EP2445306A2 - Method for controlling the operation of an induction cooktop and induction cooktop using said method - Google Patents

Abstract

The method involves controlling one of inverter devices by a control unit and supplying alternating voltage to an induction cook top, where the cook top includes a power supply system producing rectified and filtered supply voltage (V2) from the voltage. Change of control (10) of the device is performed by a control unit when instantaneous value of the supply voltage of the device ranges between periodic minimum and 20 percent higher than the periodic minimum, where the change of control designates starting, modification of frequency or duty cycle or stop of control signals of the device. An independent claim is also included for an induction cook top comprising an inverter device.

Description

The present invention relates to a control method in operation of an induction hob.

It also relates to an induction hob, comprising at least one inductor in a hob, said induction hob being adapted to implement the control method in operation according to the invention.

More particularly, the invention relates to the modification of the inverter device control supplying an inductor in an induction hob.

An induction hob is powered by an alternating voltage which is generally that of the electrical distribution network and comprises at least one cooking zone in the hob. Each cooking zone is composed of at least one inductor.

Conventionally, each inductor is powered by an inverter device.

The inverter devices are themselves powered by a rectified and filtered voltage obtained from the AC voltage supplying the induction hob.

An inverter device notably uses a semiconductor power switch, for example of the power transistor type.

Each inverter device can be made according to different topologies. Regarding the induction hobs, it is often either a half-bridge topology, implementing two power switches, or a quasi-resonant topology, implementing a single power switch . It may also be, without this list being exhaustive, a complete bridge topology using four power switches.

It is necessary to control each inductor of each cooking zone according to a desired power demanded by the user for heating the container disposed on the cooking zone.

In order to get as close as possible to the desired setpoint power demanded by the user, the control of the inverter device is periodically modified to regulate the power restored in the container.

For this, it is conventional to vary the switching frequency of the inverter device (or switching frequency of the control signal of the power switches).

This power variation method is based on the agreement of the resonant system constituted by the inductor, the container and a resonance capacitor, the restored power decreasing when the switching frequency moves away from the resonance frequency of the resonant system.

In inverter devices made with a half-bridge topology, it is also possible to modulate the power delivered to each container by varying the duty cycle of the power switch control signal while maintaining the frequency of the control signal of the power switches. power switches.

In addition to these methods of varying the power delivered in the container, and always to get as close as possible to the desired power demanded by the user, the modification of the control of the inverter device may consist of stopping periodically and for a determined duration the control signal of the power switch (s) of the inverter device.

Thus, throughout the document, the term modification of the control of the inverter means indifferently the start, the change of the frequency or the duty cycle, or the stopping of the control signal (s) of the inverter device.

We already know the document EP 1 951 003 A1 which describes a method for controlling the power delivered to a pair of induction heaters / coils belonging to a domestic hob. This method allows the simultaneous operation of two induction heaters by avoiding the occurrence of beat noise while providing a regular distribution of the predefined power levels. The document provides for an order period during which the average power delivered by the induction heaters corresponds to the preselected power levels. This control period is divided into fractions of time. During the first fraction of time, the two induction heaters are controlled simultaneously, their respective converters operating at the same first frequency. During the second fraction of time, one of the two induction heaters is stopped and the other heating element is controlled, its converter operating at a second frequency. The selected control period can be a multiple of the half-period of the mains supply voltage and the smallest fraction of managed time can be synchronized with the mains supply voltage and be equal to the duration of one half period of the mains supply voltage.

The document is also known EP 0 986 287 A2 which relates to a two-output converter consisting of a three-phase H-bridge comprising power semiconductors which are controlled by a control circuit for regulating the power supplied to the outputs and which also comprises two switches whose activation modifies the topology to supply one of the charges or both charges simultaneously. The control circuit of the invention comprises a zero voltage detector of the mains voltage so that any change in the pulse width of the power semiconductors is synchronized with the zero crossing of the voltage, so as to preserve the voltage. operation of power semiconductors.

Conventionally, the control means of the induction hob creates a square signal synchronized with the zero crossings of the AC voltage supplying the induction hob. The periodic changes in the control of the inverter device are made at fixed times with respect to the periodic edges of this square signal.

However, the modification of the control of the inverter device at fixed times with respect to the edges corresponding to the zero crossings of the AC supply voltage of the induction hob can induce noise nuisance depending on the use of the table. induction cooking.

The present invention aims to solve the aforementioned drawback and to provide a control method in operation of an induction hob for changing the power delivered to each container disposed on the induction hob, whatever the topology of the inverter devices supplying each inductor, and optimized to avoid the appearance of noise during periodic changes in the controls of the inverter devices.

To this end, the present invention relates to a control method in operation of an induction hob comprising at least one inverter device, each inverter device supplying at least one inductor in a cooking plane of said hob to induction, said induction hob comprising at least one control means, each control means being adapted to control at least one of said inverter devices, said induction hob being powered by an alternating voltage and having at least one system power supply producing a rectified voltage and filtered from said AC voltage, each supply system feeding at least one of said inverter devices.

