Induction heating apparatus and method for controlling induction heating apparatus

Abstract

A control method for an induction heating device according to one embodiment includes the steps of: starting to heat a container; obtaining an inductance value of the container; calculating an overheating determination index based on the inductance value; comparing the overheating determination index with a predetermined first reference value; and determining whether to stop heating the container based on the result of comparing the overheating determination index with the first reference value.

Description

Technology Field

[0001] This specification relates to an induction heating device and a method for controlling an induction heating device. Background Technology

[0003] An induction heating device is a device that heats a container using an induction heating method. When electrical energy is supplied to a working coil included in the induction heating device, a magnetic field is generated around the working coil. When an eddy current is generated in a container placed above the working coil by this magnetic field, the container is heated.

[0004] FIG. 1 is an exploded perspective view of a working coil assembly disposed inside an induction heating device according to one embodiment.

[0005] As illustrated in FIG. 1, a working coil assembly according to one embodiment includes a coil base (30), a first working coil (31), and a second working coil (32).

[0006] The coil base (30) is a structure for receiving and supporting the first working coil (31) and the second working coil (32). The coil base (30) has a shape (e.g., circular or square, etc.) corresponding to the first working coil (31) and the second working coil (32) and can be made of a non-conductive material.

[0007] The first working coil (31) is mounted on the upper part of the coil base (30) and wound radially for a first number of turns. Additionally, the second working coil (32) is mounted on the upper part of the coil base (30), shares a center with the first working coil (31), and is wound radially for a second number of turns. Connectors (33a, 33b) are connected to both ends of the first working coil (31), and connectors (33c, 33d) are connected to both ends of the second working coil (32). The first working coil (31) and the second working coil (32) can be electrically connected to a controller or power supply through the connectors (33a, 33b, 33c, 33d).

[0008] A receiving space is formed in the center of the coil base (30) to accommodate a temperature sensor (304) and a fuse (302).

[0009] When a container is placed on top of the first working coil (31) and the second working coil (32) and heated, the temperature of the container can be sensed through the temperature sensor (304). While the container is being heated, the temperature of the container sensed by the temperature sensor (304) is transmitted to the controller of the induction heating device. The controller stops heating the container if the temperature value of the container sensed by the temperature sensor (304) or the rate of change of the temperature value exceeds a predetermined reference value. Accidents caused by overheating of the container can be prevented by this protection logic or overheat prevention operation.

[0010] A fuse (302) is placed on one side of the temperature sensor (304). When the temperature of the fuse (302) reaches a predetermined temperature value, the fuse (302) melts and breaks. When the fuse (302) breaks, the current flow of the induction heating device is cut off, and the operation of the induction heating device is stopped. When the container is heated, if the temperature of the container increases rapidly, a failure may occur in the induction heating device or a fire may occur due to the container overheating before the primary protection logic or overheating prevention operation by the aforementioned temperature sensor (304) is performed. Therefore, a secondary protection logic or overheating prevention operation is performed using the fuse (302).

[0011] As shown in Fig. 1, if a fuse (302) is placed separately from the temperature sensor (304) inside the induction heating device, the fuse (302) blows when a secondary protection logic or overheating prevention operation is performed by the fuse (302). However, if the fuse (302) blows due to overheating, the user cannot use the induction heating device at all until the fuse (302) is replaced, which causes inconvenience to the user. The problem to be solved

[0013] The purpose of the present specification is to provide an induction heating device and a method for controlling the induction heating device that can prevent overheating of a container without having a fuse.

[0014] The purpose of the present specification is to provide an induction heating device and a control method for an induction heating device that can be operated again without repair or replacement of parts even after the heating of the container has been stopped due to overheating of the container.

[0015] The purpose of the present specification is to provide an induction heating device and a control method for the induction heating device that can prevent overheating of a container even if a malfunction occurs in the temperature sensor.

[0016] The purpose of this specification is not limited to the purposes mentioned above, and other purposes and advantages of this specification not mentioned will be more clearly understood by the embodiments of this specification described below. Furthermore, the purposes and advantages of this specification may be realized by the components and combinations thereof described in the claims. means of solving the problem

[0018] A control method for an induction heating device according to one embodiment includes the steps of: starting to heat a container; obtaining an inductance value of the container; calculating an overheating determination index based on the inductance value; comparing the overheating determination index with a predetermined first reference value; and determining whether to stop heating the container based on the result of comparing the overheating determination index with the first reference value.

[0019] In one embodiment, the step of determining whether to stop heating the container based on the result of comparing the overheating determination index and the first reference value includes the step of determining to maintain heating the container if the overheating determination index is less than the first reference value, and the step of determining to stop heating the container if the overheating determination index is greater than or equal to the first reference value.

