EP3422815B1 - Induction cooking device and method for controlling same - Google Patents

Description

Field of application and state of the art

The invention relates to an induction cooking device with a plurality of row lines, a plurality of column lines, a plurality of resonant circuit elements with a respective first pole and a respective second pole, a plurality of grid diodes and an inverter. Each resonant circuit element is connected with its first pole to exactly one of the row lines. Each resonant circuit element is connected with its second pole to exactly one of the column lines. Each column line has a respective end column switch. The invention also relates to a method for controlling such an induction cooking device.

Induction cooking devices of this type are known from the prior art and are used in particular to achieve real surface cooking. The resonant circuit elements typically have induction heating coils with which pans standing on a hob can be heated. Exemplary designs are in EP 1 303 168 A1 as EP 2 380 400 B shown.

From the WO 97/19298 A1 an induction hob is known with a plurality of row lines and a plurality of column lines, a plurality of resonant circuit elements, which must be present, and at least one inverter. Each resonant circuit element has a first pole connected to exactly one of the row lines and a second pole connected to exactly one of the column lines. Each column line has an end column switch, and each row line has a first row line end and a second row line end, a respective row switch being arranged on one of them. The respective first poles of the connected resonant circuit elements are connected between the row line ends, and they are each connected to the inverter.

From the US 6,870,138 B2 a similar induction cooking device is known in which diodes are also arranged in the row lines.

From the EP 2 928 265 A1 yet another induction cooking device is known with a number of induction coils that can be controlled individually.

The most widespread electronic power circuits for inductive heating of an induction hob are the resonant (series) oscillating circuit and the quasi-resonant parallel oscillating circuit. The latter has the advantage that one switching element and one capacitor are required less than with the series resonant circuit.

It is desirable to control a large number of induction coils, in particular smaller induction coils, without relays with few switching elements.

In known cooktops, each individual coil is controlled by a semiconductor transistor in the case of the quasi-resonant design or by two semiconductor transistors, usually IGBTs, in the case of the series resonant circuit. This solution is very expensive due to the high number of semiconductors for many induction coils (for example 20 to 50). At least n semiconductors are required for n induction coils.

The control of resistance heating elements using the multiplex method is known from the prior art. An interconnection of inductors or induction coils by rows and columns makes it possible to save semiconductor switches and possibly capacitors. Of the The construction of a hob is also simplified because a pair of cables for high currents does not have to be routed from an inverter to each induction coil, but the cable is looped through.

An exemplary implementation of an induction cooking device according to the prior art is shown in FIG Fig. 1 shown. The induction coils of the induction heating device are controlled in series resonant circuits by means of half-bridge transistors. A respective resonant circuit has a respective induction coil coil L and a respective capacitance or capacitor C. In the example shown, six series resonant circuits are shown, which are arranged in a matrix of rows and columns. The half bridge consists of switches S _highside and S _lowside , which can be implemented in particular by means of IGBT transistors or by means of MOSFETs. It is used to generate a high-frequency alternating voltage in the range from 20 kHz to 150 kHz, as is customary for the electrical excitation of inductive heating by means of induction coils.

A pulsating DC voltage source rectified from the mains voltage is designated with U. It may also be a pure DC voltage that is generated by a PFC (Power Factor Correction) circuit. Cs is an intermediate circuit capacitor, which stabilizes the intermediate circuit voltage of the half bridges with resonant circuits. Each row (Sx1a-Sx4a) or column (Sy1-Sy4) has a switch (IGBT transistors or MOSFET transistors). In contrast to the inverter _switches (S _highside , S _lowside ) for generating the high frequency, the semiconductors for switching the rows and columns switch slowly and therefore do not have to be of high quality; alternatively, a low forward voltage Vce (sat) in IGBTs and / or a low forward resistance RDS (on) must be taken into account with MOSFETs.

A driver module is required for control of each transistor, also for the inverter. So-called "high-side" drivers such as pulse transformers (galvanic separation possible) or charge pumps (without galvanic separation) come into question, this being true for all _{row switches} and for the S _highside .