• modification de la commande dudit au moins un dispositif à onduleur par ledit au moins un moyen de commande lorsque la valeur instantanée de ladite tension redressée et filtrée d'alimentation dudit au moins un dispositif à onduleur est comprise entre le minima périodique et 20% de plus que ledit minima périodique ; ladite modification de la commande dudit au moins un dispositif à onduleur désignant le démarrage, la modification de la fréquence ou du rapport cyclique, ou l'arrêt du ou des signaux de commande dudit au moins un dispositif à onduleur.

According to the invention, the operating control method comprises at least the following step:

• modification of the control of said at least one inverter device by said at least one control means when the instantaneous value of said rectified and filtered supply voltage of said at least one inverter device is between the periodic minimum and 20% more that said periodic minimum; said modification of the control of said at least one inverter device designating the start, the modification of the frequency or the duty cycle, or the stopping of the control signal (s) of said at least one inverter device.

Thus, by making periodic changes in the control of the inverter device at the times when the rectified and filtered power supply voltage of the inverter device is minimal, it is possible to reduce or even eliminate the noise nuisance generated by the modifications of the inverter device. control of the inverter device outside the minima of the supply voltage of the inverter device.

The rectified and filtered voltage that supplies this type of inverter device is not continuous when the inverter device delivers current in its load constituted by an inductor.

The rectified and filtered supply voltage of the inverter device has periodic minima whose period is identical to the period of the AC voltage from which it is derived. The minimums of this rectified and filtered supply voltage of the inverter device are out of phase with the zero crossings of the AC voltage from which it is derived.

According to a practical feature of the invention, said at least one means for controlling said at least one inverter device receives a signal synchronized with the zero crossing of said alternating voltage. And said modification of the control of said at least one inverter device occurs with a predetermined delay with respect to said signal synchronized with the zero crossing of the AC voltage.

Thus, thanks to the predetermination during the design phase of the induction hob of the delay that exists between the signal synchronized with the zero crossing of said AC voltage and the minimum of the rectified voltage and filtered supply of said at least one an inverter device, it is possible for said at least one means for controlling said at least one inverter device to modify the control of said at least one inverter device at times corresponding to the minimums of the rectified and filtered supply voltage of said at least one inverter device.

According to a preferred feature of the invention, said at least one means for controlling said at least one inverter device comprises a device for measuring the instantaneous value of said rectified and filtered supply voltage of said at least one inverter device.

Said at least one means for controlling said at least one inverter device thus has precise knowledge, in real time, of the voltage level which supplies said at least one inverter device.

According to a practical feature of the invention, the minimum value taken by said rectified and filtered supply voltage of said at least one inverter device during a half-period or a period of the signal synchronized with the zero crossing alternating voltage is determined regularly.

By regularly determining the minimum value of said rectified and filtered supply voltage of said at least one inverter device, it is possible to improve the operating stability of the inverter devices.

The present invention also relates, according to a second aspect, to an induction hob comprising at least one inverter device, each inverter device supplying at least one inductor in a cooking surface of said induction hob, said hob to induction device comprising at least one control means, each control means being able to control at least one of said inverter devices, said induction hob being powered by an alternating voltage and comprising at least one supply system producing a rectified voltage and filtered from said AC voltage, each supply system feeding at least one of said inverter devices, said at least one control means being adapted to implement the operating control method according to the invention.

This induction hob has characteristics and advantages similar to those described above in relation to the operating control method according to the invention.

Other features and advantages of the invention will become apparent in the description below.

• la figure 1 est un schéma de principe d'un dispositif à onduleur réalisé selon une topologie demi-pont ;
• la figure 2 est un schéma de principe d'un dispositif à onduleur réalisé selon une topologie quasi-résonnante ;
• la figure 3 est un diagramme de principe représentant la tension d'alimentation de la table de cuisson à induction et un signal de synchronisation du dispositif à onduleur ;
• la figure 4 est un diagramme de principe représentant le même signal de synchronisation du dispositif à onduleur qu'à la figure 3 et la tension d'alimentation du dispositif à onduleur dans trois conditions de fonctionnement de la table de cuisson à induction ;
• la figure 5 représente les mêmes signaux et tensions que la figure 4 mais dans deux autres conditions de fonctionnement de la table de cuisson à induction ; et
• la figure 6 représente un signal de commande du dispositif à onduleur ainsi que les mêmes signaux et tensions que la figure 4 mais lors d'une variation de la commande du dispositif à onduleur.

In the accompanying drawings, given as non-limiting examples:

• the figure 1 is a block diagram of an inverter device made according to a half-bridge topology;
• the figure 2 is a schematic diagram of an inverter device made according to a quasi-resonant topology;
• the figure 3 is a principle diagram showing the supply voltage of the induction hob and a synchronization signal of the inverter device;
• the figure 4 is a principle diagram representing the same synchronization signal of the inverter device as at the figure 3 and the supply voltage of the inverter device in three operating conditions of the induction cooktop;
• the figure 5 represents the same signals and voltages as the figure 4 but in two other operating conditions of the induction hob; and
• the figure 6 represents a control signal of the inverter device as well as the same signals and voltages as the figure 4 but during a variation of the control of the inverter device.

