WO2016010491A1

WO2016010491A1 - System and method enabling modification of cookware positioning in an induction heating cooker

Info

Publication number: WO2016010491A1
Application number: PCT/TR2014/000282
Authority: WO
Inventors: Namik Yilmaz; Selçuk SOYYIĞIT; Tolga INAM; Metin ÖZTÜRK; Metin ASTOPRAK; Mehmet BARIS; Özgür Mutlu OZ; Bekir DUMLU
Original assignee: Arcelik Anonim Şirketi
Priority date: 2014-07-15
Filing date: 2014-07-15
Publication date: 2016-01-21
Also published as: PL3170362T3; ES2675239T3; EP3170362B1; EP3170362A1

Abstract

The present invention relates to a 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 ENABLING MODIFICATION OF COOKWARE POSITIONING IN AN INDUCTION HEATING COOKER

The present invention relates to a method for operating an induction heating cooker by which cookware positioning can be modified according to available input by a position detection circuit.

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 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. To this end, older or technology-averse people should also be able to immediately implement the method of operation according to the invention.

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 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 method for operating an induction heating cooker by which a cooking container of any size is heatable by induction heating as provided by the characterizing features defined in Claim 1. Primary object of the present invention is to provide a method for operating an induction heating cooker by which a cooking container of any size is heatable by a limited number of induction coils sufficiently small to obtain flexible cooking zones.

The present invention proposes a method for operating an induction heating cooker by which if up to three adjacent induction coils are selected to be powered, no user interaction is required and a cooking pan is automatically heated. And if a cooking pan is found to be located on more than three adjacent induction coils, the user is requested to limit the number of coils to be powered. The user can select a suggested cooking zone pattern on a graphic display and accordingly move the pan. The limited number of adjacent induction coils can only be in multiples of two. Therefore, 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. 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 flow diagram of the method for operating an induction heating cooker according to the present invention.

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

Fig. 4 demonstrates a general 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.

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 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 leveling capacitor serves to the purpose of filtering high frequency current. The voltage of the leveling 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). According to the method of operating the induction heating cooker (1), presence of at least three adjacent induction coils (2) are to be verified first.

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 that three adjacent induction coils (2) occupy a surface area as large as to cover the base of a larger pan (6) and 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 (1 ) 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 (11) 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 cooking zones (11) is too small, although more efficient cooking with more accurate cooking zones (11) 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 cooking zone (1 1) can feed power to a smaller size container, a larger size container is heatable by at most three adjacent induction coils (2). The induction coils (2) can be adjacent in any direction, i.e. horizontally and/or vertically.

According to the invention, if more than three adjacent induction coils (2) are detected as having a ferromagnetic container thereon, the user is asked to displace the container to a predetermined neighboring location containing a number of induction coils (2) in the form of multiples of two. In this manner, if four induction coils (2) are detected, only two or all four of those will be operable upon selection of the user by moving the pan (6), as suggested to him/her on the graphic display (12).

If a cooking pan (6) on more than three adjacent induction coils (2) is detected, user intervention is requested because three adjacent induction coils (2) are found to be sufficiently large for a standard larger size pan (6). The user is therefore invited to make a selection between suggested predetermined neighboring cooking zones (11) by reference to the graphic representation thereof and displace the cooking pan (6) to the selected cooking zone (11). The suggested predetermined neighboring cooking zones (11) can have a number of induction coils (2) in the form of multiples of two, because it is observed that in the case of more than three induction coils (2), mostly two or rarely four and even more rarely six adjacent induction coils (2) should define a suitable cooking zone (11) corresponding to any size of standard shape pans (6) also including non-standard,, i.e. non-circular pans (6).

Therefore, the present invention provides that while a smaller pan (6) can be heated by a single induction coil (2), a plurality of induction coils (2) up to three can heat any larger pan (6). And if a pan (6) is detected on more than three adjacent coils (2), a number of induction coils (2) in the multiples of two will be sufficient for covering any pan (6) rather than a cooking zone (11) having an odd number of induction coils (2), because a cooking zone (11) formed by the combination of five or seven inductions coils (2) does not fit to any standard-size circular pan (6) or is out of shape to match a non-standard (non-circular) pan (6). 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 a 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 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), 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).

The induction heating cooker (1) of the invention comprises a control circuitry (10), effecting, a) detection of presence of at least one cooking pan (6) on the vitro-ceramic glass (7) by means of said pan detection circuit (8), 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, c) verification in that said at least one cooking pan (6) is detected on at least three adjacent induction coils (2), d) merging of said at least three adjacent induction coils (2) to obtain a single cooking zone (11) of at least three adjacent induction coils (2), e) requesting of user intervention if a cooking pan (6) on more than three adjacent induction coils (2) is detected and, f) generation of a graphic representation of predetermined neighboring cooking zones (11) the cooking pan (6) is to be displaced, said predetermined neighboring cooking zones (11) containing a number of induction coils (2) in the form of multiples of two.

In one 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 still 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 yet still further embodiment of the present invention, each induction coil (2) is structured to have a rectangular, triangular or circular form.

In a yet still 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 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 with a minimal number of induction coils (2) whereby a cooking container/pan (6) of any size can be heated by induction heating.

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), 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 said 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,

- verification in that at least one cooking pan (6) is detected on at least three adjacent induction coils (2),

- merging of at least three adjacent induction coils (2) to obtain a single cooking zone (11) of at least three adjacent induction coils (2),

- requesting of user intervention if a cooking pan (6) on more than three adjacent induction coils (2) is detected and

- generation of a graphic representation of predetermined neighboring cooking zones (11) the cooking pan (6) is to be displaced, said predetermined neighboring cooking zones (11) containing a number of induction coils (2) in the form of multiples of two.

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

4) An induction heating cooker (1) as in Claim 2 or 3, 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.

5) An induction heating cooker (1) as in Claim 2, 3 or 4, characterized in that each induction coil (2) is structured to have a rectangular, triangular or circular form.

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

7) An induction heating cooker (1) as in Claim 6, characterized in that the largest distance between two different portions of an induction coil (2) is 120 mm.