ES2728849T3 - Procedure and device for feeding induction media - Google Patents

Abstract

Induction means feeding procedure, the induction means (I1, I2, I3) being associated with a cooking zone (F1, F2, F3, F4) and being fed to setpoint power values respectively by a feeding device of the inverter (20) comprising switching means (A, B) operating according to a working frequency (FT), in continuous mode when the setpoint power value is greater than or equal to a minimum instantaneous power, and in interrupted mode when the setpoint power value is lower than said minimum instantaneous power, said minimum instantaneous power corresponding to a maximum frequency of continuous operation (F2), the feeding procedure being characterized in that the switching means (A, B) are set to operation for a predefined duration (TX) at a starting frequency (Fd) greater than the maximum continuous operating frequency (F2), at the beginning of a period or program (Tprog).

Description

DESCRIPTION

Procedure and device for feeding induction means.

The present invention relates to a method of feeding induction means.

It also refers to a feeding device adapted to implement the feeding procedure, as well as an induction cooking apparatus adapted to integrate such a device. The present invention relates more particularly to the feeding of the induction means of an induction cooking apparatus.

In such a cooking appliance, each cooking zone or focus is associated with induction means. The operation of each cooking zone is directed by a power element integrated in an inverter power supply device.

A feeding device is described in EP 2341 757 A1 which discloses the preamble of claim 1.

An inverter feeding device of this type is also described in WO 2007/042315 in which the induction means integrated in a resonant circuit are fed from an inverter feeding device comprising a switch, of the type of a voltage controlled transistor, known as IGBT (acronym for the English term "Insulated Gate Bipolar Transistor '), mounted in series with the resonant circuit.

An inverter power device of this type operates according to a switching frequency of the switch. By modifying the switching frequency or working frequency of the inverter feeding device, it is possible to adjust the instantaneous power supplied by the induction means to a cooking vessel arranged on a cooking zone.

The feeding device feeds the induction means from the rectified mains voltage by means of a rectification circuit.

It will be noted that the induction means form part, with the container arranged on the cooking zone, of a resonant circuit and that when the resonance frequency of this resonant circuit is equal to the working frequency of the feeding device, the current that circulates through the resonant circuit is maximum. Consequently, the instantaneous power generated by the induction means is maximized.

The switching frequency of the switch or the working frequency of the inverter power device is in an optimal operating range that is associated with the operation of the switch.

The optimum operating range is therefore defined between a minimum frequency corresponding to a maximum instantaneous power and a maximum frequency corresponding to a minimum instantaneous power. In general, the optimum frequency range is predetermined according to the parameters of the set formed by the induction means and the feeding device.

When a user of the cooking appliance requests an instantaneous power, or setpoint power, which is comprised between the minimum instantaneous power and the maximum instantaneous power, the feeding device operates in continuous mode over a predetermined period called the program period .

The program period corresponds to a period during which the power requested by the user or the setpoint power is restored.

This program period is predetermined in a manner known to the person skilled in the art, specifically to adapt to the EN-61000-3-3 standard on the power grid (Flicker standard) that sets a maximum number of power variations allowed in one minute .

In general, a program period comprises several periods of alternating electricity network.

When the induction means must supply a setpoint power lower than the instantaneous power At a minimum, the inverter power device operates in interrupted mode, that is, the power supply is discontinuous over time. Thus, the inverter power device operates at the maximum frequency of continuous operation (frequency substantially corresponding to the maximum frequency of the optimum frequency range) during an interval of the program period.

Thus, during this interval of the program period, the inverter power device operates according to a working frequency corresponding to the minimum instantaneous power, and during the remaining time of the program period, the power device of the inverter does not work.

Thus, for example, if the minimum instantaneous power has a value of 500 W and the instantaneous power to be supplied in the induction means is 100 W, this instantaneous power of 100 W is reconstituted by controlling the operation of the feeding device according to a maximum working frequency so that the induction means provide the minimum instantaneous power for an interval of 200 ms every second (in this example the program time of one second).

When the inverter power device operates in interrupted mode, at each start-up of the power device, that is, at the beginning of each program period, a high current is generated in the resonant circuit formed by the induction means and the container arranged on the cooking zone associated with the induction means.

The sudden appearance of this high current generates an audible noise in the container disposed on the cooking zone. This noise has a variable intensity depending specifically on the size, material and contents of the container, the parameters of the inductor (for example the size) and the value of the reconstituted power, and can be annoying for a user of an apparatus that It comprises an inverter feeding device of this type.

There are electrical circuits, for example resistive, that allow to reduce this periodic noise.