An induction hob adapted to implement the control method in operation according to the invention will be described.

The cooking zones of an induction hob can be materialized by a screen printing of the hob vis-à-vis of which is an inductor 5. A hob commonly comprises one to four or even five cooking zones predefined in a hob usually extending to a width of about 30cm, 60cm or 90cm and a depth of about 51 cm.

By way of non-limiting example, the inductors 5 are generally of circular shape and the diameter of each inductor 5 is generally between 140 millimeters and 300 millimeters.

A container whose contents must be heated is placed on the hob at the screen of the cooking zone.

Some induction hobs do not have predefined cooking zones and therefore do not include screen printing predefining such or such cooking area. Each zone or cooking zone being determined on a case-by-case basis as a function of the position of a container placed opposite a subset of inductors 5. By way of non-limiting example, such a table Induction cooking usually helps to determine and to activate up to five cooking zones simultaneously to heat five containers on the hob.

As a non-limiting example, inductors 5 of these induction hobs are generally circular in shape and the diameter of each inductor 5 may be of the order of 80 millimeters. These induction hobs may for example comprise about 35 inductors 5.

Of course, the inductors 5 could be of different shape, they can for example be made by rectangular or triangular windings.

The induction hob comprises means for interfacing with the user and means for supplying and controlling at least one inductor 5.

The means for interfacing with the user comprise, on the one hand, display means and, on the other hand, selection means. They are located under the hob outside the cooking zones and so that the display means are visible to the user and the selection means are accessible to the user.

The display means make it possible, for example, to indicate the operating state of the induction hob, such as, for example, the heating power level of the cooking zones, any faults that have occurred, and the activated functions. They may be, by way of non-limiting examples, LED indicators, digital displays of the seven-segment type, liquid crystal displays.

The selection means may be, by way of non-limiting examples, knurls, keys, adjustment zones sensitive to the sliding of the finger. For reasons of ease of cleaning we often find sensitive keys on induction hobs.

The supply and control means for at least one inductor 5 essentially comprise at least one inverter device 7, a power supply system 6 and a means for controlling the at least one inverter device 7. These supply means and control of at least one inductor 5 include power electronics and also low voltage electronics, low power control.

The interface means with the user and the power supply and control means of at least one inductor 5 can be implanted on the same electronic card or, in the most frequent case, on separate electronic cards. The separation of the electronic cards makes it possible to optimize the design and the ergonomics by placing the interface means with the user at the most appropriate place for the user. The separation of the cards also makes it possible to reduce the overall bulk of the induction hob by placing the supply and control means of at least one inductor 5 in the spaces remaining free.

Depending on the number of cooking locations provided, an induction hob may use more than one electronic card comprising interface means with the user and / or more than one electronic card comprising the means for supply and control of at least one inductor 5.

We will describe first with reference to the figure 1 an exemplary embodiment of a means for supplying and controlling at least one inductor 5 by an inverter device 7 with topology half-bridge of an induction hob adapted to implement the method of operating control according to an embodiment of the invention.

This figure is a block diagram which, for the sake of simplification, does not represent all the components of an inverter device 7 but only those necessary for the explanation of the invention.

The induction hob is powered by the AC voltage V1, which in this example is single-phase.

The AC voltage V1 is received by the power supply system 6 which rectifies it by means of the four diodes 1, and then filters it to form the supply voltage V2 of the inverter device 7. The filtering capacitors of the power supply system 6 are not represented.

Filtering in this type of inverter device 7 is not intended to create a continuous supply bus. Its role is to limit the generation of electromagnetic disturbances to contain their level within the regulatory templates.

The inverter device 7 comprises the two power switches 2 and the capacitors 3, it supplies the inductor 5.

The two power switches 2 of this half-bridge topology are connected in series. This series connection is powered by the voltage V2 and the common point of this series connection supplies the inductor 5. The other end of the inductor 5 is connected to the common point of the two capacitors 3 connected in series. The series connection of these two capacitors 3 is powered by the voltage V2.

A not shown control means of the inverter device 7 generates the two control signals 4 of the inverter device 7 which drive the power switches 2. In this example, the power switches 2 are IGBT transistors (acronym for the English term). Insulated Gate Bipolar Transistor ', in French' bipolar transistor insulated gate ').

We will now describe with reference to the figure 2 an exemplary embodiment of a means for supplying and controlling at least one inductor 5 by an inverter device 7 with a quasi-resonant topology of an induction hob adapted to implement the method of operating control according to an embodiment of the invention.

The induction hob is powered by the AC voltage V1, which in this example is single-phase.

The feed system 6 is identical to that of the figure 1 .

The inverter device 7 comprises a power switch 2 and a capacitor 3, it supplies the inductor 5.