[0020] A control method for an induction heating device according to one embodiment further includes the step of obtaining a temperature change index of the container.

[0021] In one embodiment, the step of determining whether to stop heating the container based on the result of comparing the overheating determination index and the first reference value includes: a step of determining to maintain heating the container if the overheating determination index is less than the first reference value; a step of determining to maintain heating the container if the overheating determination index is greater than or equal to the first reference value and the temperature change index exceeds a predetermined second reference value; and a step of determining to stop heating the container if the overheating determination index is greater than or equal to the first reference value and the temperature change index is less than or equal to the second reference value.

[0022] In one embodiment, the overheating determination index is a value obtained by dividing the inductance value of the container by a predetermined initial inductance value.

[0023] A control method for an induction heating device according to one embodiment further includes the step of calculating the rate of change of the inductance value and the step of changing the initial inductance value to a predetermined default value if the rate of change of the inductance value is less than or equal to a predetermined third reference value or greater than or equal to a predetermined fourth reference value.

[0024] In one embodiment, the rate of change of the inductance value is the value obtained by dividing the currently obtained inductance value by the previously obtained inductance value.

[0025] In one embodiment, the temperature change index is the average value of the temperature change rate of the container.

[0026] In one embodiment, the rate of change in the temperature of the container is the value obtained by dividing the temperature value of the container acquired in the current determination cycle by the temperature value of the container obtained in the previous determination cycle.

[0027] In one embodiment, a step of determining whether to stop heating the container is performed only when the temperature value of the container measured after the heating time of the container has reached a predetermined reference time is less than the predetermined reference temperature value.

[0028] An induction heating device according to one embodiment includes a working coil, a power supply circuit for supplying power for driving the working coil, and a controller for controlling the driving of the working coil by controlling the driving of the power supply circuit.

[0029] In one embodiment, the controller starts heating the container by driving the working coil, obtains an inductance value of the container, calculates an overheating determination index based on the inductance value, compares the overheating determination index with a predetermined first reference value, and determines whether to stop heating the container based on the result of comparing the overheating determination index with the first reference value.

[0030] In one embodiment, the controller determines to maintain heating of the container if the overheating determination index is less than the first reference value, and determines to stop heating of the container if the overheating determination index is greater than or equal to the first reference value.

[0031] In one embodiment, the controller obtains a temperature change index of the container and determines to maintain heating of the container if the overheating determination index is less than the first reference value, determines to maintain heating of the container if the overheating determination index is greater than or equal to the first reference value and the temperature change index exceeds a predetermined second reference value, and determines to stop heating of the container if the overheating determination index is greater than or equal to the first reference value and the temperature change index is less than or equal to the second reference value.

[0032] In one embodiment, the overheating determination index is a value obtained by dividing the inductance value of the container by a predetermined initial inductance value.

[0033] In one embodiment, the controller calculates the rate of change of the inductance value, and if the rate of change of the inductance value is less than or equal to a predetermined third reference value or greater than or equal to a predetermined fourth reference value, the initial inductance value is changed to a predetermined default value.

[0034] In one embodiment, the rate of change of the inductance value is the value obtained by dividing the currently obtained inductance value by the previously obtained inductance value.

[0035] In one embodiment, the temperature change index is the average value of the temperature change rate of the container.

[0036] In one embodiment, the rate of change in the temperature of the container is the value obtained by dividing the temperature value of the container acquired in the current determination cycle by the temperature value of the container obtained in the previous determination cycle.

[0037] In one embodiment, the controller determines whether to stop heating the container only when the temperature value of the container measured after the heating time of the container reaches a predetermined reference time is less than the predetermined reference temperature value. Effects of the invention

[0039] The induction heating device according to the embodiments can prevent overheating of the container without having a fuse. Therefore, the manufacturing cost of the induction heating device can be reduced. In addition, since replacement of the fuse is not required, user satisfaction with the quality of the induction heating device can be improved.

[0040] In addition, according to the embodiments, the induction heating device can be operated again without repair or replacement of parts even after the heating of the container is stopped due to overheating of the container.

