JP2008089572A - Drive device, physical quantity measuring device and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit capable of operating in a sleep mode and shortening the oscillation staring time without increasing circuit size, and provide a physical quantity measuring apparatus and an electronic apparatus using the same. <P>SOLUTION: An oscillation drive circuit 10 includes both a gain control amplifier 20 for exciting driving oscillations at an oscillator 12 by controlling the oscillation amplitude in an oscillation loop and a comparator 50 for generating reference signals of synchronous detection on the basis of signals in the oscillation loop. The oscillation drive circuit 10 in first operating mode uses output of the comparator, increases a gain in an oscillation loop formed by the oscillator 12 and the comparator 50 to one or greater; and then controls the oscillation amplitude in an oscillation loop formed by the oscillator 12 and the gain control amplifier 20 to excite driving oscillations at the oscillator 12. The oscillation drive circuit 10 in second operating mode excites driving oscillations at the oscillator 12 in an oscillation loop formed by the oscillator 12 and the comparator 50. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drive device for exciting drive vibration in a vibrator, and a physical quantity measuring device using the drive device, for example, a vibratory gyroscope and an electronic apparatus.

  A so-called gyroscope includes a rotation type and a vibration type depending on a detection method of a force acting on an object. Among them, the vibration type gyroscope is advantageous for downsizing and cost reduction from the viewpoint of components and the like. Among such vibrating gyroscopes, a vibrating gyro sensor that detects an angular velocity acting on an object includes a piezoelectric vibrating gyro sensor that excites a crystal or a piezoelectric element that is advantageous for reliability and downsizing. The piezoelectric vibration type gyro sensor utilizes the fact that when an angular velocity is applied to a vibrating object, a Coriolis force is generated in a direction perpendicular to the vibration.

  The vibration gyro sensor is applied to a wide range of applications, such as camera shake detection of video cameras and digital cameras, GPS (Global Positioning System) position detection of car navigation systems, and attitude detection of aircraft and robots.

  In such applications, the vibratory gyro sensor is driven by a battery. Therefore, it is necessary to reduce the power consumption of the vibration type gyro sensor as much as possible and to extend the battery life. In this case, it is preferable that the power supply to the vibration type gyro sensor is stopped during a period when the angular velocity is not detected, and the power is supplied from the battery only during the period when the vibration type gyro sensor is used. Therefore, it is necessary to perform normal operation in a short time after the vibration type gyro sensor is activated.

Techniques for shortening the startup time of such a vibration type gyro sensor are disclosed in, for example, Patent Document 1 and Patent Document 2. Patent Document 1 discloses a technique in which an oscillation amplitude is increased by an amplifier even immediately after startup by a configuration in which a CR oscillation circuit or a ring oscillator is added in an oscillation loop. Patent Document 2 discloses a technique in which a time until a signal from a vibrator is stabilized is shortened by a configuration in which a resistor is added in series with a crystal vibrator.
JP 2004-286503 A JP 2003-240556 A

  By the way, in order to stably detect the angular velocity acting on the vibrator, the vibratory gyro sensor drive device needs to vibrate (oscillate) the vibrator at a constant resonance frequency. In addition, the vibrator needs to oscillate in a short time to start normal operation. Furthermore, in order to extend the life of the battery at a low cost, it is preferable to configure the circuit with a small size and low power consumption.

  On the other hand, for example, when the vibrator is formed of quartz having a high Q value and the vibrator is vacuum-sealed in a package, the driving Q value of the vibrator becomes very high. Therefore, when driving vibration is excited in the vibrator, there is a problem that the time (start-up time) until the signal from the vibrator is stabilized becomes long.

  Also, for the purpose of reducing the power consumption of the drive device, the operation of unnecessary circuits is stopped except when necessary, while the operation mode of the drive device is provided with a so-called sleep mode in order to return to normal operation at high speed when necessary. Sometimes. In particular, when a crystal resonator is oscillated, the Q value is high and the oscillation start-up time is long. Therefore, in order to shorten the return time to the normal operation, it is necessary to continue the oscillation of the crystal resonator at least.

  However, in the technique of Patent Document 1, when an oscillation is made at a frequency close to the driving frequency of the crystal resonator, the element areas of the capacitors and resistors of the CR oscillation circuit increase. For this reason, there is a problem that the vibration gyroscope (vibration gyro sensor) is increased in size and cost. Further, in the technique of Patent Document 1, since it is once activated at a different frequency at the time of activation, it is difficult to draw in the driving frequency of a crystal resonator having a high Q value. For this reason, there is a problem that the time until stable oscillation is further increased under the influence of manufacturing variations. Therefore, the technique of Patent Document 1 has a problem that even if the sleep mode is provided, the startup time becomes long and the power consumption increases.

  In the technique of Patent Document 2, it is necessary to insert a resistor. In general, when a resistor is formed in an integrated circuit device, there is a problem that manufacturing variation of the resistor is large and it is difficult to give desired energy to the vibrator. Furthermore, the technique of Patent Document 2 has a problem that the gain is lost because the energy given to the vibrator is divided by the resistor. Therefore, in the technique of Patent Document 2, there is a problem that even if the sleep mode is provided, the startup time is prolonged and the power consumption is increased due to the loss of gain.

  The present invention has been made in view of the technical problems as described above. The object of the present invention is to oscillate without increasing the circuit scale even when returning from the so-called sleep mode or starting oscillation. It is an object of the present invention to provide a drive device capable of shortening the startup time, a physical quantity measuring device using the drive device, and an electronic apparatus.

