EP0057663A2 - Control device for stepping motor - Google Patents

Abstract

Control device for a stepping motor provided with a coil and a rotor subjected to a rotational movement when the coil is traversed by a current, comprising means for supplying a plurality of time base signals, means for producing, in response to time signals, motor control pulses, means responding to the control pulses for supplying the motor by maintaining the current in the coil at a substantially constant and determined value. This device also includes means for analyzing the voltage signal present on the coil or a signal representative of the latter and providing at least information on the voltage induced in the coil by the movement of the rotor. By providing means for supplying the motor comprising switching means for connecting the coil to a supply voltage source and for short-circuiting the coil and means for periodically comparing, during each control pulse, the current in the coil to a reference value and provide a control signal to control the switching means, in order to short-circuit the coil when, during a comparison, the current exceeds the reference value and to supply voltage to the coil in otherwise, until the next comparison, in order to maintain the average value of the current at the reference value for the duration of the control pulses, it is possible to obtain a high efficiency supply system and, at the coil terminals, logical information on the induced voltage whose analysis and operation can be easily carried out by logic circuits.

Description

The present invention relates to control devices for stepping motors.

In stepper motors, the analysis of the voltage induced in the driving coil by the displacement of the rotor makes it possible to know the behavior of the motor when it takes a step. This analysis can be useful both for the realization of motor control and servo-control circuits, in particular those which make it possible to adapt the duration of the driving pulses applied to it to its load, as well as at the level of devices for measuring parameters of this motor such as useful torque, current consumed, etc., or to check its correct operation.

However, most of the stepping motors, in particular those used in watchmaking, are powered by driving pulses of fixed voltage. During the duration of these driving pulses, the measurement of the induced voltage can then only be done indirectly, by analyzing the current in the coil. This operation is delicate in particular because of the influence of the coil's own self, a large value self which opposes the current variations resulting from the existence of said induced voltage, which disturbs the measurement.

Another disadvantage of the known control devices is that if the voltage of the power source to which the coil is connected during the driving pulses varies, the power supplied to the motor also varies. The operation of the engine is therefore subject to variations that may arise from the electromotive force and the internal resistance of the energy source, as is the case in watchmaking where the engine can be supplied with batteries whose voltage varies in time and from one type to another.

The object of the invention is in particular to provide a control device for a stepping motor capable of supplying, during the duration of the driving pulses which are applied to it, precise information on the voltage induced in the coil by the movement of the rotor.

The invention also proposes to provide a control device making the operation of the engine independent. over a wide range of supply voltage.

According to the invention, the control device of a stepping motor provided with a coil and a rotor subjected to a rotational movement when the coil is traversed by a current, comprises means for providing a plurality of time base signals, means for producing, in response to time base signals, motor control pulses, means responding to the control pulses for supplying the motor by maintaining the current in the coil at a value substantially constant and determined during the duration of the control pulses, means for taking a signal representative of the voltage signal present on the coil and analysis means for supplying, from the signal representative of the voltage signal, at least information on the voltage induced in the coil by the movement of the rotor.

The analysis means can be designed to also provide information on the voltage value across the resistance of the coil.

Furthermore, it is possible to provide the device for controlling additional circuits to determine, from the indications provided by the analysis means, other parameters relating to the operating conditions of the engine such as the energy consumed during 'a step.

The various results can then be used to control the motor control so as to reduce the energy consumption, for example by interrupting the driving pulse when the rotor has taken its step or by controlling the duration of the driving pulse in function variations in engine load. It is also possible, for example, to determine whether a step has not been taken and to correct this error by sending an additional high-energy driving pulse to force the passage of the rotor.

In addition to the fact that it makes it possible to achieve the main objectives sought, that is to say the possibility of directly obtaining information on the voltage induced by the movement of the rotor, without having to go through the analysis of the current. , and the independence of the operation of the motor with respect to the parameters of the power source, which is very advantageous in applications such as watchmaking, the constant current power supply also has the advantage of to reduce the number of turns of the coil by increasing the diameter of the wire accordingly, resulting in an interesting gain on the price of the coil.

However, to be able to use such a feeding method, at the level of portable, autonomous and small-sized devices such as watches, it is necessary to produce a high-efficiency feeding device.

It is therefore not possible, for example, to supply the motor with high voltage pulses through a large current limiting resistor.

The invention also makes it possible to provide a solution to this problem by producing a stepping motor control device in which the means for supplying the motor which comprise switching means for connecting the coil to a supply voltage source and for short-circuiting said coil also comprise means for periodically comparing, during each motor control pulse, the current in the coil with a reference value and supplying a control signal for controlling the switching means, in order to short-circuit the coil when, during a comparison, the current exceeds the reference value and supplying the coil with voltage if the current is less than this value, this until the next comparison, so as to maintain the average value of the current at the reference value for the duration of the control pulses.

The reference value can be chosen as a function of the threshold voltage of an MOS transistor, independent of the supply voltage.

It is also possible to program this reference value using current sources which can be switched and combined with each other.

The voltage across the coil, during the control pulses, is thus composed of a succession of supply periods interspersed with short-circuit periods which form logic information representative of the induced voltage.

The analysis of this information or of a signal which is its image, such as the control signal used to control the switching means, can therefore be carried out by means of entirely logic circuits, which constitutes an advantage. which is added to that of the high efficiency that can be obtained from such a switching power supply system. ge.

Furthermore, the signal present at the terminals of the coil can be picked up either by a galvanic link on a motor terminal, or without contact, for example inductively by a pick-up coil and analyzed by circuits external to the control device. This makes it possible to determine the parameters relating to the operation of the engine without any intervention inside the control device, which is particularly advantageous for checks in progress or at the end of manufacture and during repairs.

• - la figure 1 montre le schéma électrique équivalent d'un moteur pas à pas de type connu,
• - la figure 2 montre les courbes des tensions de la figure 1, dans le cas d'une alimentation à tension constante,
• - la figure 3 montre les courbes des tensions de la figure 1 dans le cas d'une alimentation à courant constant,
• - la figure 4 montre le schéma d'un circuit de commande selon l'invention,
• - la figure 5 montre le courant consommé par le moteur, respectivement dans le cas d'une alimentation à tension constante (5a) et à courant constant (5b).
• - la figure 6 montre le schéma-bloc d'un circuit d'analyse du signal de contrôle produit par le circuit de la figure 4,
• - la figure 7 montre le schéma-bloc d'un circuit de calcul de l'énergie consommée par le moteur,
• - la figure 8 montre le schéma d'un circuit externe de reconstitution du signal de contrôle produit par le circuit de la figure 4, et
• - la figure 9 montre le schéma d'un circuit permettant de programmer le courant de référence déterminant le niveau de déclenchement du discriminateur de niveau de la figure 4.

