JP2000077938A - Quartz oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the output of a stable frequency even when a difference occurs in the characteristics of respective quartz vibrators while keeping the non-linear relation of quartz oscillator temperature and frequency by performing the optimum management of a heater temperature while controlling the gate pulse duty of an MOSFET in a regulator circuit. SOLUTION: A pulse signal outputted from a pulse width modulation circuit 13 is amplified by driver circuits 14a and 14b and inputted to the gates of MOSFET 15a and 15b later. The MOSFET 15a and 15b are alternately repeat ON/OFF, a transformer 16 is excited by a current flowing from a power source 26a, and a voltage is generated on its secondary side. Concerning this voltage, the unwanted ripple or the like is suppressed by a rectifier/filter circuit 17, and a smoothed DC voltage is impressed to a heater 2. Therefore, since the gate pulse duty of MOSFET 15 is appropriately controlled corresponding to temperature information from a thermistor 5, the heater voltage can be managed to the optimum value corresponding to the characteristics of a quartz oscillator 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator used in microwave communication, radar, and the like, and more particularly to stabilization of a frequency characteristic thereof.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional crystal oscillator. In this figure, 1 is a crystal oscillator, 2 is a heater, 3 is an oscillation circuit, 4 is a buffer circuit, 5 is a thermistor, 6 is a comparison circuit, 7 is a transistor, 26a is a first power supply, and 26b is a second power supply. , 26c are the third power source, 27
a is a first resistor, 27b is a second resistor, 27c is a third resistor, 27d is a fourth resistor, 27e is a fifth resistor, 28
a is the first capacitor, 28b is the second capacitor, 2
9 is a transistor, 30 is a differential amplifier, 31 is a reference power supply, and 32 is a diode.

Next, the operation will be described. Crystal unit 1
The crystal vibrates when an appropriate bias is applied, and the transistor 29, the first resistor 27a connected between the second power supply and the collector of the transistor 29, and the first resistor 27a connected between the second power supply and the base of the transistor 29 Two resistors 27b,
A third resistor 27c connected between the emitter of the transistor 29 and the ground; a first capacitor 28a connected between the emitter and the base of the transistor 29;
Second capacitor 2 connected between base 9 and ground
8b and the like, and resonates at a predetermined frequency to generate a stable and amplified oscillation signal. This oscillation signal is further amplified by the buffer circuit 4 and reaches a specific level. At this time, the quartz oscillator 1 is loosened by the heater 2 and maintained at a predetermined temperature. The resistance value of the thermistor 5 changes according to the temperature of the crystal unit 1, and as a result, the voltage of the third power supply 26 c
d, the voltage is divided by the fifth resistor 27e and the resistor of the thermistor 5, so that the voltage input to the differential amplifier 30 in the comparison circuit 6 is changed and compared with the voltage of the reference voltage power supply 31, and the difference is It is amplified by the dynamic amplifier 30 and output as a control signal. The control signal is a rectifying diode 3
As a result, the current flowing from the first power supply 26a to the heater 2 is adjusted, and the temperature of the heater 2 is controlled. As a result, the temperature of the crystal unit 1 is controlled according to the environmental temperature.

[0004]

A conventional crystal oscillator is:
As described above, since the control is performed by the thermistor 5 and the comparison circuit 6, the control of the heater temperature has a substantially linear relationship with the environmental temperature. However, the temperature and frequency characteristics of the crystal unit have a non-linear relationship as shown in FIG. 7, and it is necessary to operate the device in a temperature range near the turning point where the slope of the characteristics becomes zero. It was difficult. In addition, the relationship between the temperature and the frequency of the crystal oscillator often has different temperature characteristics depending on the individual crystal oscillators, and it has been difficult to cope with such a difference between the individual characteristics.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the relationship between the temperature and the frequency of the crystal unit is non-linear, and even if there is a difference in the characteristics of the individual crystal units. And a crystal oscillator that obtains an output with a stable frequency.

[0006]

A crystal oscillator according to a first aspect of the present invention constitutes a regulator circuit for a heater by a push-pull circuit, and stores a control value corresponding to an ambient temperature and characteristics of a crystal oscillator in a memory. By controlling the gate pulse duty of the metal oxide semiconductor field effect transistor (MOSFET) in the regulator circuit by controlling the pulse output duty of the pulse width modulation circuit by the control value of the memory, the heater temperature is controlled. Is optimally managed to stabilize the oscillation frequency.

