Piezoelectric vibrator with built-in temperature sensor and reference signal generation device

Abstract

To provide a piezoelectric vibrator with a built-in temperature sensor having a new structure effective for improving frequency temperature characteristics.SOLUTION: The piezoelectric vibrator 10 is provided with an AT-cut crystal vibrating piece 10a, a thermosensor 10b, and a resister 10c connected in series to the thermosensor, and is used by being connected to an external electronic device having a temperature compensation circuit for compensating an oscillation frequency of the crystal vibrating piece according to a predetermined correction formula. The resistor is a resistor having a first resistance value capable of setting the inter-terminal voltage of the temperature sensor to a voltage scheduled by a predetermined correction formula, or a second resistance value smaller than the first resistance value or a third resistance value larger than the first resistance value capable of setting the inter-terminal voltage to a correction voltage corresponding to the individual difference of the piezoelectric vibrator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric vibrator incorporating a temperature sensor such as a thermistor, and a reference signal generating device including the same. [Background technology]

[0002] In recent years, quartz crystal units with built-in temperature sensors, which have an AT-cut quartz crystal element and a temperature sensor (typically a thermistor) built into a single container, have become popular. Typical examples are those with a single-chamber structure and an H-shaped structure. The former is a device in which a quartz crystal resonator element and a temperature sensor are mounted in one chamber and hermetically sealed (see, for example, paragraph 75, Figure 7, etc. of Patent Document 1). The latter is a device in which a first chamber mounting a quartz crystal resonator element and a second chamber mounting a temperature sensor are stacked back to back, with the first chamber being hermetically sealed (see, for example, the abstract, Figure 1, etc. of Patent Document 2).

[0003] Both the single-chamber and H-type oscillators are connected to a chipset (external electronic device) designed for use with this oscillator. The oscillator frequency of the crystal resonator is corrected on the chipset side based on the temperature information detected by the temperature sensor, allowing the desired frequency to be obtained with greater precision. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-70552 [Patent Document 2] Japanese Patent Publication No. 2022-140662 Summary of the Invention [Problem to be solved by the invention]

[0005] The above correction is performed using a predetermined correction formula built into the external electronic device. In order to manufacture this external electronic device inexpensively, it is desirable that the predetermined correction formula be simple. Therefore, a correction formula for an approximation formula that approximates a representative frequency-temperature characteristic among the frequency-temperature characteristics of each of the many quartz crystal units used in combination with the external electronic device is used as the correction formula (see Figures 3(A) and (B) described below). However, because the correction formula is determined based on the typical frequency-temperature characteristics of a quartz crystal unit, there is a problem in that the correction will deviate from the ideal if the quartz crystal unit has frequency-temperature characteristics that deviate from the typical frequency-temperature characteristics due to manufacturing variations, etc. (See Figures 4(A) and (B) below). When using a crystal unit with a built-in temperature sensor as a more accurate reference signal source, such as for Bluetooth (registered trademark) or WLAN (Wireless LAN), it is desirable for the frequency fluctuation to be as small as possible in response to fluctuations in ambient temperature in order to satisfy the frequency deviation stipulated by laws and regulations and communication standards. There is also an increasing demand for use in high-temperature environments where frequency fluctuations become greater. Therefore, there is an increasing need for higher accuracy while maintaining low cost, and a solution to the above problems is desirable. This application has been made in consideration of these points, and therefore, the purpose of this application is to provide a piezoelectric vibrator with a built-in temperature sensor having a novel structure that is effective in improving the frequency-temperature characteristics of a piezoelectric vibrator with a built-in temperature sensor, which comprises a piezoelectric vibrating piece with frequency-temperature characteristics and a temperature sensor, and a reference signal generating device using the same. [Means for solving the problem]

