Induction cooking apparatus employing noise reduction method

Abstract

An induction heating apparatus according to one embodiment of the present invention includes: a first operating coil for a first burner; a second operating coil for a second burner; an inverter including a plurality of switches that are switched so that current flows in the first operating coil and the second operating coil; and a processor for controlling the switching of the plurality of switches of the inverter, wherein the operating frequency of the first operating coil and the operating frequency of the second operating coil differ by at least a predetermined frequency value due to the inductance value of the first operating coil and the inductance value of the second operating coil.

Description

Induction cooking appliances that employ noise reduction methods

[0001] The present disclosure relates to a method for reducing noise in an induction cooking device having multiple burners and an induction cooking device employing such a method.

[0002] An induction range is a cooking appliance that utilizes the principle of induction heating. Commonly called induction, induction cooking equipment, or induction heating equipment, induction ranges do not consume oxygen and do not emit waste gases compared to gas ranges, thereby reducing indoor air pollution and temperature increases. Furthermore, induction ranges utilize an indirect method of inducing heat to the heated object itself, resulting in high energy efficiency and stability. Furthermore, since heat is generated only within the heated object itself and not the contact surface, there is a low risk of burns, which has led to a continued increase in demand for induction ranges.

[0003] Induction ranges can include multiple burners. Each burner has a separate control button. Users can identify the burner on which a container is placed and use the corresponding control button to perform cooking.

[0004] According to one embodiment of the present disclosure, an induction heating device includes a first working coil for a first burner having a circular shape. According to one embodiment, the induction heating device includes a second working coil for a second burner having a square shape. According to one embodiment, the induction heating device includes an inverter including a plurality of switches for switching current to flow through the first working coil and the second working coil, and a processor for controlling switching of the plurality of switches of the inverter. According to one embodiment, an operating frequency of the first working coil and an operating frequency of the second working coil differ by a predetermined frequency value or more due to an inductance value of the first working coil and an inductance value of the second working coil.

[0005] In an induction heating device according to one embodiment of the present disclosure, the inverter further includes a first resonant capacitor resonating with a first working coil, and a first switch and a second switch that are switched on and off for resonance between the first working coil and the first resonant capacitor, wherein the processor controls the on-duty ratio of the first switch and the second switch to a fixed value during asymmetric control.

[0006] According to one embodiment of the present disclosure, an induction heating device includes a first working coil for a first burner. According to one embodiment, the induction heating device includes a second working coil for a second burner. According to one embodiment, the induction heating device includes an inverter including a plurality of switches for switching current to flow through the first working coil and the second working coil, and a processor for controlling switching of the plurality of switches. According to one embodiment, a maximum operating frequency of the first working coil and a maximum operating frequency of the second working coil differ by 5 kHz or more.

[0007] In an induction heating device according to one embodiment of the present disclosure, the first crater has a circular shape, and the second crater has a square shape.

[0008] In an induction heating device according to one embodiment of the present disclosure, a noise reduction method includes a step of operating a first working coil for a first crater having a circular shape and a second working coil for a second crater having a square shape according to a user's input. In one embodiment, the noise reduction method includes a step of determining whether the operating frequencies of the first working coil and the second working coil differ by a predetermined frequency value or more. In one embodiment, the noise reduction method includes a step of performing asymmetric control so that an on-duty ratio of a third switch among a third switch and a fourth switch that are turned on and off for resonance between the second working coil and the second resonance capacitor is greater than an on-duty ratio of the fourth switch, based on a determination that the operating frequencies of the first working coil and the second working coil do not differ by a predetermined frequency value or more.

[0009] Aspects, features and advantages of one embodiment of the present disclosure will become more apparent with reference to the accompanying drawings described below.

[0010] FIG. 1A and FIG. 1B are drawings for explaining an induction heating device according to one embodiment of the present disclosure.

[0011] FIG. 2 is a cross-sectional view of a cooking vessel placed on an induction heating device according to one embodiment of the present disclosure.

[0012] FIG. 3 is an inverter circuit diagram of an induction heating device for operating a plurality of operating coils according to one embodiment of the present disclosure.

[0013] Fig. 4 is a switching diagram of an inverter circuit of an induction heating device according to one embodiment of the present disclosure.

[0014] FIG. 5 is a waveform diagram of resonant currents detected in a plurality of operating coils according to one embodiment of the present disclosure.

[0015] FIG. 6a is a diagram showing asymmetric control switching in an inverter circuit of an induction heating device according to one embodiment of the present disclosure.

[0016] FIG. 6b is an asymmetric control flowchart of an induction heating device according to one embodiment of the present disclosure.

[0017] FIGS. 7A and 7B illustrate an induction heating device using a square working coil according to one embodiment of the present disclosure.

[0018] FIG. 8 is a drawing showing an induction heating device according to one embodiment of the present disclosure together with a working coil.

[0019] FIG. 9 is a graph showing the inductance of a square operating coil and a circular operating coil according to one embodiment of the present disclosure.

[0020] FIG. 10A is a graph showing the resonant frequency of each working coil according to one embodiment of the present disclosure.

[0021] FIG. 10b is a graph showing the resonant frequency of each working coil according to one embodiment of the present disclosure.

[0022] FIG. 11 is a graph showing the frequency difference by crater according to one embodiment of the present disclosure.

[0023] FIG. 12 is a drawing showing a cooking vessel being placed on an induction heating device and heated according to one embodiment of the present disclosure.

[0024] Figure 13a is a drawing showing the relationship between the coil windings and magnetic flux.

[0025] FIG. 13b is a drawing showing a small cooking vessel placed on the working coil of an induction heating device according to one embodiment of the present disclosure.

[0026] FIG. 13c is a drawing showing a large cooking vessel placed on the working coil of an induction heating device according to one embodiment of the present disclosure.

[0027] FIG. 13d is a drawing showing a cooking vessel misaligned on a burner of an induction heating device according to one embodiment of the present disclosure.

[0028] FIG. 14 is a graph showing the phase of voltage and current of an operating coil according to one embodiment of the present disclosure.

[0029] FIG. 15 is a drawing showing an operation of removing noise through asymmetric control in an induction heating device according to one embodiment of the present disclosure.

[0030] Fig. 16 is a flowchart for performing asymmetric control in an induction heating device according to one embodiment of the present disclosure.

[0031] Fig. 17 is a block diagram of an induction heating device according to one embodiment of the present disclosure.

[0032] The terms used in this disclosure will be briefly explained, and one embodiment of the present disclosure will be specifically described.

[0033] The terms used in this disclosure are selected from widely used, current terms, taking into account the functions of one embodiment of the disclosure. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the description of the relevant embodiments of the disclosure. Therefore, the terms used in this disclosure should not be defined simply as names of terms, but rather based on the meanings of the terms and the overall content of the disclosure.

[0034] In this disclosure, the expression “at least one of a, b or c” may refer to “a”, “b”, “c”, “a and b”, “a and c”, “b and c”, “all of a, b and c”, or variations thereof.

[0035] Throughout this disclosure, when a part is said to "include" a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated. Furthermore, terms such as "part," "module," etc., used in this disclosure refer to a unit that processes at least one function or operation, and "part" and "module" may be implemented as hardware or software, or as a combination of hardware and software.

[0036] Below, with reference to the attached drawings, embodiments of the present disclosure are described in detail so that those skilled in the art can easily implement the present disclosure. However, one embodiment of the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in the drawings, parts irrelevant to the description are omitted to clearly describe one embodiment of the present disclosure, and similar parts are designated with similar drawing reference numerals throughout the present disclosure.

[0037] Induction heating devices can have multiple burners, and when multiple types of containers are placed on them, noise can be generated due to interference between the operating frequencies of each burner. This noise can cause auditory discomfort to users of the device, and therefore needs to be reduced.

[0038] Therefore, according to one embodiment of the present disclosure, there is an advantage in that when cooking is performed in multiple burners in an induction heating device including multiple burners, noise resulting from a difference in operating frequency of each burner can be reduced.

[0039] FIG. 1A and FIG. 1B are drawings for explaining an induction heating device according to one embodiment of the present disclosure.

[0040] Referring to FIGS. 1A and 1B, an induction heating device (2000) according to an embodiment of the present disclosure may include a plurality of burners (201, 202, 203). In FIG. 1B, the plurality of burners (201, 202, 203) have a circular shape, and thus may be referred to as a first circular burner (201), a second circular burner (202), and a third circular burner (203), respectively, and the first circular burner (201) may also be simply referred to as a first burner (201). Hereinafter, the induction heating device (2000) may be expressed as an induction cooking device, an induction heating device, or simply a heating device. Not all of the components illustrated in FIG. 1 are essential components. The induction heating device (2000) may be implemented with more components than the illustrated components, or may be implemented with fewer components.

[0041] The cooking vessel (101) may be a device for heating the contents inside the cooking vessel (101). The contents inside the cooking vessel (101) may be liquids such as water, tea, coffee, soup, juice, wine, oil, etc., or solids such as butter, meat, vegetables, bread, rice, etc., but are not limited thereto.

[0042] According to one embodiment of the present disclosure, the cooking vessel (101) can be powered wirelessly from an induction heating device (2000) using electromagnetic induction. Therefore, the cooking vessel (101) according to one embodiment of the present disclosure may not include a power cord connected to a power outlet.

[0043] According to one embodiment of the present disclosure, the type of cooking vessel (101) that wirelessly receives power from an induction heating device (2000) may vary. The cooking vessel (101) may be a general induction heating (IH) vessel (hereinafter, IH vessel) containing a magnetic material. The cooking vessel (101) may have a magnetic field induced in the vessel (IH metal) itself.

