JPS61154206A - Piezoelectric oscillator - Google Patents

Abstract

PURPOSE:To improve the frequency stability by storing a control voltage changing an oscillated frequency of a voltage controlled piezoelectric oscillating section in response to ambient temperature and power supply voltage fluctuation to a read only memory so as to compensate easily the oscillation frequency fluctuation against a wide variety of external fluctuation by means of a simple circuit. CONSTITUTION:An output of a temperature detecting section 1, a power supply voltage detection 2 and a counter 3 or the like is inputted to an analog/digital converter 4, which converts said output into a digital signal and gives the signal as a read only memory section 5. A voltage value to be inputted to a voltage controlled piezoelectric oscillating section 7 is stored in each address of the read only memory section 5 as a digital value. A read data from the read only memory section 5 is converted into an analog value by a digital/analog converting section 6 and fed to a control input of the voltage controlled piezoelectric oscillating section 7 to change the oscillated frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a piezoelectric oscillator, and more particularly to a piezoelectric oscillator with high frequency stability whose oscillation frequency does not change due to changes in ambient temperature or the like.

SUMMARY OF THE INVENTION The present invention provides a frequency change that cancels a change in the oscillation frequency due to a temperature change or the like of a piezoelectric oscillator using a DC voltage supplied to a voltage-controlled piezoelectric oscillator. The DC voltage value to be applied to the voltage-controlled piezoelectric oscillator section in response to temperature changes, etc. is stored in advance as a digital value at each address in the read-only memory section, and the DC voltage value to be applied to the voltage-controlled piezoelectric oscillator section is stored in advance as a digital value in each address of the read-only memory section. By converting the digital value read from the section into an analog signal and supplying it to the control input of the voltage-controlled piezoelectric oscillation section, it is possible to obtain a stable oscillation frequency over a wide range of changes in ambient temperature and the like.

BACKGROUND ART Conventional piezoelectric oscillators have a drawback in that their oscillation frequency changes due to changes in ambient temperature, fluctuations in power supply voltage, or changes over time. This is due to changes in the frequency of the piezoelectric oscillator due to changes in ambient temperature, changes in the impedance of semiconductor elements in the oscillation circuit due to changes in power supply voltage, and changes in the characteristics of the oscillator mechanical components over time. be.

Conventionally, in order to prevent the oscillation frequency stability from deteriorating due to the various fluctuation factors listed in h. We are taking measures to prevent this.

Problems with the Prior Art The above-mentioned conventional solutions have the disadvantage that the components become expensive and are not suitable for mass production.

In addition, for example, when an AT-cut crystal resonator is used, the temperature characteristics of the oscillation frequency are as shown in curve a in Figure 2.
The temperature range in which the frequency is stable against temperature changes is narrow, and the frequency changes between low and high temperatures are large, so a normal temperature compensation circuit cannot compensate the oscillation frequency over a wide temperature range of 1f. It is difficult to do so.

Furthermore, with a piezoelectric oscillator of low commercial voltage, it may not be possible to supply constant voltage power using a constant voltage diode or the like.

1-4 of the invention 1.1 of the present invention solves the conventional drawbacks mentioned in 1-1, and stabilizes the oscillation frequency easily in a circuit that is in motion and even against a wide range of changes in fluctuation factors. The object of the present invention is to provide a piezoelectric oscillator with high frequency stability.

Composition of the Invention The piezoelectric oscillator of the present invention includes: a voltage-controlled piezoelectric oscillator whose oscillation frequency is varied by a human-powered DC voltage; an analog-to-digital converter which converts and outputs analog information such as temperature and power supply voltage into digital information; The output of the analog-to-digital conversion section is input as a read address signal, and the digital value stored in advance at the address position is output, and the output signal of the partial only memory section and the read only memory section is converted into an analog signal. a digital-to-analog converter for outputting and supplying the output to the control input of the voltage-controlled piezoelectric oscillator; each address of the read-only memory unit stores frequency fluctuations due to temperature and power supply voltage fluctuations of the voltage-controlled piezoelectric oscillator; It is characterized by storing the control voltage value required to compensate for.