The invention will now be described in more detail, by way of example and with reference to the accompanying drawings in which:

• FIG. 1 shows the equivalent electrical diagram of a stepping motor of known type,
• FIG. 2 shows the voltage curves of FIG. 1, in the case of a constant voltage supply,
• FIG. 3 shows the curves of the voltages in FIG. 1 in the case of a constant current supply,
• FIG. 4 shows the diagram of a control circuit according to the invention,
• - Figure 5 shows the current consumed by the motor, respectively in the case of a constant voltage supply (5a) and constant current (5b).
• FIG. 6 shows the block diagram of a circuit for analyzing the control signal produced by the circuit of FIG. 4,
• FIG. 7 shows the block diagram of a circuit for calculating the energy consumed by the motor,
• FIG. 8 shows the diagram of an external circuit for reconstituting the control signal produced by the circuit of FIG. 4, and
• FIG. 9 shows the diagram of a circuit making it possible to program the reference current determining the tripping level of the level discriminator of FIG. 4.

FIG. 1 represents the equivalent electrical diagram of a bipolar single-phase stepper motor of the Lavet type commonly used in watchmaking, FIG. 2 shows the voltage curves of FIG. 1 for driving pulses at constant voltage and FIG. 3 shows the curves of the voltages of figure 1 for driving pulses with constant current. This type of motor essentially includes a choke its own, a coil resistance and a voltage generator at the terminals of which appear the voltages of self U _L , of resistance U _R and the voltage Ui induced in the coil by the displacement of the rotor. The sum of these three voltages is equal to the voltage Ub across the coil.

When the motor is supplied at constant voltage, the current is variable. FIG. 2 represents the distribution of the components U _L , Ui and U _R during the driving pulse.

The current being variable, these three components are variable, and the value of Ui can only be known by determining the variables U _R and U _L. On the other hand, when the motor is supplied with constant current (fig. 3) the component U _L is eliminated as soon as the current reaches the set value (constant) and the component U _R becomes constant and equal to RIo, Io being the current in the coil. The voltage across the coil is equal to U _R + Ui = Ui + constant. The value of the constant U _R can be measured at the start of the driving pulse, as soon as the current in the coil has reached the setpoint Io. In fact, at this instant, the speed of the rotor is still low and the value of the induced voltage Ui is negligible. We can therefore admit that U _R : Ub.

FIG. 4 shows by way of example the diagram of a control circuit of the device according to the invention, circuit making it possible to maintain the current in the coil at a value fixed during the duration of the control pulses of the advance of the motor. . A quartz oscillator 10 delivers a 32 kHz signal to the clock inputs a of a frequency divider 11 and of a type D flip-flop, 12, operating as a monostable. To this end, the output Q (b) of this flip-flop is connected by a resistor 13 to its reset input (c) and to a capacitor 14 connected against ground. Thus, each time the flip-flop 12 goes to the logic state "1", the capacitor 14 charges through the resistor 13 and the reset occurs after a certain delay which is chosen to be of very short value (2 ps). The flip-flop 12 therefore delivers fine pulses with a duration of 2 μs at a repetition frequency of 32 kHz when its input D (e) is at "1".

The divider 11 delivers signals of frequency 8 kHz on its output b, 4 kHz on its output c, 2 kHz on its output d; 1 kHz on its e output, 64 Hz on its f output, 32 Hz on its g output and 0.5 Hz on its h output. The latter is connected to the clock input a of flip-flop of type D, 15, and through an inverter 17 at the clock input a of another flip-flop of type D, 16. The inputs D (b) of flip-flops 15 and 16 are maintained at state "1" while their reset inputs (c) are connected to the output of an OR gate 18 whose input a is connected to the output g (32 Hz) of the divider 11. The flip-flops 15 and 16 take turns, one on the positive side of the 0.5 Hz signal on the output h of the divider 11, the other on the negative side of this same signal, pulses to control the engine advance. It is the 32 Hz output (g) of the divider which, through gate 18, carries out the reset of flip-flops 15 and 16 and thus determines the duration of the control pulses, ie 16 ms.

The outputs d of the flip-flops 15 and 16 are connected to the inputs b and a of an OR gate 20, to the inputs a of two NAND gates 21 and 22, as well as to the control inputs of two analog switches 23 and 24. The output of gate 21 is connected to the gate of a P-MOS transistor of power 25 and to the input a of an AND gate 26, the output of which is connected to the gate of an N-MOS transistor. of power 27. The output of gate 22 is connected to the gate of a P-MOS transistor of power 28 and to the input a of an AND gate 29 the output of which is connected to the gate of a transistor N - Power MOS 30.

The sources of the P-type transistors 25 and 28 are connected to the positive pole of the electrical supply source and the sources of the N-type transistors 27 and 30 to the negative pole of this source. The drains of transistors 27 and 25 are connected to terminal a of the motor coil 31, and the drains of transistors 28 and 30 to terminal b of this coil. These power transistors 25, 27, 28 and 30 form switching means making it possible either to connect the coil to the terminals of the electrical supply source, or to short-circuit this coil. Let us assume that the inputs b of doors 21,22,26 and 29 are at "1". In the absence of pulses on the outputs of the flip-flops 15 and 16, the outputs of the gates 21, 22, 26 and 29 are at "1". Transistors 25 and 28 are cut, while transistors 27 and 30 are conductive: The coil is short-circuited.

When the flip-flop 15 delivers a control pulse, the outputs of the gates 21 and 26 change to "0". The transistor 27 is cut off and the transistor 25 becomes conductive, connecting the terminal a of the coil 31 to the positive pole of the power source. The current flows in the meaning a - b.

When the flip-flop 16 delivers a control pulse, the outputs of the gates 22 and 29 change to "0". The transistor 30 is blocked and the transistor 28 becomes conductive, connecting the terminal b of the coil 31 to the positive pole of the power supply. Current flows through the coil in direction b - a. The motor is thus supplied with pulses of alternating polarity at the rate of one pulse per second, as in most known watch circuits.

When a pulse arrives at the output of the flip-flop 15, the switch 23 becomes conductive, so that a resistor R1 and the gate of an N-MOS transistor 32 are connected in parallel with the power transistor 30. On the other hand, the input D (e) of the type D flip-flop, 12, goes to "1", and the latter delivers on its output Q (d) very fine negative pulses of duration 2 μs at the frequency of 32 kHz which are transmitted by gate 29 on the gate of transistor 30, which periodically blocks this transistor, for very short moments. Since the current in the coil 31 can no longer flow in this transistor 30, it then passes entirely through the resistor R1, causing an increase in the voltage on the gate of the N-MOS transistor 32. If the current in the coil is of sufficient value high, this voltage rise exceeds the conduction threshold of transistor 32 (V _T ) and the latter becomes conductive. A negative pulse appears on the drain of this transistor which is connected to a resistor 33 of great value, connected to the positive pole of the power supply and to the input of an inverting amplifier 34, at the output of which therefore positive pulses appear . This combination acts as a level discriminator of the current in the coil. Indeed, when the current in the coil is greater than a fixed value (Io = V _{T /} Rl), a signal appears at the output of the amplifier 34. On the other hand, if the current in the coil is more small than the fixed value, the conduction threshold of transistor 32 is not reached and the output of amplifier 34 remains at "0". It can be noted that this conduction threshold, ie the threshold voltage of transistor 32, is independent of the supply voltage. As a result, the level of current discrimination, V _{T /} Rl, is itself independent of the motor supply voltage.

