JP2006324937A - Temperature control circuit and high stable piezoelectric oscillator employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein it takes a long time when determining the optimum mount position of a temperature sensor by a qualification test because temperature distribution around a crystal resonator differs depending on a model of a high stable crystal oscillator in the case of carrying out temperature control by arranging the temperature sensor close to the crystal resonator of the high stable crystal oscillator. <P>SOLUTION: The high stable crystal oscillator is configured such that changeover switches S1 to S3 are respectively connected in series with thermisters TH1 to TH3 mounted on printed wiring boards 4a, 4b sandwiching the crystal resonator and connected to ground, and the changeover switches S1 to S3 are mounted on the upper side of the printed wiring board 4a in a way of easily applying opening/closing operations to the changeover switches S1 to S3 when a case 7 is opened. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a temperature control circuit, and more particularly, to a temperature control circuit used in a highly stable piezoelectric oscillator, and more particularly to a temperature control circuit capable of easily selecting a location where a temperature sensor is installed and a highly stable piezoelectric oscillator using the temperature control circuit. .

Conventionally, a crystal oscillator used for a reference frequency signal source such as a communication device or a measuring instrument is required to have a stable output frequency with high accuracy against a temperature change. As a crystal oscillator capable of obtaining extremely high frequency stability, the ambient temperature of an electronic component such as a crystal oscillator whose electrical characteristics are easily affected by temperature is maintained at a constant temperature of, for example, about 80 ° C. There is known a highly stable crystal oscillator that keeps the frequency-temperature characteristic of the frequency constant.
FIG. 4 is an electric circuit diagram showing an example of a temperature control circuit of a conventional highly stable crystal oscillator. As shown in the figure, the temperature control circuit 20 detects the temperature of a crystal resonator (not shown) of a highly stable crystal oscillator and outputs a current based on the detected information, and the control And a heater circuit unit 12 for heating the crystal resonator based on the current value from the unit 11.

The control unit 11 connects the connection midpoint of the resistors R1 and R2 of the series circuit of the resistors R1 and R2 connected between the power source Vcc and the ground to the plus input terminal (+) of the differential amplifier IC1, The connection midpoint of the series circuit of the resistor R3 connected between the power source Vcc and the ground and the thermistor TH11 as a temperature sensor is connected to the minus (−) input of the differential amplifier IC1, and the output of the differential amplifier IC1 is The differential amplifier IC1 is connected to the negative input terminal (−) of the differential amplifier IC1 through a feedback resistor R4.

The heater circuit section 12 is composed of a power MOS FET (hereinafter referred to as FET) Q1 and heaters H1, H2, H3, and H4. The heater H1 is connected between a power source Vcc and a source S of the FET Q1, and The heaters H2, H3, and H4 are connected between the drain D of the FET Q1 and the ground, respectively.
The output of the differential amplifier IC1 is connected to the gate G of the FET Q1. The capacitor C1 is a capacitor for removing AC noise.

The temperature control operation of the highly stable crystal oscillator provided with the temperature control circuit shown in the figure is as follows.
Since the resistance value of the thermistor TH11 disposed in proximity to a crystal resonator (not shown) heated by the heaters H1 to H4 changes according to the ambient temperature, the (+) input of the differential amplifier IC1 and (−) The potential difference from the input changes, and accordingly, the output of the differential amplifier IC1, that is, the voltage applied to the gate G of the FET Q1 is controlled.
As a result, the drain current of the FET Q1, that is, the heat generation temperature of the heaters H1 to H4 is controlled, and the ambient temperature of the crystal resonator or the like can be maintained at a predetermined temperature.