However, these electrical circuits are not satisfactory since they are quite expensive circuits, which occupy an important space in the electronic card (s) destined for the control of the induction means and that generate significant Joule losses.

The object of the present invention is to propose a method of controlling the induction means, which allows reducing, even eliminating, the noise generated in a container arranged on a cooking zone.

For this, the present invention relates to a method of feeding induction means, the induction means being associated with a cooking zone and being fed to setpoint power values respectively by an inverter feeding device comprising means of switching operating according to a working frequency, in continuous mode when the setpoint power value is greater than or equal to a minimum instantaneous power, and in interrupted mode when the setpoint power value is less than said minimum instantaneous power, said corresponding minimum instantaneous power at a maximum frequency of continuous operation.

According to the invention, the switching means are put into operation for a predefined duration at a starting frequency greater than the maximum continuous operating frequency, at the beginning of a program period.

Thus, as soon as the starting frequency is higher than the maximum continuous operating frequency, the current flowing in the vessel is lower than the current supplied when the switching means operate according to a working frequency lower than the maximum continuous operating frequency. .

Therefore, the operation of the inverter power device does not generate noise or at least generates a noise of low intensity and which is not annoying for a user of the cooking apparatus.

Advantageously, the switching means are put into operation for a predefined duration at a starting frequency greater than the maximum continuous operating frequency when operating in interrupted mode.

It will be noted that when the switching means operate in interrupted mode, they are put into operation on a regular basis.

Thus, it is particularly advantageous to operate the switching means at the starting frequency for a predefined duration when operating in interrupted mode.

According to one characteristic, the inverter power device is adapted to apply a mains voltage on the induction means, the predefined duration representing the time elapsed between a first instant from which the switching means are put into operation at a starting frequency and a second instant from which the switching means are put into operation at the working frequency substantially equal to the maximum frequency of continuous operation.

For example, in the second instant, the grid voltage is substantially zero.

Thus, when the control means are put into operation at the working frequency (which has a value substantially equal to the maximum frequency of continuous operation), the grid voltage is substantially zero.

Thanks to this characteristic, the possible generation of important currents in the inductors is avoided during the commissioning of the switching means at the working frequency.

Advantageously, the switching means are put into operation at the starting frequency when the mains voltage has its peak value.

Thus, when the switching means are put into operation at the first instant, the grid voltage has its peak value.

Consequently, the mains voltage evolves between its peak value and a substantially null value during the predetermined duration defined by the first instant (from which the switching means are put into operation at the starting frequency) and the second instant (from which the switching means are put into operation at the working frequency).

According to one characteristic, the switching means are put into operation at a starting frequency greater than the maximum continuous operating frequency at the beginning of each program period of the power supply device in which the instantaneous power supplied by the induction means is restored. .

The present invention relates, according to a second aspect, to a power device that feeds induction means at setpoint power and which comprises switching means that operate according to a working frequency in continuous mode when the power value of setpoint is greater than or equal to a minimum instantaneous power, and in interrupted mode when the setpoint power value is less than said minimum instantaneous power, said minimum instantaneous power corresponding to a maximum frequency of continuous operation.

According to the invention, the feeding device comprises control means configured to implement a feeding method according to the invention.

The present invention relates, according to a third aspect, to an induction cooking apparatus comprising a feeding device that feeds induction means and which is according to the invention and which implements a feeding method according to the invention.

The feeding device and the induction cooking apparatus have characteristics and advantages similar to those described above in relation to the feeding process.

The present invention finds its application in particular on an induction hob.

Other particularities and advantages of the invention will be further apparent from the following description. In the attached drawings, provided by way of non-limiting examples:

- Figure 1 is a schematic view of an induction cooking apparatus adapted to implement the feeding process according to the invention;

- Figure 2 is a diagram illustrating a feeding device according to an embodiment;

- Figure 3 is a more detailed diagram of the embodiment of the feeding device of Figure 2; - Figure 4 is a curve representing instantaneous power as a function of frequency;

- Figure 5 illustrates the instantaneous power as a function of time; Y

- Figure 6 represents curves that illustrate the evolution over time of certain signals when the feeding method according to the invention is implemented.

First, an induction cooking apparatus adapted to practice the present invention will be described with reference to FIG.

In this example, this cooking apparatus can be an induction hob 10 comprising at least one cooking focus associated with induction means.

In this example, the cooking plate 10 comprises four cooking foci F1, F2, F3, F4, each cooking focus being associated with the induction means comprising one or more induction coils.

This cooking plate 10 conventionally comprises an electrical supply 11, normally an alternating mains supply or mains supply.

