CH639815A - - Google Patents

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Publication number
CH639815A
CH639815A CH1074378A CH1074378A CH639815A CH 639815 A CH639815 A CH 639815A CH 1074378 A CH1074378 A CH 1074378A CH 1074378 A CH1074378 A CH 1074378A CH 639815 A CH639815 A CH 639815A
Authority
CH
Switzerland
Prior art keywords
pulse
circuit
voltage
winding
motor
Prior art date
Application number
CH1074378A
Other languages
French (fr)
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CH639815B (en
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Publication of CH639815B publication Critical patent/CH639815B/en
Priority to JP14465177A priority Critical patent/JPS6115387B2/ja
Application filed filed Critical
Publication of CH639815A publication Critical patent/CH639815A/fr

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Classifications

    • GPHYSICS
    • G04HOROLOGY
    • G04CELECTROMECHANICAL CLOCKS OR WATCHES
    • G04C3/00Electromechanical clocks or watches independent of other time-pieces and in which the movement is maintained by electric means
    • G04C3/14Electromechanical clocks or watches independent of other time-pieces and in which the movement is maintained by electric means incorporating a stepping motor
    • G04C3/143Means to reduce power consumption by reducing pulse width or amplitude and related problems, e.g. detection of unwanted or missing step

Description

The present invention relates to an electronic timepiece, in particular an electronic wristwatch.
In electronic quartz watches with analog display known from the prior art, a mechanism in the current type such as that shown in FIG. 1. The movement of a stepping motor comprising a stator (1), a winding (7) and a rotor (6) was transmitted to a gear train (2, 3,4, 5) whose mobile output actuated the display mechanism comprising for example a second hand, a minute hand and an hour hand, and may include, in some cases, still a calendar display arrangement actuated by gear trains (not visible) in flg. 1.
The construction of the circuit of such a conventional electronic watch was as follows, as shown for example in FIG. 2: The frequency of the oscillation signal of an oscillator circuit (10) was continuously divided by a frequency divider circuit (11). The signal resulting from the frequency division was converted into two signals each having a pulse width of 7.8 ms and a period of two seconds, one being phase-shifted by 1 sec from the other.
This was achieved by the use of a pulse duration combination circuit (12) and these signals were applied to the inputs (15,16) of inverting drive amplifiers (13a, 13b). Thus, alternating pulses, that is to say having a direction of current changing every second, were applied to the winding (7) and the rotor (6) magnetized according to two poles was each time driven in rotation, in steps of 180 °. An example of the evolution as a function of time of the current in the winding is shown in FIG. 3.
Generally, the duration of the drive pulses (7.8 ms in the example shown), the resistance value of the winding, the number of turns of the winding, the dimensions of each of the parts of the stepping motor , as well as other parameters conditioning the operation of the stepping motor, were established so that the stepping motor is always driven under stable conditions whatever the conditions under which the electronic watch had to function, it is that is, even when the load imposed on the gear train becomes large due to the fact that the additional calendar function operates, or that the watch is placed in a magnetic field, or that the internal resistance of the battery supplying the watch was experiencing an increase due to low temperature. Thus, the watch constantly used the relatively high power necessary to ensure its operation under the aforementioned unfavorable conditions, even when, under normal operating conditions, such a high mechanical output torque was not required from the stepping motor. This made it impossible to truly reduce the total power consumption of an electronic watch to a minimum.
As an object of the prior art, however, the watch described in the description FR-A-2 200 675 has been cited, which is an electronic watch comprising a circuit for detecting current spikes in the stepping motor, which makes it possible to detect whether the engine is running or not. A pulse delivery circuit is then conditioned to deliver a drive pulse the duration of which is sufficient to run the engine. However, it is noted that this presentation FR-A-2 200 675 discloses an arrangement in which the detection of the load is carried out by a resistance during the very application of the drive pulse. In addition, regardless of the very moment when the induced voltage is detected, things are such, in the subject of this French presentation, that the resistance in question remains in series during the application of the drive pulses, hence some loss of energy.
From this French presentation, it can be said in any case that it does not disclose a detection of the charge, which more or less amounts to a detection of the condition of rotation or non-rotation, which would occur “during a short pulse of
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detection, after the cessation of the normal training pulse ”.
However, it appears that a detection which takes place at the same time as the drive pulse is subject to the vagaries of the stroke made by the rotor of the motor, which stroke can be more or less hampered depending on the surrounding conditions, and it is to say the least, it is difficult to distinguish the current curve corresponding to a rotation which has just barely intervened, but with difficulty, from the current curve of a rotation which has almost intervened, but has finally aborted. The object of this French presentation therefore does not ensure the improved reliability which should be the prerogative of a method using a “short pulse duration of detection after the normal training pulse has stopped”.
Reference was also made to the description JP-A-52-119 267, which proposes, in an electronic watch, the delivery of a correction pulse of adequate duration, in the event of non-rotation of the engine. However, the means recommended in this case for detecting the rotation or non-rotation of the motor, means which are, moreover, not very explained in the English extract of this Japanese document, in any case do not include a "short duration impulse detection subsequent to the normal drive impulse "and therefore do not provide more than the object of the French presentation previously mentioned, the particularly improved reliability which was discussed above.
The present invention aims to eliminate the drawbacks and inadequacies of the prior art, its aim being to provide,
in an electronic watch with a stepping motor, an arrangement which is particularly reliable and free from the drawbacks which plagued the devices according to the prior art, allowing a reduction in consumption going truly up to the minimum possible energy consumption while being without danger as for the impeccable functioning of the watch.
According to the invention, this object is achieved by the presence of the characters set out in the first claim.
The characteristics set out in the subsequent claims allow this object to be achieved under particularly advantageous conditions from the point of view of construction, structure and practicality of construction.
With the watch according to the invention, the duration of the pulses is constantly adapted to the minimum required in correspondence with the load conditions encountered by the stepping motor.
The appended drawing illustrates, by way of example and compared with what the prior art knew, embodiments of the subject of the invention. In this drawing:
fig. 1 schematically represents a display mechanism, of a known general type, for an electronic watch with analog display,
fig. 2 shows an example of constitution. Of the circuits of a conventional electronic watch with analog display, FIG. 3 is a diagram showing an example of the waveform of the drive current of the stepping motor of an electronic watch with a conventional analog display,
fig. 4 represents an example of a drive pulse train presented in an electronic watch with stepping motor of the particular type according to the invention,
FIGS. 5, 6 and 7 schematically represent a stepping motor under different operating conditions, to explain the principle of the operations for detecting the rotation or non-rotation of the motor,
fig. 8 shows an example of the waveform of the drive current in the stepping motor according to FIGS. 5 to 7,
fig. 9 is a diagram of a drive circuit for a stepping motor, this diagram being presented only to explain the principle of detecting the rotation or non-rotation of the stepping motor,
fig. 10 is a diagram representing detection pulses applied to the circuit of FIG. 9 and illustrating two different cases of operation of the detection circuit,
fig. 11 is a diagram illustrating the relationship between the angle of rotation of the rotor and a voltage induced after the drive pulse,
fig. 12 diagrammatically represents the drive circuit of a stepping motor for producing the rotor movement detection circuit according to another principle,
fig. 13 is a diagram similar to that of FIG. 11, but relating to the circuit shown in FIG. 12,
fig. 14 is a diagram representing the waveform of the induced voltage and of the current in the case of different durations of the drive pulse,
fig. 15 is a diagram illustrating the relationship between the duration of the drive pulse and the peak value of the voltage induced after this pulse,
fig. 16 is a diagram representing the waveform of the voltage induced at the moment when the movement of a rotor is detected,
fig. 17 is a block diagram of an embodiment of an electronic watch with digital display according to the invention,
fig. 18 is a diagram showing the distribution over time of the pulses required for the embodiment of the watch according to FIG. 17,
fig. 19 represents the diagram of an embodiment of the drive and detection circuits in an electronic watch of the type according to the invention,