[0041] In addition, the induction heating device according to the embodiments can prevent the container from overheating even if a malfunction occurs in the temperature sensor. Brief explanation of the drawing

[0043] FIG. 1 is an exploded perspective view of a working coil assembly disposed inside an induction heating device according to one embodiment. FIG. 2 is an exploded perspective view of an induction heating device according to one embodiment. FIG. 3 is a circuit diagram of an induction heating device according to one embodiment. FIG. 4 is a flowchart illustrating a control method for an induction heating device according to one embodiment. FIG. 5 is a flowchart illustrating a control method for an induction heating device according to another embodiment. FIG. 6 is a flowchart illustrating a control method for an induction heating device according to another embodiment. Specific details for implementing the invention

[0044] The aforementioned objectives, features, and advantages are described in detail below with reference to the attached drawings, and accordingly, a person skilled in the art to which this specification pertains will be able to easily implement the embodiments of this specification. In describing this specification, detailed descriptions of known technologies related to this specification are omitted if it is determined that such descriptions would unnecessarily obscure the gist of this specification. Hereinafter, preferred embodiments of this specification will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals indicate the same or similar components.

[0045] FIG. 2 is an exploded perspective view of an induction heating device according to one embodiment.

[0046] As illustrated in FIG. 2, an induction heating device (10) according to one embodiment includes a case (102) constituting the main body of the induction heating device (10) and a cover plate (104) coupled to the case (102) to seal the case (102).

[0047] The cover plate (104) is coupled with the upper surface of the case (102) to seal the space formed inside the case (102) from the outside. The cover plate (104) includes a top plate (106) on which a container for cooking food can be placed. In one embodiment, the top plate (106) may be made of a reinforced glass material such as ceramic glass. However, the material of the top plate (106) may vary depending on the embodiment.

[0048] A first heating area (12) and a second heating area (14) corresponding to the working coil assembly (122, 124) are formed on the top plate (106). In order to allow the user to clearly recognize the location of the heating areas (12, 14), lines or shapes corresponding to the heating areas (12, 14) may be printed or displayed on the top plate (106).

[0049] The case (102) may have a cuboid shape with an open top. A working coil assembly (122, 124) for heating a container is disposed in a space formed inside the case (102). Additionally, an interface unit (114) (or interface) is provided inside the case (102) to have a function that allows a user to apply power or adjust the power level of each heating area (12, 14), and a function that displays information related to the induction heating device (10). The interface unit (114) may be a touch panel capable of both inputting information and displaying information by touch. However, depending on the embodiment, the interface unit (114) may be implemented as a different device or structure.

[0050] Additionally, the top plate (106) is provided with an operation area (118) positioned at a location corresponding to the interface section (114). For user operation, characters or images may be pre-printed in the operation area (118). The user can perform a desired operation by touching a specific point in the operation area (118) while referring to the characters or images pre-printed in the operation area (118). Additionally, information output by the interface section (114) may be displayed through the operation area (118).

[0051] The user can set the power level of each heating area (12, 14) through the interface section (114). The power level may be displayed as a number (e.g., 1, 2, 3, ..., 9) on the operation area (118). Once the power level for each heating area (12, 14) is set, the required power value and heating frequency of the working coil corresponding to each heating area (12, 14) are determined. A controller (not shown) drives each working coil based on the determined heating frequency so that the actual output power value of each working coil matches the required power value set by the user.

[0052] In addition, a power supply unit (112) for supplying power to the first working coil assembly (122), the second working coil assembly (124), and the interface unit (114) is disposed in the space formed inside the case (102).

[0053] For reference, in the embodiment of FIG. 2, two working coil assemblies, namely the first working coil assembly (122) and the second working coil assembly (124), are exemplarily shown placed inside the case (102), but depending on the embodiment, three or more working coil assemblies may be placed inside the case (102).

[0054] The working coil assembly (122, 124) includes a working coil that forms an induced magnetic field using a high-frequency alternating current supplied by a power supply unit (112) and an insulating sheet to protect the coil from heat generated by the container. For example, in FIG. 2, the first working coil assembly (122) includes a first working coil (132) and a first insulating sheet (130) for heating a container placed in a first heating area (12). Additionally, the second working coil (124) includes a second working coil (142) and a first insulating sheet (140) for heating a container placed in a second heating area (14). Depending on the embodiment, an insulating sheet may not be provided.

[0055] In addition, a temperature sensor is placed at the center of each working coil (132, 142). For example, in FIG. 2, a temperature sensor (134) is placed at the center of the first working coil (134), and a second temperature sensor (144) is placed at the center of the second working coil (142). The temperature sensor measures the temperature of the container placed in each heating area. In one embodiment, the temperature sensor may be a thermistor having a variable resistor whose resistance value changes according to the temperature of the container, but is not limited thereto.

[0056] In one embodiment, the temperature sensor outputs a sensing voltage corresponding to the temperature of the container, and the sensing voltage output from the temperature sensor is transmitted to a controller. The controller checks the temperature of the container based on the magnitude of the sensing voltage output from the temperature sensor, and if the temperature value of the container or the rate of change of temperature is greater than or equal to a predetermined reference value, it performs an overheating prevention operation by lowering the output power value of the working coil or stopping the operation of the working coil.

