GB2073917A

GB2073917A - Electronic timepiece

Info

Publication number: GB2073917A
Application number: GB8111839A
Authority: GB
Original assignee: Ebauchesfabrik ETA AG; Eta SA Fabriques dEbauches
Current assignee: ETA SA Manufacture Horlogere Suisse; Ebauchesfabrik ETA AG
Priority date: 1980-04-16
Filing date: 1981-04-14
Publication date: 1981-10-21
Also published as: CH632383B; GB2073917B; FR2480956B1; JPS56159998A; DE3114356C2; JPS5848876B2; DE3114356A1; CH632383GA3; FR2480956A1

Abstract

An electronic timepiece suitable for use with different types of batteries having different voltages, and including a stepping motor 6, an oscillator 1, a frequency divider 2 and a motor control circuit 5, comprises a battery voltage detector 8 and a pulse shaper circuit 9 capable of producing pulses of different durations. The voltage detector circuit 8 controls the pulse shaper circuit 9 to cause it to supply the motor control circuit with pulses whose duration depends upon the detected battery voltage, whereby the drive pulse power will be substantially the same irrespective of the type and voltage of the battery fitted. In another embodiment trains of short pulses are used instead of single pulses and the duty cycle of the short pulses is varied. <IMAGE>

Description

SPECIFICATION Electronic timepiece The invention concerns an electronic timepiece comprising a stepping motor, an oscillator for producing a standard frequency signal, and a frequency divider coupled between the oscillator and a driving circuit for the motor for supplying power to the motor in the form of drive pulses.

In designing such a timepiece, the object is to maximise the overall efficiency, that is to say, the ratio between the mechanical power supplied by the motor for driving analog display members and the electrical power supplied by the battery, in order to obtain reliable operation of the assembly over a maximum length of time. The structure and operation of the different parts of the timepiece are designed for a given battery voltage.

The term battery is used, as in common usage, to comprehend a single cell.

The stepping motor in particular, which is the main power consumer, must be of optimised construction. The object of achieving the best ratio between the working torque and consumption leads in particular to adopting a particular gauge of wire for the coil and providing a given drive pulse power for driving the motor, taking into account the load thereon.

Therefore, if a timepiece is fitted with a battery whose voltage differs from that for which the timepiece was designed, the result is, at worst, defective operation of the timepiece, at best a reduction in its level of performance by virtue of an increase in its power consumption.

The different types of batteries which are available at the present time have voltages which differ substantially from each other. For example, a mercury battery has a voltage of 1.35 V whereas the voltages of silver or lithium type batteries are respectively 1.55 V and 3.0 V.

The user is therefore obliged to use a battery of a given type and, should the price of the different type of batteries happen to vary widely, the user would not necessarily be able to choose the most economical battery.

Moreover, regional or world-wide problems in regard to supply may arise, which prevent the user from obtaining the battery that he wants.

The object of the invention is to overcome these disadvantages.

According to the present invention, there is provided an electronic timepiece capable of being supplied by different types of battery with different voltages, comprising a stepping motor, an oscillator for producing a standard frequency signal, a frequency divider coupled between the oscillator and a driving circuit for the motor for supplying power to the motor in the form of drive pulses, and detection means for determining the type of battery with the timepiece is fitted and wherein the motor driving circuit comprises adapting means which are controlled by the detection means for so modifying the drive pulses that the power thereof maintains substantially the same value irrespective of the voltage of the battery with which the timepiece is fitted.

In a first embodiment of the invention, the adapting means modify the duration of the drive pulses.

In a second embodiment, the adapting means produce pulse trains of different cycle ratios.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a conventional timepiece, in the form of a block circuit diagram, and Figures 2 and 3 are also block circuit diagrams of two embodiments of the timepiece according to the invention.

The conventional timepiece shown in Fig. 1 comprises, for producing a time base signal, a quartz oscillator 1 supplying a standard frequency signal, for example at 32 kHz, to a frequency divider circuit 2 formed by a plurality of cascade-connected flip-flops. The time base signal supplied by the frequency divider circuit 2 is transmitted to a circuit 3 for driving the stepping motor 6. The motor 6 drives analog display members such as hands (not shown). The motor driving circuit 3 comprises a control pulse generating circuit 4 for producing, at the frequency of the output signal of the divider circuit 2 that it receives, control pulses of constant amplitude and given duration, and a motor control circuit 5 which applies the control pulses of the circuit 4 to the motor 6 in the form of drive pulses which are generally of alternate polarity.A battery 7 of given type, for example a silver type battery, supplies power to the different circuits 1, 2, 4, 5 and to the motor 6 by way of the control circuit 5.