If a switch (Sx1a or Sx2a) of a row and a column (Sy1 or Sy2) is now closed, the oscillating circuit L11C11 or L22C22 is excited (see Fig. 2 ). However, at the same time there is also an undesired flow of current through all further resonant circuits of line 2 to the switch (Sy1 or Sy2). Such leakage currents are smaller than the desired excitation current of the actual induction coil L11 or L22, but they generate disruptive losses and electromagnetic fields at the inductances of all other resonant circuits in the matrix. An analytical calculation for the quantitative determination of these leakage currents is not trivial. However, this current flow can be shown and quantified for simulation. In Fig. 2 the time course of the currents through the induction coils is shown if the induction coils L11 or L22 etc. are to be electrically excited at the time windows T11 or T22. In the time window T11, the desired current flow for the induction coil L11 is shown thick, for the other induction coils L the disturbances are shown thin. At the time window T22, the desired current flow for the induction coil L22 is shown thick, the interference for the other induction coils L is shown thin again. This applies in the event that a pot is placed on the induction coils L11 and L22. Therefore, current flows are only effected in their time windows T11 and T22.

Task and solution

The object of the invention is to create an induction cooking device and a method for controlling such an induction cooking device, with which problems of the prior art can be avoided and which are optimized in particular with regard to interference or possible leakage currents.

This object is achieved by an induction cooking device with the features of claim 1 and by a method for controlling such an induction cooking device with the features of claim 14. Advantageous and preferred embodiments of the invention are the subject of the further claims and are explained in more detail below. Some of the features are mentioned only for the induction cooking device or only for the process. However, they should be able to apply independently and independently of one another both to the induction cooking device and to the method. The wording of the claims is made part of the content of the description by express reference.

The invention relates to an induction cooking device. This has a plurality of row lines and a plurality of column lines. It has a plurality of resonant circuit elements with a respective first pole and a respective second pole. It also has a plurality of grid diodes and an inverter. Each resonant circuit element is connected with its first pole to exactly one of the row lines. Each resonant circuit element is connected with its second pole to exactly one of the column lines. Each column line has a respective end column switch.

According to the invention, it is provided that each row line has a first row line end and a second row line end, between which the respective first poles of the connected resonant circuit elements are connected. The first and second row line ends are each connected to the inverter, a respective row switch being arranged at least at one of the row line ends. The respective first poles of the oscillating circuit elements are connected to a respective grid diode which is connected to the respective second row line end with the forward direction towards the second row line end, so that of the first poles connected to a row line at most one respective first pole is directly connected to the second row line end.

This embodiment avoids the disadvantage described at the beginning by a clever arrangement of the grid diodes. A direct series connection of a diode to the resonant circuit is not possible, because otherwise free oscillation of the series resonant circuit is prevented. However, the function of the resonant circuits is guaranteed by the design described here, in particular the separation by means of grid diodes. Unwanted currents through induction coils do not occur, as these are prevented by the diodes. At any point in time, a current flow takes place exclusively in the oscillating circuit elements that are to be electrically excited at a given point in time.

It should be understood that the term grid diodes is not a special type of diode, but that in principle all known designs of diodes can be used. Low-loss diodes or Schottky diodes are preferred. The designation of the grid diodes is chosen to make it clear that they are located within a grid of row lines and column lines. According to one embodiment, the resonant circuit elements are a respective capacitor and a respective coil connected in series. This can mean in particular that each resonant circuit element represents a resonant circuit per se.

According to one embodiment, the resonant circuit elements are a respective coil, a capacitor also being connected in each column line, which capacitor forms series resonant circuits with the respective connected coils. In this case, an oscillating circuit cannot typically already be formed by the respective oscillating circuit elements per se, but rather it arises only in connection with the respective capacitor. This can significantly reduce the number of capacitors required overall.

