Induction heating device for driving multiple heating coils via two switches

Abstract

According to an embodiment of the present disclosure, an induction heating device for driving multiple heating coils by using a single inverter is disclosed. The induction heating device comprises: a first heating coil for inner-side heating of a circular burner; a second heating coil for outer-side heating; an inverter including a first switch and a second switch connected in series with each other; a first resonant capacitor connected to a first side of the first switch and connected to a first end of the second heating coil; and a second resonant capacitor connected to a second side of the first switch and a first side of the second switch, and connected to a second end of the second heating coil and a first end of the first heating coil, wherein a second side of the second switch is connected to a second end of the first heating coil.

Description

Induction heating device that drives multiple heating coils with two switches

[0001] One embodiment of the present disclosure relates to an induction cooking device having inner and outer heating coils, wherein the inner and outer heating coils are driven by a single inverter having two switches.

[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 rises. 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] An induction range may include one or more burners. In this case, the burners may heat a cooking vessel placed on the burner by means of an inner heating coil and an outer heating coil.

[0004] According to one embodiment of the present disclosure, an induction heating device driving a plurality of heating coils with a single inverter is disclosed. According to one embodiment, the induction heating device may include a first heating coil for heating the inside of a circular burner. According to one embodiment, the induction heating device may include a second heating coil for heating the outside of the circular burner. According to one embodiment, the induction heating device may include a link capacitor for establishing a full-wave rectified voltage at both ends. According to one embodiment, the induction heating device may include a first switch and a second switch connected in series and an inverter connected in parallel with the link capacitor. According to one embodiment, the induction heating device may include a first resonant capacitor connected to a first side of the first switch and connected to a first end of the second heating coil. An induction heating device according to one embodiment may include a second resonant capacitor connected to a second side of a first switch and a first side of a second switch and connected to a second end of a second heating coil and a first end of the first heating coil. An induction heating device according to one embodiment may include a processor that controls the first switch and the second switch to be alternately turned on and off so that a magnetic field is induced in the first heating coil and the second heating coil, wherein the second side of the second switch is connected to the second end of the first heating coil.

[0005] FIG. 1 is a drawing for explaining an induction heating device according to one embodiment of the present disclosure.

[0006] FIG. 2 illustrates an induction heating device including a rectangular cooking area according to one embodiment of the present disclosure.

[0007] FIG. 3 is a drawing showing a circular furnace including an inner heating coil and an outer heating coil according to one embodiment of the present disclosure.

[0008] FIG. 4A is a cross-sectional view showing a cooking vessel placed on a burner driven by a plurality of heating coils according to one embodiment of the present disclosure.

[0009] FIG. 4b is a cross-sectional view showing a cooking vessel placed on a burner driven by a plurality of heating coils according to one embodiment of the present disclosure.

[0010] FIG. 5 is an inverter circuit diagram of an induction heating device for operating a plurality of heating coils according to one embodiment of the present disclosure.

[0011] FIG. 6 is an inverter circuit diagram of an induction heating device for operating a plurality of heating coils according to one embodiment of the present disclosure.

[0012] FIG. 7 is a circuit diagram for driving multiple heating coils with two switches according to one embodiment of the present disclosure.

[0013] FIG. 8 is a graph showing current and gate waveforms when operating an induction heating device according to one embodiment of the present disclosure.

[0014] FIG. 9a is a circuit diagram showing a current flow in one section according to one embodiment of the present disclosure.

[0015] FIG. 9b is a circuit diagram showing a two-section current flow according to one embodiment of the present disclosure.

[0016] FIG. 9c is a circuit diagram showing current flow in three sections according to one embodiment of the present disclosure.

[0017] FIG. 9d is a circuit diagram showing current flow in four sections according to one embodiment of the present disclosure.

[0018] FIG. 9e is a circuit diagram showing current flow in five sections according to one embodiment of the present disclosure.

[0019] FIG. 9f is a circuit diagram showing current flow in six sections according to one embodiment of the present disclosure.

[0020] FIG. 10 is a drawing showing a case where the size of a cooking vessel placed on a burner changes according to one embodiment of the present disclosure.

[0021] FIG. 11A is a waveform diagram of a current flowing in a heating coil according to a change in inductance of the outer heating coil according to one embodiment of the present disclosure.

[0022] FIG. 11b is a waveform diagram of a current flowing in a heating coil according to a change in inductance of the outer heating coil according to one embodiment of the present disclosure.

[0023] FIG. 12 is a graph showing the voltage gain by frequency according to the change in inductance of a heating coil according to one embodiment of the present disclosure.

[0024] Fig. 13 is an equivalent circuit of an inverter and a resonant circuit according to one embodiment of the present disclosure.

[0025] FIG. 14a is a circuit diagram for driving a plurality of heating coils with switches added to the outer heating coil path according to one embodiment of the present disclosure.

[0026] FIG. 14b is a circuit diagram for driving a plurality of heating coils with switches added to the outer heating coil path according to one embodiment of the present disclosure.

[0027] Figure 15 is a block diagram of an induction heating device according to one embodiment of the present disclosure.

[0028] The terms used in this disclosure will be briefly explained, and one embodiment of the present disclosure will be specifically described.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] An induction heating device may have a burner, and when heating a cooking vessel using multiple heating coils contained within the burner, an inverter is required to drive the multiple heating coils. When driving multiple heating coils, using a single inverter with two switches can reduce costs and component losses compared to an inverter with four switches. However, when operating multiple heating coils with a single inverter, the current flowing to the outer heating coils must be automatically controlled even when the cooking vessel does not cover the outer heating coils.

[0034] FIG. 1 is a drawing for explaining an induction heating device according to one embodiment of the present disclosure.

[0035] Referring to FIG. 1, an induction heating device (2000) according to an embodiment of the present disclosure may include a plurality of burners (201, 202, 203). Since the plurality of burners (201, 202, 203) in FIG. 1 have a circular shape, they may be referred to as a first burner (201), a second burner (202), and a third burner (203), respectively, and the first burner (201) may also be simply referred to as a 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.

[0036] 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.

[0037] According to one embodiment of the present disclosure, the cooking vessel (101) can be powered wirelessly from an induction heating device (2000) via 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.

[0038] According to one embodiment of the present disclosure, the type of cooking vessel (101) that wirelessly receives power from the 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.

[0039] 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 intended 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).

[0040] 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, an NFC (Near Field Communication interface), 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.

[0041] 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).

[0042] 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).

[0043] 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)) positioned on a top plate of the induction heating device (2000) using electromagnetic induction. The induction heating device (2000) may include a heating coil (working coil) that generates a magnetic field for inductively heating the cooking vessel (101). Throughout the present disclosure, the heating coil may also be referred to as a working coil.

[0044] Generating a magnetic field by a heating coil may include transmitting power by utilizing a magnetic field induced in an IH metal (e.g., iron component) through magnetic induction. For example, an induction heating device (2000) may generate an eddy current in a cooking vessel (101) by flowing a current through a heating coil to form a magnetic field.

[0045] According to one embodiment of the present disclosure, the induction heating device (2000) may include a plurality of heating 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 heating 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 heating coil is provided on the inside and a second heating coil is provided on the outside. The high-power cooking zone may include two or more heating coils.

[0046] 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.

[0047] 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 a heating coil due to the approach of the cooking vessel (101). In this way, the induction heating device (2000) can detect whether the size of the cooking vessel (101) is such that it covers only the inner heating coil or also the outer heating coil.