[0044] The cooking vessel (101) may be a general IH vessel, such as a pot, a frying pan, or a steamer. The cooking vessel (101) may include a cooker device. The cooker device may be a device into which a general IH vessel may be inserted or removed. In one embodiment, the cooker device may be a device capable of automatically cooking contents according to a recipe. The cooker device may be referred to as a pot, a rice cooker, or a steamer depending on its use. For example, if an inner pot for cooking rice is inserted into the cooker device, the cooker device may be referred to as a rice cooker. Hereinafter, the cooker device may be defined as a smart pot (or smart pot).

[0045] According to one embodiment of the present disclosure, when the cooking vessel (101) includes a communication interface, the cooking vessel (101) can communicate with the induction heating device (2000). The communication interface may include a short-range communication unit, a long-range communication unit, etc. The short-range wireless communication interface may include, but is not limited to, a Bluetooth communication unit, a BLE (Bluetooth Low Energy) communication unit, a near field communication interface (NFC), a WLAN (Wi-Fi) communication unit, a Zigbee communication unit, an IrDA (Infrared Data Association) communication unit, a WFD (Wi-Fi Direct) communication unit, an UWB (ultra wideband) communication unit, an ANT+ communication unit, etc. When the cooking appliance is remotely controlled by a server device (not shown) in an IoT (Internet of Things) environment, the long-range communication unit may be used to communicate with a server device. The telecommunications unit may include the Internet, a computer network (e.g., a LAN or WAN), and a mobile communication unit. The mobile communication unit may include, but is not limited to, a 3G module, a 4G module, a 5G module, an LTE module, an NB-IoT module, an LTE-M module, and the like.

[0046] According to one embodiment of the present disclosure, the cooking vessel (101) can transmit information to a server device (not shown) via the induction heating device (2000). For example, the cooking vessel (101) can transmit information obtained from the cooking vessel (101) (e.g., temperature information of the contents, etc.) to the induction heating device (2000) via short-range wireless communication (e.g., Bluetooth, BLE, etc.). At this time, the induction heating device (2000) can transmit the information obtained from the cooking vessel (101) to the server device by connecting to the server device using a WLAN (Wi-Fi) communication unit or a long-distance communication unit (e.g., the Internet). Meanwhile, the server device can provide the information obtained from the cooking vessel (101) received from the induction heating device (2000) to a user via a mobile terminal (not shown) connected to the server device. According to another embodiment of the present disclosure, the induction heating device (2000) may directly transmit information obtained from the cooking vessel (101) to the user's mobile terminal through D2D (device to device) communication (e.g., WFD (Wi-Fi Direct) communication or BLE communication).

[0047] Meanwhile, according to one embodiment of the present disclosure, the cooking vessel (101) may directly transmit information of the cooking vessel (101) (e.g., temperature information of the contents, etc.) to a server device via a communication interface (e.g., WLAN (Wi-Fi) communication unit). In addition, the cooking vessel (101) may directly transmit information obtained from the cooking vessel (101) (e.g., temperature information of the contents, etc.) to a user's mobile terminal via short-range wireless communication (e.g., Bluetooth, BLE, etc.) or D2D (device to device) communication (e.g., WFD (Wi-Fi Direct) communication).

[0048] An induction heating device (2000) according to one embodiment of the present disclosure may be a device that wirelessly transmits power to a heated object (e.g., a cooking vessel (101)) located on a top plate using electromagnetic induction. The induction heating device (2000) may include a working coil that generates a magnetic field for inductively heating the cooking vessel (101).

[0049] Generating a magnetic field by a working coil may mean transmitting power by utilizing a magnetic field induced in an IH metal (e.g., iron component) through self-induction. For example, an induction heating device (2000) may generate eddy currents in a cooking vessel (101) by flowing a current through the working coil to form a magnetic field.

[0050] According to one embodiment of the present disclosure, the induction heating device (2000) may include a plurality of operating coils. For example, if the top plate of the induction heating device (2000) includes a plurality of cooking zones, the induction heating device (2000) may include a plurality of operating coils corresponding to each of the plurality of cooking zones. In addition, the induction heating device (2000) may include a high-power cooking zone in which a first operating coil is provided on the inside and a second operating coil is provided on the outside. The high-power cooking zone may include three or more operating coils.

[0051] The top plate of the induction heating device (2000) according to one embodiment of the present disclosure may be made of reinforced glass, such as ceramic glass, to prevent it from being easily damaged. In addition, a guide mark may be provided on the top plate of the induction heating device (2000) to guide the cooking zone where the cooking vessel (101) should be positioned.

[0052] An induction heating device (2000) according to one embodiment of the present disclosure can detect that a cooking vessel (101) including a magnetic material is placed on the top plate. For example, the induction heating device (2000) can detect that the cooking vessel (101) is positioned on the top plate of the induction heating device (2000) based on a change in the current value (inductance) of the operating coil due to the approach of the cooking vessel (101).

[0053] According to one embodiment of the present disclosure, the induction heating device (2000) may include a communication interface for communicating with an external device or devices. For example, the induction heating device (2000) may communicate with a cooking vessel (101) or a server device through the communication interface. The communication interface may include a short-range communication unit (e.g., an NFC communication unit, a Bluetooth communication unit, a BLE communication unit, etc.), a mobile communication unit, etc.

[0054] According to one embodiment of the present disclosure, the induction heating device (2000) can detect a cooking vessel (101) positioned on the top plate through a communication interface. For example, the induction heating device (2000) can detect the cooking vessel (101) by receiving a packet transmitted from the cooking vessel (101) positioned on the top plate using short-range wireless communication (e.g., BLE mesh network, Bluetooth).

[0055] According to one embodiment of the present disclosure, the induction heating device (2000) can display information related to the cooking vessel (101) through a user interface. For example, when the cooking vessel (101) is detected, the induction heating device (2000) can display identification information of the cooking vessel (101) and location information of the cooking vessel (101) on a display unit included in the user interface (2400).

[0056] Referring to FIG. 1A, when a user places a cooking vessel (101) (e.g., a pot) on the top plate of an induction heating device (2000), the induction heating device (2000) can provide the user with identification information of the cooking vessel (101) (e.g., a pot) and location information of the cooking vessel (101) (e.g., located on the right burner) on a display (2411) as an output interface.

[0057] Referring to Fig. 1b, the induction heating device (2000) may include multiple burners (201, 202, 203), and thus may heat multiple cooking appliances simultaneously. When the induction heating device (2000) heats multiple cooking appliances simultaneously, the operating coils corresponding to each burner operate. However, if the operating frequencies of the operating coils are different from each other, they may interfere with each other, and noise in the audible range that can be heard by the user of the induction heating device (2000) may be generated. Therefore, there is a need to reduce the interference noise generated when heating multiple cooking appliances through multiple burners (201, 202, 203).

[0058] FIG. 2 is a cross-sectional view of a cooking vessel placed on an induction heating device according to one embodiment of the present disclosure.

[0059] Referring to FIG. 2, the cooking vessel (101) may include a magnetic material (e.g., IH metal) in which a magnetic field can be induced.

[0060] The cooking vessel (101) can be inductively heated by an induction heating device (2000) and can be a variety of containers including a magnetic material. Induction heating (IH) is a method of heating an IH metal using an electromagnetic induction phenomenon. For example, when an alternating current is supplied to the working coil (2120) of the induction heating device (2000), a magnetic field that varies with time is induced inside the working coil (2120). The magnetic field generated by the working coil (2120) passes through the bottom of the cooking vessel (101). When the magnetic field that varies with time passes through the IH metal (e.g., iron, steel, nickel, or various types of alloys) included in the bottom of the cooking vessel (101), a current that rotates around the magnetic field is generated in the IH metal. The rotating current is called an eddy current, and the phenomenon in which a current is induced by a magnetic field that varies with time is called an electromagnetic induction phenomenon. In the case of a cooking vessel (101), heat is generated at the bottom of the cooking vessel (101) by eddy current and resistance of IH metal (e.g., iron). The contents of the cooking vessel (101) can be heated by the heat generated at this time.

[0061] FIG. 3 is an inverter circuit diagram of an induction heating device for operating a plurality of operating coils according to one embodiment of the present disclosure.

[0062] Referring to Fig. 3, the input power source (10) is an AC power source, and the AC voltage generated by the AC power source is rectified by a rectifier circuit (2112) through an EMI filter (2111). The rectifier circuit (2112) is a device for converting the AC voltage into a DC voltage, and a diode may be used, but a thyristor or other type of switching device may also be used. Once converted into a DC voltage through the rectifier circuit (2112), the DC voltage may be smoothed by a DC link capacitor (2117_1, 2117_2).

[0063] In Fig. 3, two resonant circuits are illustrated assuming that there are two operating coils (2120_1, 2120_2), but if there are three craters and three operating coils are required, a resonant circuit can be added.

[0064] The DC voltage smoothed by the DC link capacitor (2117_1) generates a magnetic field in the first working coil (2120_1) by resonance between the first working coil (2120_1) and the resonant capacitor 1 (2118_1) and the resonant capacitor 2 (2118_2) through the switching operation of the two switch elements SW1 (2113_1) and SW2 (2113_2). The magnetic field generated in the first working coil (2120_1) generates an eddy current in the IH cooking vessel placed on the top of the first working coil (2120_1) to heat the contents of the cooking vessel. CT1 (2115_1) is a current sensing unit for detecting the current flowing in the first working coil (2120_1). In one embodiment, the first working coil (2120_1) may be a first working coil for a circular burner.

[0065] Likewise, the DC voltage smoothed by the DC link capacitor (2117_2) at the bottom generates a magnetic field in the second operating coil (2120_2) by resonance between the second operating coil (2120_2) and the resonant capacitor 3 (2118_3) and the resonant capacitor 4 (2118_4) through the switching operation of the two switch elements SW3 (2113_3) and SW4 (2113_4). The magnetic field generated in the second operating coil (2120_2) generates an eddy current in the IH cooking vessel placed on the top of the second operating coil (2120_2) to heat the contents of the cooking vessel. CT2 (2115_2) is a current sensing unit for detecting the current flowing in the second operating coil (2120_2). In one embodiment, the second operating coil (2120_1) may be a second operating coil for a square-shaped burner.

