JP2018044823A - Drive circuit and physical quantity sensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive circuit and a physical quantity sensor with which it is possible to shorten the startup time of a vibrator while suppressing an increase in power consumption.SOLUTION: A drive circuit comprises: an amplification circuit for amplifying an input signal and outputting it as a drive signal to drive a vibrator; a vibration detection unit for detecting the vibrating state of the vibrator on the basis of the drive signal that corresponds to the output signal outputted by the vibrator, and determining, on the basis of the detected vibrating state of the vibrator, a first gain value by which the input signal is multiplied by the amplification circuit and outputting the determined gain value; a vibration determination unit for determining the vibrating state of the vibrator on the basis of a second gain value with which it is possible to determine that the vibrator is vibrating in an appropriate vibrating state and the first gain value; an additional amplification circuit for outputting an amplified signal that is amplified by multiplying a vibration signal by a predetermined gain value; and a switching circuit for switching the input signal amplified by the amplification circuit to either the vibration signal or the amplified signal on the basis of a determination result of the vibration detection unit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a drive circuit and a physical quantity sensor device.

  Conventionally, a physical quantity sensor device that detects a physical quantity by vibrating a vibrator provided as a vibration sensor has been put into practical use. In the physical quantity sensor device, the physical quantity is measured by detecting a change amount in which the vibration (frequency, etc.) of the vibrator is changed by a physical quantity given from the outside. For example, in a vibration type pressure sensor device, pressure is measured by detecting a change amount (for example, a vibration frequency or a vibration frequency) when vibration of a vibrator is changed by pressure applied from the outside. In such a physical quantity sensor device, a self-excited vibration control circuit for vibrating the vibrator with an appropriate constant amplitude is provided as a vibrator drive circuit in order to accurately detect a change in vibration in the vibrator ( (See Patent Document 1, Patent Document 2, and Patent Document 3).

JP 2003-021518 A International Publication No. 2010/084531 JP 2010-151669 A

  By the way, in order to realize low power consumption of the physical quantity sensor device, there is a method of intermittently operating the vibrator. In this intermittent operation, the vibration operation is stopped and operated repeatedly in a predetermined cycle. At this time, it takes a certain amount of time for the vibrator to change from a state where it does not vibrate to a state where it vibrates. In the physical quantity sensor device, the time until the vibrator vibrates to an appropriate amplitude from the state in which the vibrator does not vibrate, the so-called startup time, is a time when a change in physical quantity cannot be accurately detected. Short is desirable.

  Here, as a method of shortening the activation time of the vibrator in the physical quantity sensor device, it is conceivable to increase the gain of the drive signal of the vibrator output from the drive circuit. However, increasing the gain of the drive signal corresponds to increasing the power consumption. That is, although the vibrator is intermittently operated in order to realize low power consumption in the physical quantity sensor device, the power consumption increases because the vibrator is activated quickly.

  The present invention has been made based on the above problems, and an object of the present invention is to provide a drive circuit and a physical quantity sensor device that can reduce the startup time of a vibrator while suppressing an increase in power consumption. .

  In order to solve the above problems, the drive circuit of the present invention is a drive circuit that vibrates a vibrator used for measuring a physical quantity, and amplifies an input signal and outputs the amplified signal as a drive signal for driving the vibrator. An oscillation circuit detects a vibration state of the vibrator based on a vibration signal corresponding to an output signal output from the vibrator, and converts the input signal in the amplification circuit based on the detected vibration state of the vibrator. A vibration detection unit that determines and outputs a first gain value to be multiplied, a second gain value that can determine that the vibrator vibrates in an appropriate vibration state, and the first gain value Based on the vibration determination unit for determining the vibration state of the vibrator, an additional amplification circuit for outputting an amplified signal obtained by multiplying the vibration signal by a predetermined gain value, and the determination result of the vibration determination unit On the basis of, It said input signal whose serial amplifier circuit for amplifying, and a switching circuit for switching to one of the vibration signal or the amplified signal, it is characterized.

  The vibration determination unit in the drive circuit of the present invention determines that the vibrator is not vibrating in an appropriate vibration state when the first gain value is larger than the second gain value. When the first gain value is less than or equal to the second gain value, it is determined that the vibrator is oscillating in an appropriate vibration state, and the switching circuit determines that the vibrator is When it is determined that it is not vibrating in an appropriate vibration state, the amplified signal is used as the input signal, and when the vibration determination unit determines that the vibrator is vibrating in an appropriate vibration state, The vibration signal is used as the input signal.

  The vibration determination unit in the drive circuit of the present invention includes a reference circuit that outputs the second gain value, the second gain value, and the first gain that is currently output by the vibration detection unit. And a comparator that compares the result and outputs the result of the comparison as a result of the determination of the vibration state of the vibrator.

  In addition, the second gain value in the drive circuit of the present invention is the first gain that can be determined that the vibration of the vibrator is a steady-state vibration that can be used to measure the physical quantity. The gain value is the upper limit of the value range.