For example, when the temperature rises, the resistance value of the thermistor TH11 decreases, and accordingly, the potential of the (−) input of the differential amplifier IC1 decreases, so that the (+) and (−) inputs of the differential amplifier IC1. The potential difference between the terminals increases, and the output voltage of the differential amplifier IC1 increases.
As a result, the potential difference between the gate and source of the FET Q1 decreases, and the drain current of the FET Q1 flowing through the heaters H1 to H4 decreases. As a result, the heat generation amount of the heaters H1 to H4 is reduced and the temperature is lowered.
On the other hand, when the temperature decreases, the resistance value of the thermistor TH11 increases, and the amount of heat generated by the heaters H1 to H4 increases and the temperature rises, contrary to the above description. In this way, the ambient temperature of the crystal unit or the like is kept constant.
JP 2000-183649 A

However, in a highly stable crystal oscillator, the component that most wants to keep the temperature stable is a crystal resonator, and in particular, a crystal vibration substrate inside the resonator package. However, since the crystal vibration substrate is accommodated in the vacuum package, the temperature on the crystal vibration substrate cannot be directly detected.
Therefore, a temperature sensor is arranged in the vicinity of the crystal unit package and the temperature is detected, so that the temperature of the crystal substrate is approximately detected and temperature control is performed. It is difficult to construct an oscillator that oscillates a stable output frequency with high accuracy.

For this reason, as a means for detecting a temperature closer to the center of the crystal resonator package, there is a method of distributing a plurality of temperature sensors around the crystal resonator and using an average of the detected temperatures.
For example, if two thermistors are used as temperature sensors and are disposed on both side surfaces of the crystal resonator package, the crystal vibration substrate is positioned between the two sensors. Assuming that the temperature gradient between the two thermistors is constant, it can be estimated that the average of the detected temperatures of both thermistors is the temperature of the quartz crystal vibration substrate.
The circuit configuration of the means for taking the average of the two thermistors is realized, for example, by connecting the thermistors in parallel.

However, since the structure around the crystal resonator package is complicated and various materials having different thermal properties are used, the heat distribution of the crystal resonator and its peripheral portion is not uniform. Therefore, the temperature gradient between the thermistors does not become a constant gradient.
Therefore, in the method of using the plurality of thermistors as described above and setting the average of the detected values as the temperature of the middle point, in order to determine the optimum thermistor mounting location for each oscillator model having a different structure around the vibrator In addition, there is a drawback that it takes a lot of time, such as performing a confirmation test by changing the position of the thermistor many times.
On the other hand, as a method of making the temperature gradient between a plurality of thermistors uniformly approach, a method in which a crystal resonator or an oscillation circuit component is enclosed in one metal block (oven) and this oven is controlled and heated to a constant temperature. However, there are cases where this measure cannot be applied due to limitations in terms of product size or weight, or cost.
The present invention has been made to solve the above-described problem, and a temperature control circuit capable of easily determining the mounting location of the temperature sensor of the temperature control circuit and performing temperature control with high accuracy, and the same are used. An object is to provide a highly stable piezoelectric oscillator.

  In order to solve the above problems, in the temperature control circuit according to claim 1, a heater circuit unit including a heater and a transistor amplifier circuit for supplying electric power to the heater, and a temperature sensor for detecting a temperature change of an object to be heated by the heater And a control unit including a differential amplifier that controls an input voltage of the transistor amplifier circuit based on a detection result of the temperature sensor, and a temperature control circuit housed in a sealed container, wherein the temperature sensor Are attached to a plurality of predetermined locations, and a switch is connected in series to each of the temperature sensors.

3. The temperature control circuit according to claim 2, wherein the heater circuit includes a heater, a transistor amplifier circuit that supplies power to the heater, a temperature sensor that detects a temperature change of an object to be heated by the heater, and a detection result of the temperature sensor. And a control unit including a differential amplifier for controlling an input voltage of the transistor amplifier circuit based on the temperature control circuit housed in a sealed container, wherein the temperature sensors are mounted at a plurality of predetermined locations. The temperature sensors are all connected in series, and a switch is connected to each temperature sensor in parallel.

The temperature control circuit according to claim 3 is the temperature control circuit according to claim 1 or 2, wherein the switching device is easily opened and closed when the sealed container is opened. It is mounted in a position where it can be.
A temperature control circuit according to a fourth aspect of the present invention is the temperature control circuit according to any one of the first to third aspects, wherein the switch is formed of a resistor.
Furthermore, a highly stable piezoelectric oscillator according to a fourth aspect of the present invention is characterized by being configured using the temperature control circuit according to any one of the first to fourth aspects.