[0066] Fig. 4 is a switching diagram of an inverter circuit of an induction heating device according to one embodiment of the present disclosure.

[0067] In FIG. 4, SW1 (2113_1), SW2 (2113_2), SW3 (2113_3), and SW4 (2113_4) correspond to SW1 (2113_1), SW2 (2113_2), SW3 (2113_3), and SW4 (2113_4) in the circuit diagram according to FIG. 3, respectively.

[0068] Referring to Fig. 4, the on-off of SW1 (2113_1) and SW2 (2113_2) is repeated at a constant frequency (f1), and the on-duty of each of SW1 (2113_1) and SW2 (2113_2) is the same. Similarly, the on-off of SW3 (2113_3) and SW4 (2113_4) is repeated at a constant frequency (f2), and the on-duty of each of SW1 (2113_1) and SW2 (2113_2) is the same. The fact that the switching frequencies of SW1 (2113_1), SW2 (2113_2) and SW3 (2113_3), SW4 (2113_4) are different means that the output from the first operating coil (2120_1) where resonance occurs due to the switching of SW1 (2113_1), SW2 (2113_2) and the output from the second operating coil (2120_2) where resonance occurs due to the switching of SW3 (2113_3), SW4 (2113_4) are different. Therefore, when the burner corresponding to the first working coil (2120_1) is the first burner (201) of FIG. 1 and the burner corresponding to the second working coil (2120_2) is the second burner (203) of FIG. 1, the difference in output between the first working coil (2120_1) and the second working coil (2120_2) means that the outputs at the first burner (201) and the second burner (203) are different from each other. In actual cooking, there are frequent cases where cooking must be done simultaneously in the first burner (201) and the second burner (203) and cooking must be done with different outputs.

[0069] In Fig. 4, it can be confirmed that the switching frequencies of SW3 (2113_3) and SW4 (2113_4) are higher than the switching frequencies of SW1 (2113_1) and SW2 (2113_2). When the switching frequencies of SW1 (2113_1) and SW2 (2113_2) are f1 and the switching frequencies of SW3 (2113_3) and SW4 (2113_4) are f2, Fig. 5 illustrates the waveforms of the resonant currents detected in each of the first operating coil (2120_1) and the second operating coil (2120_2).

[0070] FIG. 5 is a waveform diagram of a resonant current detected in a plurality of operating coils according to one embodiment of the present disclosure.

[0071] Referring to FIG. 5, waveform diagram 501 is a waveform diagram of a resonant current detected in the first operating coil (2120_1), and the frequency (resonant frequency or operating frequency) of the resonant current is f1. Waveform diagram 503 is a waveform diagram of a resonant current detected in the second operating coil (2120_2), and the frequency (resonant frequency or operating frequency) of the resonant current is f2.

[0072] If the resonant frequency f1 of the first working coil (2120_1) and the resonant frequency f2 of the second working coil (2120_2) are different, interference noise due to a third frequency corresponding to the difference between the two frequencies (f1- f2) is generated, as shown in 505 of FIG. 5. If the difference between the two frequencies |f1- f2| falls within the audible band, the user of the induction heating device (2000) perceives the noise. The perceived noise may cause auditory discomfort to the user. Therefore, it is necessary to reduce the interference noise generated between the working coils (or between the burners).

[0073] FIG. 6a is a diagram showing asymmetric control switching in an inverter circuit of an induction heating device according to one embodiment of the present disclosure.

[0074] Referring to FIG. 6a, at the top (610), as seen in the previous FIG. 4, the on-off of SW1 (2113_1) and SW2 (2113_2) is repeated at a constant frequency (f1), and the on-duty of each of SW1 (2113_1) and SW2 (2113_2) is the same. Similarly, the on-off of SW3 (2113_3) and SW4 (2113_4) is repeated at a constant frequency (f2), and the on-duty of each of SW1 (2113_1) and SW2 (2113_2) is the same. The switching frequency f2 of SW3 (2113_3) and SW4 (2113_4) is higher than the switching frequency f1 of SW1 (2113_1) and SW2 (2113_2), and if a difference in resonant frequency (operating frequency) occurs in this way, interference noise may occur. According to one embodiment, in order to eliminate interference noise, so-called 'asymmetric control' may be performed by making the switching frequency of SW3 (2113_3) and SW4 (2113_4) f1 while making the on-duty of SW4 (2113_4) different from that of SW3 (2113_3), as shown in the lower part (620) of Fig. 6a. If the switching control that makes the on-duties of SW3 (2113_3) and SW4 (2113_4) different from each other is called 'asymmetric control', the switching control that makes the on-duties of SW3 (2113_3) and SW4 (2113_4) the same may be called 'symmetric control'.

[0075] In one embodiment, when the switching frequency of SW3 (2113_3) and SW4 (2113_4) is lowered to f1 as in 620, the output from the burner increases compared to when switching to f2. However, when so-called 'asymmetric control' is performed in which the on-duty of SW4 (2113_4) is made different from the on-duty of SW3 (2113_3), the output decreases compared to 'symmetric control'. Therefore, the induction heating device (2000) can make the output by the second working coil (2120_2) in the case of symmetric control the same as the output of the second working coil (2120_2) in the case of asymmetric control while setting the switching frequency of SW3 (2113_3) and SW4 (2113_4) to f1. In other words, by changing the switching frequency of SW3 (2113_3) and SW4 (2113_4) to f1 and appropriately adjusting the on-duty of SW3 (2113_3) and SW4 (2113_4), the output of the second operating coil (2120_2) can be controlled to be the same as the output by the second operating coil (2120_2) in the case of symmetrical control with the switching frequency of SW3 (2113_3) and SW4 (2113_4) as f2. Such symmetrical control and asymmetrical control of the switching elements SW3 (2113_3) and SW4 (2113_4) can be performed by the processor of the induction heating device (2000).

[0076] In one embodiment, the induction heating device (2000) can match the frequency of the working coil operating at a high switching frequency (or the operating frequency of the working coil) to the frequency of the working coil operating at a relatively low switching frequency (or the operating frequency of the working coil) to perform asymmetric control.

[0077] FIG. 6b is an asymmetric control flowchart of an induction heating device according to one embodiment of the present disclosure.

[0078] Figure 6b is a flowchart showing the asymmetric control performed by the induction heating device (2000) in the preceding Figure 6a.

[0079] First, in step S601, the induction heating device (2000) initiates a heating operation in the first crater (201) and the second crater (204).

[0080] In step S603, the induction heating device (2000) can determine a first operating frequency in the first crater (201) and a second operating frequency in the second crater (203) according to a start command of the second crater (203). When the output in the first crater (201) is determined, a reference frequency for PWM (pulse width modulation) switching of SW1 (2113_1) and SW2 (2113_2) according to the output is determined, so that the induction heating device (2000) can detect the first operating frequency according to the determined reference frequency. Similarly, when the output is determined by the user in the second crater (203), a second operating frequency in the second operating coil (2120_2) of the second crater (203) corresponding to the determined output can be determined. The second operating frequency can be said to be the switching frequency of SW3 (2113_3) and SW4 (2113_4).

[0081] In step S605, if the first operating frequency and the second operating frequency are different from each other, the induction heating device (2000) matches the second operating frequency in the second operating coil (2120_2) corresponding to the second crater (203) with the first operating frequency. By matching the second operating frequency with the first operating frequency, interference noise that may occur between the first operating frequency and the second operating frequency can be eliminated.

[0082] Since the output from the second crater (203) may vary as the second operating frequency matches the first operating frequency, in order to compensate for this, according to one embodiment, the on-duty of the switching SW3 (2113_3) and SW4 (2113_4) for generating resonance in the second operating coil (2120_2) may be changed. In this case, in one embodiment, the induction heating device (2000) may keep the on-duty of SW3 (2113_3) the same as before, and only change the on-duty of SW4 (2113_4). Conversely, the induction heating device (2000) may keep the on-duty of SW4 (2113_4) the same as before, and only change the on-duty of SW3 (2113_3). In one embodiment, the induction heating device (2000) can control the output from the second operating coil (2120_2) to be the same as the output when operating at the second operating frequency by changing both the on-duty of SW3 (2113_3) and the on-duty of SW4 (2113_4).

[0083] FIGS. 7A and 7B illustrate an induction heating device using a square working coil according to one embodiment of the present disclosure.

[0084] Referring to FIGS. 7A and 7B, an induction heating device (2000) according to one embodiment of the present disclosure may include a circular first burner (201) operated by a first operating coil and a square second burner (204) operated by a second operating coil. The first operating coil may be a circular operating coil, and the second operating coil may be a square or nearly square-shaped operating coil. The square of the second burner (204) may be rectangular, and the second operating coil on the bottom surface of the square second burner (204) may include a plurality of rectangular or elongated oval operating coils.

[0085] Using a second working coil for the square second burner (204) in an induction heating device (2000) has the advantage of eliminating a non-cooking zone, for example, when placing a square pot. In addition, no matter where the user of the induction heating device (2000) places the cooking vessel on the square second burner (204), the induction heating device (2000) can recognize the cooking vessel and operate at least some of the corresponding plurality of working coils necessary for heating the cooking vessel, thereby heating the contents of the cooking vessel.

[0086] FIG. 8 is a drawing showing an induction heating device according to one embodiment of the present disclosure together with a working coil.

