ATBECHDE..ESFRGBGRITLILUNLSE......................JDIM360 - Ver 2.5 (21 Aug 1997) 2100000/00305344EUROPEAN PATENT SPECIFICATIONB119920102EP88830336.9198808021989033119900117itenen677308719870825IT199201021992011989030119890919920102199201199102075 5F 02D 41/20 A 5H 03K 17/04 BdeSchaltung zum Ansteuern von induktiven Lasten, insbesondere zum Antreiben von Elektro-Einspritzventilen eines DieselmotorsenA circuit for the piloting of inductive loads, particularly for operating the electro-injectors of a diesel-cycle internal combustion enginefrCircuit de commande de charges inductives, en particulier pour actionner des injecteurs électriques d'un moteur dieselEP-A- 0 034 076EP-A- 0 106 743DE-A- 3 324 937FR-A- 2 533 263FR-A- 2 538 942GB-A- 2 182 815US-A- 3 896 346Calfus, MarcoStrada Superga, 298I-10132 TorinoITMARELLI AUTRONICA S.p.A.00454643E680-GQVia Griziotti 420145 MilanoITQuinterno, Giuseppeet al00051431c/o JACOBACCI & PERANI S.p.A. Corso Regio Parco, 2710152 TorinoITATBECHDEESFRGBGRITLILUNLSE19890301198909

The present invention relates to a circuit for the piloting of inductive loads, and particularly for the control of the electro-injectors of a diesel-cycle internal combustion engine, of the kind defined in the preamble of the amended Claim 1.

FR-A-2533263 discloses a circuit of this type for driving the fuel injectors in the engine of a motor-vehicle. This known circuit is capable of operating the injectors properly also at very high rotational speeds, but this is possible only if the voltage supply is capable of delivering a sufficient current.

When a circuit of the above-defined kind is used for piloting the injectors of an engine, the voltage supply is typically constituted by the battery of the motor vehicle. In some circumstances, this battery is unable to deliver a sufficiently high current for the piloting circuit to be able to energise the electro-injectors in the desired manner. This may occur, for example, when the battery is not sufficiently charged or when, for various reasons, the impedance "felt" by the battery is unusually high. In such a situation, the prior-art circuit described above is unable to pilot the electro-injectors in a satisfactory manner.

It is therefore an object of the present invention to produce a circuit of the type specified above which is able to ensure the correct functioning of the electro-injectors even when the supply is unable to deliver a current of sufficiently high intensity.

This object is achieved according to the invention by means of a circuit of the type specified above, having the features defined in the characterising portion of Claim 1.

Further advantages of the present invention will become clear from the detailed description which follows with reference to the appended drawings, provided by way of non-limiting example, in which:

With reference to Figure 1, a circuit according to the invention for the piloting of a plurality of inductive loads Li comprises an input terminal 1 connected in use to a low-tension, direct-voltage supply VB, such as a battery. In particular, the inductive loads Li may represent the solenoids for operating the electro-injectors of a diesel engine for a motor vehicle.

In this case, the supply VB is constituted by the battery of the motor vehicle.

A storage coil, indicated L₁, can be connected to the input terminal 1 through a controlled electronic switch, generally indicated SW₁, which is open at rest. The switch SW₁ has been shown as an interrupter with which a diode D₁ is connected in parallel. This switch may be be constituted, for example, by an integrated MOSFET-type transistor, and in that case the diode D₁ is constituted by its parasitic diode.

A diode whose anode is connected to earth and whose cathode is connected between the storage coil L₁ and the controlled switch SW₁ is indicated R₁.

A further controlled switch SW₂, similar to SW₁ is connected between L₁ and earth in the manner illustrated.

L₁ is connected to a first terminal of a capacitor C whose other terminal is connected to earth. A plurality of branch circuits is connected in parallel with C and each includes an inductive load Li in series with which a controlled electronic switch SWi of a similar type to SW₁ and SW₂ is connected. A respective capacitor Ci may be connected in parallel with each load Li for quenching it, that is, for rapidly cancelling out the current in the corresponding load Li when the latter is deactivated.

