Phase locked loop circuit and sensing device

Abstract

To provide a phase synchronization circuit and a sensing device, which are capable of changing an oscillation frequency with good followability even when a resonance frequency changes with time due to a change in environmental conditions such as a temperature.SOLUTION: The phase synchronization circuit includes: a first oscillator that changes a frequency depending on a first control signal; a resonance element that resonates at a predetermined resonance frequency and outputs a signal obtained by shifting a phase of an output signal of the first oscillator by 90 degrees at the resonance frequency; a second oscillator that changes a frequency depending on a second control signal; a first phase detector that detects a first phase error between an output signal of the resonance element and the output signal of the second oscillator; a control unit that generates a first signal including at least the proportional component of the first phase error; and a first auxiliary signal generator that generates a second signal proportional to at least the differential component of the first phase error. The first control signal is a signal depending on the first signal, and the second control signal is a signal depending on the first signal and the second signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present embodiment relates to a phase locked loop circuit and a sensing device. [Background technology]

[0002] 2. Description of the Related Art A phase locked loop circuit is known that performs feedback control so that the oscillation frequency of a variable frequency oscillator does not change even when the resonance frequency of a resonance element changes due to environmental conditions such as temperature.

[0003] However, it is difficult to accurately change the oscillation frequency to follow changes in the resonance frequency due to environmental conditions such as temperature, and a frequency error occurs between the oscillation frequency and the resonance frequency. Therefore, in a physical quantity detection sensor using this type of phase-locked loop, the frequency error between the oscillation frequency and the resonance frequency reduces the detection accuracy of the physical quantity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-97354 [Patent Document 2] U.S. Patent No. 4,951,508 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, this embodiment provides a phase locked loop circuit and a sensing device that can change the oscillation frequency with good tracking even if the resonance frequency changes over time due to changes in environmental conditions such as temperature. [Means for solving the problem]

[0006] The phase locked loop circuit of this embodiment includes a first oscillator that varies its frequency in response to a first control signal, a resonant element that resonates at a predetermined resonant frequency and outputs a signal that is 90 degrees out of phase with the output signal of the first oscillator at the resonant frequency, a second oscillator that varies its frequency in response to a second control signal, a first phase detector that detects a first phase error between the output signal of the resonant element and the output signal of the second oscillator, a control unit that generates a first signal that includes at least a proportional component of the first phase error, and a first auxiliary signal generator that generates a second signal that is proportional to at least a differential component of the first phase error, wherein the first control signal is a signal that depends on the first signal, and the second control signal is a signal that depends on the first signal and the second signal. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a block diagram of a phase locked loop according to a first embodiment. [Figure 2] FIG. 1 is a block diagram of a phase locked loop circuit according to a comparative example. [Figure 3] FIG. 10 is a block diagram of a phase locked loop circuit according to a second embodiment. [Figure 4] FIG. 10 is a block diagram of a phase locked loop in a case where a control unit performs proportional control and integral control in a second embodiment. [Figure 5] FIG. 10 is a block diagram of a phase locked loop circuit according to a third embodiment. [Figure 6] FIG. 10 is a block diagram of a phase locked loop circuit according to a fourth embodiment. [Figure 7] FIG. 10 is a block diagram of a phase locked loop circuit according to a fifth embodiment. [Figure 8] FIG. 13 is a block diagram of a phase locked loop circuit according to a sixth embodiment. [Figure 9A] FIG. 13 is a block diagram of a phase locked loop circuit according to a seventh embodiment. [Figure 9B] FIG. 13 is a block diagram of a phase locked loop circuit in which a first phase detector is configured with a multiplier and a low-pass filter in a seventh embodiment. [Figure 10A]FIG. 13 is a block diagram of a sensing device according to an eighth embodiment. [Figure 10B] FIG. 20 is a block diagram showing an example of the configuration of a second phase detector in the eighth embodiment. [Figure 11] FIG. 13 is a block diagram of a sensing device according to a ninth embodiment. [Figure 12] FIG. 22 is a block diagram of a sensing device according to a tenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] (First embodiment) Fig. 1 is a block diagram of a phase locked loop 1 according to a first embodiment, and Fig. 2 is a block diagram of a phase locked loop 100 according to a comparative example. First, the operating principle of the phase locked loop will be described using the phase locked loop 100 according to the comparative example in Fig. 2.

[0010] The phase locked loop 100 of FIG. 2 includes an oscillator 200, a resonant element 300, a phase detector 400, and a control unit 500.

[0011] Oscillator 200 generates an oscillation signal whose frequency is variable. More specifically, oscillator 200 controls the frequency of the oscillation signal based on a first control signal output from control unit 500. Oscillator 200 generates an oscillation signal with a frequency obtained by multiplying the first control signal by a frequency conversion coefficient K.

[0012] The output signal (oscillation signal) of the oscillator 200 is input to the resonant element 300. The resonant element 300 resonates at a predetermined resonant frequency. The resonant element has a steep Q value (Quality Factor) at the resonant frequency, and outputs a signal that is delayed in phase by 90 degrees from the oscillation signal at the resonant frequency.

[0013] If the frequency (oscillation frequency) of the output signal of the oscillator 200 deviates from the resonant frequency of the resonant element 300, the phase delay in the resonant element 300 deviates from 90 degrees. In this specification, this deviation component is called a phase error, and the phase error signal obtained by Laplace transforming this phase error is denoted as θe(s). If the signal obtained by Laplace transforming the phase of the output signal of the oscillator 200 (hereinafter referred to as the phase signal) is denoted as θ(s), the phase signal obtained by Laplace transforming the phase of the output signal of the resonant element 300 is θ(s)-90° / s+θe(s).

[0014] The phase detector 400 detects the phase difference between the phase of the output signal of the oscillator 200 and the phase of the output signal of the resonant element 300. When the difference between the phase signal θ(s) of the oscillator 200 and the phase signal θ(s)-90° / s+θe(s) of the resonant element 300 is taken, the phase difference becomes -90° / s+θe(s). When an oscillation signal with a phase shift of 90 degrees is generated in advance from the oscillator 200 and input to the phase detector 400, the phase difference becomes θe(s).