[0006] In order to achieve this object, according to a first aspect of the present application, there is provided a temperature sensor built-in piezoelectric vibrator that includes a piezoelectric vibrating piece having frequency-temperature characteristics and a temperature sensor, and that is used by being connected to an external electronic device that has a temperature compensation circuit that compensates for the oscillation frequency of the piezoelectric vibrating piece in accordance with temperature information detected by the temperature sensor and a predetermined correction formula, wherein: the temperature sensor detects a voltage between its terminals as the temperature information by the external electronic device; The temperature compensation device is characterized in comprising a resistor having one end connected to the temperature sensor and the other end connected to a predetermined power supply of the external electronic device, the resistor having a first resistance value that can make the inter-terminal voltage a voltage expected by the predetermined correction formula, or a second resistance value that is smaller than the first resistance value or a third resistance value that is larger than the first resistance value that can make the inter-terminal voltage a correction voltage according to individual differences of the piezoelectric vibrator. In other words, the first resistance value is a resistance value that can obtain a desired temperature compensation result by a correction formula that is stored in advance in the external electronic device.

[0007] The second and third resistance values ​​are resistance values ​​that can correct the frequency-temperature characteristics of a crystal unit that deviates from the typical frequency-temperature characteristics due to manufacturing variations, etc., in a direction that improves the frequency-temperature characteristics compared to the first resistance value, and are resistance values ​​that are determined in accordance with the frequency-temperature characteristics. The second and third resistance values ​​may be determined for each crystal unit, or may be determined for each group consisting of multiple crystal units with frequency characteristics within a desired range.

[0008] In implementing this invention, the piezoelectric vibrating reed may be any of a variety of types having frequency-temperature characteristics, such as a quartz crystal vibrator, a piezoelectric ceramic vibrator, or a vibrator made of other piezoelectric materials. However, the piezoelectric vibrating reed is preferably an AT-cut quartz crystal vibrating reed. Since AT-cut quartz crystal vibrating reeds are currently and will continue to be widely used as elements for reference signal sources, applying this invention can realize a more useful reference signal source.

[0009] In carrying out the present invention, it is preferable that the piezoelectric vibrator has, as external terminals for connecting to the external electronic device, first and second terminals for the piezoelectric vibrating piece, third and fourth terminals for the temperature sensor and resistor, and a fifth terminal connected to a connection point between the temperature sensor and the resistor. With this configuration, the vibrator of the present invention can be used effectively. In addition, the reference signal generating device of the second invention of this application is characterized by including a piezoelectric vibrator with a built-in temperature sensor according to the first invention, and an external electronic device having a temperature compensation circuit that compensates for the oscillation frequency of the piezoelectric vibrating reed in accordance with temperature information detected by the temperature sensor built into the piezoelectric vibrator and a predetermined correction formula. [Effects of the Invention]

[0010] The piezoelectric resonator with a built-in temperature sensor according to the first aspect of this application further includes a resistor having a first resistance value, a second resistance value, or a third resistance value for setting (correcting) the voltage between the terminals of the temperature sensor. Therefore, an external electronic device (chip set) to which the piezoelectric resonator of this invention is connected inputs the voltage corrected by the resistor as temperature information from the temperature sensor to perform temperature compensation. That is, when the resistor has the first resistance value, the chip set performs compensation using temperature information conforming to a predetermined compensation formula. Furthermore, when the resistor has the second resistance value or the third resistance value, the chip set performs compensation using the predetermined compensation formula using temperature information intentionally deviated from temperature information conforming to the predetermined compensation formula due to the second or third resistance value. Therefore, even in the case of a crystal resonator whose frequency-temperature characteristics deviate from the typical frequency-temperature characteristics due to manufacturing variations or the like, the resistor with the second or second resistance value functions to provide better temperature compensation than when this resistor is not included. Furthermore, the reference signal generating device of the second aspect of the present invention, in combination with the piezoelectric vibrator of the first aspect of the present invention, can generate a reference signal with higher accuracy than conventional ones. Therefore, it is possible to provide a piezoelectric vibrator and a reference signal generator with a built-in temperature sensor, which have a novel structure that is effective in improving the frequency temperature characteristics of the piezoelectric vibrator compared to conventional ones. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a piezoelectric vibrator 10 with a built-in temperature sensor and a reference signal generating device 21 according to an embodiment. [Figure 2]1 is a diagram for deepening understanding of the present invention, and is a diagram for explaining a conventional piezoelectric vibrator 30 with a built-in temperature sensor. FIG. [Figure 3] 3A to 3C are diagrams for explaining the effects of the piezoelectric vibrator 10 according to the embodiment. [Figure 4] 3A and 3B are views continuing from FIG. 3 and illustrating the effects of the piezoelectric vibrator 10 according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a piezoelectric vibrator with a built-in temperature sensor according to the present invention will be described with reference to the drawings. Note that each drawing used for the description is merely a schematic illustration to enable understanding of the present invention. Furthermore, in each drawing used for the description, similar components are designated by the same numbers, and their description may be omitted. Furthermore, the circuit configurations, numerical examples, etc. described in the following description are merely preferred examples within the scope of the present invention. Therefore, the present invention is not limited to the following embodiments.