[0057] In addition, although not shown in FIG. 2, a circuit board on which a plurality of circuits or components including a controller are mounted may be placed in the space formed inside the case (102).

[0058] The controller can perform a heating operation by driving each working coil (132, 142) according to a user's heating start command input through the interface unit (114). When the user inputs a heating end command through the interface unit (114), the controller can stop driving the working coils (132, 142) to end the heating operation.

[0059] FIG. 3 is a circuit diagram of an induction heating device according to one embodiment.

[0060] As illustrated in FIG. 3, an induction heating device (10) according to one embodiment includes a rectifier circuit (202), a smoothing circuit (L1, C1), an inverter circuit (204), a working coil (132), a controller (2), and a driving circuit (22).

[0061] The rectifier circuit (202) includes a plurality of diode elements (D1, D2, D3, D4). The rectifier circuit (202) may be a bridge diode circuit, or may be a different circuit depending on the embodiment. The rectifier circuit (202) rectifies an AC input voltage supplied from a power supply device (20) and outputs a voltage having a pulsating waveform.

[0062] The smoothing circuit (L1, C1) smooths the voltage rectified by the rectifier circuit (32) and outputs a DC link voltage. The smoothing circuit (L1, C1) includes a first inductor (L1) and a DC link capacitor (C1).

[0063] The voltage sensor (212) senses the magnitude of the voltage output from the DC link capacitor (C1) and transmits the sensed voltage value to the controller (2).

[0064] The current sensor (214) senses the magnitude of the current output from the inverter circuit (204) and transmits the sensed current value to the controller (2).

[0065] The controller (2) can calculate the inductance value of the container using the voltage value measured by the voltage sensor (212) and the current value measured by the current sensor (214) when the container is heated. The controller (2) can perform an overheating prevention operation to prevent the container from overheating based on the calculated inductance value. In addition, the controller (2) can perform an overheating prevention operation to prevent the container from overheating based on the temperature value or the rate of change of the temperature value measured by the temperature sensor (134) shown in FIG. 2.

[0066] The inverter circuit (204) includes a first switching element (SW1), a second switching element (SW2), a third switching element (SW3), and a fourth switching element (SW4).

[0067] In the embodiment of FIG. 3, the inverter circuit (204) of the induction heating device (10) is configured as a full bridge circuit including four switching elements (SW1, SW2, SW3, SW4). However, in other embodiments, the inverter circuit (204) may be a half bridge circuit including two switching elements.

[0068] The rectifier circuit (202), smoothing circuit (L1, C1), and inverter circuit (204) may be referred to as a power supply circuit. That is, the power supply circuit may include the rectifier circuit (202), the smoothing circuit (L1, C1), and the inverter circuit (204).

[0069] The first switching element (SW1), the second switching element (SW2), the third switching element (SW3), and the fourth switching element (SW4) are each turned on and turned off by the first switching signal (S1), the second switching signal (S2), the third switching signal (S3), and the fourth switching signal (S4), respectively. Each switching element (SW1, SW2, SW3, SW4) is turned on when each switching signal (S1, S2, S3, S4) is at a high level and is turned off when each switching signal (S1, S2, S3, S4) is at a low level.

[0070] FIG. 4 illustrates an embodiment in which each switching element (SW1, SW2, SW3, SW4) is an IGBT element, but each switching element (SW1, SW2, SW3, SW4) may be a different type of switching element (e.g., BJT or FET, etc.) depending on the embodiment.

[0071] Any of the switching elements among each switching element (SW1, SW2, SW3, SW4) can be turned on and turned off alternately. For example, while the first switching element (SW1) is turned on (turned off), the second switching element (SW2) can be turned off (turned on).

[0072] Any of the switching elements among each switching element (SW1, SW2, SW3, SW4) can be turned on and turned off at the same time as each other. For example, the first switching element (SW1) can be turned on and turned off at the same timing as the third switching element (SW3).

[0073] By the turn-on and turn-off operations, i.e., the switching operations, of the switching elements (SW1, SW2, SW3, SW4) included in the inverter circuit (204), the DC link voltage input to the inverter circuit (204) is converted into AC current. The AC current converted by the inverter circuit (204) is supplied to the working coil (132).

[0074] In this specification, the first switching signal (S1), the second switching signal (S2), the third switching signal (S3), and the fourth switching signal (S4) are each Pulse Width Modulation (PWM) signals having a predetermined duty cycle.

[0075] When alternating current output from the inverter circuit (204) is supplied to the working coil (132), the working coil (132) is driven. When the working coil (132) is driven, eddy current flows through the container placed on top of the working coil (132), and the container is heated. When the working coil (132) is driven, the amount of thermal energy supplied to the container varies according to the amount of power actually generated by the driving of the working coil, that is, the actual output power value of the working coil.

[0076] When the user operates the interface of the induction heating device (10) to change the induction heating device (10) to a Power On state, power is supplied to the induction heating device from the input power source (20), and the induction heating device enters a standby state. Subsequently, the user places a container on the working coil of the induction heating device and sets the power level for the container, thereby inputting a heating start command for the working coil. When the user inputs the heating start command, the power value required for the working coil (132), i.e., the required power value, is determined according to the power level set by the user.

[0077] When a heating start command is input, the controller (2) determines a frequency corresponding to the required power value of the working coil (132), i.e., a heating frequency, and supplies a control signal corresponding to the determined heating frequency to the driving circuit (22). Accordingly, switching signals (S1, S2, S3, S4) are output from the driving circuit (22), and the working coil (132) is driven as the switching signals (S1, S2, S3, S4) are input to the switching elements (SW1, SW2, SW3, SW4), respectively. When the working coil (132) is driven, eddy currents flow through the container, and the container is heated.

[0078] In one embodiment, the controller (2) determines a heating frequency that corresponds to a power level set by the user for the heating area. For example, when the user sets a power level for the heating area, the controller (2) can gradually lower the driving frequency of the inverter circuit (204) until the output power value of the working coil (132) matches the required power value corresponding to the power level set by the user, while the driving frequency of the inverter circuit (204) is set to a predetermined reference frequency. The controller (2) can determine the frequency at which the output power value of the working coil (132) matches the required power value as the heating frequency.

[0079] The controller (2) supplies a control signal corresponding to a determined heating frequency to the driving circuit (22). Based on the control signal output from the controller (2), the driving circuit (22) outputs a switching signal (S1, S2, S3, S4) having a duty ratio corresponding to the heating frequency determined by the controller (2). Upon input of the switching signal (S1, S2, S3, S4), the switching elements (SW1, SW2, SW3, SW4) are turned on and off complementarily, and an alternating current is supplied to the working coil (132).

[0080] Meanwhile, as described above, in order for the controller (2) to determine the heating frequency, the actual output power value of the working coil (132) must be calculated while the working coil (132) is driven. In one embodiment, the controller (2) can calculate the output power value of the working coil (132) based on the magnitude of the output voltage of the DC link capacitor (C1) measured by the voltage sensor (212), i.e., the DC link voltage value, and the magnitude of the output current of the inverter circuit (204) measured by the current sensor (214), i.e., the output current value of the inverter circuit (204).

[0081] In order to accurately calculate the output power value of the working coil (132) while the working coil (132) is driven, the magnitude of the voltage input to the working coil (132) and the magnitude of the current input to the working coil (132) are each required.

[0082] The magnitude of the current input to the working coil (132) is substantially the same as the magnitude of the current output from the inverter circuit (204), that is, the output current value of the inverter circuit (204).

[0083] In one embodiment, the magnitude of the voltage input to the working coil (132) is substantially the same as the magnitude of the voltage output from the inverter circuit (204), that is, the output voltage value of the inverter circuit (204). In one embodiment, the output voltage value of the inverter circuit (204) can be calculated based on a DC link voltage function and a switching function of the inverter circuit (204).

[0084] FIG. 4 is a flowchart illustrating a control method for an induction heating device according to one embodiment.

[0085] When the user inputs a heating start command, the controller (2) drives the working coil (132). Accordingly, the heating of the container begins (402).

[0086] When heating of the container begins, the controller (2) obtains the inductance value of the container (404). In one embodiment, the controller (2) can calculate the inductance value of the container using the voltage value measured by the voltage sensor (212) and the current value measured by the current sensor (214).

[0087] For example, the controller (2) can calculate the inductance value of the container based on [Equation 1].

[0089]

[0091] In [Equation 1], Leq is the inductance value of the container, ω=2πf (f is the heating frequency), and Ceq is the capacitance value of the container. Also, Z (impedance value of the container) can be calculated by [Equation 2], and R (resistance value of the container) can be calculated by [Equation 3].

[0093]

[0095]

[0097] In [Equation 2] and [Equation 3], Vin is a voltage value measured by the voltage sensor (212), Iin is a current value measured by the current sensor (214), and Ipeak is the peak value (or maximum value) of the current value measured by the current sensor (214).

[0098] The method of calculating the inductance value based on [Equation 1] to [Equation 3] is merely one example, and the controller (2) may also calculate the inductance value of the container based on other known methods.

[0099] When the inductance value is obtained in step (404), the controller (2) calculates an overheating determination index (406). In one embodiment, the controller (2) can calculate the overheating determination index based on [Equation 4].