A resistor and a capacitor, indicated Rc and Cc, are connected in parallel with each other between the earth and a junction N to which are connected the cathodes of diodes Dc, each of which has its anode connected between a load Li and the associated controlled switch SWi. The diodes Dc together form an OR-type circuit.

A further controlled switch SW₄, similar to the above, is connected between the junction N and the input 1.

An electronic control unit produced in known manner is indicated ECU and comprises, for example, a microprocessor unit and input/output interface circuits. The unit ECU has a series of inputs connected to the earth of the circuit described above, to the positive pole of the supply VB, and to a sensor S which is adapted to provide electrical signals indicative of the current flowing in the storage coil L₁ during operation. The sensor S may be constituted, for example, by a Hall-effect sensor. As an alternative to this solution, the non-earth terminal of the capacitor C may be connected to the unit ECU for detecting the current flowing in L₁: the voltage established across the terminals of C at particular stages of operation is related to the intensity of the current flowing in L₁.

A further alternative solution for the detection of the current flowing in L₁ could be constituted, for example, by a shunt resistor connected in series with L₁ and connected to the ECU.

The unit ECU has a plurality of outputs connected in order to the control inputs of the switches SW₁, SW₂, SW₃ and SWi.

In order to pilot the electro-injectors of a diesel engine, the unit ECU may be provided with further electrical input signals, such as, for example, the rate of revolution of the engine, etc.

Before describing the operation of the circuit shown in Figure 1, some considerations concerning the ideal trace of the current ILi in the solenoid for operating an electro-injector for a diesel engine will be put forward. This ideal behaviour is shown in Figure 2 as a function of time t. The ideal curve illustrated has a rising slope a followed by a stage b of substantially constant high-current intensity Imax, followed by a transition c towards a holding current level Ih. This current is maintained for a certain period of time (section d of the curve) and is then followed by the "quenching" of the current (stage e) with possible inversion and definitive cancelling out of the current (stage f).

For optimal and exact control of the injection it is necessary that the actuation time of individual injectors be precisely controllable. For this purpose, therefore, it is necessary that the times during which the current rises and subsequently falls are extremely short, and less than the minimum injection time by at least one order of magnitude.

With reference to Figures 1, 3 and 4, we shall now see how the circuit according to the invention is able to make the current rise rapidly in a particular load each time that load is to be activated.

Figure 3 shows the states of SW₁, SW₂ and of the switch SWi associated with the load Li to be energised, and the traces of the current IL1 in the storage coil, of the voltage VC across the capacitor C and of the current ILi in the load.

In order to make a current pass into the load Li, the unit ECU causes the switches SW₁ and SW₂ to close at a time tO. All the other switches remain open. In this condition, an increasing current flows in the storage coil L₁, as shown in Figure 3.

At a subsequent time t₁, SW₁ and SW₂ are opened, whilst the switch SWi associated with the load to be energised is closed. In this condition, the storage inductor L₁ is disconnected from the supply but is connected to the capacitor C with which it forms a resonant circuit. This resonant circuit is discharged to the load Li associated with the switch SWi which is closed. The current ILi decays in the manner illustrated, whilst the voltage across the capacitor C(i) increases and then decreases until it reaches zero at a time t₂. The current in the selected load therefore increases from the time t₁ until it reaches a maximum value at the time t₂, and then starts to decay, as shown in Figure 3. In order to extend the period for which the current persists at high-intensity levels in the load, the unit ECU may be arranged to cause successive openings and closings of SW₁ after the time t₂, with resultant "chopping" of the current ILi, as shown by the broken line in Figure 3.

The rapid transfer of energy from the supply to the generic load Li by means of storage in L₁ and the consequent discharge of the resonant circuit L1-C can be achieved, provided that the supply VB is able to deliver a current of sufficient intensity.

According to the invention, the control unit ECU may be arranged to detect the intensity of the current which can be delivered by the supply. This may be achieved by the acquisition of the signals provided by the sensor S, or by the reading of the voltage across C when SW₁ and SW₂ are open, or even by the reading of the voltage across a shunt resistor arranged in series with the storage coil L₁. When the current delivered by the supply is less than a predetermined value, the unit ECU can also determine (and possibly signal for diagnostic purposes) whether the inadequacy of the current is due to a low charge level of the supply or to an anomaly in the circuitry connected to the supply, by reading the voltage VB of the supply.

