JP2017183141A - Electromagnetic induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic induction heating device ensuring big firepower, even when a heated body, such as a pot, floats from a top plate.SOLUTION: An electromagnetic induction heating device has a heating coil Lr0 for heating a heated object on a top plate, a resonance circuit Res0 having a heating coil and a resonance capacitor Cr0, an inverter circuit Inv0 for outputting power to the resonance circuit, and a control section Co0 for controlling the input power to the inverter circuit. when the heated object floats from the top plate, the control section sets the switching frequency of the inverter circuit lower than the switching frequency before the heated object floats from the top plate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electromagnetic induction heating apparatus such as an electromagnetic induction heating cooker.

  When a load such as a pan is placed on the top plate, an electromagnetic induction heating cooker causes a high-frequency current to flow from the high-frequency inverter to the heating coil, generating an eddy current in a metal pan placed close to the coil. Heat the pan by generating heat by the electrical resistance of the pan itself.

  When the pan was not placed on the top plate, the driving of the high frequency inverter was stopped to reduce power consumption, and the energization to the heating coil was stopped. However, when cooking the fried food by shaking the pan, the pan moves away from or approaches the heating coil, and heating and stopping are repeated, so the heating power applied to the pan becomes weak.

  On the other hand, the prior art described in Patent Document 1 is known. In this conventional technology, when it is determined that the pan is floating above the top plate, the drive signal of the high frequency inverter is fixed to the drive signal before the pan is lifted from the top plate, and the heating coil is energized. continue.

Japanese Patent Laying-Open No. 2015-50118

  In the above prior art, when the pan floats from the top plate, the inductance of the heating coil increases, and the resonance point shifts to the low frequency side. Therefore, when the pan is lifted from the top plate and operated at a driving frequency before the pan is lifted from the top plate, the output power is lower than that before the pan is lifted from the top plate, and thus the thermal power is reduced.

  Therefore, the present invention provides an electromagnetic induction heating device that can obtain a large heating power even when a heated object such as a pan floats from the top plate.

  In order to solve the above problems, an electromagnetic induction heating apparatus according to the present invention outputs a heating coil for heating an object to be heated on a top plate, a resonance circuit having a heating coil and a resonance capacitor, and outputs power to the resonance circuit. An inverter circuit, and a control unit that controls input power to the inverter circuit, wherein the control unit determines the switching frequency of the inverter circuit when the heated object floats from the top plate. Is lower than the switching frequency before floating from the top plate.

  ADVANTAGE OF THE INVENTION According to this invention, the thermal power in the case where a to-be-heated body floats from a top plate can be improved.

  Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS It is a basic block diagram of the electromagnetic induction heating apparatus which is Example 1 of this invention. An example of the relationship between the inductance and series resistance of a heating coil, and the distance from a top plate is shown. The relationship between input power and switching frequency is shown. The relationship between input power and switching frequency is shown. It is an example of an operation waveform of an inverter circuit in the case of using the control method indicated in patent documents 1. It is an example of the operation | movement waveform of an inverter circuit in the case of using the control means of the present Example 1. It is the elements on larger scale of the operation waveform shown in FIG. 3 is a flowchart illustrating a flow of power control processing according to the first embodiment. FIG. 9 is an operation waveform of the inverter circuit when the power control shown in FIG. 8 is used. FIG. 10 is a partial enlarged view of the operation waveform shown in FIG. 9. It is a basic block diagram of the electromagnetic induction heating apparatus which is Example 2 of this invention. It is a circuit block diagram of the electromagnetic induction heating apparatus in Example 2. The waveform of the gate drive signal of a switching element, the electric current which flows into a heating coil, and the voltage applied to a resonance circuit is shown. It is a basic block diagram of the electromagnetic induction heating apparatus which is Example 3 of this invention. 6 is a circuit configuration diagram of an electromagnetic induction heating device in Example 3. FIG. It is the waveform of the voltage applied to the gate drive signal of a switching element, the electric current which flows into a heating coil, and a heating coil. It is a circuit block diagram of the electromagnetic induction heating apparatus which is Example 4 of this invention. The waveform of the gate drive signal of a switching element, the electric current which flows into a heating coil, and the both-ends voltage of a switching element is shown. It is a basic block diagram of the electromagnetic induction heating apparatus which is Example 5 of this invention. It is a circuit block diagram of the electromagnetic induction heating apparatus in Example 5. The relationship between input power and switching frequency is shown. The relationship between input power and switching frequency is shown. It is the waveform of the voltage applied to the gate drive signal of a switching element, the electric current which flows into a heating coil, and a heating coil. It is a basic block diagram of the electromagnetic induction heating apparatus which is Example 6 of this invention. The relationship between input power and switching frequency is shown. The relationship between input power and switching frequency is shown. 12 is a flowchart illustrating a flow of power control processing according to the sixth embodiment. It is a basic block diagram of the electromagnetic induction heating apparatus which is Example 7 of this invention. The relationship between input power and switching frequency is shown. The relationship between input power and switching frequency is shown. 12 is a flowchart illustrating a flow of power control processing according to the seventh embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same reference numerals indicate the same constituent elements or constituent elements having similar functions.

  FIG. 1 is a basic configuration diagram of an electromagnetic induction heating apparatus that is Embodiment 1 of the present invention.

  As shown in FIG. 1, the electromagnetic induction heating device IH0 includes a top plate, a heating coil Lr0 that heats a pan that is a heated object placed on the top plate, and a pan on the top plate from a predetermined position. A pan position detection unit that detects movement, a resonance circuit Res0 having a heating coil Lr0 and a resonance capacitor Cr0, an inverter circuit Inv0 that inputs power from the AC power supply AC0 and outputs power to the resonance circuit Res0, and an inverter circuit It is comprised by the control part Co0 which controls the input electric power to Inv0.

  In the pan position detection unit, a known technique such as an induction type or a capacity type can be applied. Moreover, you may detect the position of a pan based on the calculated value of any of series resistance, an inductance, and the resonance frequency mentioned later, or its change.

  The control unit Co0 calculates the inductance value of the heating coil Lr0 in the actual operation state of the circuit from the pan operation determination unit that determines whether or not the pan has floated based on the output of the pan position detection unit and the circuit operation of the inverter circuit. An inductance calculating unit L_ca0, a resonance frequency calculating unit Fr_ca0 that calculates a resonance frequency from the inductance value calculated by the inductance calculating unit L_ca0 and the capacitance value of the resonance capacitor Cr0, an inverter from the resonance frequency calculated by the resonance frequency calculating unit Fr_ca0 A lower limit frequency setting unit Fr_lim0 for setting a lower limit value of a switching frequency for driving the circuit, a power command value setting unit for reading an input power command value from the operation unit and setting an input power command value to the inverter circuit Inv0, and a lower limit The lower limit set by the frequency setting unit Fr_lim0 Based on the value of the input power command which is set by the value of the etching frequency and power instruction value setting unit, and a drive signal generating unit Driver0 for generating a drive signal of the inverter circuit.

