Induction heating device and control method of an induction heating device

Abstract

The present application relates to an induction heating device and a control method of the induction heating device. In the present application, if a user changes a required power value of a first work coil or a second work coil to a third required power value, a controller determines a third drive frequency corresponding to the third required power value. The controller of an embodiment of the present application calculates a difference between a drive frequency of a work coil whose required power value is not changed and the third drive frequency, and compares the calculated difference with a first reference range set in advance. If the calculated difference is included in the first reference range, the controller changes an operation mode or a power control mode of a first inverter circuit or a second inverter circuit, and changes an output power value of a work coil whose required power value is changed to the third required power value.

Description

TECHNICAL FIELD

[0001] The present application relates to an induction heating apparatus and a control method of an induction heating apparatus. BACKGROUND

[0002] An induction heating apparatus is a device that generates eddy current in a container of a metal material to heat the container using a magnetic field generated around a work coil. If the induction heating apparatus is driven, a high-frequency current is applied to the work coil. Thereby, an induction magnetic field is generated around the work coil disposed inside the induction heating apparatus. If the magnetic lines of the induction magnetic field generated as described above pass through the bottom of the container containing a metal component placed on the upper portion of the work coil, eddy current is generated inside the bottom of the container. If the eddy current thus generated flows through the container, the container itself is heated.

[0003] The induction heating apparatus can include two or more heating regions and two or more work coils corresponding thereto. For example, if a user places containers in two heating regions and inputs a heating start instruction, the respective work coils are driven at a driving frequency corresponding to a required power value set by the user.

[0004] Figure 1 is a graph showing resonance characteristic curves of the respective work coils when the induction heating apparatus including two work coils is driven.

[0005] In Figure 1 , resonance characteristic curves of the respective work coils (i.e., a resonance characteristic curve 31 of a first work coil and a resonance characteristic curve 32 of a second work coil) when the two work coils are driven, respectively, in a state in which a container is placed in each of the heating regions of the induction heating apparatus are shown. The resonance frequency of the first work coil is fr1, and the resonance frequency of the second work coil is fr2.

[0006] In Figure 1 , a first required power value of the first work coil is P1, and a required power value of the second work coil is P2. Accordingly, the first work coil is driven at a first driving frequency f1 corresponding to the first required power value P1, and the second work coil is driven at a second driving frequency f2 corresponding to the second required power value P2.

[0007] As Figure 1 indicated in , if the difference f2-f1 in the driving frequencies of the respective work coils is in an audible sound band (for example, 2 kHz ~ 20 kHz) when the two work coils are simultaneously driven, interference noise caused by the driving of the work coils can be generated. Such interference noise can cause great inconvenience to a user using the induction heating apparatus, and can also become a cause for the user to suspect that the induction heating apparatus has a malfunction.

[0008] According to an unfavorable configuration, the driving frequency of at least one of the two work coils is arbitrarily adjusted so as to deviate the difference f2-f1 of the driving frequencies of the respective work coils from the audible sound frequency band. However, if the driving frequency of the work coil is arbitrarily adjusted in order to reduce the interference noise, there is a problem that the output power value of the work coil does not coincide with the required power value set by the user. SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] An object of the present invention is to provide an induction heating device and a control method thereof, which can prevent the interference noise caused by the driving of the work coil while maintaining the output power value of the work coil as the same as the required power value when the two work coils are simultaneously driven.

[0011] In addition, an object of the present invention is to provide an induction heating device and a control method thereof, which can prevent the interference noise caused by the driving of the work coil when heating a plurality of kinds of containers having different characteristics from each other.

[0012] The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned can be understood by persons skilled in the art from the following description, and will be further clearly understood by the embodiments of the present invention. In addition, the objects and advantages of the present invention can be easily achieved by the methods expressed in the claims and combinations thereof.

[0013] TECHNICAL SOLUTION TO THE PROBLEM

[0014] An induction heating device according to an embodiment of the present invention includes a first work coil and a second work coil. The first work coil is driven at a first driving frequency corresponding to a first required power value set by a user, and the second work coil is driven at a second driving frequency corresponding to a second required power value set by the user.

[0015] If the user changes the required power value of the first work coil or the second work coil to a third required power value, the controller determines a third driving frequency corresponding to the third required power value. For example, if the user changes the required power value of the second work coil to a third required power value, the driving frequency of the second work coil needs to be changed to the third driving frequency.

[0016] However, if the second working coil is driven at the third drive frequency, interference noise caused by the first working coil and the second working coil can be generated. Therefore, the controller calculates a difference between the drive frequency of the working coil (for example, the first working coil) for which the requested power value is not changed and the third drive frequency, and compares the calculated difference with a first reference range (for example, 5 kHz or more and 20 kHz or less) set in advance.

[0017] The calculated difference being included in the first reference range means that interference noise caused by the first working coil and the second working coil is generated. Therefore, in order to prevent the interference noise, the controller changes the operation mode of the first inverter circuit or the second inverter circuit, or changes the power control mode.

[0018] The controller changes the operation mode of the first inverter circuit or the second inverter circuit from the full-bridge mode to the half-bridge mode. If the operation mode of the first inverter circuit or the second inverter circuit is changed to the half-bridge mode, the output power value of the first working coil or the second working coil is reduced over the entire frequency band. Thereby, the difference between the drive frequency of the first working coil and the drive frequency of the second working coil will be greater than the boundary value (for example, 20 kHz) of the audible sound frequency band. By such control, interference noise caused by the driving of the working coil is prevented.

[0019] The controller changes the power control mode of the first inverter circuit or the second inverter circuit to either one of the asymmetric pulse width modulation mode and the phase shift mode. In an embodiment of the present application, if the operation mode of the working coil for which the requested power value is changed is the half-bridge mode, the controller changes the power control mode to the asymmetric pulse width modulation mode, and if the operation mode of the working coil for which the requested power value is changed is the full-bridge mode, the controller changes the power control mode to either one of the asymmetric pulse width modulation mode and the phase shift mode.

[0020] If the power control mode of the first inverter circuit or the second inverter circuit is changed to either one of the asymmetric pulse width modulation mode and the phase shift mode, the output power value of the first working coil or the second working coil can be adjusted without changing the drive frequency of the first working coil or the second working coil. Therefore, even if the output power value of the first working coil or the second working coil is adjusted to be the same as the third requested power value, interference noise caused by the driving of the working coil can be prevented.

[0021] The induction heating device of one embodiment of the present application includes a first work coil, a first inverter circuit that supplies current to the first work coil at a first drive frequency corresponding to a first required power value of the first work coil, a second work coil, a second inverter circuit that supplies current to the second work coil at a second drive frequency corresponding to a second required power value of the second work coil, and a controller that, if the required power value of the first work coil or the second work coil is changed to a third required power value, determines a third drive frequency corresponding to the third required power value, calculates a difference between the drive frequency of the work coil whose required power value is not changed and the third drive frequency, changes an operation mode or a power control mode of the first inverter circuit or the second inverter circuit if the difference is included in a first reference range set in advance, and changes an output power value of the work coil whose required power value is changed to the third required power value.

[0022] If the resonance frequency of the first work coil is smaller than the resonance frequency of the second work coil and the difference is included in the first reference range set in advance, the controller changes the operation mode of the first inverter circuit to a half-bridge mode and changes the drive frequency of the first inverter circuit to a fourth drive frequency corresponding to the third required power value.

[0023] The first inverter circuit includes a variable capacitor circuit and a relay circuit connected to the variable capacitor circuit, and the controller sets a capacitance value of the variable capacitor circuit to Cr,h of [Formula 1] below by turning on or off a plurality of relays included in the relay circuit.

[0024] [Formula 1]

[0025]

[0026] (where fr,h is a value identical to the frequency of a switching signal input to the second inverter circuit, and Lr is an inductance value of a second inductor included in the second inverter circuit)

[0027] After the drive frequency of the first inverter circuit is changed to the fourth drive frequency, the controller changes the power control mode of the first inverter circuit to an asymmetric pulse width modulation mode.

[0028] If the resonance frequency of the first operating coil and the resonance frequency of the second operating coil are the same and the difference value is included in a first reference range set in advance, the controller changes the power control mode of the operating coil of the requested power value to either one of an asymmetric pulse width modulation mode and a phase shift mode, and adjusts the output power value of the operating coil of the requested power value to be the same as the third requested power value according to the power control mode.

[0029] If the operation mode of the operating coil of the requested power value is a half bridge mode, the controller changes the power control mode to the asymmetric pulse width modulation mode, and if the operation mode of the operating coil of the requested power value is a full bridge mode, the controller changes the power control mode to either one of the asymmetric pulse width modulation mode and the phase shift mode.

[0030] If the power control mode is set to the asymmetric pulse width modulation mode, the controller changes the output power value of the operating coil of the requested power value to the third requested power value by adjusting the duty ratio of a switching signal for driving the operating coil of the requested power value.

[0031] If the power control mode is set to the phase shift mode, the controller changes the output power value of the operating coil of the requested power value to the third requested power value by adjusting the phase difference between a plurality of switching signals for driving the operating coil of the requested power value.

[0032] In addition, the control method of the induction heating device of an embodiment of the present application includes the steps of driving the first operating coil at a first driving frequency corresponding to a first requested power value, driving the second operating coil at a second driving frequency corresponding to a second requested power value, determining a third driving frequency corresponding to a third requested power value if the requested power value of the first operating coil or the second operating coil is changed to the third requested power value, calculating a difference value of the driving frequency of the operating coil of which the requested power value is not changed and the third driving frequency, changing the operation mode or the power control mode of a first inverter circuit supplying current to the first operating coil or a second inverter circuit supplying current to the second operating coil if the difference value is included in a first reference range set in advance, and changing the output power value of the operating coil of the requested power value to the third requested power value.

[0033] The step of changing the operation mode or the power control mode of the first inverter circuit or the second inverter circuit includes a step of changing the operation mode of the first inverter circuit to a half-bridge mode if the resonance frequency of the first work coil is smaller than the resonance frequency of the second work coil and the difference is included in a first reference range set in advance, and a step of changing the drive frequency of the first inverter circuit to a fourth drive frequency corresponding to the third required power value.

[0034] The first inverter circuit includes a variable capacitor circuit, and a relay circuit connected to the variable capacitor circuit, and if the operation mode of the first inverter circuit is changed to the half-bridge mode, the capacitance value of the variable capacitor circuit is set to Cr,h of [Formula 1] by turning on or off a plurality of relays included in the relay circuit.