[0015] The control unit 500 generates a first control signal 500 by performing proportional control (P control) and integral control (I control) according to the phase difference detected by, for example, the phase detector 400. The control unit 500 can be configured with a filter having a proportional term P and an integral term I. The filter of the control unit 500 can be expressed as P+I / s in Laplace notation.

[0016] Oscillator 200 generates an oscillation signal having a frequency obtained by multiplying a first control signal generated from the output of control unit 500 by a frequency conversion coefficient K. Frequency conversion coefficient K is a coefficient unique to oscillator 200. In Fig. 2 and other figures, the output signal of oscillator 200 is expressed as a phase, and oscillator 200 is expressed as K / s because the phase is obtained by integrating the frequency.

[0017] 2, the output signal θ(s) of oscillator 200 can be calculated by multiplying the phase error signal θe(s), the filter P+I / s of control unit 500, and K / s of oscillator 200. That is, the output signal θ(s) of oscillator 200 is expressed by the following equation (1).

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[0018] The oscillation frequency of the oscillator 200 can be obtained by differentiating the phase θ(s), and can be expressed as sθ(s) in Laplace notation by multiplying it by s. r (t) changes depending on the time change of the environment. Resonance frequency ω r (t) is expressed as ω in Laplace notation. r It can be expressed as (s).

[0019] When the oscillation frequency of the oscillator 200 is close to the resonant frequency of the resonant element 300, the phase characteristic can be linearly approximated near the resonant frequency of the resonant element 300. If the phase gradient at the resonant frequency of the resonant element 300 is a, the phase error θe(s) is the difference sθ(s)-ω between the oscillation frequency of the oscillator 200 and the resonant frequency of the resonant element 300. r The phase error θe(s) can be expressed as a value obtained by multiplying (s) by a coefficient a. That is, the phase error θe(s) is expressed by the following equation (2).

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[0020] From equations (1) and (2), the output signal θ(s) of the oscillator 200 is expressed by the following equation (3).

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[0021] From equation (3), the frequency error sθ(s)-ω between the oscillation frequency of the oscillator 200 and the resonant frequency of the resonant element 300 is r (s) is expressed by the following equation (4).

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[0022] As described above, when the resonant frequency of the resonant element 300 changes over time, the oscillation frequency of the oscillator 200 cannot follow the change in the resonant frequency, and a frequency error shown in equation (4) occurs.

[0023] 1 is characterized by reducing the frequency error shown in equation (4) to zero. The phase locked loop 1 includes a first oscillator 21, a second oscillator 22, a resonant element 3, a first phase detector 41, a control unit 5, and a first auxiliary signal generator 61.

[0024] 2, the first oscillator 21 varies the frequency in response to a first control signal generated from the output of the control unit 5. Specifically, the first oscillator 21 generates an oscillation signal having a frequency obtained by multiplying the first control signal by a specific frequency conversion coefficient (first conversion coefficient) K1.

[0025] The second oscillator 22 varies the frequency in response to a second control signal, which will be described later. Specifically, the second oscillator 22 generates an oscillation signal having a frequency obtained by multiplying the second control signal by a specific frequency conversion coefficient (second conversion coefficient) K2.

[0026] Similar to the resonant element 300 in FIG. 2, the resonant element 3 resonates at a predetermined resonant frequency and outputs a signal whose phase is shifted by 90 degrees from the output signal of the first oscillator 21 at the resonant frequency.

[0027] The first phase detector 41 is configured by, for example, an adder. The first phase detector 41 detects a phase difference (first phase error) between the phase of the output signal of the resonant element 3 and the phase of the output signal of the second oscillator 22. The first phase detector 41 inputs the first phase error signal to the control unit 5 and the first auxiliary signal generator 61.

[0028] The control unit 5 generates a first signal that includes at least a proportional component of the first phase error signal. The first control signal is a signal that corresponds to the first signal.

[0029] The first auxiliary signal generator 61 generates a second signal proportional to at least the differential component of the first phase error signal.

[0030] The second control signal is a signal corresponding to the first signal and the second signal. The second control signal is generated, for example, by a first phase corrector 71. The first phase corrector 71 is inserted between the input node of the second oscillator 22 and the output node of the control unit 5 and the output node of the first auxiliary signal generator 61. The first phase corrector 71 combines the first signal and the second signal to generate the second control signal.

[0031] The output signals of the first oscillator 21 and the second oscillator 22 are ideally oscillation signals that are 90 degrees out of phase with the output signal of the resonator element 3. If the phase of the output signal of the first oscillator 21 is θ1(s), then, as in equation (2), the phase difference between the first oscillator 21 and the resonator element 3 is −90° / s+a(sθ1(s)−ω r (s)). That is, the phase signal of the resonator element 3 can be expressed as θ1(s)-90° / s+a(sθ1(s)-ω r (s)) where the coefficient a indicates the phase gradient at the resonant frequency of the resonant element 3.

[0032] The first phase error θe1(s) output from the first phase detector 41 is the phase difference between the phase signal of the resonant element 3 and the phase signal of the second oscillator 22. When the phase signal of the second oscillator 22 is θ2(s) and an oscillation signal with a phase shift of 90 degrees is generated in advance from the second oscillator 22 and input to the first phase detector 41, the first phase error θe1(s) output from the first phase detector 41 is expressed by the following equation (5).

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[0033] When the transfer function of the control unit 5 is F(s), the phase signal θ1(s) of the first oscillator 21 is expressed by the following equation (6).

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[0034] When the transfer function of the first auxiliary signal generator 61 is represented by A(s), the second control signal output from the first phase corrector 71 can be represented by F(s)+A(s). As a result, the phase signal θ2(s) of the second oscillator 22 is expressed by the following equation (7).

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[0035] From equations (5), (6), and (7), the oscillation frequency sθ1(s) of the first oscillator 21 is expressed by the following equation (8).

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[0036] Here, the transfer function A(s) of the first auxiliary signal generator 61 is set as shown in equation (9) so that the relationship F(s)(K2-K1)+A(s)K2=-s holds. When the transfer function A(s) of equation (9) is applied to equation (8), the result of equation (10) is obtained. As can be seen from equation (10), the oscillation frequency sθ1(s) of the first oscillator 21 can be made to follow the resonant frequency ωr(s) of the resonant element 3.