  The control unit Co0 is configured using an arithmetic processing device such as a microcomputer, for example, and functions as each unit of the control unit Co0 when the arithmetic processing device executes a predetermined program.

  FIG. 2 shows the distance between the top plate and the pan when the pan is separated from the top plate in a direction perpendicular to the top surface of the top plate, the inductance and series resistance of the heating coil, and the top plate. An example of the relationship with the distance from is shown. However, the material which comprises a pan is SUS304. Note that the relationship example in FIG. 2 was obtained by the study of the present inventors.

  As shown in the upper diagram of FIG. 2, when the top plate and the pan are close to each other, the magnetic field generated from the eddy current flowing in the pan cancels the magnetic field generated from the heating coil, so that the inductance is low. Further, when the pan is moved away from the top plate, the eddy current flowing through the pan is reduced, and the magnetic field generated from the heating coil is not canceled, so that the inductance is increased.

  As shown in the lower diagram of FIG. 2, when the top plate and the pan are close to each other, the series resistance increases due to the resistance of the pan. In addition, when the pan is moved away from the top plate, the effect of the pan resistance is reduced, and the series resistance value is decreased.

  In addition, the same relationship is shown also with the pan comprised with materials other than SUS304.

  3 and 4 show the relationship between the input power to the inverter circuit and the switching frequency of the inverter circuit when the pan moves away from the top plate in the first embodiment. When the pan floats from the top plate, the inductance value of the heating coil increases (see the upper diagram of FIG. 2), so that the resonance frequency decreases from fr1 to fr2. On the other hand, when the pan floats from the top plate, the series resistance of the heating coil is reduced (see the lower diagram in FIG. 2), so the Q value increases.

  As shown in FIG. 3, with the pan placed on the top plate and the inverter operating at the switching frequency fsw1 and outputting power P1 (at this time, the input power command value is P1), the pan is moved from the top plate. Since the inverter still outputs the electric power P1 even when floating, the switching frequency is lowered to fsw2. In addition, as shown in FIG. 4, when the pan is floating from the top plate, the inverter operates at the switching frequency fsw2 and outputs the electric power P1, and even if the pan is brought close to the top plate, the inverter still has the electric power P1. To increase the switching frequency to fsw1. Thus, when the pan floats from the top plate, the output power of the inverter is controlled to a constant value by adjusting the switching frequency of the inverter in accordance with the fluctuation of the resonance frequency. Thereby, the thermal power in the case of floating a pan from a top plate improves.

  FIG. 5 is an operation waveform example of the inverter circuit when normal power control is performed for 1 second using the control method described in Patent Document 1 described above, and then the pan is shaken twice in 1 second. When the pot shake cooking is started, since the inductance L increases (15.5 μH → 37.7 μH), the resonance frequency decreases. For this reason, when the switching frequency is fixed even after starting the pot cooking, the electric power actually input with respect to the input electric power command value is greatly reduced. Therefore, it is difficult to obtain sufficient thermal power in the case of cooking in a pot.

  FIG. 6 is an example of operation waveforms of the inverter circuit when normal power control is performed for 1 second using the control means in the first embodiment described in FIGS. 3 and 4 and then the pan is shaken twice in 1 second. is there. Even during cooking in a pot, the input power detection value fluctuates, but on average, it is equivalent to that before cooking in a pot. Here, when the pan is moved closer to the top plate, relatively large instantaneous power (4.87 kW) is applied to the inverter circuit. This is because according to the study of the present inventor, the response of the switching frequency cannot always follow the fluctuation of the resonance frequency.

  FIG. 7 is a partial enlarged view of the operation waveform shown in FIG. 6, and the circuit operation when a large instantaneous electric power is applied to the inverter circuit when the pan is moved from the far side of the top plate toward the top plate during cooking in a pot. Indicates. While the resonance frequency increases as the pan approaches the top plate, the resonance frequency and the switching frequency are close to each other due to the delay in response of the switching frequency of the inverter circuit, and a large instantaneous power is input.

  Therefore, in the first embodiment, the control operation described below is further performed using the lower limit frequency setting unit Fr_lim0.

  FIG. 8 is a flowchart illustrating the flow of the power control process executed by the electromagnetic induction heating device according to the first embodiment.

  In step 1, the control unit Co0 reads the power command value input from the operation unit.

  In Step 2, the control unit Co0 outputs a drive signal from the drive signal generation unit Driver0 to the inverter based on the read power command value, and starts heating the pot.

  In Step 3, the control unit Co0 determines whether or not the pan is lifted by the pan position detection unit. When it determines with the pan not floating (No of step 3), the control part Co0 performs the process after step 1 again. When it is determined that the pan is floating (Yes in Step 3), the control unit Co0 executes the process in Step 4.

  In step 4, the control unit Co0 calculates the inductance value in the actual operation state of the heating coil Lr0 from the circuit operation of the inverter circuit Inv0 by the inductance calculation unit L_ca0.

  Next, in step 5, the control unit Co0 calculates the resonance frequency in the actual operation state of the circuit by the resonance frequency calculation unit Fr_ca0 based on the calculation result of the inductance calculation unit L_ca0.

  Next, in step 6, the control unit Co0 sets the lower limit value of the switching frequency of the inverter circuit Inv0 by the lower limit frequency setting unit Fr_lim0 based on the calculation result of the resonance frequency calculation unit Fr_ca0.

  Next, in step 7, the control unit Co0 generates a drive signal by the drive signal generation unit Driver0 and drives the inverter circuit Inv0 within the frequency range set by the lower limit frequency setting unit Fr_lim0.

  Note that after executing the process of step 7, the process of the control unit Co0 returns to START (RETURN).

  According to the power control shown in FIG. 8, the lower limit value of the switching frequency is set based on the resonance frequency in the actual operation state, thereby preventing the resonance frequency and the switching frequency from being close to each other. For this reason, it can suppress that excessive electric power is applied to inverter circuit Inv0.

  FIG. 9 shows operation waveforms of the inverter circuit Inv0 when normal power control is performed for 1 second using the power control shown in FIG. 8, and then the pan is shaken twice in 1 second.

  As shown in FIG. 9, when cooking the pot, in order to reduce the switching frequency of the inverter circuit Inv0 in accordance with the decrease in the resonance frequency, relatively large power is input to the inverter circuit Inv0, Firepower is increasing. Moreover, since the switching frequency and the resonance frequency are prevented from approaching when the pan is returned, application of large instantaneous power is suppressed.

  FIG. 10 is a partially enlarged view of the operation waveform shown in FIG. 9, and shows circuit operation when the pan is brought closer to the top plate from a distance from the top plate during cooking in the pot. As shown in FIG. 10, in the first embodiment, the lower limit value of the switching frequency of the inverter circuit Inv0 is set to a value provided with a predetermined margin (3 kHz in FIG. 10) from the resonance frequency calculated by the resonance frequency calculation means Fr_lim0. Therefore, the switching frequency and the resonance frequency are not close to each other, and a large instantaneous power is not input. That is, it is possible to achieve both the improvement in heating power during cooking in a pot and the suppression of application of excessive power.