[0087] FIG. 8 is a drawing showing the working coils inside the induction heating device (2000) wound together with the outer shape of the induction heating device (2000), although it is not actually visible from the outside. As shown in FIG. 8, according to one embodiment, four square working coils (2120_3, 2120_4, 2120_5, 2120_6) corresponding to the second square crater (204) in the induction heating device (2000) are wound sequentially from the top of the induction heating device (2000). The four square working coils (2120_3, 2120_4, 2120_5, 2120_6) may be second working coils. Of course, this is only one example, and the number of second operating coils (2120_3, 2120_4, 2120_5, 2120_6) corresponding to the second crater (204) of the square may be four or more, or may be less than four.

[0088] On the right side of the induction heating device (2000), as previously shown in FIG. 1, a circular operating coil corresponding to the first circular crater (201) is wound to fit the first crater (201) as a first operating coil (2120_1). Hereinafter, in the present disclosure, the first operating coil (2120_1) may also be referred to as a circular operating coil.

[0089] FIG. 9 is a graph showing the inductance of a square operating coil and a circular operating coil according to one embodiment of the present disclosure.

[0090] For convenience of explanation, the following description will be given as an example of a case where two lower square operating coils (2120_5, 2120_6) among the second operating coils (2120_3, 2120_4, 2120_5, 2120_6), which are square operating coils, operate and a circular operating coil (2120_1) operates at the same time. Although the description focuses on the lower square operating coils (2120_5, 2120_6), the embodiments below can be equally applied to the upper square operating coils (2120_3, 2120_4) or the middle square operating coils (2120_4, 2120_5). In FIGS. 9 and 10A only, the lower square operating coils (2120_5, 2120_6) are referred to as the second operating coils, and the circular operating coil (2120_1) is referred to as the first operating coil.

[0091] The second operating coils (2120_5, 2120_6) should be designed to have a high inductance value due to their shape, and the first operating coil (2120_1) is designed to have a relatively low inductance value. This is because when a cooking vessel is placed on the burner in the induction heating device (2000), the equivalent inductance value of the operating coil corresponding to the burner decreases, and when the equivalent inductance value of the operating coil decreases, the equivalent resistance value of the operating coil increases. At this time, the operating coil corresponding to the square burner has a relatively low coupling with the cooking vessel compared to the operating coil corresponding to the circular burner. Therefore, even if the inductance values ​​of the operating coil corresponding to the circular burner and the operating coil corresponding to the square burner are the same when no cooking vessel is placed, the inductance value of the operating coil corresponding to the circular burner becomes smaller than the inductance value of the operating coil corresponding to the square burner when the cooking vessel is placed on the burner. An example of this is shown in Table 1 below.

[0092] Circular burner operating coilSquare burner operating coilCircular inductance value of the operating coil80uHCircular inductance value of the operating coil80uHInductance value of the operating coil when the cooking vessel is placed40uHInductance value of the operating coil when the cooking vessel is placed

[0093] Here, as in the case of the circular burner, the more the equivalent inductance value of the working coil decreases, the greater the equivalent resistance value of the working coil becomes. However, in the case of the square burner, the amount by which the inductance value of the working coil decreases when the cooking vessel is placed is small, so the equivalent resistance value of the working coil does not increase relatively. Accordingly, in the induction heating device (2000), the same output (P = I 2 In order to obtain the equivalent resistance (R), the current value in the square crater must be increased. Therefore, in order to increase the equivalent resistance value, the inductance of the square crater must be relatively increased.

[0094] Therefore, referring to FIG. 9, it can be confirmed through the graph that the inductance (910) of the lower second operating coil (2120_5, 2120_6) has a larger value than the inductance (920) of the first operating coil (2120_1). The fact that the inductance of the second operating coil (2120_5, 2120_6) is higher than the inductance of the first operating coil (2120_1) means that the resonant frequency at which the second operating coil (2120_5, 2120_6) resonates with the resonant capacitor is lower than the resonant frequency at which the first operating coil (2120_1) resonates with the resonant capacitor. This is because the resonant frequency is derived by the following equation.

[0095] ... Mathematical formula (1)

[0096] Therefore, according to the above mathematical equation (1), the operating frequency (f2) at the maximum output of the second operating coil (2120_5, 2120_6) is smaller than the operating frequency (f1) at the maximum output of the first operating coil (2120_1).

[0097] FIG. 10A is a graph showing the resonant frequency of each working coil according to one embodiment of the present disclosure.

[0098] Fig. 10a is a graph showing the output according to the operating frequency of each crater (working coil) according to the above mathematical equation (1). As shown in Fig. 10a, it can be seen that the operating frequency (f2) at the maximum output by the second working coil (2120_5, 2120_6) is lower than the operating frequency (f1) at the maximum output by the first working coil (2120_1) which is circular. In Fig. 10a, the induction heating device (2000) can be controlled so that the maximum output of the second crater (204) having a square shape occurs, for example, at point f2 rather than point f'. In other words, the point at which the second operating coil (2120_5, 2120_6) can produce maximum output is f', but in this case, the induction heating device (2000) may become unstable, so the induction heating device (2000) is usually set to produce maximum output for each burner at point f2, which is slightly to the right of point f'.

[0099] According to Fig. 10a, when the second operating coil (2120_5, 2120_6) performs a heating operation, the operating frequency has a value smaller than the operating frequency of the first operating coil (2120_1).

[0100] According to one embodiment of the present disclosure, when the second operating coil (2120_5, 2120_6) performs a heating operation, the operating frequency has a value smaller than the operating frequency of the first operating coil (2120_1). If the difference (f1-f2) between the operating frequency of the first operating coil (2120_1) and the operating frequency of the second operating coil (2120_5, 2120_6) is less than 5 kHz, interference noise may occur during the heating operation in the two burners. Therefore, in one embodiment, when designing the inductance of the second operating coil (2120_5, 2120_6) and the inductance of the first operating coil (2120_1), the operating coils - the inductance of the operating coils - can be designed such that the difference (f1-f2) between the operating frequencies when the second operating coils (2120_5, 2120_6) perform a heating operation and the operating frequencies when the first operating coil (2120_1) performs a heating operation is greater than 5 kHz. Although a frequency difference of 5 kHz may not normally cause auditory discomfort to a user, the two operating coils - the inductance of the operating coils - can be designed such that the difference (f1-f2) between the two operating frequencies is preferably between 5 and 10 kHz, or greater than 10 kHz, so that it is more difficult for the user to perceive interference noise.

[0101] FIG. 10b is a graph showing the resonant frequency of each working coil according to one embodiment of the present disclosure.

[0102] It can be seen that the difference in output by frequency band occurs for each crater as shown in Fig. 10a because the lower square operating coil (2120_5, 2120_6) usually has a larger inductance value than the circular operating coil (2120_1).

[0103] However, even in an induction heating device (2000) consisting of only circular burners as in Fig. 1, there may be differences in inductance values ​​for each burner. For example, even if the inductance of the first operating coil (2120_1) corresponding to the first burner (201) (the first circular burner (201)) is smaller than the inductance of the second operating coil (2120_2) corresponding to the second circular burner (202), a difference in output for each burner according to the frequency band as in Fig. 10b may occur.

[0104] As shown in FIG. 10b, it can be seen that the operating frequency (f2) at the maximum output by the second operating coil (2120_2) is lower than the operating frequency (f1) at the maximum output by the first operating coil (2120_1). In FIG. 10b, the induction heating device (2000) can be controlled so that the maximum output of the second circular crater (202) occurs, for example, at point f2 rather than point f'. In other words, although the point at which the second operating coil (2120_2) can produce the maximum output is f', in this case, the induction heating device (2000) may become unstable, so the induction heating device (2000) is usually set to produce the maximum output for each crater at point f2, which is slightly to the right of point f'.

[0105] According to FIG. 10b, when the second operating coil (2120_2) performs a heating operation, the operating frequency usually has a value smaller than the operating frequency of the first operating coil (2120_1).

[0106] If the inductance values ​​of the first operating coil (2120_1) and the second operating coil (2120_2) are not the same - or the difference is very small - or the difference between the inductance values ​​of the two operating coils is large, interference noise may occur when the two operating coils operate, as shown in Fig. 10b. Therefore, in order to eliminate this interference noise, when designing the inductance of the first operating coil (2120_1) and the inductance of the second operating coil (2120_2), the two operating coils - the inductances of the operating coils - can be designed such that the difference |f1-f2| between the operating frequency when the first operating coil (2120_1) performs a heating operation and the operating frequency when the second operating coil (2120_2) performs a heating operation is greater than 5 kHz. Although a frequency difference of 5 kHz may not cause any auditory discomfort to the average user, it is desirable to have a difference between the two operating frequencies |f1- f to make it more difficult for the user to perceive the noise. 2| The two working coils (2120_1, 2120_2) - the inductance of the two working coils - can also be designed to be between 5 and 10 kHz or greater than 10 kHz. In one embodiment, both the first burner heated by the first working coil (2120_1) and the second burner heated by the second working coil (2120_2) can be circular. In one embodiment, the first burner heated by the first working coil (2120_1) can be circular, and the second burner heated by the second working coil (2120_2) can be square.

[0107] FIG. 11 is a graph showing the frequency difference by crater according to one embodiment of the present disclosure.

[0108] Referring to Figure 11, the difference in operating frequency and the noise reduction method are explained.

[0109] As already explained through Fig. 5, noise may be generated depending on the difference in operating frequency for each burner in the induction heating device (2000). There are various factors that cause the difference in operating frequency for each burner, but the operating frequency may be different if the output set by the user for each burner is different. In addition, as examined in Figs. 10a and 10b, the operating frequency may be different if the inductance of the operating coil for each burner is different. In addition, the operating frequency may be different if the output set by the user for each burner is different and the inductance of the operating coil for each burner is also different. Fig. 11 is a diagram showing that the operating frequencies of two burners among the multiple burners of the induction heating device (2000) differ as f2 and f1 due to at least one of the above factors.

