Induction heating cooker, control device for induction heating cooker, and control method for induction heating cooker

Abstract

The present invention provides an induction cooker capable of suppressing interference noise, a control device for the induction cooker, and a control method for the induction cooker. [Solution] The induction heating cooker comprises a first heating coil that heats the central region of the bottom surface of a heating container, a second heating coil arranged concentrically with the first heating coil and heating the outer peripheral region of the central region of the heating container, a first inverter circuit that supplies a high-frequency current to the first heating coil, a second inverter circuit that supplies a high-frequency current to the second heating coil, and a control unit that controls the first inverter circuit and the second inverter circuit. When the control unit supplies a high-frequency current to the first heating coil and the second heating coil, it causes the first inverter circuit and the second inverter circuit to operate at substantially the same operating frequency.

Description

Technical Field

[0001] The present disclosure relates to an induction heating cooker, a control device for an induction heating cooker, and a control method for an induction heating cooker.

Background Art

[0002] Patent Document 1 discloses an electric rice cooker that drives a plurality of heating coils simultaneously.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides an induction heating cooker, a control device for an induction heating cooker, and a control method for an induction heating cooker that can suppress interference noise.

Means for Solving the Problems

[0005] The induction heating cooker in the present disclosure includes a first heating coil that heats a central region of the bottom surface of a heating container, a second heating coil that is arranged concentrically with the first heating coil and heats an outer peripheral region of the central region of the heating container, a first inverter circuit that supplies a high-frequency current to the first heating coil, a second inverter circuit that supplies a high-frequency current to the second heating coil, and a control unit that controls the first inverter circuit and the second inverter circuit. When supplying a high-frequency current to the first heating coil and the second heating coil, the control unit operates the first inverter circuit and the second inverter circuit at substantially the same operating frequency.

[0006] Furthermore, the control device for an induction cooker in this disclosure is a control device for an induction cooker having a first heating coil that heats the central region of the bottom surface of a heating container, a second heating coil that is arranged concentrically with the first heating coil and heats the outer peripheral region of the central region of the heating container, a first inverter circuit that supplies a high-frequency current to the first heating coil, and a second inverter circuit that supplies a high-frequency current to the second heating coil, wherein the control device operates the first inverter circuit and the second inverter circuit at substantially the same operating frequency when supplying a high-frequency current to the first heating coil and the second heating coil.

[0007] Furthermore, the induction heating cooker control method in this disclosure is a control method for an induction heating cooker having a first heating coil that heats the central region of the bottom surface of a heating container, a second heating coil arranged concentrically with the first heating coil and heating the outer peripheral region of the central region of the heating container, a first inverter circuit that supplies a high-frequency current to the first heating coil, and a second inverter circuit that supplies a high-frequency current to the second heating coil, wherein when supplying a high-frequency current to the first heating coil and the second heating coil, the first inverter circuit and the second inverter circuit are operated at substantially the same operating frequency. [Effects of the Invention]

[0008] The induction cooker, the control circuit for the induction cooker, the control device for the induction cooker, and the control method for the induction cooker in this disclosure operate the first inverter circuit and the second inverter circuit at substantially the same operating frequency when supplying a high-frequency current to the first heating coil and the second heating coil. Therefore, interference noise can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows the position of the heating coil in the rice cooker of this embodiment. [Figure 2] Circuit diagram showing the control circuit in the rice cooker of this embodiment. [Figure 3] This figure shows the configuration of the control unit in the rice cooker of this embodiment. [Figure 4] Timing chart showing the operation of the first inverter circuit in the rice cooker of this embodiment. [Figure 5] This figure shows the first to third states of the first inverter circuit in the rice cooker of this embodiment. [Figure 6] This figure shows the fourth to sixth states of the first inverter circuit in the rice cooker of this embodiment. [Figure 7] Timing chart showing an example of the processing of the phase control unit in the rice cooker of this embodiment. [Figure 8] A graph showing an example of the processing of the frequency setting unit in the rice cooker of this embodiment. [Figure 9] This diagram shows the arrangement of the first current path to the fourth current path in the rice cooker of this embodiment. [Figure 10] A flowchart showing an example of the process for determining whether a pot is present or not in the rice cooker of this embodiment. [Modes for carrying out the invention]

[0010] (Knowledge and other information that formed the basis of this disclosure) At the time the inventors conceived of this disclosure, for example, an electric rice cooker that simultaneously drives multiple heating coils was disclosed, as described in Patent Document 1. The multiple heating coils included, for example, an inner coil positioned opposite the bottom of the pot and an outer coil positioned opposite the bottom side of the pot. However, the inventors discovered that when multiple heating coils are driven simultaneously, interference noise occurs if the driving frequencies of the multiple heating coils are different from each other. To solve this problem, the subject matter of this disclosure was established. Therefore, this disclosure provides an induction cooker capable of suppressing interference noise, a control circuit for the induction cooker, a control device for the induction cooker, and a method for controlling the induction cooker.

[0011] Hereinafter, embodiments will be described in detail with reference to the drawings. However, there may be cases where explanations that are more detailed than necessary are omitted. For example, there may be cases where details of well-known matters are omitted, or duplicate explanations for substantially the same configurations are omitted. Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] [1. Configuration] [1-1. Configuration of the rice cooker] FIG. 1 is a diagram showing the position of the heating coil in the rice cooker 100 of the present embodiment. In FIG. 1, the X-axis, Y-axis, and Z-axis are shown. The X-axis, Y-axis, and Z-axis are perpendicular to each other. The X-axis and Y-axis are parallel to the horizontal direction. The Z-axis is parallel to the vertical direction. The X-axis indicates the left-right direction. The Y-axis indicates the front-back direction. The positive direction of the X-axis indicates the right direction. The positive direction of the Y-axis indicates the front direction. The positive direction of the Z-axis indicates the upward direction. The rice cooker 100 corresponds to an example of an "induction cooker".

[0013] In the upper part of FIG. 1, a side sectional view of the rice cooker 100 is shown. The rice cooker 100 includes a pot PT, a first heating coil 11, and a second heating coil 12. The pot PT is formed in a bottomed cylindrical shape. The pot PT is made of a conductive material such as iron or copper. The pot PT corresponds to an example of a "heating container".

[0014] The first heating coil 11 is arranged to face the bottom of the pot PT. The first heating coil 11 is formed in a hollow disk shape and is arranged substantially parallel to the X-Y plane. The bottom of the pot PT corresponds to an example of a "central region of the bottom surface". The first heating coil 11 is arranged such that the central axis CL extending in the vertical direction of the pot PT passes through the center C1 of the first heating coil 11. The first heating coil 11 inductively heats the bottom of the pot PT.

[0015] The second heating coil 12 is positioned opposite the bottom side of the pot PT. The second heating coil 12 is formed in a cylindrical shape with a diameter that increases upwards, so as to follow the bottom side of the pot PT. The bottom portion corresponds to an example of the "outer periphery of the central region." The second heating coil 12 is positioned such that the central axis CL extending vertically from the pot PT passes through the center C2 of the second heating coil 12. The center C2 is located at the vertical center of the second heating coil 12 and is situated at the intersection of the central line CL2 extending horizontally and the central axis CL. The second heating coil 12 induces heating of the bottom side of the pot PT.

[0016] The lower part of Figure 1 shows plan views of the first heating coil 11 and the second heating coil 12. As shown in the lower part of Figure 1, the second heating coil 12 is positioned concentrically with the first heating coil 11.

[0017] [1-2. Configuration for driving and controlling the inverter circuit] Figure 2 is a circuit diagram showing the inverter circuit 2 in the rice cooker 100 of this embodiment. The inverter circuit 2 includes a first inverter circuit 21 and a second inverter circuit 22. The first inverter circuit 21 supplies high-frequency current to the first heating coil 11. The second inverter circuit 22 supplies high-frequency current to the second heating coil 12.