In any case, when the unit ECU detects that the current which can be delivered by the supply is less than a predetermined threshold, it puts into operation a second procedure for the transfer of current to the load Li selected from time to time. In this procedure, which will now be described with reference to Figures 1 and 4, the unit ECU causes successive simultaneous closures of SW₁ and SW₂, as indicated at the times t₀, t₂ and t₄ in Figure 4. The switches SW₃ and SWi, however, are kept open.

Upon each closure of SW₁ and SW₂, the current in the storage coil Li increases until, as at the times t₁, t₃ and t₅, the switches are opened. Upon each opening of SW₁ and SW₂, the voltage across the capacitor C is increased. The diode R₂ prevents the discharge of C during the stage of storage in L₁. The diode P₂ also serves to protect SW₂ when the capacitor C is subsequently discharged.

The voltage across C therefore rises in steps and can be brought to a level greater than that of the supply, until a level VS is reached (Figure 4) which is sufficient to cause the rapid passage of a high current to the selected load. This injection of current takes place at the time t₆ in Figure 4 (which, at the limit, may be made to coincide with ts) when the switch SWi associated with the selected load is closed while all the other switches are open.

The first operating mode of the circuit of Figure 1, described with reference to Figure 3, is preferable since it is more convenient from an energy point of view. However, this operating mode is only possible if the supply is able to deliver sufficent current. When this does not occur, the circuit according to the invention nevertheless enables a rapid injection of current to the loads to be achieved by the charging and subsequent discharging of the capacitor C, as described with reference to Figure 4. The charging of C obviously takes a certain time, which depends on the intensity of the current which can be delivered by the supply. The unit ECU is correspondingly programmed to start the charging of C correspondingly in advance of the time (t₆ in Figure 4) at which the passage of current to the selected load must be triggered.

In practice, the circuit of Figure 1 requires a single large-capacitance capacitor (the capacitor C) which is used for the injection of the current to the loads Li in a predetermined sequential order actuated by the unit ECU by means of corresponding sequential piloting of the switches SWi.

Capacitors Ci of considerably smaller capacitance are consequently sufficient to achieve any final inversion of the current in the loads.

Two ways in which the circuit of Figure 1 can cause a current to pass rapidly into a generic load to achieve the portions a and b of the ideal curve of Figure 2 have been described above. This current can be made to flow at the desired holding level (section d of the ideal curve shown in Figure 2) by the opening of the switch SW₁ or the switch SWi associated with the load. In order subsequently to cancel out the current ILi (stage 2) SWi is opened. In this condition, a voltage is developed across the load which rises to high values in a short time. A clamping circuit is provided for limiting the value of this voltage and is constituted by the capacitor Cc to which the resistor Rc can be connected. It should be noted that this is a single circuit connected to all the loads Li by means of the diodes Dc which are connected so as to form an OR circuit.

Together with the switch SW₃, the "clamping" circuit described above also enables the partial recovery of the reactive energy of the load which is excited from time to time, enabling this energy to be recycled towards the supply VB. This energy recovery, which will now be described, takes place essentially each time a switch SWi is opened after the injection of current to the associated load L. This can occur essentially in three circumstances, that is, when the current in the load Li is changed from the maximum level to the holding level (section c of the ideal curve of Figure 2), when the current in the load is quenched (section e of Figure 2) and, although to a lesser extent, during the stages when the current in the load is being chopped, such as, for example, those described with reference to Figure 3.

Figure 5 shows examples of the traces of the current Ii in a load and of the voltage Vc across the clamping capacitor, and the corresponding stages of the switch SWi associated with the load in question and of the switch SW₃. With reference to this Figure, when, at a time t₀, SW₃ is closed as a result of a command provided by the unit ECU and the switch SWi associated with the energised load is closed, the current ILi decays, whilst the voltage across the clamping capacitor rises. When the current IH is reached in the load (a condition which can be detected by the unit ECU, for example, by means of a further Hall-effect sensor associated with Li) at the time t₁, the unit ECU causes the switch SWi which was previously been opened, to close again and opens SW₃. In these conditions, the clamping capacitor remains charged at the voltage to which it has previously been brought.

