that modulates an input potential of a differential pair of the operational amplifier to a high frequency voltage, and application of the high frequency voltage The capacitance type detection device according to claim 1, further comprising a circuit. The sensor unit is
A vibrator supported on a substrate and displaceable in XYZ axial directions orthogonal to each other;
A drive unit having a pair of drive electrodes for vibrating the vibrator in the Z-axis direction;
A pair of first and second capacitive elements provided above and below to sandwich the vibrator and increasing / decreasing capacitance changes in opposite directions with respect to displacement of the vibrator in the X-axis direction;
A pair of third and fourth capacitive elements provided above and below to sandwich the vibrator and increasing / decreasing capacitance changes in opposite directions with respect to displacement of the vibrator in the Y-axis direction;
A pair of fifth capacitive elements that are provided vertically so as to sandwich the vibrator, and are disposed so as to surround the driving electrode, and detect a change in capacitance with respect to displacement of the vibrator in the Z-axis direction; The capacitance-type detection device according to claim 1, further comprising:   5. The acceleration / angular velocity detection characterized by detecting the acceleration in the XYZ-axis direction acting on the vibrator and the angular velocity around the XY axis using the capacitance type detection device according to claim 1. apparatus.   The CV conversion circuit includes an XYZ-axis CV conversion circuit, and outputs a demodulation circuit connected to each of the XYZ-axis CV conversion circuits and an XYZ-axis acceleration signal connected to each of the demodulation circuits. 6. The acceleration / angular velocity detection according to claim 5, further comprising: a low-pass filter; a high-pass filter that outputs an XY-axis angular velocity signal connected to each of the demodulation circuits; and a low-pass filter via a synchronous detection circuit. apparatus.   The acceleration / angular velocity detection device according to claim 6, further comprising an oscillation circuit connected to the Z-axis CV conversion circuit of the CV conversion circuit, the sensor unit, and the synchronous detection circuit.   The CV conversion circuit includes an XYZ-axis CV conversion circuit, and outputs a demodulation circuit connected to each of the XYZ-axis CV conversion circuits and an XYZ-axis acceleration signal connected to each of the demodulation circuits. 6. The acceleration / angular velocity detection device according to claim 5, further comprising: a low-pass filter; and a low-pass filter that outputs an XY-axis angular velocity signal directly connected to each of the XYZ-axis CV conversion circuits.   9. The acceleration / angular velocity detection device according to claim 8, further comprising an oscillation circuit connected to the Z-axis CV conversion circuit of the CV conversion circuit, the sensor unit, and the synchronous detection circuit.

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