[0018] Next, with reference to Figure 2, the configuration for driving the inverter circuit 2 will be described. The first inverter circuit 21 receives AC power supplied from the commercial power supply, which is full-wave rectified by a diode bridge DB and then smoothed by a smoothing circuit consisting of a first smoothing coil L1 and a first smoothing capacitor C12. In other words, the smoothing circuit reduces the high-frequency ripple supplied to the inverter circuit 2. The smoothing circuit consists, for example, a smoothing capacitor of a few μF and a smoothing coil of several hundred μH. The first smoothing capacitor C12 corresponds to an example of a "smoothing capacitor".

[0019] The second inverter circuit 22 receives AC power supplied from the commercial power supply, which is full-wave rectified by a diode bridge DB and then smoothed by a smoothing circuit consisting of a second smoothing coil L2 and a second smoothing capacitor C22. The second smoothing capacitor C22 corresponds to an example of a "smoothing capacitor".

[0020] In this embodiment, the commercial power supply provides, for example, single-phase 200V AC power to the diode bridge DB. The voltage supplied by the commercial power supply to the diode bridge DB may be 220V, 230V, or 240V. Alternatively, the commercial power supply may be a three-phase AC power supply. In this case, it is preferable that the diode bridge DB be a diode bridge compatible with the three-phase AC power supply.

[0021] The first inverter circuit 21 and the second inverter circuit 22 are driven by the inverter drive circuit 3. The inverter drive circuit 3 is controlled by the control unit 4. Furthermore, the control unit 4 corresponds to an example of a "control device".

[0022] The control unit 4 is, for example, a so-called microcomputer. Furthermore, the control unit 4 consists of a microcomputer and peripheral circuits. In other words, a control unit 4, which consists of a single microcomputer, drives the first inverter circuit 21 and the second inverter circuit 22 via the inverter drive circuit 3.

[0023] [1-3. Inverter Circuit Configuration] Next, the configurations of the first inverter circuit 21 and the second inverter circuit 22 will be described with reference to Figure 2.

[0024] The first inverter circuit 21 includes a first main switching element SM1, a first resonant capacitor C11, and a first series circuit SC1. The first main switching element SM1 is connected in series with the first heating coil 11. The first resonant capacitor C11 is connected in parallel with the first heating coil 11. The first series circuit SC1 is connected in parallel with the first resonant capacitor C11. The first series circuit SC1 is configured by connecting the first auxiliary switching element SS1 and the first auxiliary capacitor C13 in series.

[0025] The first resonant capacitor C11 resonates with the first heating coil 11. The first series circuit SC1 clamps the resonant voltage when the first main switching element SM1 is conducting by charging and discharging the first auxiliary capacitor C13. The first main switching element SM1 and the first auxiliary switching element SS1 are alternately connected by the inverter drive circuit 3.

[0026] The second inverter circuit 22 includes a second main switching element SM2, a second resonant capacitor C21, and a second series circuit SC2. The second main switching element SM2 is connected in series with the second heating coil 12. The second resonant capacitor C21 is connected in parallel with the second heating coil 12. The second series circuit SC2 is connected in parallel with the second resonant capacitor C21. The second series circuit SC2 is constructed by connecting the second auxiliary switching element SS2 and the second auxiliary capacitor C23 in series.

[0027] The second resonant capacitor C21 resonates with the second heating coil 12. The second series circuit SC2 clamps the resonant voltage when the second main switching element SM2 is conducting by charging and discharging the second auxiliary capacitor C23. The second main switching element SM2 and the second auxiliary switching element SS2 are alternately connected by the inverter drive circuit 3.

[0028] The first main switching element SM1 consists of a first main IGBT (Insulated Gate Bipolar Transistor) TM1 and a first main reverse-connected diode DM1. For convenience, in the following explanation, "IGBT" will be simply referred to as "transistor". In other words, the first main switching element SM1 is composed of a first main transistor TM1 and a first main reverse-connected diode DM1. The first auxiliary switching element SS1 consists of a first auxiliary transistor TS1 and a first auxiliary reverse-connected diode DS1. The first auxiliary transistor TS1 is composed of an IGBT.

[0029] The second main switching element SM2 consists of a second main transistor TM2 and a first main reverse-connected diode DM2. The second main transistor TM2 is composed of an IGBT. The second auxiliary switching element SS2 consists of a second auxiliary transistor TS2 and a second auxiliary reverse-connected diode DS2. The second auxiliary transistor TS2 is composed of an IGBT.

[0030] The inverter drive circuit 3 outputs a PWM (Pulse Width Modulation) signal to the first main transistor TM1 and the second main transistor TM2, in which the duty cycle changes periodically during the conduction period. The frequency of the PWM output by the inverter drive circuit 3 is, for example, 23 kHz. The frequency of the PWM signal is set by the frequency setting unit 414 of the control unit 4, which will be explained later. The inverter drive circuit 3 also operates in response to the PWM signal from the control unit 4.

[0031] The first current sensor SA1 is positioned between the negative terminal of the diode bridge DB and the negative terminal of the first smoothing capacitor C12, or the emitter terminal of the first main transistor TM1. The first current sensor SA1 detects the first current value J1 input to the first inverter circuit 21.

[0032] The second current sensor SA2 is positioned between the negative terminal of the diode bridge DB and the negative terminal of the second smoothing capacitor C22, or the emitter terminal of the second main transistor TM2. The second current sensor SA2 detects the second current value J2 input to the second inverter circuit 22.

[0033] The voltage sensor SV is positioned between the positive terminal and the negative terminal of the diode bridge DB. The voltage sensor SV detects the voltage value V applied to the first inverter circuit 21 and the second inverter circuit 22.

[0034] The operation of the first inverter circuit 21 and the second inverter circuit 22 will be further explained with reference to Figure 4.

[0035] [1-4. Configuration of the Control Unit] Next, the configuration of the control unit 4 will be described with reference to Figure 3. Figure 3 is a diagram showing the configuration of the control unit 4 in the rice cooker 100 of this embodiment. As shown in Figure 3, the control unit 4 comprises a processor 41 and a memory 42.

[0036] The processor 41 consists of a CPU (Central Processing Unit), an MPC (Micro Processing Unit), and the like. The memory 42 consists of ROM (Read Only Memory) and the like.

[0037] The processor 41 may consist of multiple processors or a single processor. The processor 41 may be hardware programmed to implement the functions of each part described later. That is, the processor 41 may be configured to incorporate the control program 421 as a hardware circuit. In this case, for example, the processor 41 may be composed of an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), etc. The following description explains the case in which the processor 41 realizes various functions of the control unit 4 by executing the control program 421.

[0038] Memory 42 has a storage area for storing programs executed by the processor 41 and data processed by the processor 41. Memory 42 stores control programs 421 and the like executed by the processor 41. Memory 42 has a non-volatile storage area for storing programs and data non-volatilely. Memory 42 may include, for example, ROM, HDD (Hard Disk Drive), SSD (Solid State Drive), etc., as the non-volatile storage area. Alternatively, memory 42 may include a volatile storage area and constitute a work area for temporarily storing programs executed by the processor 41 and data to be processed. Memory 42 may include, for example, RAM (Random Access Memory), etc., as the volatile storage area.

[0039] The control unit 4 includes a voltage acquisition unit 411, an on-time setting unit 412, a power consumption setting unit 413, a frequency setting unit 414, a phase control unit 415, a current acquisition unit 416, and a pot presence / absence detection unit 417. Specifically, the processor 41 functions as the voltage acquisition unit 411, the on-time setting unit 412, the power consumption setting unit 413, the frequency setting unit 414, the phase control unit 415, the current acquisition unit 416, and the pot presence / absence detection unit 417 by executing the control program 421.

[0040] The voltage acquisition unit 411 acquires a voltage value V from the voltage sensor SV. The voltage acquisition unit 411 also determines the power supply voltage VG based on the voltage value V. For example, the voltage acquisition unit 411 determines the power supply voltage VG by doubling the voltage value V. The power supply voltage VG is, for example, 200V. The power supply voltage VG may also be 220V, 230V, or 240V.

[0041] The on-time setting unit 412 sets the upper limit value TX1 for the on-time of the first main transistor TM1 and the upper limit value TX2 for the on-time of the second main transistor TM2 according to the power supply voltage VG.