When, at the time t₂, the unit ECU subsequently opens SWi, the current in the load decays rapidly, whilst the voltage Vc across the clamping capacitor rises rapidly, as shown in Figure 5, until the unit ECU closes SW₃ at the time t₃ and the voltage VC consequently decreases rapidly.

During the stages when the current in the load which is energised from time to time is decaying, the closure of SW₃ enables part of the reactive energy stored in the load to be returned to the supply, by virtue of the concomitant action of the clamping circuit.

This characteristic may be of considerable interest for applications of the circuit according to the invention in the automotive field, particularly in motor cars provided with batteries and/or with relatively low power-recharging systems.

As far as Rc is concerned, this is only necessary (to dissipate the energy stored in Cc) if the circuit according to the invention is not arranged to recover the reactive energy. In this case, resistors, each connected in parallel with a diode Dc, may be provided in place of Rc.

Further possible applications of the circuit according to the invention are, for example, for controlling the relays which scan the punched cards or tapes in Jacquard-type textile machines, for controlling the electro-injectors of an Otto-cycle engine, for controlling the printing heads of matrix printers, etc.

 1. A circuit for the piloting of inductive loads (Li), particularly for operating the electro-injectors of a diesel-cycle internal combustion engine, comprising: an input (1) for connection to a low-tension supply (VB), a storage coil (L₁) for storing energy delivered by the supply (VB), and electronic switching means (SW₁, SW₂, SWi) for controlling the connection between the input (1), the storage coil (L₁) and each of the loads (Li) in a predetermined manner to achieve a rapid transfer of current to each of the loads selectively, a capacitor (C) which is arranged in parallel with the branch circuits containing the loads (Li), and which is connected to the coil (L₁) and the electronic switching means (SW₁, SW₂, SWi), and an electronic control unit (ECU) for piloting the electronic switching means (SW₁, SW₂, SWi) according to a first operative mode in which, to transfer current into one of the loads (Li), the switching means cause in succession, after the connection of the storage coil (L₁) to the supply (VB): the connection of the storage coil (L₁) to the capacitor (C) so as to form a resonant circuit, and then the discharge of the resonant circuit (L₁, C) into the load (Li);
characterised in that it also includes sensor means (S) for providing electrical signals indicative of the current delivered by the supply (VB), and in that the control unit (ECU) is connected to the sensor means (S) and is arranged to pilot the electronic switching means (SW₁, SW₂, SWi) in the first operative mode when the current delivered by the supply is greater than a predetermined value and in a second operative mode when the current delivered by the supply is less than a predetermined value; the unit (ECU) and said switching means (SW₁, SW₂) being adapted to control the connection of the capacitor (C) and of the storage coil (L₁) to the supply (VB) so as to form a voltage-boosting means (C, L₁, R₂) in the second operative mode, so as to charge the capacitor (C) to a predetermined voltage level greater than the voltage of the supply, and then the discharge of the energy stored in the capacitor (C) into a selected load (Li). 2. A circuit according to Claim 1, further including a current-inversion capacitor (Ci) in parallel with each load (Li) for enabling the current in the corresponding load (Li) to be cancelled out rapidly, characterised in that each of the inversion capacitors (Ci) has a smaller capacitance than that of the said capacitor (C). 