Fig. 2 is a block circuit diagram showing a first embodiment of a timepiece according to the invention, wherein the duration of the motor control pulses is adapted to the voltage of the battery with which it is fitted, so as to ensure operation of the motor under practically optimum conditions, so that the battery 7 may be any of the most widely used types, that is to say, a lithium battery, a silver battery or a mercury battery.

The timepiece further comprises a dualthreshold voltage detector circuit 8 which is connected to the terminals of the battery. The circuit 8 compares the voltage of the battery 7 to two stored reference values which are so selected as to define three voltage ranges, each of which includes the voltage of respective one of the above-mentioned types of battery, and produces at its outputs 8, and 82. signals which represent the type of battery with which the timepiece is fitted. For example, the reference voltage values may be fixed at 1.45 V and 1.80 V. In addition, the timepiece comprises means for adapting the control pulses, comprising a pulse shaper circuit 9 which replaces the control pulse generating circuit (Fig. 1) of the conventional timepiece.The pulse shaper circuit 9 is capable of producing pulses of three different durations, depending on the signals that it receives from the detector circuit 8, at its control inputs 9, and 92, each pulse duration corresponding to a given type of battery and being substantially inversely proportional to the battery voltage with which it is associated. The power of the drive pulses which are communicated to the motor 6 then remains substantially the same, irrespective of the supply voltage. A pulse duration of 4.0 ms will preferably be selected from a lithium battery, a pulse duration of 7.8 ms for a silver battery and 9.0 ms for a mercury battery. The pulse shaper circuit 9 may comprise three elementary circuits which are similar to the pulse generating circuit 4 (Fig. 1) of a conventional timepiece and which are connected in parallel.Each of the elementary circuits can produce pulses of a given duration and can be activated individually by the signals from the voltage detector circuit 8.

It may also comprise a pulse combining circuit which is known per se and which combines the output signals of different flip-flops of the frequency divider circuit 2, to produce pulses of different durations.

The above-described timepiece will still operate under good conditions if it is fitted with a battery of a different type from the batteries for which it was designed, but the pulse duration of 4.0 ms, 7.8 ms or 9.0 ms will no longer correspond to the optimum value for the battery voltage used. In order to provide a timepiece which is capable of operating under the best conditions, irrespective of the voltage of the battery with which it is fitted, it is sufficient to increase the number of thresholds for the detector circuit 8 and to provide a control pulse shaper circuit 9 which is capable of producing a number of pulses of different predetermined durations, which number is at least equal to the number of voltage ranges defined by the thresholds of the detector circuit 8, each pulse duration being substantially inversely proportional to the battery voltage in the corresponding range.

It is also possible to maintain the power of the drive pulses supplied to the motor at a substantially constant value, irrespective of the type of battery with which the timepiece is fitted, by producing not single pulses of variable duration but trains of short pulses, the duration of the trains of pulses being fixed, and by varying the duty cycle, that is to say, the ratio between the duration of a pulse and the period of the pulses. With the inductance of the motor acting as a filter on such trains of pulses, the effect is the same as the effect of drive pulses whose duration is equal to that of the train of pulses but whose amplitude has been reduced by a factor equal to the duty cycle. This can be achieved in the manner shown in Fig. 3 which again shows the components which are common to Figs. 1 and 2, using the same references.

The circuit 9 (see Fig. 2) for shaping pulses of different durations is replaced in this circuit by a generating circuit 10 which now only produces pulses of the same duration which is to be at least equal to the optimum duration for the lowest-voltage battery with which the timepiece may be fitted, and a pulse chopping circuit 11 which is connected between the pulse shaper circuit 10 and the control circuit 5 for the motor. The chopping circuit 11 which is known per se is connected to different intermediate outputs of the frequency divider circuit 2 and at its control inputs ili and 112 receives the signals from the voltage detector circuit 8.From the pulses that the chopping circuit receives from the generating circuit 10, the chopping circuit produces trains or shorter pulses, the frequency of which may be of the order of a kilohertz (for example 1024 Hz) and the duty cycle of which depends on the type of battery used.

As in the embodiment shown in Fig. 2, it is sufficient to use a two-threshold detector and to provide for the possibility of three duty cycles ratios for the trains of pulses produced by the chopping circuit 11, or to increase the number of thresholds and the number of corresponding duty cycle ratios, if it is desired to attain optimum functioning of the timepiece, irrespective of the battery voltage.

In all cases, optimum operation is attained by selecting a duty cycle which is substantially inversely proportional to the voltage of the battery. The highest of the duty cycle ratios may be equal to one if the duration of the pulses supplied by the circuit 10 corresponds to the optimum duration for the lowest supply voltage.

