EP3169939A1

EP3169939A1 - System and method for the operation of an induction heating cooker

Info

Publication number: EP3169939A1
Application number: EP14815098.0A
Authority: EP
Inventors: Namik Yilmaz; Metin ASTOPRAK; Metin ÖZTÜRK; Tolga INAM; Özgür ÖZ; Selçuk SOYYIGIT; Mehmet BARIS; Yunus TUNAK
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2014-07-15
Filing date: 2014-07-15
Publication date: 2017-05-24
Also published as: WO2016010490A1

Abstract

The present invention relates to a system and method for operating an induction heating cooker (1) comprising a plurality of induction coils (2) in association with induction resonant inverters (4) to provide multi-zone induction coils (3), a power switch driving circuit (5) driving power switches associated with the induction resonant inverters (4), a pan detection circuit (8) and a user interface (14) having a graphic display (12), the induction heating cooker (1) further comprising a vitro-ceramic glass (7) surface containing no surface indication as to suggestible placement of a pan (6).

Description

SYSTEM AND METHOD FOR THE OPERATION OF AN INDUCTION

HEATING COOKER

The present invention relates to a system and method for the operation of an induction heater cooker.

It is well-known that an induction heating cooker operates based on the process of heating a ferromagnetic material by electromagnetic induction where eddy currents are to be induced and resistance provides heat dissipation within the ferromagnetic material, i.e. a cooking vessel in the form of a pot or pan.

By induction heating, high-frequency alternating current is passed through a coil upon which a magnetic field of the same frequency is induced. The internal resistance of the pan causes heat dissipation due to Joule effect and energy transfer is interrupted once the pan is removed from the cooktop. The energy efficiency of induction heating cookers is considerably high since there is no transfer of heat energy between the hob and the cookware and heat energy lost in the air is minimal.

A resonant converter in an induction heater circuit topology typically consists of a capacitor, an inductor and resistance. To this end, when power is supplied to the resonant tank, electric energy is stored in the inductor and transferred to the capacitor. Resonance therefore occurs while the inductor and the capacitor involve in energy exchange. The resonant converter can be a half-bridge series resonant converter or a quasi-resonant converter.

A quasi-resonant converter exhibits certain advantages over a half-bridge series resonant converter especially due to its simpler circuit design having only one power switching device compared to the half-bridge series resonant converter whose overall operation is more complex. The circuit design parameters in a quasi-resonant converter are regarded as a serious cost advantage in this regard. In order to drive the resonant inductor generating magnetic field and in turn inducing eddy currents on the skin depth of a cooking vessel, a high-frequency power switch such as an IGBT is accordingly used.

Among others, a prior art publication in the technical field of the invention may be referred to as EP 1 629 698 Bl, which discloses an induction cooking system including a power inverter, a microprocessor, a protection circuit and a pan detection circuit.

The present invention provides a simple yet effective method by which a number of sufficiently small cooking zones are created to provide a flexible-distribution cooking surface to correspond to a cooking container of any size. The present invention provides a plurality of distinct induction coils driven by respective resonant inverters such that a plurality of flexible cooking zones can be created with a minimal number of induction coils whereby a cooking container of any size can be heated by induction heating. The present invention is devised under the recognition that a significantly simple and immediately practical method of operating an induction heating cooker remains a great need because induction heating cookers are reported to be generally used by younger people having a certain inclination towards non- traditional technologies such as induction cooking.

In this regard, the present invention provides a graphic display demonstrating graphic representation of different-size cooking containers and enables configuration of the cooking zones in an intuitively efficient manner without a touch interaction graphic display, to be operable by older people.

Touch screen user interfaces, beside the fact that they have a role in increasing costs, are viewed more complex to be operated by older people. Apart from this, the cooking environment may have a negative impact on the performance of the touch screen due to humidity and vapor density. To this end, the invention is devised under the recognition that older or technology-averse people should also be able to immediately implement the method of the invention.

The present invention provides a system and method for the operation of an induction heating cooker enabling configuration of the cooking zones in an intuitively efficient manner without making use of a touch control user interface as provided by the characterizing features defined in Claim 1.

Primary object of the present invention is to provide a system and method for the operation of an induction heating cooker by which flexible cooking zones are configurable on a graphic display in an intuitively efficient manner without using a touch screen display.

The present invention proposes a system and method for operating an induction heating cooker by which presence of at least one cooking pan is detected and a corresponding graphic representation is generated on a graphic display. A plurality of flexible cooking zones can be created with a minimal number of induction coils whereby a cooking container of any standard size can be heated.

Further, a plurality of graphic zone indicators is provided such that each zone indicator is individually associatable with different cooking zones and a control button near the zone indicator effects selection of said zone. A specific zone and a zone indicator in relation therewith do have a common indication such as an identical color and/or number. Navigation indicators and setting indicators are generated on the graphic display for allowing navigation between different screens and selection of different settings.

The diameter of a circular-form induction coil according to the invention is preferably between 100 and 140 mm. In the case of other forms of induction coils, such as square, rectangular, triangular etc., the largest distance between two different opposite portions can be determined in the same range. Accompanying drawings are given solely for the purpose of exemplifying an induction heating cooker, whose advantages over prior art were outlined above and will be explained in brief hereinafter.

The drawings are not meant to delimit the scope of protection as identified in the Claims, nor should they be referred to alone in an effort to interpret the scope identified in said Claims without recourse to the technical disclosure in the description of the present invention.

Fig. 1 demonstrates a simplified general block diagram representation of an induction heating cooker system according to the present invention.

Fig. 2 demonstrates a general top view of the induction heating cooker with different size food containers according to the present invention. Fig. 3 demonstrates a general top view of the graphic display of the induction heating cooker with visualization of different size food containers according to the present invention.

Fig. 4 demonstrates a general top view of the user interface of the induction heating cooker with visualization of different size food containers on the graphic interface according to the present invention.

Fig. 5 demonstrates a general top view of the graphic display of the induction heating cooker with visualization of different size food containers and zone switching/navigation indicators according to the present invention. Fig. 6 demonstrates a general top view of the graphic display of the induction heating cooker with the zone configuration screen according to the present invention. The following numerals are assigned to different part number used in the detailed description:

1) Induction heating cooker

2) Induction coil

3) Multi-zone induction coils

4) Induction resonant inverter

5) Power switch driving circuit

6) Pan

7) Vitro-ceramic glass

8) Pan detection circuit

9) Display driver circuit

10) Control circuitry

11) Cooking zone

12) Graphic display

13) Control buttons

14) User interface

15) Zone indicator

16) Navigation indicator The present invention proposes an induction heating cooker (1) having a plurality of induction coils (2) in the form of multi-zone induction coils (3). A power circuit in relation with each induction coil (2) provides that heat energy is induced within a magnetically responsive cooking container or pan (6) placed above the induction coils (2) of the induction heating cooker (1).

The induction heating cooker (1) may comprise a plurality of induction resonant inverters (4) supplied with a source of AC voltage. In the case of quasi-resonant converters having a single power switch, a full-wave bridge rectifier may be connected between the AC source and power stage of the resonant inductor. The resonant inductor is conventionally connected between the output of said rectifier and the power switch. The resonant capacitor is parallel to the resonant inductor and an anti-parallel diode, i.e. a freewheeling diode is connected parallel to the power switch.

The induction resonant inverters (4) of the induction heating cooker (1) may conventionally comprise AC signal filtering circuits. Power passing through a levelling capacitor together with filtering inductor serves to the purpose of filtering high frequency current. The voltage of the levelling capacitor is converted into a square wave by the high-frequency power switch. According to Ampere's Law, the square wave provides resonance creating a magnetic field around the resonant inductor, that is, the respective induction coil (2). The resonant capacitor provided in parallel with the resonant inductor therefore compensates the inductive nature of the latter.

The quasi-resonant converter's power switch may be an insulated gate bipolar transistor (IGBT) driven by a power switch driving circuit (5). The operating principle of the quasi-resonant converter typically relies on the storage of energy in the resonant inductor when the power switch is turned on, and transfer of energy from the resonant inductor to a cooking pan (6) when the power switching device is turned off.

