JP2975037B2 - Temperature compensated crystal oscillator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature-compensated crystal oscillator that stabilizes an oscillation frequency by compensating for a change in the oscillation frequency due to a temperature change, and particularly relates to a temperature sensor and a crystal resonator. The improvement of the thermal coupling.

(Technical Background of the Invention and Problems Thereof) In recent years, a crystal oscillator has been widely used as a reference for frequency, time, and the like. By the way, a crystal oscillator used for a crystal oscillator generally has a temperature coefficient, and the frequency changes with a change in temperature. For example, a general AT-cut crystal unit used at a frequency of several MHz to several tens of MHz has a temperature coefficient substantially in the form of a cubic curve, and its characteristics change minutely according to the cutting angle. The inflection point is around 25 ° C.

On the other hand, as the accuracy of electronic devices increases, the oscillation frequency tends to be required to be more stable even in a crystal oscillator.

As a crystal oscillator that satisfies such requirements, for example, a temperature compensation voltage is obtained according to the detection output of a temperature sensor, and this is applied to a voltage capacitance variable element connected in series to the crystal unit to finely control the oscillation frequency. There is one that is stabilized.

FIG. 3 is a circuit diagram showing an example of such an oscillator. A Colpitts-type crystal oscillator is formed using the transistor 1. A capacitor 2, a crystal resonator 3, and a variable voltage capacity element, for example, a varicap diode 4, are connected in series to the base of the transistor 1. Then, the detection value of the temperature sensor 5 is supplied to a compensation voltage generation circuit 6 to generate a temperature compensation voltage Vt, which is applied to the varicap 4 so that the generated frequency is finely varied and stabilized.

By the way, in such a temperature-compensated crystal oscillator, it is necessary to accurately measure the temperature of the crystal resonator using a temperature sensor and accurately compensate for a change in the resonance frequency of the crystal resonator due to a temperature change.

However, in the oscillator having the structure shown in FIG. 3, since the crystal oscillator and the temperature sensor are not electrically connected directly, heat conduction from the lead wire which accounts for a large proportion of heat conduction is cut off from each other. become. Therefore, the conditions of heat conduction from the lead wires of these circuit elements are different, and there has been a problem that the temperature of the crystal unit cannot be measured accurately.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and has a simple configuration, in which a temperature of a crystal resonator can be accurately measured, and thereby a temperature can be accurately compensated. It is an object of the present invention to provide a compensation type crystal oscillator.

(Summary of the Invention) The present invention relates to an apparatus for performing temperature compensation by applying a temperature compensation voltage corresponding to a detection value of a temperature sensor for detecting a temperature to a variable voltage capacity element connected to a crystal unit. It is characterized in that the vibrator is electrically and thermally connected, and that this is used as a reference potential.

Embodiment An embodiment of the present invention will be described below in detail with reference to the block diagram shown in FIG.

That is, a Colpitts-type crystal oscillator is configured using the transistor 11. A capacitor 12 and a variable voltage capacity element 13 such as a varicap and a quartz oscillator 14 are connected in series to the base of the transistor 11, and are grounded to a reference potential. And one end of the temperature sensor 15 is a crystal oscillator
14 is connected to one end on the ground side, and the other end of this temperature sensor is connected to a compensation voltage generating circuit 16 so as to give a detection value.

The compensation voltage generation circuit 16 generates a temperature compensation voltage Vt according to the value detected by the temperature sensor 15 and applies the temperature compensation voltage Vt to the cathode side of the varicap 13. A connection point between the anode of the varicap 13 and the crystal unit 14 is connected to a reference potential via a resistor 17 to form a return path of the temperature compensation voltage Vt.

FIG. 2 is a side view showing a specific configuration of a main part of the circuit diagram shown in FIG. 1, in which a quartz oscillator 14 is formed through a relatively short distance conductive pattern 19 formed on a plate surface of an insulating substrate 18. One end and one end of the temperature sensor 15 are connected in series to make an electrical connection, and the conductive pattern 19 is set to a reference potential. One end of the quartz oscillator 14 and one end of the temperature sensor 15 are also thermally connected via the conductive pattern.

With such a configuration, one end of the crystal resonator 14 and one end of the temperature sensor 15 are electrically connected in series. And, since the lead wires which occupy a large proportion as heat conduction paths of each are thermally connected in series, even if a thermal drop occurs between the two, heat conduction is performed via the lead wires and quick. To an equilibrium state. Therefore, crystal oscillator 14
Both the temperature and the temperature sensor 15 are kept quickly and always at substantially the same temperature.

Therefore, the temperature sensor 15 can accurately measure the temperature of the crystal unit 14 and can quickly follow the change, thereby performing accurate temperature compensation.

Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, the crystal resonator 14 and the temperature sensor are thermally connected via the conductive pattern 19, but both are directly connected to the mechanical device. Needless to say, a configuration may be used in which the connection is made.

(Effects of the Invention) As described in detail above, according to the present invention, the thermal coupling between the crystal unit and the temperature sensor can be kept tight, whereby the temperature of the crystal unit can be measured accurately, and It is possible to provide a temperature-compensated crystal oscillator that can quickly follow a change and perform accurate temperature compensation.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a side view showing a specific example of a main part of the embodiment shown in FIG. 1, and FIG. 3 is a conventional temperature-compensated crystal oscillator. It is a circuit diagram showing an example. 11 Transistor 13 Voltage capacity conversion element 14 Crystal oscillator 15 Temperature sensor 16 Compensation voltage generation circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-75790 (JP, A) JP-A-55-123205 (JP, A) JP-A-57-91005 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H03B 5/30-5/42

Claims (1)

(57) [Claims] A temperature compensation device for applying a temperature compensation voltage corresponding to a detection value of a temperature sensor for detecting a temperature to a variable voltage capacitance element connected to a crystal resonator to perform temperature compensation. Characterized in that one end of the crystal oscillator is electrically and thermally connected and the connection point is used as a reference potential.