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[0037] 1 includes the second oscillator 22 and the first auxiliary signal generator 61, the oscillation frequency of the first oscillator 21 can be changed with good tracking ability even if the resonance frequency of the resonance element 3 varies depending on the environment, such as temperature. In particular, according to this embodiment, the oscillation frequency can be made to track the resonance frequency with good accuracy without externally inputting environmental information, etc. Specifically, the oscillation frequency of the first oscillator 21 can be made to track the resonance frequency by setting the transfer function A(s) of the first auxiliary signal generator 61 as shown in Equation (9).

[0038] Furthermore, as shown in equation (9), the characteristics of the first auxiliary signal generator 61 are determined from the transfer function F(s) of the control unit 5 and the frequency conversion coefficients K1 and K2 of the first oscillator 21 and the second oscillator 22. Therefore, the characteristics of the first auxiliary signal generator 61 can be set regardless of the characteristics of the resonant element 3 or environmental information such as temperature characteristics.

[0039] (Second embodiment) The frequency conversion coefficient K1 of the first oscillator 21 and the frequency conversion coefficient K2 of the second oscillator 22 may be set to be approximately equal. Fig. 3 is a block diagram of a phase locked loop 1a in the second embodiment. In Fig. 3, K1 = K2 = K0. As a result, the transfer function A(s) of the first auxiliary signal generator 61 shown in equation (9) can be expressed as in equation (11).

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[0040] As shown in equation (11), the transfer function A(s) of the first auxiliary signal generator 61 does not depend on the transfer function F(s) of the control unit 5, and can be simplified to have only differential characteristics.

[0041] In the second embodiment, the transfer function F(s) of the control unit 5 can be set arbitrarily. FIG. 4 is a block diagram of the phase locked loop 1b in the second embodiment when the control unit 5 performs proportional control and integral control. For example, the transfer function F(s) of the control unit 5 can be realized by proportional control (also referred to as P control) and integral control (also referred to as I control) according to the first phase error detected by the first phase detector 41, as shown in FIG. 4. Therefore, the control unit 5 can be configured with a filter having a proportional term P and an integral term I.

[0042] As described above, in the second embodiment, the frequency conversion coefficients K1 and K2 of the first oscillator 21 and the second oscillator 22 are made to be approximately the same. As a result, the transfer function A(s) of the first auxiliary signal generator 61 does not depend on the transfer function F(s) of the control unit 5, as shown in equation (11). Therefore, the phase locked loop circuits 1a and 1b can make the oscillation frequency of the first oscillator 21 follow the resonant frequency without depending on the transfer function F(s) of the control unit 5.

[0043] (Third embodiment) One or more auxiliary signal generators may be provided in addition to the first auxiliary signal generator 61. For example, a second auxiliary signal generator may be further provided to receive the first phase error signal detected by the first phase detector 41, and the first control signal for the first oscillator 21 may be generated from the sum of the output of the second auxiliary signal generator and the output of the control unit 5.

[0044] 5 is a block diagram of a phase locked loop 1c according to the third embodiment. The phase locked loop 1c includes a second auxiliary signal generator 62 and a second phase corrector 72 in addition to the configuration of the phase locked loop 1 in FIG.

[0045] The second auxiliary signal generator 62 receives the first phase error signal from the first phase detector 41. The second auxiliary signal generator 62 generates a third signal proportional to at least the differential component of the first phase error signal.

[0046] The second phase corrector 72 is inserted between the first oscillator 21 and the control unit 5 and second auxiliary signal generator 62. The second phase corrector 72 combines the first signal and the third signal to generate the first control signal.

[0047] When the transfer function of the second auxiliary signal generator 62 is B(s), the phase signal θ1(s) of the first oscillator 21 in the third embodiment is expressed by the following equation (12).

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[0048] From equations (5), (7), and (12), sθ1(s) is expressed by the following equation (13).

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[0049] From equation (13), the transfer function A(s) of the first auxiliary signal generator 61 and the transfer function B(s) of the second auxiliary signal generator 62 can be set so that the relationship A(s)K2-B(s)K1=-s+F(s)(K1-K2) holds. As a result, the relationship of equation (10) also holds in the phase locked loop 1c, and the oscillation frequency of the first oscillator 21 can be made to follow the resonant frequency.

[0050] The frequency conversion coefficient K1 of the first oscillator 21 and the frequency conversion coefficient K2 of the second oscillator 22 can be set to K1=K2=K0. As a result, regardless of the transfer function F(s) of the control unit 5, the difference between the transfer function A(s) of the first auxiliary signal generator 61 and the transfer function B(s) of the second auxiliary signal generator 62 can be simplified as shown in equation (14).

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[0051] In this way, even when one or more auxiliary signal generators are provided in addition to the first auxiliary signal generator 61, it is possible to make the oscillation frequency of the first oscillator 21 follow the resonance frequency, as in the first embodiment. Also, as in the second embodiment, by making the frequency conversion coefficients K1, K2 of the first oscillator 21 and the second oscillator 22 approximately equal, the transfer function A(s) of the first auxiliary signal generator 61 and the transfer function B(s) of the second auxiliary signal generator 62 become independent of the transfer function F(s) of the control unit 5.

[0052] (Fourth embodiment) In the first embodiment, the first phase detector 41 is configured with an adder, but the configuration of the first phase detector 41 is not limited to an adder. For example, the first phase detector 41 may be configured with a multiplier and a low-pass filter.

[0053] 6 is a block diagram of a phase locked loop circuit 1d according to the fourth embodiment. A first phase detector 41a in FIG.

[0054] Multiplier 42 outputs the multiplication result of the output signal of resonator element 3 and the output signal of second oscillator 22. Low-pass filter 43 extracts frequency components lower than a predetermined cutoff frequency from the output signal of multiplier 42.