To detect cookware presence on a vitro-ceramic glass (7) surface of the induction heating cooker (1) and also to detect its position accurately, a pan detection circuit (8) sensing cookware positioning is used. Such a pan detection circuit (8) can monitor the resonant current or the IGBT voltage. An electronic circuit that generates an output at the moment which the freewheeling diode starts conduction can be used. A charge detection circuit therefore detects the zero-cross of the current of the freewheeling diode. Pan detection techniques in induction heating cookers are extensively used in the state of the art and being known to the skilled worker will as such not be further discussed herein. According to the invention, a user interface (14) with control buttons (13) and a graphic display (12) being controlled by a display driver circuit (9) are provided to enable the user to operate the induction heating cooker (1) functioning according to the method as described hereinafter. In accordance with the invention, the vitro-ceramic glass (7) contains no surface indication as to suggested placement of a cookware or utensil and a user can place a pan (6) anywhere on the vitro-ceramic glass (7) surface he/she wishes. To this end, the pan detection circuit (8) detects presence of at least one cooking pan (6) on the vitro-ceramic glass (7) and the user interface (14) generates a graphic representation of the detected cookware placement as currently placed on the graphic display (12).

As induction heating cookers (1) are reported to be generally used by younger people having a certain inclination towards non-traditional technologies such as induction cooking, the invention ensures that older or technology-averse people can also immediately implement the method of operation according to the invention.

It is known that cooking utensils are manufactured in certain standard sizes such as having base diameters of 105, 145, 180, 210 or 288 mm. According to the present invention, it is established a single induction coil (2) itself can supply alone sufficient power to a smaller size pan (6), while at the same time providing a sufficiently small cooking zone (11) to provide a distributed-configuration cooking surface. Such a flexible cooking surface allows simultaneous powering of a certain number of induction coils (2) to provide versatile cooking zones (1 1) corresponding to cooking pans (6) of different sizes, including those with non- standard, i.e. non-circular shapes. Therefore, a flexible surface configuration can be maintained with a limited number of induction coils (2), those being sufficiently small in size to provide flexible cooking zones (11) and sufficiently large to keep the total number of induction coils (2) limited, while at the same time creating optimum size cooking zones (11) for powering cooking pans (11) of different sizes, including non-standard ones.

If the size of individual induction coils (2) is too small, although more efficient cooking with more accurate cooking zones (1 1) can be obtained, a large number of induction coils (2) with respective induction resonant inverters (4) will be necessary. On the other hand, if substantially large induction coils (2) are provided, the efficiency will again be low. Therefore, an induction heating cooker (1) being versatile and flexible, yet having a reduced number of induction coils (2) creating, when combined, cooking zones (11) corresponding to the existing standard sizes of the cooking equipment is proposed in the manner that while a single induction coil (2) can feed power to a smaller size container, a larger size container is heatable by adjacent induction coils (2).

According to the invention, the control circuitry (10) provides that generation of graphic representation of zone indicators (15) on the graphic display (12) of the user interface (14) is effected. According to the invention, a zone indicator (15) is a specific-shape graphic generated on the graphic display (12) to be individually associatable with different cooking zones (11). Each zone indicator (15) is therefore individually associatable with a specific cooking zone (1 1) and the association between a zone indicator (15) and a cooking zone (11) is established by way of using same colors or numbers for each pair of associated zone indicator (15) and cooking zone (11). The user may select the preferred zone among a plurality of alternative cooking zones (11) for a pan position and may displace the cooking pan (6) by reference to the graphic representation thereof to another cooking zone (11). In accordance with the invention, a graphic display (12) demonstrating graphic representation of different-size cooking containers is provided so as to enable configuration of the cooking zones (11) in an intuitively efficient manner although no touch interaction is possible on said graphic display (12). Touch screen user interfaces are considered to be more complex to be operated by older people. Apart from this, they are costly and the cooking environment may have a negative impact on the performance thereof due to humidity and vapor density.