The output of amplifier 34 is connected to input D (a) of a type D flip-flop, 35, whose clock input (b) is connected to the Q output (d) of the flip-flop 12 delivering negative test pulses. At the end of the test pulse, the flip-flop 35 records the state of its input D and thus stores the state at the output of the amplifier 34, depending on the level of current in the coil.

If this current is greater than the fixed value, the output of the amplifier 34 is at "1" and the output Q (c) of the flip-flop 35 goes to "0". Conversely, if the current in the coil is smaller than the fixed value, the output of the amplifier 34 remains at "0" and the output Q (c) of the flip-flop 35 changes to "1". The output Q (c) is connected to the input b of the NAND gate 21, the output of which remains at "0" if this output Q remains at "1", but which however goes to "1" if the output goes to "0", which blocks transistor 25 and turns transistor 27 on. Thus, the power supply to the coil is interrupted and the short-circuit restored to its terminals, each time the discriminator delivers a signal corresponding to the condition that the current in the coil is greater than the fixed value, which produces a state "0" on the output c of the flip-flop 35. Conversely each time the output of the discriminator remains at "0", which corresponds on condition that the current in the coil is less than the fixed value, the output c of the flip-flop 35 comes to "1" and the supply of the driving coil 31 by the transistor 25 is restored, the transistor 27 being cut off .

When the control pulse arrives at the output of the flip-flop 16, the process is the same. Simply, it is the switch 24 which is conductive, and the resistor R1 is connected in parallel to the transistor 27 which is interrupted periodically for very short moments by the pulses coming through the gate 26 and delivered by the output Q (d ) of the flip-flop 12, and it is the gate 22, the input b of which is connected to the output Q (c) of the flip-flop 35 which makes it possible either to supply the driving coil by the transistor 28, or to short-circuit it with transistor 30, depending on the state of this output c of flip-flop 35, a state which depends on the level of current in the coil. We thus obtain a servo-control of the current in the driving coil during the duration of the control pulses, servo-control which tends to keep this current constant and equal to the fixed value, Io = V _{T /} R1. The coil is supplied in all or nothing by a plurality of short duration pulses followed by as many short circuits. You would think that variations in current in the coil, between the supply and short-circuit phases are important. It should not be forgotten, however, that the stepper motors have a large series self. This inductor acts as a current regulator, and keeps the current in the coil around the set value, even during short-circuit periods. The theory of this type of diet is as follows.

où L est la self-induction de la bobine 31. Lorsque la bobine est alimentée, la tension Ub est égale à la tension d'alimentation V :

Lorsque la bobine est court-circuitée, la tension Ub est égale à 0 :

Par le fait que la bobine est alimentée en courant constant, la somme des variations (3) et (4) doit être nulle :

où t = période de test (- 30 ps) n = nombre de périodes d'alimentation de la bobine n ₌ nombre de périodes de court-circuit de la bobine, avec

à partir de (5), on calcule :

The voltage Ub across the coil is given by

where L is the self-induction of the coil 31. When the coil is supplied, the voltage Ub is equal to the supply voltage V:

When the coil is short-circuited, the voltage Ub is equal to 0:

By the fact that the coil is supplied with constant current, the sum of the variations (3) and (4) must be zero:

where t = test period (- 30 ps) n = number of coil supply periods n ₌ number of coil short-circuit periods, with

from (5), we calculate:

The average voltage Ub, on the coil is given by:

où Io = courant constant dans la bobineThe current consumed, Ic, on the power supply is given by:

where Io = constant current in the coil

The relation (7) is interesting; it shows that the average value of the voltage on the coil, represented by a succession of short duration pulses, interspersed with short circuits, is equal to the sum U _R + Ui.

If the coil supply times are represented by logic states "1" and the short-circuit times by logic states "0", the distribution of the coil supply and short-circuit times is given by a sequence of these logical states, a sequence representative of Ub = U _R + Ui. This sequence of logic states is delivered by the output c of the flip-flop 35 of FIG. 4 and it is also found at the terminals of the driving coil 31. It can also be called "control signal".

An adequate analysis of this sequence of logical states therefore makes it possible, as will be seen below, to know U _R and Ui and to deduce therefrom certain important parameters relating to the operation of the engine.

Although the current Io in the coil is constant, the average current, Ic, delivered by the power supply is variable, since Io only passes through the power supply during the supply times of the coil. The relation (8) shows that Ic is proportional to Ub, that is to say to the sum U _R ⁺ Ui.

FIG. 5 shows a comparison between the form of current Ic delivered by the power supply in the case (5a) where the coil is supplied with constant voltage and in the case (5b) where the coil is supplied with constant current by the device according to the invention.

In the first case, the current decreases when the induced voltage increases and vice versa. The current at the end of the control pulse tends to its maximum value.

In the second case, the current increases and decreases with the induced voltage; the current at the end of the control pulse tends to 0.

Finally, note that if Io is independent of the supply voltage, which is possible using an internal stabilizer, the motor is no longer affected by the variations of the latter since the number of ampere-turns that it receives remains constant.

It is therefore possible to supply the motor with power sources whose voltage varies over time, which is the case for example for lithium batteries, without modifying the working point of the motor.

FIG. 6 represents by way of example the block diagram of a circuit for analyzing the sequence of logic states delivered by the control circuit of FIG. 4, a circuit making it possible to determine the ratios Ui / V and U _{R /} V. This circuit is connected to the control circuit of FIG. 4 by the points P1 (test pulses), P2 (test), P3 (motor control pulses) and P4 (end of motor control pulses).

The point P2 which corresponds to the output of the level discriminator and to the input D (a) of the flip-flop 35, is connected to the input D (a) of a transfer register 40 of 16 stages, at the clock input of a type D flip-flop, 41, and at inputs a of an EXCLUSIVE gate 42 and a NOR gate 43. The point Pl which delivers fine pulses of 2 ps of duration at 32 kHz on the clock input b of the flip-flop 35 is connected to the clock input b of the register 40 and to the clock inputs a of two type D flip-flops, 44 and 45 .

The point P3 which corresponds to the output of door 20 on which positive pulses appear for each motor control pulse, pulses delivered either by the flip-flop 15 or by the flip-flop 16, is connected to the input d 'an inverter 46 whose output is connected to the reset inputs c of register 40, b of the type D flip-flop, 41 and to another type D flip-flop, 47. The register 40 and the flip- Flops 41 and 47 are therefore only operational for the duration (max. 16 ms) of the motor control pulses since they are kept at "0" between these pulses.