  FIG. 11 is a basic configuration diagram of an electromagnetic induction heating apparatus that is Embodiment 2 of the present invention.

  As shown in FIG. 11, the electromagnetic induction heating device IH1 includes a top plate, a heating coil Lr1 for heating the pan on the top plate, and a pan position detection for detecting that the pan on the top plate has moved from a predetermined position. , A resonance circuit Res1 having a heating coil Lr1 and a resonance capacitor Cr1, an inverter circuit Inv1 that inputs power from the AC power supply AC1 and outputs power to the resonance circuit Res1, and a control that controls input power to the inverter circuit Inv1 Unit Co1, a power detection unit Ps1 that detects input power to the inverter circuit, a voltage detection unit Vs1 that detects the output voltage of the inverter circuit, a current detection unit Cs1 that detects a current flowing through the heating coil, and a voltage detection unit A phase difference detector P for detecting a phase difference between the AC voltage detected by Vs1 and the AC current detected by the current detector Cs1. Constituted by the s1.

  The control unit Co1 includes an inductance calculation unit L_ca1 that calculates an inductance value in an actual operation state of the circuit based on the values of each electric quantity detected by the power detection unit Ps1, the current detection unit Cs1, and the phase difference detection unit Phs1, and an inductance calculation. The resonance frequency calculation unit Fr_ca1 that calculates the resonance frequency in the actual operation state of the circuit from the inductance value calculated by the unit L_ca1, and the lower limit value of the switching frequency that drives the inverter circuit is set from the resonance frequency calculated by the resonance frequency calculation unit Fr_ca1 The lower limit frequency setting unit Fr_lim1 and the drive signal generation unit Driver1 that generates the drive signal of the inverter circuit based on the lower limit value of the switching frequency set by the lower limit frequency setting unit Fr_lim1.

  FIG. 12 is a circuit configuration diagram of the electromagnetic induction heating device IH1 in the present embodiment, and shows the main circuit portion including the inverter circuit Inv1 shown in FIG. 11 in more detail.

  As shown in FIG. 12, the main circuit portion of the electromagnetic induction heating device IH1 includes an AC / DC conversion circuit ACDC1, an inverter circuit Inv1, and a resonance circuit Res1 that input power from an AC power supply AC1.

  The inverter circuit Inv1 is configured by a single-phase bridge circuit including switching elements Q11, Q12, Q13, and Q14. That is, the inverter circuit Inv1 includes a first switching leg in which the switching elements Q11 and Q12 are connected in series, and a second switching leg in which the switching elements Q13 and Q14 are connected in series, and a series connection point of the switching elements Q11 and Q12, The series connection point of switching elements Q13 and Q14 is an AC terminal from which high-frequency power is output.

  The inverter circuit Inv1 outputs high-frequency power between the node Nd11 and the node Nd12 by turning on and off the switching elements Q11 to Q14 at a high speed by the gate drive signal generated by the drive signal generation unit Driver1. Diodes D11, D12, D13, and D14 are connected in antiparallel to switching elements Q11, Q12, Q13, and Q14, respectively. The diodes D11 to D14 operate as freewheeling diodes.

  In the second embodiment, n-channel IGBTs (Insulated Gate Bipolar Transistors) are used as the switching elements Q11 to Q14. Here, when using MOSFET as these switching elements Q11-Q14, since the parasitic diode of MOSFET can be utilized, the diodes D11-D14 can be omitted.

  The resonance circuit Res1 is composed of a heating coil Lr1 and a resonance capacitor Cr1 connected in series, and high frequency power is supplied from the inverter circuit Inv1 to the heating coil Lr1, and the pan on the top plate is heated.

  FIG. 13 shows the gate drive signals VGEQ11 to VGEQ14 of the switching elements Q11 to Q14, the current ILr1 flowing through the heating coil Lr1, and the voltages VNd11 to Nd12 applied to the resonance circuit Res1 when the switching elements Q11 to Q14 are turned on / off. Waveform is shown.

  In the electromagnetic induction heating device IH1, the switching element Q11 and the switching element Q12 are complementarily turned on / off by the gate drive signals VGEQ11 to VGEQ14, and the switching element Q13 and the switching element Q14 are complementarily turned on / off. . During the period when the switching element Q11 and the switching element Q14 are simultaneously turned on, the output voltage of the AC / DC conversion circuit ACDC1 is applied in the positive direction to the resonance circuit Res1, and due to the series resonance phenomenon of the heating coil Lr1 and the resonance capacitor Cr1, A substantially sinusoidal current ILr1 as shown in FIG. 13 flows through the heating coil Lr1. Further, during the period when the switching element Q12 and the switching element Q13 are simultaneously turned on, the output voltage of the AC / DC conversion circuit ACDC1 is applied in the reverse direction to the resonance circuit Res1, and the series resonance phenomenon of the heating coil Lr1 and the resonance capacitor Cr1. As a result, a substantially sinusoidal current ILr1 as shown in FIG. 13 flows through the heating coil Lr1.

  The operations of the inductance calculation unit Lr_ca1 and the resonance frequency calculation unit Fr_ca1 will be described with reference to FIG.

  In the state of FIG. 13, the inverter circuit Inv1 receives power Pin1 from the AC power supply AC1, turns on and off the switching elements Q11 to Q14 at the switching frequency fsw1, and outputs a voltage of VNd11-Nd12 to the resonance circuit. Thereby, the high frequency current ILr1 flows through the heating coil Lr1, and the pan on the top plate is heated. At this time, the series resistance Rs1 of the resonance circuit is expressed by Expression (1).

Rs1 = Pin1 / ILr1 ² (1)
Further, the angular frequency ω1 of the resonance circuit Res1 is expressed by the equation (2) using fsw1.

ω1 = 2πfsw1 (2)
The inductance value Lr1 in the actual operation state of the circuit is the series resistance Rs1, the voltage applied to the resonance circuit, that is, the phase difference φ1 between the output voltage of the inverter circuit and the current flowing through the heating coil, the capacitance value Cr1 of the resonance capacitor, and the resonance circuit Res1. It is expressed by equation (3) using the angular frequency ω1.

Lr1 = (Rs1 · tan φ1 / ω1) + (1 / (ω1 ² · Cr1)) (3)
Based on the above equations (1), (2), and (3), the inductance calculator L_ca1 calculates the inductance value in the actual operation state of the circuit.

  Next, the operation of the resonance frequency calculation unit Fr_ca1 will be described.

