Cooking hob having heating zones with different temperatures The present invention relates to a cooking hob for a domestic or an industrial appliance. Further, the present invention relates to a method for performing a cooking process on a cooking hob.

Usually, a cooking hob comprises several heating zones. The power and/or temperature of each heating zone are individually adjustable by the user and controllable by a control unit of the cooking hob.

The document WO 2015/015360 A1 discloses an induction cooktop having at least two heating elements which are arranged next to each other and are provided at least to heat positioned cookware and having at least one control unit. The control unit deter mines, in at least one operation mode, a plurality of virtual heating zones having different heat output density depending on a size of at least one positioned piece of cookware, wherein the virtual heating zones are formed by heating elements arranged adjacent to one another.

The document WO 2015/015361 A1 discloses an induction cooktop having at least two heating elements for heating positioned cookware and having one control unit which is provided in order to activate at least one first heating element allocated to a first position of a positioned piece of cookware. The control unit can, for the case of a change from the first position of the cookware to a second position of the cookware, to deactivate at least one first heating element allocated to the first posi tion of the cookware and to activate at least one second heating element which is allocated to the second position of the cookware and has differing heat output density than the first heating element.

It is an object of the present invention to provide an improved cooking hob, wherein the cooking temperature can be determined by the user in an easy way.

The object is achieved by the cooking hob according to claim 1. According to the present invention a cooking hob for a domestic or an industrial appliance is provided, wherein:

the cooking hob comprises at least one heating area, the heating area comprises at least a first and a second heating zone, wherein, in a first operation mode, the first and second heating zones are configured for being operated as heating zones separate from each other and, in a second operation mode, the first and second heating zones are con figured for being operated as one joint heating zone;

each of the first and second heating zone includes at least one heating element, wherein the first and second heating zones are operable or operated to heat a particular cookware item in such way that foodstuff disposed within the particu lar cookware is heated to (a) defined temperature ( s ) , when the particular cookware is placed above one of the first or second heating zones in the first operation mode, and in such way that foodstuff disposed within the particular cookware is heated to (a) defined temperature ( s ) , when the particular cookware is placed at least partially above both the first and second heating zones in the second operation mode;

wherein the cooking hob further comprises an automatic tem perature control for controlling the temperature of the par ticular cookware or for controlling the temperature of the foodstuff disposed within the particular cookware; and wherein the automatic temperature control is configured to control a first separate temperature related to the first heating zone and to control a second separate temperature related to the second heating zone in the case that the first and second heating zones are operated as separate heating zones in the first operation mode and wherein the automatic temperature control is configured to control a first common temperature related to the first and second heating zone in the case that first and second heating zone are operated as one joint heating zone in the second opera tion mode.

Such a cooking hob advantageously allows a user to use a so called chef mode in which the user defines specific heating zones to be temperature zones providing defined temperature for cookware placed upon. Thus, it is not longer necessary to adapt or reset the temperature of the heating zones, but only to move the cookware item from one temperature zone to another, e.g.

from a searing zone to a soft cooking zone to a holding zone. The automatic temperature control for the heating zones can be adapted with a high degree of freedom and enables comfort and exact and delay free achievement of the desired temperature of the foodstuff or the cookware item, respectively. In an advantageous embodiment according to the invention, the cooking hob enables the user to select, in particular for all heating zones provided on the cooking hob, if heating zones shall be operated in the first operation mode or in the second operation mode.

Thus, the user is enabled to define separate heating zones and joint heating zones flexibly by himself. User comfort is in creased . According to a further advantageous embodiment the cooking hob is configured or can be configured by user input

to operate at least a first and second heating zone in the first operation mode

or

to operate at least a first or a second heating zone in the first operation mode and one joint heating zone in the second operation mode at the same time

or

to operate at least two joint heating zones at the same time in the second operation mode.

Thus, the cooking hob can be operated with a high degree of freedom, in particular in such way that the user can combine heating zones as he or she desires and that the combination can be easily provided.

In a further advantageous embodiment of the invention, at least two, preferably at least three, separate and/or joint heating zones can be operated at set temperatures being different from each other, wherein each of the at least two, preferably at least three, heating zones is subject to the automatic tempera ture control, wherein each of the different set temperatures is controlled separately by the automatic temperature control.

Thus, a chef mode is advantageously enabled, wherein automatic temperature control is provided. Thus, the temperatures defined for the different chef mode temperature zones are controlled precisely on the basis of the real temperature of the cookware item or the food placed therein. The set temperatures can be reached quickly and without delay.

