JPS62283708A - Piezo-oscillator - Google Patents

Abstract

PURPOSE:To obviate such defects as an operating point of a piezoelectric vibrator changes, a series resistance becomes small, and the titled oscillator is not easily started, by constituting the oscillator so that a load capacity of a oscillator becomes large virtually at the time of start, even if a negative resistance of the oscillator is shallow. CONSTITUTION:A piezoelectric vibrator 2 is connected to an oscillator circuit 1, and an adjusting capacitor 3 is connected in series to the piezoelectric vibrator 2. As for the adjusting capacitor, that which has a comparatively small capacity is used, and the oscillator is constituted so that a capacitor 4 of a large capacity is connected in parallel to this adjusting capacitor by turning on a switch 5. The switch 5 is closed at the time of start, and the operation becomes a state that the capacitor of a large capacity has been connected in series to the piezoelectric vibrator 2, and instanteneously, the switch 5 is opened. As a result of such an operation, the virtual load capacity becomes large, and even a piezoelectric vibrator which is not easily started comes to be easily oscillated.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Industrial Application Field 1] The present invention provides a function that increases the load capacity of the piezoelectric vibrator only during startup in order to prevent oscillations that occur during startup. The present invention relates to a piezoelectric oscillator equipped with a piezoelectric oscillator.

[Prior Art 1 Piezoelectric oscillators are widely used as clock sources and signal generation sources. It is preferable to start oscillation immediately upon startup. However, the recent oscillation ml lack 1-),
-+ to 4, V=nogo) +1 to 7. i island shape 'c, +
z −J−h < many, and in order to widen the variable frequency range, the load capacity of the circuit tends to be small, so the series resonance resistance of the piezoelectric vibrator may be large, or oscillation may occur at startup depending on the conditions of the oscillation circuit. There may be problems such as not being available or it taking a long time to start up. Therefore, it has already been announced whether to select a piezoelectric vibrator with a small series resonance resistance value, increase the excavation drive on the circuit side at startup, or deepen (reduce) the negative resistance of the oscillation circuit. However, a complicated circuit is required to increase the oscillation drive or deepen the negative resistance at startup. Therefore, there was a need for a simple circuit that would oscillate without problems during startup.

[Problems to be Solved by the Invention] The present invention provides an oscillator with a means for increasing the load capacitance only at the time of start-up in the circuit so as to shift the apparent series resistance to an operating point with a small value. There is.

EConfiguration 1 of the Present Invention The present invention is a piezoelectric oscillator using a piezoelectric vibrator, which is provided with means for increasing the load capacity only at startup.

[Effects and Examples J FIG. 1 is a circuit diagram showing the principle of the present invention.

A piezoelectric vibrator 2 is connected to an oscillation circuit 1, and an adjustment capacitor 3 is connected in series with the piezoelectric vibrator 2. Adjustment capacitors usually have relatively small capacitance.

A capacitor 4 having a large capacity is connected in parallel with this adjustment capacitor when a switch 5 is turned on. During operation, the switch 5 is closed at startup, and a large capacitance capacitor is connected in series to the piezoelectric vibrator 2. Then, switch 5 is opened instantly.

As a result of such an operation, the apparent load capacity becomes large, and even a piezoelectric vibrator is likely to oscillate during startup.

Figure 3 is a graph showing the reactance characteristics and resistance characteristics of a crystal resonator to explain the present invention in detail.The reactance characteristics are the reactance characteristics on the vertical axis and the frequency on the horizontal axis. Here, the vertical axis shows the resistance and the horizontal axis shows the frequency. The characteristics shown in FIG. 3 are an example of a crystal resonator, and a crystal perturber is the most widely used piezoelectric resonator.

The actual operating point is between the series resonance point f and the anti-resonance point f2, and the resistance R at that time is at the resonance point f.

It increases from the point toward the anti-resonance point f2, and reaches the anti-resonance point r2.
It has reached its peak. As the load capacity decreases, the resistance R approaches the anti-resonance point and therefore increases. In the present invention, paying attention to this, the load capacitance is increased at startup, and the device is operated at an operating point where the resistance R becomes small.

FIG. 2 shows a circuit using the present invention, in which a variable capacitance diode is connected in place of the capacitor shown in FIG.

The capacitance value of the variable capacitance diode 6 reaches its maximum when a small voltage is applied, so apply such a voltage in advance, turn on the switch 5 at startup, or leave the switch 5 closed, and then Alternatively, a voltage may be applied only to the variable capacitance diode.

1. In the examples shown in Figures 1 and 2, mechanical switching has been described, but of course electronic switching can also be used.

Furthermore, FIG. 4 is a block diagram of a digital TCXO to which the present invention can be applied, in which IO is a sensor that detects temperature, 11 is an A/D converter that converts temperature information into a digital signal, and 12 is a A ROM that stores temperature characteristic information of the piezoelectric vibrator, 13 is an arithmetic processing unit that judges and processes signals according to the information from the sensor and the temperature information of the piezoelectric vibrator in advance according to a pre-stored program. 15 is a D/A converter that converts the signal from the arithmetic processing section into an analog signal, and 15 is a crystal excavator whose frequency can be varied by voltage or current.

The load capacity of the arithmetic processing unit 14 increases in advance at startup.
It is programmed to make it easier to oscillate.

In this example, an example was given in which a large capacitance tensor was connected to the piezoelectric vibrator in parallel with the adjustment capacitor.
The circuit of the oscillator may include a means for increasing the load capacity only at startup. Also, as a piezoelectric vibrator,
Although a crystal resonator is given as an example, not only crystal but also lithium tantalate or piezoelectric ceramic may be used.

[Effects of the present invention] According to the present invention, even if the negative resistance of the oscillator is shallow, the load capacity of the oscillator appears to be larger at startup, so the operating point of the piezoelectric vibrator changes, the series resistance becomes smaller, and the oscillator starts up. The drawback of difficulty has been resolved.

Furthermore, since it is instantaneous at startup, there is less influence on the frequency. Furthermore, in a digital TCXO, the same effect can be obtained by increasing the load capacity by setting the program in advance so that it operates according to the principle of the present invention without adding a special circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram illustrating the present invention in detail. Fig. 2 is a circuit diagram to which the present invention is applied, Fig. 3 is a graph of the actance characteristics and resistance characteristics for detailed explanation of the present invention, and Fig. 4 is a digital TC to which the present invention is applied.
A block diagram of the XO is shown.

Claims (2)

[Claims] (1) A piezoelectric oscillator using a piezoelectric vibrator, characterized in that the piezoelectric oscillator is provided with means for increasing the load capacity only at startup. (2) The piezoelectric oscillator according to claim 1, wherein the piezoelectric oscillator is a digital temperature compensated oscillator.