[0035] [Formula 1]

[0036]

[0037] (where fr,h is a value identical to the frequency of a switching signal input to the second inverter circuit, and Lr is an inductance value of a second inductor included in the second inverter circuit)

[0038] In addition, the control method of the induction heating device of the embodiment of the present application further includes a step of changing the power control mode of the first inverter circuit to an asymmetric pulse width modulation mode after the drive frequency of the first inverter circuit is changed to the fourth drive frequency.

[0039] The step of changing the operation mode or the power control mode of the first inverter circuit or the second inverter circuit includes a step of changing the power control mode of the work coil for which the required power value is changed to either one of an asymmetric pulse width modulation mode and a phase shift mode if the resonance frequency of the first work coil and the resonance frequency of the second work coil are identical and the difference is included in a first reference range set in advance, and a step of adjusting the output power value of the work coil for which the required power value is changed to be identical to the third required power value according to the power control mode.

[0040] The step of changing the power control mode of the work coil of which the required power value is changed to either one of the asymmetric pulse width modulation mode and the phase shift mode includes a step of changing the power control mode to the asymmetric pulse width modulation mode if the operation mode of the work coil of which the required power value is changed is the half bridge mode, and a step of changing the power control mode to either one of the asymmetric pulse width modulation mode and the phase shift mode if the operation mode of the work coil of which the required power value is changed is the full bridge mode.

[0041] The step of changing the output power value of the work coil of which the required power value is changed to the third required power value includes a step of changing the output power value of the work coil of which the required power value is changed to the third required power value by adjusting a duty ratio of a switching signal for driving the work coil of which the required power value is changed if the power control mode is set to the asymmetric pulse width modulation mode.

[0042] The step of changing the output power value of the work coil of which the required power value is changed to the third required power value includes a step of changing the output power value of the work coil of which the required power value is changed to the third required power value by adjusting a phase difference between a plurality of switching signals for driving the work coil of which the required power value is changed if the power control mode is set to the phase shift mode.

[0043] Technical Effects

[0044] The induction heating device according to the present application can prevent the interference noise caused by the driving of the work coil while maintaining the output power value of the work coil to be the same as the required power value when the two work coils in the induction heating device are simultaneously driven.

[0045] In addition, the induction heating device according to the present application can prevent the interference noise caused by the driving of the work coil when a plurality of kinds of containers having different characteristics from each other are heated using the induction heating device. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a graph showing resonance characteristic curves of each work coil when the induction heating device including two work coils is driven.

[0047] Figure 2 is an exploded perspective view of an induction heating device of an embodiment of the present application.

[0048] Figure 3 is a circuit configuration diagram of an induction heating device of an embodiment of the present application.

[0049] Figure 4 FIG. 6 is a waveform chart showing waveforms of a switching signal, an input voltage, and a resonant current when the operation mode of the first inverter circuit is the full-bridge mode in an embodiment of the present application.

[0050] Figure 5 FIG. 7 is a waveform chart showing waveforms of a switching signal, an input voltage, and a resonant current when the operation mode of the first inverter circuit is the full-bridge mode and the power control mode of the first inverter circuit is the asymmetric pulse width modulation mode in an embodiment of the present application.

[0051] Figure 6 FIG. 8 is a waveform chart showing waveforms of a switching signal, an input voltage, and a resonant current when the operation mode of the first inverter circuit is the full-bridge mode and the power control mode of the first inverter circuit is the phase shift mode in an embodiment of the present application.

[0052] Figure 7 FIG. 9 is a graph showing a resonant characteristic curve of a work coil when the operation mode of the first inverter circuit is the full-bridge mode in an embodiment of the present application.

[0053] Figure 8 FIG. 10 is a graph showing power conversion efficiency of an induction heating device when the power control mode of the first inverter circuit is set to the pulse frequency modulation mode, when the power control mode of the first inverter circuit is set to the asymmetric pulse width modulation mode, and when the power control mode of the first inverter circuit is set to the phase shift mode in a state where the operation mode of the first inverter circuit is the full-bridge mode in an embodiment of the present application.

[0054] Figure 9 FIG. 13 is a waveform chart showing waveforms of a switching signal, an input voltage, and a resonant current when the operation mode of the first inverter circuit is the half-bridge mode in an embodiment of the present application.

[0055] Figure 10 FIG. 14 is a waveform chart showing waveforms of a switching signal, an input voltage, and a resonant current when the operation mode of the first inverter circuit is the half-bridge mode and the power control mode of the first inverter circuit is the asymmetric pulse width modulation mode in an embodiment of the present application.

[0056] Figure 11 FIG. 15 is a graph showing a resonant characteristic curve of a work coil when the operation mode of the first inverter circuit is the half-bridge mode in an embodiment of the present application.

[0057] Figure 12is a graph showing the power conversion efficiency of the induction heating device when the power control mode of the first inverter circuit is set to the pulse frequency modulation mode and when the power control mode of the first inverter circuit is set to the asymmetric pulse width modulation mode in a state where the operation mode of the first inverter circuit is the half-bridge mode in an embodiment of the present application.

[0058] Figure 13 is a graph showing the resonance characteristic curves of each work coil when the required power value of the first work coil is changed in a state where the resonance frequency of the first work coil and the resonance frequency of the second work coil are different from each other in an embodiment of the present application.

[0059] Figure 14 is a graph showing the resonance characteristic curves of each work coil when the power control mode of the first work coil is changed in order to prevent interference noise in an embodiment of the present application. Figure 13

[0060] Figure 15 is a graph showing the resonance characteristic curves of each work coil when the required power value of the first work coil is changed in a state where the resonance frequency of the first work coil and the resonance frequency of the second work coil are the same as each other in another embodiment of the present application.

[0061] Figure 16 is a graph showing the resonance characteristic curves of each work coil when the power control mode of the first work coil is changed in order to prevent interference noise in an embodiment of the present application. Figure 15

[0062] Figure 17 is a graph showing the resonance characteristic curves of each work coil when the required power value of the second work coil is changed in a state where the resonance frequency of the first work coil and the resonance frequency of the second work coil are the same as each other in another embodiment of the present application.

[0063] Figure 18 is a graph showing the resonance characteristic curves of each work coil when the power control mode of the second work coil is changed in order to prevent interference noise in an embodiment of the present application. Figure 17

[0064] Figure 19 is a flowchart showing the control method of the induction heating device in an embodiment of the present application. DETAILED DESCRIPTION

[0065] ​​​The purpose, features, and advantages will be described in detail below with reference to the accompanying drawings, so that those of ordinary skill in the art can easily implement the technical idea of the present application. In explaining the present application, when it is judged that a detailed explanation of related known technology can make the gist of the present application unclear, a detailed explanation thereof will be omitted. Hereinafter, preferred embodiments of the present application will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar structural elements.

[0066] Figure 2 is an exploded perspective view of an induction heating apparatus of an embodiment of the present application. Other embodiments and configurations can also be provided.

[0067] An induction heating apparatus 10 of an embodiment of the present application includes a housing 102 constituting a main body, and a cover plate 104 combined with the housing 102 to seal the inside of the housing 102.

[0068] The cover plate 104 is combined with the top surface of the housing 102 and forms a space inside the housing 102 with respect to the outside. The cover plate 104 includes an upper plate portion 106 on which a container for cooking food can be placed. In an embodiment of the present application, the upper plate portion 106 can be formed of a reinforced glass material such as ceramic glass, but the material of the upper plate portion 106 can be different according to embodiments.

[0069] Heating regions 12, 14 corresponding to the work coil assemblies 122, 124, respectively, are formed in the upper plate portion 106. In order for a user to be able to clearly recognize the positions of the heating regions 12, 14, lines or patterns corresponding to the heating regions 12, 14 can be printed or marked on the upper plate portion 106.

[0070] The housing 102 can have a shape of a hexahedron with an upper portion open. In the space formed inside the housing 102, the work coil assemblies 122, 124 for heating the container are disposed. In addition, an interface portion 114 is provided inside the housing 102, and the interface portion 114 is for a user to turn on power, or has a function of adjusting the power level of each heating region 12, 14 and a function of displaying information related to the induction heating apparatus 10. The interface portion 114 can be constituted of a touch panel capable of realizing touch-based information input and information display, but according to embodiments, an interface portion 114 having a different structure can also be used.

[0071] An operation region 118 is provided in the upper plate portion 106, and the operation region 118 is disposed at a position corresponding to the interface portion 114. In order for a user to operate, text or images, etc. can be printed on the operation region 118 in advance. A user can refer to the text or images printed in advance on the operation region 118, touch a specific portion of the operation region 118 to perform a desired operation. In addition, information output by the interface portion 114 can be displayed through the operation region 118.

[0072] Users can set the power level of each heating zone 12, 14 using the interface 114. The power level can be displayed on the operation area 118 using numbers (e.g., 1, 2, 3, ..., 9). If a power level is set for each heating zone 12, 14, the required power value and drive frequency of the working coil corresponding to each heating zone 12, 14 are determined. Based on the determined drive frequency, the controller drives each working coil so that the output power value of each working coil matches the required power value set by the user.

[0073] A power supply unit 112 for supplying power to the working coil assemblies 122, 124 or the interface portion 114 is arranged in the space formed inside the housing 102.

[0074] For reference, Figure 2 In the embodiments, two working coil assemblies, namely the first working coil assembly 122 and the second working coil assembly 124, are configured inside the housing 102. However, according to the embodiments, more than three working coil assemblies may also be configured inside the housing 102.

[0075] The working coil assemblies 122 and 124 include: a working coil that uses a high-frequency alternating current supplied by the power supply unit 112 to form an induced magnetic field; and a heat insulation sheet for protecting the coil from heat generated from the container (or object). For example, in Figure 2 In this configuration, the first working coil assembly 122 includes: a first working coil 132 for heating a container (or object) placed in the first heating zone 12; and a first heat insulation sheet 130. Additionally, the second working coil assembly 124 includes a second working coil and a second heat insulation sheet. According to embodiments, a heat insulation sheet may not be provided.

[0076] A temperature sensor is positioned at the center of each working coil. For example, in Figure 2 In this invention, a temperature sensor 134 is disposed at the center of the first working coil 134. The temperature sensor senses (or determines) the temperature of the container (or object) placed in each heating zone. In one embodiment of the invention, the temperature sensor may be a thermistor temperature sensor with a variable resistance whose resistance value changes with the temperature of the container, but is not limited thereto.

[0077] In one embodiment of the present invention, a 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 determines the temperature of the container based on the magnitude of the sensing voltage output from the temperature sensor. If the temperature of the container is above a preset reference value, an overheat protection action is performed to reduce the output power value of the working coil or interrupt the driving of the working coil.