According to a further advantageous embodiment, the cooking hob enables the user to switch on or off the automatic temperature control for one or more specific separate or joint heating zones .

Thus, the automatic temperature control can be used when neces- sary, and can be switched off when it is not needed. Thus, en ergy can be saved.

According to a further advantageous embodiment, the cooking hob enables the user to couple specific separate and/or joint heat- ing zones, in particular in such way that the set temperatures of the coupled heating zones are jointly adjustable, preferably by means of only one user input or by means of only one input element, in particular wherein the difference between the set temperatures of adjacent heating zones or of jointly adjustable heating zones is between 10°C and 80°C, preferably between 20°C and 60°C, in particular between 30°C and 40°C.

Thus, it is possible for the user to define coupled or combined separate and/or joint heating zones which can be adjusted to- gether, e.g. such that the temperature of all coupled or com bined heating zones can be increased or decreased for 10°C.

In a further advantageous embodiment the automatic temperature control comprises at least one closed loop control for control- ling the set temperature of a first or second heating zone or of a joint heating zone, in particular in that the automatic tem perature control comprises separate closed loop controls for controlling separatly each of the first or second second heating zone or of a joint heating zone.

Thus, independent automatic temperature control can be achieved for each heating zone as defined by the user. Thus, efficient control of the set temperatures for each heating zone is pro vided . According to a further advantageous embodiment, the cooking hob comprises at least one temperature sensor for each heat ing zone, wherein preferably at least one temperature sensor is provided for each heating element.

It is particularly advantageous if each heating element is associated with at least one temperature sensor of if at least one temperature sensor is arranged adjacent to each heating element. The temperature sensor in this case are able to detect temperature related parameter values with re spect to cookware placed above the heating element.

Further advantageously, the automatic temperature control com- prises at least one temperature measurement unit, at least one control unit and at least one power unit, wherein the tempera ture measurement unit is configured to receive a signal or sig nals representative of temperature parameters detected by the temperature sensor (s) associated to a specific separate and/or joint heating zone and/or to transfer a signal or signals repre sentative of temperature parameters detected by the temperature sensor (s) associated to a specific separate and/or joint heating zone to the control unit, wherein the control unit outputs a control signal based on the temperature parameter detected by the temperature sensors for a specific separate and/or joint heating zone to the power unit such that the power unit controls the amount of energy supplied to the respective separate and/or joint heating zone in order to constantly maintain the tempera ture set for the respective separate and/or joint heating zone.

The temperature measurement unit and the control unit can be part of a central processing unit that calculates on the basis of the received temperature parameter information which output signal has to be output in order to achieve the set temperature on the specific heating zone.

Also advantageous it is that the cooking hob comprises at least three heating elements, in particular three induction coils, each heating element being associated with a temperature sensor, and one power unit, in particular comprising a power circuit board, wherein the power unit is operably, in particularly elec trically, coupled to each of the heating elements, wherein the power unit can drive each of the heating elements separately and can drive the heating elements in combination such that all heating elements associated to one joint heating zone are driven by the power unit in a way that the a temperature set for the joint heating zone can be constantly maintained.

Such an embodiment enables to use a "Chef-mode" in a even more advantageous form. The user is enabled to define specific heat ing zones to be temperature zones providing defined temperature for cookware placed upon. A searing zone, a soft cooking zone and a holding zone can be realized in positions adjacent to each other, wherein the automatic temperature control for the heating zones can be selectively used for the specific heating zones, wherein the desired temperature of the foodstuff or the cookware item can be controlled separately or jointly.

A further advantageous embodiment of the cooking hob comprises at least four heating elements, in particular four induction coils, and at least two power units, wherein each heating ele ment being associated with a temperature sensor, and one power unit, in particular wherein each power unit comprises a power circuit board, wherein the power units are operably, in particu lar electrically, coupled to heating elements that are exclu sively associated to exact one power unit, wherein the power units can drive their associated heating elements separately and can drive their associated heating elements in combination such that those heating elements that are associated to one joint heating zone are driven by their associated power unit in a way that the a temperature set for the joint heating zone can be constantly maintained.

Driving a number of, e.g. four, coils with two different power unit or power ciruit boards allows a more precise adaption of the power supplied to the respective coils, e.g. a more precise adaption of induction frequency or current to the cookware placed above the coils. Maintenance of a constant temperature of the cookware item or the foodstuff placed within the cookware item can be achieved precisely. Additionally, the cooking hob may comprise at least one memory for storing an adjustment of temperatures on the heating zones, wherein preferably the memory is adapted to store a fine adjust ment of the temperatures on the heating zones or related to the heating zones.