The capacitor 3 is connected in parallel with the inductor 5. This parallel assembly is itself connected in series with the power switch 2. The assembly is powered by the voltage V2.

The filtering of this voltage V2 serves the same purpose as in the case of mounting the figure 1 .

A not shown control means of the inverter device 7 generates the control signal 4 of the inverter device 7 which controls the power switch 2. In this example, the power switch 2 is an IGBT transistor.

Whether in the case of the figure 1 at half-bridge topology or in the case of the figure 2 with quasi-resonant topology, the supply voltage V1 of the induction hob usually comes from the electrical distribution network. In the embodiments of figures 1 and 2 , V1 is a single-phase nominal RMS voltage between 220V and 240V with a nominal frequency of 50Hz or 60Hz.

Of course, these values of voltages and frequencies are given as non-limiting examples and other values of voltages and / or frequencies may be used without departing from the scope of the invention.

On an induction hob having a plurality of cooking zones, each cooking zone having at least one inductor 5, it is possible to use a single power supply system 6 receiving the voltage V1, a single control means of the inverter 7 and several inverter devices 7.

In this case, the voltage V2 produced by the single power supply system 6 supplies each inverter device 7, and the single control means independently controls each inverter device 7.

Each inverter device 7 can supply a single inductor 5, or each inverter device 7 can supply several inductors 5 successively and periodically for example by means of a relay device.

The supply voltage of the induction hob can be three-phase with neutral conductor. It is then possible to use three power supply and control means each supplying at least one inductor 5. Each of the three power supply and control means being fed between one of the three phases and the neutral. Again, the power supply system 6 of each of the three power supply and control means of at least one inductor 5 can feed several inverter devices 7 which in turn can feed an inductor 5 or several inductors 5 successively and periodically.

For example, the induction hob can operate on a three-phase network with neutral conductor whose current limit is set at 16 amperes per phase, or even on a single-phase network whose current limit is fixed at 16 amperes or well 32 amperes.

Such a hob is thus capable of delivering a high total power, corresponding to the power delivered by the three phases, each delivering 16 amps at a voltage of 230 volts, or about 11040 watts.

Each inverter device 7 is controlled by a switching frequency of at least one signal 4, here adjustable, which makes it possible to modify the instantaneous power restored in a receptacle at least partially covering the inductor 5 thus fed.

In order to deliver the power corresponding to the setpoint that the user has selected for each cooking zone, it is necessary to periodically modify the control of the inverter devices 7.

The modification of the control of the inverter devices 7 may occur for example at each period of the supply voltage of the induction hob.

The modification of the control of the inverter devices 7 may consist, in addition to modifying the frequency of at least one signal 4, to periodically stop the operation of said at least one inverter device 7, for example by interrupting the generation of said at least one signal 4 of said at least one inverter device 7.

Stopping the operation of an inverter device 7 causes the stop of the operation of said at least one inductor 5 that it powers.

For example, the switching frequency of said at least one control signal 4 of said at least one inverter device 7 generally ranges from about 10 kHz to about 100 kHz. The minimum and maximum frequencies depend inter alia on the electrical characteristics of the power switches 2 and the inductors 5.

The figure 6 represents the signal V3 synchronized with the zero crossings of the AC supply voltage V1 of the hob to induction. It also represents on the curve f, the supply voltage V2 of the inverter device 7 at the moment of a modification of the control of the inverter device 7. The modification of the control of the inverter device 7 consists in this example in a modification of the frequency of the control signal 4 of the inverter device 7. Taking into account the frequencies (for example 50 Hz for the signal V3 and the alternating voltage V1 whose voltage V2 is output and 10 kHz at 100 kHz for the signal 4), the signal 4 has a period approximately 200 to 2000 times shorter than the period of the signal V3 and the AC voltage V1 whose voltage V2 is derived. In order to facilitate the understanding of the figures, the scale between the periods of the signals V3 and V2 on the one hand and of the signal 4 on the other hand has not been respected. The representation is chosen so that it clearly shows the moment of the change of frequency of the signal 4.

Each inductor 5 of the hob is independent and can operate at a switching frequency (or switching period) distinct from the switching frequencies of the other inductors 5.

An embodiment of the control method in operation of an induction hob, implemented by at least one control means integrated into the induction hob and making it possible in particular to generate the at least one induction hob, will now be described. a signal 4 for controlling the power switches 2 of said at least one inverter device 7.

Said at least one control means uses in particular physical measurement data, such as measurement data of the supply voltage V2 of said at least one inverter device 7 in order to adjust the control of said at least one inverter device 7 Said at least one control means also uses the signal V3 synchronized with the zero crossings of the AC supply voltage V1 of the induction hob.