[0078] In addition, although not shown in FIG. 1, a substrate on which a plurality of circuits or elements (including the controller) are mounted can be disposed in a space formed inside the housing 102. The controller can drive each of the work coils to perform a heating operation according to a user's heating start instruction input through the interface portion 114. If the user inputs a heating end instruction through the interface portion 114, the controller ends the heating operation by interrupting the driving of the work coils. Figure 2

[0079] Figure 3 is a circuit configuration diagram of an induction heating device according to an embodiment of the present disclosure. Other embodiments and configurations can also be provided.

[0080] As shown in FIG. 2, the induction heating device 10 includes a first rectifier circuit 202, a first smoothing circuit L1, C1, a first inverter circuit 204, a first work coil 132, a second rectifier circuit 212, a second smoothing circuit L3, C5, a second inverter circuit 214, a second work coil 142, a first driving circuit 22, a second driving circuit 24, and a controller 2. The controller 2 can include hardware for controlling other components. Figure 3 The first rectifier circuit 202 includes a plurality of diode elements D1, D2, D3, D4. As shown in FIG. 2, the first rectifier circuit 202 can be a bridge diode circuit, and can be a different circuit according to an embodiment. The first rectifier circuit 202 rectifies an alternating current input voltage from the power supply device 20 and outputs a voltage having a pulsating waveform.

[0081] Figure 3 The first smoothing circuit L1, C1 smoothes the voltage rectified by the first rectifier circuit 202 and outputs a direct current link voltage. The first smoothing circuit L1, C1 includes a first inductor L1 and a first direct current link capacitor C1.

[0082] The first inverter circuit 204 includes a first switching element SW1, a second switching element SW2, a third switching element SW3, a fourth switching element SW4, a second inductor L2, a variable capacitor portion C2, C3, C4 (or a variable capacitor device / circuit) including a plurality of capacitors, and a relay circuit 206 (or a relay portion). As shown in FIG. 2, the first inverter circuit 204 of the induction heating device 10 is configured of a full-bridge circuit including four switching elements SW1, SW2, SW3, SW4.

[0083] The first inverter circuit 204 of the induction heating device 10 is configured of a full-bridge circuit including four switching elements SW1, SW2, SW3, SW4. Figure 3

[0084] ​​​The first switch element SW1, the second switch element SW2, the third switch element SW3, and the fourth switch element SW4 are turned on and off in accordance with a first switching signal S1, a second switching signal S2, a third switching signal S3, and a fourth switching signal S4 from the first drive circuit 22, respectively. In each of the switch elements SW1, SW2, SW3, and SW4, the on state is maintained when the respective switching signal S1, S2, S3, and S4 is at a high level, and the off state is maintained when the respective switching signal S1, S2, S3, and S4 is at a low level.

[0085] Any of the switch elements SW1, SW2, SW3, and SW4 can be turned on and off in a complementary manner to each other. For example, in any of the operation modes, the second switch element SW2 can be turned off (on) during the period in which the first switch element SW1 is turned on (off). Switch elements that are turned on and off in a complementary manner to each other are referred to as "complementary" switch elements.

[0086] In addition, any of the switch elements SW1, SW2, SW3, and SW4 can be turned on and off in the same manner as each other. For example, in any of the operation modes, the first switch element SW1 and the third switch element SW3 can be turned on and off at the same point in time as each other. Switch elements that are turned on and off at the same point in time as each other are referred to as "corresponding" switch elements.

[0087] The DC link voltage input to the first inverter circuit 204 is converted into an alternating voltage (alternating current) by the on and off actions (switching actions) of the switch elements SW1, SW2, SW3, and SW4 included in the first inverter circuit 204. The alternating voltage (alternating current) converted by the first inverter circuit 204 is supplied to the second inductor L2, the first work coil 132, and the plurality of variable capacitor sections C2, C3, and C4 (or variable capacitor circuit). If the alternating voltage (alternating current) is supplied by the first inverter circuit 204, a resonance phenomenon occurs in the first work coil 132, and thus heat energy is supplied to the container (or object).

[0088] The first switching signal S1, the second switching signal S2, the third switching signal S3, and the fourth switching signal S4 are each a PWM (Pulse Width Modulation) signal having a predetermined duty ratio.

[0089] The relay circuit 206 includes a plurality of relays (or switches) connected in series with each of the variable capacitor sections C2, C3, and C4. Each of the relays included in the relay circuit 206 can be turned on or off in accordance with a control signal of the controller 2.

[0090] The overall capacitance value of the variable capacitors C2, C3, C4 (or the variable capacitor circuit) can be changed according to the number of relays that are turned off by the control of the controller 2. That is, the controller 2 can adjust the capacitance value of the variable capacitors C2, C3, C4 by turning on or off the relays included in the relay circuit 206.

[0091] In at least one embodiment of the present application, the controller 2 determines the operation mode of the first inverter circuit 204, and can control the on-off state of each relay included in the relay circuit 206 so that the capacitance value of the variable capacitor section C2, C3, C4 corresponds to the operation mode of the first inverter circuit 204. As described later, the frequency of the resonant current flowing in the working coil 132 can be adjusted according to the capacitance value of the variable capacitor section C2, C3, C4.

[0092] In Figure 3 the embodiment, the variable capacitor circuit includes three capacitors C2, C3, C4 connected in parallel. However, the number of capacitors included in the variable capacitor circuit can be different according to the embodiment. In addition, the connection state (series or parallel) of the capacitors included in the variable capacitor section can be different according to the embodiment.

[0093] Referring to Figure 3 , the second rectifier circuit 212 includes a plurality of diode elements D5, D6, D7, D8. As shown in Figure 3 , the second rectifier circuit 212 can be a bridge diode circuit, and can be a different circuit according to the embodiment. The second rectifier circuit 212 rectifies the alternating current input voltage from the power supply device 20 and outputs a voltage having a pulsating waveform.

[0094] The second smoothing circuit L3, C5 smoothes the voltage rectified by the second rectifier circuit 212 and outputs a direct current link voltage. The second smoothing circuit L3, C5 includes a third inductor L3 and a second direct current link capacitor C5.

[0095] The second inverter circuit 214 includes a sixth capacitor C6, a seventh capacitor C7, a fifth switching element SW5, and a sixth switching element SW6. As shown in Figure 3 , the second inverter circuit 214 of the induction heating device 10 is configured by a half-bridge circuit including two switching elements SW5, SW6. However, in another embodiment of the present application, the second inverter circuit 214 can also be configured by a full-bridge circuit including four switching elements, like the first inverter circuit 204.

[0096] The fifth switching element SW5 and the sixth switching element SW6 are turned on and off in a complementary manner based on a fifth switching signal S5 and a sixth switching signal S6 output from the second drive circuit 24, respectively.

[0097] In Figure 3 An embodiment in which each of the switching elements SW1, SW2, SW3, SW4, SW5, and SW6 is an IGBT element is shown in the above description, but each of the switching elements SW1, SW2, SW3, SW4, SW5, and SW6 can be a switching element of a different type (e.g., a BJT or a FET, etc.).

[0098] The DC link voltage input to the second inverter circuit 214 is converted into an alternating voltage (alternating current) by on and off actions (switching actions) of the switching elements SW5 and SW6 included in the second inverter circuit 214. The alternating voltage (alternating current) converted by the second inverter circuit 214 is supplied to the second work coil 142. If the alternating voltage (alternating current) is supplied by the second inverter circuit 214, a resonance phenomenon occurs in the second work coil 142, and thus heat energy is supplied to the container (or the object).

[0099] In the present application, the fifth switching signal S5 and the sixth switching signal S6 are PWM signals each having a duty ratio set in advance.

[0100] If the alternating currents output from each of the inverter circuits 204 and 214 are supplied to the work coils 132 and 142, each of the work coils 132 and 142 is driven. If each of the work coils 132 and 142 is driven, eddy currents flow in the container (or the object) placed on the upper portion of each of the work coils 132 and 142, and thus the container (or the object) is heated. While each of the work coils 132 and 142 is driven, the amount of heat energy supplied to the container differs depending on the amount of power actually generated, that is, the output power value of each of the work coils 132 and 142.

[0101] The controller 2 determines the drive frequency of each of the work coils 132 and 142 corresponding to the power level set by the user with respect to the heating region. In an embodiment of the present application, the controller 2 can determine the drive frequency of each of the work coils 132 and 142 with reference to a table in which the drive frequency corresponding to each of the power levels is recorded or a relational expression between each of the power levels and the drive frequency. In addition, the amount of power required to be output by each of the work coils 132 and 142, that is, the required power value, is determined according to the power level set by the user.

[0102] The controller 2 supplies a control signal corresponding to the determined drive frequency to each of the drive circuits 22 and 24. Each of the drive circuits 22 and 24 outputs a switching signal S1, S2, S3, S4, S5, or S6 having a duty ratio corresponding to the drive frequency determined by the controller 2, based on the control signal output from the controller 2.

[0103] If the user operates the interface portion of the induction heating device 10 to change the induction heating device 10 to a power on state, power is supplied from the power supply device 20 to the induction heating device, and thus the induction heating device 10 is in a driving standby state. Next, the user places a container (or an object) on the upper portion of each of the work coils 132, 142 of the induction heating device 10, and inputs a heating start command to each of the work coils 132, 142 by setting a power level to the container. If the user inputs the heating start command, a power value required for each of the work coils 132, 142, i.e., a required power value, is determined according to the power level set by the user.

[0104] The controller 2 receiving the heating start command of the user determines a driving frequency corresponding to the required power value of each of the work coils 132, 142, and supplies a control signal corresponding to the determined driving frequency to each of the driving circuits 22, 24. Thereby, the switching signals S1, S2, S3, S4, S5, S6 are output from each of the driving circuits 22, 24, and each of the work coils 132, 142 is driven while the switching signals S1, S2, S3, S4, S5, S6 are input to the switching elements SW1, SW2, SW3, SW4, SW5, SW6, respectively. If each of the work coils 132, 142 is driven, eddy current is generated in the container and the container is heated.

[0105] On the other hand, while the first work coil 132 and the second work coil 142 are driven at the first driving frequency and the second driving frequency, respectively, to heat the container, the user can change the required power value of the first work coil 132 or the second work coil 142 to a third required power value. For example, if the required power value of the first work coil 132 is changed from the first required power value (e.g., 2000 W) to the third required power value (e.g., 500 W), the controller 2 needs to change the driving frequency of the first work coil 132 to a third driving frequency corresponding to the third required power value (e.g., 500 W).