In the temperature control circuit according to the present invention, a switch is connected to each of the plurality of temperature sensors installed at a predetermined position, and the temperature control circuit is configured using the temperature control circuit, and the oscillator of the oscillator housed in a sealed container is used. When the sealed container is opened, it is attached to a place where the switching device can be easily opened and closed.
As a result, it is possible to solve the problem that a great deal of time is required in a large number of confirmation tests for selecting a temperature sensor at an optimum location from among a plurality of temperature sensors.
Furthermore, the sensitivity of the temperature sensor at a desired location can be easily adjusted by adjusting the resistance value of the switch as a resistor.
Therefore, according to the present invention, it is possible to solve the problem that it takes a lot of time to determine the optimum mounting position of the temperature sensor of the oscillator using the temperature control circuit, and to reduce the temperature and the excellent performance. In providing a control circuit and a highly stable piezoelectric oscillator, a remarkable effect can be exhibited.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is an electric circuit diagram showing an embodiment of a temperature control circuit of a crystal oscillator as a highly stable piezoelectric oscillator according to the present invention.
As shown in the figure, the temperature control circuit 10 detects the temperature of a crystal resonator (not shown) and outputs a current based on this information, and the current value from the control unit 1. And a heater circuit unit 2 for heating the crystal resonator and the like.

The control unit 1 includes resistors R1, R2, R3, and R4, thermistors TH1, TH2, and H3, switches S1, S2, and S3, and a differential amplifier IC1.
The circuit configuration of the control unit 1 includes a thermistor TH11 in the control unit 11 of FIG. 4, a series circuit of a switch S1 and the thermistor TH1, a series circuit of a switch S2 and the thermistor TH2, a series of a switch S3 and the thermistor TH2. The control unit 11 is the same as that shown in FIG. 4 except that the circuit is replaced with a circuit connected in parallel.
The heater circuit unit 2 includes heaters H1, H2, H3, and H4 and a power MOS FET (hereinafter referred to as FET) Q1, and the circuit configuration and operation of the heater circuit unit 2 are shown in FIG. The circuit unit 12 is exactly the same.
Therefore, a detailed description of common parts is omitted.

In the figure, a plurality of switchers S1, S2, S3 are mounted at appropriate positions around a crystal resonator (not shown) and connected between the (−) input terminal of the differential amplifier IC1 and the ground (in the case of FIG. Three thermistors TH1, TH2, and TH3 are connected in series.
In the confirmation test for determining the location of the thermistor of the high stability crystal oscillator using the temperature control circuit 10, the thermistor judged to be unnecessary opens the switch connected to the thermistor. It can be in a disconnected state.

FIG. 2 is a longitudinal sectional view showing an example of the structure of a highly stable crystal oscillator including the temperature control circuit 10 shown in FIG. As shown in the figure, this highly stable crystal oscillator is equipped with the switches S1, S2, S3 of the temperature control circuit 10 on the top surface, and the crystal unit 3, thermistors TH1, TH2, heaters H1, H2 on the bottom surface. And a printed wiring board 4b on which heaters H3 and H4 and a thermistor TH3 are mounted. The switching devices S1, S2, and S3 are jumper wires, and the switching devices S1, S2, and S3 can be opened and closed by attaching and detaching them.
The other components of the temperature control circuit 10 and the oscillation amplification circuit component are mounted on the lower surface of the printed wiring board 4b or other appropriate place, but are not shown for simplicity.

The printed wiring boards 4a and 4b pass through the printed wiring boards 4a and 4b, are fixed to metal pins 6 fixed to the base member 5, and the thermistors TH1 and TH2 and heaters H1 and H2 of the printed wiring board 4a. The quartz vibrator 3 is fixed between the heaters H3 and H4 of the printed wiring board 4b and the thermistor TH3.
Then, the highly stable crystal oscillator is configured by covering the base member 5 with a case 7 and sealing it.

With the above structure, when the case 7 of the highly stable crystal oscillator is removed when performing a confirmation test for selecting the optimum position of the thermistor, the switches S1 to S3 are mounted at the top in FIG. Therefore, this can be easily operated (jumper wire attaching / detaching operation), and an unnecessary thermistor can be disconnected and a required thermistor can be connected in a short time.