FIGS. 20a and 20b show, respectively in the form of a detailed diagram and in the form of a block diagram, the constitution of a comparator circuit for the embodiment of the watch according to the preceding figure,
FIGS. 21a and 21b are explanatory diagrams of the operating mode of the comparator,
fig. 22 represents, by a block diagram, the constitution of a control circuit for the watch according to the invention,
fig. 23 shows a diagram similar to that of FIG. 19, for another embodiment, and FIG. 24 shows the diagram of a circuit providing a constant voltage.
We will not return to Figs. 1 to 3, illustrating the prior art, which have already been briefly considered in the introduction. We will now consider in detail, in conjunction with FIGS. 4 et seq., An electronic watch, typically an electronic wristwatch, with analog display by stepping motor provided with a particular drive system, in accordance with the invention, ensuring a significantly reduced power consumption.
First of all, an example of the operating principle which is the basis of the invention should be presented, which will be done in conjunction with the curves a, b and c of FIG. 4.
The drive pulses of the stepping motor, as they appear in the electronic watch according to the invention, comprise two types of pulses, namely: normal drive pulses and correction drive pulses . These pulses are, if necessary, applied to the stepping motor in the order comprising first the normal drive pulse and then the correction drive pulse. Note that the correction drive pulse is, as a rule, applied to the stepping motor when it cannot be s
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caused to move in rotation by the normal drive pulse. Since the fact that a correction drive pulse must be applied to the stepping motor indicates that this motor could not have been rotated by the normal driving pulse which was first applied to it, in such a case, the duration of the next normal pulse should be increased, by a predetermined additional duration, to allow it to easily move the rotor of the stepping motor. Conversely, the duration of the normal drive pulses is made shorter, by an amount of predetermined duration, when the application of only the normal drive pulses to the stepping motor caused the latter to move. correctly for a number of steps.
In the context of the above-mentioned operating mode, the duration of the normal driving pulse Pj corresponds to the minimum duration which is necessary each time, taking into account the load conditions, to drive the stepping motor. In this way, the power consumption of the stepping motor is reduced to a minimum. For example, as shown in fig. 4a, the kind of operation mentioned above first causes the duration of the normal drive pulse Pj to be reduced from 3.9 ms to 3.4 ms. Assuming that the stepping motor can still be moved adequately under these conditions, the above-mentioned operating mode brings the duration of the pulse Pj to the even smaller value of 2.9 ms, after the stepping motor has was driven in rotation, over a number of steps, by normal drive pulses having a duration of 3.4 ms. Assuming now that, under these conditions (with a pulse of 2.9 ms) the motor is no longer able to be rotated, a condition of non-rotation of the rotor will be detected in the context of the above-mentioned operating mode, so that a correction pulse P2 will be quickly applied to the motor, after which the normal drive pulse P! will be reduced to the duration of 3.4 ms. Then, the duration of the normal training pulses will be maintained at 3.4 ms, with repetition of the operations previously mentioned. If subsequently, for some reason, the stepper motor falls into conditions such that it can no longer be rotated by the application of a normal drive pulse of 3.4 ms duration , the condition of non-rotation of the rotor is again detected using a rotor motion detection circuit. Things then appear as shown in fig. 4b, a correction pulse is quickly applied, after which the duration of the normal training pulse is increased, for subsequent steps, to 3.9 ms. Then, when this pulse width becomes large enough to move the stepping motor again, the duration of the normal drive pulse is again reduced to 3.4 ms, as illustrated in FIG. 4c, after a certain number of steps have been taken under the control of normal training pulses lasting 3.9 ms.
The operating principle according to the invention having now been explained, the principles on the basis of which it is possible to detect the rotation or non-rotation of the rotor should be explained further, this detection playing a role. important role in the realization of the invention. Although the movement of a rotor can be detected using an external element, such as a mechanical switch or a hollow element as a semiconductor, it is very difficult to incorporate such a mechanism when one has only a small volume available, as for example in the case of an electronic wristwatch. We will therefore now describe two different motion detection principles (as an example for detecting the movement of the rotor required by the present invention) which do not require any external element and which can be achieved by establishing a circuit. detection on the printed circuit board itself which includes the oscillator circuit, the frequency divider circuit, the drive circuit, etc.
The first method uses the fact that the waveform of the drive current changes according to the position of the rotor, when a one-piece stator is used. In fig. 5, the reference sign 4 represents a stator in one piece (or in a body) on which saturable magnetic portions 17 are established. These portions are magnetically coupled to a portion of the magnetic circuit around which the winding 17 is wound. In this stator, notches 18 are provided to determine the direction of rotation of the rotor 6 which is magnetized in the radial direction, in a bipolar fashion. . Fig. 5 shows the situation just before a current is applied to the winding 7. In this case, as no current in the winding magnetizes the stator, the rotor is stopped in a position such that an angle of approximately 90 ° is found established between its line of magnetic poles and the direction of the notches 18. If, in this situation, a current is caused to flow through the winding 7, in the direction indicated by an arrow, magnetic poles are generated in the stator, as shown in fig. 5, and the rotor 6 begins to move clockwise, due to a repelling action. When the current situation through the winding 8 is interrupted, the rotor 6 comes to a stop in the state diametrically opposite to that shown in FIG. 5. Then from this, by circulating current in the opposite direction through the winding 7, the rotor 6 is caused to continue its rotation clockwise, again by half a turn.
If the stepper motor is provided with a stator in a body, having saturable portions 17, the current diagram will include a portion of gradual increase, as shown in fig. 3, when a voltage (and a current) is applied to the winding 7. This relatively small increase results from the fact that the magnetic resistance (or reluctance) of the magnetic circuit, seen from the winding 7, is very low as long as the saturable portions 17 of the stator are not yet saturated, and it follows that the time constant x of the series circuit formed by the resistor R and the winding becomes larger. This is explained by the following equation:
t = L / R, L = N2 / Rm which gives x = N2 / (R x Rm7
equation in which L represents the inductance of the winding 7, N represents the number of turns of the winding 7, and Rm represents the magnetic resistance (or reluctance). When the saturable portions 17 of the stator 1 become saturated, the permeability of these saturated portions becomes equal to that of air, so that the magnetic resistance Rm decreases and the time constant x of the circuit becomes lower, as illustrated in fig. 3. As a result, the current waveform suddenly has a steep slope. Since the saturation time also depends on the conditions of the magnetization of the motor, the saturation time is naturally longer, as a corollary with the increase in the current level over time, when the pulse is cut off. Thus, since the magnetization time becomes longer after the correction pulse has been applied to the stepper motor, a magnetization pulse, to cancel the aforementioned effect, can be applied to the stepper motor. Detection of rotor movement, i.e.
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the detection of the fact that the rotor has actually rotated or not, results in this example from the difference in time constants of the series circuit formed by the resistor and by the winding. We will now explain, in conjunction with the drawing, the reason why this difference in time constant occurs.
Fig. 6 represents the situation of the magnetic fluxes at the moment when the current begins to circulate in the winding 7, the magnetic poles of the rotor 6 being still located at the place where they are when this rotor begins to move, that is to say say that the rotor is still practically in the same position as in FIG. 5. A magnetic flux represented by line 20 is produced by the permanent magnetization of the rotor 6. In practice, a small part of this flux passes through the winding core, but this part of flux is negligible. The magnetic fluxes 20a and 20b are directed as shown by arrows in FIG. 6. The saturable portions 17 are, in most cases, not yet saturated by this flux coming from the proper magnetization of the rotor. When under these conditions, the current is caused to flow through the winding 7 in the direction marked by arrows, so as to cause a rotation of the rotor clockwise, magnetic fluxes 19a and 19b are produced by the winding 7 and reinforce the magnetic fluxes 20a and 20b, due to the proper magnetization of the rotor 6, in the saturable portions 17a and 17b, so that these saturable portions 17 of the stator are highly saturated and that one begins to circulate the current through the winding 7 in the direction marked by the arrow. Thereafter, a magnetic flux having sufficient force to cause rotation of the rotor 6 is produced in the stator and in the rotor 6, however this situation has not been taken into account in FIG. 6 because the interesting phenomena here are those which occur at the start of the application of the current, before the rotor has actually rotated. The shape of the current through the winding at this moment is represented by the curve 22 of FIG. 8.