In order to solve the above problems, the present invention
When measuring a physical quantity using an output signal obtained by synchronously detecting a detection signal output from the vibrator based on a drive vibration excited by the vibrator and a physical quantity to be measured, an oscillation loop is formed with the vibrator. A drive device for exciting drive vibration to the vibrator,
A gain control amplifier that controls the oscillation amplitude in the oscillation loop to excite drive vibration in the vibrator;
A comparator that generates a reference signal for the synchronous detection based on a signal in the oscillation loop;
In the state set to the first operation mode, the output of the comparator is used to increase the gain in the oscillation loop formed by the vibrator and the comparator to greater than 1, and then the vibrator and the gain control Control the oscillation amplitude in the oscillation loop formed by the amplifier to excite the drive vibration in the vibrator,
In the state set to the second operation mode, the present invention relates to a drive device that excites drive vibration in the vibrator in an oscillation loop formed by the vibrator and the comparator.

In the drive device according to the present invention,
Including an oscillation detector for detecting a signal from the vibrator;
In the state set in the first operation mode, formed by the vibrator and the gain control amplifier from the oscillation loop formed by the vibrator and the comparator based on the detection result of the oscillation detector. Can be switched to the oscillation loop.

In the drive device according to the present invention,
The oscillation detector is
From the oscillation loop formed by the vibrator and the comparator, by the vibrator and the gain control amplifier, on the condition that the direct current voltage converted from the current flowing through the vibrator has reached a given threshold voltage. It is possible to switch to the oscillation loop that is formed.

  In any one of the above inventions, when measuring a physical quantity using an output signal obtained by synchronously detecting a detection signal output from the vibrator based on a drive vibration excited by the vibrator and a physical quantity to be measured, A driving device forms an oscillation loop with the vibrator and is used to excite driving vibration in the vibrator. According to any one of the above-described inventions, in the state where the first operation mode is set, the signal in the oscillation loop is amplified using the comparator that generates the reference signal for synchronous detection when oscillation starts. When the oscillation is in a steady state, the oscillation loop is switched. Thereafter, the oscillation amplitude in the oscillation loop is controlled by the gain control amplifier. As a result, it is possible to realize synchronous detection processing and faster oscillation start-up. Furthermore, in the state set to the second operation mode, the oscillation state is maintained in the oscillation loop formed by the vibrator and the comparator. Therefore, in the state set to the second operation mode, it is not necessary to operate the circuit portion that performs oscillation control in the first operation mode. Therefore, both low power consumption in the second operation mode and high-speed oscillation start-up when the second operation mode is canceled can be achieved.

In the drive device according to the present invention,
A gain control circuit for controlling the gain of the gain control amplifier based on an oscillation signal in the oscillation loop;
In the state set to the second operation mode, the operation of the gain control circuit can be set to the disabled state without setting the operations of the gain control amplifier and the comparator to the disabled state.

  According to the present invention, in the state set in the first operation mode, when oscillation is started, a signal in the oscillation loop is amplified using a comparator that generates a reference signal for synchronous detection, and the oscillation is in a steady state. The oscillation loop is switched. Thereafter, the oscillation amplitude in the oscillation loop is controlled by the gain control amplifier. As a result, it is possible to realize synchronous detection processing and faster oscillation start-up. Further, in the state set to the second operation mode, the oscillation state is maintained in the oscillation loop formed by the vibrator and the comparator, and the operation of the gain control circuit is stopped. It is possible to achieve both low power consumption in the second operation mode and high-speed oscillation start-up when the second operation mode is canceled.

In the drive device according to the present invention,
When an oscillation loop is formed by the vibrator and the comparator, the vibrator is excited using the output of the comparator,
When an oscillation loop is formed by the vibrator and the gain control amplifier, the output of the comparator can be used as a clock for synchronous detection for generating the output signal.

  According to the present invention, it is possible to perform switching control of the switch element by diverting a signal detection result from a vibrator generally used for performing oscillation control of the oscillation loop, so that the circuit scale is not increased. Thus, it is possible to realize synchronous detection processing and high-speed oscillation start-up.

In the drive device according to the present invention,
The polarity of the output of the gain control amplifier and the polarity of the output of the comparator may be the same.

  According to the present invention, it is not necessary to add a circuit for inverting the polarity, and an increase in circuit scale can be suppressed.

A physical quantity measuring device for measuring a physical quantity corresponding to a detection signal output from the vibrator based on a drive vibration excited by the vibrator and a physical quantity to be measured,
A vibrator,
Any one of the drive devices described above for exciting drive vibration to the vibrator;
A detection device that detects an output signal corresponding to the physical quantity based on the detection signal,
The detection device is
The present invention relates to a physical quantity measuring device including a synchronous detector that synchronously detects the detection signal based on the output of the comparator.

  According to the present invention, it is possible to perform switching control of the switch element by diverting a signal detection result from a vibrator generally used for performing oscillation control of the oscillation loop, so that the circuit scale is not increased. In addition, it is possible to provide a physical quantity measuring device that realizes synchronous detection processing and high-speed oscillation start-up, and achieves downsizing and low power consumption. Furthermore, according to the present invention, it is possible to provide a physical quantity measuring device including a drive device that can shorten the oscillation start time without increasing the circuit scale, both when returning from the so-called sleep mode and when starting the oscillation.

In the physical quantity measuring device according to the present invention,
The detection device is
A phase shifter for adjusting the phase between the output of the comparator and the detection signal may be included.

  According to the present invention, the phase adjustment can be performed according to the phase change during the detection process of the minute detection signal. As a result, it is possible to achieve both the high-accuracy phase adjustment and the prevention of the circuit scale increase. it can.

The present invention also provides
The present invention relates to an electronic device including the physical quantity measuring device described above.