A crystal oscillator according to a second aspect of the present invention forms a regulator circuit for a heater by a forward converter circuit, and stores a control value in accordance with an environmental temperature and characteristics of a crystal oscillator in a memory. Adjusts the pulse output duty of the pulse width modulation circuit according to the control value of the memory to control the gate pulse duty of the MOSFET in the above to optimize the heater temperature while controlling and stabilize the oscillation frequency. It is.

A crystal oscillator according to a third aspect of the invention forms a regulator circuit for a heater by a flyback converter circuit, and stores a control value corresponding to an environmental temperature and characteristics of a crystal oscillator in a memory. Adjusts the pulse output duty of the pulse width modulation circuit according to the control value of the memory to control the gate pulse duty of the MOSFET in the above to optimize the heater temperature while controlling and stabilize the oscillation frequency. It is.

A crystal oscillator according to a fourth aspect of the present invention comprises a regulator circuit for a heater using a full-bridge converter circuit, and stores, in a memory, a control value corresponding to the ambient temperature and the characteristics of the crystal oscillator, Adjusts the pulse output duty of the pulse width modulation circuit according to the control value of the memory to control the gate pulse duty of the MOSFET in the above to optimize the heater temperature while controlling and stabilize the oscillation frequency. It is.

A crystal oscillator according to a fifth aspect of the present invention forms a heater regulator circuit by a series regulator circuit, and stores a control value in accordance with the environmental temperature and the characteristics of the crystal oscillator in a memory. By controlling the base voltage of the transistor inside by the control value of the memory, the heater temperature is optimally managed and the oscillation frequency is stabilized.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing Embodiment 1 of the present invention.
Reference numerals 5 and 26 to 29 are the same as those of the above-mentioned conventional apparatus. 8 is a temperature sensor circuit, 9 is an A / D converter, 10
Is a latch circuit, 11 is an erasable / programmable read only memory (EPROM) circuit, 12 is a D / A converter, 13 is a pulse width modulation circuit, 14 is a driver circuit, 15 is a MOSFET, 16 is a transformer, and 17 is a rectifier / filter circuit. It is.

Next, the operation will be described. Crystal unit 1
The crystal vibrates when an appropriate bias is applied, and the first resistor 27 a connected between the transistor 29, the second power supply and the collector of the transistor 29, and the first resistor 27 a connected between the second power supply and the base of the transistor 29. Two resistors 27b,
A third resistor 27c connected between the emitter of the transistor 29 and the ground; a first capacitor 28a connected between the emitter and the base of the transistor 29;
Second capacitor 2 connected between base 9 and ground
8b and the like, and resonates at a predetermined frequency to generate a stable and amplified oscillation signal. This oscillation signal is further amplified by the buffer circuit 4 and reaches a specific level. At this time, the quartz oscillator 1 is loosened by the heater 2 and maintained at a predetermined temperature. The resistance value of the thermistor 5 changes depending on the temperature of the crystal unit 1, and the change in the resistance value is detected by the temperature sensor circuit 8 and output as an analog signal. This output signal is A /
After being digitized by the D converter 9, it is held by the latch circuit 10 and input to the EPROM circuit 11. The digitized temperature signal is EP
A control signal which is read as an address in the ROM circuit 11 and stored so as to control the heater in order to stabilize the output frequency in accordance with the temperature characteristics and the environmental temperature of the crystal unit 1 is read from the EPROM circuit 11.

This signal is input to a D / A converter 12, converted into an analog signal, and input to a pulse width modulation circuit 13.
This analog signal is compared with a specific triangular wave generated in the pulse width modulation circuit 13 and generates a pulse when the voltage of the triangular wave is high, and generates a pulse when the voltage of the analog signal is high.
V outputs. Therefore, the lower the voltage of the analog signal, the higher the pulse duty. The pulse width modulation circuit 13 is configured to output two pulse signals alternately, and each pulse signal is
MOSFET 15a after being amplified by 4a and 14b
And the gate of the MOSFET 15b.