[0013] 1. Piezoelectric vibrator configuration Fig. 1 is a diagram for explaining a piezoelectric vibrator 10 according to an embodiment. It is a block diagram showing the piezoelectric vibrator 10 together with an external electronic device 20 to which the piezoelectric vibrator 10 is connected. Fig. 2 is a diagram for deepening understanding of the present invention, and is a block diagram showing a conventional piezoelectric vibrator 30 together with an external electronic device 40 to which the piezoelectric vibrator 30 is connected. The piezoelectric vibrator 10 of the embodiment is a temperature sensor-embedded piezoelectric vibrator that includes a piezoelectric vibrating piece 10a having frequency-temperature characteristics and a temperature sensor 10b, and is used by being connected to an external electronic device 20 that has a temperature compensation circuit 20a that compensates for the oscillation frequency of the piezoelectric vibrating piece 10a according to temperature information detected by the temperature sensor 10b and a predetermined correction formula.

[0014] In this embodiment, the piezoelectric vibrating piece 10a provided in the piezoelectric vibrator 10 is an AT-cut quartz crystal vibrating piece. The temperature sensor 10b has a voltage between its terminals that is detected as the temperature information by the external electronic device 20. The temperature sensor 10b can be any suitable sensor, but in this embodiment, the temperature sensor 10b is configured as an NTC (negative temperature coefficient) thermistor. As a feature of the present invention, the piezoelectric vibrator 10 also includes a resistor 10c, one end of which is connected to the temperature sensor 10b and the other end of which is connected to a predetermined power supply 20b of the external electronic device 20. This resistor 10c, as will be described in detail in the section on functions and effects below, is a resistor having a first resistance value that can adjust the inter-terminal voltage of the temperature sensor 10b to a voltage predicted by the predetermined correction formula, or a resistor having a second resistance value smaller than the first resistance value or a third resistance value larger than the first resistance value that can adjust the inter-terminal voltage to a correction voltage corresponding to individual differences in the piezoelectric vibrator. The resistor 10c and the temperature sensor 10b form a series circuit. The terminal of the temperature sensor 10b opposite the terminal connected to the resistor 10c is connected to a line of a predetermined potential, such as ground.

[0015] The piezoelectric vibrating piece 10a, temperature sensor 10b, and resistor 10c are housed in any suitable container, such as a ceramic airtight container. Furthermore, the piezoelectric vibrator 10 includes external terminals for connecting to an external electronic device 20: a first terminal 10d and a second terminal 10e for the piezoelectric vibrating piece 10a, a third terminal 10f and a fourth terminal 10g for the temperature sensor 10b and resistor 10c, and a fifth terminal 10h connected to the connection point between the temperature sensor and the resistor. These terminals 10d to 10h are provided, for example, on the outer bottom surface of the ceramic container. While not shown, the present invention can of course be applied to both single-chamber type piezoelectric vibrators with built-in temperature sensors and H-shaped piezoelectric vibrators with built-in temperature sensors.