  According to the present invention, it is possible to contribute to downsizing and low power consumption of an electronic device that performs a given process using a measurement result of a physical quantity. Furthermore, according to the present invention, it is possible to provide an electronic device including a drive device that can shorten the oscillation start time without increasing the circuit scale, both when returning from the so-called sleep mode and when starting oscillation.

In the drive device according to the present invention,
The vibrator is a capacitively coupled vibrator,
The gain control amplifier excites the driving vibration by applying a rectangular wave driving signal to the vibrator.

  The rectangular driving method has an advantage that there is little variation in driving signals. In addition, since the voltage amplitude can be easily controlled, there is an advantage that the circuit configuration can be simplified and the circuit scale can be reduced.

  In addition, if a capacitively coupled oscillator (an oscillator with a DC blocking capacitor in the signal path in the internal equivalent circuit) is used, any potential can be used as the DC potential of the oscillation loop. There is an advantage that the degree is improved. An example of a capacitively coupled vibrator (capacitive vibrator) is a piezoelectric element.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
The embodiments described below do not unduly limit the contents of the present invention described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present invention.

1. FIG. 1 shows a block diagram of a configuration example of an oscillation drive circuit as a drive device in the present embodiment. The oscillation drive circuit as a drive device in the present embodiment measures a physical quantity using an output signal obtained by synchronously detecting a detection signal output from the vibrator based on the drive vibration excited by the vibrator and the physical quantity to be measured. Used for

  The oscillation drive circuit 10 is provided with first and second connection terminals TM1 and TM2 (electrodes, pads), and the oscillator 12 is provided between the first and second connection terminals outside the oscillation drive circuit 10. Has been inserted. An excitation unit 14 is attached to the vibrator 12, and the excitation unit 14 is connected to the oscillation drive circuit 10 to form an oscillation loop. First, oscillation starts when the gain of the driver in the oscillation drive circuit 10 is large (gain is greater than 1). At this point, the only input to the driver is noise. This noise includes a wide range of waves including the natural resonance frequency of the target drive vibration. This noise is input to the vibrator 12.

  The vibrator 12 is made of, for example, a piezoelectric single crystal as will be described later. Due to the frequency filter action of the vibrator 12, a signal containing a lot of waves of the target natural resonance frequency is output, and this signal is input to the driver. By repeating such an operation in the oscillation loop, the ratio of the signal of the target natural resonance frequency is increased, and the amplitude of the input signal to the driver is increased.

  In the steady oscillation state, the output current from the vibrator 12 is converted into a voltage value by the current-voltage converter 30 and oscillated by an AGC (Auto Gain Control) circuit (gain control circuit in a broad sense) 40 based on this voltage value. Controls the oscillation amplitude in the loop. As a result, the gain (loop gain) while the signal goes around the oscillation loop becomes 1, and in this state, the vibrator 12 stably oscillates.

  Stable oscillation of the vibrator is indispensable for measuring physical quantities. This is because if the amplitude of the drive signal oscillating in the vibrator is not constant, the value of the output signal to be output from the vibrator will not be constant, and accurate measurement cannot be performed.

  Further, in order to reduce the power consumption of the system including the vibrator and the oscillation drive circuit, it is indispensable to increase the oscillation start-up speed of the vibrator. This is because by quickly obtaining stable oscillation, oscillation can be started only when necessary, and the operation period during which power is consumed wastefully can be shortened.

  Therefore, in the present embodiment, in the oscillation drive circuit 10, the comparator 50 is used as a driver when oscillation is started, and a gain control amplifier (hereinafter referred to as GCA) 20 is used as a driver in a steady oscillation state.

  Therefore, in the present embodiment, the oscillation drive circuit 10 is provided with the comparator 50 in parallel with the GCA 20. The oscillation drive circuit 10 includes a first switch element SW1 inserted between the output of the GCA 20 and the second connection terminal TM2, and the first switch element SW1 is ON / OFF controlled by a switch control signal SWCTL. The Further, the oscillation drive circuit 10 includes a second switch element SW2 inserted between the output of the comparator 50 and the second connection terminal TM2, and the second switch element SW2 is controlled to be turned on / off by a switch control signal SWCTL #. Is done. The switch control signal SWCTL # is an inverted signal of the switch control signal SWCTL.

  The oscillation drive circuit 10 can output the output of the comparator 50 as a synchronous detection clock as a reference signal for synchronous detection.

  The sleep control signal SLEEP corresponding to the control data set in the sleep mode setting register 80 is supplied to the GCA 20 and the AGC circuit 40. When operating in the sleep mode, the operations of the GCA 20 and the AGC circuit 40 are stopped. In this embodiment, when operating in the sleep mode, the current-voltage converter 30 and the comparator 50 operate without being set to the disabled state (the enabled state is maintained).

  The AGC circuit 40 includes a full wave rectifier 42, an oscillation detector 44, and an integrator 46. The full-wave rectifier 42 converts the voltage value converted by the current-voltage converter 30 into a voltage value as a DC signal. The oscillation detector 44 detects whether or not the oscillation loop including the vibrator 12 is in an oscillation state based on the voltage value converted by the full wave rectifier 42, and generates a switch control signal SWCTL corresponding to the detection result. . For example, the oscillation detector 44 compares the voltage value converted by the full-wave rectifier 42 with a given reference voltage value, and generates the switch control signal SWCTL based on the comparison result. Further, the integrator 46 generates a control signal VCTL for performing oscillation control in the oscillation loop by the GCA 20 based on the integration result of the voltage value converted by the full wave rectifier 42. For example, the integrator 46 integrates the voltage value converted by the full-wave rectifier 42 to obtain the level of the DC component, compares the level with a given reference signal level, and controls the control signal based on the comparison result. Generate VCTL. For example, the high-potential side power supply voltage of the circuit (output circuit) in the output stage (final stage) of the GCA 20 is controlled based on the control signal VCTL.