It is easy for a timepiece according to the invention to be provided with a device for adapting the power of the drive pulses applied to the motor to the instantaneous load thereof. For that purpose, it is sufficient to provide a device for detecting the load and/or rotation of the motor, being connected either to the pulse shaper circuit 9 (Fig. 2) or to the chopping circuit 11 (Fig. 3). The latter comprises means for combining the data supplied by the battery voltage detector circuit and the motor rotation or load detection device and supplies the control circuit 5 with pulses or trains of pulses which are at the optimum power value, taking into account the voltage of the power source and the instantaneous load on the motor.The range of pulse durations or duty cycle ratios is then increased to hermit the above-mentionsd additional adapta ton to the motor load, irrespective of the type of battery used, taking into account the fact that certain values in respect of pulse duration or duty cycle ratio, which are provided for one type of battery and a maximum motor load, may be suitable for a battery which has a lower voltage and a lower motor load.

Moreover, it is sufficient to provide an additional lower threshold, in order for the voltage detector circuit 8 also to form a detector for detecting the end of battery life. In fact, as soon as the voltage of the battery drops and crosses the threshold of the detection circuit, which is immediately below the normal battery voltage value, the output signals of the detector circuit 8 are modified. It is therefore sufficient for the outputs which are already provided, and an additional output corresponding to the lower threshold added, to be connected to a simple logic circuit for actuating an acoustic or visual alarm device, thereby to provide the timepiece with a means for warning of the end of battery life.

Moreover, for most types of batteries, the motor continues to be supplied with power at a sufficient level, even for the few days which follow the beginning of the drop in voltage from the battery, the duration of the pulses or the cycle ratio for the train of pulses increasing in proportion as the voltage of the battery falls below increasingly lower thresholds of the detector device.

It will be appreciated that the invention is not limited to the embodiments described hereinbefore. It is possible for example for the power of the control pulses applied to the motor to be maintained at a substantially constant value, irrespective of the type of battery, and for that power possibly to be adapted for shaping pulses of different durations, and a chopping circuit, for producing trains of pulses of different durations and with a variable duty cycle.

It is also possible to produce trains of pulses with a constant duty cycle ratio but which are amplitude modulated and to vary the degree of modulation in dependence on the voltage of the battery.

Moreover, it is possible to provide means other than a voltage detector for identifying the type of battery with which the timepiece is fitted, for example, devices for detecting the presence or the absence of mechanical adapting means which would have to be used because of differences in shape and dimensions as between the different types of battery.

Claims

1. An electronic timepiece capable of being supplied by different types of battery with different voltages, comprising a stepping motor, an oscillator for producing a standard frequency signal, a frequency divider coupled between the oscillator and a driving circuit for the motor for supplying power to the motor in the form of drive pulses, and detection means for determining the type of battery with the timepiece fitted and wherein the motor driving circuit comprises adapting means which are controlled by the detection means for so modifying the same value irrespective of the voltage of the battery with which the timepiece is fitted.

2. An electronic timepiece according to claim 1, wherein the detection means comprise a voltage detector circuit which compares the voltage of the battery to at least one reference value.

3. An electronic timepiece according to claim 2, wherein the voltage detector circuit compares the voltage of the battery to two reference values defining three battery voltage ranges in which the voltages of mercury, silver and lithium batteries respectively lie.

4. An electronic timepiece according to claim 2 or 3, wherein the voltage detector circuit also comprises means for indicating the end of battery life.

5. An electronic timepiece according to any of claims 1 to 4, wherein the adapting means comprise pulse shaper means for producing pulses of different predetermined durations, each pulse duration being associated with at least one type of battery.

6. An electronic timepiece according to claim 5, wherein each pulse duration is substantially inversely proportional to the voltage corresponding to the type of battery with which it is associated.

7. An electronic timepiece according to claim 5 or 6, wherein the pulse shaper means comprise a plurality of pulse generating circuits for separately producing pulses of respective durations and which can be activated separately by the detection means.

8. An electronic timepiece according to claim 5 or 6, wherein the pulse shaper means comprise a pulse combining circuit.

9. An electronic timepiece according to any of claims 1 to 4, wherein the adapting means comprise a circuit for generating pulses of constant duration and a circuit for producing, from the constant-duration pulses, trains of shorter pulses, of different predetermined duty cycle ratios, and each duty cycle ratio being associated with at least one type of battery.

1 0. An electronic timepiece according to claim 9, wherein each cycle ratio is substantially inversely proportional to the voltage corresponding to the type of battery with which it is associated.