[0016] The external electronic device 20 includes a voltage detection circuit 20c that detects the voltage between the terminals of the temperature sensor 10b, and an oscillation circuit 20d for the piezoelectric vibrating piece 10a. The temperature compensation circuit 20a, the predetermined power supply 20b, the voltage detection circuit 20c, and the oscillation circuit 20d can be configured using known components. In this embodiment, the piezoelectric vibrator 10 and the external electronic device 20 can form a reference signal generating device 21, which corresponds to the second invention of this application. The external electronic device 20 may be any of various devices that can use the piezoelectric vibrator 10, such as a chipset provided by a chipset manufacturer, or a Bluetooth (registered trademark) device or WLAN device that uses the chipset.

[0017] As can be seen from the block diagram of the conventional piezoelectric vibrator 30 and external electronic device 40 shown in Figure 2, the conventional piezoelectric vibrator is configured with a fixed resistor 40a on the external electronic device side, and the piezoelectric vibrator 30 is configured with a piezoelectric vibrating piece 10a and a temperature sensor 10b, whereas the piezoelectric vibrator 10 of the present invention is configured with a predetermined resistor having a first resistance value, a second resistance value, or a third resistance value on the piezoelectric vibrator 10 side, and no resistor on the external electronic device 20 side. However, a resistor may of course be provided on the external electronic device 20 side for purposes such as circuit protection. In that case, the divided voltage according to the present invention is determined taking this resistor into consideration.

[0018] 2. Actions and Effects of the Present Invention Next, in order to deepen understanding of the present invention, the actions and effects produced by the configuration of the present invention will be described using specific examples. The temperature characteristic of the resistance value Rth of the NTC thermistor used as the temperature sensor 10b can be approximated by, for example, the following equation: In the equation, Ro is the resistance value at the reference temperature, To is a reference temperature (e.g., 25°C), T is the ambient temperature, and B is a constant. Rth=Ro / e B(1 / T-1 / To) Therefore, the voltage Vth at the midpoint of the series circuit of resistor 10c and temperature sensor 10b shown in Figure 1 is obtained by dividing the voltage Vbias of power supply 20b by the resistance value Rth of the thermistor and the resistance value r of resistor 10c, and is therefore the voltage shown in the following formula. Vth=Rth Vbias / (r+Rth)

[0019] Therefore, the temperature information obtained from the voltage detected by the temperature sensor 10b is information expressed by the following formula: In the formula, T is the ambient temperature (temperature information), and To is an arbitrary reference temperature (for example, 25° C.). TIFF2026011495000002.tif43165

[0020] On the other hand, the frequency-temperature characteristics of the AT-cut quartz crystal vibrating piece 10a can be approximated by a higher-order approximation formula, or more simply, the following third-order approximation formula: In the formula, T is the ambient temperature, To is an arbitrary reference temperature (e.g., 25°C), F is the oscillation frequency of the quartz crystal resonator at the reference temperature To, dF is the difference (F-Fn) between the oscillation frequency Fn of the quartz crystal vibrating piece at a certain temperature and the oscillation frequency F of the quartz crystal vibrating piece at the reference temperature, and dF / F is the frequency deviation due to changes in ambient temperature. Additionally, a, b, c, and d are coefficients. dF / F=a(T-To) 3 +b(T-To) 2 +c(T-To)+d

[0021] The frequency-temperature characteristics of each crystal unit will differ. To simplify the explanation and the illustration, Figure 3(A) shows three examples of the many different frequency-temperature characteristics: a first frequency-temperature characteristic X, a second frequency-temperature characteristic Y, and a third frequency-temperature characteristic Z. The horizontal axis of Figure 3 represents temperature, and the vertical axis represents frequency deviation. The constant C is set to 0 for simplicity. This is to ensure that the frequencies at 25°C of the three illustrated frequency-temperature characteristics X, Y, and Z are the same. Therefore, in this embodiment, these three temperature characteristics are assumed to be several frequency-temperature characteristics that arise due to manufacturing variations and the like, and the first frequency-temperature characteristic X is assumed to be a representative frequency-temperature characteristic. TIFF2026011495000003.tif53169