  More specifically, the sleep control signal SLEEP is supplied to the full-wave rectifier 42, the oscillation detector 44, and the integrator 46. When the sleep mode is designated by the sleep control signal SLEEP, the operations of the full-wave rectifier 42, the oscillation detector 44, and the integrator 46 are stopped. When the normal mode is designated by the sleep control signal SLEEP, the full-wave rectifier 42, the oscillation detector 44, and the integrator 46 are operated.

  In the present embodiment, in the state in which the sleep mode setting register 80 is set to the normal mode, the first and second switch elements SW1 and SW2 are controlled to control the oscillation loop including the vibrator 12 and the GCA 20 and the vibration. The oscillation loop including the child 12 and the comparator 50 is switched. Further, in the present embodiment, in the state where the sleep mode is set by the sleep mode setting register 80, the oscillation is continued in the oscillation loop including the vibrator 12 and the comparator 50.

  At this time, the AGC circuit 40 performs switch control of the first and second switch elements SW1 and SW2 and oscillation amplitude control of the GCA 20.

  2A and 2B are timing waveform diagrams of the sleep control signal SLEEP and the switch control signals SWCTL and SWCTL #.

  FIG. 2A shows a timing waveform diagram when operating in the normal mode, and FIG. 2B shows a timing waveform diagram when operating in the sleep mode.

  In FIG. 2A, when the sleep control signal SLEEP is at L level, the oscillation drive circuit 10 operates in the normal mode. At this time, in the oscillation starting process such as immediately after the power is turned on, the oscillation detector 44 of the AGC circuit 40 detects that the voltage value obtained by converting the current signal from the vibrator 12 is lower than a given reference voltage value. The detector 44 generates an L level switch control signal SWCTL. As a result, the first switch element SW1 is set to the off state and the second switch element SW2 is set to the on state. At this time, as an operational characteristic of the comparator 50, when the level of the input signal of the comparator 50 exceeds a given threshold, the input signal is amplified with a very large gain, and the gain in the oscillation loop is made larger than 1. it can. As a result, in the oscillation starting process, in the oscillation loop including the vibrator 12 and the comparator 50, the oscillation in the oscillation loop is such that the gain in the oscillation loop is greater than 1 and the phase in the oscillation loop is 360 × n (n is an integer). Drive vibration is excited in the child 12.

  Thereafter, when the oscillation detector 44 detects that the voltage value obtained by converting the current signal from the vibrator 12 is higher than a given reference voltage value, the oscillation detector 44 generates an H level switch control signal SWCTL. Generate. As a result, the first switch element SW1 is set to the on state, and the second switch element SW2 is set to the off state. At this time, based on the control signal VCTL from the AGC circuit 40, the oscillation amplitude in the oscillation loop is controlled by the GCA 20 and the gain in the oscillation loop is controlled to be unity. As a result, the oscillation start-up process ends and the oscillation steady state is entered. In this oscillation steady state, in the oscillation loop including the oscillator 12 and the GCA 20, drive vibration is excited in the oscillator 12 so that the gain in the oscillation loop is 1 and the phase in the oscillation loop is 360 × n. .

  That is, in this embodiment, based on the detection result of the oscillation detector 44, the oscillation loop formed by the vibrator 12 and the comparator 50 can be switched to the oscillation loop formed by the vibrator 12 and the GCA 20. . More specifically, in the oscillation detector 44, the above switching control is performed on the condition that the DC voltage obtained by converting the current flowing through the vibrator 12 has reached a given threshold voltage. By doing so, the switching detection of the switch element can be performed by diverting the signal detection result from the vibrator 12 that is generally used for performing the oscillation control of the oscillation loop, so that the circuit scale is increased so much. Therefore, high-speed oscillation start can be realized.

  In FIG. 2B, when the sleep control signal SLEEP is at the H level, the oscillation drive circuit 10 operates in the sleep mode. At this time, the oscillation detector 44 generates an L-level switch control signal SWCTL regardless of whether the oscillation starting process is immediately after power-on or the like or the oscillation steady state. As a result, the first switch element SW1 is set to the off state and the second switch element SW2 is set to the on state. That is, the same state of the oscillation starting process in the normal mode shown in FIG. At this time, as described above, when the level of the input signal of the comparator 50 exceeds a given threshold, the input signal is amplified with a very large gain as the operation characteristic of the comparator 50, and the gain in the oscillation loop is set to 1. Can be larger. As a result, in the oscillation starting process, in the oscillation loop including the vibrator 12 and the comparator 50, the oscillation in the oscillation loop is such that the gain in the oscillation loop is greater than 1 and the phase in the oscillation loop is 360 × n (n is an integer). Drive vibration is excited in the child 12. In this way, in the sleep mode, the operation of the AGC circuit 40 can be stopped to reduce power consumption. In the sleep mode, since the oscillation state is continued in the oscillation loop used in the oscillation start process in the normal mode, high-speed oscillation start can be realized when the sleep mode is shifted to the normal mode. Therefore, it is possible to provide a drive device that can shorten the oscillation start-up time without increasing the circuit scale when operable in a so-called sleep mode.

  As described above, in the state where the oscillation driving circuit 10 is set in the normal mode, the gain in the oscillation loop formed by the vibrator 12 and the comparator 50 is made larger than 1 using the output of the comparator 50. The oscillation amplitude in the oscillation loop formed by the vibrator 12 and the GCA 20 is controlled to excite drive vibration in the vibrator 12. The oscillation drive circuit 10 excites drive vibration to the vibrator 12 in an oscillation loop formed by the vibrator 12 and the comparator 50 in a state where the sleep mode is set.