  Further, the vibration determination unit in the drive circuit of the present invention determines the vibration state of the vibrator at the start time of the vibrator that causes the vibrator to change from an unvibrated state to an appropriate vibration state, and performs the switching. The circuit switches the input signal amplified by the amplifier circuit based on a determination result of the vibration determination unit during the startup time.

  The physical quantity sensor device of the present invention includes the drive circuit of the present invention, and a physical quantity measurement circuit that detects a change in vibration in the vibrator and measures a physical quantity based on the detected change in vibration. It is characterized by.

  According to the present invention, it is possible to provide a drive circuit and a physical quantity sensor device that can shorten the activation time of the vibrator while suppressing an increase in power consumption.

It is a block diagram showing a schematic structure of a drive circuit in an embodiment of the present invention. It is the timing chart which showed an example of the signal when starting the drive of a vibration sensor in the drive circuit of this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a drive circuit according to an embodiment of the present invention. In FIG. 1, in a physical quantity sensor device 1 equipped with a drive circuit according to an embodiment of the present invention, a vibration sensor 10 which is a vibrator used for detection of a physical quantity given from the outside, and the vibration sensor 10 are driven (vibration). The configuration with the drive circuit 20 is shown. That is, in the configuration of the physical quantity sensor device 1 illustrated in FIG. 1, the configuration of the physical quantity measurement circuit that detects a change in vibration of the vibration sensor 10 and measures the physical quantity based on the detected change in vibration is omitted.

  In addition, the drive circuit 20 is a measurement called a field device for the purpose of monitoring the operating state of each facility arranged in the plant and controlling the operation of the facility in a plant having various facilities. You may mount in field devices (for example, a two-wire pressure transmitter, a wireless pressure transmitter, etc.), such as a device and an operation device. Further, the drive circuit 20 is a vibration type sensor device that vibrates the vibration sensor 10 provided as a vibrator and detects a physical quantity given from the outside, such as a pressure sensor device, a gyro sensor device, and an acceleration sensor device. May be installed. However, the sensor device on which the drive circuit 20 can be mounted is not limited to the sensor device as described above, and the physical quantity given from the outside is changed by changing the vibration of the vibrator by vibrating the vibrator. As long as it is a vibration type sensor device that detects based on the above, it may be mounted on a sensor device that measures any physical quantity.

  The vibration sensor 10 is a vibration sensor configured to include a vibrator (for example, a crystal vibrator) that vibrates in accordance with a sensor drive signal output from the drive circuit 20. The vibration sensor 10 is a vibration sensor that uses, for example, a MEMS (Micro Electro Mechanical Systems) as a vibrator. The vibration sensor 10 outputs a signal corresponding to the vibration of the vibrator (hereinafter referred to as “sensor output signal”). In the following description, for ease of explanation, the sensor output signal output by the vibrator constituting the vibration sensor 10 is assumed to be output by the vibration sensor 10.

  The drive circuit 20 is a self-excited vibration control circuit for driving the vibrator constituting the vibration sensor 10 to vibrate the vibrator with an appropriate constant amplitude. The drive circuit 20 controls (drives) the vibration of the vibrator constituting the vibration sensor 10 so as to intermittently operate, thereby reducing power consumption in the physical quantity sensor device 1 including the drive circuit 20. For example, in the physical quantity sensor device 1 provided with the drive circuit 20, by performing an intermittent operation that repeatedly activates the vibration sensor 10, measures a physical quantity by a physical quantity measurement circuit (not shown), and stops the vibration sensor 10 in one second. The power consumed while the vibration sensor 10 vibrates is reduced. At this time, in the physical quantity sensor device 1, the physical quantity measurement circuit (not shown) cannot accurately detect the physical quantity during the start-up time when the vibration sensor 10 is vibrated to an appropriate amplitude from the non-vibrating state. Despite time, it is time to consume power. For this reason, the drive circuit 20 shortens the time for consuming power by shortening the start-up time for changing the vibration sensor 10 from being not oscillated to being oscillated to an appropriate amplitude, that is, low power consumption. Plan The drive circuit 20 includes a sensor amplifier 21, a variable gain amplifier 22, an amplitude detection circuit 23, an error amplifier 24, an amplitude reference circuit 25, a boost amplifier 26, a switch 27, a comparator 28, and a boost reference circuit 29. And comprising.

  The sensor amplifier 21 is an amplifier that amplifies the signal level by multiplying the sensor output signal output from the vibration sensor 10 by a predetermined gain value. The sensor amplifier 21 outputs a sensor output signal obtained by amplifying the signal level to each of the amplitude detection circuit 23, the boost amplifier 26, and the switch 27 as a sensor signal.

  The amplitude detection circuit 23 is a detection circuit that detects information on the amplitude of vibration of the vibration sensor 10 based on the sensor signal output from the sensor amplifier 21. More specifically, the amplitude detection circuit 23 detects the magnitude of the amplitude at which the vibrator constituting the vibration sensor 10 vibrates based on the sensor signal. The vibration state of the vibrator constituting the vibration sensor 10 can be monitored based on the amplitude detected by the amplitude detection circuit 23. The amplitude detection circuit 23 outputs information indicating the magnitude of the detected amplitude (hereinafter referred to as “amplitude information”) to the error amplifier 24.