3. A circuit according to Claim 1, characterised in that the sensor means comprise a shunt resistor in series with the storage coil (L₁). 4. A circuit according to Claim 1, characterised in that the sensor means comprise a galvanometric-effect sensor (S), particularly a Hall-effect sensor. 5. A circuit according to Claim 1, characterised in that the control unit (ECU) is adapted to detect the voltage across the capacitor (C). 6. A circuit according to any one of the preceding claims, comprising a plurality of branch circuits in parallel with each other, each of which includes a load (Li), and in which the electronic switching means comprise a first switch (SW₁) between the supply (VB) and the storage coil (L₁), a second switch (SW₂) in parallel with the branch circuits, and a control switch (SWi) in each of the branch circuits, between the corresponding load (Li) and the supply (VB),
characterised in that it also includes clamping circuit means (Rc, Dc) for limiting and possibly dissipating the voltage generated by each of the loads (Li) when the associated control switch (SWi) cuts off the current flowing into the load (Li). 7. A circuit according to Claim, 6, characterised in that the clamping circuit means comprise a clamping circuit of the parallel-RC type, and in that the loads (Li) are connected to the clamping circuit by means of an OR circuit (Dc). 8. A circuit according to any one of the preceding claims, characterised in that it also includes energy-recovery circuit means (SW₃, Rc, Cc) controlled by the unit (ECU) and adapted to enable part of the reactive energy stored in the load (Ri) to be recycled towards the supply (Vb) each time a load (L) is deactivated. 9. A circuit according to Claims 7 and 8, characterised in that the recover circuit means include a further electronic switch (SW₃) connected between the clamping circuit (Rc, Cc) and the supply (VB) and controlled by the electronic unit (ECU). 1. Schaltung zum Ansteuern von iduktiven Lasten (Li), insbesonders zum Antreiben von Elektroeinspritzventilen eines Dieselmotors mit: ― einem Eingang (1) für den Anschluß an eine Niederspannungsversorgung (VB), ― einer Speicherspule (L₁) zum Speichern der von der Versorgung (VB) gelieferten Energie, und ― elektronischen Schaltern (SW₁, SW₂, SWi) zur Steuerung der Verbindung zwischen dem Eingang (1), der Speicherspule (L₁) und jeder Last (Li) in einer vorbestimmten Weise, um eine schnelle Übermittlung von Strom zu jeder der ausgewählten Lasten zu erreichen, ― einem Kondensator (C), der parallel zu den die Lasten (Li) enthaltenden Zweigschaltungen angeordnet ist und der mit der Spule (L₁) und den elektronischen Schaltern (SW₁, SW₂, SWi) verbunden ist, und ― einer elektronischen Steuereinheit (ECU) zum Ansteuern der elektronischen Schalter (SW₁, SW₂, SWi) gemäß einem ersten Betriebsmodus, bei dem die Schalter, um Strom in eine der Lasten (Li) zu leiten, nach dem Verbinden der Speicherspule (L₁) mit der Versorgung (VB) in Aufeinanderfolge bewirken:
die Verbindung der Speicherspule (L₁) mit dem Kondensator (C), so daß ein Schwingkreis gebildet wird, und anschließend die Entladung des Schwingkreises (L₁, C) in die Last (Li); dadurch gekennzeichnet, daß sie außerdem Sensoren (S) umfaßt, welche dazu dienen, elektrische Signale zu erzeugen, die den von der Versorgung (VB) gelieferten Strom anzeigen, und daß die Steuereinheit (ECU) mit den Sensoren (S) verbunden und dazu vorgesehen ist, die elektronischen Schalter (SW₁, SW₂, SWi) in dem ersten Betriebsmodus anzusteuern, wenn der von der Versorgung gelieferte Strom höher ist als ein vorbestimmter Wert, und in einem zweiten Betriebsmodus, wenn der von der Versorgung gelieferte Strom niedriger ist als ein vorbestimmter Wert; wobei die Einheit (ECU) und die besagten Schalter (SW₁, SW₂) dazu geeignet sind, die Verbindung des Kondensators (C) und der Speicherspule (L₁) mit der Versorgung (VB) so zu steuern, daß in dem zweiten Betriebsmodus ein spannungserhöhendes