  Further, when the oscillation drive circuit 10 includes the AGC circuit 40 that controls the gain of the GCA 20 based on the oscillation signal in the oscillation loop, the operation of the GCA 20 and the comparator 50 is disabled in the state set in the sleep mode. The operation of the AGC circuit 40 can be set to a disabled state without being set to (in the enabled state).

  By the way, in the present embodiment, for example, in the normal oscillation state of the normal mode, the output of the comparator 50 is output as a clock for synchronous detection. In this way, when measuring the physical quantity using the output signal obtained by synchronously detecting the detection signal output from the vibrator 12 based on the drive vibration excited by the vibrator 12 and the physical quantity to be measured, the circuit scale is reduced. Synchronous detection processing and faster oscillation start-up can be realized without increasing it.

  It is preferable to increase the gain of the comparator 50 as much as possible. By doing so, the loop gain in the oscillation loop formed in the oscillation starting process can be increased, and the oscillation starting time can be shortened. In addition, the clock accuracy of the synchronous detection clock output in the steady oscillation state can be improved.

  In addition, it is preferable that the polarity (inverted and non-inverted) of the operational amplifier constituting the GCA 20 is the same as the polarity of the operational amplifier constituting the comparator 50. By doing so, even if the oscillation loop is switched by the first and second switch elements SW1 and SW2, it is not necessary to add a circuit for inverting the polarity, and an increase in circuit scale can be suppressed.

  FIG. 3 shows a circuit diagram of a configuration example of the oscillation drive circuit 10 of FIG.

  3, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The current-voltage converter 30 includes an operational amplifier OP1, a feedback capacitor C1, and a feedback resistor R1. A given reference voltage VR0 is supplied to the non-inverting input terminal (+) of the operational amplifier OP1, and the first connection terminal TM1 is electrically connected to the inverting input terminal (−).

  The full wave rectifier 42 includes operational amplifiers OP2 and OP3 and resistors R2 and R3. The operational amplifier OP2 and the resistors R2 and R3 function as an inverting circuit. The operational amplifier OP3 functions as a comparator that compares the output voltage of the current-voltage converter 30 with the reference voltage VR0. Full-wave rectifier 42 includes a switch element provided on the output side of operational amplifier OP2, and a switch element that bypasses the input and output of full-wave rectifier 42. Both switch elements are exclusively turned on and off based on the output signal of the operational amplifier OP3. When the sleep control signal SLEEP is at the H level, the operation of each operational amplifier is stopped by stopping or limiting the operation current of each operational amplifier of the operational amplifiers OP2 and OP3. On the other hand, when the sleep control signal SLEEP is at the L level, each operational amplifier is operated by generating an operating current of each operational amplifier of the operational amplifiers OP2 and OP3.

The oscillation detector 44 includes a low pass filter (hereinafter referred to as LPF) and an operational amplifier OP4. The LPF includes a resistor R4 and a capacitor C2. The resistor R4 is inserted in series between the LPF input and output. One end of the capacitor C2 is electrically connected to the output node of the LPF. A reference voltage VR1 is supplied to the other end of the capacitor C2. The cutoff frequency of this LPF is 1 / (2π × C2 × R4). The output node of the LPF is connected to the inverting input terminal of the operational amplifier OP4. A resistor R5 is inserted as a feedback resistor between the output of the operational amplifier OP4 and the non-inverting input terminal. The reference voltage VR1 is supplied to the non-inverting input terminal of the operational amplifier OP4 through the resistor R6. The output signal of the operational amplifier OP4 is output as the switch control signal SWCTL. When the sleep control signal SLEEP is at the H level, the operation of the operational amplifier OP4 is stopped by stopping or limiting the operation current of the operational amplifier OP4. When the sleep control signal SLEEP is at the L level, the operational amplifier OP4 is operated by generating an operation current of the operational amplifier OP4.

  The integrator 46 includes an operational amplifier OP5, resistors R7 and R8, and a capacitor C3. The capacitor C3 is connected as a feedback capacitor of the operational amplifier OP5. The resistor R8 is inserted as a feedback resistor for the operational amplifier OP5. The resistor R7 is inserted between the inverting input terminal of the operational amplifier OP5 and the output node of the full-wave rectifier 42. In the integrator 46, the effects of the input voltage offset and the input current offset are reduced by the resistors R7 and R8, and gain adjustment is performed. The reference voltage VR2 is supplied to the non-inverting input terminal of the operational amplifier OP5. An LPF function is provided by the capacitor C3 and the resistor R8 of the integrator 46, and the cutoff frequency is 1 / (2π × C3 × R8). The output signal of the operational amplifier OP5 is supplied to the GCA 20 as the control signal VCTL. When the sleep control signal SLEEP is at the H level, the operation of the operational amplifier OP5 is stopped by stopping or limiting the operation current of the operational amplifier OP5. When the sleep control signal SLEEP is at the L level, the operational amplifier OP5 is operated by generating an operation current of the operational amplifier OP5.

  Here, the current flowing through the vibrator 12 in the oscillation starting process is Id, and the current flowing through the vibrator 12 in the steady oscillation state is Id ′. In consideration of smoothing by the current-voltage converter 30, the reference voltage VR2 can be expressed as the following equation.

VR2 = (Id × R1 × 2 / π) + VR0 (1)
Here, R1 means the resistance value of the feedback resistor of the current-voltage converter 30. Similarly, the reference voltage VR1 can be expressed as the following equation.

VR1 = (Id ′ × R1 × 2 / π) + VR0 (2)
Since Id ′ <Id, VR2> VR1. Moreover, it is preferable to have the following relationship with respect to the reference voltage VR0.