Fig. 7 shows the flow situation which occurs during a subsequent impulse directed in the opposite direction, assuming that the rotor did not, for some reason, rotate during the previous impulse and that it is therefore still in the same position as it was originally. To rotate the rotor, in the case of fig. 7, circulate the current in the winding 7 in the same direction as above, that is to say in the direction shown by the arrows in FIG. 6. However, since the current is applied alternately in both directions to the winding 7, at each revolution, conditions similar to those of FIG. 7 will be established if the rotor 6 could not move in rotation during the previous pulse. In this case, since the rotor has remained in the same position, the direction of flow due to the magnetization of the rotor has remained the same as in FIG. 6. On the other hand, since the current is caused to flow in the other direction through the rotor, the direction of the flow due to the passage of the current in the winding is the reverse of what it was in the case of fig . 6. The magnetic fluxes 21a and 21b therefore oppose the magnetic fluxes 20a and 20b in the saturable portions 17a and 17b of the stator 1. To bring these portions to saturation, it will therefore take more time. This situation is represented by the curve 23 in FIG. 8.
An example of the means for detecting the positioning of the rotor, using the previously mentioned phenomena, is illustrated in FIGS. 9 and 10, which do not correspond to the object of the invention but are provided only for explanatory purposes.
Fig. 9 shows a way of establishing the detection circuit for the rotor, this circuit being formed by adding to
a drive circuit of conventional type, comprising for example reversers formed by MOS gates 24, 25, 26 and 27, detection gates 28 and 29, a detection resistor 30, a transmission gate 31 for charging a capacitor, a capacitor 33 and a voltage comparator 32. It is noted first of all, as it corresponds to normal driving operations, that the current is caused to flow by the channel represented by line 34, and the winding 7 is excited, so that the rotor is normally caused to rotate half a turn. When this rotation is practically finished, a first detection pulse is applied to the winding 7 through a path represented by the line in dotted lines 35, during a very short time interval (approximately 0.5 to 1 ms) then, after that , a second detection pulse, of similar duration, is applied to the winding via the channel represented by the dashed line 36.
Now making sure that the normal drive pulse has actually caused the rotor to move one step, the relationships between the magnetic poles of the rotor and the magnetic poles of the stator at the time when the first detection pulse is applied at winding are the conditions under which the rotor could be driven again by one step, that is to say the conditions illustrated in FIG. 6. The portion of increase in the waveform of the current at this time consists of a curve which very quickly has a steep slope, as shown by curve 22 in FIG. 8. When the second detection pulse is applied to the winding, the rotor is always in the same position it occupied when the first detection pulse was applied, since, due to the very short duration of the detection pulse and due to the presence of the resistor 30, of high value, in series with the winding during the detection pulse, the latter cannot cause the rotor to move. Thus, during the second detection pulse, the directions of the magnetic excitations are opposite, and the position relationships between the magnetic poles of the rotor and the magnetic poles of the stator are found to correspond to that shown in FIG. 7. In this case, the portion of increase in the shape of the current is established in a manner having a relatively long rise time, that is to say a lower slope, in correspondence with what the curve 23 of fig. 8. However, given the presence of the detection resistor 30 in series with the winding at the time of the application of the detection pulse, this shape does not correspond exactly with the waveform of FIG. 8, except for the character of the rising portion.
Thus, the fact that the potential Vs1 produced by the first detection pulse reaches a level higher than that of the potential Vs2 produced by the second detection pulse, as shown in FIG. 10a, can be observed by observing the voltage present at the terminals of the detection resistor 30.
When the motor could not be rotated by the application of the last normal drive pulse, this rotor therefore being returned to its position resulting from the penultimate normal drive pulse, the relationships between the magnetic poles of the rotor and the magnetic poles of the stator at the time of the application of the first detection pulse and at the time of the application of the second detection pulse, occur in reverse order to those that occur when the rotor was able to rotate. This is illustrated by curve b in fig. 10, where we see that the voltage developed across the detection resistor 30 reaches a value Vs2 (second detection pulse) greater than the value Vs! (first detection pulse).
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It is therefore understood that it is possible to detect the fact that the rotor has or has not carried out its normal movement during the application of the last normal drive pulse, simply by comparing the values “V5l” and “Vs2”. In the explanatory example considered, the voltage difference between the potentials Vs1 and Vs2 amounts to approximately 0.4 V. Such a voltage value can easily be detected. To carry out the detection operations in question, it is possible, for example, as is the case of the circuit shown in FIG. 9, use a transmission gate 31 which is set to the on state during the first detection pulse, so that the capacitor 33 is charged by the potential VsI, this potential Vsl, memorized on the capacitor 33, being, at moment of the second detection pulse, compared with the potential Vs2 then generated at the terminals of the detection resistor 30. This voltage comparison is carried out in a voltage comparator 33 which makes it possible to recognize which of the two potentials was higher.
These are the explanations concerning a method for detecting the movement of the rotor which is advantageous in itself but which does not yet correspond to the subject of the invention.
We will now describe the principle of a method of detecting the movement of the rotor, in which the waveform of the voltage produced in the winding by the free oscillation of the rotor is used after the rotor has been driven. This method, explained in conjunction with Figs 11 and following, can be explained as follows:
Fig. 11 shows the relationship between the angle of rotation of the rotor and the waveform of the voltage produced in the winding, which develops across a resistance of high value, for example of the order of 10 K ohms, connected, following the application of the pulse, to the two winding connections, so as to form a loop.
During the time interval "Tj", the drive pulse is still applied to the winding and the high value resistance (detection resistance) is not yet connected in circuit, so that no form of voltage does not appear on the diagram. The voltage during the time interval "T2" is the voltage which is produced in the winding by the rotational and vibrational movements of the rotor, after the drive pulse. Since the voltage waveform during the time interval "T2" varies according to the load conditions and the drive conditions of the stepping motor, the detection of these voltage waveform variations makes it possible detecting the movement of the stepper motor.
Fig. 12 shows an example of a detection circuit using this principle. The doors 24, 25, 26, 27, 28 and 29, the detection resistor 30 and the winding 7 are established in the same manner as in the case of FIG. 9, but the input signal in the case of FIG. 12 is different from what it was in the case of FIG. 9. The junction point (not grounded) of the detection resistor 30 is connected to the input of a voltage detector 40 having a predetermined threshold. When the normal drive pulse is applied to the winding by the channel represented by the solid line 41, the winding is excited and the rotor is driven. After that, during the movement of the rotor, a switching action is carried out intermittently between the condition in which the two ends of the winding are grounded by a channel 42 which establishes a short circuit and the condition in which the loop closed also includes the detection resistor 30, which, as we have seen, is of high value. The effect of this intermittent switching will be explained later. First of all, to simplify the explanations, we will consider the condition in which the closed loop, established just after the motor has received its drive pulse, includes the detection resistor 30. FIG. 11 shows the voltage waveform produced at the terminals of the detection resistor 30 under these conditions. For the curve of fig. 11, the engine is admitted as being practically not loaded. Fig. 13 shows on the other hand how the waveform is presented, as a function of the angle of rotation of the rotor, in the case of a maximum load of the stepping motor and in the case of an overload of the stepping motor , respectively by curves "a" and "b". Since the rotational speed of the rotor in case "a" of the maximum load conditions is low and since the amplitude of the vibration which occurs after a step has been taken is also low, the waveform of the voltage produced becomes subject to less irregularity. In the overload condition "b", the peak voltage is produced in the negative direction when the rotor returns to its original position. However, the waveform of the voltage produced generally has less ripples, with the exception of the previously mentioned portion.
