Vibration type angular velocity sensor

Abstract

The vibration-type angular velocity sensor (100) is provided with a phase synchronization circuit (26) that outputs a frequency signal for controlling the frequency of a drive signal input to the vibrator (10). A phase synchronization circuit (26) includes: a comparator (41) that compares a detection signal from an oscillator (10) with a reference signal generated from a frequency signal; an integrator (42) having an operational amplifier (50) and a capacitor (70) and outputting an integrator output signal on the basis of the output from the comparator (41); an oscillator (43) that outputs a frequency signal of a predetermined frequency on the basis of the integrator output signal from the integrator (42); and a short-circuit switch unit (44) that, when the oscillator (10) is activated, is short-circuited so as to bypass the capacitor (70) of the integrator (42).

Description

Technical Field

[0001] The present invention relates to a vibration type angular velocity sensor, and in particular to a vibration type angular velocity sensor having a phase synchronization circuit. Background Art

[0002] Conventionally, a vibration-type angular velocity sensor including a phase-locked circuit is known. This type of vibration-type angular velocity sensor is disclosed in, for example, Japanese Patent No. 3808774.

[0003] Japanese Patent No. 3808774 describes a vibrating gyroscope equipped with a phase-locked loop (phase-synchronized circuit). This vibrating gyroscope includes a planar vibrating structure. In this planar vibrating structure, when primary vibration along a first axis on a plane is excited and the vibrating structure rotates about an axis perpendicular to the plane, the Coriolis force excites secondary vibration along a second axis inclined from the first axis. Based on these secondary vibrations, the angular velocity of the vibrating structure rotating about the axis perpendicular to the plane is measured. In the vibrating angular velocity sensor described in Japanese Patent No. 3808774, the frequency of the primary vibration excited in the vibrating structure is adjusted using a phase-synchronized circuit.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 3808774 Summary of the Invention

[0007] Technical issues to be solved by the invention

[0008] Although not explicitly described in Japanese Patent No. 3808774, the phase-locked loop (PLL) circuit described in the aforementioned Japanese Patent No. 3808774 typically includes a filter circuit. The filter circuit in a phase-locked circuit is sometimes comprised of an integrator using an operational amplifier and a capacitor. In this case, if there is a deviation, such as an error, between the two inputs of the operational amplifier, the output of the integrator may sometimes deviate when the vibrating structure (vibrator) begins to vibrate due to the integration of the deviation between the two inputs of the operational amplifier. In this case, the frequency of the signal output from the phase-locked circuit shifts, and the frequency of the drive signal input to the vibrator during startup shifts, preventing the vibrator from starting properly. Therefore, when controlling the vibration of the vibrator using a phase-locked circuit including an integrator using an operational amplifier, it is desirable to prevent this from occurring.

[0009] The present invention is completed to solve the problems mentioned above. One of the purposes of the present invention is to provide a vibration-type angular velocity sensor, which can suppress the situation where the start-up of the vibrator cannot be carried out normally when the vibration of the vibrator is controlled by a phase synchronization circuit. The phase synchronization circuit has an integrator using an operational amplifier.

[0010] Means for solving technical problems

[0011] To achieve the above-mentioned object, a vibration-type angular velocity sensor according to one aspect of the present invention includes: a vibrator; a phase synchronization circuit that outputs a frequency signal for controlling the frequency of a drive signal input to the vibrator; and a detection circuit that detects the angular velocity applied to the vibrator, wherein the phase synchronization circuit includes: a comparator that compares the detection signal from the vibrator with a reference signal generated based on the frequency signal; an integrator that includes an operational amplifier and a capacitor and outputs an integrator output signal based on the output from the comparator; an oscillator that outputs a frequency signal of a predetermined frequency based on the integrator output signal from the integrator; and a short-circuit switch that short-circuits the integrator capacitor when the vibrator is activated to bypass the integrator capacitor. The term "integrator output signal" herein includes both a signal output by the integrator after integration and a signal output from the integrator in a state where the short-circuit switch has short-circuited the integrator capacitor.

[0012] As described above, a vibration-type angular velocity sensor according to one aspect of the present invention includes a short-circuit switch portion that short-circuits when the vibrator is activated to bypass the capacitor of the integrator. Thus, when the vibrator is activated, even if there is a deviation between the two inputs of the operational amplifier, the short-circuit switch portion short-circuits to bypass the capacitor, thereby preventing the formation of an integration circuit based on the operational amplifier, thereby suppressing the integration of the deviation between the two inputs of the operational amplifier. Therefore, since the output of the integrator can be suppressed from deviating during startup, the frequency of the drive signal input to the vibrator during startup can be suppressed from shifting. As a result, when the vibration of the vibrator is controlled by a phase synchronization circuit having an integrator using an operational amplifier, it is possible to suppress the vibrator from failing to start normally.

[0013] In the vibration-type angular velocity sensor according to the above aspect, the integrator preferably includes a negative feedback circuit having a capacitor connected between the inverting input terminal and the output terminal of an operational amplifier, and the short-circuit switch section short-circuits the capacitor in the negative feedback circuit of the integrator during vibrator startup. With this configuration, in the integrator including the operational amplifier having the capacitor connected in the negative feedback circuit, the short-circuit switch section short-circuits the capacitor to bypass the capacitor, thereby preventing the formation of an integration circuit based on the operational amplifier. This prevents the integration of the deviation between the two inputs of the operational amplifier during vibrator startup. Consequently, when the vibration of the vibrator is controlled by a phase-synchronized circuit including an integrator using the operational amplifier having the capacitor connected in the negative feedback circuit, it is possible to prevent the vibrator from failing to start normally.