Therefore, the MOSFET 15a and the MOSFE
T15b alternately repeats ON / OFF to excite the transformer 16 with a current flowing from the first power supply 26a to generate a voltage on its secondary side. This voltage is smoothed by the rectification / filter circuit 17 by the rectification and filter functions to suppress unnecessary ripples and the like, and a smoothed DC voltage is applied to the heater 2. Therefore, by appropriately controlling the gate pulse duty of the MOSFET 15 based on the temperature information from the thermistor 5, the heater voltage can be controlled to an optimum value in accordance with the characteristics of the crystal unit 1, and the oscillation frequency can be stabilized. Can be achieved. FIG. 8A shows the relationship between the conventional environmental temperature and the heater control temperature.
The characteristic shown in FIG. 8C, which is approximately similar to the required heater control temperature curve according to the characteristic of the crystal unit shown in FIG.

Embodiment 2 FIG. 2 is a block diagram showing a second embodiment of the present invention, in which 1 to 17 and 26 to 29 are the same as those in the first embodiment. 18 is a diode, 19 is a resistor, 20 is a capacitor, and 26 is a power supply.

Next, the operation will be described. Crystal unit 1
1 to the pulse width modulation circuit 13 are the same as in the first embodiment, and a description thereof will be omitted. The signal output from the pulse width modulation circuit 13 is amplified by a driver circuit 14 and then amplified by a MOSFET.
Input to the gate of T15. When the MOSFET 15 is ON, a current flows from the power supply via the transformer 16 and the MOSFET 15. In the case of OFF, the diode 16, the resistor 19, the capacitor 20,
Current flows in the loop of the transformer 16. With this series of operations, the current from the first power supply 26
Excites to generate a voltage on its secondary side. This voltage is smoothed by a rectifier / filter circuit 17 by rectifying and filtering functions to suppress unnecessary ripples and the like, and a smoothed DC voltage is applied to the heater. Therefore, by appropriately controlling the gate pulse duty of the MOSFET 15 based on the temperature information from the thermistor 5, the heater voltage can be controlled to an optimum value in accordance with the characteristics of the crystal unit 1, and the oscillation frequency can be stabilized. Can be achieved. FIG. 8A shows the relationship between the conventional environmental temperature and the heater control temperature. FIG. 8B shows a conventional heater control temperature curve which is substantially approximated according to the characteristics of the crystal unit shown in FIG. The characteristic shown in (c) is obtained.

Embodiment 3 FIG. 3 is a block diagram showing a third embodiment of the present invention, in which 1 to 17 and 26 to 29 are the same as those in the first embodiment. 21 is a diode and 26 is a power supply.

Next, the operation will be described. Crystal unit 1
1 to the pulse width modulation circuit 13 are the same as in the first embodiment, and a description thereof will be omitted. The signal output from the pulse width modulation circuit 13 is amplified by a driver circuit 14 and then amplified by a MOSFET.
Input to the gate of T15. When the MOSFET 15 is ON, the first power supply 26 supplies the transformer 16, the MOSFET 1
The current flows via the line 5. When it is OFF, no current flows on the primary side. However, current flows in the loop of the transformer 16, the diode 21, and the rectifier / filter circuit 17 due to the electromotive force on the secondary side of the transformer 16. By this series of operations, a DC voltage accompanied by a continuous ripple is generated on the secondary side. This voltage is smoothed by the rectifier / filter circuit 17 by the rectifier and filter functions to suppress unnecessary ripples and the like, and a smoothed DC voltage is applied to the heater. Therefore, according to the temperature information from the thermistor 5, the MOSFE
By appropriately controlling the gate pulse duty of T15, the heater voltage can be controlled to an optimum value according to the characteristics of the crystal unit 1, and the oscillation frequency can be stabilized. FIG. 8 (a) shows a conventional relationship between the ambient temperature and the heater control temperature. FIG. 8 (b) approximates a heater control temperature curve required according to the characteristics of the crystal unit shown in FIG. 8 (b) according to the present invention. The characteristic shown in (c) is obtained.

Embodiment 4 FIG. 4 is a block diagram showing a fourth embodiment of the present invention, in which 1 to 14 and 26 to 29 are the same as those in the first embodiment. 15a is the first MOSFET and 15b is the second MOSFET.
SFET, 15c is the third MOSFET, 15d is the fourth MOSFET
, 16 is a transformer, 17 is a rectifier / filter circuit, 22a is a first diode, 22b is a second diode, 22c is a third diode, and 22d is a fourth diode.