Although there are many ways in which one can detect whether the rotor has rotated using the waveform of the voltage produced, the method in which the condition of the rotor is detected by detecting the existence of the tip “P” of the waveform allows the use of a simplified circuit and gives complete security as for the detection of the situation of the rotor. According to this method, the circuit must recognize if the potential across the detection resistor 30 reaches a predetermined potential value during a predetermined period of time following a few milliseconds after the application of the drive pulse. The rotation or non-rotation of the rotor is determined according to the presence or absence of this point "P".
However, according to this method, it can happen that the rotor is considered as not having carried out its rotation despite the fact that it has effectively carried out this rotation, but under conditions of maximum load, as illustrated by FIG. 13a. This possibility of error, however, goes in the direction of safety since this principle is used, in accordance with the invention, together with that of the application of a correction pulse. In fact, since the correction pulse which will then be applied will have the same polarity as that which the circuit will have considered to be inoperative, no additional (undesirable) rotation of the rotor will be likely to occur,
Fig. 14 shows the waveforms of the voltage produced in the winding after the drive, in the case of different normal drive pulse durations. It can be seen in this figure that when the duration of the normal drive pulses becomes greater than a certain predetermined value, the peak value in the voltage waveform produced becomes lower, as shown in "P4" , despite that we are in the condition of no load and normal rotation. To explain this fact clearly, fig. 15 represents the pulse duration of the normal drive pulses on the abscissa, and the peak value of the induced voltage on the ordinate. Curve 45 corresponds to the condition in which the closed loop is produced by continuously connecting the detection resistance in series with the winding after the drive pulse, as previously described, and curve 46 represents the case where the detection resistance is connected only intermittently in the closed loop, as will be described later.
First of all, the effect obtained by the continuous connection of the detection resistor in series with the winding after the application of the normal drive pulse will be
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Explain. In a conventional drive circuit, such as that shown in FIG. 2, to implement the drive operations using two inverters, the two terminal connections of the motor are short-circuited using a low value resistance, established in the control stage, when the engine is in non-moving condition. This is how a current flows in the winding under the effect of the developed voltage passing through the short-circuit branch 42 shown in FIG. 12. This current causes Joule losses in the resistor and in the drive transistor, which results in the mechanical oscillations of the rotor being damped. When the closed loop is established along track 43 shown in FIG. 12, in order to detect the induced voltage, the current flowing through the damping circuit is low, compared to the case previously considered, since the detection resistor 30 has a high impedance added to the drive circuit in which it is included.
Thus, an alternating permutation action between the two types of circuit, at the time of the braking operation of the rotor causes rapid changes in the current in this circuit. However, since the inductance of the motor winding is large, the current in the circuit cannot follow these changes. It follows that the circuit has the response characteristic of a first time delay having the time constant "x" = L / R ", which depends on the inductance" L "of the winding and the resistance" Rd = (R + R 30) "of the braking circuit. The value of the voltage produced across the detection resistor 30 at this time is approximately 0 V when the braking circuit is established by using the channel 42 shown in Fig. 12, while, at the time of switching on track 43, the winding 7 acts so as to maintain as much as possible the current flow which was established during the braking operation through track 42 As a result, a high voltage value is developed for an instant at the terminals of the detection resistance 30, of high value, then this high voltage value is reduced in correspondence with the time constant "t".
Fig. 16 shows an example of the voltage waveforms produced across the detection resistor 30 under these conditions. It is a peculiarity of the method described here to use the voltage induced by the motor at the time of the braking action, which is only possible by means of changes in the value of the resistance inserted in the circuit. in the engine brake system. This method is also distinguished by the fact that the maximum value of the peak voltage goes beyond the voltage value (approximately 1.5 V of the power supply of the drive circuit at the time when the detection resistor is connected only intermittently, as illustrated by curve 46 in Fig. 15, while the maximum value of the peak voltage is approximately 0.8 V, at most, when the voltage produced is continuously detected, as shown in the Curve 45 in Fig. 15. As a result, it is very easy to detect such a voltage.It should also be noted that, as shown in Fig. 14, when the duration of the normal pulse increases to some extent, the de-undulation of the voltage produced becomes easier.
Two principles have been described according to which a circuit for detecting the movement of the rotor can operate. The first of these principles is only an illustrative example not falling within the invention, the second, although not being the main essence of the invention, can be associated therewith without difficulty. In fact, the main character which distinguishes the present invention lies in the fact that the normal pulse duration is suitably increased or decreased depending on the operating conditions of the rotor. Therefore, although the constitution of the stepping motor and of the detection circuit responsible for detecting the rotations thereof are important elements, their constitution is not here a primordial question.
We will now explain an embodiment of what constitutes the essence of the present invention.
Fig. 17 shows a block diagram of an electronic watch with analog display of the particular type according to the invention.
This figure shows an oscillator circuit 90 in which a quartz vibrator with a vibration frequency of 32,768 Hz is conventionally used. A frequency divider circuit 91, consisting of fifteen flip-flop stages connected in cascade, provides a time signal to one second by dividing the frequency of the oscillator.
We see in 97 a reset (or reset time) input for the watch, all the stages of the frequency divider circuit being reset to zero by the application of a signal to this reset input. zero. A combination pulse forming circuit 92, in which the desired pulses are established by combining signals from different flip-flops of the frequency divider circuit 91, includes NAND gates and NOR gates to perform the functions of " timing ”shown in fig. 18. As such a combination pulse-forming circuit can be easily achieved by using logic circuit elements, the diagram of this combination pulse conditioning circuit has been omitted.
Fig. 30 19 shows the diagram of the drive circuit 94 and the detection circuit 95 of FIG. 17, the input connection T! corresponding to the output condition of the control circuit 93 of FIG. 17. It is only when the input Tx is at the "high" logic level that the output connection for the stepping motor 96 is at the "high" level. As the other output connection is at the “low” level, a current flows in the stepping motor 96. The output signal from the control circuit 93 shown in FIG. 22 is applied to the input T2 of the circuit of FIG. 19. Then -40 that, when the input T2 is at the “high” level, the signals Q and (J of the flip-flop 100 are applied to the gate input EX-OR during a period, and that therefore the outputs of these EX-OR gates are then logically inverted with respect to the outputs of the flip-flop 100, it is possible to reverse the direction of current flow in the motor.
In this embodiment, the motor is driven also using a correction pulse P2 when the motor cannot move in rotation by the sole application of the normal drive pulse, and an im-50 pulse P3, opposite to pulse P2 is then applied again. The reason is that, in a one-piece stator motor, the magnetic saturation time of the magnetically saturable portions at the time of the application of the next drive pulse becomes 55 longer when an operation correction drive was performed by a P2 pulse, which would reduce the effective pulse duration. By applying the opposite polarity pulse P3 to the winding of the stepping motor 96, when a correction drive operation has been performed by the application of a pulse P2, the stator is already magnetized in the direction corresponding to the next drive pulse, so the time required to saturate the saturable portion of this one-piece stator can be reduced. 65 The output T3 of the control circuit 93 of FIG. 17 is connected to the input T3 of the circuit of FIG. 19 and the operations for detecting the rotation condition are carried out using this pulse, according to the above method
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duly mentioned, in which the voltage produced after the rotation of the rotor is used.
When the pulse P0, having a period of one second, is applied to the flip-flop 100, the latter delivers a signal having a frequency of Vi Hz, its output Q being connected to an input of the gate EX-OR 121 and its output (J being applied to an input of door EX-OR 122. The other input of each of these doors EX-OR 121 and 122 is connected to input T2. The output of door EX-OR 122 is connected to doors NOR 102 and 103 and the output of door EX-OR 122 is connected to doors NOR 104 and 105.