[0014] In this case, the short-circuit switch preferably short-circuits the inverting input terminal and output terminal of the operational amplifier in the integrator during oscillator startup. With this configuration, by using the short-circuit switch to short-circuit the inverting input terminal and output terminal of the operational amplifier, a voltage follower circuit can be formed in the integrator as a buffer circuit, which directly outputs the input applied to the non-inverting input terminal of the operational amplifier. Therefore, since the integrator can be configured as a buffer circuit, even if there is a deviation between the inputs to the inverting and non-inverting input terminals of the operational amplifier, deviations in the output of the integrator during oscillator startup can be further suppressed. As a result, failure to properly start the oscillator can be further suppressed.

[0015] In the vibration-type angular velocity sensor according to the above aspect, the short-circuit switch unit preferably switches from a short-circuit state to an open state after a predetermined time has elapsed since the vibrator was activated. With the short-circuit switch unit switched to the open state, the phase synchronization circuit outputs a frequency signal through feedback control based on a detection signal from the vibrator. With this configuration, the relatively simple control of switching the short-circuit switch unit from a short-circuit state to an open state after a predetermined time has elapsed since the vibrator was activated can prevent normal startup from occurring. Furthermore, feedback control by the phase synchronization circuit can be performed while a normal detection signal is being obtained from the vibrator after the predetermined time has elapsed since startup. Therefore, it is easy to prevent normal startup of the vibrator from occurring.

[0016] The vibration-type angular velocity sensor according to the above aspect preferably further includes an offset adjustment circuit connected to the input side of the integrator to adjust the offset between the inverting and non-inverting input terminals of the operational amplifier. The integrator outputs an integrator output signal having a predetermined voltage value based on the output from the comparator and the output from the offset adjustment circuit. When the offset adjustment circuit makes a large adjustment, the output from the offset adjustment circuit causes a relatively large deviation between the two inputs of the operational amplifier, thereby increasing the deviation in the output of the integrator during vibrator startup. Therefore, when the offset adjustment circuit adjusts the offset between the inverting and non-inverting input terminals of the operational amplifier, the short-circuit switch section bypasses the capacitor of the integrator by short-circuiting the integrator during vibrator startup, effectively suppressing any deviation in the output of the integrator. Consequently, when the offset adjustment circuit adjusts the offset between the inverting and non-inverting input terminals of the operational amplifier, it is effectively suppressed that the vibrator cannot properly start up. The term "offset" as used herein encompasses a potential difference or a current difference between the terminals.

[0017] The vibration-type angular velocity sensor according to the above aspect preferably further includes a frequency adjustment circuit connected to the input side of the oscillator and configured to adjust the frequency of a frequency signal output from the oscillator. When the oscillator is activated, the oscillator outputs a frequency signal having a predetermined activation frequency based on an integrator output signal from an integrator and an output from the frequency adjustment circuit. The integrator is short-circuited by a short-circuit switch to bypass the capacitor. With this configuration, a frequency signal having a startup frequency at a level (value) sufficient for normal oscillator activation can be easily output based on the output from the integrator and the output from the frequency adjustment circuit. The integrator is short-circuited to bypass the capacitor. This makes it easier to prevent the oscillator from activating normally.

[0018] The vibration-type angular velocity sensor according to the above aspect preferably further comprises: a primary-side control circuit including a phase synchronization circuit, which induces primary vibration in the vibrator by a drive signal; and a secondary-side control circuit including a detection circuit, wherein the phase synchronization circuit in the primary-side control circuit outputs a frequency signal through feedback control based on a detection signal detecting the primary vibration induced in the vibrator, and the detection circuit in the secondary-side control circuit detects secondary vibration generated in the vibrator due to an angular velocity applied to the vibrator. With this configuration, the vibration-type angular velocity sensor can effectively prevent the primary-side control circuit from failing to properly activate the vibrator by bypassing the capacitor by short-circuiting the capacitor during vibrator activation. The vibration-type angular velocity sensor operates using two control circuits: the primary-side control circuit for controlling vibrator drive and the secondary-side control circuit for detecting angular velocity.

[0019] The vibration-type angular velocity sensor according to the aforementioned aspect preferably further comprises an output amplifier circuit connected to the output side of the integrator and configured to output an integrator output signal from the integrator to the outside. With this configuration, the integrator output signal from the integrator can be output externally via the output amplifier circuit, thereby enabling external confirmation of the integrator output signal during vibrator activation. Therefore, by monitoring the output from the output amplifier circuit, it is possible to easily determine whether control during vibrator activation is operating normally.

[0020] In the vibration-type angular velocity sensor according to the above aspect, the vibrator preferably includes a ring-shaped vibrator. With this structure, the vibrating area can be made smaller than that of a disk-shaped vibrator of the same diameter, thereby relatively reducing the power supplied to vibrate the vibrator.

[0021] Effects of the Invention

[0022] According to the present invention, as described above, when the oscillation of the vibrator is controlled by the phase-locked circuit including the integrator using the operational amplifier, it is possible to suppress the vibrator from failing to start normally. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a block diagram showing the structure of a vibration-type angular velocity sensor according to one embodiment.

[0024] Figure 2 This is a plan view showing a state in which a vibrator of a vibration-type angular velocity sensor according to one embodiment vibrates by a single vibration.

[0025] Figure 3 This is a plan view showing a state in which a vibrator of a vibration-type angular velocity sensor according to one embodiment vibrates due to secondary vibration.

[0026] Figure 4 This is a block diagram showing the configuration of a PLL circuit.

[0027] Figure 5 This is a flowchart for explaining the operation of the vibrator when it is started. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0029] (Structure of a vibration-type angular velocity sensor)

[0030] refer to Figures 1 to 4 The structure of a vibration-type angular velocity sensor 100 according to one embodiment of the present invention will be described. Vibration-type angular velocity sensor 100 is used to detect angular velocity in digital cameras, smartphones, portable game consoles, robots, car navigation systems, and vehicles. Vibration-type angular velocity sensor 100 is, for example, a MEMS (Micro Electro Mechanical Systems) device.