  The amplitude reference circuit 25 generates a reference (hereinafter referred to as “reference amplitude information”) that represents the magnitude of the amplitude that serves as a reference for the drive circuit 20 to keep the vibration of the vibration sensor 10 in an appropriate constant vibration state. Circuit. Here, the reference amplitude information generated by the amplitude reference circuit 25 is for enabling a physical quantity measurement circuit (not shown) to accurately detect a change in physical quantity during a period in which a change in vibration of the vibration sensor 10 is detected. Is information representing the amplitude of the target steady state amplitude. The amplitude reference circuit 25 outputs the generated reference amplitude information to the error amplifier 24.

  The error amplifier 24 is a control circuit that controls the gain value set in the variable gain amplifier 22. The error amplifier 24 includes the amplitude information output from the amplitude detection circuit 23, that is, the current amplitude of the vibration sensor 10 oscillating, and the reference amplitude information output from the amplitude reference circuit 25, that is, the drive circuit 20. Compares the amplitude of the target for vibrating the vibration sensor 10. Then, the error amplifier 24 determines a gain value to be set in the variable gain amplifier 22 based on the comparison result between the amplitude information and the reference amplitude information. The error amplifier 24 outputs control information (hereinafter referred to as “gain control signal”) representing the determined gain value to each of the variable gain amplifier 22 and the comparator 28.

  More specifically, the error amplifier 24 first calculates the difference between the magnitude of the amplitude represented by the amplitude information and the magnitude of the amplitude represented by the reference amplitude information. Subsequently, in the error amplifier 24, the magnitude of the amplitude represented by the amplitude information becomes the magnitude of the amplitude represented by the reference amplitude information, that is, the magnitude of the amplitude represented by the amplitude information and the magnitude of the amplitude represented by the reference amplitude information. A gain value is calculated so as to reduce the difference. Thereafter, the error amplifier 24 determines a gain value to be set in the variable gain amplifier 22 in order to change the amplitude of the vibration sensor 10 vibrating based on the calculated gain value. The error amplifier 24 outputs a gain control signal representing the determined gain value to each of the variable gain amplifier 22 and the comparator 28. The gain control signal may be the calculated gain value itself. In the following description, for ease of explanation, it is assumed that the gain control signal is the calculated gain value itself.

  The configuration combining the configuration so far and the variable gain amplifier 22 is also a configuration provided in a drive circuit (self-excited control circuit) provided in a conventional physical quantity sensor device. In the conventional drive circuit, the variable gain amplifier 22 drives the vibration sensor 10 with a sensor drive signal obtained by amplifying the sensor signal output from the sensor amplifier 21 in accordance with the gain control signal output from the error amplifier 24. By the way, when the vibration sensor 10 is intermittently operated in order to reduce the power consumption of the physical quantity sensor device, the startup time for changing the vibration sensor 10 from a non-vibrating state to an appropriate amplitude is set. In order to shorten the position, it is necessary to drive the vibration sensor 10 with a sensor drive signal obtained by further amplifying the sensor signal output from the sensor amplifier 21. However, if the variable gain amplifier 22 that outputs the sensor driving signal amplifies the sensor signal output from the sensor amplifier 21 more greatly, the variable gain amplifier 22 consumes more power. That is, in the configuration of the conventional physical quantity sensor device, when the vibration sensor 10 achieves low power consumption by intermittent operation, the amplification factor (that is, variable gain) of the variable gain amplifier 22 depends on factors such as power consumption and frequency response characteristics. The gain of the amplifier 22 is limited, and there is a limit to the startup time of the vibration sensor 10 that can be shortened. Therefore, in the drive circuit 20, the conventional physical quantity sensor device has the configuration described below without increasing the gain (gain) of the variable gain amplifier 22, that is, without increasing the power consumption of the variable gain amplifier 22. The start-up time is shorter than the drive circuit provided in

  The boost reference circuit 29 is a reference circuit that generates a gain value (hereinafter, referred to as a “boost reference gain value”) that can be determined that the vibration sensor 10 vibrates to an appropriate amplitude. Here, the boost reference gain value generated by the boost reference circuit 29 is such that the drive circuit 20 does not vibrate when the drive circuit 20 is powered on or when the vibration sensor 10 is intermittently operated. This is a gain value with which it can be determined that the vibration sensor 10 is oscillating to an appropriate amplitude when the startup time for oscillating to an appropriate amplitude is shortened. For example, the boost reference gain value generated by the boost reference circuit 29 is an upper limit gain value that can determine that the vibration of the vibration sensor 10 is in a steady state. The boost reference circuit 29 outputs the generated boost reference gain value to the comparator 28.