The output signal from the inverter 101 is applied to the NOR gates 103 and 104 and the input T3 of the control signal 93 is connected to the NOR gates 102 and 105 via the inverter 120.
The output of NOR gate 102 is connected to the first input of NOR gate 106 and to an N-type MOS-FET transistor 115. The output of NOR gate 103 is connected to the input of a MOS-FET transistor type P 113, used for driving the stepping motor, via the inverter 123, as well as at the second input of the NOR gate 106. The output of the NOR gate 104 is connected to the input of the P-type MOS-FET transistor 118, used to drive the stepping motor, via the inverter 124, and is also connected to the first input of the NOR gate 107. The output NOR gate 105 is connected to the input of N-type MOS-FET transistor 116, as well as the second input of NOR gate 107. The output of NOR gate 106 is connected to the input of transistor MOS-FET type N 114, used to drive the stepping motor, and the NOR gate 107 is connected to the MOS-FET type N 119 used to drive the stepping motor s.
The positive supply voltage VDD supplies the energy input on the positive side, on the source electrodes of the P-type MOS-FET transistors 113 and 118.
The source electrodes of the N-type MOS-FET transistors 114 and 119 are grounded, the drains of the P-type MOS-FET transistor 113 and of the N-type MOS-FET transistor 114 are connected to each other. other and form an output connection for a connection of the winding of the stepping motor 96 at the same time as a connection supplying the drain of the N-type MOS-FET transistor 115 used for detection.
The drains of the P-type MOS-FET transistors 118 and N-type 119 are connected together and form the other output connection for the winding of the stepper motor, together with the drain connection for the MOS-FET transistor 116 of type N used for detection.
The sources of the N-type MOS-FET transistors 115 and 116 are connected together and are also connected to one terminal of a detection resistor 117, the other terminal of which is grounded.
The source link point of N-type MOS-FET transistors 115 and 116, and resistor 117, is connected to the positive input of comparator 110. The signal appearing at this connection point, called T0, is the signal which indicates whether the rotor has rotated or not. A circuit composed of resistors 108 and 109, comparator 110 and MOS-FET transistor 111 of type N forms the detection circuit 95. If the detection signal T0 can be detected using the threshold voltage of a gate circuit CMOS, you can simply use a CMOS inverter.
One end of the resistor 108 is connected to the positive power source VDD, and its other end is connected to the resistor 109. In this case, the point where these two resistors meet is connected to the negative input of the comparator 110, The other end of the resistance
109 is connected to the drain of the MOS-FET transistor 111 of type N, for the inhibition of the detection operations, the connection with the ground potential being effected only through the source of this MOS-FET transistor 111. The comparator 110 ground connection is also connected to the drain of this N-type MOS-FET 111 transistor and it is also grounded only when the latter is conductive.
The output signal of the comparator 110 is present on an output connection 112, as signal T4, and it is applied to the control circuit 93.
The comparator used in the detection circuit 95 according to the present invention is constructed using CMOS elements, and its operation will now be briefly explained in conjunction with FIG. 20.
Fig. 20a shows the detailed diagram of this comparator while FIG. 20b represents it in the form of a block diagram. A connection 164 supplies the positive (or additive "+") input of this comparator while an input connection 165 supplies its negative (or subtractive "-") input. The output of the comparator is present on an output terminal 166 and an input T3 constitutes the “operating authorization” input.
The functions of this comparator circuit are shown in Table 1 below
Table 1
positive input negative input self-input
"+" "-" risat. operating
- 0 -
V +> V_ 1 "H"
V + <V_ 1 "L"
The indication VD0 represents the positive supply connection, supplying the sources of the MOS-FET 160 and 162 transistors, P type. The control electrode and the drain of the MOS-FET 160 transistor P type are connected together and are also connected to the control electrode of the P-type MOS-FET 162 transistor, as well as to the drain of the P-type MOS-FET transistor 161.
The drain of the P-type MOS-FET transistor 162 is connected to the drain of the N-type MOS-FET transistor 163, this point also forming the output connection 166. The control electrode of the MOS-FET transistor 163 R is connected to the input 165 and the source of this transistor is connected to the drain of the MOS-FET transistor 111 of type N, at the same time as the source of the MOS-FET transistor 161 of type N. The source of the MOS-FET transistor 111 of type N is grounded and its control electrode is connected to input T3.
It should also be noted that the electrical characteristics of the MOS-FET transistor 161 of type N are identical to those of the MOS-FET transistor 163 of type N and that, moreover, the electrical characteristics of the MOS-FET transistor 160 of type P are identical to those of the P-type MOS-FET 162 transistor.
We will now explain the operation of the comparator that we have just described. When the authorization input connection T3 is at the “low” level, the MOS-FET transistor 111, of type N, is made non-conducting and the comparator is not in operation. When the input connection T3 goes to the “high” level, the N-type MOS-FET transistor 111 is turned on and the comparator is then in working order. Since, in this embodiment, the threshold voltage for the signal to be detected is obtained in the voltage divider circuit composed of the resistors s
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IO
108 and 109 which is crossed by a current only during the time when the comparator is also in service, a significant energy saving is achieved. Thus, in this embodiment, the circuit is arranged in such a way that current flows only when the pulse T3 passes to the “high” level, given the operating mode of the MOS-FET transistor of the Nili type. This also allows a notable saving of energy, as for the operation of the comparator circuit.
When an input voltage W1 is applied to connection 164, the potential and the current appearing at junction point 168 are established, as a function of this voltage V \, in the manner represented by part a of FIG. 21.
On the latter, the voltage Vi6g is the potential on connection 168 and the current indicated II6g is the current flowing through this connection 168.
Since the potential V168 is applied to the control electrode of the P-type MOS-FET transistor 162, its saturation current is equal to the current value I168.
This condition is represented by part b of FIG. 21.
On the other hand, assuming that the voltage applied to the input 165 is V2, the saturation current of the N-type MOS-FET transistor 163 will be greater than the current II68 if the voltage V2 is greater than the voltage Vt , and smaller than the current I168 if the voltage V2 is smaller than the voltage Vj. In the case where the voltage V2 is greater than the voltage V ,, the voltage V168, on the output 168, will be approximately at the "low" level, as shown by point "X" in FIG. 21b. On the contrary, when the voltage V! is greater than the voltage V2 (or that the voltage V2 is smaller than the voltage Vj), the output voltage Vi68 will be at the "high" level, as represented by the point "Y" in FIG. 21b.
This explains the functions indicated by table 1 previously presented.
Fig. 22 shows an example of how the control circuit 93 shown in FIG. 17.
The output signal T4 of the detection circuit 95 is applied to the input for placing in the working position S of a flip-flop 140 of the SR type. The signal Pt, coming from the pulse-forming circuit by combination 92, is applied, via an inverter 57, to the reset input R of a flip-flop 158 of SR type, and it is also applied directly to the reset input R of the flip-flop 140, to the clock pulse input C of a binary counter 143, and to an input of a gate AND 156. An AND gate 141 receives on an input the output signal P2 of the pulse-forming circuit by combination 92, and on its other input the signal coming from the output Q of the flip-flop 140 of RS type. An AND gate 142 receives on an input the signal P3 coming from the pulse-forming circuit by combination 92, and on its other input the signal coming from the output Q of the flip-flop 140. The output signal of the AND gate 142 is applied to the stepper motor drive circuit as a T2 pulse. An AND gate 159 receives on one input the output signal P5 of the pulse-forming circuit by combination 92 and on its other input also the signal coming from the output Q of the flip-flop 140, the output signal of this gate 149 being applied to the control circuit of the stepping motor 94 (fig. 19) as signal T3.
In this embodiment, the binary counter 143 consists of four stages of flip-flops, the output signal of each stage being applied to an AND gate 144. The output thereof is connected to the input of a OR gate, the other input of which receives the signal leaving the AND gate 142. An AND gate 146 receives on one input the signal leaving the output Q of the flip-flop 140, and on its other input the output signal of a NAND gate 147. A bidirectional counter 148 receives on its input U / D for selecting the direction of counting the signal leaving the AND gate 146, while it receives on its counting input C the signal leaving the OR gate 145. In this embodiment, the bidirectional counter 148 comprises three stages of flip-flops, the outputs Qi, Q2 and Q3 of which are respectively connected to the three inputs of the NAND gate 147, as well as to an input of one of three doors EX / OR 150,151,152, respectively. The output signals Pj and P4 of the combination pulse-forming circuit 92, as well as the signal of the output Q of the flip-flop 158, are applied to an AND gate 156 whose output controls, by its counting input C, a binary counter 159, the reset input R of which is connected to the output Q of the RS-type flip-flop 158. In this embodiment, the binary counter 149 consists of three stages of flip-flops whose respective outputs Q, Q2 and Q3 are applied on the one hand to the three inputs of an OR gate 154 and on the other hand to the second input of each of the three above-mentioned EX / OR gates 150, 151 and 152. The outputs of these three EX / OR gates 150, 151, 152 are connected to the three inputs of a NOR gate 153, the output of which is applied to the activation input in working position S of flip-flop 158 of type SR. The output of the AND gate 141, the output of the AND gate 142, the output of the OR gate 154, and the input connection bringing the signal P0 from the pulse-forming circuit by combination 92, are applied to the four inputs of an OR gate 155, the output of which supplies the control pulse T j to the drive circuit of the stepping motor 96 (fig. 19).