[0110] If the operating frequencies of two of the plurality of burners are different, f2 and f1, and the difference between the two operating frequencies |f1- f2| falls within the audible band, the user of the induction heating device (2000) will perceive noise and experience auditory discomfort. Therefore, in one embodiment, if the operating frequency difference |f1- f2| between two of the plurality of burners is 3 kHz or less as shown in FIG. 11, the induction heating device (2000) can control the output of the burner to be maintained the same as when it is operated at the operating frequency f1 by simultaneously performing asymmetric control to make the relatively high operating frequency f1 the operating frequency f2 (f1-> f2). Although it may vary depending on the case, the maximum value at which the frequency can be lowered by asymmetric control is generally about 3 kHz.

[0111] FIG. 12 is a drawing showing a cooking vessel being placed on an induction heating device and heated according to one embodiment of the present disclosure.

[0112] Referring to Fig. 12, the induction heating device (2000) has a square second crater (204) and a circular first crater (201).

[0113] The inductance of the lower square operating coils (2120_5, 2120_6) corresponding to the lower part of the second square crater (204) is usually larger than the inductance of the circular operating coil (2120_1) corresponding to the first crater (201). Therefore, when designing the inductances of the lower square operating coils (2120_5, 2120_6) and the circular operating coil (2120_1) in order to eliminate interference noise, it has already been described with reference to FIG. 10a that the two operating coils can be designed so that the difference (f1-f2) between the operating frequency when the lower square operating coils (2120_5, 2120_6) perform a heating operation and the operating frequency when the circular operating coil (2120_1) performs a heating operation is greater than a predetermined frequency value - for example, 5 kHz or more or 5 kHz to 10 kHz.

[0114] In addition, it has already been explained with reference to Fig. 10b that the two operating coils can be designed so that the operating frequency difference |f1- f2| between the first operating coil (2120_1) and the second operating coil (2120_2), which are both circular, is also greater than 5 kHz.

[0115] In Fig. 12, let us examine a case where the investment rate of a cooking vessel (102) placed on a second square burner (204) corresponding to a lower square operating coil (2120_5, 2120_6) is lower than the investment rate of a cooking vessel (101) placed on a first burner (201) corresponding to a first operating coil (2120_1).

[0116] A low investment rate in a cooking vessel means a higher inductance value as seen from the operating coil. For a more detailed examination of this, refer to Figures 13a to 13d and Figure 14.

[0117] Figure 13a is a drawing showing the relationship between the coil windings and magnetic flux.

[0118] Referring to Fig. 13a, when current flows through the coil (13), a magnetic flux is formed around it. Here, the inductance of the coil (13) is the inductance corresponding to the amount of magnetic flux flowing out as much as flowing in the coil (13). Therefore, a large inductance means that there are many magnetic force lines. At this time, when a magnetic material with permeability approaches the surroundings, the magnetic material absorbs these magnetic force lines, and the permeability is a value indicating how much magnetic flux can be absorbed. For example, the permeability of a small cooking utensil is lower than that of a relatively large cooking utensil, so it absorbs less magnetic flux. Absorbing less magnetic flux means that the inductance value is large. Conversely, a cooking utensil with a large permeability absorbs a lot of magnetic flux, so the inductance value is small.

[0119] FIG. 13b is a drawing showing a small cooking vessel placed on the working coil of an induction heating device according to one embodiment of the present disclosure.

[0120] FIG. 13c is a drawing showing a large cooking vessel placed on the working coil of an induction heating device according to one embodiment of the present disclosure.

[0121] A relatively large cooking vessel (105) absorbs more magnetic flux (magnetic lines of force) generated by the operating coil than a small cooking vessel (103). This is because the magnetic permeability of the large cooking vessel (105) is greater than that of the small cooking vessel (103). However, this is only an example, and if the magnetic material of the small cooking vessel (103) itself has a high magnetic permeability, the inductance value will be smaller even if the small cooking vessel (103) is small.

[0122] FIG. 13d is a drawing showing a cooking vessel misaligned on a burner of an induction heating device according to one embodiment of the present disclosure.

[0123] A misalignment of a cooking vessel on the burner of an induction heating device (2000) means that the center of the cooking vessel does not coincide with the center of the burner. It may also mean that a portion of the cooking vessel is asymmetrically placed beyond the circular boundary of the burner.

[0124] Apart from the permeability, the inductance value may also vary depending on the position where the cooking vessel is placed. According to FIG. 13d, even if a cooking vessel (105) with the same permeability is placed on the working coil (2120) - the burner corresponding to the working coil (2120), if it is not placed exactly on the burner but is misaligned, the permeability is lowered, which means that the inductance in the working coil of the burner increases. Accordingly, in FIG. 13d, compared to the case where the cooking vessel (105) is placed so as to match the shape of the working coil (2120) - the burner corresponding to the working coil (2120), since it is placed misaligned from the center of the working coil (2120), the inductance at this time becomes relatively larger than when it is placed so as to match the shape of the working coil (2120).

[0125] As shown in FIGS. 13a to 13d above, when the inductance is increased by the cooking vessel, the current is delayed further compared to the voltage applied to the operating coil (2120), so the phase difference between the voltage and current becomes wider. FIG. 14 shows this in a graph.

[0126] FIG. 14 is a graph showing the phase of voltage and current of an operating coil according to one embodiment of the present disclosure.

[0127] According to Fig. 14, the voltage (v) and current (i1, i2) of the working coil are shown. The induction heating device (2000) can detect the voltage and current of the working coil through a voltage sensor and a current sensor (CT), respectively, and the processor (2200) of the induction heating device (2000) can detect the phase difference (△1, △2) between the voltage and current based on the detected voltage and current.

[0128] If the permeability of the cooking vessel 1 placed on the burner is μ1, and the current of the working coil when the induction heating device (2000) heats the cooking vessel 1 is i1, and the permeability of the cooking vessel 2 is μ2 (μ1 > μ2), and the current of the working coil when the induction heating device (2000) heats the cooking vessel 2 is i2, then when the induction heating device (2000) heats the cooking vessel 2, the inductance is greater than when the cooking vessel 1 is heated due to the permeability, so the current (i2) delay (△2) of the working coil that heats the cooking vessel 2 may be greater than the current (i1) delay (△1) with respect to the voltage (v) when heating the cooking vessel 1. The current delay (△1, △2) can be said to be the phase difference between the voltage and the current. Therefore, the actual output of the burner becomes V*I*cosθ (V is the rms value of v, I is the rms value of i1, i2). At this time, the output of V*I*cos(△1) is generated in cooking vessel 1, and the output of V*I*cos(△2) is generated in cooking vessel 2, and V*I*cos(△1) > V*I*cos(△2). In order to maintain the output of cooking vessel 2, which has a relatively large inductance, the current must be increased instead of the fixed voltage value. To increase the current, the operating frequency of the working coil must be lowered. If the operating frequency continues to be lowered, the current will increase, but there is a limit to lowering the operating frequency because it cannot be increased higher than the current limit according to the specifications of the working coil or the induction heating device (2000). Therefore, for cooking vessels with low permeability, it is necessary to increase the operating frequency overall. For example, in the case of a high permeability such as cookware 1, the operating coil can be operated at an operating frequency of 25 kHz, but in the case of a cookware with a low permeability, it is necessary to operate it at a relatively high operating frequency, for example, 27 kHz.When using a cookware with such a low investment rate, noise may occur again because the operating frequency is changed while the difference between the operating frequencies of the two burners is more than 5 kHz due to the inductance design to eliminate interference noise.

[0129] In other words, let's say that the inductance of the lower square operating coils (2120_5, 2120_6) is designed so that the operating frequency of the lower square operating coils (2120_5, 2120_6) operates at f2 = 25 kHz, and the first operating coil (2120_1) is designed to operate at f1 = 31 kHz. At this time, if a cooking vessel with low permeability is placed on the lower square operating coils (2120_5, 2120_6), the operating frequency of the lower square operating coils (2120_5, 2120_6) becomes 27 kHz, and the frequency difference between f2 and f1 becomes 4 kHz, which may cause interference noise. Therefore, a method for reducing or eliminating this interference noise is needed.

[0130] In one embodiment, the processor (2200) determines that the permeability of the cooking vessel 2 is lower than the permeability of the cooking vessel 1 - the predetermined permeability - as the phase difference between the voltage and current of the operating coil - △2 in the previous example - becomes greater than a predetermined phase difference value (△1) corresponding to a normal cooking vessel - a cooking vessel having a relatively high permeability - and based on this determination, the processor (2200) can perform asymmetric control.

[0131] FIG. 15 is a drawing showing an operation of removing noise through asymmetric control in an induction heating device according to one embodiment of the present disclosure.

[0132] According to FIG. 15, the 1501 graph according to one embodiment of the present disclosure is a case where the cooking vessel is normal (a large cooking vessel with a relatively high investment rate), and when such a cooking vessel is used, the inductance of the lower square operating coils (2120_5, 2120_6) is designed so that the operating frequency of the lower square operating coils (2120_5, 2120_6) operates at f2 = 25 kHz, and the first operating coil (2120_1) is designed so that the operating frequency of the lower square operating coils (2120_5, 2120_6) operates at f1 = 31 kHz, so that the two operating frequencies differ by more than 5 kHz and noise is not generated.

[0133] Of course, this is only one example, and as previously explained, a second operating coil (2120_2) may be used instead of the lower square operating coils (2120_5, 2120_6).

