JP5660301B2 - Detection circuit, physical quantity measuring device - Google Patents

Description

  The present invention relates to a detection circuit, a physical quantity measurement device, and the like.

  The output signal from the physical quantity measuring device may include unnecessary signal components unnecessary for measurement in addition to the detection signal for detecting the physical quantity to be measured. In the physical quantity measuring device, for example, the detected analog signal is subjected to filter processing and amplification, the signal after synchronous detection is smoothed, converted into a DC voltage, and the amplified signal is output. Here, a processing block before synchronous detection is called an AC stage, and a processing block after synchronous detection is called a DC stage. In the AC stage, there are a parallel component unnecessary signal having the same phase as that of the detection signal, and a quadrature component unnecessary signal having a phase difference of 90 degrees from the detection signal.

  The unnecessary signal of the parallel component directly affects the detection signal even in the DC stage. Further, although the unnecessary signal of the orthogonal component is removed by the synchronous detection, for example, as described in Patent Document 1, the unnecessary signal of the orthogonal component may affect the detection signal by generating an unnecessary charge in the AC stage. is there. Therefore, in the invention of Patent Document 1, the signal excluding the influence of the unnecessary signal is output by canceling the unnecessary signal by the addition / subtraction amplifier circuit.

JP 2010-071909 A

  However, in the invention of Patent Document 1, it is necessary to add a 90-degree phase shift circuit to the detection circuit of the physical quantity measuring device in order to generate a signal for canceling the unnecessary signal of the orthogonal component. As a result, the circuit scale increases.

  The present invention has been made in view of such problems. According to some aspects of the present invention, it is possible to provide a detection circuit or the like that realizes a reduction in noise of an output signal by canceling an unnecessary signal while suppressing an increase in circuit scale.

(1) The present invention is a detection circuit that detects a physical quantity applied to the sensor element based on a differential input signal from the sensor element, and amplifies the difference between the differential input signals, A differential amplifier circuit that outputs the signal, a high-pass filter that transmits the high-frequency component of the first signal and outputs the second signal, and amplifies the second signal and outputs it as a third signal The high-pass filter includes a capacitor having a first terminal to which the first signal is input and a second terminal for outputting the second signal; A resistor including a third terminal connected to the terminal and a fourth terminal to which a cancel signal is input, and the cancel signal is phase-shifted by 90 degrees to be combined with the first signal, Included in the differential input signal Offsetting at least a portion of the undesired signal is an unnecessary signal to the detection of the physical quantity are.

  According to the present invention, since the high-pass filter used for transmitting high-frequency components in normal processing is used as a cancel circuit for unnecessary signals, unnecessary signals are canceled while suppressing an increase in circuit scale, and the output signal is reduced. Noise can be realized. The high-pass filter includes a resistor and a capacitor, and functions as a low-pass filter when viewed from the fourth terminal side to which the cancel signal is input. Since the phase of the cancel signal is delayed by 90 degrees, for example, if a signal having a phase obtained by inverting the first signal (output of the differential amplifier circuit) is selected as the cancel signal, an unnecessary signal orthogonal to the first signal is selected. Can be canceled (offset).

  Here, as the cancel signal, a signal based on the differential input signal may be appropriately selected from the inside and outside of the detection circuit and used. As will be described later, by canceling an unnecessary signal whose phase is delayed by 90 degrees in the AC stage, it is possible to reduce the composite amplitude of the signal in the AC stage that affects the setting upper limit value of the analog gain.

(2) In this detection circuit, the AC amplifier may set an upper limit of an amplification factor based on a signal level of the second signal from which at least a part of the unnecessary signal is canceled.

  According to the present invention, the upper limit of the amplification factor of the AC amplifier can be set based on the signal level of the second signal (the output of the high-pass filter) from which at least a part of the unnecessary signal has been canceled. The upper limit can be set larger than when the upper limit of the amplification factor is set based on the signal level of a signal obtained by combining a detection signal that detects a physical quantity that is a measurement target and an unnecessary signal that is unnecessary for measurement. Is possible. Then, since it becomes possible to take a large detection signal in the AC stage, the S / N ratio is improved and the physical quantity applied to the sensor element can be detected with high accuracy.