The operation of the control circuit according to this embodiment will now be explained:
Since the flip-flop of type SR 140 is put in its working position by the application of the detection signal T4, when the rotor of the stepping motor has normally made its advance by two steps, and since then the output Q of this flip-flop 140 is at the "low" level, all the outputs of the AND gates 141, 142, 146 and 159 are at the "low" level. As a result, the output signal T3 of the AND gate 159 is at the low level when a rotation is detected, and therefore the detection circuit is in the inhibition condition. The bidirectional counter 148 operates in the advance direction when its U / D input is at the "high" level and in the reverse direction when its U / D input is at the "low" level. Since the AND gate 146 then delivers a low level at its output, this counter 148 operates as a countdown counter (reverse operation) when the rotor has operated normally.
At this time, the output signal Pj from the pulse-forming circuit by combination is applied to the counting input C of the binary counter 143 every second and, since this binary counter is four-stage, in the form of execution considered, an output pulse of “high” level is delivered by gate 144 every 16 seconds. This pulse is applied to the counting input C of the bidirectional counter 148, via the OR gate 145, so that the counting state of the bidirectional counter 148 decreases by one unit every 16 seconds.
On the other hand, the output signal P4 of the combination pulse-forming circuit 92 has a frequency of 2048 Hz, so that its period is approximately 0.5 ms. This signal is applied to the counting input C of the binary counter 149, via the AND gate 156, but only insofar as the output signal Px of the pulse-forming circuit by combination 92 is
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at the "high" level. In this embodiment, the binary counter 159 comprises three stages of flip-flops. The EX / OR gates 150, 151, 152 permanently check the coincidence between the outputs of the binary counter 149 and those of the bidirectional binary counter 148. When all the outputs coincide, the three EX / OR gates 150, 151 and 152 each deliver a level " low ”at their exit, which means that the exit from door NOR 153 delivers a“ high ”level. As a result, the SR 158 type flip-flop is put into the working position and its output Q goes to the “high” level, which causes the binary counter 149 to be reset to zero. It follows from this that the output of the OR gate 154 is at the "high" logic level during a time interval equal to the product of the counting content of the bidirectional counter 148 by the time quanta of 0.5 ms delivered on the input P4. This time interval decreases by a quanta of 0.5 ms every 16 seconds, each time the counting content of counter 148 decreases by one.
Under these conditions, there comes a time when the output T4 of the detection circuit 95 does not produce a “high” level signal within the time allocated for detection, which means that the rotor could not have been driven by the application of the first drive pulse. At this time, the output Q of the flip-flop 140 remains at the “high” level. Under these conditions, the pulse P2 coming from the circuit for forming the pulses by combination 92 can pass through the AND gate 141 and operate the output OR gate 155 which has just transmitted the control pulse during the time interval. where the OR gate 154 delivered a "high" level at its output. The output Tj on the command of the pulse P2 therefore delivers a second pulse, the duration of which is determined by the pulse P2, this second pulse constituting the correction drive pulse which will certainly allow the motor to perform the advance by one step which it will not have taken under the control of the normal drive pulse. The output signal P3 of the pulse-forming circuit by combination 92 can also in this case be transmitted by the AND gate 142 and it appears on the output T2 whose signal is applied to the driving circuit 94, at the same time as it appears on the output Tt via the OR gate 155. Under the effect of the pulse on the output T2, the circuit 94 controls the direction of the current in the motor winding so that this current flows, during the pulse P3, in the opposite direction to that in which it had previously circulated during the correction pulse delivered in correspondence with the pulse P2. The combined effect of this current pulse in the opposite direction during the P3 pulse is to eliminate the residual magnetism in the stepping motor, which allows the elimination of the increased saturation time of the saturable magnetic portions, at the following a correction pulse.
On the other hand, since the output TJ of the flip-flop 140 is at the "high" level, the output of the AND gate 146 delivers a "high" level on the U / D input of the bidirectional counter 148, which is of this way prepared to count in the direction of an advance. The pulse P3 of the circuit for forming the combination pulses 92 will be applied to the counting input C of this counter 148, via the AND gate 142 and the OR gate 145. This counter will therefore increase immediately by one step its counting content, so that the next normal training pulse will have its duration increased by 0.5 ms.
If the next step of advance of the stepper motor cannot be made again by the normal drive pulse (for example because the mechanism has started to exert its action on the date ring) the flip -flop 140 will also remain in the idle state, for lack of pulses
T4, at the next pulse, and in the same way the counter 148 will increase by a quanta of 0.5 ms the duration of the normal training pulse. In this way, it could happen that all the outputs Q15 Q2 and Q3 of the flip-flops of the bidirectional counter 148 reach the "high" state, after which the content of the counter would return completely to zero. To prevent this, the NAND gate 147 detects the fact that these three outputs of the counter 148 are at the "high" level and it delivers at that time, at its output a "low" level which, applied to the second input of the AND gate 146, switches its output to the “low” level, which results in the counter being reset again in reverse operating condition (counting down).
If after 0.5 ms the duration of the normal drive pulses has been increased, the stepper motor resumes operation directly under the effect of the normal drive pulses, the flip-flop 140 switches again under the control of a pulse T4, which means that the gate 146 again delivers at its output a "low" level which puts the counter 148 back into operating condition. Under these conditions, after a certain number of normal training pulses of just sufficient duration, a new step back from the counter 148 reintroduces a normal training pulse of insufficient duration, immediately followed, thanks to the operating mode which has just be explained, a correction pulse and a 0.5 ms increase in the normal pulse duration. This process of periodically testing a reduction in the duration of the normal drive pulse is however limited by the presence of the pulse P0 coming from the pulse-forming circuit by combination, the role of this pulse P „, applied to OR gate 155 at the same time as the normal drive pulse, is to determine a minimum pulse duration for the normal drive pulses. The reason why this has been planned is that the operation in “repetitive test” regime of reduction of the normal training pulse duration causes a certain loss of energy, since (typically once in 16) there has been in addition to the normal training pulse a correction pulse of greater duration, which implies a certain loss of energy since the duration of pulse just necessary would certainly be less. When in a low load operating regime for which relatively short normal training pulses are sufficient, it is therefore preferable to prevent further shortening of the normal training pulse duration, and c is what the input pulse P0 does. In this embodiment, the minimum normal drive pulse duration, fixed by the duration of the P0 pulse, is set at approximately 1.9 ms.
The counting content of the bidirectional counter 148 is not reset even when the frequency divider circuit 91 is reset, and the determination of the duration of the normal drive pulses starts again from the value it had before when , once the reset or time reset operations have been carried out, the conditions for resetting the frequency divider circuit to zero are deleted. The duration of the correction pulses, corresponding to the duration of the T2 pulse, is established so as to ensure maximum torque for the stepping motor. In the present embodiment, this duration is set at 7.8 ms. As the bidirectional counter 148 acts as a counter counting forward when the pulse P3 of the circuit 92 is applied, the content of the counter increases by one unit. Thus, if the pulse duration of a training pulse developed after one second is 1.9 ms, the duration of the normal training pulse developed