[0042] The ON-time setting unit 412 sets the upper limit TX1 and upper limit TX2 to 25 μsec when the power supply voltage VG is, for example, 200 V. The ON-time setting unit 412 sets the upper limit TX1 and upper limit TX2 to 23 μsec when the power supply voltage VG is, for example, 220 V. The ON-time setting unit 412 sets the upper limit TX1 and upper limit TX2 to 21 μsec when the power supply voltage VG is, for example, 250 V.

[0043] Furthermore, when the rice cooker 100 starts cooking rice, the ON time setting unit 412 sets the upper limit value TX1 of the ON time of the first main transistor TM1 and the upper limit value TX2 of the ON time of the second main transistor TM2 to the inverter drive circuit 3. The inverter drive circuit 3 controls the on-time of the first main transistor TM1 so that it is less than or equal to the upper limit value TX1, and controls the on-time of the second main transistor TM2 so that it is less than or equal to the upper limit value TX2.

[0044] The power consumption setting unit 413 controls the current values ​​of the first inverter circuit 21 and the second inverter circuit 22 so that the sum WS of the power consumption W1 of the first heating coil 11 and the power consumption W2 of the second heating coil 12 becomes a predetermined value WT, according to the power supply voltage VG. However, the timing at which the power consumption W1 of the first heating coil 11 reaches its maximum power is different from the timing at which the power consumption W2 of the second heating coil 12 reaches its maximum power. Therefore, the power consumption setting unit 413 controls the current values ​​of the first inverter circuit 21 and the second inverter circuit 22, for example, so that the sum of the maximum power value of the power consumption W1 of the first heating coil 11 and the maximum power value of the power consumption W2 of the second heating coil 12 becomes a predetermined maximum value. The power consumption setting unit 413, for example, causes the inverter drive circuit 3 to control the current values ​​of the first inverter circuit 21 and the second inverter circuit 22 so that the sum WS of the power consumption W1 of the first heating coil 11 and the power consumption W2 of the second heating coil 12 becomes a predetermined value WT.

[0045] The specified value WT is, for example, "1000W". When the power supply voltage VG is 200V, the inverter drive circuit 3 controls the current values ​​of the first inverter circuit 21 and the second inverter circuit 22 so that the sum AS of the current value A1 flowing through the first heating coil 11 and the current value A2 flowing through the second heating coil 12 is 5A.

[0046] When the power supply voltage VG is 220V, the inverter drive circuit 3 controls the current values ​​of the first inverter circuit 21 and the second inverter circuit 22 so that the sum AS of the current value A1 flowing through the first heating coil 11 and the current value A2 flowing through the second heating coil 12 is "4.55A (=1000 / 220)". Furthermore, the inverter drive circuit 3 may, for example, set the current value A1 of the current flowing through the first heating coil 11 and the current value A2 of the current flowing through the second heating coil 12, and control the current values ​​of the first inverter circuit 21 and the second inverter circuit 22.

[0047] When the power supply voltage VG is 240V, the inverter drive circuit 3 controls the current values ​​of the first inverter circuit 21 and the second inverter circuit 22 so that the sum AS of the current value A1 flowing through the first heating coil 11 and the current value A2 flowing through the second heating coil 12 is "4.17A (=1000 / 240)".

[0048] When the frequency setting unit 414 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it causes the first inverter circuit 21 and the second inverter circuit 22 to operate at approximately the same operating frequency F. When the frequency setting unit 414 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it, for example, causes the inverter drive circuit 3 to operate the first inverter circuit 21 and the second inverter circuit 22 at approximately the same operating frequency F. The frequency setting unit 414 sets the operating frequency F based on, for example, the frequency of the CPU's internal clock circuit, or a frequency obtained by multiplying or dividing the frequency of an external clock circuit.

[0049] The inverter drive circuit 3 drives the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 at, for example, "23kHz". The difference ΔF between the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 is, for example, 100 Hz or less. Preferably, the difference ΔF between the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 is, for example, 50 Hz or less. More preferably, the difference ΔF between the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 is, for example, 20 Hz or less.

[0050] The difference ΔF between the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 corresponds to the frequency of the interference sound between the first inverter circuit 21 and the second inverter circuit 22. Therefore, if the difference ΔF between the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 is 20 Hz or less, the frequency of the interference sound will also be 20 Hz or less, and thus it will not be perceptible to the human ear. In other words, humans cannot hear the interference sound. Furthermore, while 50Hz and 100Hz are within the human audible range, if the interfering sound is not continuous but instantaneous, humans will have difficulty perceiving it.

[0051] Furthermore, when the frequency setting unit 414 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it may operate the first heating coil 11 at approximately the same operating frequency F and periodically change the operating frequency F at approximately the same timing. When the frequency setting unit 414 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it may, for example, operate the first inverter circuit 21 and the second inverter circuit 22 with respect to the inverter drive circuit 3 at approximately the same operating frequency F, and periodically change the operating frequency F at approximately the same timing. For example, the inverter drive circuit 3 may periodically change the operating frequency F of the first inverter circuit 21 and the second inverter circuit 22 at the same timing within the range of "22.25 kHz" or higher and "24.25 kHz". This case will be further explained with reference to Figure 8.

[0052] When the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it shifts the ON timing of the second main transistor TM2 by a predetermined time ΔP relative to the ON timing of the first main transistor TM1. When the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it controls the inverter drive circuit 3, for example, so that the timing of the second main transistor TM2 turning on is shifted by a predetermined time ΔP compared to the timing of the first main transistor TM1 turning on.

[0053] When the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it may shift the timing of the second main transistor TM2 off by a predetermined time ΔP relative to the timing of the first main transistor TM1 off. Furthermore, when the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it may, for example, instruct the inverter drive circuit 3 to control the timing of the off-time of the second main transistor TM2 to be shifted by a predetermined time ΔP compared to the timing of the off-time of the first main transistor TM1.

[0054] When the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 are both "23 kHz", then one period PD is "43 μsec (= 1000 / 23)". The predetermined time ΔP is, for example, less than half a period, i.e., half a period. The predetermined time ΔP is, for example, 1 / 20 of one period PD. This case will be further explained with reference to Figure 7.

[0055] Furthermore, when the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it may set the current flowing through the second heating coil 12 to be approximately in opposite phase to the current flowing through the first heating coil 11. In this case, when the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it controls the inverter drive circuit 3, for example, to make the current flowing through the second heating coil 12 approximately in opposite phase to the current flowing through the first heating coil 11.

[0056] In this case, the inverter drive circuit 3 controls the timing of the second main transistor TM2 to turn on by half a cycle compared to the timing of the first main transistor TM1 turning on.

[0057] When the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 are both "23 kHz", then one period PD is "43 μsec (= 1000 / 23)". Therefore, half a period is "approximately 21.5 μsec". In other words, the inverter drive circuit 3 controls the timing of the second main transistor TM2 to turn on by approximately 21.5 μsec compared to the timing of the first main transistor TM1 turning on.

[0058] Furthermore, when the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it may set the current flowing through the second heating coil 12 to be approximately in phase with the current flowing through the first heating coil 11. In this case, when the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it controls, for example, the inverter drive circuit 3 to make the current flowing through the second heating coil 12 substantially in phase with the current flowing through the first heating coil 11.

[0059] In this case, the inverter drive circuit 3 is controlled, for example, to match the ON timing of the second main transistor TM2 with the ON timing of the first main transistor TM1.

[0060] The current acquisition unit 416 acquires a first current value J1 from the first current sensor SA1 and a second current value J2 from the second current sensor SA2. The first current value J1 is the current value input to the first inverter circuit 21. The second current value J2 is the current value input to the second inverter circuit 22.

[0061] The pot presence / absence detection unit 417 detects the presence or absence of a pot PT based on at least one of the first current value J1 and the on-time TN1 of the first main transistor TM1, and the second current value J2 and the on-time TN2 of the second main transistor TM2. The pot presence / absence detection unit 417 obtains the on-time TN1 of the first main transistor TM1 and the on-time TN2 of the second main transistor TM2 from, for example, the inverter drive circuit 3. Here, the presence or absence of the pot PT indicates whether or not the pot PT is positioned in a predetermined location within the casing of the rice cooker 100.