[0106] As described above, if the driving frequency of the first work coil 132 or the second work coil 142 is changed to the third driving frequency, interference noise can be generated due to the difference between the driving frequency of the remaining work coil whose driving frequency is not changed and the third driving frequency.

[0107] In one embodiment of the present application, if the required power value of the first working coil 132 or the second working coil 142 is changed to a third required power value, the controller 2 determines a third drive frequency corresponding to the third required power value. In order to prevent the interference noise as described above, the controller 2 calculates a difference between the drive frequency of the working coil whose required power value is not changed and the third drive frequency. In the present application, the difference between the two drive frequencies means a value obtained by subtracting the smaller value from the larger value of the two drive frequencies.

[0108] If the calculated difference is included in a first reference range (for example, 5 kHz or more and 20 kHz or less) set in advance, the controller 2 changes the operation mode or the power control mode of the first inverter circuit 204 or the second inverter circuit 214 to prevent the interference noise.

[0109] In one embodiment of the present application, if the resonance frequency of the first working coil 132 is smaller than the resonance frequency of the second working coil 142, and the difference between the drive frequency of the working coil whose required power value is not changed and the third drive frequency is included in the first reference range set in advance, the controller 2 changes the operation mode of the first inverter circuit 204 from the full-bridge mode to the half-bridge mode, and determines a fourth drive frequency of the first working coil 132 corresponding to the third required power value to prevent the interference noise. The controller 2 changes the drive frequency of the first inverter circuit 204 to the fourth drive frequency.

[0110] If the operation mode of the first inverter circuit 204 is changed from the full-bridge mode to the half-bridge mode, the output power value of the first working coil 132 is reduced in the entire frequency band of the first working coil 132. Therefore, the drive frequency of the first working coil 132 corresponding to the third required power value, that is, the fourth drive frequency is reduced. Thus, the difference between the drive frequency of the first working coil 132 (the fourth drive frequency) and the drive frequency of the second working coil 142 (the second drive frequency) will reach a value of 22 kHz or more, which is the noise avoidance value set in advance. In the present application, the noise avoidance value can be set to a value larger than the maximum value (for example, 20 kHz) of the boundary values of the audible sound frequency band, and can be set differently according to the embodiment.

[0111] In one embodiment of the present application, if the resonance frequency of the first working coil 132 is the same as the resonance frequency of the second working coil 142, and the difference between the drive frequency of the working coil whose required power value is not changed and the third drive frequency is included in the first reference range set in advance, the controller 2 changes the power control mode of the working coil whose required power value is changed to either one of the asymmetric pulse width modulation mode (APWM) and the phase shift mode, and adjusts the output power value of the working coil whose required power value is changed to be the same as the third required power value according to the changed power control mode.

[0112] In one embodiment of the present application, if the operation mode of the work coil for which the power value is changed is changed to the half-bridge mode, the controller 2 can change the power control mode to the asymmetric pulse width modulation mode. Also, in one embodiment of the present application, if the operation mode of the work coil for which the power value is changed is changed to the full-bridge mode, the controller 2 can change the power control mode to either one of the asymmetric pulse width modulation mode and the phase shift mode.

[0113] In one embodiment of the present application, if the power control mode is set to the asymmetric pulse width modulation mode, the controller 2 can change the output power value of the work coil for which the power value is changed to a third required power value by adjusting the duty ratio of the switching signal for driving the work coil for which the power value is changed.

[0114] Also, in one embodiment of the present application, if the power control mode is set to the phase shift mode, the controller 2 can change the output power value of the work coil for which the power value is changed to a third required power value by adjusting the phase difference between the plurality of switching signals for driving the work coil for which the power value is changed.

[0115] As described above, if the output power value of the work coil is changed to a third required power value according to the changed power control mode after the power control mode is changed, the driving frequency of the work coil for which the power value is changed is maintained as it is without being changed. Thus, the difference between the driving frequency of the first work coil 132 and the driving frequency of the second work coil 142 deviates from the audible sound frequency band, thereby preventing the generation of interference noise.

[0116] In another embodiment of the present application, if the difference between the driving frequency of the work coil for which the power value is not changed and the third driving frequency is included in the second reference range (for example, 2 kHz or more and less than 5 kHz) set in advance, the controller 2 can set the driving frequency of the first work coil 132 and the driving frequency of the second work coil 142 to be the same. Thus, the generation of interference noise caused by the driving of the first work coil 132 and the second work coil 142 is prevented.

[0117] Also, in another embodiment of the present application, if the difference between the driving frequency of the work coil for which the power value is not changed and the third driving frequency is not included in the first reference range and the second reference range, the controller 2 sets the driving frequency of the work coil for which the power value is changed to the third driving frequency, and does not change the driving frequency of the work coil for which the power value is not changed. This is because, if the difference between the driving frequency of the work coil for which the power value is not changed and the third driving frequency is not included in the first reference range and the second reference range, interference noise is not generated.

[0118] For reference, the boundary values of the first reference range and the second reference range can be set differently according to embodiments.

[0119] Figure 4 The waveforms of the switching signals, the input voltage, and the resonance current when the operation mode of the first inverter circuit in an embodiment of the present application is the full-bridge mode are shown respectively. Other embodiments and configurations can also be provided.

[0120] When the operation mode of the first inverter circuit 204 is the full-bridge mode, the controller 2 applies control signals to the drive circuit 22 to output switching signals S1, S2, S3, S4 having waveforms as shown in FIG. 6. Figure 4

[0121] In addition, as shown in FIG. 7, in order to output the resonance current supplied to the first working coil 132 once during one period TS1 of the switching signals S1, S2, S3, S4, in other words, to make the frequency of the resonance current supplied to the first working coil 132 one time of the frequency of the switching signals S1, S2, S3, S4, the controller 2 sets the capacitance value of the variable capacitor circuit C1, C2, C3 to Cr,f as shown in the following [Equation 1]. Figure 4

[0122] [Equation 1]

[0123]

[0124] In [Equation 1], fr,f is the same as the frequency of the switching signals S1, S2, S3, S4, and Lr represents the inductance value of the second inductor L2.

[0125] The controller 2 turns on or off the plurality of relays included in the relay circuit 206 respectively to make the overall capacitance value of the variable capacitor circuit C1, C2, C3 (or the variable capacitor portion) coincide with the capacitance value Cr,f of [Equation 1]. If the capacitance value adjustment of the variable capacitor circuit C1, C2, C3 is completed, the controller 2 supplies the switching signals S1, S2, S3, S4 having waveforms as shown in FIG. 6 to the first inverter circuit 204 through the first drive circuit 22. Thus, heating of the container (or the object) is performed. Figure 4

[0126] As shown in FIG. 8, the controller 2 turns on or off the plurality of relays included in the relay circuit 206 respectively to make the overall capacitance value of the variable capacitor circuit C1, C2, C3 (or the variable capacitor portion) coincide with the capacitance value Cr,f of [Equation 1]. If the capacitance value adjustment of the variable capacitor circuit C1, C2, C3 is completed, the controller 2 supplies the switching signals S1, S2, S3, S4 having waveforms as shown in FIG. 6 to the first inverter circuit 204. Thus, heating of the container (or the object) is performed. Figure 4 ​​​As shown, each of the switching signals has an on-interval and an off-interval within one period TS1. In the present application, the time of the on-interval is referred to as an on-time TS11, and the time of the off-interval is referred to as an off-time TS12. In addition, the ratio of the on-time TS11 with respect to one period TS1 is referred to as a duty ratio of the switching signal. For example, in a case where one period TS1 of the first switching signal S1 is 1 second and the on-time TS11 is 0.5 second, the duty ratio of the first switching signal S1 is 50% (or 0.5).

[0127] Referring to Figure 4 , the first switching element SW1 turns on and off in a complementary manner to the second switching element SW2. In addition, the third switching element SW3 turns on and off in a complementary manner to the fourth switching element SW4.

[0128] Figure 4 A waveform of Vab, which is the magnitude of the voltage between the nodes a and b in the circuit diagram of Figure 3 is shown. Here, Vab is the same as an input voltage value Vin, which is the magnitude of the input voltage to the first operating coil 132. In addition, Figure 4 A waveform of the input current, i.e., the resonance current, to the first operating coil 132 is shown.

[0129] As shown in Figure 4 , when the operation mode of the first inverter circuit 204 is the full-bridge mode, the input voltage Vab and the resonance current have the same frequency as each other. In addition, the frequency of the input voltage Vab and the resonance current is the same as the frequency of the switching signals S1, S2, S3, S4. Thus, the voltage gain of the first operating coil 132 remains a maximum value (e.g., 1), and thus it is possible to stably supply power to the container.

[0130] Figure 5 Waveforms of the switching signals, the input voltage, and the resonance current when the operation mode of the first inverter circuit is the full-bridge mode and the power control mode of the first inverter circuit is the asymmetric pulse width modulation mode in an embodiment of the present application are shown. Other embodiments and configurations can also be provided.

[0131] If the power control mode of the first inverter circuit 204 is determined to be the asymmetric pulse width modulation mode, the controller 2 adjusts the duty ratios of the switching signals S1, S2, S3, S4. As Figure 5As shown, the magnitudes of the input voltage Vab and resonant current will differ depending on the on-time TS11 of the first switch signal S1 and the fourth switch signal S4 (or the off-time of the second switch signal S2 and the third switch signal S3) and the on-time TS12 of the second switch signal S2 and the third switch signal S3 (or the off-time of the first switch signal S1 and the fourth switch signal S4). Since the output power of the first working coil 132 changes according to the magnitude of the input voltage Vab and the magnitude of the resonant current, the controller 2 can adjust the output power of the first working coil 132 by adjusting the on-time TS11 of the first switch signal S1 and the fourth switch signal S4, i.e., the duty cycle of the first switch signal S1 and the fourth switch signal S4.

[0132] For example, controller 2 can increase the output power of the first working coil 132 by increasing the on-time TS11 of the first switch signal S1 and the fourth switch signal S4, in other words, by increasing the duty cycle of the first switch signal S1 and the fourth switch signal S4. Conversely, controller 2 can decrease the output power of the first working coil 132 by decreasing the on-time TS11 of the first switch signal S1 and the fourth switch signal S4, in other words, by decreasing the duty cycle of the first switch signal S1 and the fourth switch signal S4.