The first stage of the register 40 is connected in parallel with the flip-flop 35 and has on its output Q, like this flip-flop 35, the sequence of logical states representing the ratio (U _R + Ui) / V = n ⁺ / n.

This sequence of states is transmitted with a delay period on the gate Q of the second stage of the register 40 with two periods of delay on the output Q of the third stage, etc. and with 15 periods of delay on the output Q (e) of the 16th stage of register 40. This register 40 thus permanently stores the last 16 periods of the sequence of logic states, ie a duration of 0.5 ms. By making the ratio between the number of stages of register 40 whose outputs Q are at "1" and the total number of stages, we obtain the ratio n ⁺ / n, that is = (U _R + Ui) / V (the total number n of stages is of course constant and equal to 16).

It is obviously interesting to be able to isolate U _{R /} V and Ui / V. We know that U _R becomes constant as soon as the current in the coil reaches the setpoint Io. The parameters of the coil are chosen in such a way that this establishment time is short, so that the ratio (U _R + Ui) / V can be measured at the start of the motor control pulse, i.e. at around point A in Figure 5b. In fact, at this instant, the rotor speed is low and the induced voltage is close to 0. The ratio U _{R /} V is therefore approximately equal to the number of stages of register 40 whose Q outputs are at "1" on the first group representative of the memorized states of 16 periods. The start of this first group begins as soon as the current in the coil reaches the setpoint Io, ie as soon as the test input (P2) goes to "1" and the output Q of the first stage of the register to "0". The end of this first group of 16 periods corresponds to the moment when this state "0" on the output Q of the first stage arrives at the last stage of the register, that is to say when the output Q15 (e) of the register 40 passes in turn to "0" for the first time, the output Q15 (d) passing it to "1". The beginning and the end of this first group representative of 16 periods are recorded respectively by the flip-flop 41 which goes to "1" as soon as the entry P2 goes to "1" and the flip-flop 47 whose entry D (b) is connected to the output Q (d) of the flip-flop 41 whose output Q changes to "1" as soon as the output Q15 (d) of register 40 changes to "1". The output Q (c) of the flip-flop 47 is connected to the input b of the NOR gate 43 whose other input (a) is connected to the input D (b) of the flip-flop 44 which is connected as a monostable, its output Q (c) being connected by a resistor 48 to its reset input (d) and to a capacitor 49 connected to ground.

At the start of the driving pulse, the output Q (e) of the flip-flop 47 is at "0". The output of gate 43, ie input b of flip-flop 44 comes to "1" each time input P2 comes to "0". The "test pulses" on P1 simultaneously attack the clock inputs of flip-flop 44 and register 40, so that the output Q (c) of flip-flop 44 changes to "1" each time the first stage of register 40 records a state "1" on its output Q. The output c of the flip-flop 44 returns to "0" as soon as the resistor 48 has charged the capacitor 49 and actuated the reset. This output c of the flip-flop 44 therefore delivers a pulse to the clock input (a) of a counter 50, for each state "1" of the sequence of logic states delivered by the control circuit of FIG. 4.

The reset input R (b) of the counter 50 is connected to the output Q (e) of the flip-flop 41 which changes to "0" at the start of the first group representative of 16 periods, so that the counter 50 is kept at 0 until the start of this first group. At the end of the first group of 16 periods, the flip-flop 47 changes to "1", which blocks at "0" the input D (b) of the flip-flop 44 which therefore ceases to deliver pulses on its exit. Thus, the counter 50, starting from 0, counts and stores the number of states "1" which are in the first group representative of 16 periods. Its state, represented by the binary combination present on its outputs Q0 (c), Q1 (d), Q2 (e) and Q3 (f), is equal to the ratio U _R / ^V.

As soon as the first group of 16 periods corresponding to the value of the UR / V ratio has been recorded in the register 40, that is to say as soon as the output Q 15 of the latter changes to "1", it is possible to calculate Ui / V by analyzing the variations in the n ⁺ / n ratio, that is to say the variations in the number of states "1" on the outputs Q of the 16 stages of the registers 40. Indeed, U _R is then constant and these variations can only be produced by the induced voltage, Ui, which, as we have seen, is practically zero at the start of the pulse. It is easy to know whether the number of states "1" contained in the register increases, decreases or remains stable.

If a "1" is entered in the register and a "0" is output, the number of states "1" increases by one. On the other hand, if a "0" is entered and a "1" is output, the number of states "1" decreases by one. If you enter "1" and exit "1", the number of states "1" remains stable, just as if you enter a "0" and exit a "0" ".

The output Q 15 (d) of the register 40 is connected to the input b of an EXCLUSIVE gate 42 whose output is connected to the input D (b) of the flip-flop 45 connected as a monostable, its output Q (c) being connected to its reset input (d) by a resistor 51, also connected to a capacitor 52, the second terminal of which is connected to ground. The input D of the flip-flop 45 is at "1" each time the input P2 and the output Q 15 of the register are in different states, that is to say each time the number of states " 1 "in register 40 should change. Indeed, when the input P2 is at "0" and the output Q 15 of the register at "1", just before the test pulse (Pl), this means that we will introduce a "1" in the first floor (exit Q), and output a "0" from the last floor (exit Q 15) from the register. The number of states "1" will therefore be increased by one and vice versa, when input P2 is at "1" and output Q 15 from 40 to "0".

In these two cases, the flip-flop 45 goes to "1" at the next test pulse on Pl and delivers a pulse to the clock input a of a reversible counter 53. This counter 53 therefore receives a pulse each once the number of states "1" contained in register 40 is increased or decreased by one. The counting direction of the counter 53 is determined by the state of the input U / D of the counting direction (b) which is connected to the output Q 15 (d) of the register 40. The counter 53 is incremented by one unit when this Q 15 output is at "1", that is to say when the number of states "1" in the register increases by one unit, and conversely it is decremented by one unit when the Q 15 output from the register 40 is at "0", that is to say when the number of states "1" in the register decreases by one. Recall that these are the states of the outputs Q of the stages of the register 40 which are taken into account to form the sequence of logical states representing the ratio (U R + Ui) / V. Indeed, it is necessary, at the start of the motor control pulse, to have only states "1" in the register, which is obtained by actuating the reset and taking into account the Q outputs

In the case where P2 and the output Q 15 of the register 40 are in the same state, the input D (b) of the flip-flop 45 is at "0" and therefore it cannot deliver a clock pulse to the counter 53. The reset input c of this counter 53 is connected to the output Q (d) of the flip-flop 47 which changes to "0" at the end of the first group representative of 16 periods, ie when UR / V has been stored in counter 50. The counter 53 therefore starts from 0 at the end of this first group of 16 periods and its state, represented by the binary combination present on its outputs Q0, Q1, Q2 and Q3 (d, e, f, g), is equal to the ratio Ui / V.