  The resonance frequency fr1 in the actual operation state of the circuit is expressed by Expression (4) using the inductance Lr1 and the capacitance value Cr1 of the resonance capacitor.

fr1 = 1 / (2π (Lr1 · Cr1) ^1/2 ) (4)
The resonance frequency in the actual operation state of the circuit calculated by the resonance frequency calculation unit Fr_ca1 is output to the lower limit frequency setting unit Fr_lim1. In the lower limit frequency setting unit Fr_lim1, a margin is set in order to avoid the switching frequency fsw1 of the inverter circuit Inv1 and the resonance frequency fr1 from being close to each other. The lower limit frequency setting unit Fr_lim1 sets the lower limit value of the switching frequency for driving the inverter circuit Inv1, and the drive signal generation unit Driver1 drives the inverter circuit Inv1 based on the lower limit value of the switching frequency set by the lower limit frequency setting unit Fr_lim1. Signals (VGEQ11 to VGEQ14) are generated.

  As described above, in the electromagnetic induction heating device IH1 of the second embodiment, the inductance value in the actual operation state of the circuit is calculated, and the switching frequency fsw1 of the inverter circuit Inv1 and the resonance frequency fr1 are avoided from being close to each other. Thus, it is possible to improve the thermal power when the pan is lifted and to suppress the application of excessive power when the pan is returned.

  FIG. 14 is a basic configuration diagram of an electromagnetic induction heating apparatus that is Embodiment 3 of the present invention.

  As shown in FIG. 14, the electromagnetic induction heating device IH2 includes a top plate, a heating coil Lr2 for heating the pan on the top plate, and a pan position detection for detecting that the pan on the top plate has moved from a predetermined position. , A resonance circuit Res2 having a heating coil Lr2 and a resonance capacitor Cr2, an inverter circuit Inv2 that inputs power from the AC power supply AC2 and outputs power to the resonance circuit Res2, and a control that controls input power to the inverter circuit Inv2 Part Co2, voltage detection part Vs2 for detecting the voltage applied to heating coil Lr2, current detection part Cs2 for detecting the current flowing through the heating coil, AC voltage detected by voltage detection part Vs2 and current detection part Cs2 The phase difference detection unit Phs2 detects the phase difference of the detected alternating current.

  The control unit Co2 includes an inductance calculation unit L_ca2 that calculates an inductance value in an actual operation state of the circuit based on each value detected by the voltage detection unit Vs2, the current detection unit Cs2, and the phase difference detection unit Phs2, and an inductance calculation unit L_ca2. The resonance frequency calculation unit Fr_ca2 that calculates the resonance frequency in the actual operation state of the circuit from the calculated inductance value, and the lower limit frequency that sets the lower limit value of the switching frequency that drives the inverter circuit from the resonance frequency calculated by the resonance frequency calculation unit Fr_ca2 Based on the setting unit Fr_lim2 and the lower limit value of the switching frequency set by the lower limit frequency setting unit Fr_lim2, the driving signal generation unit Driver2 generates a drive signal for the inverter circuit.

  FIG. 15 is a circuit configuration diagram of the electromagnetic induction heating device IH2 in the present embodiment, in which the main circuit portion including the inverter circuit Inv2 shown in FIG. 14 is described in more detail.

  As shown in FIG. 15, the main circuit portion of the electromagnetic induction heating device IH2 includes an AC / DC conversion circuit ACDC2, an inverter circuit Inv2, and a resonance circuit Res2 that input power from an AC power supply AC2.

  The inverter circuit Inv2 is configured by a single-phase bridge circuit including switching elements Q21, Q22, Q23, and Q24, and the switching elements Q21 to Q24 are turned on / off at high speed by a gate drive signal created by the drive signal generation unit Driver2. Thus, high frequency power is output between the node Nd21 and the node Nd22. Diodes D21, D22, D23, and D24 are connected in reverse parallel to switching elements Q21, Q22, Q23, and Q24, respectively. The diodes D21 to D24 operate as freewheeling diodes.

  In the third embodiment, n-channel IGBTs are used as the switching elements Q21 to Q24. Here, when MOSFETs are used as the switching elements Q21 to Q24, parasitic diodes of the MOSFETs can be used, so that the diodes D21 to D24 can be omitted.

  The resonance circuit Res2 includes a heating coil Lr2 and a resonance capacitor Cr2 connected in series, and high frequency power is supplied from the inverter circuit Inv2 to the heating coil Lr2 to heat the pan on the top plate.

  FIG. 16 shows waveforms of the gate drive signals VGEQ21 to VGEQ24 of the switching elements Q21 to Q24, the current ILr2 flowing through the heating coil Lr2, and the voltage VLr2 applied to the heating coil Lr2 when the switching elements Q21 to Q24 are turned on / off. is there.

  In the electromagnetic induction heating device IH2, similarly to the electromagnetic induction heating device IH1 of the second embodiment, the switching element Q21 and the switching element Q22 are repeatedly turned on and off in a complementary manner, and the switching element Q23 and the switching element Q24 are complementarily turned on.・ Repeat off. During the period when the switching element Q21 and the switching element Q24 are simultaneously turned on, the output voltage of the AC / DC conversion circuit ACDC2 is applied in the positive direction to the resonance circuit Res2, and due to the series resonance phenomenon of the heating coil Lr2 and the resonance capacitor Cr2, A substantially sinusoidal current ILr2 as shown in FIG. 16 flows through the heating coil Lr2. Further, during the period when the switching element Q22 and the switching element Q23 are simultaneously turned on, the output voltage of the AC / DC conversion circuit ACDC2 is applied in the reverse direction to the resonance circuit Res2, and the series resonance phenomenon of the heating coil Lr2 and the resonance capacitor Cr2 As a result, a sinusoidal current ILr2 as shown in FIG. 16 flows through the heating coil Lr2.

  The operations of the inductance calculation unit Lr_ca2 and the resonance frequency calculation unit Fr_ca2 will be described with reference to FIG.

  In the state of FIG. 16, the inverter circuit Inv2 receives power from the AC power supply AC2, and the inverter circuit Inv2 turns on and off the switching elements Q21 to Q24 at the switching frequency fsw2 and outputs the high frequency voltage VLr2 to the heating coil. Thereby, the high frequency current ILr2 flows through the heating coil Lr2, and the pan on the top plate is heated. At this time, the angular frequency ω2 of the resonance circuit Res2 is expressed by Expression (5).

ω2 = 2πfsw2 (5)
The inductance value Lr2 in the actual operation state of the circuit includes the voltage VLr2 applied to the heating coil Lr2, the current ILr2 flowing through the heating coil Lr, the phase difference φ2 between the voltage applied to the heating coil and the current flowing through the heating coil, the resonance circuit Res2 This is expressed by Expression (6) using the angular frequency ω2.

Lr2 = (VLr2 / ILr2). (Sin φ2 / ω2) (6)
Based on the above equations (5) and (6), the inductance calculator L_ca2 calculates the inductance value Lr2 in the actual operation state of the circuit.

  Next, the operation of the resonance frequency calculation unit Fr_ca2 will be described.

