JPS5892885A - Temperature compensating electronic clock - Google Patents

Abstract

PURPOSE:To compensate the oscillation frequency for temperature, by using a semiconductor variable capacity element in the method where the variance of the electric characteristic of a crystal due to temperature is absorbed by the variance of the capacity of a capacitor and detecting the variance of temperature to apply pulses. CONSTITUTION:The output of a temperature sensor 1 is inputted to an operating circuit 2, and information of the variance of temperature is converted to the number of pulses, the width of pulses, the level (voltage), etc. and is transmitted to a pulse generating circuit 3. The operating circuit 2 includes a storage circuit to store the temperature. The output of an oscillating circuit 6 is displayed as the time or the like on a display 9 through a circuit 7 for the normal clock function. The output of the temperature sensor 1 is converted to a signal for temperature display by a converting circuit 8 for temperature display and is displayed as the temperature on the display 9. Thus, the electronic clock where the oscillation frequency is compensated for temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature compensated electronic timepiece, and more particularly to temperature compensation of the oscillation frequency of a crystal oscillation circuit.

The eternal theme of watches is to keep accurate time. It is still fresh in our minds that when the old mechanical clocks were replaced by electronic clocks using crystal oscillators, the accuracy of clocks changed at random.

Nowadays, crystal oscillation type electronic watches are the mainstream, boasting an accuracy of ±15 seconds per month. However, the pursuit of the eternal theme still continues, and many attempts have been made to achieve high precision.

The deviation rt in the oscillation frequency of the crystal oscillator circuit is due to the temperature characteristics of the Fi crystal resonator, and the problem of minimizing changes due to temperature is the subject of improvement in accuracy. Conventional methods of temperature compensation can be broadly classified into two types. FIG. 1 shows a method of improving the temperature dependence of the oscillation frequency itself, which attempts to compensate for the change in the second #i oscillation frequency by changing the division ratio. The first method is to improve the crystal oscillator itself, use multiple crystal oscillators with different temperature characteristics, and oscillate by absorbing changes in the electrical characteristics of the crystal oscillator with changes in content t in the oscillation circuit. Various methods have been used to correct the frequency.

However, even if the crystal oscillator itself is improved, the temperature range is limited and it is unavoidably expensive, and when a plurality of crystals are used, the choice of crystal becomes difficult and expensive. Two possible ways to change the capacitance according to the temperature characteristics of the crystal are to use a trimmer capacitor with matching characteristics and to switch the capacitor depending on the temperature, but the former method requires difficult selection of the capacitor. This is too impractical, and the latter is complicated and expensive. The second method of changing the frequency division ratio by nine has a complicated circuit and is troublesome to check its operation.

The present invention attempts to compensate for the oscillation frequency, and is in the first category.As one of the methods for absorbing changes in the electrical characteristics due to the temperature of the crystal into changes in the capacitance of the capacitor, the present invention detects changes in temperature and normally Used as a replacement for the trimmer capacitor of
The purpose is to change the capacitance by applying a pulse t- to the rL9 semiconductor variable capacitance element, thereby temperature-compensating the oscillation frequency.

The present invention will be explained below based on the accompanying drawings.

FIG. 1 shows the temperature characteristics of a commonly used crystal oscillator. The temperature characteristics show a quadratic curve, and are determined empirically so that the maximum frequency occurs around 20 degrees. FIG. 2 shows the relationship between the oscillation frequency and the capacitance of the external capacitor; as the capacitance increases, the oscillation frequency decreases.

As can be seen from FIGS. 1 and 2, the capacitance of the capacitor may be increased or decreased by an amount commensurate with the change in frequency as the set temperature reaches the maximum of the quadratic curve. FIG. 3 shows an embodiment of the present invention as a digital watch with a thermometer. The oscillation circuit 6 uses a conductor-capable mass element 4 instead of the normally used trimmer capacitor, and the pulse from the pulse generation circuit 3 is applied to the injection electrode 4h. This causes the capacitance to change, thereby compensating for changes in the characteristics of the crystal oscillator 5 due to temperature. The output of the temperature sensor 1 is input to the arithmetic circuit 2, and the information on the temperature change is the number of pulses, the width,
It is converted into information such as "high voltage" and transmitted to the pulse generating circuit 3. The arithmetic circuit 2 includes a memory circuit and cannot be used unless the temperature is stored.