(3) In this detection circuit, the sensor element is a vibrator and receives a reference phase signal that is a signal based on the excitation current of the vibrator, and the high-pass filter includes a storage unit that is a nonvolatile memory; And a programmable gain amplifier capable of changing an amplification factor according to a setting signal from the storage unit, and the reference phase signal may be amplified by the programmable gain amplifier to be a cancel signal.

(4) In this detection circuit, the high-pass filter may be capable of setting an amplification factor of the programmable gain amplifier to zero.

  According to these inventions, since the gain of the cancel signal can be selected by the programmable gain amplifier, it becomes possible to cancel the unnecessary signal with certainty. When there is no unnecessary signal to be canceled, it is preferable that the gain of the programmable gain amplifier can be made zero. Specifically, setting the amplification factor to 0 may be connecting to an analog ground potential instead of inputting a cancel signal.

(5) In this detection circuit, the AC amplifier includes an inverting amplifier circuit, and the cancellation signal is input to the other end of the resistor connected to the inverting input terminal of the inverting amplifier circuit, and the differential input You may cancel at least one part of the unnecessary signal which is a signal unnecessary for the detection of the said physical quantity contained in the signal.

(6) The present invention is a detection circuit that detects a physical quantity applied to the sensor element based on a differential input signal from the sensor element, and amplifies the difference between the differential input signals, A differential amplifier circuit that outputs the signal, a high-pass filter that transmits the high-frequency component of the first signal and outputs the second signal, and amplifies the second signal and outputs it as a third signal And the AC amplifier includes an inverting amplifier circuit, the cancel signal is input to the other end of the resistor connected to the inverting input terminal of the inverting amplifier circuit, and the differential input At least a part of an unnecessary signal that is an unnecessary signal for detecting the physical quantity included in the signal is canceled.

  According to these inventions, an AC amplifier used for signal amplification in normal processing is used as a cancel circuit for unnecessary signals. Therefore, unnecessary signals are canceled while suppressing an increase in circuit scale, thereby reducing output signal noise. Can be realized. Although the AC amplifier includes an inverting amplifier circuit, the other end of the resistor connected to the inverting input terminal is not grounded, but the cancel signal is input. For example, if a signal having a phase obtained by inverting the second signal (the output of the high-pass filter) is selected as a cancel signal, an unnecessary signal that is a parallel component can be canceled.

(7) In this detection circuit, the AC amplifier sets an upper limit of the amplification factor based on the signal level of the third signal from which at least a part of the unnecessary signal is canceled.

  According to the present invention, the upper limit of the amplification factor of the AC amplifier can be set based on the signal level of the third signal (output of the AC amplifier) from which at least a part of the unnecessary signal is canceled. The upper limit can be set larger than when the upper limit of the amplification factor is set based on the signal level of a signal obtained by combining a detection signal that detects a physical quantity that is a measurement target and an unnecessary signal that is unnecessary for measurement. Is possible. Then, since it becomes possible to take a large detection signal in the AC stage, the S / N ratio is improved and the physical quantity applied to the sensor element can be detected with high accuracy.

(8) In this detection circuit, the sensor element is a vibrator and receives a reference phase signal that is a signal based on an excitation current of the vibrator, and the AC amplifier includes a storage unit that is a nonvolatile memory; And a programmable gain amplifier capable of changing an amplification factor according to a setting signal from the storage unit, and the reference phase signal may be amplified by the programmable gain amplifier to be a cancel signal.

  According to the present invention, since the gain of the cancel signal can be selected by the programmable gain amplifier, the unnecessary signal can be canceled with certainty. At this time, when there is no unnecessary signal to be canceled, the gain of the programmable gain amplifier may be set to zero. Specifically, setting the amplification factor to 0 may be connecting to an analog ground potential instead of inputting a cancel signal.

(9) The present invention is a physical quantity measuring device including any one of the detection circuits described above.

  According to the present invention, it is possible to cancel an unnecessary signal while suppressing an increase in circuit scale and to reduce the noise of an output signal.