Glied (C, L₁, R₂) gebildet wird, so daß der Kondensator (C) bis auf einen vorbestimmten Spannungspegel, der höher ist als die Versorgungsspannung, aufgeladen wird und anschließend die in dem Kondensator (C) gespeicherte Energie in eine bestimmte Last (Li) entladen wird. 2. Schaltung nach Anspruch 1, die weiters einen mit jeder Last (Li) parallelgeschalteten Kondensator (Ci) umfaßt, der der Stromumkehr dient, um zu ermöglichen, daß der Strom in der entsprechenden Last (Li) schnell gelöscht werden kann, dadurch gekennzeichnet, daß jeder dieser invertierend wirkenden Kondensatoren (Ci) eine geringere Kapazität besitzt als der besagte Kondensator (C). 3. Schaltung nach Anspruch 1, dadurch gekennzeichnet, daß die Sensoren einen mit der Speicherspule (L₁) in Serie geschalteten Parallelwiderstand umfassen. 4. Schaltung nach Anspruch 1, dadurch gekennzeichnet, daß die Sensoren einen auf einem galvanometrischen Effekt beruhenden Sensor (S), insbesonders einen Halleffekt-Sensor umfassen. 5. Schaltung nach Anspruch 1, dadurch gekennzeichnet, daß die Kontrolleinheit (ECU) dazu geeignet ist, die an dem Kondensator (C) anliegende Spannung zu ermitteln. 6. Schaltung nach einem der vorhergehenden Ansprüche, die eine Vielzahl einander parallelgeschalteter Zweigschaltungen umfaßt, von denen jede eine Last (Li) enthält, und bei der die elektronischen Schalter: ― einen ersten Schalter (SW₁) zwischen der Versorgung (VB) und der Speicherspule (L₁), ― einen zweiten Schalter (SW₂) parallel mit den Zweigschaltungen, und ― einen Steuerschalter (SW₁) in jeder Zweigschaltung zwischen der entsprechenden Last (Li) und der Versorgung (VB)
umfassen, dadurch gekennzeichnet, daß sie außerdem als Klemmschaltung wirkende Mittel (Rc, Dc) umfaßt, die der Begrenzung und möglichen Dissipation der von jeder Last (Li) erzeugten Spannung dienen, wenn der zugehörige Steuerschalter (SW₁) den Stromfluß in die Last (Li) unterbricht. 7. Schaltung nach Anspruch 6, dadurch gekennzeichnet, daß die Mittel zur Klemmung aus einer Klemmschaltung vom RC-Parallelschaltungstyp bestehen und daß die Lasten (Li) über eine ODER-Schaltung (Dc) mit der Klemmschaltung verbunden sind. 8. Schaltung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß sie ebenfalls Mittel zur Energierückgewinnung (SW₃, Rc, CC) beinhaltet, die von der ECU-Einheit gesteuert werden und ermöglichen, daß ein Teil der in der Last (Li) gespeicherten reaktiven Energie in die Versorgung (Vb) rückgeführt wird, und zwar jedesmal, wenn eine Last (Li) ausgeschaltet wird. 9. Schaltung nach Anspruch 7 und 8, dadurch gekennzeichnet, daß die der Rückgewinnung dienende Schaltung einen weiteren elektronischen Schalter (SW₃) umfaßt, der zwischen der Klemmschaltung (Rc, Cc) und der Versorgung (VB) angeschlossen ist und von der elektronischen Einheit (ECU) gesteuert wird. 1. Circuit de commande de charges inductives (Li), en particulier pour faire fonctionner des injecteurs électriques d'un moteur à combustion interne à cycle Diesel, comprenant: une entrée (1) pour la liaison à une alimentation à basse tension (VB), une bobine d'accumulation (L₁) pour accumuler de l'énergie fournie par l'alimentation (VB), et des moyens de commutation électronique (SW₁, SW₂, SWi), pour commander de manière prédéterminée la liaison entre l'entrée (1), la bobine d'accumulation (L₁) et chacune des charges (Li), afin d'obtenir un passage rapide, de façon sélective, du courant allant à chacune des charges, un condensateur (C) mis en parallèle avec les circuits de ramification contenant les charges (Li) et relié à la bobine (L₁) et aux moyens de commutation électronique (SW₁, SW₂, SWi), et une unité de commande électronique (ECU) pour commander les moyens de commutation électronique (SW₁, SW₂, SWi) suivant un premier mode de fonctionnement, dans lequel, pour transférer du courant dans l'une des charges (Li), les moyens de commutation provoquent successivement, après la liaison de la bobine d'accumulation (L₁) à l'alimentation (VB): la liaison de la bobine d'accumulation (L₁) au condensateur (C), pour former un circuit de résonance, et, ensuite, la décharge du circuit de résonance (L₁, C) dans la charge (Li);