VR0 <VR1 <VR2 (3)
When the sleep control signal SLEEP is at the H level, the operation of the GCA 20 is stopped by stopping or limiting the operation current of the GCA 20. When the sleep control signal SLEEP is at the L level, the GCA 20 is operated by generating an operating current of the GCA 20.

  4A and 4B show circuit diagrams of configuration examples of the GCA 20 in FIG.

  4A shows a configuration example when the GCA 20 is configured using a P-type differential amplifier, and FIG. 4B shows a configuration when the GCA 20 is configured using an N-type differential amplifier. An example is shown. 4A and 4B, the sleep control signal SLEEP # is an inverted signal of the sleep control signal SLEEP.

  In FIG. 4A, the current I0 generated by the current source is supplied as the operating current I0 ′ of the P-type differential amplifier by two current mirror circuits. One gate of the P-type differential transistor pair of the P-type differential amplifier is supplied with the voltage of the output node of the current-voltage converter 30 as the input signal IN. A reference voltage VR0 is supplied to the other gate of the P-type differential transistor pair of the P-type differential amplifier. The output voltage of the P-type differential amplifier is supplied to the output buffer. The output signal of the output buffer is supplied to one end of the first switch element SW1.

  Here, in the two current mirror circuits and the P-type differential amplifier, the high-potential side power supply voltage is the voltage VDD and the low-potential side power supply voltage is the voltage AGND. On the other hand, the output buffer is an inverter circuit composed of a P-type output transistor and an N-type output transistor. The voltage AGND is supplied to the source of the N-type transistor of the output buffer, and the control signal VCTL from the AGC circuit 40 is supplied to the source of the P-type transistor. Therefore, the output voltage of the output buffer can be changed by changing the control signal VCTL.

  In FIG. 4B, the current I1 generated by the current source is supplied as the operating current I1 ′ of the N-type differential amplifier by the two current mirror circuits. The voltage at the output node of the current-voltage converter 30 is supplied as an input signal IN to one gate of the N-type differential transistor pair of the N-type differential amplifier. A reference voltage VR0 is supplied to the other gate of the N-type differential transistor pair of the N-type differential amplifier. The output voltage of the N-type differential amplifier is supplied to the output buffer. The output signal of the output buffer is supplied to one end of the first switch element SW1.

  Here, in the two current mirror circuits and the N-type differential amplifier, the high potential side power supply voltage is the voltage VDD and the low potential side power supply voltage is the voltage AGND. On the other hand, the output buffer is an inverter circuit composed of a P-type output transistor and an N-type output transistor. The voltage AGND is supplied to the source of the N-type transistor of the output buffer, and the control signal VCTL from the AGC circuit 40 is supplied to the source of the P-type transistor. Therefore, the output voltage of the output buffer can be changed by changing the control signal VCTL.

  In FIGS. 4A and 4B, the substrate bias effect can be prevented by applying the control signal VCTL as the substrate potential of the P-type output transistor of the output buffer.

  4A and 4B, a current control transistor is provided in series with the current source. In FIG. 4A, the current source transistor is a P-type transistor, and the sleep control signal SLEEP is supplied to the gate of the transistor. In FIG. 4B, the current source transistor is an N-type transistor, and a sleep control signal SLEEP # is supplied to the gate of the transistor. 4A and 4B, when the sleep control signal SLEEP becomes H level, the source and drain of the current control transistor are electrically disconnected, and the current of the current source is changed to the current mirror circuit. Not supplied. Therefore, based on the sleep control signal SLEEP, the operation of the GCA 20 can be set to a disabled state (stopped).

  The oscillation drive circuit 10 is not limited to the configuration shown in FIG.

  For example, in the sleep mode, the operation of the AGC circuit 40 is set to stop (set to the disabled state), but at this time, the voltage of the node of each part of the AGC circuit 40 is indefinite. . In particular, when the potential of the control signal VCTL becomes unstable, the output signal of the GCA 20 also becomes unstable. Therefore, when shifting from the sleep mode to the normal mode, the output signal of the GCA 20 is also undefined due to the control signal VCTL having an undefined level.

  When the output signal of the GCA 20 becomes indefinite, drive vibration is excited in the vibrator 12 by the output signal. For example, when the vibrator 12 uses the piezoelectric effect, the vibrator 12 operates in proportion to the supplied electric charge. Therefore, there is a possibility that the vibrator 12 may be folded due to an output signal that cannot be controlled. Therefore, as a modification of the present embodiment, an output fixing transistor that fixes the output of the integrator 46 may be provided.

  FIG. 5 shows a circuit diagram of another configuration example of the oscillation drive circuit 10 of FIG.

  In FIG. 5, the same parts as those in FIG. The oscillation drive circuit of FIG. 5 differs from the oscillation drive circuit 10 of FIG. 3 in that an integrator 90 is provided instead of the integrator 46 of FIG.

  The integrator 90 has a configuration in which an output fixing transistor 92 is added to the integrator 46 of FIG. The output fixing transistor 92 is composed of an N-type transistor. The output node of the operational amplifier OP5 is connected to the drain of the output fixing transistor 92, and the voltage AGND is supplied to the source of the output fixing transistor 92. The sleep control signal SLEEP is supplied to the gate of the output fixing transistor 92.

  With such a configuration, when the sleep control signal SLEEP becomes H level, the output fixing transistor 92 becomes conductive, and the output node of the integrator 90 is set to the same potential as the voltage AGND. By doing this, even when the potential of the control signal VCTL is fixed and the mode is shifted from the sleep mode to the normal mode, the output signal of the GCA 20 is not in an indefinite state and the situation where the vibrator 12 is folded is surely avoided. become able to.

  In FIG. 5, the output fixing transistor is provided to fix the output of the integrator, but the configuration is not limited to that of FIG. 5.