The block diagram of the detection circuit of 1st Embodiment. The figure of the physical quantity measuring device containing the detection circuit of a 1st embodiment. The block diagram of a drive circuit. FIG. 4A shows the influence of unnecessary signals. FIG. 4B shows a flow of removing unnecessary signals. The figure which shows the example of the circuit in the AC stage of the detection circuit of 1st Embodiment. The figure which shows the example of the circuit in the cancellation signal production | generation part of 1st Embodiment. The figure which shows the example of the circuit in DC stage of the detection circuit of 1st Embodiment.

1. First Embodiment A first embodiment of the present invention will be described with reference to FIGS.
1.1. Configuration of Detection Circuit According to this Embodiment FIG. 1 is a block diagram of a detection circuit 10 according to this embodiment. The detection circuit 10 receives the differential input signals 290 and 292 from the sensor elements at the input terminal (S1) 104 and the input terminal (S2) 106, respectively. In this embodiment, noise-resistant differential input is performed, but single-ended input may be used. The differential input signals 290 and 292 include a detection signal for detecting a physical quantity to be measured and an unnecessary signal unnecessary for measurement. The detection circuit 10 performs necessary processing on the analog signal based on the differential input signals 290 and 292 in the AC stage 12 and converts it into a DC voltage in the DC stage 14 including the synchronous detection circuit 60 to perform necessary processing. . Then, the final output signal 294 is output from the output terminal (VO1) 108.

  The AC stage 12 of the detection circuit 10 includes charge amplifiers 20-1 and 20-2, a differential amplifier circuit (differential amplifier) 30, a high-pass filter (HPF) 40, and an AC amplifier 50. The DC stage 14 of the detection circuit 10 includes a synchronous detection circuit 60 and a detection signal output unit 70.

  The charge amplifiers 20-1 and 20-2 amplify the differential input signals 290 and 292, respectively. The charge amplifier 20-1 and the charge amplifier 20-2 have the same configuration, and each of the differential input signals 290 and 292 is phase-shifted in the same manner. The charge amplifiers 20-1 and 20-2 may be omitted.

  The differential amplifier circuit 30 receives both the signals 110 and 112 output from the charge amplifiers 20-1 and 20-2, amplifies the difference between these signals, and outputs the amplified signal as the first signal 114. The high pass filter 40 transmits the high frequency component of the first signal 114 and outputs it as the second signal 116. Then, the AC amplifier 50 amplifies the second signal 116 and outputs the third signal 118 to the DC stage 14.

  The synchronous detection circuit 60 receives the third signal 118 and performs synchronous detection. The detection signal output unit 70 receives the signal 120 output from the synchronous detection circuit 60, generates a signal converted into a DC voltage by a smoothing process such as a low-pass filter, and amplifies the obtained DC voltage. . The obtained signal is output as an output signal 294.

  Here, the detection circuit 10 of the present embodiment receives the reference phase signal 202. Then, using the high-pass filter 40 and the AC amplifier 50 used in normal processing, unnecessary signals are removed while suppressing an increase in circuit scale. The high-pass filter 40 and the AC amplifier 50 generate a cancel signal for canceling the unnecessary signal based on the reference phase signal 202 and synthesize it with the first signal 114 or the second signal 116. Here, the reference phase signal 202 may be a signal based on the excitation current of the vibrator when the sensor element is a vibrator, for example. Since the detection circuit 10 of the present embodiment uses the high-pass filter 40 and the AC amplifier 50 as a cancel circuit for unnecessary signals, it is possible to cancel the unnecessary signals while suppressing an increase in circuit scale, and to realize a reduction in noise of the output signal. .

1.2. 2 is a configuration example of a physical quantity measuring device 1 including a detection circuit 10 according to the present embodiment. The detection circuit 10 of the present embodiment functions as a detection part of the physical quantity measuring device 1. Note that the same elements as those in FIG.