[0031] like Figure 1 As shown, a vibration-type angular velocity sensor 100 includes a vibrator 10, a primary-side control circuit 20, and a secondary-side control circuit 30. The primary-side control circuit 20 includes a closed-loop control circuit that induces primary vibration in the vibrator 10 using a drive signal. The secondary-side control circuit 30 includes a closed-loop control circuit that detects the angular velocity applied to the vibrator 10 by detecting secondary vibration generated in the vibrator 10 due to the angular velocity applied to the vibrator 10. The secondary-side control circuit 30 is an example of a "detection circuit" in the claims.

[0032] like Figure 2 and Figure 3 As shown, vibrator 10 is a ring-type vibrator 10. In a vibration-type angular velocity sensor 100, the vibration of vibrator 10 changes due to a Coriolis force fc generated by applying rotational motion to vibrator 10 vibrating in a predetermined direction. Vibration-type angular velocity sensor 100 is configured to detect angular velocity based on the change in vibration of vibrator 10.

[0033] like Figure 2 As shown, the ring-shaped vibrator 10 is configured to vibrate rotationally symmetrically about the center of the vibrator 10. In response to a drive signal from the primary-side control circuit 20, a primary vibration is induced in the vibrator 10. This primary vibration alternately repeats vibration in the Y direction and vibration in the X direction, which is orthogonal to the Y direction. The primary-side control circuit 20 controls the drive signal to cause the vibrator 10 to vibrate at its natural frequency.

[0034] Then, if Figure 3As shown, the vibrator 10 vibrates in a direction inclined with respect to the X and Y directions as predetermined directions due to the Coriolis force fc generated by the application of rotational motion (for example, rotational motion generated by the rotation of a vehicle). Figure 2 As shown, when primary vibration is generated in the vibrator 10, a Coriolis force fc is generated when an angular velocity Ω is generated about an axis perpendicular to the vibrator 10 (an axis perpendicular to the paper). Due to the Coriolis force fc generated by the angular velocity applied to the vibrator 10, secondary vibration is generated in the vibrator 10 in a direction oblique to the primary vibration (see FIG. Figure 3 The secondary-side control circuit 30 inputs a drive signal to the vibrator 10 so that the signal generated by the secondary vibration is zero. Depending on the magnitude of the drive signal input to zero the signal generated by the secondary vibration, the secondary-side control circuit 30 outputs a sensor output corresponding to the angular velocity applied to the vibrator 10.

[0035] In detail, Figure 1 As shown, the primary-side control circuit 20 includes an amplifier circuit 21, a synchronous detection circuit 22, a loop filter 23, a modulation circuit 24, a drive circuit 25, a PLL (Phase Locked Loop) circuit 26, and a reference signal generation circuit 27. Furthermore, the oscillator 10, amplifier circuit 21, synchronous detection circuit 22, loop filter 23, modulation circuit 24, and drive circuit 25 are connected in sequence to form a closed control loop. The loop filter 23 includes, for example, an integration circuit. The PLL circuit 26 is an example of a "phase synchronization circuit" in the claims.

[0036] In the primary-side control circuit 20, the primary vibration detection signal output from the vibrator 10 is amplified by the amplifier circuit 21. The detection signal amplified by the amplifier circuit 21 has a sinusoidal shape. Based on the detection signal amplified by the amplifier circuit 21, the PLL circuit 26 and the reference signal generation circuit 27 generate a reference signal (synchronization signal). Details of the reference signal generation by the PLL circuit 26 and the reference signal generation circuit 27 will be described later. The generated reference signal is output to the synchronous detection circuit 22 and the modulation circuit 24. Furthermore, the generated reference signal is also output to the synchronous detection circuit 32 and the modulation circuit 34 of the secondary-side control circuit 30, described later.

[0037] The synchronous detection circuit 22 then detects the detection signal amplified by the amplifier circuit 21 based on the reference signal. The signal output from the synchronous detection circuit 22 is integrated by the loop filter 23 and output as a signal of constant magnitude. The output from the loop filter 23 is then converted to a pulsed signal by the modulation circuit 24 based on the reference signal generated by the reference signal generation circuit 27. The pulsed signal generated by the modulation circuit 24 is then input to the drive circuit 25, and the drive signal output from the drive circuit 25 induces primary vibration in the vibrator 10.

[0038] The signals in the secondary-side control circuit 30 are also the same as those in the primary-side control circuit 20. The secondary-side control circuit 30 includes an amplifier circuit 31, a synchronous detection circuit 32, a loop filter 33, a modulation circuit 34, a drive circuit 35, and an amplifier circuit 36. The vibrator 10, amplifier circuit 31, synchronous detection circuit 32, loop filter 33, modulation circuit 34, and drive circuit 35 are connected in sequence to form a closed control loop. The loop filter 33 is, for example, an integrator circuit. The output of the loop filter 33 is input to the amplifier circuit 36. The detection signal of the secondary vibration generated in the vibrator 10 is input to the secondary-side control circuit 30. Then, by performing the same control processing as the primary-side control circuit 20, a drive signal is output to the vibrator 10 so that the detection signal of the secondary vibration is substantially zero. Furthermore, the signal output from the amplifier circuit 36 ​​is output in the secondary-side control circuit 30 as a sensor output indicating the magnitude of the angular velocity applied to the vibrator 10.