Moreover, the memory may be adapted to store the adjustment or fine adjustment, respectively, of temperatures on the heating zones or of temperatures related to the heating zones for at least one individual cookware item.

For example, the cooking hob may be an induction cooking hob, wherein the heating elements are induction coils.

According to another example, the cooking hob may be a radiant cooking hob, wherein the heating elements are radiant heating elements . Further, the cooking hob may be a gas cooking hob, wherein the heating elements are gas burner assemblies.

Moreover, the cooking hob may be a combination of an induction cooking hob, a radiant cooking hob and/or a gas cooking hob.

Preferably, the cooking hob comprises at least one glass ceramic panel covering the heating area. Further, the cooking hob may comprise:

at least one heating area,

the heating area is subdivided or divisible into at least two adjacent heating zones,

each heating zone includes at least one heating element, - the temperature of each heating zone is separately adjusted or adjustable by the user or predefined by the producer, and a cookware item is placeable on one heating zone or on more adjacent heating zones. It is possible that the cooking temperature depends on the posi tion of the cookware item on the heating area, wherein said heating area is subdivided or divisible into adjacent heating zones with different temperatures. The cooking temperature may be the temperature inside the cookware item. If the cookware item is arranged above one heating zone, then the cooking tem perature may correspond with the temperature of said heating zone. If the cookware item is arranged above two adjacent heat ing zones, then the cooking temperature may correspond with an intermediate temperature of the temperatures of said adjacent heating zones. The user may be enabled to change the cooking temperature by changing the position of the cookware item. It is not necessary to change the adjustment of the temperature and/or power of the heating zone. Before the cooking process, the user is able to define the temperature of each heating zone or the temperature of each heating zone is predefined by the producer. In a special case, the heating zones are individually activata- ble . Moreover, the heating zones may be defined by the user before the cooking process, wherein the temperatures of a plurality of heating elements of the heating area on the cooking hob may be separately adjusted by the user. Alternatively, the temperatures of the heating zones may be predefined by the producer. For ex- ample, the heating elements are arranged as a matrix on the heating area of the cooking hob. In this case, adjusted heating elements having the same temperature form the heating zone.

For example, the cooking hob comprises at least one pot detec- tion device for recognising the heating zone or heating zones, on which the cookware item is placed. The pot detection device allows that only those heating zones are activated, which are completely or partially covered by the cookware item. In particular, the cooking hob comprises at least one tempera ture sensor for each heating zone, wherein preferably at least one temperature sensor is provided for each heating element. For example, if the heating element is an induction coil or a radi ant heating element, then the temperature sensor is arranged in the centre of said induction coil or radiant heating element, respectively. Additionally or alternatively, a sensor for evalu ating the temperature of the cookware and or the food in the cookware item may be provided, for example an external sensor placed in the food, a vibration sensor, an optical system, a weight measuring sensor or a sensor for evaluating the electri cal characteristics inside the power boards of induction heated systems . The temperature sensor may be provided for detecting or evaluat ing the temperature of the cookware item placed on the heating zone(s) . Further, the temperature sensor may be provided for de tecting the temperature of the food in the cookware item placed over the heating zone(s) .

Moreover, at least one sensor for detecting a physical parameter related to the temperature of the food or water in the cookware item placed on the heating zone(s) may be provided.

Furthermore, any data output of the power board like frequency, power, phase angle of voltage and/or current, efficiency factor or any combination of these parameters may be used to compute the temperature of the cookware item and/or the food.

Further, the cooking hob may comprise a control unit for con trolling the temperature on each heating zone, preferably a con stant temperature on each heating zone. Furthermore, a method for performing a cooking process on a cooking hob for a domestic or an industrial appliance is dis closed, wherein said method comprises the steps of:

providing at least one heating area subdivided into at least two adjacent heating zones,

- adjusting or activating separately the temperature of each heating zone, and

placing a cookware item on one heating zone or on more adja cent heating zones, so that a desired cooking temperature is obtained .

The method provides that the heating area is subdivided into ad jacent heating zones with different temperatures. If the

cookware item is arranged above one heating zone, then the cook ing temperature corresponds with the temperature of said heating zone. If the cookware item is arranged above two adjacent heat ing zones, then the cooking temperature corresponds with an in termediate temperature of the temperatures of said adjacent heating zones. Thus, the user is able to change the cooking tem- perature by changing the position of the cookware item. Moreo ver, the temperature of each heating zone is defined by the user .