[0062] The pot presence detection unit 417 detects the presence of a pot PT when, for example, the first current value J1 and the on-time TN1 of the first main transistor TM1 satisfy the following equation (1). TN1 × α - J1 ≤ TH1 (1) Here, the coefficient α is a preset constant. The threshold value TH1 is also preset according to the power supply voltage VG. The larger the power supply voltage VG, the smaller the threshold value TH1 is set to.

[0063] The pot presence detection unit 417 detects the presence of a pot PT when, for example, the second current value J2 and the on-time TN2 of the second main transistor TM2 satisfy the following equation (2). TN2 × β - J2 ≤ TH2 (1) Here, the coefficient β is a preset constant. The threshold value TH2 is also preset according to the power supply voltage VG. The larger the power supply voltage VG, the smaller the threshold value TH2 is set to.

[0064] The processing of the pot presence / absence detection unit 417 will be further explained with reference to Figure 10. The pot presence / absence detection unit 417 corresponds to an example of a "container presence / absence detection unit".

[0065] [2. Operation] [2-1. Operation of the Inverter Circuit] Next, the operation of the inverter circuit will be explained with reference to Figures 4-6. Figure 4 is a timing chart showing the operation of the first inverter circuit 21 in the rice cooker 100 of this embodiment.

[0066] The horizontal axis of Figure 4 represents time T. The vertical axis of Figure 4, from top to bottom, represents the following nine items: ON / OFF status of the first main transistor TM1, ON / OFF status of the first auxiliary transistor TS1, the sum of the collector current of the first main transistor TM1 and the current of the first main reverse diode DM1 (hereinafter referred to as current JA1 for convenience), the collector-emitter voltage VCM of the first main transistor TM1, the current J11 flowing through the first heating coil 11, the sum of the collector current of the first auxiliary transistor TS1 and the current of the first auxiliary reverse diode DS1 (hereinafter referred to as current JB1 for convenience), the collector-emitter voltage VCS of the first auxiliary transistor TS1, the current JC11 flowing through the first resonant capacitor C11, and the voltage VC13 of the first auxiliary capacitor C13.

[0067] The horizontal axis of Figure 4, time T, includes times T1, T2, T3, T4, T6, and T7. The period from time T1 to time T2 is denoted as the first period P1. The period from time T2 to time T3 is denoted as the second period P2. The period from time T3 to time T4 is denoted as the third period P3. The period from time T4 to time T5 is denoted as the fourth period P4. The period from time T5 to time T6 is denoted as the fifth period P5. The period from time T6 to time T7 is denoted as the sixth period P6.

[0068] Figure 5 shows the first state 501 to the third state 503 of the first inverter circuit 21 in the rice cooker 100 of this embodiment. In the first state 501, the direction of the current flowing through the first inverter circuit 21 during the first period P1 is indicated by a dashed arrow. In the second state 502, the direction of the current flowing through the first inverter circuit 21 during the second period P2 is indicated by a dashed arrow. In the third state 503, the direction of the current flowing through the first inverter circuit 21 during the third period P3 is indicated by a dashed arrow.

[0069] Figure 6 shows the fourth state 504 to the sixth state 506 of the first inverter circuit 21 in the rice cooker 100 of this embodiment. In the fourth state 504, the direction of the current flowing through the first inverter circuit 21 during the fourth period P4 is indicated by a dashed arrow. In the fifth state 505, the direction of the current flowing through the first inverter circuit 21 during the fifth period P5 is indicated by a dashed arrow. In the sixth state 506, the direction of the current flowing through the first inverter circuit 21 during the sixth period P6 is indicated by a dashed arrow.

[0070] The operation of the first inverter circuit 21 will be explained with reference to Figures 4-6. As shown in Figure 4, time T1 corresponds to the zero-crossing point of the collector current JA1 of the first main transistor TM1. Before time T1, the collector current JA1 of the first main transistor TM1 is negative, and as time T progresses, the collector current JA1 of the first main transistor TM1 increases and becomes "zero" at time T1.

[0071] At time T1, the first main transistor TM1 transitions from the OFF period to the ON period according to the instructions of the inverter drive circuit 3. The OFF period is the period during which the first main transistor TM1 is held in the OFF state, and the ON period is the period during which the first main transistor TM1 is periodically turned ON at a predetermined duty cycle.

[0072] During the first period P1, the first main transistor TM1 is held ON according to the instructions of the inverter drive circuit 3. Also during the first period P1, as shown in the first state 501 of Figure 5, current flows from the first smoothing capacitor C12, through the first heating coil 11 and the first main transistor TM1 in sequence, and back to the first smoothing capacitor C12.

[0073] As current flows in this manner, the collector current JA1 of the first main transistor TM1 increases with a slope corresponding to the quotient obtained by dividing the voltage value of the first smoothing capacitor C12 by the inductance value of the first heating coil 11. Then, at time T2, the first main transistor TM1 transitions from the ON period to the OFF period according to the instructions of the inverter drive circuit 3.

[0074] During the second period P2, the first main transistor TM1 and the first auxiliary transistor TS1 are held in the OFF state. During the second period P2, as shown in the second state 502 of Figure 5, current flows in the parallel circuit of the first heating coil 11 and the first resonant capacitor C11. That is, the first heating coil 11 and the first resonant capacitor C11 resonate. Therefore, as shown in Figure 4, the current JC11 flowing through the first resonant capacitor C11 becomes large during the second period P2.

[0075] Furthermore, during the second period P2, the current flowing through the first heating coil 11 flows into the first resonant capacitor C11 and is stored in the first resonant capacitor C11, causing the terminal voltage of the first resonant capacitor C11 to increase. As a result, the collector-emitter voltage VCM of the first main transistor TM1 increases. Conversely, the collector-emitter voltage VCS of the first auxiliary transistor TS1 decreases.

[0076] At time T3, the collector-emitter voltage VCS of the first auxiliary transistor TS1 reaches zero volts. At this point, the first auxiliary reverse-connected diode DS1 becomes conductive. During the third period P3, as shown in the third state 503 of Figure 5, current flows from the first auxiliary capacitor C13, through the first heating coil 11 and the first auxiliary reverse-connected diode DS1 in sequence, and back to the first auxiliary capacitor C13. In other words, the first auxiliary capacitor C13 is charged by the current flowing through the first heating coil 11.

[0077] Furthermore, during the third period P3, the collector-emitter voltage VCS of the first auxiliary transistor TS1 is maintained at zero volts. The current J11 flowing through the first heating coil 11 decreases. The current JB1, which is the current flowing through the first auxiliary reverse diode DS1, increases from a negative value to a positive value. Also, since the first auxiliary capacitor C13 is charged, the voltage VC13 across the first auxiliary capacitor C13 increases.

[0078] At time T4, the current J11 flowing through the first heating coil 11 and the current JB1 flowing through the first auxiliary reverse-connected diode DS1 reach a zero-crossing point. Then, the first auxiliary transistor TS1 transitions from the OFF period to the ON period according to the instructions of the inverter drive circuit 3.

[0079] In the fourth period P4, as shown in the fourth state 504 of Figure 6, the current flows in the opposite direction to the third state 503 of Figure 5. That is, as shown in the fourth state 504 of Figure 6, in the fourth period P4, the current flows from the first auxiliary capacitor C13, through the first auxiliary transistor TS1 and the first heating coil 11 in that order, and then back to the first auxiliary capacitor C13. In other words, the first auxiliary capacitor C13 is discharged.

[0080] During the fourth period P4, the current J11 flowing through the first heating coil 11 flows in the negative direction, and the absolute value of the current increases. The collector current JB1 of the first auxiliary transistor TS1 increases by a positive value. Also, since the first auxiliary capacitor C13 is discharged, the voltage VC13 across the first auxiliary capacitor C13 decreases.

[0081] At time T5, the first auxiliary transistor TS1 transitions from ON to OFF according to the instructions of the inverter drive circuit 3. The timing of the first auxiliary transistor TS1 turning off is set, for example, based on the period PD shown in Figure 7.

