JPS6227564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature compensated piezoelectric oscillator whose oscillation frequency can be stably controlled against changes in ambient temperature.

Conventionally, a temperature-compensated piezoelectric oscillator of the type shown in the system diagram of FIG. 1 has been put into practical use as a piezoelectric oscillator that can reduce fluctuations in oscillation frequency due to changes in ambient temperature. In FIG. 1, the temperature characteristics of the oscillation frequency of the voltage-controlled piezoelectric oscillator 1 are mainly influenced by the temperature characteristics of the piezoelectric oscillator. For example, in the case of a frequency-temperature characteristic as shown in Figure 2, in order to compensate for the frequency-temperature characteristic, the voltage is applied to a voltage-controlled variable capacitance element added to the circuit element that determines the oscillation frequency. The voltage characteristics of the control voltage with respect to temperature are:
It is necessary that the characteristic be as shown in characteristic a in FIG.
Therefore, in FIG. 1, the output voltage stabilized by the reference voltage generation section 2 is outputted by the control voltage conversion section constituted by a combination circuit of a resistor and a heat-sensitive resistance element such as a thermistor. 3, where an output voltage having a temperature versus voltage characteristic as seen in FIG. 3 is obtained. The control voltage converter 3 is generally constructed of a circuit as shown in FIG. However, due to variations in piezoelectric oscillator manufacturing lots and other factors, and manufacturing irregularities in parts used in voltage-controlled piezoelectric oscillators, the temperature
Since the frequency characteristics change, the temperature versus voltage characteristics must also be changed from a to b or c in FIG. 3 accordingly. In order to obtain a control voltage corresponding to such a change in characteristics, it is necessary to select the values of elements such as the resistance and thermistor in the circuit of the control voltage converter shown in FIG. 4 for each characteristic. Determining such element values requires complicated calculations, and a computer is generally used for this calculation.
Therefore, the design cost of this type of temperature-compensated piezoelectric oscillator increases, and it becomes difficult to standardize the product.As a result, the price increases, and mass production is not possible.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to compensate for temperature compensation of the oscillation frequency due to variations in the characteristics of manufactured parts.
An object of the present invention is to provide a temperature compensated piezoelectric oscillator that allows easy compensation adjustment, standardization of design, and cost reduction.

According to the present invention, a temperature-compensated piezoelectric generator is provided that controls the oscillation frequency of an oscillation circuit including a piezoelectric oscillator and a voltage-controlled variable capacitance element using a voltage generated by following the temperature change of a heat-sensitive resistance element. The oscillator includes a temperature-dependent voltage generation circuit that applies a reference voltage to a connection circuit between the heat-sensitive resistance element and the fixed resistance element, and a logic circuit that has a gate function that is controlled by the output voltage of the temperature-dependent voltage generation circuit. In combination, a temperature compensated piezoelectric oscillator is obtained, characterized in that the output of the logic circuit is applied to the voltage controlled variable capacitance element to control the oscillation frequency of the oscillation circuit.

Next, a temperature compensated piezoelectric oscillator according to the present invention will be described in detail with reference to the drawings. First, FIG. 5 is a system diagram showing the type of piezoelectric oscillator according to the present invention. In this figure, a reference voltage stabilized by a reference voltage generator 2 is applied to a control voltage converter 4, and is converted by a resistor and a heat-sensitive resistance element into an ambient temperature dependent voltage that changes in accordance with changes in ambient temperature. . Then, this ambient temperature dependent voltage is applied to the logic circuit 5, and the gate of the logic circuit 5 is turned on or off at a certain set temperature, and depending on the output voltage, The capacitance of a voltage-controlled variable capacitance element such as a variable-capacitance diode added to the voltage-controlled piezoelectric oscillator 1 can be changed, and as a result, the oscillation frequency can be controlled at a certain temperature point. Therefore, the oscillation frequency changes depending on the ambient temperature, and if the oscillation frequency shifts outside the desired frequency range from a certain temperature, the above logic circuit will change depending on the temperature-dependent voltage at that temperature point. By selecting circuit constants so as to turn the gate "on" or "off", the oscillation frequency can be controlled within a desired frequency range.