According to another embodiment, the resonant circuit elements are a respective coil, two capacitors furthermore being connected to each column line which form resonant circuits in series with the respective connected coils. The respective column line with the column switch is connected between the capacitors.

The column switches can in particular be bidirectionally conductive.

The coils are preferably induction coils. These can advantageously be used to heat cookware designed for this purpose and are then induction heating coils. The induction coils or other resonant circuit elements can preferably be identical to one another. This can mean in particular that all resonant circuit elements of the same type used in the induction cooking device are identical to one another.

The resonant circuit elements are preferably arranged in rows and columns, in particular in the form of a matrix. This leads to a clear design which enables, for example, a uniform distribution of oscillating circuit elements over a cooking surface to be heated.

According to one embodiment, a first row switch is arranged at each first row line end and a second row switch is arranged at each second row line end. The first row switch and the second row switch of each row line are preferably configured to be switched simultaneously. This enables an advantageous simultaneous connection of both row line ends, which ensures the operation of all resonant circuits even when the aforementioned grid diodes are present.

According to one embodiment, a row switch is arranged at each first row line end and a respective row diode is arranged with the forward direction away from the row switch at each second row line end. With such a design, the operation of the resonant circuits is also ensured when the grid diodes are used. The mentioned line diode is a typically cheaper component compared to line switches, which also does not need to be controlled.

According to one embodiment, of the poles connected to a row line, only that pole which is connected closest to the second row line end is directly connected to the second row line end. In this way, the already mentioned and desired suppression of leakage currents can be achieved in an advantageous manner.

The switches are preferably designed as self-locking N-channel MOSFETs. This has proven to be advantageous in practice. This can affect all switches or only some of the switches, for example row switches and / or column switches.

The column switches preferably have a respective freewheeling diode. Any parasitic currents can thus be diverted.

According to one embodiment of the invention, the line switches form an inverter. As a result, additional switching elements for forming the inverter can be saved. According to one embodiment, the grid diodes are connected between two first poles. They can thus advantageously exert the desired effect of suppressing undesired leakage currents.

According to a further embodiment, each first pole is connected to the first row line end by means of a respective grid diode and connected to the second row line end by means of a respective further grid diode. Each grid diode is connected with the forward direction towards the second row line end. Although this design is more complex, it offers the advantage of an even distribution of the voltages among the oscillating circuit elements.

The induction cooking device preferably also has a pot detection system which is designed to switch the row switches and column switches in such a way that only resonant circuit elements under a recognized pot are excited by the inverter. This enables an optimal use and a saving of energy, since only the required oscillating circuit elements are actually controlled.

The resonant circuit elements are preferably induction coils or induction heating coils or have such which are arranged in rows and columns next to one another and one behind the other. They are therefore distributed in a corresponding configuration on a hob, the columns advantageously meaning the arrangement one behind the other. The rows are the arrangement of induction coils side by side. The induction coils are preferably arranged in at least four rows and three columns, that is to say in a field with three induction coils one behind the other and four induction coils side by side. This has proven itself for typical applications, since sufficient variability with regard to the pot sizes and positions used is achieved without using an excessive number of components.

These and other features emerge from the claims and also from the description and the drawings, the individual features being implemented individually or in combination in the form of subcombinations in one embodiment of the invention and in other areas and being advantageous and protectable per se Can represent designs for which protection is claimed here. The subdivision of the application into individual sections and subheadings does not limit the general validity of the statements made under these.