Thus, as illustrated in figure 3 , the AC supply voltage V1 of the induction hob is used to generate a signal V3 synchronized with the periodic zero crossings of the voltage V1. The signal V3 is a square signal whose voltage level is adapted to the use by a processing unit of said at least one control means of said at least one inverter device 7. This processing unit can be for example a microcontroller. This signal V3 has a high logic level during a half-wave of the voltage V1 and a low logic level during the next half-wave of the voltage V1. The edges of this signal V3 are used to clock certain operations performed by the processing unit of the at least one control means of the at least one inverter device 7.

The invention relates to a control method in operation of an induction hob comprising at least one inverter device 7, each inverter device 7 supplying at least one inductor 5 in a cooking surface of said induction hob. said induction hob comprising at least one control means, each control means being adapted to control at least one of said inverter devices 7, said hob being powered by an alternating voltage V1 and having at least one supply system 6 producing a rectified and filtered voltage V2 from said alternating voltage V1, each supply system 6 supplying at least one of said inverter devices 7.

• modification 10 de la commande dudit au moins un dispositif à onduleur 7 par ledit au moins un moyen de commande lorsque la valeur instantanée de ladite tension redressée et filtrée V2 d'alimentation dudit au moins un dispositif à onduleur 7 est comprise entre le minima périodique et 20% de plus que ledit minima périodique.

Said operating control method comprises at least the following step:

• modification of the control of said at least one inverter device 7 by said at least one control means when the instantaneous value of said rectified and filtered supply voltage V2 of said at least one inverter device 7 is between the periodic minimum and 20% more than said periodic minimum.

The figure 4 represents the rectified voltage and filtered supply V2 of the inverter device 7 in three different operating conditions of said induction hob powered by an alternating voltage V1. In the three temporal representations of V2, the periodic minima of said rectified and filtered voltage V2 for supplying the inverter device 7 are observed.

The synchronization of the modification of the control of said inverter device 7 by a control means of the inverter device 7 with the periodic minima of said rectified and filtered voltage supply V2 of the inverter device 7 makes it possible to reduce or even eliminate the noise generated by the control changes of the inverter device 7.

Said at least one means for controlling said at least one inverter device 7 receives a signal V3 synchronized with the zero crossing of said alternating voltage V1. Said modification of the command of said at least one inverter device 7 occurs with a predetermined delay with respect to said signal V3 synchronized with the zero crossing of the alternating voltage V1.

The figure 4 represents temporally more than one period of the signal V3 synchronized with the periodic zero crossings of the voltage V1. The figure 4 also represents, in the same time axis, said voltage V2 in three different operating conditions of said induction hob. In the three representations of V2, the periodic minima of said rectified and filtered voltage supply V2 of the inverter device 7 are observed. The minima of V2 are spaced by the same duration as the time separating two successive fronts of the signal V3 synchronized with the periodic zero crossings of the voltage V1.

Thus, the modification of the control of said inverter device 7 by a control means of the inverter device 7 during the periodic minima of said rectified and filtered voltage supply V2 of the inverter device 7 can be carried out after each signal front V3 synchronized with the periodic zero crossings of the voltage V1.

In a preferred embodiment of the invention, the modification of the control of said inverter device 7 by a control means of the inverter device 7 occurs at most one edge out of two. That is, said modification occurs at most, either after each rising edge or after each falling edge of said signal V3, but not after each edge of said signal V3.

In the three operating conditions of the induction hob shown on the figure 4 by the curves a, b and c of the voltage V2, the minima of V2 occur with delays t1, t2 and t3 with respect to the edges of the signal V3 synchronized with the periodic zero crossings of the voltage V1.

Thus, during the design phase of said induction hob, identifying the complete series of delays t1, t2, t3 separating the edges of the signal V3 from the minima of the voltage V2 for the various operating conditions of the hob. induction, it is possible to store said complete series of delays t1, t2, t3 in the processing unit of the control means of the inverter device 7 and to program said processing unit so that it modifies the control of said inverter device 7 according to this complete set of times t1, t2, t3 stored.

In practice, for the inverter devices 7 sharing the same power supply system 6, said predetermined time of modification of the control of said at least one inverter device 7 depends on the number of inverter devices 7 in operation.

On an induction hob having a plurality of cooking zones, each cooking zone having at least one inductor 5, the control means can control several inverter devices 7 fed by the same power system.

The processing unit of said control means is aware of the number of inductors 5 in operation, and it has in memory the complete list of delays to be applied with respect to the synchronization signal V3 for the modification of the commands of the inverter devices 7 qu she controls. This list of said delays to be applied for the modification of the control of the inverter devices 7 is organized according to the number of inverter devices 7 in operation. By way of nonlimiting example, the delays t1, t2 and t3 can be t1 = 750ps, t2 = 500μs and t3 = 250μs.

t1 is used at startup of an inverter device 7 while no inverter device 7 is in operation.

t1 is also used when changing the control of an inverter device 7 when a single inverter device 7 is in operation.

t2 is used when changing the control of the inverter devices 7 when two inverter devices 7 are in operation.

t3 is used when changing the control of the inverter devices 7 when three inverter devices 7 are in operation.