[0039] <Details of generating a reference signal>

[0040] like Figure 4 As shown, PLL circuit 26 outputs a frequency signal used to control the frequency of the drive signal input to vibrator 10. Reference signal generation circuit 27 outputs a reference signal based on the frequency signal from PLL circuit 26. PLL circuit 26 and reference signal generation circuit 27 perform control such that a frequency signal for vibrating vibrator 10 at a predetermined frequency is output through feedback control based on a detection signal that detects a single oscillation of vibrator 10. PLL circuit 26 includes a comparator 41, an integrator 42, an oscillator 43, a short-circuit switch 44, an offset adjustment circuit 45, a frequency adjustment circuit 46, and an output amplifier circuit 47.

[0041] Comparator 41 compares the detection signal from a single vibration of vibrator 10 with a reference signal. Specifically, comparator 41 compares the detection signal from a single vibration of vibrator 10, amplified by amplifier circuit 21, with the reference signal generated by reference signal generation circuit 27. Comparator 41 is a phase comparator that compares the phases of the detection signal and the reference signal. Comparator 41 outputs a comparison signal, the result of the comparison between the detection signal and the reference signal, to integrator 42. The comparison signal represents the phase difference between the detection signal and the reference signal.

[0042] Integrator 42 outputs an integrator output signal based on the output from comparator 41. Integrator 42 includes an operational amplifier 50, a resistor 60, and a capacitor 70. Operational amplifier 50 is an operational amplifier (OP amp). It has two input terminals, an inverting input terminal 51 and a non-inverting input terminal 52, and an output terminal 53. Operational amplifier 50 is an integrated circuit configured to amplify the potential difference between its two inputs, the inverting input terminal 51 and the non-inverting input terminal 52, and output the amplified signal through output terminal 53. In this embodiment, integrator 42 includes a negative feedback circuit with capacitor 70 connected between the inverting input terminal 51 and the output terminal 53 of operational amplifier 50. Specifically, integrator 42 forms an integration circuit comprised of operational amplifier 50 (OP amp) and capacitor 70. Resistor 60 and capacitor 70 are connected in series in the negative feedback circuit of operational amplifier 50 in integrator 42. Integrator 42 outputs an integrator output signal, obtained by integrating the comparison signal output from comparator 41, to oscillator 43. In the operational amplifier 50 , the comparison signal from the comparator 41 is input to the inverting input terminal 51 . A reference potential of a constant magnitude is applied to the non-inverting input terminal 52 .

[0043] Furthermore, an offset adjustment circuit 45 is connected to the input side of the integrator 42. The offset adjustment circuit 45 adjusts the offset, which is the potential difference or current difference between the inverting input terminal 51 and the non-inverting input terminal 52. The offset adjustment circuit 45 is connected to the inverting input terminal 51 of the operational amplifier 50 and outputs an offset adjustment signal to the inverting input terminal 51. This offset adjustment signal is a DC signal of a predetermined magnitude. Therefore, the integrator 42 integrates the input signal, which is a composite of the comparison signal (output from the comparator 41) and the offset adjustment signal (output from the offset adjustment circuit 45), based on the comparison signal and the offset adjustment signal. This outputs an integrator output signal having a predetermined voltage value. The offset adjustment signal has a value set to appropriately perform feedback control in the PLL circuit 26. Therefore, the offset adjustment signal is not limited to adjusting to eliminate the offset (potential difference or current difference) between the inverting input terminal 51 and the non-inverting input terminal 52. The offset adjustment signal, which is an output from the offset adjustment circuit 45 , is a signal for adjusting the phase of the reference signal, for example.

[0044] An output amplifier circuit 47 is connected to the output side of integrator 42. Output amplifier circuit 47 is provided to output the integrator output signal from integrator 42 to the outside. Output amplifier circuit 47 amplifies the input integrator output signal and outputs it. For example, output amplifier circuit 47 includes an amplifier circuit using an operational amplifier (op amp).

[0045] Oscillator 43 outputs a frequency signal of a predetermined frequency based on the integrator output signal from integrator 42. Oscillator 43 is, for example, a voltage-controlled oscillator (VCO), whose oscillation frequency varies according to the input voltage. Oscillator 43 outputs a frequency signal having a frequency corresponding to the input voltage. The frequency signal is, for example, a pulse signal.

[0046] Furthermore, a frequency adjustment circuit 46 is connected to the input side of oscillator 43. Frequency adjustment circuit 46 outputs a frequency adjustment signal used to adjust the frequency value of the frequency signal output from oscillator 43. Frequency adjustment circuit 46 outputs the frequency adjustment signal, a DC signal of a predetermined magnitude. Specifically, the integrator output signal from integrator 42 and the frequency adjustment signal output from frequency adjustment circuit 46 are input to oscillator 43. Oscillator 43 receives a signal synthesized from the integrator output signal from integrator 42 and the frequency adjustment signal from frequency adjustment circuit 46, and outputs a frequency signal having a frequency corresponding to the input signal. The frequency signal output from oscillator 43 is output to reference signal generation circuit 27. In PLL circuit 26, the frequency of the output frequency signal is controlled through feedback control based on the primary vibration detection signal amplified by amplifier circuit 21, thereby causing vibrator 10 to vibrate at its natural frequency. For example, in this embodiment, the frequency of the reference signal from reference signal generation circuit 27 becomes the frequency of the drive signal input to vibrator 10. The frequency of a single oscillation of vibrator 10 is approximately equal to the frequency of the drive signal. Furthermore, the frequency of the frequency signal from oscillator 43 serves as a reference value for the reference signal from reference signal generation circuit 27 and the drive signal input to vibrator 10. For example, reference signal generation circuit 27 includes a frequency divider that generates a reference signal based on the frequency signal from oscillator 43. This reference signal has a frequency that is an integer fraction of the frequency of the frequency signal. Therefore, the frequency of the frequency signal from oscillator 43 becomes a multiple (n times, where n is an integer) of the frequency of the reference signal. Therefore, the frequency of the reference signal is controlled by controlling the frequency of the frequency signal output from oscillator 43. In this embodiment, the frequency signal is controlled through feedback control in PLL circuit 26 so that the frequency of the reference signal from reference signal generation circuit 27 matches the natural frequency of vibrator 10.