By way of example, the cooking plate 10 is fed with 32 A, which can provide a maximum power of 7200 W to the cooking plate 10, ie a power of 3600 W per phase, in the case of a cooking plate 10 comprising two power phases.

It will be noted that the induction means associated with each cooking focus F1, F2, F3, F4 can be carried out in practice from one or more coils in which the electric current circulates, mounted on a power phase.

A control and power control card 12 makes it possible to support all the electronic and computer means necessary for the control of the cooking plate 10.

In practice, electrical connections 13 are provided between this control and power control card 12 and each cooking focus F1, F2, F3, F4.

Classically, in a cooking plate 10 of this type, the set of induction means and the control and control card 12 are placed under a flat cooking surface, for example made from a hob.

The cooking lights can also be identified by screen printing in front of the induction coils placed under the cooking surface.

Obviously, although an example of a cooking plate embodiment is illustrated in which four cooking zones which constitute the cooking foci F1, F2, F3, F4 in the cooking plane are predefined, the present invention also applies to a cooking plate that has a variable number or different forms of cooking focus, or even, that has a cooking plane without predefined cooking zones or spotlights, the latter being defined in each case by the position of the container in front of a subset of coils of induction arranged under the cooking plane.

Finally, the cooking plate 10 also comprises control and interface means 14 with the user that specifically allow the user to control in power and duration the operation of each focus F1, F2, F3, F4.

In particular, the user can, by means of the control and interface means 14, assign a setpoint power to each cooking focus covered by a vessel.

It is not necessary to describe here in more detail the structure of a cooking plate of this type and the assembly of the induction means.

The induction means are fed by an inverter supply device comprising switching means that operate according to a working frequency.

An exemplary embodiment of an inverter feeding device adapted to feed several cooking foci F1, F2, F3, F4 (three cooking foci F1, F2, F3 in the illustrated example) is illustrated in Figure 2.

The power device of the inverter 20 is adapted to apply the voltage of the alternating mains or mains voltage 30 on the induction means I1, I2, I3 corresponding respectively to the cooking foci F1, F2, F3.

The mains voltage or mains voltage has for example a value of 230 VRMS (peak value of 325 V) for the French electricity grid.

Obviously, the grid voltage may have different values, depending on the electricity grid of the country in which it is located.

The feeding device specifically comprises rectification means 21 suitable for rectifying the mains voltage 30 and synchronization means 22 that allow generating a periodic digital signal in which at least one between the rising front and the falling front is synchronized with a step through zero volts of the mains voltage 30.

A capacitor C ^bus is connected to the output of the rectifying means 21. The capacitor C ^bus is charged by the rectified mains voltage. The voltage V ^bus taken at the terminals of this capacitor C ^bus is substantially equal to the peak value of the rectified mains voltage while no power is supplied by an inductor, with the capacitor C ^bus charged at this peak value of the mains voltage rectified.

This value is, for example, 325 V for a power grid with an effective voltage value of 230 V.

In the feeding device 20, power bridges 23a, 23b, 23c are connected to inductors I1, I2, I3 respectively. The power bridges 23a, 23b, 23c can be built according to a semi-bridge or full-bridge architecture.

The feeding device 20 further comprises a treatment unit 24 suitable for controlling, in particular, the operation of the feeding device 20. The treatment unit is for example a microcontroller, a microprocessor or a programmable logic circuit.

Figure 3 represents a diagram of a power supply device 20 with a semi-bridge architecture. In this scheme, a power bridge 23a feeds a cooking focus (not shown in Figure 3).

It will be noted that the operation of a complete bridge architecture is similar, and will not be described here. The mains voltage 30, the rectification means 21, the ^bus capacitor C, the synchronization means 22, as well as the treatment unit 24 which have been described with reference to Figure 2, are shown in Figure 3. The bridge of power 23a comprises switching means.

In this example, the switching means are two power components A, B connected in series and operating as two switches.

For example, the power components are IGBT transistors (acronym for the English term "Insulated Gate Bipolar Transistors").

In the case of a complete bridge architecture, two other transistors connected to each other in series are mounted in parallel to the IGBT transistors A, B.

It will be noted that the two IGBT transistors A, B operate in alternation, that is, when one is through the other is blocked.

In this scheme, an inductance L represents both the inductance of the induction means and that of the vessel to be heated placed opposite.

Two resonance capacitors C1, C2 are mounted in parallel with the inductance L forming a resonant circuit therewith.

Two capacitors Ca, Cb for switching aid are mounted in parallel between the inductance L and the IGBT transistors A, B.