Further, the method may comprise the further step of recognising the heating zone or heating zones, on which the cookware item is placed. The recognition of the position of the cookware item al lows that only those heating zones are activated, which are com pletely or partially covered by the cookware item. In particular, the heating zones are defined by the user, wherein the temperatures of a plurality of heating elements of the cooking hob are separately adjusted by the user. Adjusted heating elements having the same temperature form the heating zone .

Further, the adjustment of temperatures on the heating zones may be stored. Preferably a fine adjustment of the temperatures on the heating zones is stored. Additionally, the adjustment or fine adjustment of temperatures on the heating zones is stored for at least one individual cookware item.

At last, the method may be provided for the cooking hob men- tioned above.

Novel and inventive features of the present invention are set forth in the appended claims. The present invention will be described in further detail with reference to the drawing, in which

FIG 1 illustrates a schematic top view of a heating area on a cooking hob according to a first embodiment of the pre sent invention,

FIG 2 illustrates a schematic top view of the heating area on the cooking hob according to a second embodiment of the present invention,

FIG 3 illustrates a schematic top view of the heating area on the cooking hob according to a third embodiment of the present invention,

FIG 4 illustrates a schematic top view of the heating area on the cooking hob according to a fourth embodiment of the present invention, wherein a cookware item is in a first position,

FIG 5 illustrates a schematic top view of the heating area on the cooking hob according to the fourth embodiment of the present invention, wherein the cookware item is in a sec ond position, and

FIG 6 illustrates a schematic top view of the heating area on the cooking hob according to the fourth embodiment of the present invention, wherein the cookware item is in a third position,

FIG 7 illustrates a block diagram showing the function of a closed loop automatic temperature control according to a first embodiment, FIG 8 illustrates a block diagram showing the function of a closed loop automatic temperature control according to a second embodiment. FIG 1 illustrates a schematic top view of a heating area 10 on a cooking hob according to a first embodiment of the present in vention .

The heating area 10 is subdivided into three rectangular heating zones 12, 14 and 16 arranged side by side. Preferably, the three heating zones 12, 14 and 16 have different temperatures. A first heating zone 12 has a high temperature. A second heating zone 14 has a medium temperature. A third heating zone 16 has a low tem perature. In this example, the heating zones 12, 14 and 16 are arranged with increasing temperatures, so that the heating zone 14 with the medium temperature is arranged between the heating zone 12 with the high temperature and the heating zone 16 with low temperature. For example, the one heating zone of heating zones 12, 14 and 16 with the highest temperature may be arranged closest to the user or the front of the cooking hob in order to allow that the food in the pan can be easier turned. However, in a special case, two or more heating zones 12, 14 and 16 may have the same temperature.

In particular, each heating zone 12, 14 and 16 comprises a tem perature sensor, so that the temperature on each heating zone 12, 14 and 16 is individually controllable.

For example, the high temperature in the first heating zone 12 is about 180°C, the medium temperature in the second heating zone 14 is about 150°C and the low temperature in the third heating zone 16 is about 100°C. In order to obtain a desired cooking temperature, a cookware item 18 has to be placed in a suitable position on the cooking area 10. If the desired cooking temperature corresponds with the temperature of one heating zone 12, 14 or 16, respectively, then the cookware item 18 has to be placed directly above the corresponding heating zone 12, 14 or 16. If an intermediate cooking temperature is desired, then the cookware item 18 has to be placed half on each on two adjacent heating zones 12, 14 and/or 16. For example, if a cooking tem- perature of 165°C is desired, then the cookware item 18 has to be placed one half each on the first heating zone 12 and on the second heating zone 14.