Next, the operation will be described. Crystal unit 1
1 to the pulse width modulation circuit 13 are the same as in the first embodiment, and a description thereof will be omitted. The signal output from the pulse width modulation circuit 13 is amplified by a driver circuit 14 and then amplified by a MOSFET.
Input to the gates of T15a to 15d. MOSFET1
5a and MOSFET 15c are different from MOSFET 15b and M
When the OSFETs 15d are turned on / off in pairs, the transformer 16 is excited, and a voltage is generated on the secondary side. When all MOSFETs are OFF, MOS
After the FET 15a and the MOSFET 15c are turned on, the energy of the transformer 16 flows and is discharged in the order of the diode 22b, the first power supply 26b, the ground, the diode 22d, and the transformer 16 of the transformer 16. When all MOSFETs are OFF, MOS
After the FET 15d and the MOSFET 15d are turned on, the energy of the transformer 16 is discharged from the transformer 16 in the order of the diode 22a, the first power supply 26b, the ground, the diode 22c, and the transformer 16. The voltage generated on the secondary side is applied to the heater 2 by the rectifier / filter circuit 17, in which unnecessary ripples and the like are suppressed by the rectification and filter function and smoothed. Therefore, the temperature information from the thermistor 5 allows M
By appropriately controlling the gate pulse duty of the OSFETs 15a to 15d, the heater voltage can be controlled to an optimum value according to the characteristics of the crystal unit 1, and the oscillation frequency can be stabilized. FIG. 8A shows the relationship between the conventional environmental temperature and the heater control temperature.
The characteristic shown in FIG. 8C, which is approximately similar to the required heater control temperature curve according to the characteristic of the crystal unit shown in FIG.

Embodiment 5 FIG. 5 is a block diagram showing a fifth embodiment of the present invention.
14 is the same as that of the first embodiment. 23 is a transistor, 24 is a diode, 25 is a filter circuit,
26 is a power supply.

Next, the operation will be described. Crystal unit 1
1 to EPROM circuit 11 are the same as in the first embodiment, and a description thereof will be omitted. The duty-related signal relating to the temperature is read as an address in the EPROM circuit 11, and a control signal stored so as to control the heater to stabilize the output frequency in accordance with the temperature characteristics of the crystal unit 1 and the environmental temperature is stored. It is read from the EPROM circuit 11. This signal is input to the D / A converter 12, converted into an analog signal, amplified by the driver circuit 14, and then input to the base of the transistor 23. By controlling the voltage between the collector and the emitter of the transistor 23 according to the level of the base voltage, a desired voltage is output from the first power supply 26 via the diode 24 and smoothed by the filter circuit 25, and then the heater 2 is turned on. Is applied to Therefore, by appropriately controlling the base voltage of the transistor 23 based on the temperature information from the thermistor 5, the heater voltage can be controlled to an optimum value in accordance with the characteristics of the crystal unit 1.
The oscillation frequency can be stabilized. FIG. 8A shows the relationship between the conventional environmental temperature and the heater control temperature. FIG. 8B shows a conventional heater control temperature curve which is substantially approximated according to the characteristics of the crystal unit shown in FIG. The characteristic shown in (c) is obtained.

[0023]

According to the first aspect of the invention, by storing the necessary control signals in the memory, it becomes possible to control the optimum heater temperature in accordance with the environmental temperature, and to reflect the characteristics of the crystal unit. Therefore, the output frequency of the oscillator can be stabilized. Also, the primary side of the transformer and 2
Since the return line on the next side can be isolated, noise interference around the heater circuit can be improved.

According to the second aspect of the invention, by storing the necessary control signals in the memory, it becomes possible to control the heater temperature optimally in accordance with the environmental temperature and to reflect the characteristics of the crystal unit. Therefore, the output frequency of the oscillator can be stabilized. In addition, since the primary and secondary return lines of the transformer can be isolated, noise interference around the heater circuit can be improved. Although the noise is slightly larger than that of the first invention, the number of driver circuits is halved and the circuit is made up of one MOSFET, a diode, a resistor, and a capacitor, so that the circuit can be simplified and the cost can be reduced.

According to the third aspect of the invention, by storing the necessary control signals in the memory, it is possible to control the heater temperature optimally according to the environmental temperature, and to further reflect the characteristics of the crystal unit. Therefore, the output frequency of the oscillator can be stabilized. In addition, since the primary and secondary return lines of the transformer can be isolated, noise interference around the heater circuit can be improved. Although the noise is slightly larger than in the first and second inventions, one MOSFET and one diode 1
It is possible to simplify the circuit and reduce the cost.