Embodiments of the Invention Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

That is, the temperature detection section 1. Power supply voltage detection section 2. Counting part 3
input the output of
The analog/digital converter 4 converts these into digital signals and outputs them as read address signals to the read-only memory section 5. At each address in the read-only memory section 5, a voltage value to be input to the voltage-controlled piezoelectric oscillation section 7 for each condition is stored as a digital value. The read data from the read-only memory section 5 is converted into an analog value by the digital-to-analog conversion section 6 and supplied to the control input of the voltage-controlled piezoelectric oscillation section 7. The voltage-controlled piezoelectric oscillator 7 changes the oscillation frequency according to the direct voltage input from the digital-to-analog converter 6, and the voltage-controlled piezoelectric oscillator 7 changes its oscillation frequency in response to changes in temperature, etc. Digital values that cancel out frequency changes are stored in the read-only memory section 5.

For example, with respect to temperature changes, the read-only memory section 5 stores voltage values such that the oscillation frequency of the voltage-controlled piezoelectric oscillation section 7 follows the curve shown by the dotted line in FIG. Therefore, the output of the temperature detection section 1 is converted into a digital value by the analog-to-digital converter 4, and the digital value read from the read-only memory section 5 is converted into a DC voltage by the digital-to-analog converter 6. By supplying the voltage to the voltage-controlled piezoelectric oscillator 7, the oscillation frequency of the voltage-controlled piezoelectric oscillator 7 becomes stable against temperature changes, as shown by curve C in FIG.

In response to fluctuations in the power supply voltage, the oscillation frequency changes as shown by the curve in FIG.
By supplying the voltage value to the voltage controlled piezoelectric oscillator 7, the fluctuation of the oscillation frequency with respect to the power supply voltage fluctuation shown by the curve a can be canceled out, and the stable oscillation frequency shown by the curve C can be obtained.

In addition, if the oscillation frequency after the power is turned on has a characteristic that changes over time as shown by curve a in FIG.
The oscillation frequency is set according to the output count value of the song vjb in the same figure.
By changing the frequency as shown in FIG. 1, it is possible to obtain a temporally stable oscillation frequency as shown by curve C in the figure.

If these fluctuate at the same time, the analog/digital converter 4 converts these combinations into digital signals,
Each address of the read-only memory unit 5 may store a voltage value that allows the voltage-controlled piezoelectric oscillator 7 to stably oscillate for each combination of conditions.

Effects of the Invention As described in 1-, in the present invention, the control voltage for changing the oscillation frequency of the voltage-controlled piezoelectric oscillator according to the ambient temperature, power supply voltage fluctuation, etc. is stored in the read-only memory section. , easily compensates for oscillation frequency fluctuations over a wide range of external fluctuations with a simple circuit, and improves frequency stability.
It has the effect of being able to do two things.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a diagram showing frequency temperature characteristics of a piezoelectric oscillator, and Fig. 3 is -1-
FIG. 4 is a diagram for explaining changes in oscillation frequency with respect to power supply voltage fluctuations in the embodiment described above, and FIG. In the figure, 1: temperature detection section, 2: power supply voltage detection section, 3
: Counting section, 4: Analog-to-digital conversion section, 5: Read-only memory section, 6: Digital-to-analog conversion section,
7: Voltage controlled piezoelectric oscillator.

Claims (1)

[Claims] A voltage-controlled piezoelectric oscillator whose oscillation frequency is varied depending on an input DC voltage; an analog-to-digital converter that converts and outputs analog information such as temperature and power supply voltage into digital information; a read-only memory section that inputs the output of the digital conversion section as a read address signal and outputs a digital value stored in advance at the address position; and a read-only memory section that converts the output signal of the read-only memory section into an analog signal and outputs the voltage as the read address signal. and a digital-to-analog conversion section that supplies the control input of the controlled piezoelectric oscillation section, and each address of the read-only memory section has information for compensating for frequency fluctuations due to temperature, power supply voltage fluctuations, etc. of the voltage-controlled piezoelectric oscillation section. A piezoelectric oscillator characterized by storing a control voltage value required for the piezoelectric oscillator.