  The comparator 28 is a comparator that compares the gain value represented by the gain control signal output from the error amplifier 24 with the boost reference gain value output from the boost reference circuit 29. That is, the comparator 28 compares the gain value set by the error amplifier 24 in the variable gain amplifier 22 with the upper limit gain value that can determine that the vibration of the vibration sensor 10 is in a steady state. Accordingly, the comparator 28 can determine whether or not the variable gain amplifier 22 is driving the vibration sensor 10 with a gain value that increases the amplitude of vibration. Then, the comparator 28 outputs control information representing the result of comparing the respective gain values to each of the boost amplifier 26 and the switch 27. Here, as a result of comparing the respective gain values by the comparator 28, as described above, it is determined whether or not the variable gain amplifier 22 is driving the vibration sensor 10 with a gain value that increases the vibration amplitude. It is a result. Here, the result determined by the comparator 28 is used as a control signal for switching whether or not to accelerate the vibration of the vibration sensor 10 (hereinafter referred to as “boost control signal”).

  The boost amplifier 26 is an amplifier that amplifies the signal level by multiplying the sensor signal output from the sensor amplifier 21 by a predetermined gain value (for example, a gain value that triples the sensor signal). The boost amplifier 26 outputs a sensor signal obtained by amplifying the signal level (hereinafter referred to as “boost sensor signal”) to the switch 27. The boost amplifier 26 outputs a boost sensor signal when the boost control signal output from the comparator 28 indicates that the vibration of the vibration sensor 10 is accelerated, and the boost control signal output from the comparator 28. However, when it represents that the vibration of the vibration sensor 10 is not accelerated, the boost sensor signal may not be output.

  The switch 27 is a selection circuit that selects either the sensor signal output from the sensor amplifier 21 or the boost sensor signal output from the boost amplifier 26 according to the boost control signal output from the comparator 28. The switch 27 outputs one of the selected sensor signals as an input signal of the variable gain amplifier 22. More specifically, the switch 27 selects and changes the sensor signal output from the sensor amplifier 21 when the boost control signal output from the comparator 28 indicates that the vibration of the vibration sensor 10 is not accelerated. Output to the gain amplifier 22. This state is the same as the operation state in the drive circuit provided in the conventional physical quantity sensor device. On the other hand, when the boost control signal output from the comparator 28 indicates that the vibration of the vibration sensor 10 is accelerated, the switch 27 selects the boost sensor signal output from the boost amplifier 26 and selects the variable gain amplifier 22. Output to.

  The variable gain amplifier 22 is an amplifier that amplifies the signal level by multiplying the sensor signal output from the switch 27 by the gain value represented by the gain control signal output from the error amplifier 24. The variable gain amplifier 22 outputs a sensor signal obtained by amplifying the signal level to the vibration sensor 10 as a sensor drive signal. As a result, the vibrator constituting the vibration sensor 10 vibrates with a constant amplitude according to the sensor drive signal output from the variable gain amplifier 22. That is, the vibrator constituting the vibration sensor 10 has an appropriate constant vibration that allows a physical quantity measurement circuit (not shown) to accurately detect a change in physical quantity during a period in which the vibration change of the vibration sensor 10 is detected. The state (steady state) is maintained.

  Here, the amplification factor (gain) at which the variable gain amplifier 22 amplifies the sensor signal output from the switch 27 is the same as the variable gain amplifier 22 provided in the drive circuit (self-excited control circuit) provided in the conventional physical quantity sensor device. Similarly, it is an amplification factor (gain) corresponding to the gain control signal output from the error amplifier 24. That is, the variable gain amplifier 22 amplifies the sensor signal output from the switch 27 without consuming more power. However, in the drive circuit 20, when the boost control signal output from the comparator 28 indicates that the vibration of the vibration sensor 10 is accelerated, the variable gain amplifier 22 receives the boost sensor signal output from the boost amplifier 26. Amplify. This boost sensor signal is a sensor signal obtained by further amplifying the sensor signal output from the sensor amplifier 21 by the boost amplifier 26 as in the conventional drive circuit. In other words, in the drive circuit 20, the amplification factor (gain) of the variable gain amplifier 22 is the same as that of the variable gain amplifier 22 provided in the drive circuit provided in the conventional physical quantity sensor device, but the sensor signal to be amplified is conventional. Is a more amplified sensor signal. Thereby, in the drive circuit 20, the sensor signal output from the sensor amplifier 21 is more increased without increasing the gain (gain) of the variable gain amplifier 22, that is, without increasing the power consumption of the variable gain amplifier 22. It can be greatly amplified.

  With such a configuration, in the physical quantity sensor device 1 including the drive circuit 20, when the vibration sensor 10 is intermittently operated in order to achieve low power consumption, the vibration sensor 10 is suppressed while suppressing an increase in power consumption. It is possible to shorten the start-up time for changing from a state of not vibrating to a state of vibrating to an appropriate amplitude.