[0047] The magnitude (voltage or current value) of the offset adjustment signal output from the offset adjustment circuit 45 and the magnitude (voltage or current value) of the frequency adjustment signal output from the frequency adjustment circuit 46 are preset and stored in a storage unit such as a nonvolatile memory. The magnitude of the frequency adjustment signal is preset, for example, by monitoring the signal from the output amplifier circuit 47. In other words, to set the output from the frequency adjustment circuit 46, the output amplifier circuit 47 outputs the integrator output signal, which is the output from the integrator 42, to the outside.

[0048] In this embodiment, the PLL circuit 26 is provided with a short-circuit switch 44 to ensure normal operation during the startup of the oscillator 10. In this embodiment, the short-circuit switch 44 short-circuits the capacitor 70 in the negative feedback circuit of the integrator 42 when the oscillator 10 is started, thereby bypassing the capacitor 70. Specifically, the short-circuit switch 44 short-circuits the inverting input terminal 51 and the output terminal 53 of the operational amplifier 50 in the integrator 42 when the oscillator 10 is started. In other words, the short-circuit switch 44 is connected in parallel with the operational amplifier 50 between the inverting input terminal 51 and the output terminal 53 of the operational amplifier 50. The short-circuit switch 44 switches the conduction (on / off) of the circuit based on an input signal. The short-circuit switch 44 includes, for example, an analog switch.

[0049] <Activating the Vibrator>

[0050] Next, refer to Figure 5 , a method of starting the oscillator 10 will be described. Specifically, the operation of the PLL circuit 26 when the oscillator 10 is started will be described.

[0051] First, in step S1, the activation of the vibrator 10 begins. For example, power is supplied to the vibration-type angular velocity sensor 100 from a control device such as a CPU (Central Processing Unit) (not shown). When the vibrator 10 is activated, the short-circuit switch 44 is turned on (short-circuited). Since the short-circuit switch 44 is in the short-circuit state during activation, the resistor 60 and capacitor 70 of the operational amplifier 50 of the integrator 42 are bypassed, and the inverting input terminal 51 and output terminal 53 are short-circuited. Consequently, the integrator 42 does not form an integrating circuit, but instead forms a voltage follower circuit as a buffer circuit, which directly outputs the input applied to the non-inverting input terminal 52 of the operational amplifier 50. Therefore, when the vibrator 10 is activated, the reference potential applied to the non-inverting input terminal 52 is directly output from the integrator 42. That is, when the vibrator 10 is activated, the integrator output signal from the integrator 42 becomes a DC signal having the reference potential.

[0052] Therefore, in this embodiment, when vibrator 10 starts up, oscillator 43 outputs a frequency signal having a predetermined starting frequency based on the integrator output signal from integrator 42, which is short-circuited by short-circuit switch 44 to bypass capacitor 70, and the output from frequency adjustment circuit 46. Specifically, when vibrator 10 starts up, oscillator 43 receives a signal that is a composite of the integrator output signal having a reference potential and a frequency adjustment signal of a predetermined magnitude from frequency adjustment circuit 46, thereby outputting a frequency signal having a predetermined starting frequency. In other words, the signal output from frequency adjustment circuit 46 is preset so that, when vibrator 10 starts up, oscillator 43 outputs a frequency signal having the predetermined starting frequency. The starting frequency is a level (value) such that the frequency of the primary vibration induced in vibrator 10 is close to the natural frequency of vibrator 10. In this embodiment, the frequency of a single oscillation of vibrator 10 (vibration frequency) is approximately equal to the frequency of a reference signal generated by reference signal generation circuit 27 based on the frequency signal output from oscillator 43. Therefore, the starting frequency is set to a level (numerical value) such that the frequency of the reference signal is close to the natural frequency of vibrator 10. The term "close to the natural frequency" used herein is intended to encompass a value equal to the natural frequency.

[0053] Furthermore, when vibrator 10 is activated, no vibration is induced in vibrator 10, so the drive signal from vibrator 10 is not detected, or the output drive signal is extremely low. Therefore, if there is a mismatch between the two inputs of operational amplifier 50, and short-circuit switch 44 is not in the short-circuit state (on state), a normal comparison signal cannot be obtained from comparator 41. Since the offset adjustment signal from offset adjustment circuit 45 is integrated in integrator 42, the integrator output signal from integrator 42 may have a mismatched value. In this case, the frequency signal output from oscillator 43 has a value different from the activation frequency. In other words, oscillator 43 does not output a frequency signal having a startup frequency at a level (value) that causes vibrator 10 to vibrate at a frequency close to the natural frequency, and the reference signal generated by reference signal generation circuit 27 does not have a value close to the natural frequency of vibrator 10. Since the vibration-type angular velocity sensor 100 is configured so that feedback control functions normally when the vibrator 10 vibrates at a value close to the natural frequency, the vibrator 10 cannot be properly activated unless a frequency signal having a frequency close to the natural frequency is output to generate a reference signal. In this embodiment, when the vibrator 10 is activated, the short-circuit switch 44 is in a short-circuited state, and the integrator 42 outputs an integrator output signal having a reference potential. This prevents the vibrator 10 from being properly activated.

[0054] Next, in step S2, the short-circuit switch 44 switches from the short-circuit state to the open state. In this embodiment, the short-circuit switch 44 switches from the short-circuit state to the open state after a predetermined time has elapsed since the start of the vibrator 10. For example, by using a reset circuit that switches a signal after a predetermined time has elapsed, the short-circuit switch 44 switches from the on state to the off state after a predetermined time has elapsed since the start of the vibrator 10. The predetermined time may be, for example, several hundred milliseconds.