According to the fourth aspect of the invention, by storing the necessary control signals in the memory, it becomes possible to control the heater temperature optimally in accordance with the environmental temperature, and to further reflect the characteristics of the crystal unit. Therefore, the output frequency of the oscillator can be stabilized. In addition, since the primary and secondary return lines of the transformer can be isolated, noise interference around the heater circuit can be improved. Although the circuit scale is slightly larger than the first, second and third inventions, a relatively large current can be handled on the primary side, so that the heater temperature control can be speeded up, which is advantageous when the environmental temperature range is wide. become.

According to the fifth aspect of the invention, by storing the necessary control signals in the memory, it is possible to control the heater temperature optimally in accordance with the environmental temperature, and to further reflect the characteristics of the crystal unit. Therefore, the output frequency of the oscillator can be stabilized. Although the power conversion efficiency is lower than those of the first, second, third and fourth inventions, a pulse width modulation circuit, a transformer, a rectifier circuit, and the like are not required, and the circuit configuration is most simplified to reduce the cost. I can do it.

[Brief description of the drawings]

FIG. 1 is a diagram showing Embodiment 1 of a crystal oscillator according to the present invention.

FIG. 2 is a diagram showing a second embodiment of the crystal oscillator according to the present invention.

FIG. 3 is a diagram showing Embodiment 3 of a crystal oscillator according to the present invention.

FIG. 4 is a diagram showing a fourth embodiment of a crystal oscillator according to the present invention.

FIG. 5 is a diagram showing a fifth embodiment of the crystal oscillator according to the present invention.

FIG. 6 is a diagram illustrating an example of a configuration of a conventional crystal oscillator.

FIG. 7 is a diagram showing the relationship between the temperature of a crystal unit and the oscillation frequency.

FIG. 8 is a diagram showing a relationship between an ambient temperature and a heater control temperature in the crystal unit.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 crystal oscillator, 2 heater, 3 oscillation circuit, 4 buffer circuit, 5 thermistor, 6 comparison circuit, 7 first transistor, 8 temperature sensor circuit, 9 A / D converter, 10 latch circuit, 11 EPROM circuit, 12
D / A converter, 13 pulse width modulation circuit, 14
Driver circuit, 14a First driver circuit, 14b
Second driver circuit, 14c Third driver circuit, 1
4d Fourth driver circuit, 15 MOSFET, 15
a first MOSFET, 15b second MOSFET,
15c Third MOSFET, 15d Fourth MOSF
ET, 16 transformer, 17 rectifier / filter circuit, 1
8 Diode, 19 resistor, 20 capacitor, 21
Diode, 22a first diode, 22b second
Diode, 22c third diode, 22d fourth diode, 23 transistor, 24 diode, 25 filter circuit, 26a first power supply, 26b
2nd power supply, 27a 1st resistance, 27b 2nd resistance, 27c 3rd resistance, 27d 4th resistance, 27e
Fifth resistor, 28a first capacitor, 28b second capacitor, 29 transistor, 30 differential amplifier, 31 reference power supply, 32 diode.

Claims (5)