We therefore extracted from the sequence of logical states the values of U _{R /} V and Ui / V represented in coherent binary form. It is obviously interesting to be able to use this data.

For example, it is interesting, by analysis of the induced voltage Ui, to determine when the rotor has taken its step to interrupt for example the motor control pulse (energy saving), or to control the motor at fast rate (self-triggered register). It is also possible to determine whether the motor rotor is blocked (zero induced voltage) or to measure the energy which it is desired to transmit by the motor (control of the integral f UiIodt).

If we analyze the voltage induced (figure 3) by the displacement of the rotor, we see that it increases initially then returns to 0 (point B of figure 5b). At this change to 0, it is practically certain that the rotor has taken its pitch and it is possible, for example, to interrupt the control pulse. This passage through 0 is easy to detect by means of a type D flip-flop, 54, the clock input a of which is connected to the output Q 3 (g) of the counter 53, the reset input to zero (b) at output Q (d) of flip-flop 47 and input D (c) at output Q 15 (e) of register 40.

So, when the counter 53 goes from 0 to 15 (in reverse obviously), the output Q 15 (d) of the register is at "0" and the output Q 15 at "1", the flip-flop 54 goes to " 1 ". The output Q (d) of the flip-flop 54 is connected to the end of pulse P4 input, that is to say the input b of the gate 18 which acts on the resetting of the flip-flops 15 and 16 so as to interrupt the command pulse before the maximum duration of 16 ms.

We mentioned above the possibility of using the integral f Ui.Io.dt to determine the energy transmitted by the motor to the load. The current being constant, this integral is proportional to f Ui.dt.

In the circuit according to the invention, it is possible to integrate either Ui / V which remains dependent on variations in the supply voltage V, or Ui / U _{R =} Ui / IoRb where Io and Rb can be considered as constant. This integral can be determined by calculation circuits or traditional counters, as shown in Figure 7.

The circuit of FIG. 7 comprises a logic comparator 60 which receives on its inputs A the output signals 1 kHz, 2 kHz, 4 kHz and 8 kHz from the divider 11 of FIG. 4 and on its inputs B the output signals Q0, Q1, Q2 and Q3 of the counter 53 in FIG. 6, outputs on which the digital signal represents the value of the Ui / V ratio.

Signal A consists of a sequence of 16 logic states, 0000 to 1111, of 4 bits each, with a period of 1 ms imposed by the signal of 1 kHz. Signal B, which is proportional to the induced voltage Ui in the driving coil during a step, that is to say during a control pulse (max. Duration 16 ms), can be considered as constant for the duration of the 1 ms period of signal A. Under these conditions, and starting from the state 0000 of signal A, comparator 60 delivers pulses of 8 kHz each millisecond at its output, and this as long as the binary value of signal B exceeds the binary value of signal A. In other words, the number of 8 kHz pulses delivered each millisecond at its output by comparator 60 is equal to Ui / V.

The output of comparator 60 is connected to the input a of an AND gate 61, the input b of which is connected to the 16 kHz output of the divider 11 in FIG. 4. The gate 61 therefore lets each millisecond pass through its output a number of periods of the 16 kHz signal equal to the value of Ui. This output is connected to the clock input a of a programmable divider 62, the reset input b of which is connected to point P5 (reset) in FIG. 6, so that this divider 62 does not work. only during the duration (max. 16 ms) of the motor control pulses. The programming inputs of the divider 62 are connected to the doors Q0, Q1, Q2 and Q3 of the counter 50 of FIG. 6, representing the value of U _{R /} V, so that the division rate of the divider 62 is equal to the ratio U _R / ^V.

(9) avec t = nombre de milli- secondes depuis le début de l'impulsion de commande.The number of signals delivered at the output c of the divider 62 is therefore equal to the number of signals on its input divided by the division rate, ie t.

(9) with t = number of milliseconds since the start of the control pulse.

Ui / V = number of signals delivered at the output of gate 61 each millisecond. U _{R /} V = division rate of divisor 62.

It can be seen that the number of signals delivered at the output of the divider 62 is representative of the integral S Ui.dt. To find out this quantity, the output of the divider 62 is connected to the clock input a of a counter 63, the reset input b of which is connected to point P5 in FIG. 6. This counter 63 starts from 0 at the start of the motor control pulse and its content, represented by the states of its outputs QO to Q3, is representative of the integral f Ui.dt, a value proportional to the energy received and delivered by the motor.

The content of the counter 63, can itself be compared, using a comparator 64, to a set value. For this purpose, the outputs of the counter 63 are connected to the inputs B of a comparator 64 whose inputs A receive the set value. The output B> A of comparator 64 can then be used for example to interrupt the motor control pulse.

If the setpoint is not reached during the duration of the motor control pulse, it is feared that the rotor has not taken its step, and an additional driving pulse can be sent, at high energy, to ensure the passage of the rotor.

There are of course many other combinations for analyzing the sequence of logic states delivered by the motor control circuit (FIG. 4), and the values of Ui, U _R or S Ui. dt which result from the analysis of this sequence allow, by measuring the rotor passage time or the effective energy received by the motor, to adapt the duration of the control pulses using the appropriate control circuits. load the engine, detect steps not taken or control the engine at a fast rate.

In general, these control circuits cannot be dissociated from the control circuit. Thus, in a watch, the control circuits of FIG. 4 and the control circuits of FIGS. 6 and 7 would be incorporated into the integrated circuit of the watch, which is why these control circuits must be relatively simple and inexpensive.

On the other hand, during manufacture or repair, it may be advantageous to carry out more precise measurements using more advanced circuits, capable of being incorporated into a measuring device external to the watch, the latter making it possible to measure certain parameters relating to the operation of the stepping motor by analyzing the sequence of logic states delivered by the motor control circuit. However, this sequence of logic states is directly present at the terminals of the motor. It therefore suffices to connect a probe to one or other of the terminals thereof to introduce this sequence of logic states into the measuring device. This device must then include analysis means similar to those of the circuits of FIGS. 6 and 7, making it possible to extract the values of Ui, U _R or of f Ui.dt. It is in fact only an extension of the device according to the invention, part of this device then being in the watch and the other part in the other part in the external measuring device. It is also necessary to provide means for connecting these two parts, means making it possible to reconstruct and analyze in the second part the sequence of logical states generated by the first. In the case where a probe is used, these means are reduced to a simple input amplifier. In FIG. 8 is shown a second embodiment of a device using a pick-up coil to detect the signals emitted by the driving coil and to reconstruct using these the sequence of logic states produced by the circuit. . This makes it possible, for example, to check an already fitted watch and the motor terminals of which are inaccessible.