[0055] In this embodiment, when short-circuit switch section 44 is switched to an open state, PLL circuit 26 outputs a frequency signal through feedback control based on a detection signal from vibrator 10. Specifically, a detection signal from a primary vibration of vibrator 10, which is vibrating at a frequency close to the natural frequency, is input to PLL circuit 26. Comparator 41 compares the phase of the detection signal with a reference signal from reference signal generation circuit 27, thereby controlling the frequency signal through feedback control so that the frequency of the reference signal reaches the natural frequency.

[0056] [Effects of this embodiment]

[0057] In this embodiment, the following effects can be obtained.

[0058] In this embodiment, as described above, the PLL circuit 26 (phase synchronization circuit) of the vibration-type angular velocity sensor 100 includes a short-circuit switch 44. This short-circuit switch 44 short-circuits during the startup of the vibrator 10, bypassing the capacitor 70 of the integrator 42. Consequently, even if there is a deviation between the two inputs of the operational amplifier 50 during startup, the short-circuit switch 44 short-circuits the capacitor 70, preventing the formation of an integration circuit based on the operational amplifier 50. This prevents the integration of the deviation between the two inputs of the operational amplifier 50. Consequently, since the output of the integrator 42 can be suppressed during startup, the frequency of the drive signal input to the vibrator 10 can be suppressed from shifting during startup. Consequently, when the vibration of the vibrator 10 is controlled by the PLL circuit 26 (phase synchronization circuit) including the integrator 42 using the operational amplifier 50, it is possible to prevent the vibrator 10 from failing to start normally.

[0059] Furthermore, in this embodiment, as described above, the integrator 42 includes a negative feedback circuit with a capacitor 70 connected between the inverting input terminal 51 and the output terminal 53 of the operational amplifier 50. The short-circuit switch 44 short-circuits the capacitor 70 in the negative feedback circuit of the integrator 42 during startup of the oscillator 10. Thus, in the integrator 42 including the operational amplifier 50 with the capacitor 70 connected in the negative feedback circuit, the short-circuit switch 44 short-circuits the capacitor 70 to bypass it. This prevents the formation of an integration circuit based on the operational amplifier 50, thereby suppressing the integration of the deviation between the two inputs of the operational amplifier 50 during startup of the oscillator 10. Consequently, when the oscillation of the oscillator 10 is controlled by the PLL circuit 26 (phase synchronization circuit) including the integrator 42 using the operational amplifier 50 with the capacitor 70 connected in the negative feedback circuit, it is possible to suppress the normal startup of the oscillator 10.

[0060] Furthermore, in this embodiment, as described above, the short-circuit switch section 44 short-circuits the inverting input terminal 51 and the output terminal 53 of the operational amplifier 50 in the integrator 42 during startup of the oscillator 10. Thus, by short-circuiting the inverting input terminal 51 and the output terminal 53 of the operational amplifier 50 using the short-circuit switch section 44, a voltage follower circuit, acting as a buffer circuit, can be formed in the integrator 42. This circuit directly outputs the input applied to the non-inverting input terminal 52 of the operational amplifier 50. Therefore, since the integrator 42 can be configured as a buffer circuit, even if there is a deviation between the inputs to the inverting input terminal 51 and the non-inverting input terminal 52 of the operational amplifier 50, it is possible to further suppress any deviation in the output of the integrator 42 during startup of the oscillator 10. Consequently, it is possible to further suppress any failure to properly start the oscillator 10.

[0061] Furthermore, in this embodiment, as described above, the short-circuit switch unit 44 switches from a short-circuit state to an open state after a predetermined time has elapsed since the start-up of the vibrator 10. This switching of the short-circuit switch unit 44 to the open state causes the PLL circuit 26 (phase synchronization circuit) to output a frequency signal through feedback control based on the detection signal from the vibrator 10. Thus, the relatively simple control of switching the short-circuit switch unit 44 from a short-circuit state to an open state after a predetermined time has elapsed since the start-up of the vibrator 10 can prevent normal startup failures. Furthermore, feedback control by the PLL circuit 26 can be performed while a normal detection signal is being obtained from the vibrator 10 after the predetermined time has elapsed since the start-up. Consequently, it is possible to easily prevent normal startup failures of the vibrator 10.

[0062] Furthermore, in this embodiment, as described above, the vibration-type angular velocity sensor 100 includes an offset adjustment circuit 45 connected to the input side of the integrator 42 and adjusting the offset between the inverting input terminal 51 and the non-inverting input terminal 52 of the operational amplifier 50. The integrator 42 outputs an integrator output signal having a predetermined voltage value based on the output from the comparator 41 and the output from the offset adjustment circuit 45. When the amount of adjustment by the offset adjustment circuit 45 is large, the output from the offset adjustment circuit 45 causes a relatively large deviation between the two inputs of the operational amplifier 50, thereby increasing the deviation in the output of the integrator 42 during the startup of the vibrator 10. Therefore, when the offset adjustment circuit 45 adjusts the offset between the inverting input terminal 51 and the non-inverting input terminal 52 of the operational amplifier 50, the short-circuiting switch 44 bypasses the capacitor 70 of the integrator 42 by short-circuiting the capacitor 70 during the startup of the vibrator 10, effectively suppressing deviation in the output of the integrator 42. As a result, when the offset between the inverting input terminal 51 and the non-inverting input terminal 52 of the operational amplifier 50 is adjusted by the offset adjustment circuit 45 , it is possible to effectively prevent the oscillator 10 from failing to start normally.