[0082] During the fifth period P5, the first main transistor TM1 and the first auxiliary transistor TS1 are held in the OFF state. In the fifth period P5, as shown in the fifth state 505 of Figure 6, current flows in the opposite direction to the second state 502 of Figure 5. That is, as shown in the fifth state 505 of Figure 6, in the fifth period P5, current flows in the parallel circuit of the first heating coil 11 and the first resonant capacitor C11. In other words, the first heating coil 11 and the first resonant capacitor C11 resonate. Therefore, as shown in Figure 4, the current JC11 flowing through the first resonant capacitor C11 has a large negative absolute value in the fifth period P5.

[0083] Furthermore, during the fifth period P5, the power stored in the first resonant capacitor C11 is discharged, causing the terminal voltage of the first resonant capacitor C11 to decrease. As a result, the collector-emitter voltage VCM of the first main transistor TM1 decreases. Also, the collector-emitter voltage VCS of the first auxiliary transistor TS1 increases.

[0084] At time T6, the collector-emitter voltage VCM of the first main transistor TM1 reaches zero volts. Then, the first main reverse-connected diode DM1 becomes conductive. In the sixth period P6, as shown in the sixth state 506 of Figure 6, current flows in the opposite direction to the first state 501 of Figure 5. That is, as shown in the sixth state 506 of Figure 6, in the sixth period P6, current flows from the first smoothing capacitor C12, through the first main transistor TM1, and the parallel circuit of the first heating coil 11 and the first resonant capacitor C11 in that order, and then back to the first smoothing capacitor C12.

[0085] Because current flows in this way, the collector current JA1 of the first main transistor TM1 is negative, and as time T progresses, the collector current JA1 of the first main transistor TM1 increases. Then, at time T7, the collector current JA1 of the first main transistor TM1 becomes "zero".

[0086] In other words, at time T7, the current JA1, which is the current flowing through the first main reverse-connected diode DM1, reaches its zero-crossing point. Then, at time T7, the first main transistor TM1 transitions from the OFF period to the ON period according to the instructions of the inverter drive circuit 3. Thus, the state of the first inverter circuit 21 at time T7 is the same as the state of the first inverter circuit 21 at time T1. In other words, the first inverter circuit 21 repeatedly performs the operations from time T1 to time T7.

[0087] As explained with reference to Figures 4-6, during the period from time T3 to time T5, i.e., the third period P3 and the fourth period P4, the first series circuit SC1 clamps the resonant voltage when the first main switching element SM1 is conducting by charging and discharging the first auxiliary capacitor C13. As explained with reference to Figure 2, the first series circuit SC1 is configured by connecting the first auxiliary switching element SS1 and the first auxiliary capacitor C13 in series. The first auxiliary switching element SS1 is configured by connecting the first auxiliary transistor TS1 and the first auxiliary reverse diode DS1 in parallel.

[0088] At time T3 in Figure 4, the current path switches when the first auxiliary reverse diode DS1 conducts, resulting in ringing current due to switching in the path between the first main resonant capacitor C11, the first auxiliary reverse diode DS1, and the first auxiliary capacitor C13. This current path corresponds to current path RC2 or current path RC4 in Figure 9, which will be described later. Furthermore, at time T6 in Figure 4, the current path switches when the first main reverse diode DM1 conducts, resulting in ringing current due to switching in the path between the first main resonant capacitor C11, the first main reverse diode DM1, and the first smoothing capacitor C12. This current path corresponds to current path RC1 or current path RC3 in Figure 9, which will be described later.

[0089] As explained with reference to Figures 4-6, the resonant voltage when the first main switching element SM1 is conducting is clamped by the charging and discharging of the first auxiliary capacitor C13, thereby suppressing fluctuations in the operating frequency F1 of the first inverter circuit 21.

[0090] For example, when the ON time of the first main transistor TM1 is increased to increase the power consumption W1 of the first heating coil 11, the ON time of the first auxiliary transistor TS1 is shortened by the same amount as the ON time of the first main transistor TM1. Also, for example, when the ON time of the first main transistor TM1 is shortened to decrease the power consumption W1 of the first heating coil 11, the ON time of the first auxiliary transistor is shortened by the same amount as the ON time of the first main transistor TM1, thereby suppressing fluctuations in the operating frequency F1. Furthermore, in this embodiment, the first main transistor TM1 is turned ON at time T1 (time T7), but it may also be turned ON during the period when the first main reverse-connected diode DM1 is energized (sixth period P6 from time T6 to time T7). Furthermore, in this embodiment, the first auxiliary transistor TS1 is turned ON at time T4, but it may also be turned ON during the period when the first auxiliary reverse-connected diode DS1 is energized (the third period P3 from time T3 to time T4).

[0091] Similarly, as explained with reference to Figures 4-6, the resonant voltage when the second main switching element SM2 is conducted is clamped by the charging and discharging of the second auxiliary capacitor C23, thereby suppressing fluctuations in the operating frequency F2 of the second inverter circuit 22. Therefore, the difference ΔF between the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 can be reduced. Consequently, interference noise can be suppressed.

[0092] [2-2. Processing of the Phase Control Unit] Next, an example of the processing of the phase control unit 415 will be described with reference to Figure 7. Figure 7 is a timing chart showing an example of the processing of the phase control unit 415 in the rice cooker 100 of this embodiment.

[0093] The horizontal axis of Figure 7 represents time T. The vertical axis of Figure 7, from top to bottom, represents the following four items: ON / OFF of the second main transistor TM2, ON / OFF of the second auxiliary transistor TS2, ON / OFF of the first main transistor TM1, and ON / OFF of the first auxiliary transistor TS1.

[0094] In Figure 7, the frequency setting unit 414 operates the first inverter circuit 21 and the second inverter circuit 22 at the same operating frequency F. The operating frequency F is, for example, "23 kHz". In this case, the operating period PD of the first inverter circuit 21 and the second inverter circuit 22 is "43 μsec (= 1000 / 23)".

[0095] In this case, the operating period PD of each of the first main transistor TM1, the first auxiliary transistor TS1, the second main transistor TM2, and the second auxiliary transistor TS2 is "43 μsec (= 1000 / 23)".

[0096] When the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it controls the inverter drive circuit 3, for example as shown in Figure 7, so that the timing of the second main transistor TM2 turning on is shifted by a predetermined time ΔP compared to the timing of the first main transistor TM1 turning on. The predetermined time ΔP is, for example, half of one period PD, i.e., 21.5 μsec (= 43 μsec / 2).

[0097] Furthermore, when the phase control unit 415 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it controls the inverter drive circuit 3, for example as shown in Figure 7, so that the timing of the second auxiliary transistor TS2 turning on is shifted by a predetermined time ΔP compared with the timing of the first auxiliary transistor TS1 turning on.

[0098] As described above, by controlling the ON timing of the second main transistor TM2 to be shifted by a predetermined time ΔP compared to the ON timing of the first main transistor TM1, the influence of noise between the first inverter circuit 21 and the second inverter circuit 22 can be suppressed. Therefore, malfunctions and damage to the first inverter circuit 21 and the second inverter circuit 22 can be suppressed.

[0099] [2-3. Processing in the frequency control section] Next, with reference to Figure 8, the processing of the frequency setting unit 414 in the rice cooker 100 of this embodiment will be described. Figure 8 is a graph showing an example of the processing of the frequency setting unit 414 in the rice cooker 100 of this embodiment.

[0100] The horizontal axis in Figure 8 represents time T. The vertical axis in Figure 8 represents the operating frequencies F of the first inverter circuit 21 and the second inverter circuit 22. When the frequency setting unit 414 supplies high-frequency current to the first heating coil 11 and the second heating coil 12, it causes the inverter drive circuit 3 to operate the first inverter circuit 21 and the second inverter circuit 22 at the same operating frequency F, and to periodically change the operating frequency F at the same timing, as shown in Figure 8. Furthermore, it is preferable to change the operating frequency F at a point near "zero volt" of the AC power supply. In this case, the generation of noise associated with the change in operating frequency F can be suppressed.

[0101] The frequency setting unit 414 changes the operating frequency F of the inverter drive circuit 3, for example, in a triangular wave pattern, as shown in Figure 8. The center frequency FC of the operating frequency F is, for example, "23.25 kHz". The maximum frequency of the operating frequency F is, for example, "24.25 kHz". The minimum frequency of the operating frequency F is, for example, "22.25 kHz". The fluctuation range ΔFA of the operating frequency F is "1.00 kHz". The fluctuation period PE of the operating frequency F is, for example, 12 seconds.