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after 2 sec will be 0.5 ms longer, i.e. will be 2.4 ms. Furthermore, if the motor cannot be driven in rotation by the application of a pulse having this duration, it will immediately be driven by a correction drive pulse having a duration of 7.8 ms.
A pulse duration of 7.8 ms is relatively long and safely drives the stepping motor even when the load on the gear train becomes greater, for example by the fact that the date ring must be driven or by the fact that the watch is in a magnetic field. This duration of 7.8 ms also ensures safe operation of the stepping motor if the advancement difficulties thereof arise from the fact that the internal resistance of the battery supplying the watch is increased by the action of a low temperature, or because of the battery voltage becomes lower, approaching the end of its life.
If an increased load is suddenly encountered, and if the 0.5 ms increase in the normal pulse duration is still insufficient, there will again be a correction drive pulse and the next second the pulse will have a increased duration by 2.9 ms. If the motor still cannot be rotated by the normal drive pulse of this duration, the same operation is repeated and the duration of the normal drive pulse increases more and more, until it reaches the minimum sufficient. Furthermore, when the counting state of the binary counter 143 becomes equal to 16, the AND gate 144 delivers a "high" level and the bidirectional counter 148 goes down by one unit. Thus, if the normal training operation is carried out by the use of a pulse having a duration of 3.4 ms, the next pulse will in this case only have a duration of 2.9 ms. If, from this moment, the load has become smaller and if this pulse of 2.9 ms of duration is sufficient to drive the rotor, the latter will continue to be driven by the application of such a pulse of duration 2.9 ms, until for some reason this normal 2.9 ms drive pulse duration is no longer sufficient to operate the stepper motor. At this time, a new condition of non-rotation will be detected, the rotor will then be driven by the application of a correction drive pulse, and the state of the bidirectional counter 148 will go up by one, restoring the initial normal drive pulse length of 3.4 ms.
In general, in a watch fitted with a calendar mechanism, the load supported by the stepping motor increases, due to the need to drive the date ring, during a period which lasts approximately 6 hours per day. In this case, the motor can also be driven by normal drive pulses having a duration of 3.9 ms, or 4.4 ms, during the entire period when the calendar mechanism is to be moved, while, in normal operation, the pulse will continue at 3.4 ms. Every sixteen seconds, a pulse of 0.5 ms of month will be tested, which generally ensures the application of driving pulses of the stepping motor which always consumes the minimum necessary energy, counts given the variable load conditions of the stepper motor.
In the embodiment described, since the binary counter 143 comprises four stages of flip-flops, drive pulses and correction pulses will be produced during the same second approximately every 16 seconds. As this phenomenon, as we have seen, can be slightly less economical with regard to energy consumption, it is possible to slow down the rate at which it occurs by increasing the number of stages of the binary counter 143 However, if the number of stages of this counter is increased excessively, there is also a long period until the duration of normal drive pulses returns to its original value when the load is become smaller, after this time has been extended to allow correct operation with a higher load. Thus, a large increase in the number of stages of the counter 143 would still hardly be indicated.
We will now indicate some experimental results obtained with an electronic watch with analog display conforming to the design of the present invention:
These tests related to a men's wristwatch, fitted with a calendar mechanism indicating the dates and the days of the week, comprising a stepping motor whose rotor had a diameter of 1.25 mm, a thickness of 0.5 mm, the air gap between the rotor and the stator having been 0.325 mm, the resistance of the winding of the stepping motor having been 3 KOhms, with a number of turns equal to 10 000.
Table II shows the current values when the stepping motor was driven by different pulses, the values of the mechanical torque measured on the minutes mobile and the values in percent of the number of pulses of each kind which occurred actually produced, this parameter having been measured by the very operation of the stepper motor watch operated for one day. The pulses Pi and P2 correspond first to the normal training pulses, of different durations, and the second to the correction training pulses.
When 64 Pi pulses had been continuously applied to the stepping motor, the pulse duration was reduced by a quanta, and the values given in Table II below were obtained:
Table II
current torque
% of pulses
mechanical pulses
of this type
Pi 2.4 msec
0.563 | 0.A
0.38 gcm
87.0%
2.9 msec
0.647 nA
0.82 gcm
10.0%
3.4 msec
0.708 (iA
1.26 gcm
2.8%
3.9 msec
0.759 \ iA
1.44 gcm
0.2%
4.4 msec
0.816 nA
1.80 gcm
0%
P2 6.8 msec
1.518 (iA
2.76 gcm
0.2%
In fact, the average current consumed by the watch during a day is obtained by summing the products of the current values of each type of pulse by the proportion in which this type of pulse occurred during a day, and by dividing the total thus obtained by hundred (if all the proportions are considered in percent). By proceeding in this way with the values given in table II above, an average current of 0.58 | xA is obtained.
The stepping motor was set up to be controlled by pulses of a duration of 6.8 ms and it can therefore be seen that the current consumption could have been reduced from approximately 1.518 fiA to 0.58 | iA, which represents a current decrease of approximately 62%. At the same time, it is noted that the wristwatch with stepping motor which was the subject of the aforementioned tests was an electronic timepiece of a relatively large format, providing each second a step-by-step advance of the seconds hand and comprising mechanisms for indicating the date and indicating the day of the week.
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Fig. 23 shows another embodiment of the drive and detection circuit, a first embodiment of which was shown in FIG. 19. One end of the stepping motor winding is connected to an N-type switching MOS-FET transistor 115 through a detection resistor 17a, while the other end of the winding of the stepper motor is connected via a switching N-type MOS-FET transistor 116, via a detection resistor 117b. The ends of the winding of the stepping motor 10 are thus directly connected to these comparators 110a and 110b, and the detection signal generated in the winding of the stepping motor is thus directly processed, which ensures high detection precision, without distortion of the detection signal. u
The output signals of the comparators 110a and 110b are digital signals and are applied to an OR gate 126,
whose output feeds the output connection 112. The latter is applied to the connection point T4 in FIG. 22. It is thus possible to obtain an extremely precise detection of the rotation or of the non-rotation of the rotor of the stepping motor.
It is also noted that the reference voltage which is applied to one of the inputs of comparator 110 (fig. 19) or to the inputs of comparators 110a and 110b (fig. 23) is modified in accordance with a change in supply voltage in the embodiments according to FIGS. 19 and 23. More precisely, if the voltage which is applied to resistors 108 and 109 intended to establish the reference voltage is constant, without relation to the supply voltage, it is possible to detect a constant rotation or non-rotation of the rotor under constant detection conditions, whereby the operation of the detection circuit is greatly stabilized.
Fig. 24 shows an embodiment of a circuit for generating a constant voltage. The source of a P-type MOS-FET transistor 170 is connected to the positive pole of the power source, the control electrode and the drain of this transistor are connected together and are also connected to the control electrode and to the drain of an N type MOS-FET transistor 171, the source of which is connected to ground (negative supply voltage) via a resistor 172. The threshold voltage of the MOS-FET type transistor P is V VXP, the factor K of this transistor being Kp. The threshold voltage of the N-type MOS-FET transistor is the K factor of this transistor being KN. The value of resistance 172 is R. We can thus pose the following formula:
V0 = vTN + vTp + i / §g + i / ^ §g
Thus, if R is greater than VDD / KP and VDD / KN, V0 is not modified even if the supply voltage VDD is changed.
In the present embodiment, the resistance 172 is 500 KOhms, and V0 is approximately 1.2 Y.
As just described, in the electronic watch and in particular the electronic wristwatch with analog display by stepping motor according to the present invention, since all the constituent elements can be formed on an integrated MOS circuit, and since a motor conventional type stepping is driven by pulses always having the minimum duration necessary to drive the stepping motor, and since also in this watch there is no factor capable of causing an increase in cost, it is possible to obtain, according to the invention, a wristwatch extremely advantageous in that, without being of a cost price higher than that of another similar watch, it has an extremely reduced energy consumption. The watch according to the invention therefore has remarkable characteristics as a wristwatch and meets the requirements for finesse, low cost and very miniaturized format.
Although, in the description just given, an embodiment has been described and explained in which the stepping motor comprises a stator formed in one piece, the advantageous effects which the application of the design provides according to the present invention can be obtained both in the case of a stepping motor comprising a two-piece stator as in the case of a stepping motor comprising a one-piece stator.
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16 sheets of drawings