caractérisé en ce qu'il comprend également un moyen de capteur (S) pour produire des signaux électriques représentatifs du courant fourni par l'alimentation (VB), et l'unité de commande (ECU) étant reliée au moyen de capteur (S) et disposée pour commander les moyens de commutation électronique (SW₁, SW₂, SWi) suivant le premier mode de fonctionnement lorsque le courant fourni par l'alimentation est supérieur à une vapeur prédéterminée et suivant un second mode de fonctionnement lorsque le courant fourni par l'alimentation est inférieur à une valeur prédéterminée; l'unité (ECU) et lesdits moyens de commutation (SW₁, SW₂) étant adaptés pour commander la liaison du condensateur (C) et de la bobine d'accumulation (L₁) à l'alimentation (VB), de façon à former un moyen survolteur (C, L₁, R₂) dans le second mode de fonctionnement, de façon à charger le condensateur (C) à un niveau de tension prédéterminé, supérieur à la tension de l'alimentation, et ensuite à décharger l'énergie stockée dans le condensateur (C) dans une charge (Li) sélectionnée. 2. Circuit selon la revendication 1, comprenant en outre un condensateur à inversion de courant (Ci), placé en parallèle avec chaque charge (Li), pour permettre au courant passant dans la charge (Li) correspondante de tomber rapidement à zéro, caractérisé en ce que chacun des condensateurs à inversion (Ci) présente une capacité inférieure à celle dudit condensateur (C). 3. Circuit selon la revendication 1, caractérisé en ce que le moyen de capteur comprend une résistance de shunt, placée en série avec la bobine d'accumulation (L₁). 4. Circuit selon la revendication 1, caractérisé en ce que le moyen de capteur comprend un capteur à effet galvanométrique (S), en particulier un capteur à effet Hall. 5. Circuit selon la revendication 1, caractérisé en ce que l'unité de commande (ECU) est adaptée pour détecter la tension passant dans le condensateur (C). 6. Circuit selon l'une quelconque des revendications précédentes, comprenant une pluralité de circuits de ramification, placés en parallèle entre eux, chacun comprenant une charge (Li), et dans lequel les moyens de commutation électronique comprennent un premier interrupteur (SW₁) mis en circuit entre l'alimentation (VB) et la bobine d'accumulation (L₁), un second interrupteur (SW₂) mis en circuit en parallèle avec les circuits de ramification, et un interrupteur de commande (SWi) mis en circuit dans chacun des circuits de ramification, entre la charge correspondante (Li) et l'alimentation (VB),
caractérisé en ce qu'il comprend également des moyens circuit de blocage (Rc, Dc), pour limiter et si possible dissiper la tension produite par chacune des charges (Li) lorsque l'interrupteur de commande (SWi) associé coupe le courant passant dans la charge (Li). 7. Circuit selon la revendication 6, caractérisé en ce que le moyen de circuit de blocage comprend un circuit de blocage du type RC en parallèle, et les charges (Li) sont reliées au circuit de blocage grâce à un circuit OU (Dc). 8. Circuit selon l'une quelconque des revendications précédentes, caractérisé en ce qu'il comprend également des moyens de circuit de récupération d'énergie (SW₃, Rc, Cc), commandés par l'unité (ECU) et adapté pour permettre de recycler vers l'alimentation (VB) une partie de l'énergie réactive stockée dans la charge (Ri), chaque fois qu'une charge (Li) est désactivée. 9. Circuit selon les revendications 7 et 8, caractérisé en ce que les moyens de circuit de récupération comprennent un interrupteur électronique (SW₃) supplémentaire, relié entre le circuit de blocage (Rc, Cc) et l'alimentation (VB) et commandé par l'unité électronique (ECU).