JPH06260839A - Current controller for temperature detecting part in digital control temperature compensation type crystal oscillator - Google Patents

Abstract

PURPOSE:To reduce a current on a temperature detecting part as keeping the A/D conversion operation of temperature data detected by the temperature detecting part normally by supplying the current to the temperature detecting part only when the data of detecting temperature is requested. CONSTITUTION:A timer in a microcomputer MC1 is reset, and a counter is started to operate, and a signal is outputted from the output port P1 of the MC1, and it is impressed to the temperature detecting part 11, then, current supply is started. Thereby, a voltage in accordance with a potential pressure ratio of thermistor TH to resistor R1, i.e., detecting temperature data is outputted from the detecting part 11, and it is digitalized by an A/D conversion function. Such operation is performed for around two mili-seconds, and after that, the signal from the output port P1 is stopped, and a control voltage value in accordance with A/D-converted temperature data is read from memory 30. The value is outputted from the MC1, and a D/A conversion part 40 converts it to an analog value, and the analog value is impressed a variable capacitive diode. When two seconds elapses, the above operation is repeated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current control device for a temperature detecting section in a digitally controlled temperature compensated crystal oscillator for correcting the characteristics of the oscillation frequency with respect to the ambient temperature of the crystal oscillator by digital control.

[0002]

2. Description of the Related Art Although a crystal oscillator is known to have high frequency stability, an analog temperature-compensated crystal oscillator has been proposed in order to achieve higher frequency stability and achieves higher frequency stability. In order to do so, a digitally controlled temperature compensated crystal oscillator (digital TCXO) has been proposed.

FIG. 4 is a circuit diagram showing a conventional digitally controlled temperature compensated crystal oscillator.

In this conventional example, a crystal oscillator 51 and an oscillator 5 are used.
0 and the frequency characteristic control circuit 3, and the frequency characteristic control circuit 3 applies an analog voltage (correction voltage) corresponding to the ambient temperature of the crystal unit 51 to the varicap diode V.
By applying to C, the varicap diode V
The capacitance of C is changed, and the oscillation frequency is controlled in accordance with this change in capacitance.

That is, the frequency characteristic control circuit 3 stores in advance in the memory 30 the correction data for correcting the characteristic of the oscillation frequency of the crystal unit with respect to the temperature change, and the crystal unit 51.
The ambient temperature of is detected by the temperature detection unit 10, the detected temperature data is converted into digital data by the A / D conversion unit 20, and this digital data is used as an address signal,
The correction data corresponding to the address signal is read from the memory 30, the read correction data is converted into an analog voltage by the D / A conversion unit 40, and the analog voltage is applied to the varicap diode VC. The capacitance of the cap diode VC is changed, and the oscillation frequency is controlled according to this capacitance change. In addition, the frequency stability of this digitally controlled temperature compensated crystal oscillator is very high compared to other oscillators.
Within the operating temperature range (for example, −20 ° C. to + 70 ° C.), the frequency change is ± 0.1 to 0.3 ppm, for example.

FIG. 5 is a diagram showing a frequency characteristic control circuit 4 in the case where the conventional example shown in FIG. 4 is circuit-configured using a microcomputer (microcomputer) MC.

In the control circuit 4 of this frequency characteristic, A
The / D conversion unit and the memory access function are built in the microcomputer MC, and the digital value output from the A / D conversion unit becomes the memory access address information, and the microcomputer MC reads the correction data from the memory 30 based on this address information. .

[0008]

By the way, the temperature detecting section 10 in the above-mentioned conventional example is composed of the thermistor TH and the resistor R1.
, And a current is constantly flowing through the temperature detecting section 10. This current is about 0.5 mA, reaching about 10% of the entire crystal oscillator, and the temperature detection unit 1
There is a problem that the current flowing to 0 is large.

In order to reduce the current flowing through the temperature detecting section 10, it is conceivable to increase the impedance between the thermistor TH and the resistor R1 which constitute the temperature detecting section 10. However, the input impedance of the A / D conversion section 20 is considered. Is relatively low, the impedance of the thermistor TH and the resistance R1 is increased, the input current of the A / D converter 20 decreases, and the A / D converter 20 does not operate normally. Therefore, there is a limit to increase the impedance of the thermistor TH and the resistor R1, and the amount of current reduction by increasing the impedance of the thermistor TH and the resistor R1 is small.

The present invention is a digitally controlled temperature-compensated crystal capable of reducing the current flowing through the temperature detection unit while maintaining the normal operation of the A / D conversion unit converting the temperature data detected by the temperature detection unit. An object of the present invention is to provide a current control device for a temperature detection unit in an oscillator.

[0011]

SUMMARY OF THE INVENTION The present invention supplies a current to a temperature detecting section only when data on a detected temperature is required.

[0012]

According to the present invention, since the current is supplied to the temperature detecting section only when the data of the detected temperature is required, it is possible to reduce the power consumption of the entire digitally controlled temperature compensated crystal oscillator.

[0013]

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

This embodiment is the same as the conventional example shown in FIG. 5 except that the output port P1 of the microcomputer (microcomputer) MC1 controls the energization of the temperature controller 11. That is, FIG. 5 shows that the embodiment of FIG. 1 is provided with the current supply control means for supplying a current to the temperature detection unit 11 only when the temperature control unit 11 needs the data of the detected temperature. This is a difference from the conventional example. That is,
Electric current is intermittently supplied to the temperature detecting unit 11, and specifically, once every about 2 seconds (about 2 msec), the temperature detecting unit 11
Is supplied with current. In FIG. 1, the current supply control means is the output port P1 of the microcomputer MC1.
Is.