[0048] According to one embodiment of the present disclosure, the induction heating device (2000) may include a communication interface for communicating with an external device. 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.

[0049] 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).

[0050] 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 (2411) included in the user interface.

[0051] Referring to FIG. 1, 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.

[0052] FIG. 2 illustrates an induction heating device including a rectangular cooking area according to one embodiment of the present disclosure.

[0053] Referring to FIG. 2, an induction heating device (2000) according to one embodiment of the present disclosure may include a circular first burner (201) operated by a heating coil wound in a circular shape and a square second burner (204) operated by a plurality of heating coils having a square or near-square shape. The square of the second burner (204) may be rectangular, and the plurality of heating coils on the bottom of the square second burner (204) may include a plurality of rectangular or elongated oval heating coils.

[0054] In an induction heating device (2000), using a plurality of heating coils in a shape close to a square for a square second burner (204) has the advantage of eliminating a non-cooking area, for example, when a square pot is placed on it. 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) recognizes the cooking vessel and operates at least some of the corresponding plurality of heating coils necessary for heating the cooking vessel, thereby heating the contents of the cooking vessel.

[0055] FIG. 3 is a drawing showing a circular furnace including an inner heating coil and an outer heating coil according to one embodiment of the present disclosure.

[0056] The burner (201) of the induction heating device (2000) may be a high-power cooking area in which a first heating coil (2121) is provided as an inner heating coil and a second heating coil (2122) is provided as an outer heating coil. If the burner (201) is provided with a separate first heating coil (2121) on the inner side and a second heating coil (2122) on the outer side, the induction heating device (2000) can adjust the heating coil that operates according to the size of the cooking vessel (101). For example, if the cooking vessel (101) placed on the burner (201) is a cooking vessel (101) with a small diameter that does not cover the area where the second heating coil (2122) is placed, the induction heating device (2000) can operate only the first heating coil (2121) on the inside without operating the second heating coil (2122) on the outside. Conversely, if the cooking vessel (101) placed on the burner (201) is a cooking vessel (101) with a large diameter that covers the area where the second heating coil (2122) on the outside is placed, the induction heating device (2000) can operate not only the first heating coil (2121) on the inside but also the second heating coil (2122) on the outside to increase the heating output. When the cooking vessel (101) is large, if both the first heating coil (2121) and the second heating coil (2122) operate, almost the entire area of ​​the bottom of the cooking vessel (101) can be evenly heated and the cooking speed can be increased.

[0057] As seen above, since there are cases where the second heating coil (2122) does not operate when the first heating coil (2121) operates, the inverters for operating the first heating coil (2121) and the second heating coil (2122) need to be provided separately. Alternatively, even if the first heating coil (2121) and the second heating coil (2122) are operated by a single inverter, a method may be used in which the output to the second heating coil (2122) is blocked by an electronic switch or the like so that the second heating coil (2122) does not operate when the first heating coil (2121) operates. In the present disclosure, an induction heating device (2000) is disclosed that includes a method in which the first heating coil (2121) and the second heating coil (2122) are controlled without using a plurality of inverters and without blocking the output by a separate electronic switch or the like.

[0058] In one embodiment, the crater (201) may include three or more heating coils (e.g., an inner heating coil, a middle heating coil, and an outer heating coil) to further subdivide the high-power stage.

[0059] FIG. 4A is a cross-sectional view showing a cooking vessel placed on a burner driven by a plurality of heating coils according to one embodiment of the present disclosure.

[0060] The cooking vessel (101) may include a magnetic material (e.g., an IH metal) in which a magnetic field can be induced. The cooking vessel (101) may be inductively heated by an induction heating device (2000) and may be a container of various shapes 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 a heating coil (2120) of an induction heating device (2000), a magnetic field that varies over time is induced in the heating coil (2120). The magnetic field generated by the heating coil (2120) passes through the bottom of the cooking vessel (101). When the magnetic field that varies over 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), an eddy current, which is a current that rotates around the magnetic field, is generated in the IH metal. This phenomenon of electric current being induced by a magnetic field that changes over time is called electromagnetic induction. In the case of a cooking vessel (101), heat is generated at the bottom of the cooking vessel (101) due to eddy current and the resistance of the IH metal (e.g., iron). The contents of the cooking vessel (101) can be heated by the heat generated at this time.

[0061] Referring to FIG. 4A, the heating coil (2120) includes a first heating coil (2121) positioned on the inside of the burner and a second heating coil (2122) positioned on the outside. However, the size of the cooking vessel (101) currently placed on the burner does not cover the second heating coil (2122) on the outside. In this case, even if the second heating coil (2122) operates, it does not pass through the bottom of the cooking vessel (101). Therefore, in cases where the size of the cooking vessel (101) does not cover the second heating coil (2122) on the outside, it is preferable that only the first heating coil (2121) operate.

[0062] FIG. 4b is a cross-sectional view showing a cooking vessel placed on a burner driven by a plurality of heating coils according to one embodiment of the present disclosure.

[0063] According to FIG. 4b, the cooking vessel (101) is sufficiently large in size to cover the second heating coil (2122) positioned outside the burner. Therefore, when the cooking vessel (101) is large in size, not only the first heating coil (2121) on the inside but also the second heating coil (2122) needs to be operated.

[0064] FIG. 5 is an inverter circuit diagram of an induction heating device for operating a plurality of heating coils according to one embodiment of the present disclosure.

[0065] Referring to Fig. 5, the input power source (2211) is an AC power source, and the AC voltage of the AC power source is rectified by a rectifier circuit (2112) through an EMI (Electro Magnetic Interference) 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. When the AC voltage of the AC power source is full-wave rectified through the rectifier circuit (2112), the full-wave rectified voltage can be established across the link capacitors (2117_1, 2117_2).

[0066] In Fig. 5, two resonant circuits are illustrated assuming that there are two heating coils, a first heating coil (2121) and a second heating coil (2122). If three heating coils are required for the crater, additional resonant circuits can be added.

[0067] The rectified voltage established across the link capacitor C1 (2117_1) resonates between the first heating coil (2121) and the resonant capacitor 1 (2114_1) and the resonant capacitor 2 (2114_2) by the switching operation of the two switch elements, the first switch (2113_1) and the second switch (2113_2). The resonance generates a magnetic field in the first heating coil (2121). The magnetic field generated in the first heating coil (2121) generates an eddy current in the IH cooking container placed on the top of the first heating coil (2121), and the contents of the cooking container are heated by the eddy current. CT1 (2115_1) is a current sensing unit for detecting the current flowing in the first heating coil (2121). In one embodiment, the first heating coil (2121) may be an inner heating coil having a circular shape.

[0068] Likewise, the rectified voltage established in the link capacitor (2117_2) at the bottom resonates between the second heating coil (2122) and the resonant capacitor 3 (2114_3) and the resonant capacitor 4 (2114_4) by the switching operation of the two switch elements, the third switch (2113_3) and the fourth switch (2113_4). A magnetic field is generated in the second heating coil (2122) due to the resonance. The magnetic field generated in the second heating coil (2122) generates an eddy current in the cooking vessel (101) that covers up to the second heating coil (2122), which is the outer heating coil, to heat the contents of the cooking vessel. CT2 (2115_2) is a current detection unit for detecting the current flowing in the second heating coil (2122).

[0069] According to FIG. 5, a first inverter (2113a) including a first switch (2113_1) and a second switch (2113_2) and a second inverter (2113b) including a third switch (2113_3) and a fourth switch (2113_4) are required to drive a first heating coil (2121) inside the crater and a second heating coil (2122) outside the crater. Accordingly, a total of four switches - a first switch (2113_1), a second switch (2113_2), a third switch (2113_3), and a fourth switch (2113_4) - are required.