  The resonance frequency fr2 in the actual operation state of the circuit is expressed by Expression (7) using the inductance Lr2 and the capacitance value Cr2 of the resonance capacitor.

fr2 = 1 / (2π (Lr2 · Cr2) ^1/2 ) (7)
The resonance frequency in the actual operation state of the circuit calculated by the resonance frequency calculation unit Fr_ca2 is output to the lower limit frequency setting unit Fr_lim2. In the lower limit frequency setting unit Fr_lim2, a margin is set to avoid the switching frequency fsw2 of the inverter circuit Inv2 and the resonance frequency fr2 from being close to each other. The lower limit frequency setting unit Fr_lim2 sets the lower limit value of the switching frequency for driving the inverter circuit Inv2, and the drive signal generation unit Driver2 drives the inverter circuit Inv2 based on the lower limit value of the switching frequency set by the lower limit frequency setting unit Fr_lim2 Signals (VGEQ21 to VGEQ24) are generated.

  As described above, in the electromagnetic induction heating device IH2 of the third embodiment, the inductance value in the actual operation state of the circuit is calculated, and the switching frequency fsw2 of the inverter circuit Inv2 and the resonance frequency fr2 are avoided from being close to each other. Thus, it is possible to improve the thermal power when the pan is lifted and to suppress the application of excessive power when the pan is returned.

  FIG. 17 is a circuit configuration diagram of an electromagnetic induction heating device that is Embodiment 4 of the present invention. In the fourth embodiment, the configuration of the main circuit portion is different from those in the second and third embodiments.

  As shown in FIG. 17, the electromagnetic induction heating device IH2 is a power detection unit that detects input power to an AC / DC conversion circuit ACDC2, an inverter circuit Inv2, a resonance circuit Res2, and an inverter circuit Inv2 that input power from an AC power supply AC2. Part Ps2, voltage detection parts Vs21 and Vs22 for detecting the output voltage of the inverter circuit Inv2, current detection part Cs2 for detecting the current flowing in the heating coil, AC voltage detected by the voltage detection parts Vs21 and Vs22 and the current detection part Cs2 A phase difference detection unit Phs2, a power detection unit Ps2, and a current detection unit Cs2 for detecting the phase difference of the alternating current.

  Further, as shown in FIG. 17, the electromagnetic induction heating device IH2 includes an inductance calculation unit L_ca2 that calculates an inductance value in an actual operation state of the circuit based on the value of each electric quantity detected by the phase difference detection unit Phs2, and an inductance The resonance frequency calculation unit Fr_ca2 that calculates the resonance frequency in the actual operation state of the circuit from the inductance value calculated by the calculation unit L_ca2, and the lower limit value of the switching frequency that drives the inverter circuit from the resonance frequency calculated by the resonance frequency calculation unit Fr_ca2 Based on the lower limit frequency setting unit Fr_lim2 to be set and the lower limit value of the switching frequency set by the lower limit frequency setting unit Fr_lim2, a drive signal generation unit Driver2 that generates a drive signal for the inverter circuit is provided.

  The inverter circuit Inv2 is configured by a half bridge circuit including switching elements Q21 and Q22. That is, the inverter circuit Inv2 includes one switching leg to which the switching elements Q21 and Q22 are connected in series. The resonant capacitor is constituted by a series connection body of a capacitor Cr21 and a capacitor Cr22. Such a resonant capacitor is connected in parallel to the switching leg. The series connection point of switching elements Q21 and Q22 and the series connection point of capacitors Cr21 and Cr22 serve as an AC terminal from which high-frequency power is output.

  The switching elements Q21 and Q22 are turned on / off at high speed by the gate drive signal generated by the drive signal generator Driver2, thereby outputting high-frequency power between the node Nd21 and the node Nd22 and between the node Nd22 and the node Nd23. Diodes D21 and D22 are connected in antiparallel to switching elements Q21 and Q22, respectively. Here, when MOSFETs are used as the switching elements Q21 and Q22, since the parasitic diodes of the MOSFETs can be used, the diodes D21 and D22 can be omitted.

  18 shows the gate drive signals VGEQ21 and VGEQ22 of the switching elements Q21 and Q22 when the switching elements Q21 and Q22 are turned on / off, the current ILr2 flowing through the heating coil Lr2, the voltage VNd21-Nd22 across the switching element Q21, The waveform of the both-ends voltage VNd22-Nd23 of Q22 is shown.

  In the electromagnetic induction heating device IH2 according to the fourth embodiment, the switching element Q21 and the switching element Q22 are repeatedly turned on and off in a complementary manner. By turning the switching elements Q21 and Q22 on and off, a substantially sinusoidal current ILr2 flows through the heating coil Lr2 due to the resonance phenomenon of the heating coil Lr2 and the resonant capacitors Cr21 and Cr22.

  The operations of the inductance calculation unit Lr_ca2 and the resonance frequency calculation unit Fr_ca2 will be described with reference to FIG.

  In the state of FIG. 18, the inverter circuit Inv2 receives power Pin2 from the AC power supply AC2, turns on and off the switching elements Q21 and Q22 at the switching frequency fsw2, and causes the high-frequency current ILr2 to flow through the heating coil Lr. At this time, the series resistance Rs2 of the resonance circuit is expressed by Expression (8).

Rs2 = Pin2 / ILr2 ² (8)
Further, the angular frequency ω2 of the resonance circuit Res2 is expressed by Expression (9) using fsw2.

ω2 = 2πfsw2 (9)
The inductance value Lr2 in the actual operation state of the circuit is expressed by using the series resistance Rs2, the phase difference φ2 between the voltage applied to the resonance circuit and the current flowing through the heating coil, the capacitance values Cr21 and Cr22 of the resonance capacitor, and the switching frequency ω2. 10).

Lr2 = (Rs2 / tan φ2 / ω2) + (1 / (ω2 ² (Cr21 + Cr22)) (10)
Based on the above equations (8), (9), and (10), the inductance calculation unit L_ca2 calculates the inductance value in the actual operation state of the circuit.

  Next, the operation of the resonance frequency calculation unit Fr_ca2 will be described.

  The resonance frequency fr2 in the actual operation state of the circuit is expressed by Expression (11) using the inductance Lr2 and the capacitance values Cr21 and Cr22 of the resonance capacitor.

fr2 = 1 / (2π (Lr2 (Cr21 + Cr22)) ^1/2 ) (11)
The resonance frequency fr2 in the actual operation state of the circuit calculated by the resonance frequency calculation unit Fr_ca2 is output to the lower limit frequency setting unit. In the lower limit frequency setting unit Fr_lim2, a margin is set to avoid the switching frequency fsw2 of the inverter circuit Inv2 and the resonance frequency fr2 from being close to each other. The lower limit frequency setting unit Fr_lim2 sets the lower limit value of the switching frequency for driving the inverter circuit Inv2, and the drive signal generation unit Driver2 drives the inverter circuit Inv2 based on the lower limit value of the switching frequency set by the lower limit frequency setting unit Fr_lim2 Signals (VGEQ21, VGEQ22) are generated.

  As described above, in the electromagnetic induction heating device IH2 of the fourth embodiment, the inductance value in the actual operation state of the circuit is calculated, and the switching frequency fsw2 of the inverter circuit Inv2 and the resonance frequency fr2 are avoided from being close to each other. Thus, it is possible to improve the thermal power when the pan is lifted and to suppress the application of excessive power when the pan is returned. Further, since the number of switching elements in the inverter circuit is reduced, power loss and cost can be reduced.