2. FIG. 6 shows a block diagram of a configuration example of a vibration gyro sensor to which the oscillation drive circuit according to the present embodiment or a modification thereof is applied.

  In FIG. 6, the same parts as those in FIG.

  The vibration type gyro sensor (physical quantity measuring device in a broad sense) 100 includes an oscillation circuit 200 and a detection circuit (a detection device in a broad sense) 300. The oscillation circuit 200 includes the vibrator 12 and the oscillation drive circuit 10. The oscillation drive circuit 10 is for exciting the drive vibration unit 12 a of the vibrator 12.

  At the time of starting oscillation in the normal mode, the output of the comparator 50 is input to the oscillation drive circuit 10 as noise. This noise passes through the drive vibration unit 12a of the vibrator 12 and is subjected to frequency selection, and then a part of the signal that has passed through the drive vibration unit 12a is extracted and input to the full-wave rectifier 42 to be converted into amplitude. A signal having this amplitude is input to the oscillation detector 44 to generate a switch control signal SWCTL. When oscillation starts, the amplitude of the signal that has passed through the vibrator 12a and has undergone frequency selection is small, and the oscillation detector 44 outputs an L level switch control signal SWCTL.

  Immediately after starting oscillation in the normal mode, the amplitude of the signal that has passed through the vibrator 12a and has undergone frequency selection increases, and the oscillation detector 44 has the switch control signal SWCTL at H level. As a result, the oscillation loop is switched so that the amplitude of the signal that has passed through the vibrator 12a and has undergone frequency selection is controlled by the GCA 20. Thereafter, when most of the noise is cut in the drive vibration unit 12a and the output from the full-wave rectifier 42 is relatively small, the gain in the GCA 20 is increased and the loop gain becomes 1 while making a round of the oscillation loop. Like that. As time elapses, the output from the full-wave rectifier 42 increases, so the gain in the GCA 20 is decreased so that the loop gain becomes 1.

  In the sleep mode, the control is performed in the same manner as the oscillation starting process in the normal mode.

  When the oscillation state of the drive signal is stabilized, detection of signals from the drive detection units 12b and 12c of the vibrator 12 is started. That is, the detection signals (AC) from the vibrator drive detection units 12 b and 12 c are amplified using the AC amplifiers 312 A and 312 B of the AC amplifier circuit 310, and the outputs from the amplifiers 312 A and 312 B are added by the adder 314. .

  The output of the adder 314 is passed through the phase shifter 320 to obtain a phase shift signal. The phase of the phase shift signal is deviated from the phase of the synchronous detection clock that is the output of the comparator 50 of the oscillation drive circuit 10 by a predetermined angle, for example, 90 degrees. The phase shift signal and the synchronous detection clock from the oscillation drive circuit 10 are input to the synchronous detector 330, and the output signal from the vibrator 12 is detected. As a result, in the output signal after detection, the unnecessary leakage signal should be eliminated or at least reduced. In this way, by performing the phase adjustment between the synchronous detection clock and the detection signal in the detection circuit 300, the phase adjustment can be performed in accordance with the phase change during the detection process of the minute signal. This makes it possible to achieve both phase adjustment and prevention of an increase in circuit scale.

  The detected output signal is input to the low-pass filter 340, smoothed, and then input to the zero point adjuster 350. The output of the zero point adjuster 350 is taken out as an output signal corresponding to a physical quantity to be measured (for example, angular velocity).

  The vibration type gyro sensor 100 of FIG. 6 is preferably mounted on an electronic device such as a video camera, a digital camera, a car navigation system, an aircraft, or a robot.

  Note that the present invention is not limited to the vibrator 12 in the present embodiment. Examples of the material constituting the vibrator 12 include a constant elastic alloy such as Elinvar and a ferroelectric single crystal (piezoelectric single crystal). Examples of such single crystals include quartz, lithium niobate, lithium tantalate, lithium niobate-lithium tantalate solid solution, lithium borate, and langasite. The vibrator 12 is preferably hermetically sealed in the package. The atmosphere in the package is preferably dry nitrogen or vacuum.

  The physical quantity to be measured in the present invention is not limited to the angular velocity as in the present embodiment. When the vibration state of the vibrator is changed due to the influence of the physical quantity on the vibrator during driving vibration, the physical quantity that can be detected through the detection circuit from the change in the vibration state is targeted. . As such a physical quantity, in addition to the angular velocity applied to the vibrator, acceleration and angular acceleration are particularly preferable. Moreover, an inertial sensor is preferable as the detection device.

(Second Embodiment)
In the present embodiment, a rectangular wave drive, a sine wave drive, and a capacitively coupled vibrator in the drive device will be described.

  In the drive device of FIG. 1, both rectangular wave drive and sine wave drive can be employed. In addition, a capacitively coupled vibrator can be employed as the vibrator.

  FIG. 7A shows a main part of a driving device that performs rectangular wave driving. As illustrated, the vibrator 12 is driven by a rectangular wave drive signal (PL). The gain control of the oscillation loop can be easily performed by adjusting the high level voltage or the low level voltage of the drive signal (PL).

  The rectangular driving method has an advantage that there is little variation in the driving signal (PL). In addition, since the control of the voltage amplitude of the drive signal is easy, there is an advantage that the circuit configuration can be simplified and the circuit scale can be reduced.

  For example, even when the vibrator (physical quantity transducer) is driven by a rectangular wave having a predetermined frequency (including harmonic components such as third order and fifth order), the vibrator (physical quantity transducer) itself is driven by the rectangular wave. Utilizing the fact that unnecessary harmonics are reduced by the frequency filter function and a drive signal having a target frequency (resonance frequency) can be obtained.