[0055] The phase of the first oscillator 21 is delayed by 90 degrees relative to the phase of the resonant element 3 resonating at the resonant frequency, resulting in a phase error θE(t). The phase error θE(t) can be linearly approximated near the resonant frequency of the resonant element 3. That is, the coefficient a, the output frequency θ1(t) of the first oscillator 21, and the resonant frequency ω of the resonant element 3 are r Using (t), it can be expressed by the following equation (15).

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[0056] When the output signal of the first oscillator 21 is cos θ1(t), the output signal ω of the resonant element 3 is expressed by the following equation (16).

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[0057] When the output signal cos θ2(t) of the second oscillator 22 is multiplied by the output signal of the resonator element 3ω by the multiplier 42, a signal expressed by the following equation (17) is generated.

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[0058] When the output signal of the multiplier 42 is input to a low-pass filter 43, an output signal θe1(t) of the first phase detector 41a shown in the following equation (18) is obtained.

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[0059] The output signal θe1(s) of the first phase detector 41a shown in equation (18) is doubled and then subjected to Laplace transform, which corresponds to the first phase error θe1(s) shown in equation (5).

[0060] As described above, in the fourth embodiment, the first phase detector 41a is configured with the multiplier 42 and the low-pass filter 43. In this case, as in the case where the first phase detector 41 configured with an adder is used, the oscillation frequency can be made to follow the resonance frequency with high accuracy without inputting environmental information or the like from outside.

[0061] (Fifth embodiment) In the fifth embodiment, the first phase detector 41 may detect the phase difference between the first and second oscillation signals and the output signal of the resonant element 3, which are out of phase with each other by 90 degrees.

[0062] 7 is a block diagram of a phase locked loop circuit 1e according to the fifth embodiment. A first phase detector 41b in FIG.

[0063] The second oscillator 22 generates a first oscillation signal and a second oscillation signal having mutually different phases. The multiplier 42 generates a first multiplied signal I by multiplying the first oscillation signal by the output signal of the resonant element 3, and generates a second multiplied signal Q by multiplying the second oscillation signal by the output signal of the resonant element 3. The phase difference calculation unit 44 detects the phase difference between the low-frequency component signal of the first multiplied signal I and the low-frequency component signal of the second multiplied signal Q, among the output signals of the low-pass filter 43.

[0064] The first oscillator 21 in FIG. 7 supplies an oscillation signal expressed as cos θ1(t) to the resonator element 3. Furthermore, the multiplier 42 in the first phase detector 41b multiplies the output signal of the resonator element 3 by the first oscillation signal and the second oscillation signal (2 sin θ2(t), -2 cos θ2(t)) supplied from the second oscillator 22, respectively, to generate a first multiplied signal I and a second multiplied signal Q. The first multiplied signal I and the second multiplied signal Q can be expressed by the following equations (19) and (20) using the output signal ω of the resonator element 3. Note that the output signal ω of the resonator element 3 can be expressed by equation (16), similarly to the fourth embodiment.

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[0065] The low-pass filter 43 in the first phase detector 41b filters the low-frequency component signal I included in the first multiplied signal I. L and the low-frequency component signal Q included in the second multiplication signal Q. L Extract the low frequency component signal I L , Q L can be expressed by the following equations (21) and (22) using θe1(t) in equation (18).

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[0066] The phase difference calculation unit 44 calculates the low-frequency component signal I L and low frequency component signal Q L The angle ∠I L Q L The phase difference is calculated by:

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[0067] As shown in equation (23), the phase difference calculation unit 44 can output the output signal θe1(t) of the first phase detector 41b.

[0068] In this way, even when the second oscillator 22 supplies the first phase detector 41b with a first oscillation signal and a second oscillation signal that are 90 degrees out of phase with each other, by using the multiplier 42, the low-pass filter 43, and the phase difference calculation unit 44, the oscillation frequency can be made to accurately track the resonant frequency from the first phase detector 41b without inputting environmental information or the like from outside, as in the first to fourth embodiments.

[0069] (Sixth embodiment) In the phase locked loop circuits 1, 1a, 1b, 1c, 1d, and 1e according to the first to fifth embodiments, each circuit element is configured as an analog circuit. In the sixth embodiment, some of the circuit elements are configured as digital circuits. By using digital signals for each control signal, it is possible to improve resistance to environmental influences such as temperature.

[0070] Fig. 8 is a block diagram of a phase locked loop 1f according to the sixth embodiment. The phase locked loop 1f includes a DA (Digital to Analog) converter 81 and an AD (Analog to Digital) converter 82. The first oscillator 21, the second oscillator 22, the first phase detector 41, the control unit 5, and the first auxiliary signal generator 61 in Fig. 8 are configured as digital circuits, and the resonant element 3 is configured as an analog circuit.

[0071] The DA converter 81 is inserted between the output node of the first oscillator 21 and the input node of the resonator element 3. The DA converter 81 converts the output signal of the first oscillator 21 into an analog signal and inputs it to the resonator element 3.

[0072] The AD converter 82 is inserted between the output node of the resonator element 3 and the input node of the first phase detector 41. The DA converter 81 converts the output signal of the resonator element 3 into a digital signal and inputs it to the first phase detector 41.

[0073] In the phase-locked loop 1f, the first oscillator 21 and the second oscillator 22 are configured as digital circuits, so the frequency conversion coefficients K1 and K2 do not fluctuate depending on environmental information such as temperature and power supply voltage. Therefore, even if the resonant frequency of the resonant element 3 changes over time due to environmental changes, the oscillation frequency of the first oscillator 21 can be changed to follow the resonant frequency with good tracking ability.

[0074] As described above, the phase locked loop 1f in the sixth embodiment includes the DA converter 81 and the AD converter 82, and is configured as digital circuits for the first oscillator 21, the second oscillator 22, the first phase detector 41, the control unit 5, and the first auxiliary signal generator 61. As a result, even if the resonant frequency of the resonant element 3 fluctuates due to environmental factors such as temperature, the oscillation frequency of the first oscillator 21 can be changed with good follow-up to the fluctuation.

[0075] (Seventh embodiment) Various configurations can be used for the first auxiliary signal generator 61. For example, the differential characteristics of the first auxiliary signal generator 61 may be simulated by a high-pass filter or a band-pass filter.