Brief description of the exemplary embodiments

Fig. 1:

eine Induktionskochvorrichtung gemäß dem Stand der Technik,

Fig. 2:

Spulenströme der Induktionskochvorrichtung gemäß dem Stand der Technik,

Fig. 3:

ein Ausführungsbeispiel der Erfindung,

Fig. 4:

Spulenströme zum ersten Ausführungsbeispiel der Erfindung,

Fig. 5:

eine Induktionskochvorrichtung gemäß dem Stand der Technik

Fig. 6 bis 15:

ein zweites bis elftes Ausführungsbeispiel der Erfindung,

Fig. 16:

ein Zeitdiagramm,

Fig. 17:

ein weiteres Zeitdiagramm,

Fig. 18:

eine mögliche Belegung eines Kochfelds,

Fig. 19:

ein zugehöriges Zeitdiagramm,

Fig. 20:

eine weitere mögliche Belegung eines Kochfelds,

Fig. 21:

ein zugehöriges Zeitdiagramm,

Fig. 22:

eine nochmals weitere mögliche Belegung eines Kochfelds,

Fig. 23:

ein zugehöriges Zeitdiagramm und

Fig. 24:

ein Ablaufdiagramm.

Embodiments of the invention are shown schematically in the drawings and are explained in more detail below. In the drawings show:

Fig. 1:

an induction cooking device according to the prior art,

Fig. 2:

Coil currents of the induction cooking device according to the prior art,

Fig. 3:

an embodiment of the invention,

Fig. 4:

Coil currents for the first embodiment of the invention,

Fig. 5:

a prior art induction cooking device

Fig. 6 to 15:

a second to eleventh embodiment of the invention,

Fig. 16:

a timing diagram,

Fig. 17:

another timing diagram,

Fig. 18:

a possible occupancy of a hob,

Fig. 19:

an associated timing diagram,

Fig. 20:

another possible occupancy of a hob,

Fig. 21:

an associated timing diagram,

Fig. 22:

another possible assignment of a hob,

Fig. 23:

an associated timing diagram and

Fig. 24:

a flow chart.

Detailed description of the exemplary embodiments

The Fig. 1 shows an induction cooking device according to the prior art, which has already been described in the introduction to this application. The Fig. 2 FIG. 13 shows currents through the induction coils of the induction cooking device of FIG Fig. 1 , which have already been described.

Fig. 3 shows an induction cooking device according to a first embodiment of the invention, which is in particular an induction hob. Six resonant circuit elements are shown, each of which is formed from an induction coil L and a capacitor C each. In the present case, the induction coils L are induction heating coils. As shown, the resonant circuit elements are arranged in a matrix form, the induction coils L and the capacitors C each being indexed with two letters. The first letter indicates the row, while the second letter indicates the column.

In the induction cooker of Fig. 3 there are also two line switches Sx1a, Sx1b of the first line and two further line switches Sx2a, 2x2b of the second line. Between these there are respective row lines to which respective first poles of the resonant circuit elements are connected. Respective second poles, which are opposite the first poles, are, however, connected to column switches Sy1, Sy2 and Sy3, with each column switch Sy1, Sy2, Sy3 belonging to a respective column of the matrix. The column switches Sy1, Sy2, Sy3 are connected to ground on opposite sides.

The respective row switches Sx1a, Sx1b, Sx2a, Sx2b are connected to an inverter, the output of which is labeled RF-Supply. The inverter is formed by two inverter _switches S _highside , S _lowside . A capacitor Cs and a voltage source U are connected upstream of these.

In the lines between the line switches Sx1a, Sx1b, Sx2a, Sx2b, respective grid diodes D11, D12, D21, D22 are connected. Two of these grid diodes are connected per line. This leads to the fact that only the resonant circuit elements lying furthest to the right in the matrix are directly connected to the respective row switches Sx1b, Sx2b on the right. The forward direction points to the second row switch Sx1b, Sx2b.

The grid diodes D11, D12, D21, D22 ensure that no undesired currents occur through induction coils, since these are prevented by the grid diodes D11, D12, D21, D22. This is in Fig. 4 illustrated who the Fig. 2 resembles. At any point in time, a current flow takes place exclusively in the induction coils, which at this point in time (T11 or T22 in Fig. 4 ) should be electrically excited. Fig. 4 shows the respective coil currents through the induction coils L. A pot stands on the coils L11 and L22.