[0070] FIG. 6 is an inverter circuit diagram of an induction heating device for operating a plurality of heating coils according to one embodiment of the present disclosure.

[0071] Referring to Fig. 6, the input power source (2211) is an AC power source. The AC voltage of the input power source (2211) passes through an EMI filter (2111) and is rectified by a rectifier circuit (2112). The rectifier circuit (2112) is a device for converting the AC voltage into a DC voltage. A diode may be used, but a thyristor or other types of switching devices may also be used. When the AC voltage is full-wave rectified through the rectifier circuit (2112), the full-wave rectified voltage is applied across the link capacitors (2117_1, 2117_2). The full-wave rectified voltage may be partially smoothed by the link capacitors (2117_1, 2117_2).

[0072] The link capacitor's capacitance is typically sufficient to avoid power factor problems, as a large capacitance can cause the rectified voltage to become DC voltage, leading to power factor correction issues. When the inverter's input voltage reaches zero, there is no energy, which causes noise in the inverter's switching elements. Therefore, the link capacitor's capacitance is sufficient to prevent the inverter's input voltage from dropping completely to zero. Therefore, link capacitors typically have capacitances of 2 to 3 uF.

[0073] In Fig. 6, two resonance circuits are illustrated assuming that there are two heating coils, a first heating coil (2121) and a second heating coil (2122), but if three heating coils are required for the crater, a resonance circuit can be added.

[0074] The rectified voltage applied to the link capacitor C1 (2117_1) is used for resonance between the second heating coil (2122) and the first resonance capacitor (2114a) by the switching operation of the two switch elements, the first switch (2113_1) and the second switch (2113_2). The resonance causes a magnetic field to be generated in the second heating coil (2122). The magnetic field generated in the second heating coil (2122) generates an eddy current in the IH cooking vessel (101) placed on the top of the second heating coil (2122), thereby heating the contents of the cooking vessel. In one embodiment, the second heating coil (2122) may be an outer heating coil in a circular burner.

[0075] Likewise, the rectified voltage applied to the link capacitor (2117_1) is used for resonance between the first heating coil (2121) and the second resonance capacitor (2114b) by the switching operation of the two switch elements, the third switch (2113_3) and the fourth switch (2113_4). A magnetic field is generated in the first heating coil (2121) due to the resonance. The magnetic field generated in the first heating coil (2121) generates an eddy current in the cooking container (101) placed on the top of the first heating coil (2121), which is the inner heating coil, thereby heating the contents of the cooking container.

[0076] According to FIG. 6, an inverter (2113c) including a first switch (2113_1), a second switch (2113_2), a third switch (2113_3), and a fourth switch (2113_4) is required to drive the first heating coil (2121) inside the crater and the second heating coil (2122) outside the crater. Accordingly, the inverter (2113c) of FIG. 6 also requires a total of four switches, similar to that of FIG. 5 - the first switch (2113_1), the second switch (2113_2), the third switch (2113_3), and the fourth switch (2113_4).

[0077] FIG. 7 is a circuit diagram for driving multiple heating coils with two switches according to one embodiment of the present disclosure.

[0078] According to Fig. 7, the operation of the input power supply (2211), EMI filter (2111), and rectifier circuit (2112) is the same as in the previous Figs. 5 and 6. The AC voltage of the input power supply (2211) is full-wave rectified through the rectifier circuit (2112). A link capacitor (2117) may be positioned after the rectifier circuit (2112). A full-wave rectified voltage is applied to both ends of the link capacitor (2117).

[0079] In Fig. 7, a case is illustrated where there are two heating coils in one crater, a first heating coil (2121) and a second heating coil (2122).

[0080] The rectified voltage established at both ends of the link capacitor (2117) induces a magnetic field in the first heating coil (2121) and the second heating coil (2122) by the switching operation of the first switch (2113_1) and the second switch (2113_2). In addition, a switch for blocking the operation of the second heating coil (2122) so that the second heating coil (2122) is not driven separately to drive only the first heating coil (2121) is not required. The first heating coil (2121) resonates with the second resonance capacitor (2114b), and the second heating coil (2122) resonates with the first resonance capacitor (2114a). A magnetic field is generated in the first heating coil (2121) and the second heating coil (2122) by resonance. The magnetic field generated in the first heating coil (2121) generates an eddy current in the IH cooking vessel (101) placed on top of the first heating coil (2121), thereby heating the contents of the cooking vessel. In one embodiment, the first heating coil (2121) may be an inner heating coil of a circular burner. In addition, the magnetic field generated in the second heating coil (2122) generates an eddy current in the outer periphery of the cooking vessel (101) covering up to the second heating coil (2122), thereby heating the contents of the cooking vessel. In one embodiment, the second heating coil (2122) may be an outer heating coil in a circular burner. The second heating coil (2122) may operate together with the first heating coil (2121).

[0081] According to FIG. 7, a single inverter including a first switch (2113_1) and a second switch (2113_2) can drive two coils, a first heating coil (2121) and a second heating coil (2122), so that the cost of the switch element can be reduced compared to the inverter according to FIG. 5 or FIG. 6. In addition, in the inverter and resonant circuit according to FIG. 7, a separate switch for blocking the driving of the second heating coil (2122) is not required.

[0082] Looking at the inverter and resonant circuit according to FIG. 7, it includes an inverter (2113d) connected in parallel with a link capacitor (2117). According to one embodiment of the present disclosure, the inverter (2113d) includes a first switch (2113_1) and a second switch (2113_2) connected in series with each other. According to one embodiment, the first resonant capacitor (2114a) is connected to a first side, which is a drain of the first switch (2113_1), and is connected to a first terminal of the second heating coil (2112).

[0083] According to one embodiment, the second resonant capacitor (2114b) is connected to the second side, which is the source of the first switch (2113_1), and the first side, which is the drain of the second switch (2113_2), and is connected to the second terminal of the second heating coil (2122) and the first terminal of the first heating coil (2113_1).

[0084] According to one embodiment, the second side, which is the source of the second switch (2113_2), is connected to the second terminal of the first heating coil (2122).

[0085] According to one embodiment, a processor (not shown) of an induction heating device (2000) can control a switching operation in which a first switch (2113_1) and a second switch (2113_2) are alternately turned on and off so that a magnetic field is induced in the first heating coil (2121) and the second heating coil (2122). Of course, this is one embodiment, and the induction heating device (2000) may also include a separate driving processor for operating the first switch (2113_1) and the second switch (2113_2).

[0086] In a circuit such as FIG. 7, an input current is supplied from a link capacitor (2117) to an inverter (2113d) during the entire cycle of the input voltage (2211), so that the first switch (2113_1) and the second switch (2113_2) are alternately turned on and off during the entire cycle of the input voltage (2211), and a magnetic field can be induced in the first heating coil (2121) and the second heating coil (2122).

[0087] According to one embodiment, one cycle of the input current supplied from the link capacitor (2117) to the inverter (2113d) is composed of a first half cycle and a second half cycle. According to one embodiment, energy by the input current may be supplied to the first heating coil (2121) during the first half cycle, and energy by the input current may be supplied to the second heating coil (2122) during the second half cycle. A magnetic field is induced in each heating coil by the supplied energy. According to one embodiment, the peak value of the input current during the first half cycle and the peak value of the input current during the second half cycle may be different from each other. According to one embodiment, the peak value of the input current during the first half cycle and the peak value of the input current during the second half cycle can be changed by adjusting the inductance of the first heating coil (2121) and the capacitance of the second resonant capacitor (2114b) and the inductance of the second heating coil (2122) and the capacitance of the first resonant capacitor (2114a).

[0088] In order to explain the operation of the induction heating device (2000) according to Fig. 7 by section, let us look at Figs. 8 to 9f.

[0089] FIG. 8 is a graph showing current and gate waveforms when operating an induction heating device according to one embodiment of the present disclosure.

[0090] 810 is a graph showing the current and gate waveform for each operating section, and 820 shows the current and gate input corresponding to the 810 graph.

[0091] I_In represents the input current flowing from the link capacitor (2117) to the inverter (2113d). As can be seen in 810, I_In flows throughout the entire cycle. I_in_coil represents the current flowing in the first heating coil (2121), which is the inner heating coil of the crater, and the positive direction of the current is as shown in 820. If we check the waveform of I_in_coil in 810, we can see that the current that causes resonance with C_in, which is the second resonance capacitor (2114b), flows throughout the entire cycle. I_out_coil represents the current flowing in the second heating coil (2122), which is the outer heating coil of the crater, and the positive direction of the current is as shown in 820. If we check the waveform of I_out_coil at 810, we can see that it resonates with C_out, which is the first resonant capacitor (2114a), throughout the entire cycle. Gate_H is the gate waveform applied to the gate of the first switch (2113_1). Gate_L is the gate waveform applied to the gate of the second switch (2113_2).

[0092] Looking at 810, it can be divided into 1 section (t0-t1), 2 sections (t1-t2), 3 sections (t2-t3), 4 sections (t3-t4), 5 sections (t4-t5), and 6 sections (t5-t6) depending on the gate waveform and input current.

[0093] Let us examine the flow of current in the inverter (2113d), the resonant capacitor, and the heating coil, as well as the operation of the entire induction heating device (2000), for each section from section 1 to section 6 through Figures 9a to 9f.

[0094] FIG. 9a is a circuit diagram showing a current flow in one section according to one embodiment of the present disclosure.

[0095] Section 1 (t0-t1) is a section in which the first switch (2113_1) is on, the second switch (2113_2) is off, and the input current (I_In) crosses zero and rises to a positive value. At this time, both I_in_coil and I_out_coil have positive values ​​based on the direction indicated in the preceding Figure 8. Control of the first switch (2113_1) turning on and the second switch (2113_2) turning off can be performed by the processor of the induction heating device (2000).

[0096] In the first section, the energy stored in the second heating coil (2122) is discharged, charging the first resonant capacitor (2114a). And since the first switch (2113_1) is turned on, the input current (I_In) charges the second resonant capacitor (2114b), C_in, through the first switch (2113_1). The input current (I_In) flows through the second resonant capacitor (2114b), C_in, to the first heating coil (2121).

[0097] FIG. 9b is a circuit diagram showing a two-section current flow according to one embodiment of the present disclosure.

[0098] In the second section, the first switch (2113_1) is on, the second switch (2113_2) is off, and the current I_out_coil flowing in the second heating coil (2122) has a negative value, so the direction of the current changes, unlike in the first section.

[0099] In the second section, the input current (I_In) continuously charges the second resonant capacitor (2114b), C_in, and the energy stored in the existing first resonant capacitor (2114a) is discharged, causing I_out_coil to flow to the second heating coil (2122). In addition, as the first resonant capacitor (2114a) discharges, the second resonant capacitor (2114b) is charged through the first switch (2113_1).

[0100] FIG. 9c is a circuit diagram showing current flow in three sections according to one embodiment of the present disclosure.

[0101] In the third section, both the first switch (2113_1) and the second switch (2113_2) are controlled to be turned off by the processor. In the third section, the input current (I_In) crosses zero and falls to a negative value. The energy stored in the second heating coil (2122) is discharged and used to charge the first resonant capacitor (2114a), C_out, in the reverse direction.

[0102] The energy stored in the first heating coil (2121) is used to charge the second resonant capacitor (2114b), C_in, through the anti-parallel diode of the second switch (2113_2).

[0103] FIG. 9d is a circuit diagram showing current flow in four sections according to one embodiment of the present disclosure.

[0104] In the 4th section, the processor controls the first switch (2113_1) to be turned off and the second switch (2113_2) to be turned on. In the 4th section, the input current (I_In) maintains a negative value, and the current I_in_coil flowing in the first heating coil (2121) decreases from a positive value to zero.

[0105] The current flow in section 4 is almost the same as that in section 3, but since the second switch (2113_2) is on, unlike in section 3 where the current flowed to the anti-parallel diode of the second switch (2113_2), in section 4 it flows to the second switch (2113_2). When the current flows to the second switch (2113_2), the conduction loss is relatively reduced compared to when the current flowed to the anti-parallel diode.

[0106] In section 4, the energy stored in the second heating coil (2122) is used to charge the first resonant capacitor (2114a), C_out, in the reverse direction.

[0107] FIG. 9e is a circuit diagram showing current flow in five sections according to one embodiment of the present disclosure.

[0108] In section 5, the first switch (2113_1) is turned off, and the second switch (2113_2) is turned on. In section 5, the input current (I_In) changes from negative to zero, and the I_in_coil flowing through the first heating coil (2121) crosses zero and falls to negative. In addition, the I_out_coil flowing through the second heating coil (2122) changes from negative to zero.

[0109] In the 5th section, all of the energy stored in the first heating coil (2121) in the previous 4 sections is discharged, and magnetic energy is charged in the reverse direction in the first heating coil (2121) by the second resonant capacitor (2114b).

[0110] FIG. 9f is a circuit diagram showing current flow in six sections according to one embodiment of the present disclosure.

[0111] Section 6 is the section where the first switch (2113_1) remains off and the second switch (2113_2) remains on. In section 6, the input current (I_In) has a positive value after zero crossing, and I_in_coil flowing through the first heating coil (2121) maintains a negative value. In addition, I_out_coil flowing through the second heating coil (2122) becomes positive after zero crossing.

[0112] The input current (I_In) charges the first resonant capacitor (2114a), C_out, and the energy charged in the second resonant capacitor (2114b), C_in, forms a current path through which it is discharged through the lower switch and I_in_coil. Accordingly, at this time, magnetic energy is charged in the first heating coil (2121).

[0113] According to the resonant circuit by the inverter of the induction heating device (2000) according to one embodiment of the present disclosure as examined through FIGS. 9A to 9F, it can be seen that the input current (I_In) continues to flow without interruption for one cycle. In the case of a general half-bridge inverter, since the energy by the input power is transferred for only half of one cycle, the remaining half cycle becomes a section where the energy stored in the resonant capacitor is discharged, and there is a disadvantage in that the peak component of the input current (I_In) increases. However, according to the resonant circuit by the inverter according to FIGS. 7 and 9a to 9f, the energy by the input power is transferred to the first heating coil (2121), which is the inner heating coil among the first heating coil (2121) and the second heating coil (2122), during half of one cycle (half cycle), and is transferred to the second heating coil (2122), which is the outer heating coil, during the remaining half cycle, and the first heating coil (2121) resonates with the second resonant capacitor (2114a) with the stored energy. In this way, according to the resonant circuit by the inverter according to FIGS. 7 and 9a to 9f, the size of the peak component of the input current (I_In) is reduced compared to when a general half-bridge inverter is used. When the size of the peak component of the input current (I_In) is reduced, it is advantageous for protecting the inverter components including the switching components, and noise can also be reduced.

[0114] In order to reduce the size of the peak component of the input current (I_In), the time constants (resonant capacitor capacitance and heating coil inductance) of the inner and outer heating coils can be set differently, thereby adjusting the relative ratio of the current flowing through the inner and outer heating coils. Refer to Fig. 10 for an explanation of this.

[0115] FIG. 10 is a drawing showing a case where the size of a cooking vessel placed on a burner changes according to one embodiment of the present disclosure.

[0116] In Fig. 10, the dotted circle indicates the size of the cooking vessel (101) placed on the top plate of the induction heating device (2000). The cooking vessel (101) is a vessel having magnetic properties, such as iron or stainless steel, and when an alternating magnetic field is applied to such a cooking vessel (101), the bottom surface of the cooking vessel (101) absorbs the magnetic field, and the absorbed magnetic field is converted into heat by the eddy current and the resistance within the cooking vessel (101). As the amount of the absorbed magnetic field increases, the inductance of the heating coil decreases. For example, in Fig. 1010, it can be seen that a cooking vessel (101) having a relatively small diameter is placed on the top plate of the induction heating device (2000). In this case, according to the resonance circuit by the inverter of the induction heating device (2000) according to one embodiment of the present disclosure, a large current flows in the first heating coil (2121), which is the inner heating coil, and a small current flows in the second heating coil (2122), which is the outer heating coil. In contrast, as in 1020, if a sufficiently large cooking vessel covering the second heating coil (2122), which is the outer heating coil of the circular burner, is placed on the top plate of the induction heating device (2000), the inductance value of the second heating coil (2122) becomes smaller, so the current flowing in the second heating coil (2122) automatically becomes larger compared to the case of 1010.

[0117] In Fig. 10, regardless of the size of the cooking vessel (101), the first heating coil (2121) is covered by the bottom surface of the cooking vessel (101), so the inductance reduced in the first heating coil (2121) is the same. However, the inductance of the second heating coil (2122) is different when the cooking vessel (101) is small (1010) and large (1020). When the size of the cooking vessel (101) is large (1020), the inductance of the second heating coil (2122) becomes relatively small. Unlike the inverter according to one embodiment of the present disclosure, in the past, two inverters were used and the inner heating coil and the outer heating coil were driven individually by each inverter. An induction heating device including an inverter using such a driving method needs to detect the size of the cooking vessel (101) to determine whether to operate only the inner heating coil or also the outer heating coil. In addition, if the cooking vessel (101) is not aligned with the center of the circular burner and is placed only partially over the outer heating coil, there are cases where it becomes ambiguous as to whether the induction heating device should operate the outer heating coil. If the cooking vessel (101) completely covers the inner heating coil and only partially covers the outer heating coil and the outer heating coil does not operate, the outer perimeter of the cooking vessel (101) may not properly transmit heat, resulting in a problem where only the middle part of the cooking vessel (101) becomes locally hot. However, in the inverter and the resonant circuit according to one embodiment of the present disclosure, the inductance of the outer heating coil changes depending on the size of the cooking vessel (101), and the current flowing to the outer heating coil automatically increases or decreases. Therefore, the induction heating device (2000) having the inverter and the resonant circuit according to one embodiment of the present disclosure does not require a separate sensor to determine the size of the cooking vessel (101). In addition, malfunctions that may occur due to the size of the cooking container (101) not being properly judged can be prevented.When the size of the cooking vessel (101) is small and the outer heating coil is not covered, the current flowing in the outer heating coil is minimum, and when the size of the cooking vessel (101) is large and the outer heating coil is covered, the current flowing in the outer heating coil is maximum.

[0118] According to the inverter and resonance circuit of the induction heating device (2000) according to one embodiment of the present disclosure, when a plurality of heating coils are driven, a single inverter including two switches is used, so that the number of switch elements is reduced by half, thereby ensuring slimness and cost competitiveness of the induction heating device (2000). In addition, in the case of driving two heating coils with a conventional single inverter including two switches, the outer heating coil must be turned on and off by a switch depending on whether the cooking container is small or large, so there was an inconvenience in that the induction heating device had to always sense the size of the cooking container. According to the resonance circuit included in the inverter of the induction heating device (2000) according to one embodiment of the present disclosure, the inner heating coil is always operated, and as the proportion of the cooking container covering the outer heating coil increases, the current flowing in the outer heating coil increases proportionally, so there is no concern about malfunction and the bottom of the cooking container can be evenly heated. In addition, in an induction heating device (2000) according to one embodiment of the present disclosure, a method is used in which two switches are cross-driven by a single inverter, so that the peak component of the input current is reduced, and thus the peak component of the current flowing to the passive elements in the EMI filter and rectifier circuit in front of the inverter is reduced, thereby minimizing circuit loss, and thus the induction heating device (2000) can be operated with high efficiency.

[0119] FIG. 11A is a waveform diagram of a current flowing in a heating coil according to a change in inductance of the outer heating coil according to one embodiment of the present disclosure.

[0120] Fig. 11a is a waveform diagram of the current flowing in the heating coil when the inductance of the first heating coil (2121), which is the inner heating coil, is fixed at 28 uH and the inductance of the second heating coil (2122), which is the outer heating coil, is 65 uH. In other words, when the size of the cooking vessel (101) is relatively small, the inductance of the second heating coil (2122) increases, and the ratio of the current flowing in the first heating coil (2121), which is the inner heating coil, and the second heating coil (2122), which is the outer heating coil, change.

[0121] Referring to Fig. 11a, it can be seen that the inductance of the second heating coil (2122), which is an outer heating coil, is relatively large at 65 uH, and therefore, the current flowing through the second heating coil (2122) is relatively small compared to the case of Fig. 11b (when the cooking vessel (101) is large).

[0122] FIG. 11b is a waveform diagram of a current flowing in a heating coil according to a change in inductance of the outer heating coil according to one embodiment of the present disclosure.

[0123] Fig. 11b is a waveform diagram of the current flowing in the heating coil when the inductance of the second heating coil (2122), which is the outer heating coil, becomes 45 uH while the inductance of the first heating coil (2121), which is the inner heating coil, is fixed at 28 uH. In other words, as the size of the cooking vessel (101) increases, the inductance of the second heating coil (2122) becomes relatively small, and the current flowing in the second heating coil (2122), which is the outer heating coil, becomes larger compared to Fig. 11a.

[0124] FIG. 12 is a graph showing the voltage gain by frequency according to the change in inductance of a heating coil according to one embodiment of the present disclosure.

[0125] Looking at Fig. 12, the inductance of the first heating coil (2121) does not change, so the voltage gain curve of the first heating coil (2121) does not change, but the inductance of the second heating coil (2122) changes depending on the size of the cooking vessel (101), so the voltage gain curve of the second heating coil (2122) changes depending on the operating frequency.

[0126] It can be seen that when a small cooking vessel is used and the inductance of the second heating coil (2122) is large and 65 uH, the voltage gain at the switching frequency is smaller than when a small cooking vessel is used and the inductance of the second heating coil (2122) is small and 45 uH.

[0127] An induction heating device (2000) according to one embodiment of the present disclosure includes a single inverter including two switching elements, and the single inverter can operate a first heating coil (2121) and a second heating coil (2122). In addition, since both the first heating coil (2121) and the second heating coil (2122) are operated synchronously at the same switching frequency, noise problems that may occur when driving a plurality of heating coils with a plurality of inverters do not occur.