FIG. 6 is a circuit diagram showing an embodiment of the present invention which operates as described above. In the figure, the power supply voltage indicated by +B is changed to a constant reference voltage by a constant voltage diode 21, and converted to an ambient temperature dependent voltage by a resistor 22 and a thermistor 23. This voltage is divided by resistors 24 and 25 and resistors 26 and 27, respectively, and is passed through resistors 28 and 29 to the NAND
It is applied to circuits 30 and 31, respectively. on the other hand,
Since a high level voltage is applied to the other input terminals of the NAND circuits 30 and 31 using a stable reference voltage, when the applied input voltage is higher than the threshold voltage, the NAND circuit The output of is at a low level, so that as the ambient temperature increases, the input applied voltage is sequentially converted to a voltage below the threshold. As a result, a substantially step-like voltage change occurs across the resistor 32 connected to the output side. This step-like voltage changes with respect to temperature as shown in FIG.
added to one end of. On the other hand, a stable voltage divided by a resistor 35 and a variable resistor 36 is applied to the other end of the diode 34. Therefore,
The variable capacitance diode 34 is required in order for the voltage-controlled piezoelectric oscillator composed of the transistor 37, the piezoelectric oscillator 38, the variable capacitance diode 34, etc. to compensate for fluctuations in oscillation frequency that occur due to changes in ambient temperature. If the change in applied voltage with respect to temperature is represented by curve a in FIG. 8, then a stepped voltage as shown in b in FIG. 8 is applied to the variable capacitance diode 34 by the circuit in FIG. the result,
A frequency temperature characteristic as shown in FIG. 9a is obtained. Note that FIG. 9b shows the frequency-temperature characteristics before temperature compensation.

According to the above circuit configuration, since the switching temperatures can be set independently by the NAND circuits 30 and 31, it is relatively easy to determine the resistance values of the resistors 24, 25 and 26, 27. In addition, the piezoelectric oscillator 38
The variation in the frequency temperature characteristics of the variable resistor 36
It can be adjusted within a certain range. Further, if the number of logic circuits 30 and 31 is not limited to two, but a large number are used, more detailed compensation can be achieved. In addition,
FIG. 10 shows an example of actual measurement of frequency-temperature characteristics in a piezoelectric oscillator obtained according to the present invention.
This allows ±1× in the ambient temperature range of 0 to 60℃.
Frequency stability within 10 ^-6 was obtained.

As is clear from the above description, according to the present invention, the parts used are This is due to variations in the characteristics of the oscillation frequency.
In that temperature compensation can be easily adjusted and circuits can be standardized, the effect of reducing manufacturing costs is significant.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing the type of a conventional temperature compensated piezoelectric oscillator, Figure 2 is a diagram showing an example of the temperature characteristics of the oscillation frequency of the voltage controlled piezoelectric oscillator itself, and Figure 3 is a diagram showing the temperature characteristics of the oscillation frequency of the voltage controlled piezoelectric oscillator itself. FIG. 4 is a diagram showing an example of temperature vs. control voltage characteristics obtained by a conventional technique in order to control a voltage-controlled piezoelectric oscillator having the characteristics shown in FIG. 5 is a system diagram showing the type of temperature compensated piezoelectric oscillator according to the present invention, FIG. 6 is a circuit diagram showing an embodiment according to the present invention, and FIG. 7 is an output of the logic circuit in FIG. 6. 8 is a diagram showing the relationship between the control voltage characteristics in FIG. 7 and the most preferable control voltage characteristics, and FIG. 9 is a diagram showing the step-like change in control voltage that occurs in the circuit of FIG. FIG. 10 is a diagram showing a change in oscillation frequency with respect to temperature of a temperature-compensated piezoelectric oscillator.
In the figure, 1 is a voltage controlled piezoelectric oscillator, 2 is a reference voltage generator, 3 and 4 are control voltage converters, 5 is a logic circuit, 21 is a constant voltage diode, 22, 24 to 2
9, 32, 33, and 35 are resistors, 23 is a thermistor, 30, 31 are NAND circuits, 34 is a variable capacitance diode, 36 is a variable resistor, 37 is a transistor, and 38 is a piezoelectric oscillator. 〓〓〓〓

Claims (1)

[Claims] 1. In a temperature-compensated piezoelectric oscillator of a type in which the oscillation frequency of an oscillation circuit including a piezoelectric vibrator and a voltage-controlled variable capacitance element is controlled by a voltage generated following a temperature change of a heat-sensitive resistance element, the heat-sensitive A temperature-dependent voltage generation circuit which is formed by applying a reference voltage to a connection circuit between a resistance element and a fixed resistance element, an output voltage of the temperature-dependent voltage generation circuit is supplied to one input, and the reference voltage is supplied to the other input. a gate circuit that generates a stepped control voltage in response to changes in the temperature-dependent voltage; and an output of the gate circuit that is applied to the voltage-controlled variable capacitance element to control the oscillation frequency of the oscillation circuit. A temperature compensated piezoelectric oscillator featuring: