WO2017174630A1

WO2017174630A1 - Induction heating cooktop comprising a dual coil heating zone

Info

Publication number: WO2017174630A1
Application number: PCT/EP2017/058064
Authority: WO
Inventors: Metin OZTURK; Atakan SARIOGLU; Ulas OKTAY; Sercan SINIRLIOGLU
Original assignee: Arcelik Anonim Sirketi
Priority date: 2016-04-06
Filing date: 2017-04-05
Publication date: 2017-10-12

Abstract

The present invention relates to an induction heating cooktop (1) comprising an inner coil (2) and an outer coil (3) that are magnetically coupled, forming a concentric dual structure and generating magnetic energy for heating a vessel (12) placed on a heating zone (Z), a first power control circuit (4) that enables the inner coil (2) to be driven, a second power control circuit (5) that enables the outer coil (3) to be driven and a microcontroller (6) that controls the operation of the first and the second power control circuits (4, 5).

Description

INDUCTION HEATING COOKTOP COMPRISING A DUAL COIL HEATING ZONE

The present invention relates to an induction heating cooktop comprising a heating zone that has two concentric coils.

In induction heating cooktops, various induction coil structures have been developed for heating vessels with different sizes. The use of heaters that have concentric dual induction coils for heating both larger diameter vessels and smaller diameter vessels on the same heating zone with homogeneous heat distribution is known. Upon the detection of the vessel placed onto the dual induction coil heating zone, the heating process is performed by energizing the induction coils. When the diameter of the vessel that is placed onto the heating zone is small, the vessel only covers the inner coil and thus, only the inner coil is energized. When the diameter of the vessel that is placed onto the heating zone is large, the vessel covers both induction coils and thus, both induction coils are energized. For vessel detection, it is necessary to transmit a vessel detection signal to both concentric induction coils and this increases the software and hardware costs and gives rise to detection errors. Especially different detection frequencies applied to the concentric induction coils that are driven by different power supplies cause the generation of noises that disturbs the users. Errors in the vessel detection process result in excessive energy consumption, damage sensitive electronic components and prevent the vessel from being heated as needed.

The International Patent Application No. WO2015043650 discloses a dual coil induction heating cooktop.

The European Patent Applications EP1868417 and EP2342943 disclose a dual coil induction heating cooktop. The induction coils are energized by at least one power control unit.

The European Patent No. EP1943878 discloses an induction heating cooktop comprising a first heating zone having at least two induction coils energized separately by means of a power supply and an additional heating zone energized by a second power supply.

The aim of the present invention is the realization of an induction heating cooktop comprising a heating zone with two concentric coils, wherein the detection of the vessels is simplified.

In the induction heating cooktop with two concentric induction coils realized in order to attain the aim of the present invention, explicated in the first claim and the respective claims thereof, a detection signal is not transmitted to the outer coil for the detection of the presence of the vessel over the outer coil and only the inner coil is energized. The magnetic field generated by the inner coil induces a current on the outer coil. The current induced on the outer coil varies depending on whether the vessel is present on the outer coil. The said induced current is measured by means of a current measurement circuit and compared with a limit value by a microcontroller and it is determined whether the vessel covers the outer coil.

In the induction heating cooktop of the present invention, the time spent for the detection of the vessel placed onto the heating zone and hence starting the heating at the desired power level is decreased, and thus, energy is saved. It is not required to transmit detecting signals to the outer coil to detect the presence of the vessel, thus software and hardware costs are reduced and the noises are minimized.

The induction heating cooktop realized in order to attain the aim of the present invention is illustrated in the attached figures, where:

Figure 1 - is a schematic view of an induction heating cooktop in an embodiment of the present invention;

Figure 2 - is a schematic view of an induction heating cooktop in another embodiment of the present invention;

The elements illustrated in the figures are numbered as follows:

1- Induction heating cooktop

2 - Inner coil

3 - Outer coil

4- First power control circuit

5- Second power control circuit

6 - Microcontroller

7 - Current measurement circuit

8 - Bridge rectifier

9 - Drive circuit

10 - Resonant capacitor

11 - Power switch

12 - Vessel

Z: Heating zone

The induction heating cooktop (1) comprises an inner coil (2) and an outer coil (3) that are magnetically coupled, forming a concentric dual structure and generating magnetic energy for heating a vessel (12) placed on a heating zone (Z), a first power control circuit (4) that enables the inner coil (2) to be driven, a second power control circuit (5) that enables the outer coil (3) to be driven and a microcontroller (6) that controls the operation of the first and the second power control circuits (4, 5).

In the induction heating cooktop (1), when the vessel (12) is placed onto the heating zone (Z), whether the vessel (12) covers only the inner coil (2) or both the inner and the outer coils (2, 3) is detected before the heating process. After the detection of the vessel (12), according to whether the vessel (12) covers the inner and the outer coils (2, 3), in other words according to the size of the vessel (12), only the inner coil (2) or both the inner and outer coils (2, 3) are energized and the heating process is started at the power level set by the user.

The induction heating cooktop (1) of the present invention comprises the microcontroller (6) that, without transmitting a detection signal to the outer coil (3) to detect the presence of the vessel (12) on the outer coil (3), enables only the inner coil (2) to be energized by the first power control circuit (4) and that starts the heating process if the vessel (12) is present on the inner coil (2), and that detects whether the vessel (12) covers the outer coil (3) based on the magnitude of the current induced on the outer coil (3) as a result of the magnetic field generated by the inner coil (2).

In the induction heating cooktop (1), the inner and the outer coils (2, 3) concentrically disposed on the heating zone (Z) are magnetically coupled. The amount of the said magnetic coupling is directly correlated with the ratio of the area the vessel (12) covers over the inner and the outer coils (2, 3). In the embodiment of the present invention, by measuring how much the outer coil (3) is affected by the magnetic field created by the inner coil (2), it is determined whether the vessel (12) covers the outer coil (3) partially or completely, and the microcontroller (6) determines whether only the inner coil (2) or both the inner and the outer coils (2, 3) should be operated. When the induction heating cooktop (1) is operated, the first power control unit (4) transmits the vessel (12) detection signal to the inner coil (2), and if the presence of the vessel (12) is detected, the inner coil (2) is operated at the desired power level. In this case, as a result of the magnetic field created by the current passing through the inner coil (2), a current is induced on the magnetically coupled outer coil (3) at a value proportional to the diameter of the vessel (12). The value (magnitude) of the current induced on the outer coil (3) decreases or increases depending on the diameter of the vessel (12). If the diameter of the vessel (12) is large enough to at least partially cover the outer coil (3), the magnitude of the current induced on the outer coil (3) decreases due to the resistance of the vessel (12). If the vessel (12) has a diameter that is so small as to cover only the inner coil (3), the current induced on the outer coil (3) increases since there is not any vessel (12) resistance acting on the outer coil (3). The limit value of the current induced on the outer coil (3) is determined by the producer based on a vessel (12) with a diameter that is equal to the inner diameter of the outer coil (3) and the said limit induced current value is stored in the memory of the microcontroller (6).

The induction heating cooktop (1) further comprises a current measurement circuit (7) that is connected to the outer coil (3) and that measures the current induced on the outer coil (3) when the inner coil (2) is energized by the microcontroller (6) by means of the first power control circuit (4).

The microcontroller (6) compares the data received from the current measurement circuit (7) with the limit induced current value that is determined according to a vessel (12) with a diameter that is equal to the inner diameter of the outer coil (3), and determines whether the vessel (12) is present on the outer coil (3).

When the induced current on the outer coil (3) is lower than the limit induced current value, the microcontroller (6) determines that the vessel (12) at least partially covers the outer coil (3) and energizes the outer coil (3) with the power level set by the user.