[0128] Fig. 13 is an equivalent circuit of an inverter and a resonant circuit according to one embodiment of the present disclosure.

[0129] The link capacitor (2117) and the first switch (2113_1) and the second switch (2113_2) can be replaced with two voltage sources in the equivalent circuit as shown in Fig. 13.

[0130] The components that affect the current path flowing in the second heating coil (2122), which is the outer heating coil, are I_out_coil, C_out, which is the first resonant capacitor (2114a), and C_in, which is the second resonant capacitor (2114b). From the perspective of the upper voltage source (Vs / 2), C_out, which is the first resonant capacitor (2114a), and C_in, which is the second resonant capacitor (2114b), appear to be connected in series.

[0131] The components that affect the current path flowing in the first heating coil (2121), which is the inner heating coil, are I_in_coil and C_in, and the resonance point due to the current flowing in the path in which the inductance (L) and capacitance (C) are connected in series can be calculated by the mathematical formula (1) below.

[0132] ... Mathematical formula (1)

[0133] Therefore, the resonance frequency by the first heating coil (2121) is as follows:

[0134] ... Mathematical formula (2)

[0135] In mathematical expression (2), fin is the resonance frequency of the first heating coil (2121), which is the inner heating coil, Lin is the inductance of the first heating coil (2121), and Cin is the capacitance of the second resonance capacitor (2114b).

[0136] And, the resonance frequency by the second heating coil (2121) is as follows: mathematical equation (3).

[0137] ... Mathematical formula (3)

[0138] In mathematical expression (3), Lout is the inductance of the second heating coil (2122), Cout is the capacitance of the first resonant capacitor (2114a), and Cin is the capacitance of the second resonant capacitor (2114b). In the equivalent circuit of Fig. 13, the capacitance seen from the perspective of the upper voltage source (Vs / 2) is the series connection of C_out, which is the first resonant capacitor (2114a), and C_in, which is the second resonant capacitor (2114b), so the final capacitance becomes (Cout x Cin) / (Cout + Cin), as in mathematical expression (3).

[0139] If it is difficult to make the inductance value of the second heating coil (2122) through which I_out_coil flows very large, if the condition of Cout (capacitance of the first resonant capacitor (2114a)) >> Cin (capacitance of the second resonant capacitor (2114b)) is designed so that the capacitance of the capacitor connected in series by C_out, which is the first resonant capacitor (2114a), and C_in, which is the second resonant capacitor (2114b), becomes close to Cin, the burden of having to design the inductance value of the second heating coil (2122) to be extremely large compared to the first heating coil (2121) can be reduced.

[0140] In the present disclosure, one end of C_in, which is a second resonant capacitor (2114b), is connected to a point where the source of the first switch (2113_1) and the drain of the lower second switch (2113_2) meet each other, and the other end of C_in is connected to a point where the first heating coil (2121) and the second heating coil (2122) meet each other. Therefore, the resonant circuit of the inverter according to one embodiment of the present disclosure has a structure in which the first resonant capacitor (2114a) and the second resonant capacitor (2114b) are connected in series with each other.

[0141] The resonant circuit of the inverter according to one embodiment of the present disclosure is advantageous for high-frequency driving. As shown in FIG. 12, the input-output gain in the resonant circuit is 1.0. In other words, there is no amplification. As the switching frequency increases, the current induced in the cooking vessel by the magnetic field tends to flow to the surface of the cooking vessel due to the skin effect. The skin effect increases as the frequency increases. Since the current flows to the surface of the cooking vessel due to the skin effect, the cross-sectional area through which the current flows decreases, resulting in an increase in the resistance value. In the case of a high-frequency induction heating device, increasing the operating frequency increases the resistance value of the cooking vessel due to the skin effect, so that the same power can be transmitted to the cooking vessel even with a small current, thereby reducing the loss of the resonant circuit included in the inverter. P=I 2 *In the formula for R, if the resistance (R) value is doubled, to transmit the same power (P), P = (1 / √2) 2*(2R), so the current (I) can be reduced by about 30% (1 / 1.414 = 0.7). However, when the series resonant circuit according to an embodiment of the present disclosure operates in a complete resonance state, Ohm's law is established between the input voltage and the load, and when V is fixed in I = V / R, if the resistance value doubles, the current I is halved, which causes a problem in that sufficient power is not transmitted to the heating coil and the cooking vessel. In other words, compared to the method in which the induction heating device (2000) operates at a low frequency, it tries to transmit the same power to the heating coil by reducing the current by about 30%, but since the current is actually halved, there is a limit to the maximum power transmission to the heating coil. If a converter capable of amplification is used to overcome this, additional components are required, which increases the cost, and circuit loss is also induced due to unnecessary current flowing in the additional components. However, the inverter and (series) resonant circuit according to an embodiment of the present disclosure can solve this problem because they transmit power during the entire cycle of the input current. In other words, the inverter and (series) resonant circuit according to one embodiment of the present disclosure can transmit power to the heating coil during half a cycle of the input current, as seen in FIGS. 9a to 9f above, and additionally transmit power during the remaining half cycle. When the inductance of the first heating coil (2121), which is the inner heating coil, and the values ​​of the second resonant capacitor (2114b) and the inductance of the second heating coil (2122), which is the outer heating coil, and the first resonant capacitor (2114a) are appropriately adjusted, when a small cooking vessel - a cooking vessel that does not cover the second heating coil (2122) - is placed on the top plate of the induction heating device (2000), the induction heating device (2000) according to one embodiment of the present disclosure has the advantage of being able to transmit an additional 30% more power.

[0142] FIG. 14a is a circuit diagram for driving a plurality of heating coils with switches added to the outer heating coil path according to one embodiment of the present disclosure.

[0143] An inverter including a resonant circuit according to FIG. 14a is almost identical to the inverter according to FIG. 7, but has a switch (2150) in front of the first resonant capacitor (2114a). In one embodiment, if the size of the cooking vessel (101) is small and heating through the second heating coil (2122), which is an external heating coil, is not required, the processor can control the switch (2150) to be turned off, thereby blocking the operation of the second heating coil (2122). The size of the cooking vessel (101) can be determined by a sensor that detects the size of the cooking vessel (101). In one embodiment, the switch (2150) may include an electronic switch. In one embodiment, the switch (2150) may also include a relay switch.

[0144] Conversely, if the size of the cooking vessel (101) is sufficiently large that the cooking vessel (101) covers the outer heating coil, the processor of the induction heating device (2000) can control the switch (2150) to turn on so that the second heating coil (2122) can be operated.

[0145] FIG. 14b is a circuit diagram for driving a plurality of heating coils with switches added to the outer heating coil path according to one embodiment of the present disclosure.

[0146] The resonant circuit of Fig. 14b is almost identical to that of Fig. 14a, except that the switch (2150) is positioned at the rear end of the first resonant capacitor (2114a). In this way, the switch (2150) according to one embodiment of the present disclosure can be positioned at any location so long as it can operate both the first heating coil (2121) and the second heating coil (2122) when turned on, and operate only the first heating coil (2121) when turned off, and is not limited to being positioned at a specific location.

[0147] Figure 15 is a block diagram of an induction heating device according to one embodiment of the present disclosure.

[0148] As illustrated in FIG. 15, 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).

[0149] Below, we will look at the above components in turn.