The offset between the edges of the signal V3 synchronized with the periodic zero crossings of the voltage V1 and the minima of the rectified voltage and filtered supply V2 of the inverter device 7 is variable. It depends in particular on the number of inductors 5 in operation and the power supplied to each inductor 5. A power given by inductor 5, the delay to be applied between a front of the signal V3 and the modification 10 of the control of the inverter devices 7 is predetermined according to the number of operating inductors 5 which are powered by the same power supply system 6.

It is thus possible to reduce or even eliminate the noise generated by the modifications of the commands of the inverter device (s) 7 by making said modifications according to delays with respect to the synchronization signal V3 which correspond to minima of the voltage V2 of power supply of the inverter device (s) 7.

For inverter devices 7 sharing the same power supply system 6, said predetermined time for changing the control of said at least one inverter device 7 depends on the power delivered by said power supply system 6.

Advantageously, the processing unit of said control means determines the power delivered by said power supply system by measuring, for example, the current delivered by said power supply system and the voltage supplied by said power supply system and by calculating the power on said power supply system. the basis of measured values of current and voltage.

Depending on the calculated power value, the processing unit of said control means then selects said predetermined time for changing the control of said at least one inverter device 7 using for example a predetermined and stored value pair table. associating a power value with a predetermined delay value for modifying the control of said at least one inverter device 7.

The power delivered by said feed system can be determined by other means, for example and by way of non-limiting examples based on the power setpoint selected by the user for each of the cooking zones supplied by said power supply system or even based on the switching frequency of the inverter devices.

At a given power setting for the inverter devices 7 sharing the same power supply system 6, said predetermined time of change of control of said at least one inverter device 7 is a decreasing function of the number of inverter devices 7 in operation .

In addition, at a given power setting for the inverter devices 7 sharing the same power supply system 6, said predetermined time for changing the control of said at least one inverter device 7 is constant from three inverter devices. Operating.

Advantageously, the processing unit of said control means has in memory a list of three delays whose values are decreasing.

Consider a means for supplying and controlling at least one inductor 5 comprising a power supply system 6 and at least one inverter device 7. When only one inductor 5 is in operation, a single inverter device 7 is in operation. operation and the greater of the three stored delay values will be used by the processing unit to apply the modification of the control of the inverter device 7 in operation at the instant corresponding to the periodic minimum of the supply voltage V2 of said inverter device 7.

In the case of a means for supplying and controlling at least one inductor 5 comprising a power supply system 6 and several inverter devices 7, two of which are in operation to supply each at least one inductor 5, the second plus A large delay value will be used by the processing unit to apply the change in the commands of the inverter devices 7 in operation.

In the same configuration as in the preceding paragraph, when at least three inverter devices 7 are in operation, the third largest delay value will be used by the processing unit to apply the modification of the commands of inverter devices 7 to operation.

The offset between the edges of the signal V3 synchronized with the periodic zero crossings of the voltage V1 and the minima of the rectified voltage and filtered V2 supply of the inverter device 7 depends in particular on the number of inductors 5 in operation. At power given by inductor 5, the more inductors in operation, which are powered by inverter devices 7 sharing the same power system 6, the more said offset decreases.

Said offset is constant from a number of inverter devices 7 in operation. In the embodiment described, said offset is constant from three inverter devices 7 in operation.

According to the design of the induction hob, inter alia depending on the design of the inverter devices 7 and the inductors 5, the number of inverter devices 7 in operation from which said offset is constant can be different without departing from the scope of the invention. the invention.

The processing unit of said control means stores in memory a complete list of the delays to be applied with respect to the synchronization signal V3 for modifying the commands of the inverter devices 7 which it controls. Advantageously, the number of said delays to be applied for the modification of the control of the inverter devices 7 contained in this list may be equal to the number of inverter devices 7 in operation from which said offset is constant.

According to an advantageous improvement of the invention, said at least one means for controlling said at least one inverter device 7 comprises a device for measuring the instantaneous value of said rectified and filtered voltage supply V2 of said at least one inverter device. .

Thus, the processing unit of said control means of the inverter device 7 is able to know in real time the supply voltage level V2 of the inverter device 7.

Advantageously, the minimum value taken by said rectified and filtered supply voltage V2 of said at least one inverter device 7 during a half period or a period of the signal V3 synchronized with the zero crossing of the AC voltage. V1 is determined regularly.

The rectified and filtered supply voltage V2 of the inverter device 7 is represented on two curves d and e of the figure 5 in two different operating conditions of said induction hob powered by an alternating voltage V1.

In the two temporal representations d and e of V2, we observe that the periodic minima of said rectified and filtered supply voltage V2 of the inverter device 7 reach a value below a threshold S1 for the case of operation represented in d, and a value greater than the threshold S1 for the case of operation represented in e.

These variations of the minimum values of the supply voltage V2 of the inverter device 7 come from changes in the operating conditions of the induction hob. On the curve d, the power delivered by the induction hob is greater than the power delivered by the induction hob on the curve e.