[0133] exist Figure 5 In this embodiment, the duty cycle of the first switch signal S1 and the fourth switch signal S4 is less than... Figure 4 The duty cycles of the first switch signal S1 and the fourth switch signal S4 in the embodiment. Therefore, in Figure 5 In the embodiment, the actual power value of the first working coil 132 is less than Figure 4 The actual power value of the first working coil 132 in the embodiment.

[0134] Figure 6 The waveforms of the switching signal, input voltage, and resonant current are shown respectively when the first inverter circuit operates in full-bridge mode and the power control mode of the first inverter circuit is phase-off mode in one embodiment of the present invention. Other embodiments and configurations may also be provided.

[0135] If the power control mode of the first inverter circuit 204 is determined to be phase-shifted mode, then the controller 2 adjusts the phase difference between the corresponding plurality of switching signals. For example... Figure 6As shown, the magnitudes of the input voltage Vab and resonant current change according to the phase difference between the corresponding first switch signal S1 and the third switch signal S3 (or the phase difference between the second switch signal S2 and the third switch signal S3). Since the output power of the first working coil 132 changes according to the magnitudes of the input voltage Vab and the resonant current, the controller 2 can adjust the output power of the first working coil 132 by adjusting the phase difference between the corresponding first switch signal S1 and the third switch signal S3.

[0136] For example, controller 2 can increase the output power of the first working coil 132 by reducing the phase difference between the corresponding first switching signal S1 and the third switching signal S3. Conversely, controller 2 can decrease the output power of the first working coil 132 by increasing the phase difference between the corresponding first switching signal S1 and the third switching signal S3.

[0137] exist Figure 6 In this embodiment, the phase difference (90°) between the corresponding first switch signal S1 and the third switch signal S3 is greater than [missing information]. Figure 13 The phase difference (0°) between the corresponding first switch signal S1 and the third switch signal S3 in the embodiment. Therefore, in Figure 6 In the embodiment, the actual power value of the first working coil 132 is less than Figure 4 The actual power value of the first working coil 132 in the embodiment.

[0138] In one embodiment of the present invention, when the first inverter circuit 204 operates in full-bridge mode, the controller 2 can compare the required power value of the first working coil 132 with a preset reference power value, and determine the power control mode of the first inverter circuit 204 as either an asymmetric pulse width modulation mode or a phase offset mode. For example, if the required power value of the first working coil 132 is less than the reference power value, the controller 2 can determine the power control mode of the first inverter circuit 204 as an asymmetric pulse width modulation mode; if the required power value of the first working coil 132 is not less than the reference power value, the controller 2 can determine the power control mode of the first inverter circuit 204 as a phase offset mode.

[0139] Figure 7 This is a graph showing the resonant characteristic curve of the working coil when the first inverter circuit operates in full-bridge mode according to one embodiment of the present invention. Other embodiments and configurations may also be provided.

[0140] Figure 7The resonant characteristic curves 41 and 42 of the first working coil 132 are shown respectively when the duty cycle of the first switching signal S1 is 50% in full-bridge mode and when the duty cycle of the first switching signal S1 is 30% in full-bridge mode. Figure 7 In this context, fr is the resonant frequency of the first working coil 132.

[0141] like Figure 7 As shown, in full-bridge mode, when the driving frequency of the first working coil 132 is f1, if the duty cycle of the first switching signal S1 is set to 50%, the actual power value of the first working coil 132 will be P1. However, if the controller 2 maintains the driving frequency of the first working coil 132 at f1 and reduces the duty cycle of the first switching signal S1 from 50% to 30%, the actual power value of the first working coil 132 will decrease to P2. Therefore, the controller 2 can adjust the actual power value of the first working coil 132 simply by adjusting the duty cycle of the first switching signal S1 according to the asymmetric pulse width modulation method while keeping the driving frequency of the first working coil 132 at the same value in full-bridge mode.

[0142] Figure 7 The curve can also be the resonance characteristic curve 41 when the phase difference between the first switch signal S1 and the third switch signal S3 is 0°, and the resonance characteristic curve 42 when the phase difference between the first switch signal S1 and the third switch signal S3 is 90°.

[0143] like Figure 7 As shown, in full-bridge mode, when the driving frequency of the first working coil 132 is f1, if the phase difference between the first switching signal S1 and the third switching signal S3 is set to 0°, the actual power value of the first working coil 132 will be P1. However, if the controller 2 maintains the driving frequency of the first working coil 132 at f1 and increases the phase difference between the first switching signal S1 and the third switching signal S3 to 90°, the actual power value of the first working coil 132 will decrease to P2. Therefore, the controller 2 can adjust the output power value of the first working coil 132 simply by adjusting the phase difference between the first switching signal S1 and the third switching signal S3 according to the phase shift method, while maintaining the same driving frequency of the first working coil 132 in full-bridge mode.

[0144] Figure 8is a graph showing the power conversion efficiency of the induction heating device when the power control mode of the first inverter circuit is set to the pulse frequency modulation mode, when the power control mode of the first inverter circuit is set to the asymmetric pulse width modulation mode, and when the power control mode of the first inverter circuit is set to the phase shift mode, respectively, in a state where the operation mode of the first inverter circuit is the full-bridge mode in one embodiment of the present application. Other embodiments and configurations can also be provided.

[0145] Figure 8 A graph 43 showing the power conversion efficiency for each input power value when the power control mode of the first inverter circuit 204 is the pulse frequency modulation mode, i.e., when the controller 2 adjusts the output power value of the first work coil 132 by adjusting the drive frequency of the first work coil 132, is shown in a state where the operation mode of the first inverter circuit 204 is the full-bridge mode.

[0146] In addition, Figure 8 A graph 44 showing the power conversion efficiency for each input power value when the power control mode of the first inverter circuit 204 is the asymmetric pulse width modulation mode, i.e., when the controller 2 adjusts the output power value of the first work coil 132 by adjusting the duty ratio of the switching signals without changing the drive frequency of the first work coil 132, is shown in a state where the operation mode of the first inverter circuit 204 is the full-bridge mode.

[0147] In addition, Figure 8 A graph 45 showing the power conversion efficiency for each input power value when the power control mode of the first inverter circuit 204 is the phase shift mode, i.e., when the controller 2 adjusts the output power value of the first work coil 132 by adjusting the phase difference between the plurality of switching signals corresponding to each other without changing the drive frequency of the first work coil 132, is shown in a state where the operation mode of the first inverter circuit 204 is the full-bridge mode.

[0148] As Figure 8 shown, the power conversion efficiency when the power control mode of the first inverter circuit 204 is set to the asymmetric pulse width modulation mode or the phase shift mode is greater than the power conversion efficiency when the power control mode of the first inverter circuit 204 is set to the pulse frequency modulation mode in the entire range of the input power value. Therefore, by adjusting the output power value of the first work coil 132 to the asymmetric pulse width modulation mode or the phase shift mode in a state where the operation mode of the first inverter circuit 204 is set to the full-bridge mode, the power conversion efficiency of the first work coil 132 is improved compared to the induction heating device of the disadvantageous configuration.

[0149] Figure 9The waveforms of the switching signal, input voltage, and resonant current are shown respectively when the first inverter circuit operates in half-bridge mode in one embodiment of the present invention. Other embodiments and configurations may also be provided.

[0150] If the operating mode of the first inverter circuit 204 is determined to be half-bridge mode, the controller 2 applies a control signal to the first drive circuit 22 to output a signal having the following characteristics: Figure 9 The waveforms shown represent the switching signals S1, S2, S3, and S4.

[0151] In addition, such as Figure 9 As shown, in order to output the resonant current supplied to the first working coil 132 once during one cycle TS2 of the switching signals S1, S2, S3, S4, in other words, to make the frequency of the resonant current supplied to the first working coil 132 reach twice the frequency of the switching signals S1, S2, S3, S4, as shown in [Formula 2] below, the controller 2 sets the capacitance value of the variable capacitor circuits C1, C2, C3 to Cr,h.

[0152] [Formula 2]

[0153]

[0154] In [Formula 2], fr,h has the same frequency as the switching signals S1, S2, S3, and S4, and Lr represents the inductance value of the second inductor L2.

[0155] The controller 2 connects or disconnects the plurality of relays included in the relay circuit 206, respectively, so that the overall capacitance value of the variable capacitor circuits C1, C2, and C3 is consistent with the capacitance value Cr,h in [Formula 2]. Once the capacitance values ​​of the variable capacitor circuits C1, C2, and C3 are adjusted, the controller 2, through the first drive circuit 22, will... Figure 9 The switching signals S1, S2, S3, and S4 shown in the diagram are supplied to the inverter circuit 204. This, in turn, heats the container.

[0156] Reference Figure 9 The first switching element SW1 is turned on and off in a complementary manner to the second switching element SW2. Meanwhile, the third switching element SW3 remains continuously on, and the fourth switching element SW4 remains continuously off.

[0157] Figure 9 It was shown as Figure 3 The waveform of Vab, representing the magnitude of the voltage between nodes a and b in the circuit diagram. Here, Vab is the same as the input voltage value Vin, which is the magnitude of the input voltage to the first working coil 132. Additionally, Figure 9 The waveform of the input current, i.e. the resonant current, input to the first working coil 132 is shown.

[0158] like Figure 9 As shown, when the first inverter circuit 204 operates in half-bridge mode, the input voltage Vab and the resonant current have the same frequency. Furthermore, the frequencies of the input voltage Vab and the resonant current are the same as the frequencies of the switching signals S1, S2, S3, and S4. Therefore, the voltage gain of the first operating coil 132 remains at its maximum value (e.g., 1), thus enabling stable power supply to the container.

[0159] On the other hand, if the operating mode of the first inverter circuit 204 is determined to be half-bridge mode, the controller 2 determines the power control mode of the first inverter circuit 204 to be asymmetric pulse width modulation mode. In asymmetric pulse width modulation mode, the controller 2 can adjust the output power value of the first working coil 132 by adjusting the duty cycle of the switching signals S1, S2, S3, and S4 while maintaining the frequencies of the switching signals S1, S2, S3, and S4 as is.

[0160] Figure 10 The waveforms of the switching signal, input voltage, and resonant current are shown respectively when the first inverter circuit operates in half-bridge mode and the power control mode of the first inverter circuit is asymmetric pulse width modulation mode in one embodiment of the present invention. Other embodiments and configurations may also be provided.