In all cases, that is to say whether the coupling is inductive or glavanic, it is also necessary to provide a secondary generator synchronized by the signals picked up on the motor, this generator delivering the reference or clock signals necessary for the correct analysis of the sequence of logical states. In Figure 8 is shown the coil 70 of the motor and the sensing coil 71 of the device. On the driving coil 70 (transmitting coil) are the all-or-nothing signals with very steep sides of the sequence of logic states to be reconstructed. These steep sides can be detected by deriving the signal picked up by the coil 71, by means of a capacitor 72 connected to the input of an inverting amplifier 73, and of a resistor 74 connected between the capacitor 72 and the output of amplifier 73. At the output of this amplifier, positive or negative pulses appear. The polarity of these pulses depends on the direction of the current in the drive coil and the position of the pickup coil relative to the motor coil. It is therefore not possible to certify that a positive pulse corresponds to the establishment of the current in the coil and vice versa.

The positive pulses at the output of amplifier 73 are amplified by an NPN transistor 75, the base of which is connected to the output of amplifier 73 by a capacitor 76 and to ground by a resistor 77. The collector of transistor 75 is connected to the positive pole of the power supply by a resistor 78 and to the input of an inverter 79. For any positive pulse of more than 0.7 Volts (transistor threshold voltage) at the output of the amplifier 73, transistor 75 becomes conductive and produces a negative pulse on its collector at the input of inverter 79. The output of inverter 79 delivers a positive pulse at input a of an OR gate 80, of which the output also delivers a positive pulse. The negative pulses at the output of the amplifier 73 are amplified by a transistor 81 of PNP type, the base of which is connected to the output of the amplifier 73 by a capacitor 82 and to the positive pole of the power supply by a resistor 83 The collector of transistor 81 is connected to ground (negative pole of the power supply) by a resistor 84 and to input b of the OR gate 80.

For any negative pulse of more than 0.7 Volts at the output of the amplifier 73, the transistor 81 becomes conductive and produces a positive pulse on its collector, the output of the gate 80 also delivering a positive pulse. This circuit makes it possible in a way to "rectify" the pulses delivered by the amplifier 73, the output of the gate 80 delivering a positive pulse for each pulse at the output of the amplifier 73, whatever its polarity. These pulses make it possible to synchronize an internal generator comprising in this example a high frequency generator (4 MHz) 85 and a divider 86 delivering inter alia a signal of 32768 kHz which is synchronized with the internal generator of the watch by the fact that the output of door 80 is simply connected to the reset input of this divider 86. The output of door 80 is also connected to the clock input a of a D-type flip-flop, 87, operating in binary divider by 2, its output Q being connected to its input D (c).

We know that, in the motor coil, the coil supply times are necessarily followed by short-circuit times, just as in a divider by 2, the states "1" are necessarily followed by states "0 ". It is therefore sufficient to synchronize the signals at the terminals of the coil 70 and at the output of the flip-flop 87 so that the state "1" at the output of the latter corresponds to the state of feed drive coil and that the state "0" corresponds to the short-circuit state of this coil. We also know that the motor control pulses are short (2 µs) compared to their repetition period (30 µs). Therefore, the supply time of the coil is on average much shorter than the time during which it is short-circuited, the short-circuit being additionally maintained between two control pulses of the motor. To synchronize the output Q (e) of the flip-flop 87, it is sufficient to connect this output by a resistor 88 of high value to the reset input (d) of this same flip-flop, the latter being connected. to ground by a capacitor 89 of high value. The RC circuit 88,89 delivers across the capacitor 89 the average value of the voltage at the output Q of the flip-flop 87. If this average voltage is too high, this means that the states "1" are more numerous than the states "0", and that the output signal from flip-flop 87 is out of phase. The high voltage on the reset input of flip-flop 87 then causes this flip-flop to toggle, which re-establishes the correct phase relationship.

Thus, on the outputs of the flip-flop 87 and of the divider 86, there are respectively suitably reconstructed logic states delivered by the control circuit and properly synchronized clock signals. This sequence of logic states and these signals then allow the use of analysis circuits such as those which have been described in connection with FIGS. 6 and 7. These circuits make it possible inter alia to know the values of Ui / V and of U _{R /} V.

dt. Toutes ces valeurs sont donc mesurables simplement en branchant une sonde sur une borne du moteur, ou mieux, en posant celui-ci sur un capteur comprenant une bobine captrice appropriée.By entering the values of V and Rb (supply voltage and resistance of the driving coil) it is possible to calculate the values of 1 ⁼ (U _R / V) (V / Rb) = U _R / R _b and current consumed by the motor, I _c = I _o [(U _i / V) + (U _{R /} V)] as well as the electrical energy actually received by the motor, w = f Ui.Io.dt = Io.Vf

dt. All these values can therefore be measured simply by connecting a probe to a motor terminal, or better, by placing the latter on a sensor comprising an appropriate pickup coil.

A last interesting aspect of the device according to the invention is described in FIG. 9. It relates to the possibility of programming at will the reference current Io fixing the tripping level of the discriminator of the current level in the driving coil. This can be done simply by replacing the resistor R1 in FIG. 4 with a programmable current source, such as that which is represented in FIG. 9.

This device comprises a circuit delivering a reference current formed by transistors of the P-MOS 90 and 91 type. The source of the P-MOS transistor 90 is connected to the positive pole of the power supply, its drain is connected to ground by a resistor. of great value 92 and at the gate of the P-MOS type transistor, 91; its gate is connected to the positive pole of the power supply by a resistor R2 and to the source of transistor 91. The drain of transistor 91 is connected to the gate and to the drain of an N-MOS, To type transistor, the source is connected to ground. The P-type transistors 90 and 91 form a regulator maintaining the voltage across the resistor R2 equal to the threshold voltage V _T of the transistor 90.

Indeed, if the voltage across the resistor R2 increases, the current in the transistor 90 also increases, the voltage drop in the resistor 92 increases and the current in the transistor 91 decreases, which lowers the voltage at the terminals of R2. The opposite process occurs if the voltage across the resistor R2 decreases, so that this voltage is stabilized at the value of the threshold voltage V _T of the transistor 90. The reference current thus produced is equal to I _{R =} V _{T /} R2. This current flows entirely through transistor 91 and transistor To, determining on the latter a reference gate-source voltage, voltage for which the drain-source current of transistor To is equal to I _R. This reference voltage across the terminals of transistor To is applied between gate and source of four N-MOS type transistors Tl, T2, T4 and T8, dimensioned so as to deliver between drain and source portable currents at I _R , these currents increasing in geometric progression.

Thus the transistor Tl delivers a current I _R , the transistor T2 a current 2 I _R , and the transistors T4 and T8 of the respective currents 4 I _R and 8 IR. The drain of transistor Tl is connected to the source of an N-MOS type transistor 96 whose gate is connected to the output QO (a) of a reversible counter 97. The drain of the N-MOS type transistor T2, is connected to the source of the N-MOS type transistor 95 whose gate is connected to the output Q1 (b) of the counter 97. The drain of the N-MOS type transistor, T4, is connected to the source of a transistor of the N-MOS 94 type, the gate of which is connected to the output Q2 (c) of the counter 97 and the drain of the N-MOS type transistor, T8, is connected to the source of an N-MOS type transistor 93 of which the grid is connected to the output Q3 (d) of the counter 97. The drains of the type transistors N-MOS 93 to 96 are connected together at the common point P6. These transistors 93, 94, 95 and 96 act as switches, letting the currents delivered respectively by the transistors T8, T4, T2 and Tl, when their gate is at "1".