  Next, an example of the operation of the drive circuit 20 will be described. FIG. 2 is a timing chart showing an example of signals when driving of the vibration sensor 10 is started in the drive circuit of the present embodiment. FIG. 2 shows an example of signal changes when the drive circuit 20 accelerates vibration of the vibration sensor 10 and when it does not accelerate, that is, when the drive circuit 20 corresponds to the operation of the conventional drive circuit. 2 shows an example of a change in the gain control signal output from the error amplifier 24, and the lower stage in FIG. 2 shows an example of a change in the boost control signal output from the comparator 28. In the upper part of FIG. 2, the timing of the gain control signal indicated by the broken line is the timing when the drive circuit 20 operates so as not to accelerate the vibration of the vibration sensor 10, that is, when the operation corresponds to the operation of the conventional drive circuit. The timing is shown. In the upper part of FIG. 2, the timing of the gain control signal indicated by the solid line indicates the timing when the drive circuit 20 operates to accelerate the vibration of the vibration sensor 10. The lower part of FIG. 2 shows only the timing of the boost control signal when the drive circuit 20 is operated so as to accelerate the vibration of the vibration sensor 10. This is because when the drive circuit 20 performs an operation corresponding to the operation of the conventional drive circuit, the operation according to the boost control signal output from the comparator 28 is not performed.

  When the vibration sensor 10 is not vibrating, the sensor amplifier 21 outputs a sensor signal in a state where the vibration is stopped to each of the amplitude detection circuit 23, the boost amplifier 26, and the switch 27. As a result, the amplitude detection circuit 23 outputs amplitude information indicating that the vibration sensor 10 is not properly vibrating to the error amplifier 24.

  Here, first, the timing when the drive circuit 20 performs an operation corresponding to the operation of the conventional drive circuit, indicated by a broken line, in the upper part of FIG. 2 will be described. In this case, the switch 27 selects the sensor signal output from the sensor amplifier 21 and outputs it to the variable gain amplifier 22.

  When the drive circuit 20 starts to vibrate the vibration sensor 10 at time ts, the error amplifier 24 is based on the amplitude information output from the amplitude detection circuit 23 and the reference amplitude information output from the amplitude reference circuit 25. Thus, a gain control signal representing a gain value set in the variable gain amplifier 22 is output to each of the variable gain amplifier 22 and the comparator 28. More specifically, before the time ts, the amplitude information output from the amplitude detection circuit 23 is information indicating that the vibration sensor 10 is not properly vibrating, for example, the amplitude magnitude = 0. Therefore, the error amplifier 24 sends a gain control signal having a limit gain value that can be set to the variable gain amplifier 22 (voltage = V3 in the upper part of FIG. 2) from the time ts to the variable gain amplifier 22 and the comparator 28. Output to each of.

  Thus, the variable gain amplifier 22 has a signal level obtained by multiplying the sensor signal input from the sensor 27 and output from the sensor amplifier 21 by the gain value represented by the gain control signal output from the error amplifier 24. A sensor drive signal is output to the vibration sensor 10.

  Here, the gain value = G1 is obtained by multiplying the sensor output signal output from the vibration sensor 10 by the sensor amplifier 21 and the gain value by which the variable gain amplifier 22 is multiplied by the sensor signal output from the switch 27, that is, Consider a case where the gain value represented by the gain control signal output from the error amplifier 24 is gain value = G2. At this time, the signal level of the sensor drive signal is expressed by the following equation (1).

  Signal level of sensor drive signal = G1 × G2 × signal level of sensor signal (1)

  The vibration sensor 10 is driven to vibrate by the sensor drive signal having the signal level of the above formula (1), and the amplitude gradually increases. At this time, the sensor amplifier 21 outputs a sensor signal corresponding to the sensor output signal output from the vibration sensor 10, and the amplitude detection circuit 23 causes the vibration sensor 10 to vibrate based on the sensor signal output from the sensor amplifier 21. The detected amplitude information is detected, and amplitude information representing the detected amplitude is output to the error amplifier 24.

  Thereafter, gradually from time t1, the difference between the magnitude of the amplitude represented by the amplitude information output from the amplitude detection circuit 23 and the magnitude of the amplitude represented by the reference amplitude information output from the amplitude reference circuit 25 decreases, and is determined in advance. When the difference falls within the range, the error amplifier 24 outputs a gain control signal representing a gain value for maintaining the vibration of the vibration sensor 10 in a steady state to each of the variable gain amplifier 22 and the comparator 28. In the upper part of FIG. 2, when the voltage range representing the gain value in which the vibration of the vibration sensor 10 is in a steady state is set to voltage = V1 to voltage = V2, the voltage of the gain control signal output by the error amplifier 24 is In this example, the voltage gradually decreases from time t1 and stabilizes at a voltage between voltage = V1 and voltage = V2.

  Thus, the variable gain amplifier 22 has a signal level obtained by multiplying the sensor signal input from the sensor 27 and output from the sensor amplifier 21 by the gain value represented by the gain control signal output from the error amplifier 24. A sensor drive signal is output to the vibration sensor 10 to keep the vibration of the vibration sensor 10 in a steady state. Thereby, the physical quantity measuring circuit (not shown) can accurately detect the change in the physical quantity in the period for detecting the change in the vibration of the vibration sensor 10 after the vibration of the vibration sensor 10 is maintained in the steady state.