In the Fig. 3 The illustrated embodiment with a 2x3 matrix can also be expanded, for example to a 4x4 matrix. It shows Fig. 5 an embodiment according to the prior art, whereas Fig. 6 shows an embodiment according to the invention, so with grid diodes D11, ..., D43.

Fig. 7 shows an exemplary embodiment in which the respective second row switches, that is to say on the right, are replaced by diodes SDx1, SDx2, SDx3, SDx4. The advantage of such an embodiment is that an additional switch per line is saved. The number N of semiconductor switches is significantly reduced to N = rows + columns instead of the previous N = 2 x rows + columns. Instead of replacing the respective second line switches, a corresponding replacement of the first or left-hand line switches with respective diodes would also be possible.

Fig. 8 shows an embodiment in which in comparison to in Fig. 7 illustrated embodiment, all semiconductor switches can be realized by N-channel MOSFETs self-locking. It should be noted that the column switching elements, in contrast to the row switches, require a freewheeling diode. However, this does not mean that the line switches cannot or may not have a freewheeling diode.

Fig. 9 shows an embodiment which, compared to in Fig. 8 illustrated embodiment instead of MOSFETs N-channel IGBTs used in a self-locking manner. This is advantageous because when the gate is not activated (for example, if there is a fault in the power supply to the controller), no current can flow, even if voltage is present on the semiconductor. In addition, N-channel semiconductors have a lower RDS (on) for MOSFETs and Vce (sat) for IGBTs, which is why they are more efficient than P-channel semiconductors.

Fig. 10 shows an embodiment of the invention in which only one resonant circuit capacitor C1, C2, C3, C4 is provided per column. The resonant circuit elements are only formed by a respective induction coil L. Due to the line-by-line and time-shifted control, the induction coils L can share the resonant circuit capacitor C in each column. In this case, the semiconductor switches Sy1-Sy4 are advantageously bi-directionally conductive so that the electrical current can flow back from the capacitor C to the induction coil L during an oscillation period. This is the case with MOSFETs or IGBTs with free-wheeling diodes.

Fig. 11 shows an embodiment in which the respective column capacitor is designed as a double capacitor (C1a, b-C4a, b) for highside and lowside, as it is usually implemented in a series resonant circuit with half-bridge control for inductive heating. It is advantageous here that Cx / 2 = Cxa = Cxb.

Fig. 12 shows an embodiment in which the semiconductors for switching the rows are designed as fast inverter switches. As a result of this measure, the main inverter (S (high side), S (low side)) of the previous exemplary embodiments can be dispensed with. Each switch S1xa-S4xa or S1xb-S4xb can advantageously have a diode Dx1a-Dx4a or Dx1b-Dx4b (analogous to the freewheeling diode of the IGBT), which is connected anti-parallel to the current flow, in order to counter-voltage generated by the inductance of the induction coil during the dead time in the switching process prevent.

Fig. 13 FIG. 4 shows an embodiment which, in comparison to the embodiment of FIG Fig. 12 is modified so that only a respective column capacitor C1, ..., C4 is used.

Fig. 14 FIG. 4 shows an embodiment which, in comparison to the embodiment of FIG Fig. 12 it is modified so that the respective column capacitors are designed in two parts.

With regard to the corresponding features with which the exemplary embodiments of Fig. 13 and 14th of the embodiment of Fig. 12 differ, refer to the descriptions above Fig. 10 and 11 referenced.

Fig. 15 shows an embodiment which counteracts the disadvantage that in previous embodiments the number of diodes which are connected in series increases with the number of columns. As a result, the loss increases with each additional column due to the Voltage drop across the diode lines. In addition, as the voltage is reduced, the transmittable power of the induction coils is also reduced. Since the current flow for column 4 flows through more diodes than for example to column 2, the voltage and thus the transmittable power at the induction coils in column 4 is lower than at the induction coils in column 2.

To avoid this, the in Fig. 15 illustrated embodiment, each induction coil L with two diodes D each connected directly to the respective row switch Sx1-4a. The disadvantage here is the almost doubling of the number of diodes compared to the exemplary embodiments described above.