[0101]

[0103] In [Equation 4], Leq_critical is the overheating judgment index, Leq is the inductance value of the container, and Leq_init is the initial inductance value.

[0104] In one embodiment, the initial inductance value is a predetermined value and may be set differently depending on the embodiment.

[0105] When an overheating detection index is calculated in step (406), the controller (2) compares the overheating detection index with a predetermined first reference value (408). The controller (2) determines whether to stop heating the container based on the result of the comparison in step (408).

[0106] If the overheating determination index is less than the first reference value, the controller (2) determines that the container is not overheated and decides to maintain the heating of the container. Accordingly, the controller (2) performs step (404) again.

[0107] If the overheating determination index is greater than or equal to the first reference value, the controller (2) determines that the container is overheated and decides to stop heating the container. Accordingly, the controller (2) stops the operation of the working coil (132), thereby stopping the heating of the container (410). Even if the heating of the container is stopped in step (410), the user can operate the induction heating device again without replacing or repairing parts of the induction heating device.

[0108] In one embodiment, the first reference value can be set according to [Equation 5].

[0110]

[0112] In [Equation 5], Leq_standard is the first reference value and Leq_init is a predetermined initial inductance value. In [Equation 5], 1.2 is an exemplary value and may be set differently depending on the embodiment.

[0113] FIG. 5 is a flowchart illustrating a control method for an induction heating device according to another embodiment.

[0114] When the user inputs a heating start command, the controller (2) drives the working coil (132). Accordingly, the heating of the container begins (502).

[0115] When heating of the container begins, the controller (2) obtains the inductance value of the container (504). In one embodiment, the controller (2) can calculate the inductance value of the container using the voltage value measured by the voltage sensor (212) and the current value measured by the current sensor (214). For example, the controller (2) can calculate the inductance value of the container based on [Equation 1].

[0116] When the inductance value is obtained in step (504), the controller (2) calculates an overheating determination index (506). In one embodiment, the controller (2) can calculate the overheating determination index based on [Equation 4].

[0117] When an overheating detection index is calculated in step (506), the controller (2) compares the overheating detection index with a predetermined first reference value (508).

[0118] If the overheating determination index is less than the first reference value, the controller (2) determines that the container is not overheated and decides to maintain the heating of the container. Accordingly, the controller (2) performs step (504) again.

[0119] If the overheating detection index is greater than or equal to the first reference value, the controller (2) obtains the temperature change index of the container (510). In one embodiment, the controller (2) can calculate the temperature change index of the container based on [Equation 6].

[0121]

[0123] In [Equation 6], Ts_gradient_avg is the temperature change index, n is the number of temperature values ​​measured by the temperature sensor (134), Ts(n) is the currently measured temperature value, and Ts(n-1) is the previously measured temperature value. According to [Equation 6], the temperature change index can also be defined as the average value of the temperature change rate (the value obtained by dividing the currently measured temperature value by the previously measured temperature value).

[0124] When a temperature change index is obtained in step (510), the controller (2) compares the temperature change index with a predetermined second reference value (512). The second reference value is a predetermined value (e.g., 1) and can be set differently depending on the embodiment.

[0125] If the temperature change index exceeds the second reference value, the controller (2) determines that the container is not overheated and decides to maintain the heating of the container. Accordingly, the controller (2) performs step (504) again.

[0126] If the temperature change index is below the second reference value, the controller (2) determines that the container is overheated and decides to stop heating the container. Accordingly, the controller (2) stops the operation of the working coil (132), thereby stopping the heating of the container (514). Even if the heating of the container is stopped in step (514), the user can operate the induction heating device again without replacing or repairing parts of the induction heating device.

[0127] FIG. 6 is a flowchart illustrating a control method for an induction heating device according to another embodiment.

[0128] When the user inputs a heating start command, the controller (2) drives the working coil (132). Accordingly, the heating of the container begins (602).

[0129] When heating of the container begins, the controller (2) checks whether the value of the END flag stored in the memory device (e.g., volatile memory or non-volatile memory) is the first value (e.g., SET) (604).

[0130] In one embodiment, a memory device included in an induction heating device stores an END flag, which is a variable indicating whether an overheating prevention operation based on an inductance value is performed. When the value of the END flag is set to a first value (e.g., SET), steps (606) through (622) illustrated in FIG. 6 are not performed. When the value of the END flag is set to a second value (e.g., CLR), steps (606) through (622) are performed, thereby performing an overheating prevention operation based on an inductance value.

[0131] In one embodiment, when heating of the container begins, the END flag may be set to a second value. In other words, the initial value of the END flag may be the second value.