  As described above, when the drive circuit 20 performs an operation corresponding to the operation of the conventional drive circuit, the voltage of the gain control signal becomes low from time t1, and the vibration of the vibration sensor 10 becomes a steady state. That is, in a period after time t1, a physical quantity measurement circuit (not shown) can accurately detect a change in physical quantity.

  Next, the timing when the drive circuit 20 operates so as to accelerate the vibration of the vibration sensor 10 indicated by a solid line in the upper part of FIG. 2 will be described. In this case, the switch 27 selects the boost sensor signal output from the boost amplifier 26 and outputs it to the variable gain amplifier 22.

  When the drive circuit 20 starts to vibrate the vibration sensor 10 at time ts, the error amplifier 24 operates in the same manner as the timing when the drive circuit 20 performs an operation corresponding to the operation of the conventional drive circuit.

  As a result, the variable gain amplifier 22 multiplies the boost sensor signal input from the switch 27 and output from the boost amplifier 26 by the gain level represented by the gain control signal output from the error amplifier 24. Is output to the vibration sensor 10.

  Here, consider a case where a predetermined gain value multiplied by the sensor signal output from the sensor amplifier 21 by the boost amplifier 26 is gain value = G3. At this time, the signal level of the sensor drive signal is expressed by the following equation (2).

Signal level of sensor driving signal = G1 × G2 × G3 × signal level of sensor signal
... (2)

  In the above formula (2), G1 and G2 are the same as in the above formula (1).

  The vibration sensor 10 is driven and vibrated by the sensor drive signal having the signal level of the above equation (2), and the amplitude gradually increases. At this time, the sensor amplifier 21 outputs a sensor signal corresponding to the sensor output signal output from the vibration sensor 10, similarly to the timing when the drive circuit 20 performs an operation corresponding to the operation of the conventional drive circuit. The amplitude detection circuit 23 detects information on the amplitude at which the vibration sensor 10 vibrates based on the sensor signal output from the sensor amplifier 21, and outputs amplitude information indicating the detected amplitude to the error amplifier 24. To do.

  Here, as can be seen by comparing the above formula (1) and the above formula (2), when the drive circuit 20 operates to accelerate the vibration of the vibration sensor 10, the drive circuit 20 is a conventional drive circuit. The signal level of the sensor drive signal is gain value = G3 times as compared with the case where the operation corresponding to the above operation is performed. That is, as described above, the sensor drive signal is a signal further amplified by the gain value amplified by the boost amplifier 26 than when the drive circuit 20 operates corresponding to the operation of the conventional drive circuit. For this reason, the vibration sensor 10 has a steady-state vibration, that is, a magnitude of the steady-state amplitude faster than when the drive circuit 20 performs an operation corresponding to the operation of the conventional drive circuit.

  Thereby, for example, as shown in the upper part of FIG. 2, the magnitude of the amplitude represented by the amplitude information output from the amplitude detection circuit 23 and the reference amplitude information output from the amplitude reference circuit 25 are gradually increased from time t2. The difference from the magnitude of the expressed amplitude is reduced, and the difference is within a predetermined range. That is, as shown in the upper part of FIG. 2, when the drive circuit 20 operates to accelerate the vibration of the vibration sensor 10, the drive circuit 20 operates corresponding to the operation of the conventional drive circuit. From time t2 earlier than time t1 at which the difference between the magnitude of the amplitude represented by the amplitude information and the magnitude of the amplitude represented by the reference amplitude information starts to decrease, the magnitude of the amplitude represented by the amplitude information and the magnitude of the amplitude represented by the reference amplitude information The difference between and begins to decrease. Thus, when the drive circuit 20 operates to accelerate the vibration of the vibration sensor 10, the error amplifier 24 drives a gain control signal representing a gain value for keeping the vibration of the vibration sensor 10 in a steady state. The output is output to each of the variable gain amplifier 22 and the comparator 28 from an earlier timing than when the circuit 20 performs an operation corresponding to the operation of the conventional drive circuit (for example, timing earlier by time t1−time t2). The voltage of the gain control signal output from the error amplifier 24 when the vibration of the vibration sensor 10 represents a steady state gain value is the same as when the drive circuit 20 operates corresponding to the operation of the conventional drive circuit. In addition, the voltage is between V = V1 and V = V2.

  The comparator 28 outputs the boost control signal and the vibration of the vibration sensor 10 when the gain control signal currently output from the error amplifier 24 falls within the voltage range indicating that the vibration of the vibration sensor 10 is in a steady state. The state representing acceleration is changed to a state representing that the vibration of the vibration sensor 10 is not accelerated. In the lower part of FIG. 2, when the voltage of the gain control signal is at the time t3 when the upper limit voltage of the range in which it is possible to determine that the vibration of the vibration sensor 10 is in a steady state is equal to or lower than V2, the boost control signal Changes from a state representing acceleration of the vibration of the vibration sensor 10 (“High” level = boost ON) to a state representing that the vibration of the vibration sensor 10 is not accelerated (Low “level = boost OFF). Shows the case.