[0076] 9A is a block diagram of a phase locked loop 1g according to the seventh embodiment. A first auxiliary signal generator 61a in FIG.

[0077] The filter 63 is, for example, a high-pass filter. The first phase detector 41 inputs the first phase error signal to the filter 63. The filter 63 exhibits a characteristic in which the output increases with frequency at frequencies lower than a predetermined cutoff frequency of the first phase error θe1(s). Because the filter 63 exhibits a differential characteristic at frequencies lower than the cutoff frequency, the differential characteristic can be simulated by a high-pass filter. By using the high-pass characteristic of the filter 63 lower than the cutoff frequency, the differential characteristic of the first auxiliary signal generator 61 can be realized in the first auxiliary signal generator 61a as well. As a result, even if the resonant frequency of the resonant element 3 fluctuates due to environmental factors such as temperature, the oscillation frequency of the first oscillator 21 can be changed with good tracking ability to accommodate the fluctuation. The filter 63 may be a band-pass filter. Even in the case of a band-pass filter, the differential characteristic can be simulated at frequencies lower than the lower cutoff frequency.

[0078] 9B shows an example in which a phase locked loop 1h according to the seventh embodiment uses a first phase detector 41a including a multiplier 42 and a low-pass filter 43, as in the fourth embodiment. In this case, the filter 63 has a higher cutoff frequency than the low-pass filter 43.

[0079] In this way, in the seventh embodiment, by configuring the filter 63 with a high-pass filter or a band-pass filter, it is possible to prevent high-frequency noise components contained in the first phase error θe1(s) detected by the first phase detector 41 from being amplified in the first auxiliary signal generator 61a.

[0080] (Eighth embodiment) The phase locked loop circuits 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, and 1h according to the first to seventh embodiments can be incorporated into a sensing device that detects a physical quantity. The physical quantity is, for example, a signal to be detected by various sensors, such as an angle, acceleration, or gas concentration. The sensing device may detect the physical quantity based on the output signal of the resonant element 3, or may detect the physical quantity based on the output signal of the first oscillator 21 or the first control signal.

[0081] 10A is a block diagram of a sensing device 10 according to the eighth embodiment. The sensing device 10 in FIG. 10A includes a phase locked loop 1f and a physical quantity calculation unit 9. The physical quantity calculation unit 9 includes a second phase detector 91 and a calculation unit 92.

[0082] 10A may be, for example, an angle sensor. For example, when the resonant element 3 in the phase locked loop 1 is a MEMS resonant element, the sensing device 10 can be applied to an angle sensor.

[0083] The resonant element 3 in the eighth embodiment vibrates in two-dimensional directions at a predetermined resonant frequency, and outputs a displacement signal in the x direction (first direction) and a displacement signal in the y direction (second direction).

[0084] 10B is a block diagram showing an example of the configuration of the second phase detector 91. The second phase detector 91 includes a multiplier 93 and a low-pass filter 94.

[0085] The second phase detector 91 is used to detect the phase difference between the output signal of the first oscillator 21 and the output signal of the resonator element 3. Specifically, the second phase detector 91 detects, as the second phase error, the low-frequency component of the signal obtained by multiplying the output signal of the first oscillator 21 by the displacement signal of the resonator element 3 in the x direction, and the low-frequency component of the signal obtained by multiplying the output signal of the first oscillator 21 by the displacement signal of the resonator element 3 in the y direction.

[0086] The calculation unit 92 calculates a physical quantity based on the second phase error detected by the second phase detector 91. In the eighth embodiment, the calculation is performed on an angle, for example, as the physical quantity.

[0087] The MEMS resonant element vibrates a mass in an elliptical shape, with the major axis of the ellipse being d and the minor axis being q. The displacement signal in the x direction of the MEMS resonant element is expressed by equation (24), and the displacement signal in the y direction is expressed by equation (25).

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[0088] Here, θe2(t) is the output θe2(t) of the second phase detector 91. The output θe2(t) of the second phase detector 91 is Laplace transformed to become θe2(s), which is calculated as follows:

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[0089] The multiplier 93 in the second phase detector 91 multiplies the x-direction displacement signal and the y-direction displacement signal input from the resonator element 3 by the oscillation signal (2 sin θ1(t), −2 cos θ1(t)) input from the first oscillator 21 to obtain I x Signal and Q x signal and I shown in equations (28) and (29) y Signal and Q y and generate a signal.

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[0090] The low-pass filter 94 in the second phase detector 91 is x Signal, Q x Signal, I y Signal, Q y Low frequency component of the signal I xL , Q xL , I yL , Q yL The output signal I of the low-pass filter 94 is extracted. xL , Q xL , I yL , Q yL is input to the calculation unit 92. The calculation unit 92 calculates the angle θ based on the following equation (30): A Find (t).

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[0091] 10A shows an example in which the phase locked loop 1f shown in the fifth embodiment is applied to a sensing device 10. The phase locked loop 1f includes a DA converter 81 and an AD converter 82. As a result, the first oscillator 21, the second oscillator 22, the first phase detector 41, the control unit 5, the first auxiliary signal generator 61, the first phase corrector 71, and the physical quantity calculation unit 9 can all be configured with digital circuits. On the other hand, the resonant element 3 is configured with an analog circuit.

[0092] The DA converter 81 is inserted between the physical quantity calculation unit 9 and the resonant element 3, and converts the output signal of the first oscillator 21 into an analog signal. The AD converter 82 is inserted between the resonant element 3 and the physical quantity calculation unit 9, and converts the output signal of the resonant element 3 into a digital signal.

[0093] By configuring the first oscillator 21, the second oscillator 22, the first phase detector 41, the control unit 5, the first auxiliary signal generator 61, and the first phase corrector 71 as digital circuits, it is possible to suppress fluctuations in the frequency conversion coefficients K1 and K2 of the first oscillator 21 and the second oscillator 22 due to temperature, power supply voltage, etc. Therefore, even if the resonant frequency of the resonant element 3 changes over time due to environmental changes such as temperature and power supply voltage, it is possible to vary the oscillation frequency of the first oscillator 21 to accurately follow the resonant frequency of the resonant element 3.