Fig. 16 shows a timing diagram for a control variant of a hob with a 4x4 arrangement of induction coils L, in which each induction coil Lxy is excited in its assigned time window Txy, where x is the line number and y is the column number of the respective induction coil L. The number of time windows corresponds to the number of induction coils. If an induction coil L is not to be switched on, the corresponding switch in the column remains switched off in the corresponding time window Txy. If, for example, the induction coil L22 is not to be excited, the switch Sy2 blocks in the time window T22. This is shown in time window T22 for Sy2 by a dotted line. The disadvantage here is that each induction coil requires a discrete time window and thus the instantaneous power must be N times the nominal voltage, where N represents the number of induction coils L.

Fig. 17 shows a timing diagram for the control of induction coils L, this control not taking place at fixed time windows. The control can also take place line-by-line or column-wise, as is customary when controlling displays, for example, in time-division multiplexing. Fig. 17 shows an example of the time course of a line-by-line control of a hob with a 4x4 arrangement of induction coils. In a time window Txy for each line 1 to 4, the corresponding line switch Sx1a-b becomes conductive. The corresponding switches in the column of induction coils to be excited electrically in this column are then also switched on. Line 1 is drawn in thin lines, line 2 is thinly dashed, line 3 is drawn in thick and line 4 is thickly dashed.

In the worst case with N columns (in the example N = 4), the power of the induction coil should be N times the nominal power.

A corresponding algorithm can decide, as a function of the pot position, whether line-by-line or column-wise activation is more favorable for the corresponding constellation of induction coils L to be switched on.

The activation of induction coils can take place in pulse packets if a flicker standard is observed.

In practice it has been shown that the nominal power can be less than N times the nominal power, since not all lines are or have to be in operation or some lines have the same pattern, which leads to the simplification of the control timing. This is explained using three examples, which are included in the Figs. 18-23 are shown.

Fig. 18 shows a 4x4 hob in matrix control with rows R1-4 and columns C1-4. A pot 1 is set up above the induction coils L21 and L22, and a pot 2 is set up above the induction coils L33 and L34. These are shown with 1 and 2. This means that lines R1 and R4 are not required.

The timing out Fig. 17 can thus be considerably simplified, namely to that which is described in Fig. 19 is shown. Lines R2 and R3 are excited twice per time period. The maximum power of each induction coil L only has to be twice the nominal power. Line 1 is again drawn with a thin line, line 2 with a thin dashed line, line 3 with a thick line and line 4 with a thick line.

When running Fig. 20 two cooking vessels 1 and 2 are set up and each cover four induction coils L. It should be noted that the activation pattern of line R1 corresponds to that of line R2. Thus the control of the line switch for R1 can take place simultaneously with that of the line switch for R2. The same applies to R3 and R4.

That timing is in Fig. 21 shown. Here too, due to the simplification of the timing, the required maximum power of each induction coil is twice the nominal power. Line 1 is again drawn with a thin line, line 2 with a thin dashed line, line 3 with a thick line and line 4 with a thick line.

If the control of two rows or columns is carried out as described and this type of control with the execution of Fig. 14 combined, it can be advantageous to control different columns or rows with the same frequency and in phase perform in order to avoid interference between the individual induction coils L. Activation that is not in phase or not in frequency can lead both to unwanted induction currents in the induction coils L and to interference noises resulting therefrom.

When running Fig. 22 there is only one pot 1 with the hob, so that a time multiplex of the control can be completely dispensed with. Lines 1 and 4 are not covered and therefore not activated. Control of the columns for rows 2 and 3 is identical. Time division multiplexing can thus be dispensed with. The switches Sx2a / b and Sx3a / b can be permanently closed. The same applies to switches Sy2 and Sy3. Corresponding timing is in Fig. 23 shown. Line 1 is again drawn with a thin line, line 2 with a thin dashed line, line 3 with a thick line and line 4 with a thick line.