The physical quantity measuring device 1 includes a detection circuit 10, a drive circuit 410, and vibrators 2 and 3 that are sensor elements. Here, the vibrators 2 and 3 may be integrated. For example, when the physical quantity measuring device 1 is a gyro sensor, the physical quantity applied to the sensor element is Coriolis force. The Coriolis force is a force acting in a direction orthogonal to the vibration direction of the object and the rotation axis when the vibrating object is rotated. At this time, the vibrators 2 and 3 are integrated, and include a drive electrode that inputs and outputs an excitation current 200 and a drive signal 208 from the drive circuit 410, and a detection electrode that outputs differential input signals 290 and 292. May be. Regardless of whether or not the vibrators 2 and 3 are integrated, the vibrator 3 has a differential input signal 290 proportional to the physical quantity detected by the sensor element and the amplitude I _dr of the excitation current 200 of the vibrator 2. 292 is output.

  Here, the detection circuit 10 may receive the reference phase signal 202 from the drive circuit 410. As a specific example, the reference phase signal 202 may be a signal obtained by converting the excitation current 200 into a voltage by a current-voltage conversion circuit. At this time, the differential input signals 290 and 292 and the reference phase signal 202 are signals generated based on the excitation current 200 and are related to each other. The unnecessary signals included in the differential input signals 290 and 292 are similarly related to the reference phase signal 202. For example, in the circuit example described later, the phase of the unnecessary signal is parallel or orthogonal to the reference phase signal 202. doing.

1.3. Drive Circuit FIG. 3 is an example of a block diagram of the drive circuit 410 included in the physical quantity measuring device 1. The same elements as those in FIGS. The drive circuit 410 includes a current-voltage conversion circuit 420, a full-wave rectification circuit 430, a comparison adjustment circuit 440, and a drive signal generation circuit 450.

  The current-voltage conversion circuit 420 converts the excitation current 200 from the vibrator 2 into a voltage and outputs an output voltage 202. In the present embodiment, the output voltage 202 is a reference phase signal. The amplitude of the output voltage 202 is proportional to the amplitude of the excitation current 200. The full-wave rectifier circuit 430 performs full-wave rectification on the output voltage 202 from the current-voltage conversion circuit 420 to obtain a voltage close to direct current, and outputs the output voltage 204. The comparison adjustment circuit 440 compares the output voltage 204 from the full-wave rectification circuit 430 with the voltage from the comparison voltage supply circuit 442, and outputs an output voltage 206 that is a signal reflecting the comparison result to the drive signal generation circuit 450. The drive signal generation circuit 450 generates the drive signal 208 based on the output voltage 202 from the current-voltage conversion circuit 420, and adjusts the amplitude of the drive signal 208 based on the output voltage 206. Then, the excitation current 200 from the vibrator 2 is stabilized by this amplitude adjusting function, and as a result, the physical quantity detection signal measured by the physical quantity measuring device 1 is stabilized.

1.4. Reasons for Eliminating Unnecessary Signals at the AC Stage Here, the reasons for eliminating unnecessary signals at the AC stage in the detection circuit 10 will be described. Here, description will be made using a specific example on the assumption that the physical quantity measuring device including the detection circuit of the present embodiment is a gyro sensor. The signals in FIG. 4A are a gyro signal 130, a stationary gyro signal 132, and a vibration leakage signal 134, and the direction of each arrow indicates a phase relationship. That is, only the vibration leakage signal 134 has a phase delayed by 90 degrees. In FIG. 4A, ppm, which is a unit of numerical values, is, for example, a ratio to the excitation current of a vibrator that is a sensor element.

  The gyro signal 130 is a detection signal obtained by detecting the angular velocity that is the measurement target. The stationary gyro signal 132 is a signal that is output while the physical quantity measuring device is stationary, and may include an offset or the like. The vibration leakage signal 134 is a signal that is output even when Coriolis force is not generated due to processing accuracy of the vibrator as a sensor element or nonuniformity of the material. The stationary gyro signal 132 and the vibration leakage signal 134 are unnecessary signals.