[0094] Furthermore, since the physical quantity calculation unit 9 can be configured with a digital circuit, it is less susceptible to environmental influences such as temperature and power supply voltage, and can detect physical quantities more accurately than when configured with an analog circuit.

[0095] The DA converter 81 and the AD converter 82 may be omitted from the sensing device 10. In addition to the phase locked loop circuit 1f, any of the phase locked loop circuits 1, 1a, 1b, 1c, 1d, 1e, 1g, and 1h may be applied to the sensing device 10, or an appropriate combination of the circuit elements of these phase locked loop circuits may be applied.

[0096] In this way, the phase locked loop circuits 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, and 1h can be applied to the sensing device 10. Even if the resonant frequency of the resonant element 3 changes over time due to a time change in environmental information, the phase locked loop circuits 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, and 1h can make the oscillation frequency of the first oscillator 21 accurately follow the resonant frequency of the resonant element 3. This makes it possible to suppress a decrease in the detection accuracy of a physical quantity (e.g., angle) of the sensing device 10.

[0097] (Ninth embodiment) The sensing device 10 can have various configurations. For example, the configuration of the sensing device 10 may be changed to be applicable to different sensors.

[0098] 11 is a block diagram of a sensing device 10a according to the ninth embodiment. The sensing device 10a includes a phase-locked loop 1 and a physical quantity calculation unit 9a. The physical quantity calculation unit 9a includes a frequency detector 96, a frequency error detector 97, and a calculation unit 92. As in the eighth embodiment, the DA converter 81 and AD converter 82 in FIG. 11 may be omitted.

[0099] The sensing device 10a may be, for example, an acceleration sensor. For example, when the resonant element 3 in the phase locked loop 1 is a MEMS resonant element, the sensing device 10a can be applied to an acceleration sensor.

[0100] The frequency detector 96 detects the oscillation frequency of the first oscillator 21. The frequency error detector 97 calculates the frequency error between the oscillation frequency detected by the frequency detector 96 and a predetermined reference frequency. The reference frequency is, for example, the oscillation frequency of the first oscillator 21 when the acceleration of the resonant element 3 is set to zero.

[0101] The calculation unit 92 detects a physical quantity based on the frequency error calculated by the frequency error detector 97. Specifically, the calculation unit 92 calculates the frequency error calculated by the frequency error detector 97 as an acceleration coefficient K AAcceleration is calculated by dividing by the acceleration coefficient K. A is a value specific to the MEMS resonant element.

[0102] The sensing device 10a may be, for example, a gas sensor. That is, if the resonant element 3 is an MEMS resonant element having a gas-sensitive film, the mass and stress of the resonant element 3 change in response to the gas, causing a change in the resonant frequency. Therefore, the sensing device 10a can be applied to a gas sensor.

[0103] The frequency error detector 97 calculates the frequency error between the oscillation frequency of the first oscillator 21, which follows the resonance frequency detected by the frequency detector 96, and a reference frequency. The reference frequency is the resonance frequency of the resonance element 3 at a predetermined gas concentration. The calculation unit 92 calculates the frequency error calculated by the frequency error detector 97 as a function of the gas concentration coefficient K of the resonance element 3. G The gas concentration is calculated by dividing by the gas concentration coefficient K. G is a value specific to the MEMS resonant element.

[0104] In this way, the sensing device 10a in the ninth embodiment can be applied to, for example, an acceleration sensor or a gas sensor. Even if the resonant frequency of the resonant element 3 changes over time due to environmental changes, the sensing device 10a can detect acceleration (gas concentration) more accurately because the oscillation frequency of the first oscillator 21 changes to accurately follow the resonant frequency.

[0105] (Tenth embodiment) A sensing device 10a in the ninth embodiment inputs an output signal of a first oscillator 21 to a physical quantity calculation unit 9a to calculate a frequency error between the oscillation frequency of the first oscillator 21 and the resonant frequency of the resonant element 3. The first control signal of the first oscillator 21 may be used to calculate the frequency error.

[0106] Fig. 12 is a block diagram of a sensing device 10b according to the tenth embodiment. The sensing device 10b includes a phase-locked loop 1 and a physical quantity calculation unit 9b. The physical quantity calculation unit 9b includes a frequency multiplier 98, a frequency error detector 97, and a calculation unit 92. As in the eighth embodiment, the DA converter 81 and AD converter 82 in Fig. 12 may be omitted.

[0107] The frequency multiplier 98 multiplies the first control signal by the frequency conversion coefficient K1. This allows the frequency multiplier 98 to generate a frequency signal that represents the same oscillation frequency as the first oscillator 21. In other words, the frequency multiplier 98 has the function of the frequency detector 96 in FIG. 11, and outputs the frequency of the oscillation signal of the first oscillator 21 obtained by multiplying the first control signal by the frequency conversion coefficient K1.

[0108] The frequency error detector 97 calculates the frequency error between the output signal of the frequency multiplier 98 and a predetermined reference frequency. The calculation unit 92 detects a physical quantity based on the frequency error calculated by the frequency error detector 97.

[0109] The sensing device 10b may be, for example, an acceleration sensor. In this case, the processing operations of the frequency error detector 97 and the calculation unit 92 in the physical quantity calculation unit 9b that calculates acceleration are similar to the processing operations of the frequency error detector 97 and the calculation unit 92 in the physical quantity calculation unit 9a. The sensing device 10b can also be used as a gas sensor like the sensing device 10a.

[0110] In this way, the sensing devices 10a and 10b can detect acceleration (gas concentration) based on the output signal of the first oscillator 21, and can also detect acceleration (gas concentration) based on the first control signal of the first oscillator 21.

[0111] In either case, even if the resonant frequency of the resonant element 3 changes over time due to changes in environmental conditions such as temperature, the oscillation frequency of the first oscillator 21 can be changed with good tracking ability, allowing acceleration (gas concentration) to be detected more accurately.

[0112] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, configurations in which some components are omitted from all the components shown in each embodiment may also be considered. Furthermore, components described in different embodiments may be appropriately combined.