The cooking temperature is determined by the position of the cookware item 18 on the cooking area 10. The user determines the cooking temperature by selecting the position of the cookware item 18 on the cooking area 10. It is not necessary to adjust the desired cooking temperature. However, the temperatures in the heating zones 12, 14 and 16 may be adjustable by the user. For example, if the user requires five cooking temperatures of 100°C, 120°C, 140°C, 160°C and 180°C and has three adjacent heating zones 12, 14 and 16 available, the cooking temperatures of 100°C, 140°C and 180°C adjusted in said heating zones 12, 14 and 16. Then, the cooking temperatures of 100°C, 140°C and 180°C are obtained by placing the cookware item 18 on the correspond ing heating zones 12, 14 or 16. However, if the cooking tempera ture of 120°C is desired, then the cookware item 18 has to be placed one half each on the heating zone with 100°C and on the heating zone with 140°C. In a similar way, if the cooking tem- perature of 160°C is desired, then the cookware item 18 has to be placed one half each on the heating zone with 140°C and on the heating zone with 180°C. The cooking hob may be an induction cooking hob, a radiant cook ing hob, a gas cooking hob a combination thereof. Preferably, the cooking hob is an induction cooking hob or a radiant cooking hob. Each heating zone 12, 14 and 16 includes at least one heat- ing element. Preferably, each heating zone 12, 14 and 16 in cludes one heating element in order to obtain a cooking hob by low complexity. In particular, the cooking hob comprises a glass ceramic panel covering the heating zone 10, if the cooking hob is an induction cooking hob or a radiant cooking hob.

For example, each heating zone 12, 14 and 16 in FIG 1 includes an elliptic or rectangular induction coil. Alternatively, each heating zone 12, 14 and 16 in FIG 1 may include an elliptic, a rectangular or a triangular radiant heating element.

FIG 2 illustrates a schematic top view of the heating area 10 on the cooking hob according to a second embodiment of the present invention . The heating area 10 is subdivided into two rectangular heating zones 12 and 14 arranged side by side. Both heating zones 12, 14 and 16 have different temperatures. In this example, the first heating zone 12 has a low temperature, while the second heating zone 14 has a high temperature. The cookware item 18 is placed one half each on the first heating zone 12 and on the second heating zone 14. Thus, the cooking temperature in the cookware item 18 is an average of the temperatures in the first heating zone 12 and second heating zone 14. FIG 3 illustrates a schematic top view of the heating area 10 on the cooking hob according to a third embodiment of the present invention . The heating area 10 is subdivided into two rectangular heating zones 12 and 14 arranged side by side. Both heating zones 12 and 14 have different temperatures. In this example, the first heat ing zone 12 has a high temperature, while the second heating zone 14 has a low temperature. The first heating zone 12 in cludes two triangular heating elements 20 and 22. In a similar way, the second heating zone 14 includes two triangular heating elements 24 and 26. Said heating elements 20, 22, 24 and 26 may be induction coils and/or radiant heating elements.

The arrangement of the four triangular heating elements 20, 22, 24 and 26 in FIG 3 allows other subdivisions of the heating area 10 into heating zones by adjusting the temperatures of each tri angular heating element 20, 22, 24 and 26. In this case, each heating element 20, 22, 24 and 26 comprises particularly a tem perature sensor. For example, each triangular heating element 20, 22, 24 and 26 forms a corresponding heating zone, so that four heating zones with different temperatures are formed. Ac cording to another example, the second heating element 22 and the third heating element 24 form a central heating zone, while the first heating element 20 and the second heating element 26 form a separate outer heating zone in each case. In the latter case, the heating area comprises the central heating zone with the heating element 22 and 24 and the outer heating zones with the heating element 20 and 26, respectively. The central heating zone has the double size of the outer heating zone.

For example, the heating zones 12, 14 and 16 within the heating area 10 may be flexible. The heating zones 12, 14 and 16 may be also defined by the user, wherein the temperatures of a plural ity of heating elements are adjusted by the user as explained below . FIG 4 illustrates a schematic top view of the heating area 10 on the cooking hob according to a fourth embodiment of the present invention, wherein a cookware item 18 is in a first position. The heating area 10 comprises the first heating zone 12 and the second heating zone 14. The first heating zone 12 includes the first heating element 20 and the second heating element 22. The second heating zone 14 includes the third heating element 24 and the fourth heating element 26. In this embodiment, the first heating zone 12 is provided for a low temperature, while the second heating zone 14 is provided for a high temperature. The cookware item 18 in the first position is arranged above the second heating zone 14 and above the third heating element 24 and fourth heating element 26. In the cookware item 18 the low temperature is generated.

FIG 5 illustrates a schematic top view of the heating area 10 on the cooking hob according to the fourth embodiment of the pre sent invention, wherein the cookware item 18 is in a second po- sition.

The cookware item 18 in the second position is arranged par tially above the first heating zone 12 and partially above the second heating zone 14. Further, the cookware item 18 in the second position is arranged above the second heating element 22 and the third heating element 24. In the cookware item 18 an in termediate temperature between the low temperature of the first heating zone 12 and the high temperature of the second heating zone 14 is generated.

FIG 6 illustrates a schematic top view of the heating area 10 on the cooking hob according to the fourth embodiment of the pre sent invention, wherein the cookware item 18 is in a third posi tion . The cookware item 18 in the third position is arranged above the second heating zone 14 and above the first heating element 20 and the second heating element 22. In the cookware item 18 the high temperature is generated.

In general, the heating area 10 may comprise a plurality of heating elements, wherein said heating elements are arranged as a matrix. By adjusting the temperatures of each heating element the user may define individual heating zones 12, 14 and 16.

Thus, the user can determine the size and temperature of each heating zone. Then, the cooking temperature is determined by the position of the cookware item 18 on said heating area 10. Pref erably, a temperature sensor corresponds with each heating ele- ment .

FIG 7 illustrates a closed loop automatic temperature control for a induction cooking hob comprising three induction coils 301, 302, 303 as heating elements. The induction coils 301, 302, 303 are electrically associated to one power unit 400, e.g. be ing a power circuit board. The induction coils 301, 302, 303 can be driven by the power unit 400, or, in other words, the induc tion coils 301, 302, 303 can be supplied with energy from the power unit 400. The power unit 400 can drive each coil 301, 302, 303, but also can drive e.g. coils 301 and 302 jointly, thus, forming a joint heating zone comprising the coils 301 and 302 as heating elements. In this case that coil 303 can be driven sepa rately from the jointly driven coils, but it is also possible to form one joint heating zone comprising all three coils 301, 302, 303.

The control signal for controling the power unit 600 is output from the control unit 600. The control unit 600 comprises a pre defined control algorithm which determines the control signals to be output to the power unit 600 in order to achieve a defined temperature characteristic on the cookware item 18 place or po sitioned above the coils 301, 302, 303 by varying the energy output by the power unit 400. The control algorithm determines the necessary energy output and the corresponding control sig- nals to the power unit 600 on the basis of the temperature pa rameters as detected by the temperature sensors associated to each coil 301, 302, 303.

The temperature sensors associated with each coil 301, 302, 303 transfer signals representative of temperature parameters de tected by the temperature sensors to a temperature measurement unit 500. In the case that two or more coils 301, 302, 303 are coupled to enable a joint heating zone, it is possible that the temperature measurement unit 500 uses the parameter values transferred from one temperature sensor and disregards the pa rameter values from the other temperature sensors or that the temperature measurement unit 500 uses the parameter values transferred from all temperature sensors involved in the joint heating zone and calculates a value, e.g. a mean value or an av- erage value for being used by the control unit to determine the necessary energy supply to the heating elements in order to con trol the set temperature properly.

The automatic temperature control allows the cookware item 18 to be moved from one heating zone to another, e.g. from a first cooking zone operating with coil 301 to a joint cooking zone in cluding the coils 302, 303. Since the temperature measurement detects the temperature of the foodstuff within the cookware item or the temperature of the cookware item itself, the temper- atures set for the first cooking zone and for the joint cooking zone can be reached or maintained without any delay due to tem perature control, because the automatic temperature control ac cording to this embodiment allows to take the temperature on the first heating zone into account for the determination of the necessary energy to be supplied to the joint heating zone when the cookware item is moved to the joint heating zone. This is particularly advantagous in the case that the cookware item is moved to a heating zone where the cookware item shall be subject to lower temperatures.

In particular, it is possible, that the user can switch on the automatic temperature control by moving a cookware item on a specific heating zone, wherein the automatic temperature control is automatically switched on, when the cookware item is recog nized on the heating zone, e.g. by a pot detection system, or wherein the automatic temperature control can be switched on by a user by means of user interface. The temperature measurement can be based on principles known as surface acoustic wave measurement. Alternatively, it is possible that the delay time of the ceramic glas panel of the cooking hob is used to calculate the temperature of the cookware item placed on it. Further, alternatively, it is possible to detect tempera- tures of the cookware item or the foodstuff placed within the cookware item by analysis of the shape of the current or the shape of the voltage or from the behaviour of the induction fre quency . Although illustrative embodiments of the present invention have been described herein with reference to the accompanying draw ings, it is to be understood that the present invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the in vention. All such changes and modifications are intended to be included within the scope of the invention as defined by the ap pended claims. List of reference numerals

10 heating area

12 first heating zone

14 second heating zone

16 third heating zone

18 cookware item

20 first heating element

22 second heating element

24 third heating element

26 fourth heating element

301, ..., 304 induction coils

400, 401, 402 power unit

500 temperature measurement unit

600 control unit

M Movement