  Among these signals, the vibration leakage signal 134 is delayed by 90 degrees in phase with respect to the gyro signal 130, and can be removed by, for example, a synchronous detection circuit included in the DC stage of FIG. Further, the stationary gyro signal 132 can be removed by adding or subtracting an appropriate signal level at, for example, a detection signal output unit included in the DC stage. Therefore, it seems that unnecessary signals need not be removed at the AC stage. However, as described below, in order to suppress the increase in circuit scale as much as possible and improve the S / N ratio, it is necessary to remove unnecessary signals at the AC stage.

Here, amplification of the signal in the AC stage is called an analog gain, and that in the DC stage is called a digital gain. The analog gain is performed by, for example, a differential amplifier or an AC amplifier, and for the digital gain, for example, a multiplier is used or a bit shift is performed. In order for the gyro sensor to output a signal of an appropriate voltage level to a subsequent device or the like, it is necessary to be able to set the gain up to G _max by combining the analog gain and the digital gain. That is, it is necessary to satisfy G _max = AG _max × DG _max using the analog gain setting upper limit value AG _max and the digital gain setting upper limit value DG _max .

Here, the upper limit set value AG _max of the analog gain is determined based not only on the detection signal 130 but also on the amplitude of the combined signal 136 with the unnecessary signal. For example, if the amplitude of the amplified signal must be 500 [ppm] or less as a design constraint, AG _max = 1.4 because the amplitude of the synthesized signal 136 is 360 [ppm]. When G _max = 10, DG _max = 8. In other words, when the unnecessary signal is removed in the DC stage, the upper limit set value of the analog gain becomes small, so that the upper limit set value of the digital gain needs to be increased. As a result, the bus width of the data path in the DC stage, the size of the memory, multiplier, etc. used for temporary storage of data increase, and the circuit scale increases.

On the other hand, when the unnecessary signal is removed in the AC stage, the stationary gyro signal 132 and the vibration leakage signal 134 are canceled, so that the amplitude of the combined signal 136 is 200 [ppm] as in the detection signal 130. At this time, since AG _max = 2.5 in the above example, DG _max = 4 may be sufficient. That is, when unnecessary signals are removed in the AC stage, the circuit scale does not increase in the DC stage. Therefore, it is desirable to remove unnecessary signals at the AC stage.

  FIG. 4B is a diagram illustrating a flow of removing unnecessary signals in the AC stage. Here, the detection signal 130 is represented as Acos (ωt), the stationary gyro signal 132 that is a parallel component unnecessary signal is represented as Bcos (ωt), and the vibration leakage signal 134 that is a quadrature component unnecessary signal is represented as Csin (ωt). . The input signal 140 at the AC stage is a composite signal of these. The desired output signal 146 is a signal in which the unnecessary signal is canceled and only the detection signal 130 remains. In order to obtain such an output signal 146, a cancel signal 142 (-Bsin (ωt)) for canceling the unnecessary signal of the orthogonal component and a cancel signal 144 (-Bcos (ωt)) for canceling the unnecessary signal of the parallel component are obtained. May be combined with the input signal 140.

  Here, since the two cancel signals differ only in the amplitude and the phase shifted by 90 degrees, it is desirable to generate them from one signal in order to suppress the increase in circuit scale as much as possible. In addition, an operation for synthesizing a cancel signal with the input signal 140 can also suppress an increase in circuit scale if an existing circuit used in normal processing can be used.

  In the first embodiment, based on one reference phase signal 202, two cancellation signals for an unnecessary signal of a quadrature component and an unnecessary signal of a parallel component are obtained using the high-pass filter 40 and the AC amplifier 50 used in normal processing. Thus, the S / N ratio of the output signal 294 can be improved while suppressing an increase in circuit scale.

1.5. Details of detection circuit of this embodiment 1.5.1. AC Stage FIG. 5 is a diagram illustrating an example of a circuit in the AC stage 12 of the detection circuit of the present embodiment. The same elements as those in FIGS.

  The charge amplifiers 20-1 and 20-2 have the same configuration, and may include, for example, an operational amplifier 26, a resistor (feedback resistor) 24, and a capacitor (feedback capacitor) 22. At this time, phase adjustment such as delaying by 90 degrees may be performed by appropriately setting the resistance value of the resistor 24 and the capacitance of the capacitor 22.