[0134] However, in the 1503 graph according to one embodiment of the present disclosure, a cooking vessel with a low investment rate is placed on the lower square working coil (2120_5, 2120_6), and therefore, the operating frequency of the lower square working coil (2120_5, 2120_6) is raised to f2 = 27 kHz. In order to make the operating frequency f2 of the raised lower square working coil (2120_5, 2120_6) (f1-f2) > 5 kHz, the processor (2200) of the induction heating device (2000) performs asymmetric control on the lower square working coil (2120_5, 2120_6) to lower the operating frequency f2 to, for example, 25 kHz. By this method, interference noise that may occur in multiple burners of the induction heating device (2000) can be eliminated.

[0135] Fig. 16 is a flowchart for performing asymmetric control in an induction heating device according to one embodiment of the present disclosure.

[0136] In step S1601, the induction heating device (2000) detects a first operating frequency operating in the first crater. In one embodiment, the first crater may be a circular crater.

[0137] In step S1603, the induction heating device (2000) detects a second operating frequency operating in the second crater. In one embodiment, the second crater may be a square crater - a rectangular crater - or a circular crater. The inductance value of the operating coil corresponding to the first crater and the inductance value of the operating coil corresponding to the second crater may be determined such that the second operating frequency in the operating coil corresponding to the second crater and the first operating frequency in the operating coil corresponding to the first crater differ by a predetermined frequency - for example, 5 kHz - or more.

[0138] In step S1605, the induction heating device (2000) detects that the difference between the first operating frequency and the second operating frequency is within a predetermined frequency. The inductance value of the operating coil corresponding to the first burner and the inductance value of the operating coil corresponding to the second burner may be determined so that the second operating frequency in the operating coil corresponding to the second burner and the first operating frequency in the operating coil corresponding to the first burner differ by a predetermined frequency - for example, 5 kHz - or more. However, in one embodiment, the second operating frequency of the second burner may increase due to a cooking vessel with a low permeability being placed on the second burner. As a result, the difference between the first operating frequency and the second operating frequency may become within a predetermined frequency - for example, 5 kHz.

[0139] In step S1607, the induction heating device (2000) can reduce the second operating frequency by performing asymmetric control to make the duty ratio of the switching element that switches for the operating coil of the second crater corresponding to the second operating frequency (<the first operating frequency) different from each other. As a result, the difference between the first operating frequency and the second operating frequency can be made to be a difference of a predetermined frequency - for example, 5 kHz - or more again.

[0140] Fig. 17 is a block diagram of an induction heating device according to one embodiment of the present disclosure.

[0141] As illustrated in FIG. 17, an induction heating device (2000) according to one embodiment of the present disclosure may include an induction heating unit (2100), a processor (2200), a communication interface (2300), a user interface (2400), and a memory (2500).

[0142] Below, we will look at the above components in turn.

[0143] The induction heating unit (2100) may include, but is not limited to, a driving unit (2110) and an operating coil (2120). The driving unit (2110) may receive power from an input power source (10) and supply current to the operating coil (2120) according to a driving control signal of a processor (2200). The driving unit (2110) may include, but is not limited to, an EMI (Electro Magnetic Interference) filter (2111), a rectifier circuit (2112), an inverter (2113), a distribution circuit (2114), and a current detection unit (2115). According to one embodiment of the present disclosure, the driving unit (2110) may be broadly referred to as an inverter. When the driving unit (2110) is referred to as an inverter, the inverter (2113) of FIG. 17 may only refer to a switching element that performs a switching operation to supply current to the operating coil (2120).

[0144] The EMI filter (2111) blocks high-frequency noise contained in the AC power supplied from the input power source (10) and can pass AC voltage and AC current of a predetermined frequency (e.g., 50 Hz or 60 Hz). A fuse and a relay for blocking overcurrent may be provided between the EMI filter (2111) and the input power source (10). The AC power from which high-frequency noise has been blocked by the EMI filter (2111) is supplied to the rectifier circuit (2112).

[0145] The rectifier circuit (2112) can convert AC power into DC power. For example, the rectifier circuit (2112) can convert AC voltage, whose magnitude and polarity (positive voltage or negative voltage) change over time, into DC voltage, whose magnitude and polarity are constant, and can convert AC current, whose magnitude and direction (positive current or negative current) change over time, into DC current, whose polarity does not change over time. The rectifier circuit (2112) can include a bridge diode as a rectification element. For example, the rectifier circuit (2112) can include four diodes. The bridge diode can convert AC voltage, whose polarity changes over time, into a positive voltage, whose polarity is constant, and can convert AC current, whose direction changes over time, into a positive current, whose direction is constant. The rectifier circuit (2112) can be connected to a DC link capacitor that rectifies the rectified DC voltage.

[0146] The inverter (2113) may include a switching circuit that supplies or blocks driving current to the operating coil (2120) and a resonant capacitor that causes resonance with the operating coil (2120). The switching circuit may include two switches for each burner. For example, the switching circuit may include a first switch (SW1, 2113_1) and a second switch (SW2, 2113_2) for the first burner (201). In addition, when the induction heating device (2000) includes a second burner (202), it may include a third switch (SW3, 2113_3) and a fourth switch (SW4, 2113_4) corresponding to the second burner (202). The first switch (SW1, 2113_1) and the second switch (SW2, 2113_2) may be connected in series between the plus line and the minus line output from the rectifier circuit (2112). The first switch (SW, 2113_1) and the second switch (SW2, 2113_2) may be turned on or off according to a driving control signal of the processor (2200). In one embodiment, the induction heating device (2000) may include a separate driving processor in addition to the processor (2200) to generate the driving control signal.

[0147] The inverter (2113) can control the current supplied to the operating coil (2120). For example, the magnitude and direction of the current flowing in the first operating coil (2120_1) can change depending on the turning on / off of the first switch (SW1, 2113_1) and the second switch (SW2, 2113_2) included in the inverter (2113). In addition, the magnitude and direction of the current flowing in the second operating coil (2120_2) can change depending on the turning on / off of the third switch (SW3, 2113_3) and the fourth switch (SW4, 2113_4) included in the inverter (2113). In this case, an alternating current can be supplied to the first operating coil (2120_1) and the second operating coil (2120_2). In addition, the square operating coils (2120_3 to 2120_6) can also be supplied with alternating current by the inverter (21130). A sine wave-shaped alternating current is supplied to the first operating coil (2120_1) according to the switching operation of the first switch (SW1, 2113_1) and the second switch (2113_2). In addition, the longer the switching cycle of the first switch (SW1, 2113_1) and the second switch (SW2, 2113_2) (for example, the smaller the switching frequency of the first switch (SW1, 2113_1) and the second switch (SW2, 2113_2)), the greater the current supplied to the first operating coil (2120_1), and the stronger the magnetic field output by the first operating coil (2120_1) (of the induction heating device (2000)). Output) can be increased. Although the above description mainly focuses on the first switch (SW1, 2113_1), the second switch (2113_2) and the first operating coil (2120_1), the operation of the second operating coil (2120_2) and the square operating coils (2120_3 to 2120_6) can also be performed in the same manner.

[0148] When the induction heating device (2000) includes a plurality of operating coils (2120) - a first operating coil (2120_1), a second operating coil (2120_2), and rectangular operating coils (2120_3 to 2120_6) as in FIG. 17, the driving unit (2110) may include a distribution circuit (2114). The distribution circuit (2114) may include a plurality of switches that pass or block current supplied to the plurality of operating coils (2120), and the plurality of switches may be turned on or off according to a distribution control signal of the processor (2200).

[0149] The current detection unit (2115) may include CT1 (2115_1) and CT2 (2115_2) as current sensors that measure the current output from the inverter (2113) and flowing through the operating coil (2120). The current sensor may transmit an electrical signal corresponding to the measured current value to the processor (2200). Although not shown, the induction heating device (2000) may further include a voltage detection unit that senses the voltage of the operating coil (2120) in addition to the current detection unit (2115).

[0150] The processor (2200) can determine the switching frequency (turn-on / turn-off frequency) of the switching circuit included in the inverter (2113) based on the output strength (power level) of the induction heating device (2000). The processor (2200) can generate a driving control signal for turning the switching circuit on / off according to the determined switching frequency. The induction heating device (2000) can include a driving processor separate from the processor (2200) to control the operation of the induction heating unit (2100) during the operation of the processor (2200).

[0151] The actuation coil (2120) can generate a magnetic field for heating the cooking vessel (101). For example, when a driving current is supplied to the actuation coil (2120), a magnetic field can be induced around the actuation coil (2120). When a current whose magnitude and direction change over time, i.e., an alternating current, is supplied to the actuation coil (2120), a magnetic field whose magnitude and direction change over time can be induced around the actuation coil (2120). The magnetic field around the actuation coil (2120) can pass through the top plate made of tempered glass and reach the cooking vessel (101) placed on the top plate. Due to the magnetic field whose magnitude and direction change over time, an eddy current that rotates around the magnetic field can be generated in the cooking vessel (101), and due to the eddy current, electric resistance heat can be generated in the cooking vessel (101). Electric resistance heat is heat generated in a resistor when current flows through the resistor, and is also called Joule heat. The cooking vessel (101) is heated by electric resistance heat, and the contents inside the cooking vessel (101) can be heated.

[0152] The processor (2200) controls the overall operation of the induction heating device (2000). The processor (2200) is a hardware device that controls the overall operation of the induction heating device (2000). The processor (2200) may be a hardware device (chip) including an integrated circuit in which electrical circuits are integrated. The processor (2200) may control the induction heating unit (2100), the communication interface (2300), the user interface (2400), and the memory (2500) by executing programs stored in the memory (2500). The induction heating device (2000) may include at least one processor. For example, the processor (2200) may be one or multiple. In addition, when multiple processors are provided, operations by the processor in the present disclosure may be performed by any one of the multiple processors. The induction heating device (2000) may include only a main processor, or may include a main processor and at least one sub-processor.