In the temperature control circuit 10 of FIG. 1, the switchers S1 to S3 use jumper wires, but these can be used as resistors. In this case, if an unnecessary thermistor is required to remove the switch (resistor) and the sensor sensitivity of the thermistor is to be adjusted, the resistance value of the thermistor is selected by selecting the resistance value of the resistor. Sensitivity can be adjusted.
Further, as a means for adjusting the sensitivity of the thermistors TH1 to TH3, a resistor is connected in parallel to the thermistors TH1 to TH3, and this parallel resistor is mounted on the upper surface of the same printed wiring board 4a as the switchers S1 to S3. Therefore, the time required for selecting the optimum parallel resistance can be shortened.

FIG. 3 is an electric circuit diagram showing another embodiment of the control unit in the temperature control circuit of FIG.
As shown in the figure, the control unit 8 includes resistors R1, R2, R3, and R4, thermistors TH4, TH5, and H6, switches S4, S5, and S6, and a differential amplifier IC1. Instead of the series connection circuit of three sets of thermistors and switches in the control unit 1 of FIG. 1, three thermistors TH4, TH5, and H6 are connected in series to connect between the (−) input terminal of the differential amplifier IC1 and the ground. And the thermistors TH4, TH5, and H6 are connected in parallel to the switchers S4, S5, and S6, respectively.
The operation of controlling the heater current of the heater circuit unit 2 by the control unit 8 is exactly the same as that in FIG.

In the case of this configuration, in the component arrangement shown in FIG. 2, the thermistors TH4 to H6 are mounted at appropriate positions around the crystal resonator, and the switches S4 to S6 are connected in parallel to the respective thermistors, so that the printed wiring board 4a Mounted on top. In this case, the switching device may be a jumper wire, but if a resistor is used, the sensor sensitivity of the thermistor can be adjusted by selecting the resistance value of the resistor as described above.

1 is an electric circuit diagram showing an embodiment of a temperature control circuit of a crystal oscillator as a highly stable piezoelectric oscillator according to the present invention. FIG. 2 is a longitudinal sectional view showing an example of the structure of a highly stable crystal oscillator including the temperature control circuit 10 shown in FIG. The electric circuit diagram which shows the other example of a control part in the temperature control circuit of FIG. FIG. 6 is an electric circuit diagram showing an example of a temperature control circuit of a conventional highly stable crystal oscillator.

Explanation of symbols

1 .... Control part, 2 .... Heater circuit part, 3 .... Quartz crystal, 4a, 4b ... Printed wiring board,
5 .... Base member, 6 .... Metal pin, 7 .... Case, 8 .... Control part,
10 .... Temperature control circuit, 11 .... Control part, 12 .... Heater circuit part,
20 .. Temperature control circuit,
C1, ... Capacitor, H1, H2, H3, H4 ... Heater, IC1, ... Differential amplifier,
Q1..MOS FET, R1, R2, R3, R4..resistance,
S1, S2, S3, S4, S5, S6.
TH1, TH2, TH3, TH4, TH5, TH6, TH11 ・ ・ Thermistor

Claims (5)

A heater circuit unit including a heater and a transistor amplifier circuit that supplies power to the heater, a temperature sensor that detects a temperature change of an object to be heated by the heater, and an input voltage of the transistor amplifier circuit based on a detection result of the temperature sensor A temperature control circuit configured to include a differential amplifier that controls the control unit, and housed in a sealed container,
A temperature control circuit, wherein the temperature sensor is mounted at a plurality of predetermined locations, and a switch is connected in series to each of the temperature sensors. A heater circuit unit including a heater and a transistor amplifier circuit that supplies power to the heater, a temperature sensor that detects a temperature change of an object to be heated by the heater, and an input voltage of the transistor amplifier circuit based on a detection result of the temperature sensor A temperature control circuit configured to include a differential amplifier that controls the control unit, and housed in a sealed container,
A temperature control circuit characterized in that the temperature sensors are mounted at a plurality of predetermined locations and all the temperature sensors are connected in series, and a switch is connected in parallel to each temperature sensor. 3. The temperature control circuit according to claim 1, wherein the temperature control circuit is mounted at a position where the switching device can be easily opened and closed when the sealed container is opened. 4. 4. The temperature control circuit according to claim 1, wherein the switch is constituted by a resistor. A highly stable piezoelectric oscillator comprising the temperature control circuit according to any one of claims 1 to 4.

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