As described below, the IGBT switches A, B are controlled in operation according to a working frequency in order to adjust the instantaneous power supplied by the induction means to a vessel disposed over a cooking zone, to the power of setpoint requested by a user.

Figure 4 shows the instantaneous power that can be supplied by the induction means to a vessel arranged on a cooking zone, as a function of the switching frequency of the IGBT transistors. The person skilled in the art knows that the instantaneous power supplied by the induction means to the vessel is adjusted by modifying the switching frequency of the IGBT transistors.

The switching frequency of the IGBT transistor is comprised in an optimal operating range defined by a minimum frequency F ¹ and a maximum frequency F ² .

As can be seen in Figure 4, the minimum frequency F ¹ corresponds to the maximum instantaneous power and the maximum frequency F ² corresponds to the minimum instantaneous power.

The person skilled in the art knows the definition of this frequency range. The minimum frequency F ¹ (corresponding to the maximum instantaneous power) corresponds to the resonant frequency of the circuit resonant LC. The maximum frequency F ² is specifically defined taking into account operating restrictions of the IGBT transistor, for example to maintain satisfactory thermal behavior.

By way of example in absolute limitation, the optimum operating range is between 18 KHz and 50 KHz. Obviously, this interval can be between different values.

As described below, the power device can operate in continuous mode or in interrupted mode. These modes of operation will be described with reference to figure 5. This figure 5 represents the continuous instantaneous power supplied by the induction means on a vessel located over a cooking zone, as a function of time.

When the setpoint power requested by the user is between the minimum and maximum powers, the IGBT transistors A, B operate (each in turn) in continuous mode according to a working frequency. This working frequency is such that in a program period T ^prog (illustrated in Figure 5) the restored power is substantially equal to the setpoint power requested by the user.

When the setpoint power requested by the user is lower than the minimum power (corresponding to a maximum frequency of continuous operation), the IGBT transistors A, B operate in interrupted mode. In the interrupted mode, the IGBT transistors A, B operate according to the maximum frequency during an interval T ^disc of the program period T ^prog .

The duration of this interval T ^disc is limited so that the requested setpoint power is restored throughout the program period T ^prog . Since the person skilled in the art knows this determination, it will not be described in detail here.

Figure 6 shows curves that schematically illustrate the evolution over time of different signals during the implementation of the feeding method according to the invention.

The voltage V ^bus represents the voltage at the terminals of the C ^bus capacitor.

This voltage corresponds to the mains voltage V ^network when at least one power bridge 23a, 23b, 23c of the inverter power device is put into operation.

When none of the power jumpers 23a, 23b, 23c is put into operation, the voltage V ^bus is continuous and equal to the peak value of the network voltage V ^network . The frequency of the mains voltage in France is 50 Hz (therefore its period of 20 ms). Obviously, the frequency has different values depending on the country in which it is located.

The V ^com signal represents the command of the IGBT A, B switches. It will be noted that the V ^bus voltage is also represented superimposed on the V ^com signal.

Figure 6 also shows the power in the inductor in which the program period T ^prog can be displayed.

This program period T ^prog comprises several network periods, all of which are not represented here.

As an example in no way at all, the program period T ^prog has a value belonging to a range of values between 1 and 15 seconds.

It will be noted that the scales at which each of the signals are represented are different.

In the example depicted in Figure 6, the power device operates in interrupted mode.

Thus, the setpoint power requested by the user is lower than the minimum instantaneous power.

At the beginning of the program period T ^prog , the IGBT transistors A, B are put into operation at a starting frequency F ^d greater than the maximum continuous operating frequency F ² for a predefined duration T ^X.

By way of example in no way limiting, this working frequency has a value of 100 KHz.

Obviously, this starting frequency F ^d could have other values.

Thus, each time the IGBT transistors A, B are put into operation, that is, at each beginning of a program period T ^prog , are put into operation at a starting frequency F ^d greater than the maximum continuous operating frequency F ² .

Therefore, the circulating current I ^ind in the inductor is not too high and the noise generated in the vessel is reduced or even zero.

By way of example in no way limiting, the current I ^ind circulating in the inductor does not exceed 16.5 A for a frequency of 100 KHz, while for a frequency of 50 KHz (maximum frequency of continuous operation F ² ), current I ^ind reaches 26 A.

The predefined duration T ^x represents the time elapsed between a first instant t1 from which the switching means are put into operation and a second instant t2 from which the switching means are put into operation at the working frequency F ^t equal to the maximum frequency of continuous operation F ² .

In the described embodiment, the second instant t2 corresponds to an instant where the grid voltage is substantially zero.