[0153] According to one embodiment of the present disclosure, the induction heating device (2000) may be equipped with an artificial intelligence (AI) processor. The AI ​​processor may be manufactured in the form of a dedicated hardware chip for artificial intelligence (AI), or may be manufactured as part of an existing general-purpose processor (e.g., CPU or application processor) or a graphics-only processor (e.g., GPU) and equipped in the induction heating device (2000).

[0154] The processor (2200) can establish a short-range wireless communication channel (e.g., a BLE communication channel) with the cooking vessel (101) through the communication interface (2300) when the unique identification information of the cooking vessel (101) is stored in the memory (2500).

[0155] The processor (2200) can perform asymmetric control between a plurality of operating coils (2120). In one embodiment, when the operating frequency of the first operating coil (2120_1) is f1 and the operating frequency of the second operating coil (2120_2) is f2 (f1> f2), the processor (2200) can control the operating frequency of the first operating coil (2120_1) to be f1=f2. At the same time, the processor (2200) can perform asymmetric control so that even when the operating frequency of the second operating coil (2120_2) is f1, the output from the crater corresponding to the second operating coil (2120_2) when the operating frequency of the second operating coil (2120_2) is f2 is the same as the output when the operating frequency of the second operating coil (2120_2) is f1. The processor (2200) can perform asymmetric control by setting the turn-on / turn-off duty of the third switch (SW3, 2113_3) and the fourth switch (SW4, 2113_4) to be different from each other so that an alternating current flows through the second operating coil (2120_2).

[0156] Let's say that the operating frequency of the square operating coils (2120_3 to 2130_6) corresponding to the square crater among the plurality of operating coils (2120) is f3, and the operating frequency of the first operating coil (2120_1) corresponding to the circular crater is f1 (f1> f3). If the difference between the two operating frequencies is greater than 3 kHz and the two operating frequencies cannot be matched even if f1 is lowered by asymmetric control, the processor (2200) can lower the operating frequency f3 of the square operating coils (2120_3 to 2130_6) by asymmetric control so that the frequency difference between f1 and f3 becomes greater than 5 kHz.

[0157] The communication interface (2300) may include one or more components that enable communication between the induction heating device (2000) and the cooking vessel (101), the induction heating device (2000) and a server device (not shown), or the induction heating device (2000) and a user terminal (not shown). For example, the communication interface (2300) may include a short-range wireless communication interface (2310) and a long-range wireless communication interface (2320). The short-range wireless communication interface (2310) may include, but is not limited to, a Bluetooth communication interface, a BLE (Bluetooth Low Energy) communication interface, a near field communication interface, a WLAN (Wi-Fi) communication interface, a Zigbee communication interface, an IrDA (infrared Data Association) communication interface, a WFD (Wi-Fi Direct) communication interface, an UWB (Ultra Wideband) communication interface, an Ant+ communication interface, etc. The remote communication unit (2320) can be used to communicate with a server device (not shown) when the cooking vessel (101) is remotely controlled by a server device in an IoT (Internet of Things) environment. The remote communication unit (2320) can include the Internet, a computer network (e.g., LAN or WAN), and a mobile communication unit. The mobile communication unit transmits and receives a wireless signal with at least one of a base station, an external terminal, and a server on a mobile communication network. Here, the wireless signal can include various types of data according to a voice call signal, a video call call signal, or a text / multimedia message transmission and reception. The mobile communication unit can include, but is not limited to, a 3G module, a 4G module, an LTE module, a 5G module, a 6G module, an NB-IoT module, an LTE-M module, etc.

[0158] The user interface (2400) may include an output interface (2410) and an input interface (2420). The output interface (2410) is for outputting an audio signal or a video signal and may include a display and an audio output unit, etc.

[0159] When the display and the touchpad are configured as a touch screen in a layered structure, the display can be used as an input interface (2420) in addition to the output interface (2410). The display can include at least one of a liquid crystal display, a thin film transistor-liquid crystal display, a light-emitting diode (LED), an organic light-emitting diode, a flexible display, a 3D display, and an electrophoretic display. In addition, depending on the implementation form of the induction heating device (2000), the induction heating device (2000) can include two or more displays.

[0160] The audio output unit can output audio data received from the communication interface (2300) or stored in the memory (2500). In addition, the audio output unit can output audio signals related to functions performed in the induction heating device (2000). The audio output unit can include a speaker, a buzzer, etc.

[0161] According to one embodiment of the present disclosure, the output interface (2410) can display information regarding the cooking vessel (101). For example, the output interface (2410) can output a GUI (Graphical User Interface) corresponding to identification information or product type information of the cooking vessel (101). Additionally, the output interface (2410) can output information regarding the current location of the cooking vessel (101).

[0162] The input interface (2420) is for receiving input from a user. The input interface (2420) may be at least one of a key pad, a dome switch, a touch pad (contact electrostatic capacitance type, pressure resistive film type, infrared detection type, surface ultrasonic conduction type, integral tension measurement type, piezo effect type, etc.), a jog wheel, and a jog switch, but is not limited thereto.

[0163] The input interface (2420) may include a voice recognition module. For example, the induction heating device (2000) may receive a voice signal, which is an analog signal, through a microphone, and convert the voice portion into computer-readable text using an Automatic Speech Recognition (ASR) model. The induction heating device (2000) may interpret the converted text using a Natural Language Understanding (NLU) model to obtain the user's speech intent. Here, the ASR model or the NLU model may be an artificial intelligence model. The artificial intelligence model may be processed by an artificial intelligence-dedicated processor designed with a hardware structure specialized for processing artificial intelligence models. The artificial intelligence model may be created through learning. Here, being created through learning means that a basic artificial intelligence model is learned using a plurality of learning data by a learning algorithm, thereby creating a predefined operation rule or artificial intelligence model set to perform a desired characteristic (or purpose). The artificial intelligence model may be composed of multiple neural network layers. Each of the multiple neural network layers has multiple weight values, and performs neural network operations through operations between the operation results of the previous layer and the multiple weight values.

[0164] Linguistic understanding is the technology of recognizing, applying, and processing human language / characters, including natural language processing, machine translation, dialog systems, question answering, and speech recognition / synthesis.

[0165] The memory (2500) may store a program for processing and controlling the processor (2200), and may store input / output data (e.g., unique identification information of the cooking vessel (101), variable identification information of the cooking vessel (101), multiple power transmission patterns, cooking progress information of the cooking vessel (101), etc.). The memory (2500) may also store an artificial intelligence model.

[0166] The memory (2500) may include at least one type of storage medium among a flash memory type, a hard disk type, a multimedia card micro type, a card type memory (e.g., SD or XD memory, etc.), a RAM (Random Access Memory), a SRAM (Static Random Access Memory), a ROM (Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), a PROM (Programmable Read-Only Memory), a magnetic memory, a magnetic disk, and an optical disk. In addition, the induction heating device (2000) may also operate a web storage or cloud server that performs a storage function on the Internet.

[0167] An induction heating device according to one embodiment of the present disclosure includes a first working coil for a first burner having a circular shape, a second working coil for a second burner having a square shape, an inverter including a plurality of switches for switching current to flow between the first working coil and the second working coil, and a processor for controlling switching of the plurality of switches of the inverter, wherein an operating frequency of the first working coil and an operating frequency of the second working coil differ by a predetermined frequency value or more due to an inductance value of the first working coil and an inductance value of the second working coil.

[0168] In one embodiment of the present disclosure, an induction heating device includes a first working coil that is wound in a circular shape and a second automatic coil that is wound in a square shape.

[0169] In an induction heating device according to one embodiment of the present disclosure, a predetermined frequency value is a value of 5 kH or more.

[0170] In an induction heating device according to one embodiment of the present disclosure, the inverter further includes a second resonant capacitor that resonates with the second operating coil, and the plurality of switches include a third switch and a fourth switch that are switched on and off for resonance between the second operating coil and the second resonant capacitor, wherein the processor performs asymmetric control to make the on-duty ratio of the third switch greater than the on-duty ratio of the fourth switch so as to control the operating frequency of the second operating coil and the operating frequency of the first operating coil to differ by a predetermined frequency value or more.

[0171] In an induction heating device according to one embodiment of the present disclosure, the processor performs asymmetric control so that the operating frequency of the second working coil and the operating frequency of the first working coil do not differ by more than a predetermined frequency value depending on the investment rate of the cooking vessel heated by the second working coil, and performs asymmetric control so that the operating frequency of the second working coil and the operating frequency of the first working coil differ by more than a predetermined frequency value.

[0172] In an induction heating device according to one embodiment of the present disclosure, the operating frequency of the second operating coil is lower than the operating frequency of the first operating coil by a predetermined frequency value or more.

[0173] In an induction heating device according to one embodiment of the present disclosure, the predetermined frequency value is a value of 5 kHz or more and 10 kHz or less.

[0174] An induction heating device according to one embodiment of the present disclosure further includes a current detection unit for detecting a current flowing in a second working coil, and a voltage detection unit for detecting a voltage of the second working coil, wherein the processor detects a phase difference between a voltage applied to the second working coil by a cooking vessel by the voltage detection unit and a current flowing in the second working coil by the current detection unit.

[0175] In an induction heating device according to one embodiment of the present disclosure, the processor determines that the investment rate of the cooking vessel is lower than a predetermined value as the phase difference of the current becomes greater than a predetermined value, and performs asymmetric control based on the determination that the investment rate of the cooking vessel is lower than the predetermined value.

[0176] In an induction heating device according to one embodiment of the present disclosure, the processor performs asymmetric control at a frequency identical to the frequency in symmetric control, which makes the on-duty ratio of the third switch and the on-duty ratio of the fourth switch the same before asymmetric control.