Claims (8)

1, in which said means for detecting a voltage induced in the winding comprises a high impedance in a circuit to which said winding is then connected, high impedance on which a voltage occurs whose value is dependent on the fact that the motor is in the condition rotation or in the non-rotation condition.
1. Electronic timepiece, in particular electronic wristwatch, with analog display using a stepping motor, comprising:
- means for producing periodic normal training pulses the duration of which may vary in steps within a predetermined interval,
a circuit for detecting the condition of rotation or non-rotation of the motor, this detection circuit comprising means for detecting a voltage induced in the motor drive bobi78nage by the movement of the rotor of this motor, these means acting during a short pulse detection period after the cessation of the normal training pulse,
- And a control circuit arranged to deliver, when the detected induced voltage is considered by the detection circuit as corresponding to a non-rotation of the motor, a correction drive pulse whose duration is sufficient to drive the motor in rotation , and to increase the duration of the next normal training pulse by one step, compared to the previous normal training pulse, within the limits of said interval.
2, wherein said means for detecting an induced voltage in the winding comprises a high impedance and means for inserting this intermittently in a closed loop including said winding in series.
2, comprising a comparator arranged to compare the said voltages produced with a predetermined reference voltage, and to consequently supply a control signal for controlling said control circuit.
2. Electronic timepiece according to claim
3, in which said reference voltage is constituted by the threshold voltage of a circuit with a C-MOS element.
3. Electronic timepiece according to claim
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4. Electronic timepiece according to claim
5. Electronic timepiece according to claim
6. Electronic timepiece according to one of claims 2 to 5, characterized in that the value of the high impedance is between 4 KOhms and 200 KOhms.
7. Electronic timepiece according to claim 1, wherein said means for detecting a voltage induced in the winding comprises means for switching this winding alternately in a closed loop at high impedance and in a closed at low impedance.
8. Electronic timepiece according to any one of claims 1 to 7, in which means are provided to apply to the motor winding a short demagnetization pulse of the magnetic circuit of the motor after a correction drive pulse has been applied to this motor and before the next normal drive pulse is applied.
CH1074378A 1977-12-02 1978-10-17 CH639815A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP14465177A JPS6115387B2 (en) 1977-12-02 1977-12-02

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CH639815B CH639815B (en)
CH639815A true CH639815A (en) 1983-12-15

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Family Applications (1)

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CH1074378A CH639815A (en) 1977-12-02 1978-10-17

Country Status (8)

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US (2) US4326278A (en)
JP (1) JPS6115387B2 (en)
CH (1) CH639815A (en)
DE (1) DE2841946C2 (en)
FR (1) FR2410843B1 (en)
GB (2) GB2094517B (en)
HK (2) HK19084A (en)
SG (1) SG64883G (en)

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Also Published As

Publication number Publication date
US4445784A (en) 1984-05-01
HK18684A (en) 1984-03-09
JPS6115387B2 (en) 1986-04-23
SG64883G (en) 1985-03-29
CH639815B (en)
DE2841946C2 (en) 1992-02-20
US4326278A (en) 1982-04-20
DE2841946A1 (en) 1979-06-07
GB2094517A (en) 1982-09-15
FR2410843A1 (en) 1979-06-29
GB2094517B (en) 1983-01-19
FR2410843B1 (en) 1984-08-10
JPS5477169A (en) 1979-06-20
HK19084A (en) 1984-03-09
GB2009464B (en) 1983-02-02
GB2009464A (en) 1979-06-13

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