• Ermittlung der durch Töpfe auf der Induktionskochvorrichtung überdeckten Induktionsspulen,
• Zuordnung der Induktionsspulen zu den jeweiligen Töpfen,
• Zuordnung der Induktionsspulen zu den jeweiligen Zeilen,
• Ermittlung nicht angesteuerter Zeilen für das Timing, da diese Zeilen nicht betrieben werden sollen,
• Ermittlung der Zeilen mit gleicher Spaltenansteuerung, da diese Zeilen im gleichen Zeitfenster betrieben werden können,
• Ermittlung der Zeilen, die durch Hinzufügen oder Weglassen einer Induktionsspule zeitgleich mit anderen Zeilen angesteuert werden können, da auch diese Zeilen im gleichen Zeitfenster betrieben werden können,
• Ermittlung der Pulspakete für den entsprechenden Zustand und die entsprechende Kochstufe für jeden Topf.

For surface hobs with many small induction coils, it is possible to have rows in which only a single induction coil is covered by a pot, the pot being so large that several induction coils are covered, to leave this row with this induction coil completely switched off in order to improve the timing to simplify. This applies provided that the induction coils are small enough and the power loss can be compensated for by the remaining induction coils. Furthermore, the inhomogeneity that occurs in the heating of the pot should be within the tolerable range. An induction coil in a row that is not covered or not sufficiently covered can also be energized in order to obtain the same control pattern row by row and thus also to simplify the timing. This means that a slight increase in the stray field is to be expected, which, however, is slight with small coils. Finding a suitable control timing is made possible by an algorithm according to a method according to the invention, which is shown in Fig. 24 is shown. Such an algorithm or a method according to the invention generally include the following steps:

• Determination of the induction coils covered by the pots on the induction cooking device,
• Assignment of the induction coils to the respective pots,
• Assignment of the induction coils to the respective lines,
• Determination of not controlled lines for the timing, since these lines should not be operated,
• Determination of the rows with the same column control, since these rows can be operated in the same time window,
• Determination of the lines that can be controlled simultaneously with other lines by adding or omitting an induction coil, since these lines can also be operated in the same time window,
• Determination of the pulse packages for the corresponding status and the corresponding cooking level for each pot.

The entire calculation process can or will not only be carried out line by line, but can or will also be carried out column by column. The cheaper or less complex variant is then carried out. In this context, more favorable is intended to mean that more columns can remain switched off or can be operated together, and thus the period of activation is shortened. The selection therefore depends on whether more rows or more columns remain switched off or can be operated together.

When looking at the power distribution, it is noticeable that hobs are usually operated with two phases. As a result, for example, the total nominal power consumption is 7.2 kW. With a power of 400 W per induction coil, this means that a maximum of 7.2 kW / 400 = 18 induction coils can be operated simultaneously during a time window. This consideration also shows that only 18 induction coils have to be taken into account when controlling in time division multiplex. This applies to this embodiment and with maximum power of all induction coils. Correspondingly more induction coils can be operated at lower power.

Claims (15)

1. Induction cooking device, comprising

   - a plurality of row lines,

   - a plurality of column lines,

   - a plurality of resonant circuit elements (L, C) each including a respective first pole and a respective second pole, and

   - an inverter (S_highside, S_lowside),

   - wherein each resonant circuit element (L, C) is connected via its first pole to exactly one of the row lines,

   - wherein each resonant circuit element (L, C) is connected via its second pole to exactly one of the column lines,

   - wherein each column line includes a respective end-side column switch (Sy),

   - each row line includes a first row line end and a second row line end, between which ends the respective first poles of the connected resonant circuit elements (L, C) are connected,

   - the first and second row line ends each are connected to the inverter (S_highside, S_lowside), wherein at least on one of the row line ends a respective row switch (Sx) is disposed,

   characterized in that

   - a plurality of grid diodes (D) is provided,

   - respective first poles of the resonant circuit elements (L, C) are connected to a respective grid diode (D) which is connected via the respective second row line end with a conducting direction towards the second row line end,