[0150] The induction heating unit (2100) may include, but is not limited to, a driving unit (2110) and a heating coil (2120). The driving unit (2110) may receive power from an input power source (not shown) and supply current to the heating coil (2120) according to a driving control signal of the processor (2200). The driving unit (2110) may include, but is not limited to, an EMI filter (2111), a rectifier circuit (2112), an inverter (2113), 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. 15 may only mean a set of switching elements that perform a switching operation to supply current to the heating coil (2120). The inverter (2113) of FIG. 15 may be an inverter (2113d) according to FIG. 7 that includes only two switching elements.

[0151] The EMI filter (2111) blocks high-frequency noise included in the AC voltage supplied from the input power source 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 arranged between the EMI filter (2111) and the input power source. The AC power from which high-frequency noise has been blocked by the EMI filter (2111) is supplied to the rectifier circuit (2112).

[0152] The rectifier circuit (2112) can full-wave rectify an AC voltage. For example, the rectifier circuit (2112) can convert an AC voltage whose magnitude and polarity (positive voltage or negative voltage) change over time into a full-wave rectified voltage whose magnitude and polarity are both positive. 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 an AC voltage whose polarity changes over time into a positive voltage with a constant polarity, and can convert an AC current whose direction changes over time into a positive current with a constant direction. The voltage full-wave rectified by the rectifier circuit (2112) can maintain a constant power level so that the energy does not drop to 0 by the link capacitor, thereby reducing the switching loss of the inverter in a section where there is no energy.

[0153] The inverter (2113) may include a switching circuit that supplies or cuts off a driving current to the heating coil (2120). In a broad sense, the inverter (2113) may also include a resonant capacitor that resonates with the heating coil (2120). The switching circuit may include two switches for each burner. According to one embodiment of the present disclosure, when the burner includes a first heating coil (2121) as an inner heating coil and a second heating coil (2122) as an outer heating coil, both heating coils may be operated by the two switches. The first switch (2113_1) and the second switch (2113_2) included in the inverter (2113) 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 a driving control signal.

[0154] The inverter (2113) can control the current supplied to the heating coil (2120). For example, the magnitude and direction of the current flowing to the first heating coil (2121) and the second heating coil (2122) can change depending on the turning on / off of the first switch (2113_1) and the second switch (2113_2) included in the inverter (2113). In this case, an alternating current can be supplied to the first heating coil (2121) and the second heating coil (2122).

[0155] The current detection unit (2115) is a current sensor that measures the current output from the inverter (2113) and flowing to the heating coil (2120), and may include CT1 (2115_1) and CT2 (2115_2). The current detection unit (2115) may not necessarily be included in the induction heating device (2000). 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 heating coil (2120) in addition to the current detection unit (2115).

[0156] 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 processor (2200) can control the inverter (2113) to apply a gate signal corresponding to Gate_H to the first switch (2113_1) and a gate signal corresponding to Gate_L to the second switch (2113_2), as disclosed in 810 of FIG. 8, according to one embodiment of the present disclosure. 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).

[0157] The heating coil (2120) can generate a magnetic field for heating the cooking vessel (101). For example, when a driving current is supplied to the heating coil (2120), a magnetic field can be induced around the heating coil (2120). When a current whose size and direction change over time, i.e., an alternating current, is supplied to the heating coil (2120), a magnetic field whose size and direction change over time can be induced around the heating coil (2120). The magnetic field around the heating 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 size 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). Electrical 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 the electrical resistance heat, and the contents inside the cooking vessel (101) can be heated.

[0158] The processor (2200) can control 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) is a hardware component (chip) that includes an integrated circuit in which electrical circuits are integrated.

[0159] The processor (2200) may include various processing circuits and / or multiple processors. For example, the term “processor” as used herein, including in the claims, may include various processing circuits, including at least one processor. One or more processors in at least one processor may be configured to perform various functions described herein, individually and / or collectively, in a distributed fashion. As used herein, “processor,” “at least one processor,” and “one or more processors” may be configured to perform various functions. However, these terms encompass, without limitation, situations where one processor performs some of the functions and other processor(s) perform other parts of the functions, and situations where a single processor may perform all of the functions. Furthermore, the at least one processor may include a combination of processors that perform various functions of the disclosed functions in a distributed manner. The at least one processor may execute program instructions to achieve or perform various functions. The processor (2200) can 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) can include at least one processor. For example, the processor (2200) can be one or multiple. The induction heating device (2000) can include only a main processor, or a main processor and at least one sub-processor.

[0160] 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).

[0161] 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).

[0162] 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.

[0163] 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.

[0164] 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 an 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.

[0165] 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.

[0166] 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).

[0167] 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.

[0168] 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 a plurality of 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] According to one embodiment of the present disclosure, an induction heating device driving a plurality of heating coils with a single inverter is disclosed. According to one embodiment, the induction heating device may include a first heating coil for heating the inside of a circular burner. According to one embodiment, the induction heating device may include a second heating coil for heating the outside of the circular burner. According to one embodiment, the induction heating device may include a link capacitor for establishing a full-wave rectified voltage at both ends. According to one embodiment, the induction heating device may include a first switch and a second switch connected in series and an inverter connected in parallel with the link capacitor. According to one embodiment, the induction heating device may include a first resonant capacitor connected to a first side of the first switch and connected to a first end of the second heating coil. An induction heating device according to one embodiment may include a second resonant capacitor connected to a second side of a first switch and a first side of a second switch and connected to a second end of a second heating coil and a first end of the first heating coil. An induction heating device according to one embodiment may include a processor that controls the first switch and the second switch to be alternately turned on and off so that a magnetic field is induced in the first heating coil and the second heating coil, wherein the second side of the second switch is connected to the second end of the first heating coil.

[0173] According to one embodiment of the present disclosure, an induction heating device driving a plurality of heating coils with a single inverter further includes a rectifier circuit for rectifying an input voltage, wherein a magnetic field is induced in the first heating coil and the second heating coil during the entire cycle of the input voltage.

[0174] According to one embodiment of the present disclosure, an induction heating device driving a plurality of heating coils with a single inverter induces a magnetic field in the first heating coil and the second heating coil as input current is supplied from a link capacitor to the inverter during the entire cycle of the input voltage.

[0175] According to one embodiment of the present disclosure, an induction heating device driving a plurality of heating coils with a single inverter further includes a rectifier circuit for rectifying an input voltage, wherein an input current is supplied from a link capacitor to the inverter during a full cycle of the input voltage, and one cycle of the input current includes a first half cycle and a second half cycle, wherein energy by the input current is supplied to the first heating coil during the first half cycle, and energy by the input current is supplied to the second heating coil during the second half cycle.

[0176] According to one embodiment of the present disclosure, an induction heating device driving a plurality of heating coils with a single inverter has a peak value of input current during a first half cycle and a peak value of input current during a second half cycle that are different from each other.

[0177] According to one embodiment of the present disclosure, in an induction heating device that drives a plurality of heating coils with a single inverter, the peak value of the input current during the first half cycle and the peak value of the input current during the second half cycle can be changed by adjusting the inductance of the first heating coil and the capacitance of the second resonant capacitor, and the inductance of the second heating coil and the capacitance of the first resonant capacitor.

[0178] According to one embodiment of the present disclosure, in an induction heating device that drives a plurality of heating coils with a single inverter, when a cooking vessel is placed on a burner heated by a first heating coil and a second heating coil, the current flowing through the first heating coil and the second heating coil can be automatically adjusted according to the size of the cooking vessel.

[0179] According to one embodiment of the present disclosure, in an induction heating device that drives a plurality of heating coils with a single inverter, when the cooking vessel covers only the burner corresponding to the second heating coil, the current flowing in the second heating coil becomes maximum, and when the size of the cooking vessel does not cover the top plate area corresponding to the second heating coil, the current flowing in the first heating coil becomes maximum.