[0161] If the power control mode of the first inverter circuit 204 is determined to be asymmetric pulse width modulation mode, then the controller 2 adjusts the duty cycle of the switching signals S1, S2, S3, and S4. Figure 10 As shown, the magnitudes of the input voltage Vab and resonant current change according to the on-time TS21 of the first switch signal S1 (or the off-time of the second switch signal S2) and the on-time TS22 of the second switch signal S2 (or the off-time of the first switch signal S1). Since the output power of the first working coil 132 changes according to the magnitudes of the input voltage Vab and the resonant current, the controller 2 can adjust the output power of the first working coil 132 by adjusting the on-time TS21 of the first switch signal S1, i.e., the duty cycle of the first switch signal S1.

[0162] For example, controller 2 can increase the output power of the first working coil 132 by increasing the on-time TS21 of the first switching signal S1, in other words, by increasing the duty cycle of the first switching signal S1. Conversely, controller 2 can decrease the output power of the first working coil 132 by decreasing the on-time TS21 of the first switching signal S1, in other words, by decreasing the duty cycle of the first switching signal S1.

[0163] exist Figure 10In an embodiment of the application, the duty cycle of the first switching signal S1 is less than 50%. Figure 9 In an embodiment of the application, the duty cycle of the first switching signal S1 of the first inverter circuit is less than 50%. Thus, in an embodiment of the application, the output power value of the first operating coil 132 is less than 50%. Figure 10 In an embodiment of the application, the duty cycle of the first switching signal S1 of the first inverter circuit is less than 50%. Thus, in an embodiment of the application, the output power value of the first operating coil 132 is less than 50%. Figure 9 In an embodiment of the application, the output power value of the first operating coil 132 is less than 50%.

[0164] Figure 11 is a graph showing the resonant characteristic curve of the operating coil when the operation mode of the first inverter circuit is the half-bridge mode in an embodiment of the application.

[0165] In an embodiment of the application, the duty cycle of the first switching signal S1 is less than 50%. Figure 11 shows the resonant characteristic curve 51 of the first operating coil 132 when the duty cycle of the first switching signal S1 is 50% in the half-bridge mode and the resonant characteristic curve 52 of the first operating coil 132 when the duty cycle of the first switching signal S1 is 30% in the half-bridge mode, respectively. In Figure 11 In the graph of FIG. 5, fr is the resonant frequency of the first operating coil 132. Other embodiments and configurations can also be provided.

[0166] As shown in FIG. 6, when the driving frequency of the first operating coil 132 is fl in the half-bridge mode, the actual power value of the first operating coil 132 will be Pl if the duty cycle of the first switching signal S1 is set to 50%. However, if the controller 2 keeps the driving frequency of the first operating coil 132 at fl and reduces the duty cycle of the first switching signal S1 from 50% to 30%, the actual power value of the first operating coil 132 will be reduced to P2. Thus, the controller 2 can adjust the actual power value of the first operating coil 132 by adjusting the duty cycle of the first switching signal S1 according to the asymmetric pulse width modulation mode only in the case where the driving frequency of the first operating coil 132 is kept at the same value in the half-bridge mode. Figure 11

[0167] is a graph showing the power conversion efficiency of the induction heating apparatus when the power control mode of the first inverter circuit is set to the pulse frequency modulation mode and when the power control mode of the first inverter circuit is set to the asymmetric pulse width modulation mode in the state where the operation mode of the first inverter circuit is the half-bridge mode in an embodiment of the application. Other embodiments and configurations can also be provided. Figure 12

[0168] Figure 12 ​A graph 53 showing the power conversion efficiency for each input power value when the power control mode of the first inverter circuit 204 is the pulse frequency modulation mode, i.e., when the controller 2 adjusts the output power value of the first work coil 132 by adjusting the drive frequency of the first work coil 132, is shown in the state where the operation mode of the first inverter circuit 204 is the half-bridge mode.

[0169] In addition, Figure 12 A graph 54 showing the power conversion efficiency for each input power value when the power control mode of the first inverter circuit 204 is the asymmetric pulse width modulation mode, i.e., when the controller 2 adjusts the output power value of the first work coil 132 by adjusting the duty ratio of the switching signal without changing the drive frequency of the first work coil 132, is shown in the state where the operation mode of the first inverter circuit 204 is the half-bridge mode.

[0170] As Figure 12 shown, the power conversion efficiency when the power control mode of the first inverter circuit 204 is set to the asymmetric pulse width modulation mode is greater than the power conversion efficiency when the power control mode of the first inverter circuit 204 is set to the pulse frequency modulation mode in the entire range of the input power value. Therefore, by adjusting the output power value of the first work coil 132 to the asymmetric pulse width modulation mode in the state where the operation mode of the first inverter circuit 204 is set to the half-bridge mode, the power conversion efficiency of the first work coil 132 is improved compared to the inductive heating device with an unfavorable configuration.

[0171] As described above, the inductive heating device 10 can heat the container by setting the operation mode of the first inverter circuit 204 to the full-bridge mode or the half-bridge mode. Therefore, it is possible to heat containers with diverse characteristics without generating interfering noise.

[0172] Hereinafter, an embodiment of the control method of the inductive heating device of the present application will be described with reference to the drawings.

[0173] Figure 13 is a graph showing the resonance characteristic curves of each work coil when the required power value of the first work coil is changed in the state where the resonance frequency of the first work coil and the resonance frequency of the second work coil are different from each other in an embodiment of the present application. In addition, Figure 14 is a graph showing the resonance characteristic curves of each work coil when the operation mode of the first work coil is changed to the half-bridge mode in order to prevent interfering noise in the embodiment of the Figure 13 present application.

[0174] Reference will now be made to Figure 13, the user inputs a heating start instruction after placing the container (or the object) in the first heating region 12. The first required power value of the first work coil 132 corresponding to the power level set by the user to the first heating region 12 is PI, and the driving frequency corresponding to the first required power value PI is 16 kHz. Thus, the controller 2 sets the operation mode of the first inverter circuit 204 to the full-bridge mode, sets the first driving frequency of the first work coil 132 to 16 kHz, and supplies the control signal to the first driving circuit 22. Thus, the first work coil 132 exhibits the resonance characteristic as the resonance characteristic curve 61. The first work coil 132 is driven at the driving frequency of 16 kHz, and the output power value of the first work coil 132 will be PI. At this time, the resonance frequency of the first work coil 204 is 14 kHz.

[0175] In addition, the user inputs a heating start instruction after placing the container (or the object) in the second heating region 14. The second required power value of the second work coil 142 corresponding to the power level set by the user to the second heating region 14 is P2, and the driving frequency corresponding to the second required power value P2 is 37 kHz. Thus, the controller 2 sets the second driving frequency of the second work coil 142 to 37 kHz, and supplies the control signal to the second driving circuit 24. Thus, the second work coil 142 exhibits the resonance characteristic as the resonance characteristic curve 62. The second work coil 142 is driven at the driving frequency of 37 kHz, and the output power value of the second work coil 142 will be P2. At this time, the resonance frequency of the second work coil 142 is 35 kHz.

[0176] While the first work coil 132 and the second work coil 142 are driven to heat the container (or the object), the user reduces the power level of the first heating region 12. If the power level of the first heating region 12 is lowered, the required power value of the first work coil 132 is reduced from PI to P3.

[0177] The controller 2 determines the third driving frequency as the driving frequency corresponding to the third required power value P3, which is the new required power value of the work coil whose required power value is changed, i.e., the first work coil 132. As shown in FIG. 6, the third frequency corresponding to the third required power value P3 is 19 kHz. Figure 13

[0178] The controller 2 calculates the difference between the third driving frequency of the work coil whose required power value is changed and the driving frequency (the second driving frequency) of the work coil (the second work coil 142) whose required power value is not changed. In the embodiment of FIG. 6, the difference between the third driving frequency (19 kHz) and the second driving frequency (37 kHz) is 18. Figure 13

[0179] ​​Controller 2 checks whether the calculated difference 18 is within a preset first reference range (e.g., above 5kHz and below 20kHz). Since the calculated difference 18 is within the first reference range, controller 2 changes the operating mode of the first inverter circuit 204 to half-bridge mode. Thus, it has the following characteristics: Figure 9 The switching signals S1, S2, S3, and S4 of the waveform shown are input to the first inverter circuit 204, respectively.

[0180] If the first inverter circuit 204 is driven in half-bridge mode, the output power of the first working coil 132 decreases across the entire frequency range. Therefore, the first working coil 132 has the following characteristics: Figure 14 The new resonance characteristics are shown in curve 63.

[0181] After changing the operating mode of the first inverter circuit 204 to half-bridge mode, controller 2 determines the fourth drive frequency corresponding to the third required power value P3. For example... Figure 14 As shown, the fourth driving frequency corresponding to the third required power value P3 is 15kHz.

[0182] If the drive frequency of the first working coil 132 changes to the fourth drive frequency due to the change in the operating mode of the first inverter circuit 204, the difference 22 between the second drive frequency (37kHz) of the second working coil 142 and the fourth drive frequency (15kHz) of the first working coil 132 reaches a value exceeding a preset noise avoidance value (e.g., 22), thus deviating from the second reference range. Therefore, the controller 2 drives the first working coil 132 at the fourth drive frequency (15kHz) and the second working coil 142 at the second drive frequency (37kHz). Therefore, even if the output power value of the first working coil 132 changes from P1 to P3, no interference noise caused by the driving of the first working coil 132 and the second working coil 142 will be generated.

[0183] On the other hand, such as Figure 10 As shown, if the required power value of the first working coil 132 changes after the operating mode of the first inverter circuit 204 is changed to half-bridge mode, the controller 2 can change the power control mode of the first inverter circuit 204 to asymmetric pulse width modulation mode. That is, the controller 2 can change the output power value of the first working coil 132 by changing the duty cycle of the switching signal input to the first inverter circuit 204 without changing the driving frequency of the first working coil 132. However, in another embodiment of the present invention, as... Figure 10As shown, after the operation mode of the first inverter circuit 204 is changed to the half-bridge mode, and the required power value of the first work coil 132 is changed, the controller 2 can also change the output power value of the first work coil 132 by changing the driving frequency of the first work coil 132.

[0184] Figure 15 is a graph showing the resonance characteristic curves of the respective work coils when the required power value of the first work coil is changed in a state where the resonance frequency of the first work coil and the resonance frequency of the second work coil are the same as each other in another embodiment of the present application. In addition, Figure 16 is a graph showing the resonance characteristic curves of the respective work coils when the power control mode of the first work coil is changed in the embodiment of Figure 15 for the purpose of preventing interference noise. Other embodiments and configurations can also be provided.