  The differential amplifier circuit 30 may be composed of resistors 32, 33, 34, and 35 and an operational amplifier 36, for example. The first signal 114 output from the differential amplifier circuit 30 can correspond to the input signal 140 in FIG.

  The high-pass filter 40 may be composed of, for example, a capacitor 42, a resistor 44, and a cancel signal generation unit 80-1. The cancel signal 122-1 of the high pass filter 40 can be made to correspond to the cancel signal 142 for canceling the unnecessary signal of the orthogonal component in FIG. The cancel signal generation unit 80-1 includes a switch that can fix the cancel signal 122-1 to the analog ground potential, and a cancel signal generation circuit 82- that generates the cancel signal 122-1 based on the reference phase signal 202. 1 may be comprised. Details of the cancel signal generation circuit 82-1 of this embodiment will be described later.

  For example, the AC amplifier 50 may include resistors 54 and 56, an operational amplifier 52, and a cancel signal generation unit 80-2. In the present embodiment, the cancel signal generation unit 80-1 and the cancel signal generation unit 80-2 have the same configuration, and thus description thereof is omitted. The cancel signal 122-2 of the AC amplifier 50 can correspond to the cancel signal 144 for canceling the unnecessary signal of the parallel component in FIG. In addition, the third signal 118 output from the AC amplifier 50 can correspond to the output signal 146 in FIG. In the present embodiment, the unnecessary signal is canceled from the output signal of the AC stage, and the detection signal component remains.

1.5.2. High Pass Filter Cancel Signal Phase In this embodiment, both the high pass filter 40 and the AC amplifier 50 include cancel signal generation units 80-1 and 80-2 having the same configuration using the same reference phase signal 202 as an input signal. However, the phases of the cancel signal 122-1 of the high pass filter 40 and the cancel signal 122-2 of the AC amplifier 50 need to be shifted by 90 degrees when combined with the unnecessary signal. In the present embodiment, the high-pass filter 40 is used as a phase shift circuit, thereby realizing this without adding a circuit.

A high-pass filter composed of a capacitor 42 (capacitance C ₀ ) and a resistor 44 (resistance value R ₀ ) can be defined as a low-pass filter when the cancel signal 122-1 is viewed as an input, and its transfer function is Become.

By setting appropriate C ₀ and R ₀ with respect to the operating frequency, the phase can be delayed by 90 degrees. For example, when the example of FIG. 4B is used, even if the cancel signal 122-1 is -Ccos (ωt), it is converted to -Csin (ωt) at the time of synthesis with an unnecessary signal without separately providing a phase shift circuit. it can.

1.5.3. Cancel Signal Generation Unit FIG. 6 is a diagram illustrating an example of a circuit in the cancel signal generation unit 80-1 of the present embodiment. The same elements as those in FIGS. Although the cancel signal generation unit 80-1 will be described here, the cancel signal generation unit 80-2 has the same configuration.

  The cancel signal generation unit 80-1 according to this embodiment includes a switch that can fix the cancel signal 122-1 to the analog ground potential, and a cancel signal that generates the cancel signal 122-1 based on the reference phase signal 202. A generation circuit 82-1 is included. The cancel signal generation circuit 82-1 provides a phase adjustment unit 86 that can select a normal or inverted signal, a programmable gain amplifier 88 that can change the amplification factor of the output signal of the phase adjustment unit 86, and control signals 124A to 124C. A storage unit (flash memory) 84 which is a nonvolatile memory is included. The storage unit 84 is not limited to a flash memory, and may be a mask ROM or the like.

  The phase adjustment unit 86 of the present embodiment receives the reference phase signal 202, performs phase adjustment with a low-pass filter composed of a resistor 303 and a capacitor 305, and a non-inverting amplification composed of resistors 302 and 304 and an operational amplifier 306. Amplify in circuit. If phase adjustment is not necessary, the low-pass filter may be omitted. Then, the output signal from the non-inverting amplifier circuit is inverted by the comparator 308, and the signal that is normally or inverted is selected by the switches 310 and 311 that are exclusively turned on. A control signal 124 A for selecting the switches 310 and 311 is given from the storage unit 84. The value of the control signal 124A is determined by the phase relationship between the differential input signals 290 and 292 (see FIG. 5) and the reference phase signal 202.