  FIG. 19 is a basic configuration diagram of an electromagnetic induction heating device IH3 that is Embodiment 5 of the present invention. In the fifth embodiment, unlike the second and fourth embodiments, no input power detection means is provided, and a voltage application time detection unit for the heating coil is provided.

  As shown in FIG. 19, the electromagnetic induction heating device IH3 includes a top plate, a heating coil Lr3 for heating the pan on the top plate, and a pan position detection for detecting that the pan on the top plate has moved from a predetermined position. , A resonance circuit Res3 having a heating coil Lr3 and a resonance capacitor Cr3, an inverter circuit Inv3 that inputs power from the AC power supply AC3 and outputs power to the resonance circuit Res3, and a control that controls input power to the inverter circuit Inv3 Part Co3, a voltage application time detection part Tons for detecting the time for applying the output voltage of the inverter circuit Inv3 to the heating coil Lr3, a voltage detection part Vs3 for detecting the voltage applied to the heating coil Lr3, and the heating coil Lr3 It is comprised with the electric current detection part Cs3 which detects the electric current which flows.

  FIG. 20 is a circuit configuration diagram of the electromagnetic induction heating device IH3 in the present embodiment, in which the main circuit portion including the inverter circuit Inv3 shown in FIG. 19 is described in more detail.

  As shown in FIG. 20, the electromagnetic induction heating device IH3 includes an AC / DC conversion circuit ACDC3 that receives power from an AC power supply AC3, an inverter circuit Inv3, a switching element Q3 that constitutes the inverter circuit Inv3, a resonance circuit Res3, and a switching element Q3. Detects the voltage applied to the heating coil Lr3 when the voltage is on, the voltage detection unit Vs3 that detects the voltage applied to the heating coil Lr3, the current detection unit Cs3 that detects the current flowing through the heating coil Lr3, and the time during which the voltage is applied to the heating coil Lr3 A voltage application time detection unit Tons.

  Furthermore, as shown in FIG. 20, the electromagnetic induction heating device IH2 includes an inductance calculation unit L_ca3 that calculates the inductance value of the heating coil in the actual operation state of the circuit based on each detection value detected by the voltage application time detection unit Tons. The resonance frequency calculation unit Fr_ca3 that calculates the resonance frequency in the actual operation state of the circuit from the inductance value calculated by the inductance calculation unit L_ca3, and the lower limit value of the switching frequency that drives the inverter circuit from the resonance frequency calculated by the resonance frequency calculation unit Fr_ca3 Based on the lower limit value of the switching frequency set by the lower limit frequency setting unit Fr_lim3 and the lower limit frequency setting unit Fr_lim3 to be set, a drive signal generation unit Driver3 that generates a drive signal of the inverter circuit is provided.

  Here, the inverter circuit Inv3 includes one switching element Q3. The resonance circuit Res3 includes a parallel circuit of the heating coil Lr3 and the resonance capacitor Cr3, and the parallel circuit and the switching element Q3 are connected in series.

  In the electromagnetic induction heating device IH3, the voltage output from the ACDC3 is applied to the heating coil Lr3 while the switching element Q3 is on. Therefore, the heating coil Lr3 accumulates energy, and the current flowing through the heating coil Lr3 is Increase. Further, the heating coil Lr3 and the resonance capacitor Cr3 resonate while the switching element Q3 is off, and the energy accumulated in the heating coil Lr3 reciprocates between the resonance capacitor Cr3 and the heating coil Lr3. That is, the electromagnetic induction heating device IH3 outputs high-frequency power between the node Nd31 and the node Nd32 by turning on and off the switching element Q3 at high speed. A diode D3 is connected in reverse parallel to the switching element Q3.

  In the fifth embodiment, an n-channel IGBT is used as the switching element Q3. Here, when a MOSFET is used as the switching element Q3, a parasitic diode of the MOSFET can be used, and thus the diode D3 can be omitted.

  The resonance circuit Res3 includes a heating coil Lr3 and a resonance capacitor Cr3 that are connected in parallel to each other, and high frequency power is supplied to the heating coil Lr3 by turning on and off the switching element Q3.

  21 and 22 show the relationship between the input power to the inverter circuit and the switching frequency of the inverter circuit when the pan moves away from the top plate. In FIGS. 21 and 22, similarly to FIGS. 3 and 4, the fluctuation of the operating point when the input power is controlled to be constant even if the position of the pan fluctuates is shown.

  When the pan floats from the top plate, the inductance value of the heating coil increases (see the upper diagram of FIG. 2), and the resonance frequency decreases from fr3 to fr4. On the other hand, when the pan floats from the top plate, the resistance value of the heating coil decreases (see the lower diagram in FIG. 2), and the Q value increases.

  In the electromagnetic induction heating device IH3 of the fifth embodiment, unlike the first to fourth embodiments, a parallel resonance circuit is applied. For this reason, the fifth embodiment and the first to fourth embodiments have a so-called dual relationship with respect to current and voltage. Therefore, in the electromagnetic induction heating device IH3, when the adjustment of the switching frequency of the inverter circuit is delayed with respect to the fluctuation of the resonance frequency, when the pan is moved away from the top plate, the resonance frequency and the switching frequency are close to each other, and the inverter circuit There is a possibility that an excessive power is applied, or that the switching phase becomes higher than the resonance frequency, leading to an advanced phase state, and the element may fail due to hard switching.

  FIG. 23 shows operation waveforms when the switching element Q3 is turned on / off.

  The operations of the inductance calculation unit Lr_ca3 and the resonance frequency calculation unit Fr_ca3 will be described with reference to FIG.

  In the state of FIG. 23, the switching element Q3 is turned on for ΔtQ3on, the voltage V is applied to the heating coil Lr3 for the time ΔtQ3on, and the current ILr3 flowing through the heating coil Lr3 is increased by ΔILr3. At this time, the inductance value Lr3 of the heating coil Lr3 is expressed by Expression (12) using the voltage VLr3 applied to the heating coil Lr3, the increase ΔILr3 of the current ILr3 flowing through the heating coil Lr3, and the on-time ΔtQ3on of the switching element Q3. The

Lr3 = VLr3 · (ΔtQ3on / ΔILr3) (12)
Based on the equation (12), the inductance calculation unit L_ca3 calculates the inductance value in the actual operation state of the circuit.

  Next, the operation of the resonance frequency calculation unit Fr_ca3 will be described.