[0113] [Note] [Item 1] a first oscillator that varies the frequency in response to a first control signal; a resonant element that resonates at a predetermined resonant frequency and outputs a signal that is 90 degrees out of phase with the output signal of the first oscillator at the resonant frequency; a second oscillator that varies the frequency in response to a second control signal; a first phase detector that detects a first phase error between the output signal of the resonator element and the output signal of the second oscillator; a control unit that generates a first signal including at least a proportional component of the first phase error; a first auxiliary signal generator that generates a second signal proportional to at least a differential component of the first phase error; the first control signal is a signal corresponding to the first signal, the second control signal is a signal corresponding to the first signal and the second signal; Phase synchronized circuit. [Item 2] further comprising a first phase corrector that combines the first signal and the second signal to generate the second control signal; Item 1. The phase locked loop circuit according to item 1. [Item 3] a first conversion factor by which the first oscillator converts the first control signal to the output signal of the first oscillator is equal to a second conversion factor by which the second oscillator converts the second control signal to the output signal of the second oscillator; 3. The phase locked loop circuit according to item 1 or 2. [Item 4] the first phase detector includes an adder that detects the first phase error; Item 3. A phase locked loop circuit according to any one of items 1 to 3. [Item 5] the first phase detector includes a multiplier that multiplies the output signal of the resonator element by the output signal of the second oscillator; a low-pass filter that extracts a low frequency component of the output signal of the multiplier as the first phase error. Item 3. A phase locked loop circuit according to any one of items 1 to 3. [Item 6] the second oscillator outputs a first oscillation signal and a second oscillation signal that are out of phase with each other; the multiplier generates a first multiplied signal by multiplying the output signal of the resonator element by the first oscillation signal, and generates a second multiplied signal by multiplying the output signal of the resonator element by the second oscillation signal; the low-pass filter extracts a low-frequency component signal of the first product signal and a low-frequency component signal of the second product signal; the first phase detector further includes a phase difference calculation unit that detects a phase difference between a low-frequency component signal of the first product signal and a low-frequency component signal of the second product signal. Item 6. The phase locked loop circuit according to item 5. [Item 7] the first auxiliary signal generator comprises a high-pass filter or a band-pass filter; 7. A phase locked loop circuit according to any one of items 1 to 6. [Item 8] a second auxiliary signal generator that generates a third signal proportional to at least a differential component of the first phase error; a second phase corrector that combines the first signal and the third signal to generate the first control signal; Item 4: A phase locked loop circuit according to any one of items 1 to 4. [Item 9] a DA converter inserted between the first oscillator and the resonant element to convert an output signal of the first oscillator into an analog signal; an AD converter inserted between the resonant element and the first phase detector to convert an output signal of the resonant element into a digital signal, Item 9. A phase locked loop circuit according to any one of items 1 to 8. [Item 10] The resonant element is a MEMS (Micro Electro Mechanical Systems) resonant element that vibrates at the resonant frequency. 10. The phase locked loop circuit according to any one of items 1 to 9. [Item 11] A phase locked loop circuit according to any one of items 1 to 10; a physical quantity calculation unit that calculates a physical quantity based on at least one of the output signal of the resonant element, the output signal of the first oscillator, or the first control signal, Sensing device. [Item 12] the resonant element vibrates in two-dimensional directions at the resonant frequency to output a displacement signal in a first direction and a displacement signal in a second direction; The physical quantity calculation unit a second phase detector that detects, as a second phase error, a low frequency component of a signal obtained by multiplying the output signal of the first oscillator by the displacement signal in the first direction and a low frequency component of a signal obtained by multiplying the output signal of the first oscillator by the displacement signal in the second direction; a calculation unit that calculates the physical quantity based on the second phase error detected by the second phase detector, The physical quantity includes an angle. Item 12. The sensing device according to item 11. [Item 13] the physical quantity calculation unit includes a frequency detector that detects the frequency of the output signal of the first oscillator; a frequency error detector that detects a frequency error between the frequency detected by the frequency detector and a predetermined reference frequency; a calculation unit that detects the physical quantity based on the frequency error, Item 12. The sensing device according to item 11. [Item 14] the first oscillator has a first conversion factor that converts the first control signal to an output signal of the first oscillator; The physical quantity calculation unit a frequency multiplier that multiplies the first control signal by the first conversion factor of the first oscillator; a frequency error detector that detects a frequency error between an output signal of the frequency multiplier and a predetermined reference frequency, and a calculation unit that detects the physical quantity based on the frequency error. Item 12. The sensing device according to item 11. [Item 15] the resonant element has a characteristic acceleration coefficient; the calculation unit detects the acceleration by dividing the frequency error by the acceleration coefficient. Item 15. The sensing device according to item 13 or 14. [Item 16] the resonant element has a characteristic gas concentration coefficient; the calculation unit detects the gas concentration by dividing the frequency error by the gas concentration coefficient. Item 15. The sensing device according to item 13 or 14. [Explanation of symbols]

[0114] 1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 100 phase locked loop circuit, 200 oscillator, 3, 300 resonant element, 400 phase detector, 5, 500 control unit, 9, 9a, 9b physical quantity calculation unit, 10, 10a, 10b sensing device, 21 first oscillator, 22 second oscillator, 41, 41a, 41b first phase detector, 42, 93 multiplier, 43, 94 low-pass filter, 44 phase difference calculation unit, 61, 61a first auxiliary signal generator, 62 second auxiliary signal generator, 63 filter, 71 first phase corrector, 72 second phase corrector, 81 DA converter, 82 AD converter, 91 second phase detector, 92 calculation unit, 96 frequency detector, 97 frequency error detector, 98 frequency multiplier

Claims

1. a first oscillator that varies the frequency in response to a first control signal; a resonant element that resonates at a predetermined resonant frequency and outputs a signal that is synchronized with the output signal of the first oscillator by shifting the phase of the signal by 90 degrees at the resonant frequency; a second oscillator that varies the frequency in response to a second control signal; a first phase detector for detecting a first phase error between the output signal of the resonator element and the output signal of the second oscillator; a control unit having a first transfer function and multiplying the first transfer function by the first phase error to generate a first signal that is the first control signal; a first auxiliary signal generator having a second transfer function and multiplying the second transfer function by the first phase error to generate a second signal; a first phase corrector that combines the first signal and the second signal to generate the second control signal; the first transfer function and the second transfer function are set so that an oscillation frequency of the first oscillator follows an oscillation frequency of the second oscillator; the first oscillator outputs a signal obtained by multiplying the first control signal by a first conversion coefficient; the second oscillator outputs a signal obtained by multiplying the second control signal by a second conversion coefficient; When an arbitrary point on a complex plane is s, the first conversion coefficient is K 1 , the second conversion coefficient is K 2 , the first transfer function which is a Laplace transformed function is F(s), and the second transfer function which is a Laplace transformed function is A(s), the first auxiliary signal generator sets the second transfer function to satisfy the relationship F(s)(K 2 −K 1 )+A(s)K 2 =−s; Phase synchronized circuit.