[0022] In the above-described assumption, the correction formula that is stored in advance in the temperature compensation circuit 20a provided in the external electronic device 20 to which the piezoelectric vibrator 10 of the embodiment is connected is a correction formula based on the first frequency-temperature characteristic X. For example, assuming that the voltage Vbias of the power supply 20b is 3V, the constant B of the temperature sensor 10b is 4250K, and the resistance Ro of the temperature sensor at a base temperature of 25°C is 100kΩ, the first resistance value of the resistor 10c according to the present invention, i.e., the first resistance value at which the desired temperature compensation result is obtained using the correction formula pre-stored in the external electronic device, is typically 100kΩ. This is because the first resistance value is typically set so that the voltage at the terminal 10h is half the value of Vbias. In the case of the piezoelectric vibrator 10 of the present invention, since it is provided with the resistor 10c having the first resistance value, the second resistance value, or the third resistance value, the following temperature compensation becomes possible.

[0023] (First temperature compensation example) As a first example, consider a case where a quartz crystal unit having a typical frequency-temperature characteristic (first frequency-temperature characteristic X) is connected to external electronic device 20. In this case, resistor 10c provided in quartz crystal unit 10 is a resistor having a first resistance value, i.e., a resistance value of 100 kΩ, that can make the inter-terminal voltage of temperature sensor 10b (the voltage at terminal 10h in FIG. 1) a voltage predicted by a predetermined correction formula. Therefore, in this first example, as shown in FIG. 3(B), the frequency-temperature characteristic X before correction is smoothly corrected by correction formula X1, and the frequency-temperature characteristic X0 after correction is flat.

[0024] (Second example of temperature compensation) As a second example, consider the case where a crystal unit having the second frequency-temperature characteristic Y shown in Fig. 3A is connected to the external electronic device 20. That is, consider the case where a crystal unit having the temperature characteristic Y rotated clockwise with respect to the first frequency-temperature characteristic X is connected. In this case, resistor 10c is a resistor having a second resistance value smaller than the first resistance value, for example, a resistance value of 90 kΩ, in order to convert the inter-terminal voltage of temperature sensor 10b (the voltage at terminal 10h in Fig. 1) into a correction voltage according to the individual difference of the piezoelectric unit. The state of temperature compensation in this second example is shown in Figure 4(A), which also shows the state of compensation when resistor 10c is a 100 kΩ resistor and when resistor 10c is a 90 kΩ resistor.

[0025] As shown in Figure 4(A), when the second frequency-temperature characteristic Y is corrected using correction formula X1 based on a resistor (100 kΩ) corresponding to a typical frequency-temperature characteristic, the correction result is Y1. In contrast, when the second frequency-temperature characteristic Y is corrected using correction formula X2 based on a resistor having a second resistance value (90 kΩ in this case), the correction result is Y2. It can be seen that correction using a resistor having the second resistance value according to the present invention can improve the frequency-temperature characteristic compared to correction using a resistor having the first resistance value, and can reduce the frequency deviation on the high-temperature side by approximately 10 ppm in particular.

[0026] (Third temperature compensation example) As a third example, consider the case where a crystal unit having the third frequency-temperature characteristic Z shown in Figure 3(A) is connected to the external electronic device 20. That is, consider the case where a crystal unit having the temperature characteristic Z rotated counterclockwise with respect to the first frequency-temperature characteristic X is connected. In this case, resistor 10c is a resistor having a third resistance value greater than the first resistance value, for example, a resistance value of 110 kΩ, in order to convert the inter-terminal voltage of temperature sensor 10b (the voltage at terminal 10h in Figure 1) into a correction voltage according to the individual difference of the piezoelectric unit. The state of temperature compensation in this third example is shown in Figure 4(B), which also shows the state of compensation when resistor 10c is a 100 kΩ resistor and when resistor 10c is a 110 kΩ resistor.