  The resonance frequency fr3 in the actual operation state of the circuit is expressed by Expression (13) using the inductance Lr3 and the capacitance value Cr3 of the resonance capacitor.

fr3 = 1 / (2π (Lr3 · Cr3) ^1/2 ) (13)
The resonance frequency fr3 in the actual operation state of the circuit calculated by the resonance frequency calculation unit Fr_ca3 is output to the lower limit frequency setting unit Fr_lim3. In the lower limit frequency setting unit Fr_lim3, a margin is set in order to avoid the switching frequency fsw3 of the inverter circuit Inv3 and the resonance frequency fr3 from being close to each other. The lower limit frequency setting unit Fr_lim3 sets a lower limit value of the switching frequency for driving the inverter circuit Inv3, and the drive signal generation unit Driver3 drives the inverter circuit Inv3 based on the lower limit value of the switching frequency set by the lower limit frequency setting unit Fr_lim3. A signal (VGEQ3 in FIG. 23) is generated.

  As described above, in the electromagnetic induction heating device IH3 of the fifth embodiment, the inductance value in the actual operation state of the circuit is calculated, and the switching frequency fsw3 of the inverter circuit Inv3 and the resonance frequency fr3 are avoided from being close to each other. Thus, it is possible to improve the thermal power when the pot is floated and to suppress the application of excessive power when the pot is floated. In addition, since the number of switching elements in the inverter circuit is reduced, power loss and cost can be reduced.

  FIG. 24 is a basic configuration diagram of an electromagnetic induction heating device IH4 that is Embodiment 6 of the present invention.

  In the sixth embodiment, unlike the first to fifth embodiments, the power command value setting unit changes the input power command value to the inverter circuit that is output to the drive signal generation unit, according to the determination result of the pot floating determination unit. To do. Other configurations are the same as those of the first embodiment.

  25 and 26 show the relationship between the input power to the inverter circuit and the switching frequency of the inverter circuit when the pan moves away from the top plate in the electromagnetic induction heating device IH4 shown in FIG.

  In the sixth embodiment, when the pot floating is detected, the command value of the output power of the inverter is changed from the power command value P1 before the pot floating is detected, that is, when the pot is placed on the top plate. The electric power command value P2 after detection is changed to P2 (≠ P1). As shown in FIGS. 25 and 26, the power command value P <b> 1 before detecting the pot floating is set to a value larger than the power command value P <b> 2 after detecting the pot floating, so that the pot is being cooked in the pot shake. It becomes possible to increase the firepower. Moreover, although not shown in figure, the electric power command value P1 before detecting a pan float is made into a small value compared with the electric power command value P2 after detecting a pan float, and the thermal power to a pan is finely adjusted. Therefore, it is possible to prevent excessive heat from entering the pan even though the pan is shaken or the pan is shifted. Such power control can also be applied to the fifth embodiment (FIGS. 19 to 23) using a parallel resonant circuit.

  FIG. 27 is a flowchart illustrating a flow of power control processing executed by the electromagnetic induction heating device according to the sixth embodiment.

  In step 1, the control unit Co4 reads the power command value input from the operation unit.

  In Step 2, the control unit Co4 outputs a drive signal from the drive signal generation unit to the inverter circuit based on the read power command value, and starts heating the pot.

  Next, in step 3, the control unit Co4 determines whether or not the pot is lifted by the pot floating determination unit. When it determines with the pan not floating (No of step 3), control part Co4 performs the process after step 1 again. When it determines with the pan | floating being floated (Yes of step 3), control part Co4 performs the process of step 4. FIG.

  In step 4, the control unit Co4 reads the command value of the input power to the inverter circuit Inv4 again when the pan is floating. For this, an electric power command value when the pan is lifted may be input from the operation unit, the value may be read, or a heating pattern may be set in advance.

  Next, in step 5, the control unit Co4 calculates an inductance value in the actual operation state of the heating coil based on the circuit operation state of the inverter circuit Inv4 by the inductance calculation unit L_ca4.

  Next, in step 6, the control unit Co4 calculates the resonance frequency in the actual operation state of the circuit by the resonance frequency calculation unit Fr_ca4 based on the calculation result of the inductance calculation unit L_ca4.

  Next, in step 7, the control unit Co4 sets the lower limit value of the switching frequency of the inverter circuit Inv4 by the lower limit frequency setting unit Fr_lim4 based on the calculation result of the resonance frequency calculation unit Fr_ca4.

  Next, in step 8, the control unit Co4 generates a drive signal by the drive signal generation unit Driver4 and drives the inverter circuit Inv4 within the frequency range set by the lower limit frequency setting unit Fr_lim4.

  Note that after executing the process of step 8, the process of the control unit Co4 returns to START (RETURN).

  As described above, in the electromagnetic induction heating device IH4 of the sixth embodiment, when the pot floating is detected, the command value of the output power of the inverter is changed from the power command value P1 before the pot floating is detected. It changes to electric power command value P2 (≠ P1) after detection. This makes it possible to finely adjust the heating power when the pot is lifted.

  FIG. 28 is a basic configuration diagram of an electromagnetic induction heating device IH5 that is Embodiment 7 of the present invention. In the seventh embodiment, unlike the first to sixth embodiments, a pot-shaking cooking determination unit that determines whether or not the pot-shaking cooking is performed from the determination result of the pot floating determination unit is provided. In other words, in this embodiment, when the pan is lifted from the top plate, it is determined whether it is pan-shaking cooking or pan-floating cooking, and the input power command value to the inverter circuit is changed according to each cooking method. The Other configurations are the same as those of the first embodiment.

  Here, the case where it is determined that the pot shake cooking is performed by the pot shake cooking determination unit is referred to as pot shake cooking. Moreover, the case where it is determined that the pot-shaking cooking determination unit is not the pot-shaking cooking is referred to as pot-shifting cooking.

  29 and 30 show the relationship between the input power to the inverter circuit and the switching frequency of the inverter circuit in the electromagnetic induction heating device IH5 shown in FIG.

  As shown in FIGS. 29 and 30, the control unit Co5 controls the input power to the inverter to be P4 (≠ P1) when the pan deviates from the top plate. Moreover, control part Co5 is controlled so that the input electric power to an inverter may be set to P3 (≠ P1, P4), when it determines with a pot shake cooking determination part in a pot shake cooking determination part. By changing the input power to the inverter during cooking in the pot and cooking in the pan, it is possible to output the optimum heating power for each cooking method to the pan. Here, the magnitude relationship between P1, P3, and P4 is not limited to the magnitude relationship shown (P1> P3> P4), and is appropriately set according to the cooking method. Such power control can also be applied to the fifth embodiment (FIGS. 19 to 23) using a parallel resonant circuit.

  FIG. 31 is a flowchart showing a flow of power control processing executed by the electromagnetic induction heating device of the seventh embodiment.

  In step 1, the control unit Co5 reads the power command value input from the operation unit.

  In step 2, the control unit Co5 outputs a drive signal from the drive signal generation unit to the inverter circuit based on the read power command value, and starts heating the pan.

  Next, in Step 3, the control unit Co5 determines whether or not the pot is lifted by the pot floating determination unit. When it determines with the pan not floating (No of step 3), control part Co4 performs the process after step 1 again. When it is determined that the pan is floating (Yes in Step 3), the control unit Co5 executes the process in Step 4.

