JPS63209307A - Voltage controlled piezoelectric oscillation circuit - Google Patents

Abstract

PURPOSE:To set the oscillation frequency characteristic to an externally applied voltage optionally by digital-coding an external applied voltage, converting the result into an analog signal so as to set the A/D conversion rate and the D/A conversion rate. CONSTITUTION:An external applied voltage is once converted into a digital code (hereinafter referred to as DC) by an A/D converter 3 and its output DC is fed to a memory circuit 4. A voltage control DC corresponding to the DC being an address signal is stored in advance in the circuit to control the change in the oscillated frequency depending on the externally applied voltage. In varying the externally applied voltage, the address signal is also changed and the voltage controlled DC is read from the circuit 4 accordingly, converted into an analog signal by an A/D converter 5 to control the static capacitance of the varactor element 2. The oscillation frequency of the piezoelectric oscillation circuit comprising a piezoelectric resonator 1, a transistor Q, resistors R1-R7 and capacitors C1-C4 are controlled by the capacitance value.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a voltage-controlled piezoelectric oscillator circuit, and particularly to a piezoelectric oscillator circuit that generates piezoelectric oscillation by controlling the capacitance of a variable capacitance element according to the magnitude of an externally applied voltage. This invention relates to a voltage-controlled piezoelectric oscillator circuit that changes the oscillation frequency of the circuit.

[Conventional technology]

In a conventional voltage-controlled piezoelectric oscillator circuit of this type, as shown in the circuit configuration in FIG. The oscillation frequency of the piezoelectric oscillation circuit is controlled by changing the capacitance of the variable capacitance element 2 according to the externally applied voltage value.

[Problem that the invention seeks to solve]

In the conventional voltage-controlled piezoelectric oscillator circuit described above, the change characteristics of the oscillation frequency with respect to the externally applied voltage value are determined by the applied voltage-capacitance characteristics specific to the variable capacitance element 2 as shown in FIG. This method has the disadvantage that only an externally applied voltage--oscillation frequency characteristic with a non-linear portion as shown in FIG. 5 can be obtained, making it unsuitable for applications requiring, for example, a change in oscillation frequency proportional to the externally applied voltage.

[Means for solving problems]

The voltage-controlled piezoelectric oscillator circuit of the present invention includes a variable capacitance element and a piezoelectric resonator whose capacitance changes according to an externally applied voltage value. A digital-to-analog converter for encoding, a memory circuit for storing a voltage compensation digital code corresponding to an address specified by the output digital code of the analog-to-digital converter, and a memory circuit for converting the output digital code of the memory circuit into an analog signal. and a digital-to-analog converter, and is configured to apply an output signal of the digital-to-analog converter to the variable capacitance element to change the capacitance.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In the figure, an externally applied voltage is once converted into a digital code by an analog/digital converter 3. The output digital code of analog-to-digital converter 3 is
The signal is supplied to the memory circuit 4.

In order to control changes in oscillation frequency due to externally applied voltage values, the memory circuit 4 stores in advance a voltage control digital code corresponding to a digital code that is an address signal indicating a voltage value. When the external voltage value changes, the address signal also changes, and the voltage control digital code is read out from the memory circuit 4 accordingly. This read voltage control digital code is supplied to the digital-to-analog converter 5 and converted into an analog signal, and then supplied to the variable capacitance element 2 via the resistor R3.
The capacitance value of the variable capacitance element 2 is controlled. Through this capacitance value control, piezoelectric resonator 1, transistor Q, resistor R
The oscillation frequency of the piezoelectric oscillation circuit made up of capacitors C□ to C4 is controlled.

In this embodiment, by changing the set value of the voltage control digital code stored in the memory circuit 4, a desired externally applied voltage-oscillation frequency characteristic can be obtained, and a linear characteristic as illustrated in FIG. 2 can be easily obtained. can be realized.

〔Effect of the invention〕

As explained above, the present invention has a configuration in which the externally applied voltage is once converted into a digital code and then converted back into an analog signal. The oscillation frequency characteristics can be set arbitrarily,
For example, an externally applied voltage with good linearity as shown in Figure 2.
This has the effect that oscillation frequency characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a characteristic diagram illustrating externally applied voltage-oscillation frequency characteristics according to the present invention, and FIG. 3 is an applied voltage-electrostatic voltage characteristic of a variable capacitance element. FIG. 4 is a characteristic diagram showing an example of capacitance characteristics, FIG. 4 is a conventional circuit configuration diagram, and FIG. 5 is a characteristic diagram illustrating an externally applied voltage-oscillation frequency characteristic according to the conventional circuit configuration. 1... Piezoelectric resonator, 2... Variable capacitance element, R1-R
7...Resistor, 01-C4...Capacitor, Q...
- Transistor, 3... Analog-digital converter, 4... Memory circuit, 5... Digital-analog converter. 1〒'6-'

Claims (1)

[Claims] In a voltage-controlled piezoelectric oscillator circuit including a variable capacitance element and a piezoelectric resonator that change capacitance according to an externally applied voltage value, an analog-to-digital converter that converts the applied voltage value into a digital code; comprising a memory circuit that stores a voltage compensation digital code corresponding to an address specified by the output digital code of the analog-to-digital converter, and a digital-to-analog converter that converts the output digital code of the memory circuit into an analog signal,
A voltage-controlled piezoelectric oscillation circuit that applies an output signal of the digital-to-analog converter to the variable capacitance element to change the capacitance.