The microcomputer MC1 has an output port P1.
Except for this, it is the same as the microcomputer MC, and the temperature detection unit 11
Is the same as the temperature detection unit 10 except that the current is supplied from the output port P1. The frequency characteristic control circuit 1 is the same as the frequency characteristic control circuit 3 except for the microcomputer MC1 and the temperature detector 11. That is, in the frequency characteristic control circuit 3, the correction data for correcting the frequency change of the crystal unit 51 with respect to the temperature change is stored in the memory 30 in advance, and the ambient temperature of the crystal unit 51 is detected by the temperature detecting unit 11. The data of the detected temperature is converted into digital data, and the correction data read from the memory 30 is converted into an analog voltage by the D / A converter 40 based on the digital data, and the analog voltage is converted into the varicap diode VC. The oscillating frequency is controlled according to the change in the capacitance of the varicap diode VC applied.

Next, the operation of the above embodiment will be described.

FIG. 2 is a flow chart showing the operation of the above embodiment.

First, the timer provided in the microcomputer MC1 is reset and counting is started (S1), and a signal is output from the output port P1 of the microcomputer MC1 (S2). This signal serves as a power source and the temperature detection unit 1
1 is applied, and the current supply to the temperature detection unit 11 is started. By supplying the current to the temperature detecting unit 11, a voltage (detected temperature data) corresponding to the voltage division ratio between the thermistor TH and the resistor R1 is output from the temperature detecting unit 11, and the detected temperature data (analog value) is A / It is converted into a digital value by the D conversion function (S3). These movements are about 2m
The output of the signal from the output port P1 is stopped (S4), and the value of the control voltage corresponding to the A / D converted temperature data is read from the memory 30. The value of the control voltage is output from the microcomputer MC1 (S5), the D / A conversion unit 40 converts the value into an analog value, and this analog voltage is the varicap diode VC.
Applied to. When 2 seconds have passed (S6), S1
Then, the above operation is repeated.

In the above embodiment, the temperature is detected once every about 2 seconds, and the time required for the temperature detection is about 2 msec for each time. As described above, only when the data of the detected temperature is needed, the temperature detection unit 11
When a current is supplied to the device, most of the current that has been conventionally consumed by the temperature detection unit 10 can be reduced, and therefore the power consumption of the entire digitally controlled temperature-compensated crystal oscillator can be reduced.

Further, in the above embodiment, since it is not necessary to increase the resistance values of the thermistor TH and the resistor R1 forming the temperature detecting section 11 so much, even if the input impedance of the A / D converting section is low, A / D The input current of the D conversion unit can be sufficiently secured, and the conversion operation by the A / D conversion unit can be normally maintained.

FIG. 3 is a diagram showing a frequency characteristic control circuit 2 which is another embodiment of the present invention.

In this embodiment, the current supply control means is composed of the output port P2 of the microcomputer MC2 and the transistor TR for controlling the conduction of the current, and the port P2 is operated only when the detected temperature data is required. A current is supplied to the temperature detection unit 11 by turning on the transistor TR. The resistor R2 is a transistor T
It is a resistor that regulates the base current of R.

In the above embodiment, the thermistor T
Instead of using H, the temperature detecting unit 11 may be configured using a temperature detecting element having a positive temperature coefficient of resistance.

[0024]

According to the present invention, the current flowing through the temperature detecting section can be reduced while the operation of converting the temperature data detected by the temperature detecting section by the A / D converting section is normally maintained. Play.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the above embodiment.

FIG. 3 is a diagram showing a frequency characteristic control circuit 2 according to another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional digitally controlled temperature-compensated crystal oscillator.

5 is a diagram showing a frequency characteristic control circuit 4 when the conventional example shown in FIG. 4 is circuit-configured using a microcomputer MC.

[Explanation of symbols]

1 to 4 ... Control circuit for frequency characteristics of digitally controlled temperature-compensated crystal oscillator, 10, 11 ... Temperature detection unit, 30 ... Memory, 40 ... D / A conversion unit, 50 ... Oscillator, 51 ... Crystal oscillator, MC1, MC2 ... Microcomputer, P1, P2 ... Output port, VC ... Varicap diode, TH ... Thermistor.

Claims (3)

[Claims] 1. Correction data for correcting a frequency change of a crystal unit with respect to a temperature change is stored in a memory in advance, a temperature detecting unit detects an ambient temperature of the crystal unit, and the detected temperature data is converted into digital data. Then, based on this digital data, the correction data read from the memory is converted into an analog voltage, and this analog voltage is applied to the varicap diode, and the oscillation frequency is adjusted according to the capacitance change of the varicap diode. A digitally controlled temperature-compensated crystal oscillator for controlling, comprising a current supply control means for supplying a current to the temperature detection section only when the detected temperature data is required. Current control device for temperature detector in oscillator. 2. The current supply control means according to claim 1, wherein the current supply control means is a port of a microcomputer, and only when data of detected temperature is required.
A current control device for a temperature detector in a digitally controlled temperature-compensated crystal oscillator, characterized in that a current is supplied from the port to the temperature detector. 3. The current supply control means according to claim 1, comprising a port of a microcomputer and a transistor for controlling conduction of current.
Temperature detection in a digitally controlled temperature-compensated crystal oscillator characterized in that the output signal from the port supplies current to the temperature detection unit by turning on the transistor only when data on the detected temperature is required. Current control device.