To this end, the control circuitry (10) may also provide that a specific zone indicator (15) is associated with the respective cooking zone (11) both by the same color and number being visible on said specific zone indicator (15), the specific zone indicator (15) being directly in the vicinity of an individual control button (13), and therefore being selectable by way of pressing said control button (13). In -this regard, the invention ensures that a cooking zone (11) as detected by the pan detection circuit (8) can be selected in an intuitively efficient manner without necessarily using a touch screen graphic display. The zone indicators (15) that are easily associated with the detected cooking zones (11) in a visual manner allow selection of the respective zones by way of pressing a control button (13) placed immediately below or near the specific zone indicator (15).

Further, apart from the aspect of practical selection of a cooking zone (11), the user is allowed to navigate between different settings by means of navigation indicators (16), in which case a respective control button (13) adjacent to the navigation indicator (16) will perform to select the respective navigation indicator (16). The present invention therefore ensures that a visual object on the graphic display (12) in the form of a zone indicator (15) or navigation indicator (16) is easily paired with a physical control button (13) so as to operate the induction heating cooker (1) in an intuitively efficient manner without using a touch screen graphic display.

According to the present invention, if a cooking zone (11) is selected by the user by pushing a respective control button (13) adjacent to a respective zone indicator (15), the power and timer settings of the selected cooking zone (1 1) can be adjusted on a subsequent screen by means of similar setting indicators and adjacent control buttons (13). Likewise, when a cooking zone (11) is selected, the user may use a further setting indicator and a respective control button (13) to merge neighboring zones or split a selected zone into smaller ones. Further, the invention also provides that a graphic representation of residual heat map is generated on the graphic screen (12) after the cooking operation is terminated. According to the present invention, the largest distance between two portions of an induction coil (2) is between 100 and 140 mm, and preferably between 110 and 130 mm and more preferably 120 mm.

In a nutshell, the present invention proposes an induction heating cooker (1) comprising a plurality of induction coils (2) in association with induction resonant inverters (4) to provide multi-zone induction coils (3), a power switch driving circuit (5) driving power switches associated with the induction resonant inverters (4), a pan detection circuit (8) for detecting presence of a pan (6) and a user interface (14) having a graphic display (12) enclosed by a plurality of physical control buttons (13), the induction heating cooker (1) further comprising a vitro- ceramic glass (7) surface containing no surface indication as to suggestible placement of a pan (6).

A control circuitry (10) effects, a) automatic detection of presence of at least one cooking pan (6) on the vitro-ceramic glass (7) by means of the pan detection circuit (8) as soon as the hob is energized for a certain period, b) generation of a graphic representation of the detected at least one cooking pan (6) on the graphic display (12) of the user interface (14) as being currently placed and, c) generation of graphic zone indicators (15) on the graphic display (12) of the user interface (14), each zone indicator (15) being individually associatable with different cooking zones (1 1) and being directly in the vicinity of an individual control button (13).

In one embodiment of the present invention, each zone indicator (15) is individually associatable with a specific cooking zone (11) in the manner that the association between a zone indicator (15) and a cooking zone (11) is established by way of using same colors and/or numbers for each pair of associated zone indicator (15) and cooking zone (11).

In a further embodiment of the present invention, the graphic display (12) comprises navigation indicators (16) allowing navigation between different screens in the manner that a respective control button (13) adjacent to a navigation indicator (16) performs to select the respective navigation indicator (16).

In a further embodiment of the present invention, the graphic display (12) comprises setting indicators allowing adjusting different settings in the manner that a respective control button (13) adjacent to a setting indicator performs to select the respective setting indicator.

In a further embodiment of the present invention, a refresh button is displayed to reactivate the pan detection circuit (8) for a certain period of time.

In a further embodiment of the present invention, a graphic representation of residual heat map is generated on the graphic screen (12) after the cooking operation is terminated. Said residual heat map comprises color indicated heat distribution map of the induction heating cooker (1) surface independent of the surface distribution of the most recently determined cooking zones (11), because heat distribution may be effected by other environmental factors and temperature in association with every individual induction coil's (2) effect area on the vitro- ceramic glass (7) surface should be measured and a corresponding heat distribution map should be generated for the sake of safety. In a further embodiment of the present invention, the largest distance between two different portions of an induction coil (2) is preferably between 100 and 140 mm.

In a further embodiment of the present invention, each induction coil (2) is comprised of a plurality of separately powerable sub-coils.