[0185] Referring to Figure 15 , the user inputs a heating start instruction after placing the container (or the object) on the first heating region 12. The first required power value of the first work coil 132 corresponding to the power level set by the user to the first heating region 12 is P1, and the driving frequency corresponding to the first required power value P1 is 22 kHz. Thus, the controller 2 sets the operation mode of the first inverter circuit 204 to the full-bridge mode, sets the first driving frequency of the first work coil 132 to 22 kHz, and supplies the control signal to the first driving circuit 22. Thus, the first work coil 132 exhibits the resonance characteristic as the resonance characteristic curve 65. The first work coil 132 is driven at the driving frequency of 22 kHz, and the output power value of the first work coil 132 will be P1. At this time, the resonance frequency of the first work coil 204 is 20 kHz.

[0186] In addition, the user inputs a heating start instruction after placing the container (or the object) on the second heating region 14. The second required power value of the second work coil 142 corresponding to the power level set by the user to the second heating region 14 is P2, and the driving frequency corresponding to the second required power value P2 is 22 kHz. Thus, the controller 2 sets the second driving frequency of the second work coil 142 to 22 kHz, and supplies the control signal to the second driving circuit 24. Thus, the second work coil 142 exhibits the resonance characteristic as the resonance characteristic curve 65. The second work coil 142 is driven at the driving frequency of 22 kHz, and the output power value of the second work coil 142 will be P2. At this time, the resonance frequency of the second work coil 142 is 22 kHz. That is, in the embodiment of Figure 15 , the resonance frequency of the first work coil 132 and the resonance frequency of the second work coil 142 are the same as each other.

[0187] When the first and second work coils 132 and 142 are driven to heat the container (or the object), the user reduces the power level of the first heating zone 12. If the power level of the first heating zone 12 is reduced, the required power value of the first work coil 132 is reduced from PI to P3.

[0188] The controller 2 determines a third drive frequency as a drive frequency corresponding to a third required power value P3, which is a new required power value of the work coil whose required power value is changed, i.e., the first work coil 132. As shown in FIG. 6, the third frequency corresponding to the third required power value P3 is 30 kHz. Figure 15

[0189] The controller 2 calculates a difference between the third drive frequency of the work coil whose required power value is changed and a drive frequency (second drive frequency) of the work coil (the second work coil 142) whose required power value is not changed. In the embodiment of FIG. 6, the difference between the third drive frequency (22 kHz) and the second drive frequency (30 kHz) is 8. Figure 13

[0190] The controller 2 confirms whether the calculated difference 8 is included in a first reference range (for example, 5 kHz or more and 20 kHz or less) set in advance. Since the calculated difference 8 is included in the first reference range and the operation mode of the first inverter circuit 204 is the full-bridge mode, the controller 2 changes the power control mode of the first inverter circuit 204 to either one of the asymmetric pulse width modulation mode and the phase shift mode.

[0191] If the power control mode of the first inverter circuit 204 is changed, the controller 2 keeps the drive frequency of the first work coil 132 as it is at the first drive frequency (22 kHz) and adjusts the output power value of the first work coil 132 to P3 by adjusting the duty ratio of the plurality of switching signals input to the first inverter circuit 204 or the phase difference between the plurality of switching signals input to the first inverter circuit 204. The controller 2 reduces the duty ratio of the plurality of switching signals input to the first inverter circuit 204 or increases the phase difference between the plurality of switching signals input to the first inverter circuit 204 so that the output power value of the first work coil 132 is reduced, so that the first work coil 132 has a new resonance characteristic like the resonance characteristic curve 66 shown in FIG. 6. Figure 16

[0192] As a result, as shown in FIG. 6, the first work coil 132 has a new resonance characteristic like the resonance characteristic curve 66 shown in FIG. 6. Figure 16 ​​​As shown, even if the output power value of the first work coil 132 is changed to P3, the drive frequency of the first work coil 132 and the drive frequency of the second work coil 142 are identical to each other. Therefore, even if the output power value of the first work coil 132 is changed from PI to P3, interference noise caused by the driving of the first work coil 132 and the second work coil 142 is not generated.

[0193] In Figure 15 and Figure 16 embodiments, the resonance frequency of the first work coil 132 and the resonance frequency of the second work coil 142 are identical to each other, and the first required power value PI of the first work coil 132 and the second required power value P2 of the second work coil 142 are identical to each other. However, even if the resonance frequency of the first work coil 132 and the resonance frequency of the second work coil 142 are not identical to each other, and the first required power value PI of the first work coil 132 and the second required power value P2 of the second work coil 142 are not identical to each other, the control method of the induction heating apparatus of the present application can be applied.

[0194] Figure 17 is a graph showing the resonance characteristic curves of the respective work coils when the required power value of the second work coil is changed in a state where the resonance frequency of the first work coil and the resonance frequency of the second work coil are identical to each other in another embodiment of the present application. In addition, Figure 18 is a graph showing the resonance characteristic curves of the respective work coils when the power control mode of the second work coil is changed in order to prevent interference noise in the embodiment of Figure 17 . Other embodiments and configurations can be provided.

[0195] Referring to Figure 17 , the user inputs a heating start instruction after placing a container (or an object) on the first heating region 12. The first required power value of the first work coil 132 corresponding to the power level set by the user to the first heating region 12 is PI, and the drive frequency corresponding to the first required power value PI is 22 kHz. Thus, the controller 2 sets the operation mode of the first inverter circuit 204 to the full-bridge mode, sets the first drive frequency of the first work coil 132 to 22 kHz, and supplies a control signal to the first drive circuit 22. Thus, the first work coil 132 exhibits the resonance characteristic as the resonance characteristic curve 65. The first work coil 132 is driven at the drive frequency of 22 kHz, and the output power value of the first work coil 132 will be PI. At this time, the resonance frequency of the first work coil 204 is 20 kHz.

[0196] The user inputs a heating start instruction after placing the container (or the object) in the second heating region 14. The second required power value of the second work coil 142 corresponding to the power level set by the user to the second heating region 14 is P2, and the driving frequency corresponding to the second required power value P2 is 22 kHz. Thus, the controller 2 sets the second driving frequency of the second work coil 142 to 22 kHz and supplies the control signal to the second driving circuit 24. Thus, the second work coil 142 exhibits the resonance characteristic as the resonance characteristic curve 65. The second work coil 142 is driven at the driving frequency of 22 kHz, and the output power value of the second work coil 142 will be P2. At this time, the resonance frequency of the second work coil 142 is 22 kHz. That is, in the embodiment, the resonance frequency of the first work coil 132 and the resonance frequency of the second work coil 142 are the same as each other. Figure 15

[0197] While the first work coil 132 and the second work coil 142 are driven to heat the container (or the object), the user reduces the power level of the second heating region 14. If the power level of the second heating region 14 is lowered, the required power value of the second work coil 142 is reduced from P2 to P3.

[0198] The controller 2 determines the third driving frequency as the driving frequency corresponding to the third required power value P3, which is the new required power value of the work coil whose required power value is changed, that is, the second work coil 142. As shown in FIG. 6, the third frequency corresponding to the third required power value P3 is 30 kHz. Figure 18

[0199] The controller 2 calculates the difference between the third driving frequency of the work coil whose required power value is changed and the driving frequency (the first driving frequency) of the work coil (the first work coil 132) whose required power value is not changed. In the embodiment, the difference between the third driving frequency (22 kHz) and the first driving frequency (30 kHz) is 8. Figure 17

[0200] The controller 2 confirms whether the calculated difference 8 is included in the first reference range (for example, 5 kHz or more and 20 kHz or less) set in advance. Since the calculated difference 8 is included in the first reference range and the operation mode of the second inverter circuit 214 is the half-bridge mode, the controller 2 changes the power control mode of the second inverter circuit 214 to the asymmetric pulse width modulation mode.

[0201] ​​​If the power control mode of the second inverter circuit 214 is changed, the controller 2 adjusts the output power value of the second work coil 142 to P3 by adjusting the duty ratio of the plurality of switching signals input to the second inverter circuit 214 while keeping the drive frequency of the second work coil 142 as it is to the second drive frequency (22 kHz) (step 506). The controller 2 reduces the duty ratio of the plurality of switching signals input to the second inverter circuit 214, so that the second work coil 122 has a new resonance characteristic like the resonance characteristic curve 67 shown in FIG. 6. Figure 18 As a result, as shown in FIG. 7, even if the output power value of the second work coil 142 is changed to P3, the drive frequency of the second work coil 142 and the drive frequency of the first work coil 132 are the same as each other. Therefore, even if the output power value of the second work coil 142 is changed from P2 to P3, interference noise caused by the driving of the first work coil 132 and the second work coil 142 does not occur.

[0202] As a result, as shown in FIG. 7, even if the output power value of the second work coil 142 is changed to P3, the drive frequency of the second work coil 142 and the drive frequency of the first work coil 132 are the same as each other. Therefore, even if the output power value of the second work coil 142 is changed from P2 to P3, interference noise caused by the driving of the first work coil 132 and the second work coil 142 does not occur. Figure 18 In the embodiment of FIGS. 1 to 6, the resonance frequency of the first work coil 132 and the resonance frequency of the second work coil 142 are the same as each other, and the first required power value P1 of the first work coil 132 and the second required power value P2 of the second work coil 142 are the same as each other. However, even if the resonance frequency of the first work coil 132 and the resonance frequency of the second work coil 142 are not the same as each other, and the first required power value P1 of the first work coil 132 and the second required power value P2 of the second work coil 142 are not the same as each other, the control method of the induction heating apparatus of the present application can be applied.

[0203] Figure 17 Figure 18 is a flowchart showing the control method of the induction heating apparatus of an embodiment of the present application. Other embodiments and configurations can also be provided.

[0204] Figure 19 is a flowchart showing the control method of the induction heating apparatus of an embodiment of the present application. Other embodiments and configurations can also be provided.

[0205] The controller 2 of the induction heating apparatus 10 drives the first work coil 132 at a first drive frequency corresponding to a first required power value set by a user (step 702). In addition, the controller 2 drives the second work coil 142 at a second drive frequency corresponding to a second required power value set by the user (step 704).

[0206] If the user changes the required power value of the first work coil 132 or the second work coil 142 to a third required power value in a state where the first work coil 132 and the second work coil 142 are driven, the controller 2 determines a third drive frequency corresponding to the third required power value (step 706).

[0207] ​​The controller 2 calculates a difference between the drive frequency of the working coil for which the required power value is not changed and the third drive frequency (step 708).

[0208] If the calculated difference is included in the first reference range set in advance, the controller 2 changes the operation mode or the power control mode of the first inverter circuit 204 or the second inverter circuit 214 (step 710).