When the induced current on the outer coil (3) is higher than the limit induced current value, the microcontroller (6) determines that there is no vessel (12) on the outer coil (3) and does not energize the outer coil (3).

In another embodiment of the present invention, both of the first and second power control circuits (4, 5) are half bridge series resonant circuits (HBSR) that comprise a bridge rectifier (8), a drive circuit (9), two resonant capacitors (10) and two power switches (11) such as insulated gate bipolar transistors (IGBT) (Figure 1).

In another embodiment of the present invention, both of the first and second power control circuits (4, 5) are single switch quasi resonant circuits (SSQR) that comprise a bridge rectifier (8), a drive circuit (9), a single resonant capacitor (10) and a single power switch (11) such as insulated gate bipolar transistors (IGBT) (Figure 2).

In the induction heating cooktop (1) of the present invention with the inner and the outer coils (2, 3), the presence of the vessel (12) on the outer coil (3) is detected by energizing only the inner coil (2). Whether the vessel (12) at least partially covers the outer coil (3) or not is determined by measuring the current induced on the outer coil (3). Thus, the need for transmitting a signal by the second power control circuit (5) in order to detect the presence of the vessel (12) on the outer coil (3) and measuring the inductance, resistance and resonant frequency, etc. of the outer coil (3) is obviated, thus the vessel (12) detection process is simplified and the heating process is started quicker. Moreover, the software and hardware costs are decreased. Furthermore, the noise that is generated during the detection of the vessel (12) on the inner and the outer coils (2, 3) and that disturbs the user is reduced.

Claims

An induction heating cooktop (1) comprising an inner coil (2) and an outer coil (3) that are disposed concentrically and that generate magnetic energy for heating a vessel (12) placed on a heating zone (Z), a first power control circuit (4) that enables the inner coil (2) to be driven, a second power control circuit (5) that enables the outer coil (3) to be driven and a microcontroller (6) that controls the operation of the first and the second power control circuits (4, 5), characterized by the microcontroller (6) that, without transmitting a detection signal to the outer coil (3) to detect the presence of the vessel (12) on the outer coil (3), enables only the inner coil (2) to be energized by the first power control circuit (4) and that detects whether the vessel (12) covers the outer coil (3) based on the magnitude of the current induced on the outer coil (3) as a result of the magnetic field generated by the inner coil (2).
An induction heating cooktop (1) as in Claim 1, characterized by a current measurement circuit (7) that is connected to the outer coil (3) and that measures the current induced on the outer coil (3) when the inner coil (2) is energized by the microcontroller (6) by means of the first power control circuit (4).
An induction heating cooktop (1) as in Claim 1 or 2, characterized by the microcontroller (6) that compares the data received from the current measurement circuit (7) with the limit induced current value that is determined according to a vessel (12) with a diameter that is equal to the inner diameter of the outer coil (3), and determines whether the vessel (12) is present on the outer coil (3).
An induction heating cooktop (1) as in Claim 3, characterized by the microcontroller (6) that determines that the vessel (12) at least partially covers the outer coil (3) and energizes the outer coil (3) at the power level set by the user when the induced current on the outer coil (3) is lower than the limit induced current value.
An induction heating cooktop (1) as in Claim 3, characterized by the microcontroller (6) that determines that there is no vessel (12) on the outer coil (3) and does not energize the outer coil (3) when the induced current on the outer coil (3) is higher than the limit induced current value.
An induction heating cooktop (1) as in Claim 1, characterized by the first and second power control circuits (4, 5) that are half bridge series resonant circuits comprising a bridge rectifier (8), a drive circuit (9), two resonant capacitors (10) and two power switches (11).
An induction heating cooktop (1) as in Claim 1, characterized by the first and second power control circuits (4, 5) that are single switch quasi resonant circuits comprising a bridge rectifier (8), a drive circuit (9), a single resonant capacitor (10) and a single power switch (11).