In a further embodiment of the present invention, the induction heating cooker (1) comprises at least nine induction coils (2) in the form of a 3x3 induction coil (2) square matrix. The method of the invention can therefore advantageously be implemented by just nine induction coils (2), while still providing a flexible- configuration cooking surface in the form of multi-zone induction coils (3).

In a further embodiment of the present invention, each induction coil (2) is structured to have a rectangular, triangular or circular form. In a further embodiment of the present invention, the largest distance between two different portions of an induction coil (2) is preferably between 110 and 130 mm and more preferably 120 mm.

Therefore, a system and significantly simple and immediately practical method of operating an induction heating cooker (1) is proposed such that a plurality of flexible cooking zones (11) can be created while a plurality of cooking zones (1 1) can be selected and the induction heating cooker (1) can be operated in an intuitively efficient manner without using a touch screen graphic display.

Claims

1) An induction heating cooker (1) comprising a plurality of induction coils (2) in association with induction resonant inverters (4) to provide multi-zone induction coils (3), a power switch driving circuit (5) driving power switches associated with said induction resonant inverters (4), a pan detection circuit (8) for detecting presence of a pan (6) and a user interface (14) having a graphic display (12) enclosed by a plurality of control buttons (13), said induction heating cooker (1) further comprising a vitro-ceramic glass (7) surface containing no surface indication as to suggestible placement of a pan (6) characterized in that a control circuitry (10) configured to effect:

- detection of presence of at least one cooking pan (6) on the vitro-ceramic glass (7) by means of the pan detection circuit (8),

- generation of a graphic representation of the detected at least one cooking pan (6) on the graphic display (12) of the user interface (14) as being currently placed and

- generation of graphic zone indicators (15) on the graphic display (12) of the user interface (14), each zone indicator (15) being individually associatable with different cooking zones (1 1) and being directly in the vicinity of an individual control button (13).

2) An induction heating cooker (1) as in Claim 1, characterized in that each zone indicator (15) is individually associatable with a specific cooking zone (1 1) in the manner that association between a zone indicator ( 1 ) and a cooking zone (11) is established by way of using same colors or numbers for each pair of associated zone indicator (15) and cooking zone (1 1).

3) An induction heating cooker (1) as in Claim 1 or 2, characterized in that the graphic display (12) comprises navigation indicators (16) allowing navigation between different screens in the manner that a respective control button (13) adjacent to a navigation indicator (16) performs to select the respective navigation indicator (16).

4) An induction heating cooker (1) as in Claim 1, 2 or 3, characterized in that the graphic display (12) comprises setting indicators allowing adjusting different settings in the manner that a respective control button (13) adjacent to a setting indicator performs to select the respective setting indicator.

5) An induction heating cooker (1) as in Claim 1 , 2 or 3, characterized in that a graphic representation of residual heat map is generated on the graphic screen (12) after a cooking operation is terminated.

6) An induction heating cooker (1) as in Claim 5, characterized in that the residual heat map comprises color indicated heat distribution map of the induction heating cooker (1) surface independent of the surface distribution of most recently determined cooking zones (11).

7) An induction heating cooker (1) as in any one of the above claims, characterized in that a refresh button is displayed to reactivate the pan detection circuit (8) for a certain period of time.

8) An induction heating cooker (1) as in Claim 1, characterized in that the largest distance between two different portions of an induction coil (2) is between 100 and 140 mm.

9) An induction heating cooker (1) as in Claim 8, characterized in that each induction coil (2) is comprised of a plurality of separately powerable sub-coils.

10) An induction heating cooker (1) as in Claim 8 or 9, characterized in that the induction heating cooker (1) comprises at least nine induction coils (2) in the form of a 3x3 induction coil (2) matrix. 1 1) An induction heating cooker (1) as in Claim 8, 9 or 10, characterized in that each induction coil (2) is structured to have a rectangular, triangular or circular form.

12) An induction heating cooker (1) as in Claim 8, characterized in that the largest distance between two different portions of an induction coil (2) is between 110 and 130 mm. 13) An induction heating cooker (1) as in Claim 12, characterized in that the largest distance between two different portions of an induction coil (2) is 120 mm.