[0177] In an induction heating device according to one embodiment of the present disclosure, the inverter further includes a first resonant capacitor resonating with a first working coil, and a first switch and a second switch that are switched on and off for resonance between the first working coil and the first resonant capacitor, wherein the processor controls the on-duty ratio of the first switch and the second switch to a fixed value during asymmetric control.

[0178] An induction heating device according to one embodiment of the present disclosure includes a first working coil for a first burner, a second working coil for a second burner, an inverter including a plurality of switches for switching current to flow between the first working coil and the second working coil, and a processor for controlling switching of the plurality of switches, wherein a maximum operating frequency of the first working coil and a maximum operating frequency of the second working coil differ by 5 kHz or more.

[0179] In an induction heating device according to one embodiment of the present disclosure, the first crater has a circular shape, and the second crater has a square shape.

[0180] In an induction heating device according to one embodiment of the present disclosure, the inverter further includes a resonant capacitor that resonates with the second operating coil, and the plurality of switches include a third switch and a fourth switch that are switched on and off for resonance between the second operating coil and the resonant capacitor, wherein the processor performs asymmetric control to make the on-duty ratio of the third switch greater than the on-duty ratio of the fourth switch so as to control the operating frequency of the second operating coil and the operating frequency of the first operating coil to differ by at least 5 kHz.

[0181] In an induction heating device according to one embodiment of the present disclosure, the processor performs asymmetric control according to the investment rate of the cooking vessel heated by the second working coil or the cooking vessel being misaligned with the second burner.

[0182] In an induction heating device according to one embodiment of the present disclosure, the processor determines that the permeability of the cooking vessel is lower than a predetermined value when a phase difference between a voltage applied to a second working coil of the cooking vessel and a current flowing in the second working coil becomes greater than a predetermined value, and the processor performs asymmetric control based on the determination that the permeability of the cooking vessel is lower than the predetermined value.

[0183] In an induction heating device according to one embodiment of the present disclosure, the processor determines that the cooking vessel is misaligned with the second burner when a phase difference between a voltage applied to the second operating coil of the cooking vessel and a current flowing in the second operating coil becomes greater than a predetermined value, and the processor performs asymmetric control based on the determination that the cooking vessel is misaligned with the second burner.

[0184] In an induction heating device according to one embodiment of the present disclosure, the processor performs asymmetric control at a frequency identical to the frequency in symmetric control, which makes the on-duty ratio of the third switch and the on-duty ratio of the fourth switch the same before asymmetric control.

[0185] In an induction heating device according to one embodiment of the present disclosure, the inverter further includes a first resonant capacitor resonating with a first working coil, and a first switch and a second switch that are switched on and off for resonance between the first working coil and the first resonant capacitor, wherein the processor controls the on-duty ratio of the first switch and the second switch to a fixed value during asymmetric control.

[0186] A noise reduction method in an induction heating device according to one embodiment of the present disclosure includes the steps of operating a first working coil for a first crater having a circular shape and a second working coil for a second crater having a square shape according to a user's input, determining whether the operating frequencies of the first working coil and the second working coil differ by a predetermined frequency value or more, and performing asymmetric control so that an on-duty ratio of a third switch among a third switch and a fourth switch that are turned on and off for resonance between the second working coil and the second resonance capacitor is greater than an on-duty ratio of the fourth switch based on the determination that the operating frequencies of the first working coil and the second working coil do not differ by a predetermined frequency value or more.

[0187] A method according to an embodiment of the present disclosure may be implemented in the form of program commands that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, etc., alone or in combination. The program commands recorded on the medium may be those specially designed and configured for the present disclosure or may be known and available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program commands, such as ROMs, RAMs, and flash memories. Examples of program commands include not only machine language codes generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter, etc.

[0188] Some embodiments of the present disclosure may also be implemented in the form of a recording medium containing computer-executable instructions, such as program modules, executed by a computer. Computer-readable media may be any available media that can be accessed by a computer, and include both volatile and nonvolatile media, removable and non-removable media. Furthermore, computer-readable media may include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules, or other data. Communication media typically contains computer-readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transport mechanism, and includes any information delivery media. Furthermore, some embodiments of the present disclosure may also be implemented as a computer program or computer program product containing computer-executable instructions, such as a computer program that is executed by a computer.

[0189] A device-readable storage medium may be provided in the form of a non-transitory storage medium. Here, the term "non-transitory storage medium" simply means a tangible device that does not contain signals (e.g., electromagnetic waves). This term does not distinguish between cases where data is permanently stored in the storage medium and cases where data is temporarily stored. For example, a "non-transitory storage medium" may include a buffer in which data is temporarily stored.

[0190] According to one embodiment, the method according to various embodiments disclosed in the present document may be provided as included in a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read-only memory (CD-ROM)), or may be distributed online (e.g., downloaded or uploaded) through an application store or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product (e.g., a downloadable app) may be temporarily stored or temporarily generated in a machine-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or an intermediary server.

Claims

1. First crater; A first working coil for the first crater; Crater 2; A second working coil for the second crater; An inverter including a plurality of switches for switching current to flow through the first operating coil and the second operating coil; and Including a processor that controls switching of the plurality of switches of the inverter, An induction heating device, wherein the first operating frequency of the first operating coil and the second operating frequency of the second operating coil differ by a predetermined frequency value or more due to the inductance value of the first operating coil and the inductance value of the second operating coil.

2. In paragraph 1, An induction heating device, wherein the first working coil is a coil wound in a circular shape and the second automatic coil is a coil wound in a square shape.

3. In any one of paragraphs 1 to 2, An induction heating device having a frequency value of 5 kH or higher.

4. In any one of paragraphs 1 to 3, The above inverter, A first resonant capacitor resonating with the first operating coil; Further comprising a second resonant capacitor resonating with the second operating coil, The above plurality of switches include a first switch and a second switch that are switched on and off for resonance between the first operating coil and the first resonant capacitor, and Including a third switch and a fourth switch that are switched on and off for resonance between the second operating coil and the second resonant capacitor, An induction heating device, wherein the processor performs asymmetric control to make the on-duty ratio of the third switch greater than the on-duty ratio of the fourth switch, in order to control the second operating frequency and the first operating frequency to have a difference greater than the predetermined frequency value.

5. In paragraph 4, An induction heating device in which the processor performs the asymmetric control so that the second operating frequency and the first operating frequency differ by at least the predetermined frequency value when the second operating frequency and the first operating frequency do not differ by at least the predetermined frequency value depending on the investment rate of the cooking vessel heated by the second operating coil.

6. In paragraph 5, An induction heating device, wherein the processor performs the asymmetric control so that the second operating frequency is lower than the first operating frequency by a predetermined frequency value or more.

7. In any one of paragraphs 5 to 6, An induction heating device wherein the above-mentioned predetermined frequency value is 5 kHz or more and 10 kHz or less.

8. In any one of paragraphs 5 to 7, The above induction heating device comprises a current detection unit that detects the current flowing in the second operating coil; and Further comprising a voltage detection unit for detecting the voltage of the second operating coil, An induction heating device, wherein the processor detects a phase difference between a voltage applied to the second working coil by the cooking vessel by the voltage detection unit and a current flowing to the second working coil by the current detection unit.

9. In paragraph 8, An induction heating device in which the processor determines that the investment rate of the cooking vessel is lower than the predetermined investment rate when the phase difference of the current becomes greater than a predetermined value, and performs the asymmetric control based on the determination that the investment rate of the cooking vessel is lower than the predetermined investment rate.

10. In any one of paragraphs 4 to 9, An induction heating device in which the above processor performs the asymmetric control at a frequency identical to that of the symmetric control in which the on-duty ratio of the third switch and the on-duty ratio of the fourth switch are identical before the asymmetric control.

11. In any one of paragraphs 4 to 10, The above inverter, An induction heating device, wherein the processor controls the on-duty ratio of the first switch and the on-duty ratio of the second switch to fixed values ​​during the asymmetric control.

12. Crater 1; A first working coil for the first crater; Crater 2; A second working coil for the second crater; An inverter including a plurality of switches for switching current to flow through the first operating coil and the second operating coil; and Including a processor that controls switching of the plurality of switches, An induction heating device in which the processor controls the maximum operating frequency of the first operating coil and the maximum operating frequency of the second operating coil to have a difference of 5 kHz or more.

13. In paragraph 12, The above inverter, A first resonant capacitor resonating with the first operating coil; Further comprising a second resonant capacitor resonating with the second operating coil, The above plurality of switches include a first switch and a second switch that are switched on and off for resonance between the first operating coil and the first resonant capacitor, and a third switch and a fourth switch that are switched on and off for resonance between the second operating coil and the resonant capacitor, An induction heating device, wherein the processor performs asymmetric control to make the on-duty ratio of the third switch greater than the on-duty ratio of the fourth switch, so as to control the operating frequency of the second operating coil and the operating frequency of the first operating coil to differ by at least 5 kHz.

14. In paragraph 13, An induction heating device in which the processor performs the asymmetric control according to the investment rate of the cooking vessel heated by the second operating coil or the cooking vessel being misaligned with the second burner.

15. A noise reduction method of an induction heating device comprising a plurality of switches, including a first crater, a first working coil for the first crater, a second crater, a second working coil for the second crater, an inverter for switching current to flow between the first working coil and the second working coil, a resonance capacitor for resonance with the second working coil, and a first switch and a second switch for turning on and off for resonance between the second working coil and the resonance capacitor, the method comprising: A step of operating the first operating coil and the second operating coil according to a user's input; A step of determining whether the operating frequency of the first operating coil and the operating frequency of the second operating coil differ by a predetermined frequency value or more; A method for reducing noise in an induction heating device, comprising the step of performing asymmetric control so that the on-duty ratio of the first switch is greater than the on-duty ratio of the second switch based on a determination that the operating frequency of the first operating coil and the operating frequency of the second operating coil do not differ by more than a predetermined frequency value.

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