   - such that of the first poles connected to one row line at most one respective first pole is directly connected to the second row line end.
2. Induction cooking device according to claim 1, characterized in that the resonant circuit elements (L, C) are a respective capacitor (C) and a respective induction coil (L) in series connection.
3. Induction cooking device according to claim 1, characterized in that the resonant circuit elements (L, C) are a respective induction coil (L), wherein preferably in each column line one capacitor (C) is circuited which forms series resonant circuits with the respective connected induction coils (L), wherein in particular the column switches (Sy) are bidirectionally conducting.
4. Induction cooking device according to claim 1, characterized in that

   - the resonant circuit elements (L, C) are a respective induction coil (L),

   - wherein further on each column line two capacitors (C) are circuited which form series resonant circuits with the respective connected induction coils (L),

   - wherein the respective column line is connected to the column switch (Sy) between the capacitors (C),

   wherein in particular the column switches (Sy) are bidirectionally conducting.
5. Induction cooking device according to any one of the preceding claims, characterized in that the resonant circuit elements (L, C) are arranged in rows and columns, in particular in the form of a matrix.
6. Induction cooking device according to any one of the preceding claims, characterized in that on each first row line end a first line switch (Sx1a, Sx2a) is disposed and on each second row line end a second line switch (Sx1b, Sx2b) is disposed, wherein preferably the first line switch (Sx) and the second line switch (Sx) of each row line are configured to be switched simultaneously.
7. Induction cooking device according to any of the claims 1 to 5, characterized in that on each first row line end a line switch (Sx) is disposed and on each second row line end a respective line diode (SDx) is disposed with a conducting direction away from the line switch (Sx).
8. Induction cooking device according to any one of the preceding claims, characterized in that of the poles connected to a row line only that pole which is connected closest to the second row line end is attached directly to the second row line end.
9. Induction cooking device according to any one of the preceding claims, characterized in that the column switches (Sy) include a respective free-wheeling diode and/or the line switches (Sx) form the inverter (S_highside, S_lowside).
10. Induction cooking device according to any one of the preceding claims, characterized in that the grid diodes (D) are each circuited between two first poles.
11. Induction cooking device according to any of the claims 1 to 9, characterized in that by means of a respective grid diode (D) each first pole is connected to the first row line end and by means of a respective further grid diode (D) is connected to the second row line end, wherein in particular each grid diode (D) is circuited with a conducting direction towards the second row line end.
12. Induction cooking device according to any one of the preceding claims, characterized in that the induction cooking device further has a pot detection which is configured to switch the line switches (Sx) and the column switches (Sy) such that only resonant circuit elements (L, C) located underneath a detected pot (Pan) are induced by the inverter (S).
13. Induction cooking device according to any one of the preceding claims, characterized in that the resonant circuit elements (L, C) are or include induction heating coils which are arranged in rows and columns side by side and one behind the other, preferably at least in four rows and three columns.
14. Method for controlling an induction cooking device according to any one of the preceding claims, characterized by the steps:

    - identifying the induction coils covered by pots,

    - assigning the induction coils to the respective pots,

    - assigning the induction coils to the respective rows or to the respective columns,

    - identifying not-activated rows or not-activated columns for timing purposes, since those lines or columns are not to be operated,

    - identifying the rows of similar column activation or the columns of similar row activation, since those lines or columns can be operated in the same time frame,

    - identifying the rows or columns which are activatable by adding or omitting an induction coil simultaneously with other rows or columns, wherein those rows or columns can be operated in the same time frame,

    - identifying pulse bundles for the corresponding condition and the corresponding cooking setting for each pot on the induction cooking device.
15. Method according to claim 14, characterized in that the variant of the row activation or column activation is performed, in which more rows or columns can remain switched-off or can be operated together, wherein preferably the period duration of the activation is reduced thereby.

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