The current Io at common point P6 is the sum of the individual currents, its value depending on the logic states at the outputs QO to Q3 of the reversible counter 97. It is visible that if this counter 97 is at 0, the current Io is zero, the transistors 93.94.95 and 96 are all blocked. On the other hand if the content of the counter 97 is at the maximum (1111), the transistors 93 to 96 are all conductive, and the current Io on P6 takes the value: Io = I _R + 2 I _R + 4 I _R + 8 I _R = 15 I _R.

The value of the current at point P6 therefore depends on the content of the counter 97, according to the relation Io = xI _R where x is the content of the counter.

The circuit of FIG. 9 is therefore indeed a programmable current source. By replacing the resistor R1 in FIG. 4 with this current source, it is therefore possible to program the current level in the drive coil as desired. It is obvious that the grids of the transistors 93, 94, 95, 96 could also be connected to the outputs of any type of memory (ROM, RAM, REPROM, etc.).

In the circuit of FIG. 9, the reversible counter 97 has been used to show that the programming of the current Io can be used in a complementary servo system making it possible to dose exactly the number of ampere-turns necessary for the motor rotor to take his step in a fixed time.

For this, the clock input e of the counter 97 is connected to the output of an inverting amplifier 98, the input of which receives the motor control pulses on P3 in FIG. 4, the U / D input for controlling the counting direction (f) of the counter 97 receiving a signal of 64 Hz from the divisor 11 of figure 4. We admit thereafter that the system comprises the circuit of figure 6, making it possible to interrupt the control pulse of the motor when the step is taken. The duration of this control pulse is therefore variable and it represents the time necessary for the rotor to perform its pitch.

If the requested torque is low, this time will be short. If the requested torque is high, this time will be longer. Suppose that we are in the first case, and that the command pulse has a duration of 6 ms.

The 64 Hz signal on the U / D input changes to "1" after 8 ms, le. counter 97 changes at the end of the motor control pulse on its clock input, that is to say when the U / D input is still at "0". The counter then counts a step, its content decreasing by one, as well as the current Io. At the next command pulse, the number of ampere-turns (NIo, where N = number of turns of the driving coil) received by the motor will be lower, so that the rotor will take a longer time to perform its pitch , for example 7 ms. At the end of the command pulse, the U / D input is always at "0" and the counter counts down a new step so that the current Io decreases by one more. On the next command pulse, the rotor will therefore take even longer to take its step, 8.5 ms for example. In this case, at the end of the command pulse, the U / D input has changed to "1". The counter therefore advances by 1 step and the current increases by one unit, so that the duration of the next step will be shortened, the number of ampere-turns and consequently the cut of the motor being increased. It is therefore an automatic stabilization of the duration of the control pulse °, and consequently of the rotor passage time, around 8 ms, and this also in the event of variations in the load torque of the engine.

This combination of circuits makes it possible to always work the engine in optimum conditions and thus save appreciable energy. When the engine load is low, the number of ampere-turns is automatically reduced, which automatically decreases the starting torque. This avoids imposing too much acceleration on the engine, the energy spent for the latter being lost anyway.

It is clear that the examples given in Figures 6,7,8 and 9 represent only a part of the possibilities allowing the analysis of the sequence of logic states and the adjustment of the operation of the motor by the device according to the invention.

Claims (33)