According to an advantageous development of the invention, the minimum value of said rectified and filtered supply voltage V2 of said at least one inverter device 7 is determined during the half-period or the period of the signal V3 synchronized with the passage by zero of the voltage alternative V1 preceding the modification of the command of the at least one inverter device 7.

Thus, the change in control of said at least one inverter device occurs at a time when the minimum value of the rectified and filtered voltage V2 is known.

When said minimum value of the rectified voltage and filtered supply voltage V2 of at least two inverter devices 7 is lower than a predetermined threshold S1, the commands of the at least two inverter devices 7 are stopped before being restarted simultaneously by being modified or not.

In the case of a power supply and control means of several inductors 5 comprising a power supply system 6, a control means and several inverter devices 7 at least two of which are in operation to supply each at least one inductor 5 , the fact of stopping the commands of the inverter devices 7 and then restarting them at the same instant, has the effect of resynchronizing all the controls of the inverter devices 7 in operation which are powered by the same power supply system 6. This allows a better operating stability of the inverter devices 7 while avoiding the generation of noise when changing the controls.

Said predetermined threshold S1 for comparing with said minimum value of the rectified voltage and filtered supply V2 of said at least one inverter device 7 is between 30V and 40V, and is preferably 35V.

Thus, the resynchronization of the commands of the inverter devices 7 occurs without generating noise for the user.

In a second embodiment, the control means of said at least one inverter device 7 determines the instant at which it applies the modification of the control of said at least one inverter device 7 not on the basis of a predetermined delay. but using the information of the device for measuring the instantaneous value of the rectified and filtered voltage supply V2 of the at least one inverter device 7.

For this, the control means detects in real time the periodic minimum of the rectified voltage and filtered V2 supply of said at least one inverter device 7. When said periodic minimum is detected, the control means of said at least one device to Inverter 7 modifies the control of the at least one inverter device 7.

A variant of this embodiment provides that during a half-period, respectively a period, of the signal V3 synchronized with the zero crossing of the alternating voltage V1, the time which separates the beginning of said half-wave. period, respectively of said period, of the moment when the rectified voltage and filtered supply V2 of said at least one inverter device 7 takes its minimum value is determined and stored, and in that the modification of said control at least one inverter device 7 is applied at the end of said determined duration and stored after the start of a half-period, respectively of a following period of the signal V3 synchronized with the zero crossing of the alternating voltage V1.

Advantageously, the means for controlling said at least one inverter device 7 uses the device for measuring the instantaneous value of the rectified and filtered voltage supply V2 of said at least one inverter device 7 to take successive measurements of said voltage V2. so as to determine the instant at which the rectified and filtered voltage V2 takes its minimum value.

Thus, the time of application of the modification of the control of said at least one inverter device 7 is determined with respect to the current operating conditions of said induction hob.

In particular, by proceeding in this manner, the instant of application of the modification of the control of said at least one inverter device 7 varies according to the number of inverter devices 7 supplied by the same power supply system 6 at this time. moment and according to the power delivered by said power supply system 6.

The periodicity of these operations may be more or less frequent without departing from the scope of the invention.

They may be, for example, made at each period of the signal V3 synchronized with the zero crossing of the alternating voltage V1. In this case, the determination of the instant when the rectified voltage and filtered supply V2 of said at least one inverter device 7 takes its minimum value can be achieved during the first half-period of the signal V3 synchronized with the passage through zero of the AC voltage V1 and the modification of the control of said at least one inverter device 7 can be performed during the second half-period of the signal V3 synchronized with the zero crossing of the AC voltage V1.

In another example, they can be performed every two periods of the signal V3 synchronized with the zero crossing of the AC voltage V1. In this case, the determination of the moment when the rectified and filtered supply voltage V2 of said at least one inverter device 7 takes its minimum value can be achieved during a first period of the signal V3 synchronized with the zero crossing. of the AC voltage V1 and the modification of the control of said at least one inverter device 7 can be performed during the next period of the signal V3 synchronized with the zero crossing of the AC voltage V1.

These operations can also be performed less often and the duration between the beginning of the half-period, respectively of the period, of the signal V3 synchronized with the zero crossing of the AC voltage V1 and the time when the rectified voltage and filtered V2 supplying said at least one inverter device 7 its minimum value can for example be determined several times over several half-periods or over several periods of the signal V3 synchronized with the zero crossing of the alternating voltage V1 and be averaged. It is then the averaged value which is used to apply the modification of the control of said at least one inverter device 7 during a half-period or a following period of the signal V3 synchronized with the zero crossing of the voltage. alternative V1.

The repetition period of these operations depends in particular on the needs of the power control. The rehearsal period must be short enough to guarantee sufficiently powerful power control.

The present invention also relates, according to a second aspect, to an induction hob comprising at least one inverter device 7, each inverter device 7 supplying at least one inductor 5 in a hob of said induction hob, said hob induction cooker comprising at least one control means, each control means being adapted to control at least one of said inverter devices 7, said induction cooktop being powered by an alternating voltage V1 and having at least one control system. supply 6 producing a rectified and filtered voltage V2 from said alternating voltage V1, each supply system 6 supplying at least one of said inverter devices 7. Said at least one control means is adapted to implement the control method in operation according to the invention.