  As a result, the switch 27 switches the sensor signal output to the variable gain amplifier 22. More specifically, the sensor signal output to the variable gain amplifier 22 is switched from the boost sensor signal output from the boost amplifier 26 to the sensor signal output from the sensor amplifier 21. As a result, the drive circuit 20 receives the gain control signal output from the error amplifier 24 in response to the sensor signal output from the sensor amplifier 21 input by the variable gain amplifier 22 via the switch 27 after time t3. A sensor drive signal having a signal level multiplied by the expressed gain value is output to the vibration sensor 10 to keep the vibration of the vibration sensor 10 in a steady state. As a result, the physical quantity measurement circuit (not shown) maintains the vibration of the vibration sensor 10 in a steady state after time t2 (or after time t3), which is earlier than the conventional operation, and then the vibration of the vibration sensor 10 is reduced. It is possible to accurately detect the change in the physical quantity during the period for detecting the change.

  In addition, after the switch 27 switches the sensor signal output to the variable gain amplifier 22 at time t3, the boost amplifier 26 indicates that the boost control signal output from the comparator 28 does not accelerate the vibration of the vibration sensor 10 ( The operation may be stopped in accordance with the change to Low “level = boost OFF. That is, the boost amplifier 26 may be configured to operate only when the vibration sensor 10 is activated. The power consumed by the boost amplifier 26 can be reduced during a period in which the vibration of the vibration sensor 10 is in a steady state, that is, the steady power consumption by the boost amplifier 26 can be reduced. Each of the comparator 28 and the boost reference circuit 29 is appropriately reduced in power consumption. It is thereby possible to suppress the power consumption of by component for accelerating the vibration of the vibration sensor 10.

  As described above, when the drive circuit 20 operates to accelerate the vibration of the vibration sensor 10, a sensor signal obtained by further amplifying the sensor signal output from the sensor amplifier 21 by the boost amplifier 26 is supplied to the variable gain amplifier 22. By inputting the vibration, the vibration of the vibration sensor 10 can be quickly and appropriately fixed (steady state) without increasing the gain (gain) of the variable gain amplifier 22 that causes the power consumption to increase. Can be. That is, it is possible to shorten the startup time for changing the vibration sensor 10 from a state in which it does not vibrate to a state in which it vibrates to an appropriate amplitude.

  In the physical quantity sensor device 1 provided with the drive circuit 20, when the vibration sensor 10 is intermittently operated in order to realize low power consumption, a physical quantity measurement circuit (not shown) detects a change in physical quantity more accurately and quickly. Therefore, after detecting an accurate physical quantity, the vibration sensor 10 can be put into a state of not vibrating more quickly. That is, the period during which the vibration sensor 10 is vibrating can be shortened. As a result, the physical quantity sensor device 1 including the drive circuit 20 can further reduce power consumption.

  As described above, according to the embodiment for carrying out the present invention, the activation time for switching the vibrator from the non-vibrating state to the appropriate vibrating state is increased in the vibrator driving circuit. The component for this is provided. More specifically, the drive circuit (drive circuit 20 in the embodiment) responds to the output signal (sensor output signal in the embodiment) output from the vibrator (vibration sensor 10 in the embodiment). An additional amplifier circuit (in the embodiment, a boost amplifier 26) that further amplifies the vibration signal (in the embodiment, the sensor signal) than in the steady state is provided. In addition, a vibration determination unit (in the embodiment, a comparator 28 and a boost reference circuit 29) for determining the vibration state of the vibrator is provided. In addition, a switching circuit (in the embodiment, a switch 27) that switches a signal used for generating a driving signal (in the embodiment, a sensor driving signal) between the steady state and the startup time is provided. Thus, in the embodiment for carrying out the present invention, an increase in power consumption is suppressed without increasing the amplification factor (gain) of the amplifier circuit that outputs the sensor drive signal when the vibration of the vibrator is in a steady state. On the other hand, when the drive circuit is turned on or when the vibrator is intermittently operated, the activation time of the vibrator can be shortened.

  As a result, in the embodiment for carrying out the present invention, the physical quantity measuring circuit is more effective even when the vibration sensor is intermittently operated in order to realize low power consumption in the physical quantity sensor device including the driving circuit of the present embodiment. Changes in physical quantities can be detected quickly and accurately. Moreover, in the form for implementing this invention, when operating a vibration sensor intermittently in the physical quantity sensor apparatus provided with the drive circuit of this embodiment, it is further reduced by shortening the period during which the vibration sensor vibrates. Power consumption can be realized. That is, in the embodiment for carrying out the present invention, in the physical quantity sensor device including the drive circuit of the present embodiment, the vibration sensor is intermittently operated to detect the period during which the vibration sensor vibrates, that is, the change in the physical quantity. It is possible to shorten the unit time required for the physical quantity sensor device and reduce the power consumption of the physical quantity sensor device.