Thus, at the time t2 where the IGBT transistors A, B begin to operate according to a working frequency F ^t substantially equal to the maximum continuous operating frequency F ² , the capacitor C ^bus is discharged.

In the described embodiment, the IGBT transistors A, B are put into operation when the mains voltage V ^bus has its maximum value or peak value.

Thus, if the IGBT transistors A, B are put into operation when the mains voltage has its peak value, the mains voltage V ^network and the voltage at the terminals of the C ^bus capacitor evolve in a similar way.

By way of example, in no way limited, the predefined duration T ^x has a value between 2 and 5 ms.

The IGBT transistors A, B operate at this starting frequency F ^d until the end of the interval T ^x .

At the end of this interval T ^x , that is at time t2, the IGBT transistors A, B each operate in turn at a working frequency F ^t substantially equal to the maximum continuous operating frequency F ² until the end of the interval T ^disc . At the end of this interval T ^disc , the IGBT transistors A, B do not work until the end of the program period T ^prog .

In one embodiment, the operation of the switching means A, B according to a starting frequency F ^d greater than the maximum continuous operating frequency F ² is implemented for a predetermined period T ^x located at the beginning of each program period T ^prog .

According to another embodiment, the operation of the switching means A, B according to a starting frequency F ^d greater than the maximum frequency of continuous operation F ² is implemented during a predetermined period T ^x located at the beginning of a T ^prog program period of every several program periods, for example located along a T ^prog program period of every two.

It will be noted that in this example (commissioning of the switching means A, B at the starting frequency F ^d for a predetermined period T ^x located over a program period T ^prog of every two), at least one of switching means A, B must be in operation at the beginning of the program period T ^prog which does not comprise any predetermined period T ^x at the beginning.

Claims (8)

i. Induction means feeding procedure, the induction means (I1, I2, I3) being associated with a cooking zone (F1, F2, F3, F4) and being fed to setpoint power values respectively by a feeding device of the inverter (20) comprising switching means (A, B) operating according to a working frequency (F ^T ), in continuous mode when the setpoint power value is greater than or equal to a minimum instantaneous power, and in mode interrupted when the setpoint power value is lower than said minimum instantaneous power, said minimum instantaneous power corresponding to a maximum frequency of continuous operation (F ² ), the feeding procedure being characterized in that the switching means (A, B) are they operate for a predefined duration (T ^X ) at a starting frequency (F ^d ) greater than the maximum continuous operating frequency (F ² ), at the beginning of a program period (T ^prog ). 2. Feeding method according to claim 1, characterized in that the switching means (A, B) are put into operation for a predefined duration (T ^X ) at a starting frequency (F ^d ) greater than the maximum operating frequency continuous (F ² ) when operating in interrupted mode. 3. Power supply method according to one of claims 1 or 2, characterized in that the inverter power supply device (20) is adapted to apply a mains voltage (V ^network ) on the induction means (I1, I2, I3) , the predefined duration (T ^x ) representing the time elapsed between a first instant (t1) after which the switching means (A, B) are put into operation at a starting frequency (F ^d ) and a second instant ( t2) from which the switching means (A, B) are put into operation at the working frequency (F ^T ) substantially equal to the maximum continuous operating frequency (F ² ). 4. Feeding method according to claim 3, characterized in that in the second instant (t2), the mains voltage (V ^network ) is substantially zero. 5. The feeding method according to one of claims 2 to 4, wherein the switching means (A, B) are put into operation at the starting frequency (F ^d ) when the mains voltage (V ^network ) is present its peak value 6. Feeding method according to one of the preceding claims, characterized in that the switching means (A, B) are operated at a starting frequency (F ^d ) higher than the maximum continuous operating frequency (F ² ) at beginning of each program period (T ^prog ) of the inverter power supply device (20) in which the instantaneous power supplied by the induction means (I1, I2, I3) is restored. 7. Induction means feeding device, the induction means (I1, I2, I3) being associated with a cooking zone, the feeding device feeding at induction power values the induction means (I1, I2, I3 ) and comprising switching means (A, B) that operate, according to a working frequency (F ^T ) in continuous mode when the setpoint power value is greater than or equal to a minimum instantaneous power, and in interrupted mode when the setpoint power value is lower than said minimum instantaneous power, said minimum instantaneous power corresponding to a maximum frequency of continuous operation (F ² ), characterized in that the supply device comprises control means configured to implement a feeding procedure, according to one of claims 1 to 6. 8. Induction cooking apparatus, characterized in that it comprises a feeding device that feeds induction means and which is according to claim 7 and that implements a feeding method according to one of claims 1 to 6.