1. Control device of a stepping motor provided with a coil and a rotor subjected to a rotational movement when the coil is traversed by a current, characterized in that it comprises means for providing a plurality of time base signals, means for producing, in response to time base signals, motor control pulses, means responsive to the control pulses for supplying the motor by maintaining the current in the coil at a substantially constant value determined during the duration of the control pulses, means for taking a signal representative of the voltage signal present on the coil and analysis means for supplying, from the signal representative of the voltage signal, at least one information on the voltage induced in the coil by the movement of the rotor. 2. Device according to claim 1, characterized in that the means for supplying the motor include switching means for connecting the coil to a supply voltage source and for short-circuiting said coil and means for periodically comparing, during each control pulse, the current in the coil to a reference value and supply a control signal to control said switching means, in order to short-circuit the coil when, during a comparison, the current exceeds the value of reference and supplying voltage to said coil if the current is less than this value, this until the next comparison, so as to maintain the average value of said current at said reference value for the duration of said control pulses. 3. Device according to claim 2, characterized in that said reference value is a function of the threshold voltage of an MOS transistor, independent of the supply voltage of the motor. 4. Device according to claim 2, characterized in that said control signal is formed by a series of logic states "1" and "0" corresponding to the short-circuit and supply conditions of the coil. 5. Device according to Claim 4, characterized in that the said analysis means receive the said control signal and comprise storage means for storing, in response to the said time base signals, the logic states of a determined number of periods of said control signal, of the first counting means to count, in response to said time base signals, the number of logic states corresponding to the short-circuit condition of the coil in a first group of stored logic states, said first counting means supplying a digital signal at their outputs representative of the ratio of the voltage due to the resistance of said coil to the supply voltage, of the second counting means for counting, in response to said time base signals and at the end of said first group of logic states, the variations of the number of said logic states corresponding to the short-circuit condition of the coil and contained in said storage means, said second counting means supplying at their outputs a digital signal representative of the ratio of the voltage induced in the coil by the movement of the rotor at supply voltage. 6. Device according to claim 5, characterized in that said first storage means comprise a transfer register. 7. Device according to claim 5, characterized in that said second counting means are a reversible counter. 8. Device according to claim 5, characterized in that it further comprises means connected to said second counting means for delivering an end of pulse signal when the ratio of the induced voltage to the supply voltage has a determined value and means for interrupting said control pulse in response to said end of pulse signal. 9. Device according to claim 5, characterized in that it further comprises means for determining the energy consumed by the motor during a step. 10. Device according to claim 9, characterized in that the means for determining the energy consumed by the motor comprise first comparison means for comparing the ratio of the induced voltage to the supply voltage with a periodic digital signal formed of a logical combination of at least a portion of said time base signals, said first comparison means delivering an output signal when the value of said periodic digital signal is less than the value of said ratio, frequency division means at programmable division rate by said ratio of the voltage due to the resistance of the coil to the supply voltage, said frequency division means delivering in response to said time signal a number of signals representative of the energy consumed by the motor, of the third counting means receiving the signals of said frequency division means and delivering at their outputs a digital signal representative of the energy consumed by the motor during of each control pulse. 11. Device according to claim 10, characterized in that it further comprises second comparison means for comparing said digital signal representative of the energy consumed with a set value, said second comparison means delivering an end signal pulse when the value of said signal representative of the energy consumed is greater than the set value, said end of pulse signal being capable of being used to control the duration of the control pulses to the set value. 12. Device according to claim 2, characterized in that it comprises means for programming said reference quantity. 13. Device according to claim 12, characterized in that the means for programming the reference value comprise a reference voltage source controlling a group of transistors dimensioned so as to respectively deliver currents varying in geometric progression, each of said transistors being connected in series with a switching transistor having a control input and an output, the outputs of the switching transistors being connected to a common terminal and the control inputs of said switching transistors being respectively connected to outputs of storage means delivering on these outputs a digital signal determining the conduction or blocking state of said switching transistors so that the sum of the currents of said transistors of said group on said common terminal is representative of said digital signal and, consequently, programmed by this digital signal, said sum of the currents on said e terminal being said reference value. 14. Device according to claim 13, characterized in that said storage means are constituted by a reversible counter having a clock input to which said motor control pulses are applied, the duration of which is likely to vary according to the load of the motor and, a counting direction control input receiving a time base signal having a period related to the time necessary for the rotor to take a step, the output signal of said reversible counter and, consequently, the value of the reference current on said common terminal being a function of the relative durations of the motor control pulse and of said period of the time base signal, the duration of said control pulse being thus controlled by the value of the period of said time base signal and minimum energy consumption even in the presence of load variations. 15. Device according to claim 1, characterized in that it further comprises means coupled to said analysis means for delivering an end of pulse signal when said induced voltage has a determined value and means for interrupting the motor power supply in response to said end of pulse signal. 16. Control device for a stepping motor provided with a coil and a rotor subjected to a rotational movement when the coil is traversed by a current, characterized in that it comprises means for providing a plurality of time base signals, means for producing, in response to time base signals, motor control pulses, switching means responsive to said control pulses for connecting the coil to a voltage source power supply and for short-circuiting said coil and means for periodically comparing, during each control pulse, the current in the coil with a reference value and supplying a control signal for controlling said switching means, in order to short-circuit the coil when, during a comparison, the current exceeds the reference value and supplying voltage to said coil if the current is less than this value, this until the next comparison, so as to maintaining the average value of said current at said reference value for the duration of said control pulses. 17. Device according to claim 16, characterized in that said reference value is a function of the threshold voltage of a MOS transistor, independent of the supply voltage of the motor. 18. Device according to claim 16, characterized in that said control signal is formed by a series of logic states "1" and "0" corresponding to the short-circuit and supply conditions of the coil. 19. Device according to claim 18, characterized in that it further comprises means for analyzing said control signal during the duration of the motor control pulses and for provide at least one digital signal representative of the voltage induced in the coil by the movement of the rotor. 20. Device according to claim 19, characterized in that the means for analyzing the control signal comprise storage means for storing, in response to said time base signals, the logic states of a determined number of periods of said control signal, first counting means for counting, in response to said time base signals, the number of logic states corresponding to the short-circuit condition of the coil in a first group of memorized logic states, said first counting means delivering at their outputs a digital signal representative of the ratio of the voltage due to the resistance of said coil to the supply voltage, second counting means for counting, in response to said time base signals and at the end of said first group of logic states, the variations in the number of said logic states corresponding to the short-circuit condition of the coil and contained in said storage means , said second counting means delivering at their outputs a digital signal representative of the ratio of the voltage induced in the coil by the movement of the rotor to the supply voltage. 21. Device according to claim 20, characterized in that said first storage means comprise a transfer register. 22. Device according to claim 20, characterized in that said second counting means are a reversible counter. 23. Device according to claim 20, characterized in that it further comprises means connected to said second counting means for delivering an end of pulse signal when the ratio of the induced voltage to the supply voltage has a determined value and means for interrupting said control pulse in response to said end of pulse signal. 24. Device according to claim 20, characterized in that it further comprises means for determining the energy consumed by the motor during a step. 25. Device according to claim 23, characterized in that the means for determining the energy consumed by the motor comprise first comparison means for comparing the ratio of the induced voltage to the supply voltage with a digital signal periodic formed from a logical combination of at least a portion of said time base signals, said first comparison means delivering an output signal when the value of said periodic digital signal is less than the value of said ratio, the duration of said signal output being representative of the value of said ratio, frequency division means with programmable division rate by said ratio of the voltage due to the resistance of the coil to the supply voltage, said frequency division means delivering in response to said output signal of said first comparison means and to said time base signals a number of signals representative of the energy consumed by the motor, of the third counting means receiving the signals from said frequency division means and delivering to their outputs a signal digital representative of the energy consumed by the motor during each control pulse. 26. Device according to claim 24, characterized in that it further comprises second comparison means for comparing said digital signal representative of the energy consumed with a set value, said second comparison means delivering an end signal pulse when the value of the signal representative of the energy consumed is greater than the set value, said end of pulse signal being capable of being used to control the duration of the control pulses to the set value. 27. Device according to claim 16, characterized in that it comprises means for programming said reference value. 28. Device according to claim 26, characterized in that the means for programming the reference value comprise a reference voltage source controlling a group of transistors dimensioned so as to respectively deliver currents varying in geometric progression, each of said transistors being connected in series with a switching transistor having a control input and an output, the outputs of the switching transistors being connected to a common terminal and the control inputs of said switching transistors being respectively connected to outputs of storage means delivering on these outputs a digital signal determining the conduction or blocking state of said switching transistors so that the sum of the currents of said transistors of said group on said common terminal is representative of said digital signal and consequently programmed by this digital signal, said sum of the currents on said terminal being said reference value. 29. Device according to claim 27, characterized in that the said storage means consist of a reversible counter having a clock input to which the said motor control pulses are applied, the duration of which is likely to vary according to the motor load and a counting direction control input receiving a time base signal having a period related to the time required for the rotor to take a step, the output signal of said reversible counter and, consequently, the value of the reference current on said common terminal, being a function of the relative durations of the motor control pulse and of said period of the time base signal, the duration of said control pulse being thus controlled by the value of the period of said signal time base and minimum energy consumption even in the presence of load variations. 30. Device for reconstituting the control signal according to claim 16, characterized in that it comprises means for picking up signals in the motor coil, shaping means delivering for each picked up signal a positive pulse to their output, means producing time base signals synchronized by said output pulses, shaping means and switching means for producing a series of logic states representative of said control signal in response to said output pulses. 31. Device according to claim 29, characterized in that said capture means comprise a pick-up coil. 32. Device according to claim 29, characterized in that said means producing time base signals are a high frequency pulse generator associated with a frequency divider delivering said time base signals, the reset input at zero of said divider being controlled by said output pulses so as to ensure said synchronization. 33. Device according to claim 29, characterized in that said switching means comprise a flip-flop whose output is connected to the reset input by a high value resistor, the reset input being connected to the power supply pole by a high value capacitor.

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