  The programmable gain amplifier 88 amplifies the amplitude of the output signal from the phase adjustment unit 86 to a level that can cancel the unnecessary signal. The programmable gain amplifier 88 according to the present embodiment includes an inverting amplifier circuit including a resistor 312, a variable resistor 314, and an operational amplifier 316. The resistance value of the variable resistor 314 is determined by the control signal 124B. Since there is an individual difference in the magnitude of the unnecessary signal, for example, an appropriate value of the control signal 124B may be selected at the time of manufacture and the information may be recorded in the storage unit 84.

  The cancel signal generation unit 80-1 preferably includes a switch that enables the cancel signal 122-1 to be fixed to the analog ground potential at the final stage. This is because the control signal 124C can fix the analog ground potential when there is no unnecessary signal to be canceled.

By including the cancel signal generation units 80-1 and 80-2 having such a configuration, the high-pass filter 40 and the AC amplifier 50 can appropriately cancel unnecessary signals. Therefore, it is possible to increase the set upper limit value AG _max of the analog gain, and it is possible to improve the S / N ratio while suppressing an increase in the circuit scale of the entire detection circuit.

1.5.4. DC Stage FIG. 7 is a diagram illustrating an example of a circuit in the DC stage 14 of the detection circuit of the present embodiment. The same elements as those in FIGS.

  The DC stage 14 of the detection circuit receives the third signal 118 output from the AC stage 12 and performs synchronous detection, and receives the output signal from the synchronous detection circuit 60 and performs necessary processing. A detection signal output unit 70 for outputting the output signal 294.

  The synchronous detection circuit 60 generates an inverted signal of the third signal 118 by an inverting amplifier circuit including resistors 62 and 64 and an operational amplifier 66. Then, the forward or inverted signal is selected by the switches 68 and 69 that are exclusively turned on. The selection signal SDET of the switches 68 and 69 may be a pulse signal given from the outside of the synchronous detection circuit 60, for example.

  The detection signal output unit 70 may include a low-pass filter configured by combining resistors 71 and 73 and capacitors 72 and 74, respectively. The low-pass filter functions as a pre-filter for synchronous detection smoothing processing and subsequent processing. The detection signal output unit 70 may include a variable gain amplifier including variable resistors 76 and 77 and an operational amplifier 75. For example, the variable gain amplifier is used as a digital gain that can be set by the user in the physical quantity measuring device including the detection circuit of the present embodiment. Further, the output signal 294 may be output via the switched capacitor filter 78 for anti-aliasing.

  In the present embodiment, since unnecessary signals are canceled at the AC stage of the detection circuit, the gain setting at the AC stage can be increased. By setting the AC stage to a high gain and setting the gain at the DC stage to a low level, it is possible to output an output signal 294 with good low noise.

2. Modifications The detection circuit of the present invention can be modified as follows.

  In the first embodiment, both the orthogonal component unnecessary signal and the parallel component unnecessary signal are canceled, but only one of them may be canceled. For example, when the unnecessary signal of the orthogonal component is very small, by providing a circuit that cancels only the unnecessary signal of the parallel component, the circuit scale can be further suppressed without significantly reducing the effect of canceling the unnecessary signal.

  In the first embodiment, the high-pass filter 40 and the AC amplifier 50 have the cancel signal generation circuits 82-1 and 82-2 independently, but some of them may be shared. As a specific example, the phase adjustment unit 86 (see FIG. 6) may be shared. As a result, the circuit scale can be further reduced.

  In the first embodiment, the cancel signal generation circuits 82-1 and 82-2 receive one common reference phase signal 202, but may receive individual reference phase signals. The cancel signal generation circuits 82-1 and 82-2 may include a circuit that bypasses the low-pass filter for phase adjustment (see the resistor 303 and the capacitor 305 in FIG. 6). These modifications increase the versatility of the cancel signal generation circuit and make it possible to deal with various unnecessary signals. In addition, when a signal generated by the drive circuit 410 is used as the reference phase signal 202, the cancel signal generation circuits 82-1 and 82-2 may be included in the drive circuit 410.