  FIG. 7B shows a main part of a driving device that executes sinusoidal driving. As illustrated, the vibrator 12 is driven by a sinusoidal drive signal (PQ). The gain control amplifier (GCA) 20 adjusts the gain of the oscillation loop by variably controlling the resistance value of the variable resistor 100. Such an analog waveform driving method can also be used.

  7A and 7B, a capacitive coupling type oscillator is used as the oscillator 14 (however, the present invention is not limited to this, and various types such as a variable resistance type) can be used. A vibrator can be used).

  A capacitively coupled oscillator (capacitive oscillator) is a type of oscillator in which a DC blocking capacitor (C1 and C2 in FIGS. 7A and 7B) is interposed in a signal path in an internal equivalent circuit. It is. An example of a capacitively coupled vibrator (capacitive vibrator) is a piezoelectric element.

  When a capacitively coupled oscillator is used, an arbitrary potential can be used as the DC potential of the oscillation loop. Therefore, the circuit can be configured without worrying about the DC potential, and there is an advantage that the degree of freedom in circuit configuration is improved.

  According to the present invention, it is possible to provide a drive device capable of shortening the oscillation start time without increasing the circuit scale, both when returning from the so-called sleep mode and when starting the oscillation, and a physical quantity measuring device and an electronic apparatus using the drive device. be able to.

The circuit block diagram of the structural example of the oscillation drive circuit in this embodiment. 2A and 2B are timing diagrams illustrating an example of the sleep control signal and the switch control signal in FIG. FIG. 2 is a diagram showing a circuit example of the oscillation drive circuit of FIG. 1. 4A and 4B are circuit diagrams of configuration examples of the GCA. FIG. 3 is a circuit diagram of another configuration example of the oscillation drive circuit of FIG. 1. The block diagram of the structural example of the vibration type gyro sensor in this embodiment. 7A and 7B are circuit diagrams for explaining a rectangular wave drive, a sine wave drive, and a capacitively coupled vibrator.

Explanation of symbols

10 oscillation drive circuit, 12 transducers, 12a drive oscillation unit,
12b, 12c drive detection unit, 14 excitation means, 20 GCA,
30 current-voltage converter, 40 AGC circuit, 42 full-wave rectifier,
44 oscillation detector, 46 integrator, 50 comparator,
80 sleep mode setting register, 100 vibration type gyro sensor,
200 oscillation circuit, 300 detection circuit, 310 AC amplification circuit,
312A, 312B AC amplifier, 314 adder, 320 phase shifter,
330 Synchronous detector, 340 LPF, 350 0-point adjuster,
SW1 to SW2 First to second switch elements, SLEEP sleep control signal,
SWCTL, SWCTL # Switch control signal, VCTL control signal

Claims (10)

When measuring a physical quantity using an output signal obtained by synchronously detecting a detection signal output from the vibrator based on a drive vibration excited by the vibrator and a physical quantity to be measured, an oscillation loop is formed with the vibrator. A drive device for exciting drive vibration to the vibrator,
A gain control amplifier that controls the oscillation amplitude in the oscillation loop to excite drive vibration in the vibrator;
A comparator that generates a reference signal for the synchronous detection based on a signal in the oscillation loop;
In the state set to the first operation mode, the output of the comparator is used to increase the gain in the oscillation loop formed by the vibrator and the comparator to greater than 1, and then the vibrator and the gain control Control the oscillation amplitude in the oscillation loop formed by the amplifier to excite the drive vibration in the vibrator,
In the state set in the second operation mode, a driving device excites driving vibration in the vibrator in an oscillation loop formed by the vibrator and the comparator. In claim 1,
Including an oscillation detector for detecting a signal from the vibrator;
In the state set in the first operation mode, formed by the vibrator and the gain control amplifier from the oscillation loop formed by the vibrator and the comparator based on the detection result of the oscillation detector. A drive device characterized by switching to an oscillation loop. In claim 2,
The oscillation detector is
From the oscillation loop formed by the vibrator and the comparator, by the vibrator and the gain control amplifier, on the condition that the direct current voltage converted from the current flowing through the vibrator has reached a given threshold voltage. A drive device characterized by switching to an oscillation loop to be formed. In claim 1,
A gain control circuit for controlling the gain of the gain control amplifier based on an oscillation signal in the oscillation loop;
In the state set in the second operation mode, the operation of the gain control circuit is set to a disabled state without setting the operations of the gain control amplifier and the comparator to a disabled state. Drive device. In any one of Claims 1 thru | or 4,
When an oscillation loop is formed by the vibrator and the comparator, the vibrator is excited using the output of the comparator,
When the oscillation loop is formed by the vibrator and the gain control amplifier, the output of the comparator is used as a clock for synchronous detection for generating the output signal. In any one of Claims 1 thru | or 5,
The drive device characterized in that the polarity of the output of the gain control amplifier is the same as the polarity of the output of the comparator. A physical quantity measuring device for measuring a physical quantity corresponding to a detection signal output from the vibrator based on a drive vibration excited by the vibrator and a physical quantity to be measured,
A vibrator,
The drive device according to any one of claims 1 to 6, wherein drive vibration is excited in the vibrator;
A detection device that detects an output signal corresponding to the physical quantity based on the detection signal,
The detection device is
A physical quantity measuring apparatus comprising a synchronous detector for synchronously detecting the detection signal based on an output of the comparator. In claim 7,
The detection device is
A physical quantity measuring apparatus comprising a phase shifter for adjusting a phase between the output of the comparator and the detection signal.   An electronic apparatus comprising the physical quantity measuring device according to claim 7 or 8. In claim 1,
The vibrator is a capacitively coupled vibrator,
The gain control amplifier excites the driving vibration by applying a rectangular wave driving signal to the vibrator.

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