[0063] Furthermore, in this embodiment, as described above, the vibration-type angular velocity sensor 100 includes a frequency adjustment circuit 46 connected to the input side of the oscillator 43 to adjust the frequency of the frequency signal output from the oscillator 43. When the vibrator 10 is activated, the oscillator 43 outputs a frequency signal having a predetermined activation frequency based on the integrator output signal from the integrator 42, which is short-circuited by the short-circuiting switch 44 to bypass the capacitor 70, and the output from the frequency adjustment circuit 46. This facilitates outputting a frequency signal having a startup frequency at a level (value) sufficient for normal activation of the vibrator 10, based on the output from the integrator 42 and the output from the frequency adjustment circuit 46, which is short-circuited to bypass the capacitor 70. Consequently, it is possible to easily prevent the vibrator 10 from failing to properly activate.

[0064] Further, in the present embodiment, as described above, the vibration type angular velocity sensor 100 is provided with the primary side control circuit 20 including the PLL circuit 26 (phase synchronization circuit) and the secondary side control circuit 30 (detection circuit) that induces the primary vibration in the vibrator 10 by the drive signal. The PLL circuit 26 in the primary side control circuit 20 outputs the frequency signal by the feedback control based on the detection signal that detects the primary vibration induced in the vibrator 10, and the secondary side control circuit 30 (detection circuit) detects the secondary vibration generated in the vibrator 10 due to the angular velocity applied to the vibrator 10. Thus, in the vibration type angular velocity sensor 100 that operates by the two control circuits of the primary side control circuit 20 that controls the drive of the vibrator 10 and the secondary side control circuit 30 that detects the angular velocity, the situation that the start of the vibrator 10 based on the primary side control circuit 20 cannot be normally performed can be effectively suppressed by bypassing the capacitor 70 by short-circuiting using the short-circuiting switch section 44 at the start of the vibrator 10.

[0065] Further, in the present embodiment, as described above, the vibration type angular velocity sensor 100 is provided with the output amplification circuit 47 connected to the output side of the integrator 42 for outputting the integrator output signal from the integrator 42 to the outside. Thus, the integrator output signal from the integrator 42 can be output to the outside by the output amplification circuit 47, and thus the integrator output signal at the start of the vibrator 10 can be confirmed from the outside. Therefore, by monitoring the output from the output amplification circuit 47, it is possible to easily determine whether the control at the start of the vibrator 10 is normally performed.

[0066] Further, in the present embodiment, as described above, the vibrator 10 includes the ring type vibrator 10. Thus, the area of the vibration can be made smaller than that of the circular plate shaped vibrator 10 of the same diameter, and thus the power supplied to vibrate the vibrator 10 can be relatively reduced.

[0067] (Modified Example)

[0068] It should be understood that the embodiments disclosed herein are examples in all aspects and are not restrictive. The scope of the present application should be defined by the claims rather than the description of the embodiments. Furthermore, the scope thereof includes all modifications (modified examples) within the same meaning and range of the claims.

[0069] For example, in the above embodiment, an example is shown in which a negative feedback circuit consisting of a resistor 60 and a capacitor 70 connected in series is formed between the inverting input terminal 51 and the output terminal 53 in the integrator 42 of the PLL circuit 26 (phase synchronization circuit). However, the present invention is not limited to this embodiment. In the present invention, the integrator of the phase synchronization circuit may be composed of a circuit other than an integrator circuit having a capacitor connected in a negative feedback circuit. Furthermore, the integrator may form a negative feedback circuit in which only a capacitor is connected between the inverting input terminal and the output terminal of the operational amplifier, without a resistor. Furthermore, the integrator may have a resistor connected in parallel with the capacitor, or a capacitor may be connected in parallel with the resistor connected in series with the capacitor.

[0070] Furthermore, in the above embodiment, an example is shown in which the short-circuiting switch 44 is connected to short-circuit the inverting input terminal 51 and the output terminal 53 of the operational amplifier 50. However, the present invention is not limited to this. In the present invention, the short-circuiting switch can be connected to bypass only the capacitor. In other words, when a resistor and a capacitor are connected in series, the short-circuiting switch can be connected to short-circuit the input and output sides of the capacitor, thereby bypassing only the capacitor and not the resistor.

[0071] Furthermore, in the above embodiment, an example is shown in which the short-circuit switch unit 44 is switched from the short-circuit state to the open state after a predetermined time has elapsed since the start-up of the vibrator 10. However, the present invention is not limited to this. In the present invention, the short-circuit switch unit can be switched from the short-circuit state to the open state based on a detection signal generated by a single vibration of the vibrator. For example, the short-circuit switch unit can be switched between the on (short-circuit state) and off (open state) state after a predetermined time has elapsed since the start-up of the vibrator, controlled by a computing device such as a microcomputer (microcontroller). Furthermore, the short-circuit switch unit can be switched to the open state based on a detection signal generated by a single vibration of the vibrator, upon confirming that the vibrator is vibrating at a predetermined frequency.

[0072] Furthermore, while the above embodiment illustrates an example in which the offset adjustment circuit 45 is connected to the input side of the integrator 42, the present invention is not limited thereto. In the present invention, the offset adjustment circuit need not be connected to the input side of the integrator. In this case, input errors in the integrator's operational amplifier itself may cause output deviations. Therefore, by short-circuiting the short-circuit switch section during oscillator startup, this can prevent the oscillator from failing to start normally.

[0073] Furthermore, while the above embodiment illustrates an example in which the frequency adjustment circuit 46 is connected to the input side of the oscillator 43, the present invention is not limited thereto. In the present invention, the frequency adjustment circuit need not be connected to the input side of the oscillator. For example, if the output from the integrator during oscillator startup is an appropriate output for outputting a frequency signal at the startup frequency from the oscillator, the frequency adjustment circuit need not be connected.