[0027] As shown in Figure 4(B), when the third frequency-temperature characteristic Z is corrected using correction formula X1 based on a resistor (100 kΩ) corresponding to a typical frequency-temperature characteristic, the correction result is Z1. In contrast, when the third frequency-temperature characteristic Z is corrected using correction formula X3 based on a resistor having a third resistance value (110 kΩ in this case), the correction result is Z2. It can be seen that correction using a resistor having the third resistance value according to the present invention can improve the frequency-temperature characteristic compared to correction using a resistor having the first resistance value, and can reduce the frequency deviation at high temperatures in particular by about 10 ppm.

[0028] As described above, the piezoelectric vibrator of the present invention is provided with a resistor for each piezoelectric vibrator that corrects the terminal voltage of the temperature sensor to an appropriate value, and it can be seen that the frequency-temperature characteristics after compensation can be improved compared to when the resistor is not used. Moreover, the temperature compensation accuracy can be improved simply by adding an appropriate resistor. It should be noted that the present invention can of course be applied to both a one-room type piezoelectric vibrator with a built-in temperature sensor and an H-type piezoelectric vibrator with a built-in temperature sensor. [Explanation of symbols]

[0029] 10: Piezoelectric vibrator of an embodiment 10a: Piezoelectric vibrating piece 10b: Temperature sensor 10c: Resistor according to the present invention 10d, 10e: First terminal, second terminal (terminal for piezoelectric vibrating piece) 10f, 10g: 3rd terminal, 4th terminal (terminals for temperature sensor and resistor) 10h: 5th terminal (the lead-out terminal at the midpoint between the temperature sensor and the resistance value) 20: External electronic device connected to the piezoelectric vibrator 20a: Temperature compensation circuit 21: Reference signal generator

Claims

1. A temperature sensor built-in piezoelectric vibrator is provided with a piezoelectric vibrating piece having frequency-temperature characteristics and a temperature sensor, and is used by being connected to an external electronic device having a temperature compensation circuit that compensates for the oscillation frequency of the piezoelectric vibrating piece in accordance with temperature information detected by the temperature sensor and a predetermined correction formula, the temperature sensor detects a voltage between its terminals as the temperature information by the external electronic device connected thereto; A piezoelectric vibrator with a built-in temperature sensor, characterized in that it comprises a resistor having one end connected to the temperature sensor and the other end connected to a predetermined power supply of the external electronic device to which it is connected, the resistor having a first resistance value that can make the inter-terminal voltage a voltage predicted by the predetermined correction formula, or a second resistance value smaller than the first resistance value or a third resistance value larger than the first resistance value that can make the inter-terminal voltage a correction voltage according to individual differences of the piezoelectric vibrator.

2. 2. The piezoelectric vibrator with an integrated temperature sensor according to claim 1, wherein the second resistance value and the third resistance value are resistance values ​​that can correct the frequency-temperature characteristic of a quartz crystal vibrator having a frequency-temperature characteristic that deviates from a typical frequency-temperature characteristic in a direction that improves the frequency-temperature characteristic compared to the first resistance value.

3. The piezoelectric vibrator with an integrated temperature sensor as described in claim 1, characterized in that the piezoelectric vibrator has external terminals for connecting to the external electronic device, including a first terminal and a second terminal for the piezoelectric vibrating piece, a third terminal and a fourth terminal for the temperature sensor and resistor, and a fifth terminal connected to the connection point of the temperature sensor and the resistor.

4. 4. The temperature sensor-embedded piezoelectric vibrator according to claim 1, wherein the piezoelectric vibrating piece is an AT-cut quartz crystal vibrating piece.

5. A reference signal generating device comprising: a piezoelectric vibrator with a built-in temperature sensor according to any one of claims 1 to 3; and an external electronic device having a temperature compensation circuit that compensates for the oscillation frequency of the piezoelectric vibrating reed according to temperature information detected by the temperature sensor and a predetermined correction formula.

6. 6. The reference signal generating device according to claim 5, wherein the piezoelectric vibrating piece is an AT-cut quartz crystal vibrating piece.

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