[0102] As described above, interference noise can be reduced by operating the first inverter circuit 21 and the second inverter circuit 22 at the same operating frequency F, and by periodically changing the operating frequency F at the same timing. In addition, since the operating frequency F of inverter circuit 2, which is a noise source, can be dispersed, the noise terminal voltage and radiated magnetic field can be reduced.

[0103] [3. Circuit layout] Next, with reference to Figure 9, the arrangement of the first current path RC1 to the fourth current path RC4 will be described. Figure 9 is a diagram showing the arrangement of the first current path RC1 to the fourth current path RC4 in the rice cooker 100 of this embodiment. Figure 9 is an enlarged view of a portion of the circuit board layout diagram of the rice cooker 100 shown in the upper part of Figure 1, looking from the negative Z-axis direction to the positive Z-axis direction, showing the circuit board located on the bottom surface of the rice cooker 100. The circuit board is arranged with the first inverter circuit 21 and the second inverter circuit 22 shown in Figure 2.

[0104] The first inverter circuit 21 receives AC power supplied from the commercial power supply, which is full-wave rectified by a diode bridge DB and then smoothed by a first smoothing circuit consisting of a first smoothing coil L1 and a first smoothing capacitor C12.

[0105] The second inverter circuit 22 receives AC power supplied from the commercial power supply, which is full-wave rectified by a diode bridge DB and then smoothed by a second smoothing circuit consisting of a second smoothing coil L2 and a second smoothing capacitor C22.

[0106] The first inverter circuit 21 includes a first main switching element SM1, a first resonant capacitor C11, and a first series circuit SC1. The first series circuit SC1 is configured by connecting a first auxiliary switching element SS1 and a first auxiliary capacitor C13 in series.

[0107] The second inverter circuit 22 includes a second main switching element SM2, a second resonant capacitor C21, and a second series circuit SC2. The second series circuit SC2 is configured by connecting a second auxiliary switching element SS2 and a second auxiliary capacitor C23 in series.

[0108] The first inverter circuit 21 and the first smoothing capacitor C12 constitute the first current path RC1 and the second current path RC2. The first current path RC1 is a current path that includes the first main switching element SM1, the first resonant capacitor C11, and the first smoothing capacitor C12. The second current path RC2 is a current path that includes the first auxiliary switching element SS1, the first auxiliary capacitor C13, and the first resonant capacitor C11.

[0109] The first current path RC1 is a current path that returns to the current inlet terminal of the first main reverse diode DM1, which is part of the first main switching element SM1, via the first resonant capacitor C11 and the first smoothing capacitor C12, in that order, starting from the current outflow terminal indicated by a circle in Figure 9. The current outflow terminal of the first main reverse diode DM1 corresponds to the collector terminal of the first main transistor TM1. The current inflow terminal of the first main reverse diode DM1 corresponds to the emitter terminal of the first main transistor TM1. The first current path RC1 corresponds to the current flow indicated by the dashed arrow in state 506 of Figure 5. As shown in Figure 9, the first current path RC1 is arranged in a roughly figure-eight shape.

[0110] The second current path RC2 is a current path that returns to the current inlet terminal of the first auxiliary reverse diode DS1, which is part of the first auxiliary switching element SS1, via the first auxiliary capacitor C13 and the first resonant capacitor C11, in that order, indicated by a circle in Figure 9. The current outflow terminal of the first auxiliary reverse diode DS1 corresponds to the collector terminal of the first auxiliary transistor TS1. The current inflow terminal of the first auxiliary reverse diode DS1 corresponds to the emitter terminal of the first auxiliary transistor TS1. The second current path RC2 corresponds to the current flow indicated by the dashed arrow in the third state 503 of Figure 5. As shown in Figure 9, the second current path RC2 is arranged in approximately a figure-eight shape.

[0111] The second inverter circuit 22 and the second smoothing capacitor C22 constitute the third current path RC3 and the fourth current path RC4. The third current path RC3 is a current path that includes the second main switching element SM2, the second resonant capacitor C21, and the second smoothing capacitor C22. The fourth current path RC4 is a current path that includes the second auxiliary switching element SS2, the second auxiliary capacitor C23, and the second resonant capacitor C21.

[0112] The third current path RC3 is a current path that returns to the current inlet terminal of the second main reverse diode DM2, which is part of the second main switching element SM2, via the second resonant capacitor C21 and the second smoothing capacitor C22, in that order, indicated by the circle in Figure 9. The current outflow terminal of the second main reverse diode DM2 corresponds to the collector terminal of the second main transistor TM2. The current inflow terminal of the second main reverse diode DM2 corresponds to the emitter terminal of the second main transistor TM2. As shown in Figure 9, the third current path RC3 is arranged in a roughly figure-eight shape.

[0113] The fourth current path RC4 is a current path that returns to the current inlet terminal of the second auxiliary reverse diode DS2, which is part of the second auxiliary switching element SS2, via the second auxiliary capacitor C23 and the second resonant capacitor C21 in sequence, indicated by a circle in Figure 9. The current outflow terminal of the second auxiliary reverse diode DS2 corresponds to the collector terminal of the second auxiliary transistor TS2. The current inflow terminal of the second auxiliary reverse diode DS2 corresponds to the emitter terminal of the second auxiliary transistor TS2. As shown in Figure 9, the fourth current path RC4 is arranged in a roughly figure-eight shape.

[0114] As explained with reference to Figure 9, the first current path RC1, the second current path RC2, the third current path RC3, and the fourth current path RC4 are each arranged in a roughly figure-eight shape. Therefore, the high-frequency magnetic field generated by the ringing current in the third period P3 and the sixth period P6 of the current JC11 shown in Figure 4 is canceled out, thus reducing the noise caused by this ringing current.

[0115] [4. Processing of the control unit] Next, the processing of the control unit 4 will be described with reference to Figure 10. Figure 10 is a flowchart showing an example of the "pot presence / absence determination process" in the rice cooker 100 of this embodiment. The "pot presence / absence determination process" is a process that detects the presence or absence of a pot PT, and is performed by the voltage acquisition unit 411, the current acquisition unit 416, and the pot presence / absence detection unit 417.

[0116] First, in step S101, the voltage acquisition unit 411 acquires a voltage value V from the voltage sensor SV. The voltage acquisition unit 411 also determines the power supply voltage VG of the power supply based on the voltage value V. Next, in step S103, the pot presence / absence detection unit 417 sets a threshold TH1 according to the power supply voltage VG. Next, in step S105, the pot presence / absence detection unit 417 acquires a first current value J1 from the first current sensor SA1.

[0117] Next, in step S107, the pot presence / absence detection unit 417 obtains the on-time TN1 of the first main transistor TM1 from the inverter drive circuit 3. Next, in step S109, the pot presence / absence detection unit 417 determines whether or not the following equation (1) is satisfied. TN1 × α - J1 ≤ TH1 (1) Note that the above equation (1) is the same equation as equation (1) described in [1-4. Configuration of the Control Unit].

[0118] If the pot presence / absence detection unit 417 determines that the above formula (1) is not satisfied (step S109; NO), the process proceeds to step S111. Then, in step S111, the pot presence / absence detection unit 417 detects that there is no pot PT. Next, in step S113, the pot presence / absence detection unit 417 notifies the user that there is no pot PT, for example, by displaying it on a touch panel (not shown in the figure). After that, the process ends.

[0119] If the pot presence / absence detection unit 417 determines that the above formula (1) is satisfied (step S109; YES), the process proceeds to step S115. Then, in step S115, the pot presence detection unit 417 detects that there is a pot PT. Next, in step S117, the pot presence detection unit 417 notifies the user that a pot PT is present, for example, by displaying it on a touch panel (not shown). After that, the process ends. Alternatively, the heating operation may continue afterward.