  In step 4, the control unit Co5 determines whether the pot shake cooking is being performed in the pot shake cooking determination unit. In step 3, when it is determined that the pan is floating and when it is determined that the pan is not floating, the pan shake cooking is performed when the pan is alternately repeated periodically. Determined. When it is determined in step 4 that the cooking is pot cooking (Yes in step 4), the control unit Co5 next executes the process of step 5. Moreover, when it determines with it not being pan cooking (No of step 4), control part Co5 performs the process of step 6 next.

  In Step 5, the control unit Co5 uses the power command value setting unit to read the power command value at the time of cooking the pot. Moreover, in step 6, the control part Co5 reads the electric power command value at the time of pan shifting cooking using an electric power command value setting part. At this time, a power command value input from the operation unit may be read, or a heating pattern may be set in advance. After step 5 or step 6, the control unit Co5 executes the process of step 7.

  In step 7, the control unit Co5 calculates the inductance value in the actual operating state of the heating coil based on the circuit operating state of the inverter circuit Inv5 by the inductance calculating unit L_ca5.

  Next, in step 8, the control unit Co5 calculates the resonance frequency in the actual operation state of the circuit by the resonance frequency calculation unit Fr_ca5 based on the calculation result of the inductance calculation unit L_ca5.

  Next, in step 9, the control unit Co5 sets the lower limit value of the switching frequency of the inverter circuit by the lower limit frequency setting unit Fr_lim5 based on the calculation result of the resonance frequency calculation unit Fr_ca5.

  Next, in step 10, the control unit Co5 generates a drive signal by the drive signal generation unit Driver5 and drives the inverter circuit in the frequency range set by the lower limit frequency setting unit Fr_lim5.

  After executing the process of step 10, the process of the control unit Co5 returns to START (RETURN).

  As described above, in the electromagnetic induction heating device IH5 of the seventh embodiment, when the pot floating is detected, it is determined whether it is pot-shaking cooking or pot-shifting cooking, and according to each cooking method. The input power command value to the inverter circuit is changed. Thereby, it becomes possible to output optimal thermal power to a pan according to each cooking method.

  In addition, this invention is not limited to embodiment mentioned above, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  For example, the switching element is not limited to an n-channel IGBT, and a p-channel IGBT, the above-described MOSFET, a junction bipolar transistor, or the like can be used.

  Moreover, as a to-be-heated body, other cooking appliances, such as not only a pan but a frying pan, are applicable.

IH0, IH1, IH2, IH3, IH4, IH5 ... Electromagnetic induction heating devices Res0, Res1, Res2, Res3, Res4, Res5 ... Resonant circuits Lr0, Lr1, Lr2, Lr3, Lr4, Lr5 ... Heating coils Cr0, Cr1, Cr2, Cr3, Cr4, Cr5 ... Resonant coils Inv0, Inv1, Inv2, Inv3, Inv4, Inv5 ... Inverter circuits Co0, Co1, Co2, Co3, Co4, Co5 ... Control units Phs1, Phs2 ... Phase difference detectors AC0, AC1, AC2, AC3, AC4, AC5 ... AC power supplies Vs1, Vs2, Vs3 ... Voltage detection units Cs1, Cs2, Cs3 ... Current detection units ACDC1, ACDC2, ACDC3 ... AC / DC conversion circuits Q11, Q12, Q13, Q14, Q21, Q22, Q3 … Switchon Elements D11, D12, D13, D14, D21, D22, D3 ... diodes

Claims (13)

A heating coil for heating an object to be heated on the top plate;
A resonant circuit having the heating coil and a resonant capacitor;
An inverter circuit that outputs power to the resonant circuit;
A control unit for controlling input power to the inverter circuit;
In an electromagnetic induction heating device having
The control unit, when the heated object floats from the top plate, makes the switching frequency of the inverter circuit lower than the switching frequency before the heated object floats from the top plate. Electromagnetic induction heating device. In the electromagnetic induction heating device according to claim 1,
The said control part has a resonance frequency calculating part which calculates the resonance frequency of the said resonance circuit, The electromagnetic induction heating apparatus characterized by the above-mentioned. The electromagnetic induction heating device according to claim 2,
The said control part has a switching frequency lower limit value calculating part which calculates the lower limit of the switching frequency of the said inverter circuit based on the resonance frequency calculated by the said resonance frequency calculating part, The electromagnetic induction heating apparatus characterized by the above-mentioned. The electromagnetic induction heating device according to claim 2,
The resonance frequency calculation unit includes an input power to the inverter circuit, a current flowing through the heating coil, a switching frequency of the inverter circuit, a phase difference between a current flowing through the heating coil and an output voltage of the inverter circuit. An electromagnetic induction heating device that calculates a resonance frequency based on a capacitance value of the resonance capacitor. The electromagnetic induction heating device according to claim 2,
The resonance frequency calculation unit includes a switching frequency of the inverter circuit, a voltage applied to the heating coil, a current flowing through the heating coil, a voltage applied to the heating coil, and a current flowing through the heating coil. An electromagnetic induction heating device that calculates a resonance frequency based on a phase difference and a capacitance value of the resonance capacitor. The electromagnetic induction heating device according to claim 2,
The resonance frequency calculation unit calculates a resonance frequency based on a voltage applied to the heating coil, a time during which a voltage is applied to the heating coil, and a current flowing through the heating coil. Electromagnetic induction heating device. In the electromagnetic induction heating device according to claim 1,
In the control unit, the electromagnetic induction heating is characterized in that the input power command value of the inverter circuit is different between the case where the object to be heated is placed on a top plate and the case where the object to be heated floats. apparatus. In the electromagnetic induction heating device according to claim 1,
The said control part has a pot shake cooking determination part which determines whether it is pot shake cooking, The electromagnetic induction heating apparatus characterized by the above-mentioned. The electromagnetic induction heating device according to claim 8,
In the control unit, when the heated object floats from the top plate, when the pot shake cooking determination unit determines that the pot shake cooking is performed, and when the pot shake cooking determination unit is not the pot shake cooking The electromagnetic induction heating device characterized in that the input power command value to the inverter circuit differs depending on the case. The electromagnetic induction heating device according to claim 9,
The controller is configured to place the heated object on the top plate when the pan shake cooking determination unit determines that the pot shake cooking is performed, and when the pan shake cooking determination unit determines that the pot shake cooking is not pan shake cooking. The electromagnetic induction heating device is characterized in that the input power command value to the inverter circuit is different depending on the case. In the electromagnetic induction heating device according to claim 1,
The said inverter circuit is comprised from a single phase bridge circuit, The electromagnetic induction heating apparatus characterized by the above-mentioned. In the electromagnetic induction heating device according to claim 1,
The said inverter circuit is comprised from a half-bridge circuit, The electromagnetic induction heating apparatus characterized by the above-mentioned. In the electromagnetic induction heating device according to claim 1,
The inverter circuit includes a switching element,
The resonant circuit is composed of a parallel circuit of the heating coil and the resonant capacitor,
The electromagnetic induction heating device, wherein the switching element and the parallel circuit are connected in series.

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