[0132] If the value of the END flag in step (604) is the first value, the controller (2) does not perform steps (606) through (622).

[0133] If the value of the END flag in step (604) is not the first value, the controller (2) checks whether the heating time of the container is less than a predetermined reference time (e.g., 60 seconds) (606). In one embodiment, the heating time of the container refers to the time elapsed since the heating of the container began.

[0134] If the heating time of the container in step (606) is less than the reference time, steps (608) to (622) are not performed.

[0135] In step (606), if the heating time of the container is longer than the reference time, that is, if the heating time of the container reaches the reference time, the controller (2) checks whether the temperature value of the container measured by the temperature sensor (134) is less than a predetermined reference temperature value (e.g., 55℃) (608).

[0136] If the temperature value of the container confirmed in step (608) is greater than or equal to the reference temperature value, the controller (2) changes the value of the END flag stored in the memory device to the first value (e.g., SET) (610), and step (612) is performed.

[0137] If the temperature value of the container confirmed in step (608) is less than the reference temperature value, step (612) is performed.

[0138] In step (612), the controller (2) obtains the inductance value of the container, calculates the rate of change of the inductance value of the container, and checks whether the calculated rate of change of the inductance value exceeds a predetermined third reference value and is less than a predetermined fourth reference value.

[0139] In one embodiment, the controller (2) can calculate the rate of change of the inductance value of the container based on [Equation 7].

[0141]

[0143] In [Equation 7], ΔLeq is the rate of change of the container's inductance value, Leq(n-1) is the previously obtained container's inductance value, and Leq(n) is the currently obtained container's inductance value.

[0144] If the rate of change of the inductance value of the container confirmed in step (612) is less than or equal to the third reference value or greater than or equal to the fourth reference value, the controller (2) changes the initial inductance value (Leq_init) to a predetermined default value (Leq(0)) (614), and step (616) is performed. In one embodiment, the initial inductance value is a predetermined value and may be set differently depending on the embodiment. In one embodiment, the default value (Leq(0)) is a predetermined value and may be set differently depending on the embodiment.

[0145] If the rate of change of the inductance value of the container confirmed in step (612) exceeds the third reference value and is less than the fourth reference value, step (616) is performed.

[0146] In step (616), the controller (2) calculates an overheating detection index (Leq_critical) and compares the overheating detection index with a predetermined first standard value (Leq_standard) (616). In one embodiment, the controller (2) may calculate the overheating detection index based on [Equation 4]. In one embodiment, the first standard value may be set according to [Equation 5].

[0147] In step (616), if the overheating determination index is less than the first reference value, the controller (2) determines that the container is not overheated and decides to maintain the heating of the container. Accordingly, steps (618) to (622) are not performed.

[0148] If the overheating detection index in step (616) is greater than or equal to the first reference value, the controller (2) obtains the temperature change index of the container and compares the temperature change index with a predetermined second reference value (e.g., 1). In one embodiment, the controller (2) can calculate the temperature change index of the container based on [Equation 6].

[0149] When the temperature change index exceeds the second reference value, the controller (2) determines that the container is not overheated and decides to maintain the heating of the container. Accordingly, the controller (2) sets the END flag to the first value (e.g., SET) (620), and the container continues to be heated.

[0150] If the temperature change index is below the second reference value, the controller (2) determines that the container is overheated and decides to stop heating the container. Accordingly, the controller (2) stops the operation of the working coil (132), thereby stopping the heating of the container (622). Even if the heating of the container is stopped in step (622), the user can operate the induction heating device again without replacing or repairing parts of the induction heating device.

[0151] According to the embodiments described above, the controller (2) determines whether the container is overheated based on an overheating determination index calculated based on the inductance value of the container. As the temperature of the container rises, the inductance value of the container rises. Therefore, the controller (2) can determine whether the container is overheated by monitoring the inductance value of the container.

[0152] According to the embodiments described above, the controller (2) determines whether the container is overheated based on an overheating determination index calculated based on the inductance value of the container, and stops heating the container if it is determined that the container is overheated. Therefore, even in situations where the temperature of the container rises rapidly or an abnormality occurs in the temperature sensor (134) and the overheating prevention operation based on the temperature value measured by the temperature sensor (134) cannot be properly performed, the overheating prevention operation can be performed.

[0153] In addition, according to the aforementioned embodiments, a fuse for overheat prevention operation is not required, so the manufacturing cost of the induction heating device can be reduced.

[0154] In addition, according to the embodiments described above, even if the container overheats and the heating of the container is stopped, the induction heating device can be operated again without replacing or repairing specific parts. Therefore, the user can use the induction heating device more conveniently.