[0120] In Figure 10, the presence or absence detection unit 417 was shown to detect the presence or absence of a pot PT based on a first current value J1 and the on-time TN1 of the first main transistor TM1. However, the presence or absence detection unit 417 may also detect the presence or absence of a pot PT based on a second current value J2 and the on-time TN2 of the second main transistor TM2.

[0121] [5. Structure and Effects] As described above, the rice cooker 100 includes a first heating coil 11 that heats the bottom of the pot PT, a second heating coil 12 that is arranged concentrically with the first heating coil 11 and heats the bottom side of the pot PT, a first inverter circuit 21 that supplies a high-frequency current to the first heating coil 11, a second inverter circuit 22 that supplies a high-frequency current to the second heating coil 12, and a control unit 4 that controls the first inverter circuit 21 and the second inverter circuit 22. The frequency setting unit 414 of the control unit 4 operates the first inverter circuit 21 and the second inverter circuit 22 at approximately the same operating frequency F when supplying a high-frequency current to the first heating coil 11 and the second heating coil 12.

[0122] According to this, since the first inverter circuit 21 and the second inverter circuit 22 are operated at approximately the same operating frequency F, interference noise can be suppressed. For example, interference noise between the first inverter circuit 21 and the second inverter circuit 22 can be suppressed.

[0123] In the rice cooker 100 described above, the first inverter circuit 21 includes a first main switching element SM1 connected in series with the first heating coil 11, a first resonant capacitor C11 connected in parallel with the first heating coil 11, and a first series circuit SC1 connected in parallel with the first resonant capacitor C11 and consisting of a first auxiliary switching element SS1 and a first auxiliary capacitor C13. The second inverter circuit 22 includes a second main switching element SM2 connected in series with the second heating coil 12, a second resonant capacitor C21 connected in parallel with the second heating coil 12, and a second series circuit SC2 connected in parallel with the second resonant capacitor C21 and consisting of a second auxiliary switching element SS2 and a second auxiliary capacitor C23.

[0124] According to this, fluctuations in the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 can be suppressed. Therefore, interference noise between the first inverter circuit 21 and the second inverter circuit 22 can be suppressed.

[0125] In the rice cooker 100 described above, when supplying high-frequency current to the first heating coil 11 and the second heating coil 12, the phase control unit 415 of the control unit 4 shifts the timing of the second main switching element SM2 turning on by a predetermined time ΔP relative to the timing of the first main switching element SM1 turning on.

[0126] According to this, the influence of noise between the first inverter circuit 21 and the second inverter circuit 22 can be suppressed. Therefore, malfunctions and damage to the first inverter circuit 21 and the second inverter circuit 22 can be suppressed.

[0127] In the rice cooker 100 described above, when a high-frequency current is supplied to the first heating coil 11 and the second heating coil 12, the phase control unit 415 of the control unit 4 sets the current flowing through the second heating coil 12 to be approximately in opposite phase to the current flowing through the first heating coil 11.

[0128] According to this, the radiated magnetic field from the first heating coil 11 and the second heating coil 12 can be reduced.

[0129] In the rice cooker 100 described above, when a high-frequency current is supplied to the first heating coil 11 and the second heating coil 12, the phase control unit 415 of the control unit 4 makes the current flowing through the second heating coil 12 substantially in phase with the current flowing through the first heating coil 11.

[0130] According to this, interference of magnetic fields between the first heating coil 11 and the second heating coil 12 can be suppressed. Therefore, the collector voltages of the first main switching element SM1 and the second main switching element SM2 can be reduced.

[0131] In the rice cooker 100 described above, the control unit 4 is composed of a single computer.

[0132] According to this, compared to the case where the first inverter circuit 21 and the second inverter circuit 22 are controlled by separate computers, it is possible to suppress the occurrence of discrepancies between the operating frequency F1 of the first inverter circuit 21 and the operating frequency F2 of the second inverter circuit 22 due to variations in the components that make up the computer.

[0133] In the rice cooker 100 described above, when supplying high-frequency current to the first heating coil 11 and the second heating coil 12, the frequency setting unit 414 of the control unit 4 operates the first heating coil 11 at approximately the same operating frequency F and the second heating coil 12 at approximately the same operating frequency F, and periodically changes the operating frequency F.

[0134] According to this method, interference noise can be reduced, as well as noise terminal voltage and radiated magnetic field.

[0135] In the rice cooker 100 described above, a first smoothing circuit is provided to supply power to the first inverter circuit 21, the first smoothing circuit having a first smoothing capacitor C12, a second smoothing circuit is provided to supply power to the second inverter circuit 22, the second smoothing circuit having a second smoothing capacitor C22, the first main switching element SM1 is composed of a first main transistor TM1 and a first main reverse diode DM1, the second main switching element SM2 is composed of a second main transistor TM2 and a second main reverse diode DM2, the first auxiliary switching element SS1 is composed of a first auxiliary diode TS1 and a first auxiliary reverse diode DS1, the second auxiliary switching element SS2 is composed of a second auxiliary diode TS2 and a second auxiliary reverse diode DS2, and the first main switching element The first current path RC1, through which current flows sequentially through the first main reverse diode DM1, the first resonant capacitor C11, and the first smoothing capacitor C12 constituting the sub-SM1, and the second current path RC2, through which current flows sequentially through the first auxiliary reverse diode DS1, the first auxiliary capacitor C13, and the first resonant capacitor C11 constituting the first auxiliary switching element SS1, are each arranged in a roughly figure-eight shape. The third current path RC3, through which current flows sequentially through the second main reverse diode DM2, the second resonant capacitor C21, and the second smoothing capacitor C22 constituting the second main switching element SM2, and the fourth current path RC4, through which current flows sequentially through the second auxiliary reverse diode DS2, the second auxiliary capacitor C23, and the second resonant capacitor C21 constituting the second auxiliary switching element SS2, are each arranged in a roughly figure-eight shape.

[0136] According to this, when supplying high-frequency current to the first heating coil 11 and the second heating coil 12, noise caused by the current flowing through the first current path RC1, the second current path RC2, the third current path RC3, and the fourth current path RC4 on the substrate can be reduced.

[0137] In the rice cooker 100 described above, the first inverter circuit 21 and the second inverter circuit 22 each have a voltage sensor SV that detects a voltage value V corresponding to the power supply voltage VG of the AC power supply that supplies power. When the rice cooker 100 starts cooking rice, the on-time setting unit 412 of the control unit 4 sets the upper limit value TX1 of the on-time of the first main switching element SM1 and the upper limit value TX2 of the on-time of the second main switching element SM2 according to the voltage value detected by the voltage sensor SV.

[0138] According to this, even when the range of the power supply voltage VG of the connected AC power supply is wide, damage to the first inverter circuit 21 and the second inverter circuit 22 can be suppressed.

[0139] In the rice cooker 100 described above, there is a voltage sensor SV that detects a voltage value V corresponding to the power supply voltage VG of the AC power supply that supplies power to the first inverter circuit 21 and the second inverter circuit 22, respectively. When the rice cooker 100 starts cooking rice, the power consumption setting unit 413 of the control unit 4 controls the current values ​​of the first inverter circuit 21 and the second inverter circuit 22 according to the voltage value detected by the voltage sensor SV, so that the sum WS of the power consumption W1 of the first heating coil 11 and the power consumption W2 of the second heating coil 12 becomes a predetermined value WT.

[0140] According to this, even if the range of the power supply voltage VG of the connected AC power supply is wide, the sum WS of the power consumption W1 of the first heating coil 11 and the power consumption W2 of the second heating coil 12 can be controlled to a predetermined value WT.

[0141] The rice cooker 100 includes a first current sensor SA1 that detects a first current value J1 which is the current value input to the first inverter circuit 21, and a second current sensor SA2 that detects a second current value J2 which is the current value input to the second inverter circuit 22. The control unit 4 has a pot presence / absence detection unit 417 that detects the presence or absence of a pot PT. The pot presence / absence detection unit 417 detects the presence or absence of a pot PT based on at least one of the first current value J1 and the on-time of the first main switching element SM1, and the second current value J2 and the on-time of the second main switching element SM2.

[0142] According to this, even when the range of the power supply voltage VG of the connected AC power supply is wide, the presence or absence of the pot PT can be properly detected. Therefore, for example, when the absence of a pot is detected, the power supply to the first inverter circuit 21 and the second inverter circuit 22 can be stopped, and the user can be notified.