The output of the oscillation circuit jli6 is connected to the circuit 7 for normal clock function.
The time is then displayed on the display device 9 as a time or the like.

On the other hand, the output of the temperature sensor 1 is converted into a temperature display signal by the ninth temperature display conversion circuit 8.
Displayed as temperature.

FIG. 4 shows a cross-sectional view of the basic structure of the semiconductor variable capacitance element 4. As shown in FIG. The silicon substrate 4d is covered with 4o, n
There is a floating electrode 4c inside it. When a pulse t is applied to the puja electrode 4h, charge is accumulated in the floating electrode 4c. A change in the amount of charge results in a change in potential, and therefore, it is taken out as a change in capacitance between the electrode 4a and the silicon substrate 4d.Normally, the silicon substrate 4d is kept at a positive potential. , serves as a ground electrode.

FIG. 5 shows an example of the number of pulses and the change in capacitance when positive pulses are applied to the injection electrode 4b of the semiconductor variable capacitance element 4. The capacitance increases as the applied pulse increases. Also, the pulse height c'
t&pressure] increases, the amount of increase increases. 6th
The figure shows an example of the change in capacitance due to the number of pulses applied to the injection electrode 4b of the semiconductor variable capacitance element 4. As in the case of FIG. 5, the larger the number of pulses applied, the more , or the absolute value of the voltage], the larger the reduction in capacity is. Also, the pulse width (time) is
The larger the pulse width, the greater the rate of change.

In this way, the capacity can be determined by the number of applied pulses, width, height of the voltage, etc. The charges accumulated in the floating electrode 4c of the semiconductor variable capacitance element 4 do not escape through s(o, -6), and there is no need to periodically inject charges.

The present invention makes effective use of four semiconductor variable capacitance elements, and in principle can compensate for temperature changes as finely as possible, and has a wide range of compensation.

Since the division ratio is constant, operation confirmation is easy. The greatest effect of the present invention is that in a circuit that uses the semiconductor variable capacitance element 4 for adjusting the oscillation frequency, temperature compensation can be performed without changing the oscillation circuit. Since the clock circuit including the oscillation circuit 6 and the additional circuit for temperature compensation are completely independent, design, manufacture, and adjustment are easy. Therefore, a wide range of temperature compensation can be obtained at low cost. In electronic watches with thermometers, temperature compensation can be achieved with a small amount of additional circuitry, and the n1 effect is large.

[Brief explanation of the drawing]

Figure 1 shows the temperature characteristics of a normal crystal oscillation frequency, Figure 2 shows the deviation of the oscillation frequency from an external capacitor in the oscillation circuit, and Figure 3 shows a block with temperature compensation electronic implementation using a semiconductor variable capacitance element. Figure 4 is a cross-sectional view of the principle structure of a semiconductor variable capacitance confectionery, Figure 5 is an example of the number of pulses and capacitance change when a positive pulse is applied to the injection electrode of a semiconductor variable capacitance element. The figure is an example diagram of the number of pulses and the change in capacitance when a negative pulse is applied to the injection electrode of a semiconductor variable capacitance element. 10. Temperature sensor, 20. Arithmetic circuit, 30. Pulse generation circuit, 40. Semiconductor variable capacitance element 4G, [pole, 4b0
．． Injection electrode, 4G0. Floating '#IL pole, 4d, silicon substrate, 50. Crystal oscillator, 6. . Oscillation circuit, 701 Circuit for normal clock function, 80. Conversion circuit for temperature display, 9°, display circuit or higher

Claims (1)

[Claims] In a temperature-compensated electronic watch equipped with a temperature sensor, an oscillation circuit using a semiconductor variable capacitance element for crystal oscillation frequency correction and the semiconductor variable capacitance element K 2m , t
, 6 a pulse generation circuit for producing pulses, and a temperature detection tube of the temperature sensor; the number of applied pulses;
It consists of a t-th arithmetic circuit that converts the width, voltage, etc., and changes the capacitance of the semiconductor variable capacitance element according to the applied pulse, thereby temperature-compensating the oscillation frequency of the oscillation circuit. Features a temperature compensated electronic clock.