  The present invention is not limited to these exemplifications, and includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Physical quantity measuring device, 2, 3 ... Vibrator, 10 ... Detection circuit, 12 ... AC stage, 14 ... DC stage, 20-1, 20-2 ... Charge amplifier, 22, 42, 72, 74, 305 ... Capacitor 24, 32, 33, 34, 35, 44, 54, 56, 62, 64, 71, 73, 302, 303, 304, 307, 309, 312 ... resistor, 26, 36, 52, 66, 75, 306, 316 ... operational amplifier, 30 ... differential amplifier circuit (differential amplifier), 40 ... high pass filter (HPF), 50 ... AC amplifier, 60 ... synchronous detection circuit, 68, 69, 310, 311 ... switch, 70 ... detection Signal output unit, 76, 77, 314 ... Variable resistor, 78 ... Switched capacitor filter, 80-1, 80-2 ... Cancel signal generation unit, 82-1, 82-2 ... Cancel signal generation times 84: Storage unit (flash memory) 86: Phase adjustment unit 88 ... Programmable gain amplifier 100 ... Input terminal (DG) 102 ... Output terminal (DS) 104 ... Input terminal (S1) 106: Input terminal (S2), 108 ... output terminal (VO1), 110, 112, 120 ... signal, 114 ... first signal, 116 ... second signal, 118 ... third signal, 122-1, 122-2, 142 , 144 ... Cancel signal, 124A, 124B, 124C ... Control signal, 130 ... Detection signal (gyro signal), 132 ... Gyro signal at rest, 134 ... Vibration leak signal, 136 ... Composite signal, 140 ... Input signal, 146, 294 ... Output signal, 200 ... Excitation current, 202 ... Reference phase signal (output voltage), 204,206 ... Output voltage, 208 ... Drive signal, 290,292 Differential input signal, 308 ... comparator, 410 ... driving circuit, 420 ... current-voltage conversion circuit, 430 ... full-wave rectifier circuit, 440 ... comparable circuit, 442 ... reference voltage supply circuit, 450 ... driving signal generating circuit

Claims (6)

A detection circuit for detecting a physical quantity applied to the sensor element based on a differential input signal from the sensor element;
A differential amplifying circuit for amplifying a difference between the differential input signals and outputting as a first signal;
A high-pass filter that transmits a high-frequency component of the first signal and outputs it as a second signal;
An AC amplifier that amplifies the second signal and outputs it as a third signal;
The high-pass filter is
A capacitor comprising a first terminal to which the first signal is input, and a second terminal for outputting the second signal;
A resistor including a third terminal connected to the second terminal and a fourth terminal to which a cancel signal is input;
A detection circuit that phase-shifts the cancel signal by 90 degrees and combines it with the first signal to cancel at least part of the unnecessary signal that is unnecessary for detecting the physical quantity included in the differential input signal. . The detection circuit according to claim 1,
The AC amplifier
A detection circuit in which an upper limit of an amplification factor is set based on a signal level of the second signal from which at least a part of the unnecessary signal is canceled. The detection circuit according to claim 1,
The sensor element is a vibrator,
Receiving a reference phase signal which is a signal based on the excitation current of the vibrator;
The high-pass filter is
A storage unit that is a non-volatile memory;
A programmable gain amplifier capable of changing the amplification factor according to the setting signal from the storage unit,
A detection circuit that amplifies the reference phase signal by the programmable gain amplifier to generate a cancel signal. The detection circuit according to claim 3, wherein
The high-pass filter is
A detection circuit capable of setting an amplification factor of the programmable gain amplifier to zero. The detection circuit according to any one of claims 1 to 4,
The AC amplifier
Including an inverting amplifier circuit,
The cancel signal is input to the other end of the resistor connected to the inverting input terminal of the inverting amplifier circuit, and an unnecessary signal which is an unnecessary signal for detecting the physical quantity included in the differential input signal A detection circuit that cancels at least a portion. Physical quantity measuring device comprising a detection circuit according to any one of claims 1 to 5.

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