[0155] Although the present specification has been described above with reference to the illustrative drawings, the present specification is not limited by the embodiments and drawings disclosed herein, and various modifications may be made by those skilled in the art. Furthermore, even if the effects according to the configuration of the present specification were not explicitly described while explaining the embodiments of the present specification above, the effects predictable by said configuration should also be acknowledged.

Claims

Claim 1 A control method for an induction heating device comprising: a step of starting to heat a container; a step of obtaining an inductance value of the container; a step of calculating an overheating determination index based on the inductance value; a step of comparing the overheating determination index with a predetermined first reference value; and a step of determining whether to stop heating the container based on the result of comparing the overheating determination index with the first reference value. Claim 2 A control method for an induction heating device according to claim 1, wherein the step of determining whether to stop heating the container based on the result of comparing the overheating determination index and the first reference value comprises: a step of determining to maintain heating of the container if the overheating determination index is less than the first reference value; and a step of determining to stop heating of the container if the overheating determination index is greater than or equal to the first reference value. Claim 3 A control method for an induction heating device according to claim 1, further comprising the step of obtaining a temperature change index of the container, and the step of determining whether to stop heating the container according to the result of comparing the overheating determination index and the first reference value comprises: a step of determining to maintain heating of the container if the overheating determination index is less than the first reference value; a step of determining to maintain heating of the container if the overheating determination index is greater than or equal to the first reference value and the temperature change index exceeds a predetermined second reference value; and a step of determining to stop heating of the container if the overheating determination index is greater than or equal to the first reference value and the temperature change index is less than or equal to the second reference value. Claim 4 A control method for an induction heating device according to claim 1, wherein the overheating determination index is a value obtained by dividing the inductance value of the container by a predetermined initial inductance value. Claim 5 A control method for an induction heating device according to claim 3, further comprising: a step of calculating the rate of change of the inductance value; and a step of changing the initial inductance value to a predetermined default value if the rate of change of the inductance value is less than or equal to a predetermined third reference value or greater than or equal to a predetermined fourth reference value. Claim 6 A control method for an induction heating device according to claim 5, wherein the rate of change of the inductance value is the value obtained by dividing the currently obtained inductance value by the previously obtained inductance value. Claim 7 A control method for an induction heating device according to paragraph 3, wherein the temperature change index is the average value of the temperature change rate of the container, and the temperature change rate of the container is the value obtained by dividing the currently obtained temperature value of the container by the previously obtained temperature value of the container. Claim 8 A control method for an induction heating device according to claim 1, wherein the step of determining whether to stop heating the container is performed only when the temperature value of the container measured after the heating time of the container has reached a predetermined reference time is less than the predetermined reference temperature value. Claim 9 An induction heating device comprising: a working coil; a power supply circuit for supplying power for driving the working coil; and a controller for controlling the driving of the working coil by controlling the driving of the power supply circuit, wherein the controller starts heating a container by driving the working coil, obtains an inductance value of the container, calculates an overheating determination index based on the inductance value, compares the overheating determination index with a predetermined first reference value, and determines whether to stop heating the container according to the result of comparing the overheating determination index with the first reference value. Claim 10 An induction heating device according to claim 9, wherein the controller determines to maintain heating of the container if the overheating determination index is less than the first reference value, and determines to stop heating of the container if the overheating determination index is greater than or equal to the first reference value. Claim 11 An induction heating device according to claim 9, wherein the controller obtains a temperature change index of the container, determines to maintain heating of the container if the overheating determination index is less than the first reference value, determines to maintain heating of the container if the overheating determination index is greater than or equal to the first reference value and the temperature change index exceeds a predetermined second reference value, and determines to stop heating of the container if the overheating determination index is greater than or equal to the first reference value and the temperature change index is less than or equal to the second reference value. Claim 12 In claim 9, the induction heating device wherein the overheating determination index is the value obtained by dividing the inductance value of the container by a predetermined initial inductance value. Claim 13 An induction heating device according to claim 11, wherein the controller calculates the rate of change of the inductance value and changes the initial inductance value to a predetermined default value if the rate of change of the inductance value is less than or equal to a predetermined third reference value or greater than or equal to a predetermined fourth reference value. Claim 14 In paragraph 13, the rate of change of the inductance value is the value obtained by dividing the currently obtained inductance value by the previously obtained inductance value. Claim 15 In claim 11, the temperature change index is the average value of the temperature change rate of the container, and the temperature change rate of the container is the value obtained by dividing the currently obtained temperature value of the container by the previously obtained temperature value of the container. Claim 16 In claim 11, the induction heating device wherein the controller determines whether to stop heating the container only when the temperature value of the container measured after the heating time of the container has reached a predetermined reference time is less than a predetermined reference temperature value.

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