[Claims] 1. An oscillation circuit, a crystal resonator connected to the oscillation circuit, a temperature detection element for detecting a temperature of the crystal resonator, and converting temperature information detected by the temperature detection element into an analog signal. A temperature sensor circuit, an A / D converter for digitizing an output signal of the temperature sensor circuit,
A latch circuit that samples and holds the output signal of the A / D converter, reads the output signal of the latch circuit as an address signal, and outputs a control signal stored in accordance with the environmental temperature and the temperature characteristics of the crystal resonator. A memory and a D / A for converting an output signal of the memory into an analog signal
A converter, a pulse width modulation circuit connected to the D / A converter, the duty of a pulse width of which is output in accordance with an input signal level is changed, a driver circuit connected to the pulse width modulation circuit, and a gate formed by the driver circuit First and second metal oxide semiconductor field effect transistors (MOSFETs) connected so as to be driven, a transformer in which the drains of the first and second MOSFETs are connected on the primary side, and one of the transformers A crystal oscillator comprising: a first power supply connected by a center tap of a secondary winding; and a heater connected to a secondary side of the transformer and maintaining a temperature of the crystal resonator at a predetermined value. 2. An oscillation circuit, a crystal resonator connected to the oscillation circuit, a temperature detection element for detecting a temperature of the crystal resonator, and converting temperature information detected by the temperature detection element into an analog signal. A temperature sensor circuit, an A / D converter for digitizing an output signal of the temperature sensor circuit,
A latch circuit that samples and holds the output signal of the A / D converter, reads the output signal of the latch circuit as an address signal, and outputs a control signal stored in accordance with the environmental temperature and the temperature characteristics of the crystal resonator. A memory and a D / A for converting an output signal of the memory into an analog signal
A converter, a pulse width modulation circuit connected to the D / A converter, the duty of a pulse width of which is output in accordance with an input signal level is changed, a driver circuit connected to the pulse width modulation circuit, and a gate formed by the driver circuit A metal oxide semiconductor field effect transistor (MOSFET) connected to be driven, a transformer connected to the drain of the MOSFET, and a MOS of the transformer
A power supply connected to the opposite side of the primary winding to which the FET is connected; a resistor and a diode connected to the power supply; a diode connected to the drain of the MOSFET and the resistor and the diode; A heater connected to the side of the crystal oscillator to maintain the temperature of the crystal resonator at a predetermined value. 3. An oscillation circuit, a crystal resonator connected to the oscillation circuit, a temperature detection element for detecting a temperature of the crystal resonator, and converting temperature information detected by the temperature detection element into an analog signal. A temperature sensor circuit, an A / D converter for digitizing an output signal of the temperature sensor circuit,
A latch circuit that samples and holds the output signal of the A / D converter, reads the output signal of the latch circuit as an address signal, and outputs a control signal stored in accordance with the environmental temperature and the temperature characteristics of the crystal resonator. A memory and a D / A for converting an output signal of the memory into an analog signal
A converter, a pulse width modulation circuit connected to the D / A converter, the duty of a pulse width of which is output in accordance with an input signal level is changed, a driver circuit connected to the pulse width modulation circuit, and a gate formed by the driver circuit A metal oxide semiconductor field effect transistor (MOSFET) connected so as to be driven, a transformer connected on the primary side to the drain and power supply of the MOSFET, and an opposite of a primary winding connected to the MOSFET of the transformer. A crystal oscillator comprising: a power supply connected to a side of the transformer; a diode connected to a secondary side of the transformer; and a heater connected to the diode and maintaining a temperature of the crystal resonator at a predetermined value. 4. An oscillation circuit including a transistor, a resistor, a capacitor, and the like, a crystal resonator connected to the oscillation circuit, a buffer circuit for amplifying an output signal of the oscillation circuit, and a temperature control circuit for controlling the temperature of the crystal resonator. A temperature detecting element for detecting,
A temperature sensor circuit for converting temperature information detected by the temperature detection element into an analog signal, an A / D converter for digitizing an output signal of the temperature sensor circuit,
A latch circuit that samples and holds the output signal of the D converter, a memory that reads the output signal of the latch circuit as an address signal, and outputs a control signal stored corresponding to the environmental temperature and the temperature characteristics of the crystal unit;
A D / A converter that converts the output signal of the memory into an analog signal, a pulse width modulation circuit that is connected to the D / A converter and changes the duty of a pulse width to be output according to an input signal level, and a pulse width modulation circuit. A connected driver circuit; first to fourth metal oxide semiconductor field effect transistors (MOSFETs) connected so that gates are driven by the driver circuit;
MOSFETs connected between drain and source of MOSFET
A fourth diode, a power supply connected to the first and third MOSFETs, a source of the first MOSFET and a drain of the fourth MOSFET connected to one of the primary windings, and a source of the second MOSFET. And a transformer in which the drain of the third MOSFET is connected to the other side of the primary winding, and a heater connected to the secondary side of the transformer to maintain the temperature of the crystal unit at a predetermined value. And a crystal oscillator. 5. An oscillation circuit, a crystal resonator connected to the oscillation circuit, a temperature detection element for detecting a temperature of the crystal resonator, and converting temperature information detected by the temperature detection element into an analog signal. A temperature sensor circuit, an A / D converter for digitizing an output signal of the temperature sensor circuit,
A latch circuit that samples and holds the output signal of the A / D converter, reads the output signal of the latch circuit as an address signal, and outputs a control signal stored in accordance with the environmental temperature and the temperature characteristics of the crystal resonator. A memory and a D / A for converting an output signal of the memory into an analog signal
A converter, a driver circuit connected to the D / A converter, a transistor connected to the base of the driver circuit, a diode connected to the collector of the transistor, a power supply connected to the diode, and connected to an emitter of the transistor And a heater for maintaining the temperature of the crystal unit at a predetermined value.