[0074] Furthermore, the above embodiment shows an example of a closed-loop control circuit comprising two components: a primary-side control circuit 20 and a secondary-side control circuit 30. The primary-side control circuit 20 comprises an oscillator 10, an amplifier circuit 21, a synchronous detection circuit 22, a loop filter 23, a modulation circuit 24, and a drive circuit 25. The secondary-side control circuit 30 comprises an oscillator 10, an amplifier circuit 31, a synchronous detection circuit 32, a loop filter 33, a modulation circuit 34, and a drive circuit 35. The PLL circuit 26 is included in the primary-side control circuit 20, but the present invention is not limited to this. In the present invention, a control loop may be constructed using a configuration other than a configuration comprising an amplifier circuit, a synchronous detection circuit, a loop filter, a modulation circuit, and a drive circuit. Furthermore, the above embodiment shows an example of using integrating circuits as loop filters 23 and 33. However, loop filters other than integrating circuits may also be used.

[0075] Furthermore, while the above embodiment illustrates an example in which the output amplifier circuit 47 is connected to the output side of the integrator 42, the present invention is not limited thereto. In the present invention, the output amplifier circuit need not be connected to the output side of the integrator. Furthermore, when the integrator output signal from the integrator is output externally, an output circuit that does not include an amplifier may be connected to the output side of the integrator.

[0076] Furthermore, while the above embodiment illustrates an example in which the vibrator 10 is ring-shaped, the present invention is not limited thereto. In the present invention, the vibrator 10 may be configured to have a circular plate shape, a polygonal plate shape, a polygonal ring shape, or a polygonal shape. Furthermore, the vibrator may also be configured to have a tuning fork shape, an H shape, or a wine glass shape.

[0077] Furthermore, in the above embodiment, the short-circuit switch unit 44 is shown as an analog switch, but the present invention is not limited to this. In the present invention, the short-circuit switch unit can be a mechanical relay or a semiconductor relay including a switching element such as a MOSFET (metal-oxide-semiconductor field-effect transistor).

[0078] Explanation of symbols

[0079] 10 - Oscillator, 20 - Primary-side control circuit, 26 - PLL circuit (phase synchronization circuit), 30 - Secondary-side control circuit (detection circuit), 41 - Comparator, 42 - Integrator, 43 - Oscillator, 44 - Short-circuit switch section, 45 - Offset adjustment circuit, 46 - Frequency adjustment circuit, 47 - Output amplifier circuit, 50 - Operational amplifier, 51 - Inverting input terminal, 52 - Non-inverting input terminal, 53 - Output terminal, 70 - Capacitor, 100 - Vibration-type angular velocity sensor.

Claims

1. A vibration-type angular velocity sensor comprising: vibrator; a phase synchronization circuit that outputs a frequency signal for controlling the frequency of a drive signal input to the vibrator; and a detection circuit for detecting an angular velocity applied to the vibrator, The phase synchronization circuit comprises: a comparator for comparing the detection signal from the vibrator with a reference signal generated according to the frequency signal; an integrator having an operational amplifier and a capacitor, and outputting an integrator output signal based on the output from the comparator; an oscillator that outputs the frequency signal of a predetermined frequency based on the integrator output signal from the integrator; and The short-circuit switch section performs short-circuiting when the oscillator is activated to bypass the capacitor of the integrator.

2. The vibration type angular velocity sensor according to claim 1, wherein The integrator includes a negative feedback circuit in which the capacitor is connected between the inverting input terminal and the output terminal of the operational amplifier. The short-circuit switch section performs short-circuiting when the oscillator is activated to bypass the capacitor in the negative feedback circuit of the integrator.

3. The vibration type angular velocity sensor according to claim 2, wherein: The short-circuit switch section short-circuits the inverting input terminal and the output terminal of the operational amplifier in the integrator when the oscillator is activated.

4. The vibration type angular velocity sensor according to claim 1, wherein The short-circuit switch unit switches from a short-circuit state to an open state after a predetermined time has passed since the vibrator is activated. When the short-circuit switch unit is switched to an open state, the phase synchronization circuit outputs the frequency signal through feedback control based on the detection signal from the oscillator.

5. The vibration type angular velocity sensor according to claim 1, wherein Also features: An offset adjustment circuit is connected to the input side of the integrator and adjusts the offset between the inverting input terminal and the non-inverting input terminal of the operational amplifier. The integrator outputs the integrator output signal having a predetermined voltage value based on the output from the comparator and the output from the offset adjustment circuit.

6. The vibration type angular velocity sensor according to claim 1, wherein Also features: A frequency adjustment circuit, connected to the input side of the oscillator, for adjusting the frequency of the frequency signal output from the oscillator, When the oscillator is started, the oscillator outputs the frequency signal having a predetermined starting frequency based on the integrator output signal from the integrator and the output from the frequency adjustment circuit. The integrator is short-circuited by the short-circuit switch unit to bypass the capacitor.

7. The vibration type angular velocity sensor according to claim 1, wherein Also features: a primary-side control circuit including the phase synchronization circuit and inducing primary vibration in the vibrator by the drive signal; and The secondary side control circuit includes the detection circuit, The phase synchronization circuit in the primary side control circuit outputs the frequency signal through feedback control based on the detection signal of the primary vibration induced in the vibrator. The detection circuit in the secondary-side control circuit detects secondary vibration generated in the vibrator due to an angular velocity applied to the vibrator.

8. The vibration type angular velocity sensor according to claim 1, wherein Also features: The output amplifier circuit is connected to the output side of the integrator and is used to output the integrator output signal from the integrator to the outside.

9. The vibration type angular velocity sensor according to claim 1, wherein The vibrator includes a ring-type vibrator.

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