[0209] In one embodiment of the present application, the step 710 of changing the operation mode or the power control mode of the first inverter circuit 204 or the second inverter circuit 214 includes a step of changing the operation mode of the first inverter circuit 204 to the half-bridge mode if the resonance frequency of the first working coil 132 is smaller than the resonance frequency of the second working coil 142 and the difference between the drive frequency of the working coil for which the required power value is not changed and the third drive frequency is included in the first reference range set in advance, and a step of changing the drive frequency of the first inverter circuit 204 to the fourth drive frequency corresponding to the third required power value.

[0210] In addition, in one embodiment of the present application, the step 710 of changing the operation mode or the power control mode of the first inverter circuit 204 or the second inverter circuit 214 includes a step of changing the power control mode of the working coil for which the required power value is changed to either one of the asymmetric pulse width modulation mode and the phase shift mode if the resonance frequency of the first working coil 132 is the same as the resonance frequency of the second working coil 142 and the difference between the drive frequency of the working coil for which the required power value is not changed and the third drive frequency is included in the first reference range set in advance, and a step of adjusting the output power value of the working coil for which the required power value is changed to be the same as the third required power value according to the changed power control mode.

[0211] In addition, in one embodiment of the present application, the step 710 of changing the operation mode or the power control mode of the first inverter circuit 204 or the second inverter circuit 214 includes a step of changing the power control mode to the asymmetric pulse width modulation mode if the operation mode of the working coil for which the required power value is changed is the half-bridge mode, and a step of changing the power control mode to either one of the asymmetric pulse width modulation mode and the phase shift mode if the operation mode of the working coil for which the required power value is changed is the full-bridge mode.

[0212] Referring to Figure 19 , by the step 710, after the change of the operation mode or the power control mode is completed, the controller 2 changes the output power value of the working coil for which the required power value is changed to the third required power value (step 712).

[0213] In an embodiment of the present application, the step 712 of changing the output power value of the work coil of the changed required power value to the third required power value includes, if the power control mode is set to the asymmetric pulse width modulation mode, changing the output power value of the work coil of the changed required power value to the third required power value by adjusting a duty ratio of a switching signal for driving the work coil of the changed required power value.

[0214] In addition, in an embodiment of the present application, the step 712 of changing the output power value of the work coil of the changed required power value to the third required power value includes, if the power control mode is set to the phase shift mode, changing the output power value of the work coil of the changed required power value to the third required power value by adjusting a phase difference between a plurality of switching signals for driving the work coil of the changed required power value.

[0215] The control method of the induction heating device can further include a step of changing the power control mode of the first inverter circuit 132 to the asymmetric pulse width modulation mode after the driving frequency of the first inverter circuit 132 is changed to the fourth driving frequency.

[0216] Although the present application has been described with reference to the example illustrated in the accompanying drawings, the present application is not limited to the embodiments and drawings disclosed in the present specification, but it is obvious that various modifications can be made by those skilled in the art within the scope of the technical idea of the present application. Also, even if the effects corresponding to the structural elements of the present application are not explicitly described in the process of describing the embodiments of the present application, the effects predictable from the corresponding structural elements should be recognized.

Claims

1. An inductive heating device, wherein comprises: a first working coil; a first inverter circuit supplying current to the first working coil according to a drive frequency from the first inverter circuit, the first working coil being driven at a first drive frequency corresponding to a first power value of the first working coil; a second working coil; a second inverter circuit supplying current to the second working coil according to a drive frequency from the second inverter circuit, the second working coil being driven at a second drive frequency corresponding to a second power value of the second working coil; and a controller determining a third drive frequency corresponding to a third power value if the power value of the first working coil is changed, determining a difference between the third drive frequency of the first working coil and the second drive frequency of the second working coil, changing an operation mode or a power control mode of the first inverter circuit and changing an output power value of the first working coil to the third power value if the determined difference is within a preset range, if the resonance frequency of the first working coil is less than the resonance frequency of the second working coil and the determined difference is within the preset range, the controller is configured to change the operation mode of the first inverter circuit to a half-bridge mode and change the drive frequency from the first inverter circuit to a fourth drive frequency corresponding to the third power value.

2. The induction heating device of claim 1, wherein the first inverter circuit comprises: a variable capacitor circuit; and a relay circuit connected to the variable capacitor circuit, the controller is configured to set a capacitance value of the variable capacitor circuit to Cr,h of Equation 1 below by turning on or off a plurality of relays included in the relay circuit: Equation 1 wherein fr,h is a value identical to a frequency of a switching signal input to the second inverter circuit, and Lr is an inductance value of a second inductor of the second inverter circuit.

3. The induction heating device of claim 1, wherein after the drive frequency from the first inverter circuit is changed to the fourth drive frequency, the controller is configured to change a power control mode of the first inverter circuit to an asymmetric pulse width modulation mode.

4. The induction heating device of claim 1, wherein if the resonance frequency of the first working coil is identical to the resonance frequency of the second working coil and the determined difference is within the preset range, the controller is configured to change a power control mode of the first inverter circuit to an asymmetric pulse width modulation mode or a phase shift mode and adjust an output power value of the first working coil to be identical to the third power value according to the power control mode.

5. The induction heating device of claim 4, wherein if the operation mode of the first inverter circuit is a half-bridge mode, the controller is configured to change the power control mode to the asymmetric pulse width modulation mode, If the operation mode of the first inverter circuit is the full-bridge mode, the controller is configured to change the power control mode to the asymmetric pulse width modulation mode or the phase shift mode. 6.The induction heating apparatus of claim 1, wherein, If the power control mode is set to the asymmetric pulse width modulation mode, the controller is configured to change the output power value of the first work coil to the third power value by adjusting a duty ratio of a switching signal for driving the first inverter circuit. 7.The induction heating apparatus of claim 1, wherein, If the power control mode is set to the phase shift mode, the controller is configured to change the output power value of the first work coil to the third power value by adjusting a phase difference between a plurality of switching signals for driving the first inverter circuit.

8. A control method of an induction heating device, wherein, comprising: a step of driving the first work coil at a first driving frequency corresponding to a first power value; a step of driving the second work coil at a second driving frequency corresponding to a second power value; a step of determining a third driving frequency corresponding to a third power value if the power value of the first work coil is changed to the third power value; a step of determining a difference between the third driving frequency of the first work coil and the second driving frequency of the second work coil; a step of changing an operation mode or a power control mode of a first inverter circuit supplying a current to the first work coil if the determined difference is within a pre-set range; and a step of changing the output power value of the first work coil to the third power value; the step of changing the operation mode or the power control mode of the first inverter circuit comprises: a step of changing the operation mode of the first inverter circuit to a half-bridge mode if the resonance frequency of the first work coil is less than the resonance frequency of the second work coil and the determined difference is within the pre-set range; and a step of changing a driving frequency from the first inverter circuit to a fourth driving frequency corresponding to the third power value. 9.The control method of the induction heating apparatus of claim 8, wherein, the first inverter circuit comprises: a variable capacitor circuit; and a relay circuit connected to the variable capacitor circuit, if the operation mode of the first inverter circuit is changed to the half-bridge mode, a capacitance value of the variable capacitor circuit is set to Cr,h of Equation 1 below by turning on or off a plurality of relays included in the relay circuit: Equation 1 wherein fr,h is a value identical to a frequency of a switching signal input to a second inverter circuit, and Lr is an inductance value of an inductor of the second inverter circuit. 10.The control method of the induction heating apparatus of claim 8, wherein, comprising: a step of changing a power control mode of the first inverter circuit to an asymmetric pulse width modulation mode after the driving frequency from the first inverter circuit is changed to the fourth driving frequency.

11. The control method of an induction heating apparatus according to claim 8, wherein the step of changing the operation mode or the power control mode of the first inverter circuit includes: the step of changing the power control mode of the first inverter circuit to an asymmetric pulse width modulation mode or a phase shift mode if the resonant frequency of the first work coil and the resonant frequency of the second work coil are the same and the determined difference value is included in a first reference range set in advance; and the step of adjusting the output power value of the first work coil to be the same as the third power value according to the power control mode.

12. The control method of an induction heating apparatus according to claim 11, wherein the step of changing the power control mode of the first inverter circuit includes: the step of changing the power control mode to the asymmetric pulse width modulation mode if the operation mode of the first inverter circuit is a half bridge mode; and the step of changing the power control mode to the asymmetric pulse width modulation mode or the phase shift mode if the operation mode of the first inverter circuit is a full bridge mode.

13. The control method of an induction heating apparatus according to claim 8, wherein the step of changing the output power value of the first inverter circuit includes: the step of changing the output power value of the first work coil to the third power value by adjusting a duty ratio of a switching signal for driving the first inverter circuit if the power control mode is set to an asymmetric pulse width modulation mode.

14. The control method of an induction heating apparatus according to claim 8, wherein the step of changing the output power value of the first inverter circuit includes: the step of changing the output power value of the first work coil to the third power value by adjusting a phase difference between a plurality of switching signals for driving the first inverter circuit if the power control mode is set to a phase shift mode.

15. A method of inductively heating a device, wherein includes: the step of controlling the first inverter circuit to drive the first work coil at a first drive frequency; the step of controlling the second inverter circuit to drive the second work coil at a second drive frequency; the step of determining a third drive frequency in response to a change in a power level of the first work coil; the step of determining a difference value between the third drive frequency and the second drive frequency; the step of changing a mode of the first inverter circuit according to the determined difference value; and the step of changing an output of the first work coil according to the changed mode; the step of changing the mode of the first inverter circuit includes: the step of changing an operation mode of the first inverter circuit to a half bridge mode if the resonant frequency of the first work coil is less than the resonant frequency of the second work coil and the determined difference value is in a range set in advance; and the step of changing a drive frequency from the first inverter circuit to a drive frequency corresponding to the changed power level.

16. The control method of an induction heating apparatus according to claim 15, wherein the step of changing the mode of the first inverter circuit includes: if the resonant frequency of the first work coil and the resonant frequency of the second work coil are the same and the determined difference is in a preset range, then changing the power control mode of the first inverter circuit to an asymmetric pulse width modulation mode or a phase shift mode; and adjusting the output of the first work coil according to the power control mode.

17. The method of inductively heating a device of claim 16, wherein, the step of changing the power control mode of the first inverter circuit includes: if the operation mode of the first inverter circuit is a half bridge mode, then changing the power control mode to the asymmetric pulse width modulation mode; and if the operation mode of the first inverter circuit is a full bridge mode, then changing the power control mode to the asymmetric pulse width modulation mode or the phase shift mode.

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