  In the embodiment, the case where there is no fluctuation in the change of the gain control signal output from the error amplifier 24 in FIG. 2 has been described. However, the magnitude of the amplitude at which the vibration sensor 10 vibrates may vary depending on environmental factors such as, for example, the temperature around the vibration sensor 10 and the fluctuation of the pressure received by the vibration sensor 10. When the magnitude of the amplitude at which the vibration sensor 10 vibrates fluctuates, the gain control signal output from the error amplifier 24 also fluctuates with this fluctuation, that is, ringing may occur in the gain control signal. . For example, when ringing occurs in the gain control signal in the vicinity of the voltage = V2 shown in FIG. 2, the state of the boost control signal output from the comparator 28, that is, the state representing acceleration of vibration of the vibration sensor 10; The state indicating that the vibration of the vibration sensor 10 is not accelerated frequently changes. Thereby, switching of the sensor signal in the switch 27 is frequently performed. In this case, for example, it may be possible to avoid frequent changes in the boost control signal output from the comparator 28 and frequent switching of the sensor signal by the switch 27 by providing the comparator 28 with hysteresis characteristics.

  Each component provided in the drive circuit 20 can be realized by various methods. For example, components such as the amplitude detection circuit 23, error amplifier 24, amplitude reference circuit 25, comparator 28, boost reference circuit 29, AD (Analog-to-Digital), CPU (Central Processing Unit), etc. It may be realized by using a digital circuit such as a microcomputer, a DA (Digital-to-Analog) digital converter, or the like. Further, some or all of the functions of these components may be realized by an integrated circuit such as a dedicated LSI (Large Scale Integration), so-called ASIC (Application Specific Integrated Circuit).

  The embodiment of the present invention has been described above with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes various modifications within the scope of the present invention. It is.

DESCRIPTION OF SYMBOLS 1 ... Physical quantity sensor apparatus 10 ... Vibration sensor (vibrator)
20 ... Drive circuit (drive circuit)
21... Sensor amplifier 22... Variable gain amplifier (amplifier circuit)
23 ... Amplitude detection circuit (vibration detection unit)
24 ... Error amplifier (vibration detector)
25 ... Amplitude reference circuit (vibration detector)
26 ... Boost amplifier (additional amplification circuit)
27 ... Switch (switching circuit)
28 ... Comparator (vibration judgment unit, comparator)
29 ... Boost reference circuit (vibration judgment unit, reference circuit)

Claims (6)

A drive circuit for vibrating a vibrator used for measuring a physical quantity,
An amplification circuit that amplifies an input signal and outputs it as a drive signal for driving the vibrator;
A vibration state of the vibrator is detected based on a vibration signal corresponding to an output signal output from the vibrator, and the input circuit is multiplied by the input signal based on the detected vibration state of the vibrator. A vibration detector that determines and outputs a gain value;
A vibration determination unit that determines a vibration state of the vibrator based on a second gain value that can be determined that the vibrator vibrates in an appropriate vibration state and the first gain value; ,
An additional amplifier circuit that outputs an amplified signal obtained by multiplying the vibration signal by a predetermined gain value;
A switching circuit that switches the input signal amplified by the amplification circuit to either the vibration signal or the amplification signal based on a determination result of the vibration determination unit;
Comprising
A drive circuit characterized by that. The vibration determination unit
When the first gain value is greater than the second gain value, it is determined that the vibrator is not vibrating in an appropriate vibration state;
When the first gain value is less than or equal to the second gain value, it is determined that the vibrator is vibrating in an appropriate vibration state;
The switching circuit is
When the vibration determination unit determines that the vibrator is not vibrating in an appropriate vibration state, the amplified signal is used as the input signal,
When the vibration determination unit determines that the vibrator is vibrating in an appropriate vibration state, the vibration signal is used as the input signal.
The drive circuit according to claim 1. The vibration determination unit
A reference circuit for outputting the second gain value;
A comparator that compares the second gain value with the first gain value currently output by the vibration detection unit and outputs the comparison result as the determination result for determining the vibration state of the vibrator. When,
Comprising
The drive circuit according to claim 1, wherein the drive circuit is provided. The second gain value is
The vibration value of the vibrator is a gain value at the upper limit of the range of the first gain value that can be determined as steady-state vibration that can be used to measure the physical quantity.
The drive circuit according to any one of claims 1 to 3, wherein: The vibration determination unit
Determining the vibration state of the vibrator at the start-up time of the vibrator that causes the vibrator to be in an appropriate vibration state from a state of not vibrating;
The switching circuit is
The input signal to be amplified by the amplifier circuit is switched based on a determination result of the vibration determination unit at the startup time.
The drive circuit according to any one of claims 1 to 4, wherein the drive circuit is provided. The drive circuit according to any one of claims 1 to 5,
A physical quantity measurement circuit that detects a change in vibration in the vibrator and measures a physical quantity based on the detected change in vibration;
Comprising
A physical quantity sensor device.

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