Of course, the present invention is not limited to the embodiments described above.

In particular, the present invention is not limited in the number of inductors in the hob of the induction hob.

It is the same for the number of heating zones predefined or can be defined case by case on the hob from the position of a container covering a subset of inductors 5.

Claims (13)

A method of operating an induction hob comprising at least one inverter device (7), each inverter device (7) supplying at least one inductor (5) in a hob of said hob to induction, said induction hob comprising at least one control means, each control means being adapted to control at least one of said inverter devices (7), said induction hob being powered by an alternating voltage (V1) and having at least one power system (6) producing a rectified and filtered voltage (V2) from said AC voltage (V1), each power system (6) supplying at least one of said inverter devices (7) characterized in that it comprises at least the following step: modification (10) of the control of said at least one inverter device (7) by said at least one control means when the instantaneous value of said rectified and filtered voltage (V2) supplying said at least one inverter device ( 7) is between the periodic minimum and 20% more than said periodic minimum; said modification of the control of said at least one inverter device designating the start, the modification of the frequency or the duty cycle, or the stopping of the control signal (s) of said at least one inverter device. Operating control method according to claim 1, characterized in that said at least one control means of said at least one inverter device (7) receives a signal (V3) synchronized with the zero crossing of said alternating voltage (V1 ), and in that said modification (10) of the control of said at least one inverter device (7) occurs with a predetermined delay with respect to said signal (V3) synchronized with the zero crossing of the alternating voltage (V1). Operating control method according to claim 2, characterized in that for the inverter devices (7) sharing the same power supply system (6), said predetermined time period of modification (10) of the control of said at least one inverter device (7) depends on the number of inverter devices (7) in operation. An operation control method according to claim 2 or claim 3, characterized in that for the inverter devices (7) sharing the same power supply system (6), said predetermined time of modification (10) of the control said at least one inverter device (7) depends on the power delivered by said power system (6). An operation control method according to one of claims 2 to 4, characterized in that at a given power setting for the inverter devices (7) sharing the same power supply system (6), said predetermined delay of modification ( 10) of the control of said at least one inverter device (7) is a decreasing function of the number of inverter devices (7) in operation. Operating control method according to one of Claims 2 to 5, characterized in that at a given power setpoint for the inverter devices (7) sharing the same power supply system (6), said predetermined delay of modification ( 10) of the control of said at least one inverter device (7) is constant from three inverter devices (7) in operation. Operating control method according to one of the preceding claims, characterized in that said at least one means for controlling said at least one inverter device (7) comprises a device for measuring the instantaneous value of said rectified and filtered voltage (V2) of said at least one inverter device (7). An operating control method according to claim 7, characterized in that the minimum value taken by said rectified and filtered voltage (V2) for supplying said at least one inverter device (7) during a half period or a period of the signal (V3) synchronized with the zero crossing of the AC voltage (V1) is determined regularly. An operation control method according to claim 7 or claim 8, characterized in that the minimum value of said rectified and filtered voltage (V2) for supplying said at least one inverter device (7) is determined in the course of the half-period or the period of the signal (V3) synchronized with the zero crossing of the AC voltage (V1) preceding the modification (10) of the control of the at least one inverter device (7). Operating control method according to one of claims 7 to 9, characterized in that during a half-period or a period of the signal (V3) synchronized with the zero-crossing of the AC voltage (V1), the time that separates the beginning of said half-period, respectively of said period, from the moment when the rectified voltage and filtered (V2) supply of said at least one inverter device (7) takes its value minimum is determined and stored, and in that the modification (10) of the control of said at least one inverter device (7) is applied at the end of said determined duration and stored after the start of a half-period, respectively of a next period of the signal (V3) synchronized with the zero crossing of the alternating voltage (V1). An operation control method according to one of claims 8 to 10, characterized in that when said minimum value of the rectified and filtered voltage (V2) for supplying at least two inverter devices (7) is less than a predetermined threshold (S1), the commands of said at least two inverter devices (7) are stopped before being restarted simultaneously while being modified or not. An operation control method according to claim 11, characterized in that said predetermined threshold (S1) for comparison with said minimum value of the rectified and filtered voltage (V2) for supplying said at least one inverter device (7) is between 30V and 40V, and is preferably 35V. Induction hob comprising at least one inverter device (7), each inverter device (7) supplying at least one inductor (5) in a hob of said induction hob, said table induction cooker comprising at least one control means, each control means being adapted to control at least one of said inverter devices (7), said induction cooker being powered by an alternating voltage (V1) and comprising at least a power supply system (6) producing a rectified and filtered voltage (V2) from said AC voltage (V1), each power supply system (6) supplying at least one of said inverter devices (7), characterized in that that said at least one control means is adapted to implement the operation control method according to any preceding claim.

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