[0180] According to one embodiment of the present disclosure, in an induction heating device that drives a plurality of heating coils with a single inverter, in a first section in which the input current becomes a positive value after zero crossing, the processor controls to keep the first switch on and the second switch off, so that as current flows to the first heating coil, the second resonant capacitor is charged, and energy stored in the second heating coil is discharged to charge the first resonant capacitor.

[0181] According to one embodiment of the present disclosure, in an induction heating device that drives a plurality of heating coils with a single inverter, in a second period in which the input current maintains a positive value after a first period, the processor controls to keep the first switch on and the second switch off, while the first resonant capacitor is discharged and the second resonant capacitor is charged through the first switch.

[0182] According to one embodiment of the present disclosure, in an induction heating device that drives a plurality of heating coils with a single inverter, in a third section in which the input current becomes a negative value after zero crossing, the processor controls the first switch to turn off and the second switch to remain off, so that energy stored in the second heating coil is discharged to charge the first resonant capacitor through the anti-parallel diode of the second switch, and the input current becomes a negative value. According to one embodiment, in the third section, energy stored in the first heating coil is discharged to charge the second resonant capacitor through the anti-parallel diode of the second switch.

[0183] According to one embodiment of the present disclosure, in an induction heating device that drives a plurality of heating coils with a single inverter, in a fourth section in which the input current maintains a negative value, the processor controls the second switch to be turned on, and the first resonant capacitor is discharged and the second resonant capacitor is charged through the second switch.

[0184] According to one embodiment of the present disclosure, in an induction heating device that drives a plurality of heating coils with a single inverter, in a fifth section where the input current changes from a negative value to zero, the processor controls the second switch to remain on, while magnetic energy is charged in the first heating coil by the second capacitor.

[0185] According to one embodiment of the present disclosure, in an induction heating device that drives a plurality of heating coils with a single inverter, in a sixth section in which the input current becomes a positive value from zero crossing, the processor controls the second switch to remain on, such that the second resonant capacitor is charged by the input current and the second resonant capacitor is discharged through the second switch.

[0186] An induction heating device in which a plurality of heating coils are driven by a single inverter according to one embodiment of the present disclosure, wherein the capacitance of the first resonant capacitor is greater than the capacitance of the second resonant capacitor.

[0187] According to one embodiment of the present disclosure, an induction heating device driving a plurality of heating coils with a single inverter may further include an electronic switch disposed between a first side of a first switch and a first resonant capacitor or disposed between the first resonant capacitor and a first end of a second heating coil.

[0188] In an induction heating device driving a plurality of heating coils with a single inverter according to one embodiment of the present disclosure, the processor turns off an electronic switch when the cooking vessel covers only the burner corresponding to the first heating coil.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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. A first heating coil (2121) for heating the inside of a circular crater; A second heating coil (2122) for heating the outside of the above circular crater; A link capacitor (2117) that establishes a rectified voltage at both ends; Including an inverter (2113) connected in parallel with the link capacitor, wherein the inverter includes a first switch (2113_1) and a second switch (2113_2) connected in series with each other, A first resonant capacitor (2114a) connected to the first side of the first switch (2113_1) and connected to the first terminal of the second heating coil (2122); A second resonant capacitor (2114b) connected to the second side of the first switch (2113_1) and the first side of the second switch (2113_2) and connected to the second end of the second heating coil (2122) and the first end of the first heating coil (2121); and An induction heating device (2000) including a processor that controls the first switch (2113_1) and the second switch (2113_2) to be alternately turned on and off so that a magnetic field is induced in the first heating coil (2121) and the second heating coil (2122), wherein the second side of the second switch (2113_2) is connected to the second end of the first heating coil (2121).

2. In paragraph 1, An induction heating device in which a magnetic field is induced in the first heating coil and the second heating coil as input current is supplied from the link capacitor to the inverter during the full cycle of the input voltage input to the induction heating device.

3. In any one of paragraphs 1 to 2, One cycle of the input current includes a first half cycle and a second half cycle, wherein energy by the input current is supplied to the first heating coil during the first half cycle, and energy by the input current is supplied to the second heating coil during the second half cycle. An induction heating device, wherein the peak value of the input current during the first half cycle and the peak value of the input current during the second half cycle are different from each other.

4. In any one of paragraphs 1 to 3, An induction heating device, wherein the peak value of the input current during the first half cycle and the peak value of the input current during the second half cycle are changed by adjusting the inductance of the first heating coil and the capacitance of the second resonant capacitor, and the inductance of the second heating coil and the capacitance of the first resonant capacitor.

5. In any one of paragraphs 1 to 4, When a cooking vessel is placed on a burner heated by the first heating coil and the second heating coil, the current flowing through the first heating coil and the second heating coil is automatically adjusted according to the size of the cooking vessel. An induction heating device in which the current flowing in the second heating coil is maximum when the cooking vessel covers only the burner corresponding to the second heating coil, and the current flowing in the first heating coil is maximum when the size of the cooking vessel does not cover the top plate area corresponding to the second heating coil.

6. In any one of paragraphs 1 to 5, In the first section where the input current becomes a positive value after zero crossing, the processor controls the first switch to be kept on and the second switch to be kept off. An induction heating device in which the second resonant capacitor is charged when current flows through the first heating coil, and the energy stored in the second heating coil is discharged to charge the first resonant capacitor.

7. In any one of paragraphs 1 to 6, An induction heating device in which, in a second period after the first period, the input current maintains a positive value, the processor controls the first switch to be kept on and the second switch to be kept off, while the first resonant capacitor is discharged and the second resonant capacitor is charged through the first switch.

8. In any one of paragraphs 1 to 7, An induction heating device in which the above input current charges the second resonant capacitor.

9. In any one of paragraphs 1 to 8, In the third section where the input current becomes a negative value after zero crossing, the processor controls the first switch to turn off and the second switch to remain off. An induction heating device in which the energy stored in the second heating coil is discharged to charge the first resonant capacitor through the anti-parallel diode of the second switch, and the input current becomes a negative value.

10. In any one of paragraphs 1 to 9, An induction heating device in which energy stored in the first heating coil is discharged to charge the second resonant capacitor through the anti-parallel diode of the second switch.

11. In any one of paragraphs 1 to 10, In the fourth section where the input current maintains a negative value, the processor controls the second switch to be turned on, An induction heating device in which the first resonant capacitor is discharged and the second resonant capacitor is charged through the second switch.

12. In any one of paragraphs 1 to 11, An induction heating device in which the processor controls the second switch to remain on in the fifth section in which the input current changes from a negative value to zero, while magnetic energy is charged in the first heating coil by the second capacitor.

13. In any one of paragraphs 1 to 12, In the sixth section where the input current becomes a positive value from zero crossing, the processor controls the second switch to remain on. An induction heating device in which the second resonant capacitor is charged by the input current and the second resonant capacitor is discharged through the second switch.

14. In any one of paragraphs 1 to 13, An induction heating device, wherein the capacitance of the first resonant capacitor is greater than the capacitance of the second resonant capacitor.

15. An induction heating device according to any one of claims 1 to 14, wherein the processor controls the first switch (2113_1) and the second switch (2113_2) to be turned on and off alternately, thereby causing the second heating coil to resonate with the first resonant capacitor and the second resonant capacitor, and the first heating coil to resonate with the second resonant capacitor.

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