2. the first phase detector includes a multiplier that multiplies the output signal of the resonator element by the output signal of the second oscillator; a low-pass filter that extracts a low frequency component of the output signal of the multiplier as the first phase error.

2. The phase locked loop circuit according to claim 1.

3. the second oscillator outputs a first oscillation signal and a second oscillation signal that are out of phase with each other; the multiplier generates a first multiplied signal by multiplying the output signal of the resonator element by the first oscillation signal, and generates a second multiplied signal by multiplying the output signal of the resonator element by the second oscillation signal; the low-pass filter extracts a low-frequency component signal of the first product signal and a low-frequency component signal of the second product signal; the first phase detector further includes a phase difference calculation unit that detects a phase difference between a low-frequency component signal of the first product signal and a low-frequency component signal of the second product signal.

3. The phase locked loop circuit according to claim 2.

4. the first auxiliary signal generator comprises a high-pass filter or a band-pass filter; 2. The phase locked loop circuit according to claim 1.

5. A first oscillator that varies the frequency in response to a first control signal; a resonant element that resonates at a predetermined resonant frequency and outputs a signal that is synchronized with the output signal of the first oscillator by shifting the phase of the signal by 90 degrees at the resonant frequency; a second oscillator that varies the frequency in response to a second control signal; a first phase detector for detecting a first phase error between the output signal of the resonator element and the output signal of the second oscillator; a control unit having a first transfer function and multiplying the first transfer function by the first phase error to generate a first signal; a first auxiliary signal generator having a second transfer function and multiplying the second transfer function by the first phase error to generate a second signal; a first phase corrector that combines the first signal and the second signal to generate the second control signal; a second auxiliary signal generator having a third transfer function and multiplying the third transfer function by the first phase error to generate a third signal; a second phase corrector that generates a first control signal by combining the first signal and the third signal generated by the control unit, the first transfer function and the second transfer function are set so that an oscillation frequency of the first oscillator follows an oscillation frequency of the second oscillator; the first oscillator varies the frequency in response to the first control signal; the first oscillator outputs a signal obtained by multiplying the first control signal by a first conversion coefficient; the second oscillator outputs a signal obtained by multiplying the second control signal by a second conversion coefficient; Let s be an arbitrary point on the complex plane, and let K be the first conversion coefficient. １ , the second conversion coefficient is K ２ When the first transfer function, which is a Laplace transformed function, is F(s), the second transfer function, which is a Laplace transformed function, is A(s), and the third transfer function, which is a Laplace transformed function, is B(s), The first auxiliary signal generator and the second auxiliary signal generator are A(s)K 2 -B(s)K 1 = -s + F(s)(K 1 -K 2 The second transfer function and the third transfer function are set so as to satisfy the relationship: Phase synchronized circuit.

6. a first conversion factor by which the first oscillator converts the first control signal to the output signal of the first oscillator is equal to a second conversion factor by which the second oscillator converts the second control signal to the output signal of the second oscillator; 6. The phase locked loop circuit according to claim 1.

7. the first phase detector includes an adder for detecting the first phase error; 6. The phase locked loop circuit according to claim 1.

8. a DA converter inserted between the first oscillator and the resonant element to convert an output signal of the first oscillator into an analog signal; an AD converter inserted between the resonator element and the first phase detector to convert an output signal of the resonator element into a digital signal; 6. The phase locked loop circuit according to claim 1.

9. The resonant element is a MEMS (Micro Electro Mechanical Systems) resonant element that vibrates at the resonant frequency.

6. The phase locked loop circuit according to claim 1.

10. a phase locked loop circuit according to claim 1 or 5; a physical quantity calculation unit that calculates a physical quantity based on at least one of the output signal of the resonant element, the output signal of the first oscillator, and the first control signal, Sensing device.

11. the resonant element vibrates in two-dimensional directions at the resonant frequency to output a displacement signal in a first direction and a displacement signal in a second direction; The physical quantity calculation unit a second phase detector that detects, as a second phase error, a low frequency component of a signal obtained by multiplying the output signal of the first oscillator by the displacement signal in the first direction and a low frequency component of a signal obtained by multiplying the output signal of the first oscillator by the displacement signal in the second direction; a calculation unit that calculates the physical quantity based on the second phase error detected by the second phase detector, The physical quantity includes an angle. The sensing device according to claim 10.

12. the physical quantity calculation unit includes a frequency detector that detects a frequency of the output signal of the first oscillator; a frequency error detector that detects a frequency error between the frequency detected by the frequency detector and a predetermined reference frequency; a calculation unit that detects the physical quantity based on the frequency error, The sensing device according to claim 10.

13. the first oscillator has a first conversion factor that converts the first control signal to an output signal of the first oscillator; The physical quantity calculation unit a frequency multiplier that multiplies the first control signal by the first conversion factor of the first oscillator; a frequency error detector that detects a frequency error between an output signal of the frequency multiplier and a predetermined reference frequency, and a calculation unit that detects the physical quantity based on the frequency error. The sensing device according to claim 10.

14. the resonant element has a characteristic acceleration coefficient or a characteristic gas concentration coefficient; the calculation unit detects acceleration by dividing the frequency error by the acceleration coefficient, or detects gas concentration by dividing the frequency error by the gas concentration coefficient. The sensing device according to claim 13.

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