[0143] The control unit 4 of the rice cooker 100 includes a first heating coil 11 for heating the bottom of the pot PT, a second heating coil 12 arranged concentrically with the first heating coil 11 for heating the bottom side of the pot PT, a first inverter circuit 21 for supplying a high-frequency current to the first heating coil 11, and a second inverter circuit 22 for supplying a high-frequency current to the second heating coil 12. The control unit 4 operates the first inverter circuit 21 and the second inverter circuit 22 at approximately the same operating frequency F when supplying a high-frequency current to the first heating coil 11 and the second heating coil 12.

[0144] According to this, the control unit 4 of the rice cooker 100 produces the same effects as the rice cooker 100 described above.

[0145] The control method for the rice cooker 100 includes a first heating coil 11 for heating the bottom of the pot PT, a second heating coil 12 arranged concentrically with the first heating coil 11 for heating the bottom side of the pot PT, a first inverter circuit 21 for supplying a high-frequency current to the first heating coil 11, and a second inverter circuit 22 for supplying a high-frequency current to the second heating coil 12. The control method for the rice cooker 100 is such that when supplying a high-frequency current to the first heating coil 11 and the second heating coil 12, the first inverter circuit 21 and the second inverter circuit 22 are operated at approximately the same operating frequency F.

[0146] According to this, the control method for the rice cooker 100 produces the same effect as the rice cooker 100 described above.

[0147] (Other embodiments) As described above, the above embodiment has been explained as an example disclosed in this application. However, the technology in this disclosure is not limited to this embodiment and can be applied to embodiments that have been modified, replaced, added, or omitted. Furthermore, it is possible to combine the components described in the above embodiment to create new embodiments. Therefore, other embodiments are described below as examples.

[0148] In the embodiments described above, a rice cooker 100 was used as an example of the "induction heating cooker" of the Disclosure. However, the "induction heating cooker" of the Disclosure is not limited to a rice cooker 100. The "induction heating cooker" of the Disclosure may be, for example, a so-called "auto cooker".

[0149] In the embodiment described above, the "heating container" is a pot PT, but the "heating container" can be any container that holds food and is made of a material that can be induction heated.

[0150] In the embodiment described above, the first heating coil 11 is positioned facing the bottom of the pot PT, and the second heating coil 12 is positioned facing the bottom side of the pot PT, but the invention is not limited to this. For example, the first heating coil 11 and the second heating coil 12 may be positioned facing the bottom of the pot PT.

[0151] In the embodiment described above, the rice cooker 100 has two heating coils, namely a first heating coil 11 and a second heating coil 12, but it may have three or more heating coils.

[0152] The configuration of the control unit 4 shown in Figure 3 is merely an example, and the specific implementation is not particularly limited. In other words, it is not necessarily required that hardware corresponding to each part be implemented individually; it is also possible to configure the system so that a single processor executes a program to realize the functions of each part. Furthermore, some of the functions realized by software in the above-described embodiment may be implemented by hardware, or conversely, some of the functions realized by hardware may be realized by software.

[0153] The processing steps shown in Figure 10 are divided according to the main processing content to facilitate understanding of the process, and the processing is not limited by the way the processing units are divided or their names. Depending on the processing content, it may be further divided into more steps. Alternatively, it may be divided so that one step unit includes even more processing. Furthermore, the order of the steps may be changed as appropriate, as long as it does not hinder the intent of this disclosure.

[0154] Since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the claims or their equivalents.

[0155] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0156] (Technical 1) An induction heating cooker comprising: a first heating coil for heating the central region of the bottom surface of a heating container; a second heating coil arranged concentrically with the first heating coil for heating the outer peripheral region of the central region of the heating container; a first inverter circuit for supplying a high-frequency current to the first heating coil; a second inverter circuit for supplying a high-frequency current to the second heating coil; and a control unit for controlling the first inverter circuit and the second inverter circuit, wherein the control unit operates the first inverter circuit and the second inverter circuit at substantially the same operating frequency when supplying a high-frequency current to the first heating coil and the second heating coil. With this configuration, the first inverter circuit and the second inverter circuit are operated at approximately the same operating frequency, thus suppressing interference noise. For example, interference noise between the first inverter circuit and the second inverter circuit can be suppressed.

[0157] (Technology 2) The induction heating cooker according to Technology 1, wherein the first inverter circuit comprises a first main switching element connected in series with the first heating coil, a first resonant capacitor connected in parallel with the first heating coil, and a first series circuit connected in parallel with the first resonant capacitor and comprising a first auxiliary switching element and a first auxiliary capacitor, and the second inverter circuit comprises a second main switching element connected in series with the second heating coil, a second resonant capacitor connected in parallel with the second heating coil, and a second series circuit connected in parallel with the second resonant capacitor and comprising a second auxiliary switching element and a second auxiliary capacitor. This configuration allows for suppression of fluctuations in the operating frequencies of both the first and second inverter circuits. Consequently, interference noise between the first and second inverter circuits can be suppressed.

[0158] (Technical 3) The induction heating cooker according to Technical 2, wherein when a high-frequency current is supplied to the first heating coil and the second heating coil, the control unit shifts the timing of the second main switching element to turn on by a predetermined time relative to the timing of the first main switching element to turn on. This configuration suppresses the effects of noise between the first inverter circuit and the second inverter circuit. Therefore, malfunctions and damage to both the first and second inverter circuits can be suppressed.

[0159] (Technical 4) The induction heating cooker according to Technical 2, wherein when a high-frequency current is supplied to the first heating coil and the second heating coil, the control unit makes the current flowing through the second heating coil substantially out of phase with respect to the current flowing through the first heating coil. This configuration allows for a reduction in the radiated magnetic fields from the first and second heating coils.

[0160] (Technical 5) The induction heating cooker according to Technical 2, wherein when a high-frequency current is supplied to the first heating coil and the second heating coil, the control unit makes the current flowing through the second heating coil substantially in phase with the current flowing through the first heating coil. This configuration suppresses interference between the magnetic fields between the first heating coil and the second heating coil. Therefore, the collector voltages of the first and second main switching elements can be reduced.

[0161] (Technical 6) The control unit is comprised of a single computer, and the induction heating cooker is as described in any one of Technical 1 to Technical 5. This configuration makes it possible to suppress the occurrence of discrepancies between the operating frequency of the first inverter circuit and the operating frequency of the second inverter circuit due to variations in the components that make up the computer, compared to the case where the first inverter circuit and the second inverter circuit are controlled by separate computers.

[0162] (Technology 7) An induction heating cooker according to any one of Technology 1 to Technology 6, wherein when a high-frequency current is supplied to the first heating coil and the second heating coil, the control unit operates the first heating coil and the second heating coil at substantially the same operating frequency and periodically changes the operating frequency. This configuration reduces interference noise, as well as noise terminal voltage and radiated magnetic field.

[0163] (Technical 8) The first inverter circuit and the second inverter circuit are provided with a smoothing circuit that supplies power to them, the smoothing circuit having a smoothing capacitor, each of the first main switching element and the second main switching element being composed of a main IGBT and a main reverse-connected diode, each of the first auxiliary switching element and the second auxiliary switching element being composed of an auxiliary IGBT and an auxiliary reverse-connected diode, the first current path flowing sequentially through the main reverse-connected diode, the first resonant capacitor, and the smoothing capacitor that constitute the first main switching element, and the first auxiliary switch An induction heating cooker according to any one of the technologies 2 to 5, wherein each of the second current path, which flows sequentially through the auxiliary reverse-connected diode, the first auxiliary capacitor, and the first resonant capacitor constituting the switching element, is arranged in a substantially figure-eight shape, and each of the third current path, which flows sequentially through the main reverse-connected diode, the second resonant capacitor, and the smoothing capacitor constituting the second main switching element, and the fourth current path, which flows sequentially through the auxiliary reverse-connected diode, the second auxiliary capacitor, and the second resonant capacitor constituting the second auxiliary switching element, is arranged in a substantially figure-eight shape. This configuration makes it possible to reduce noise caused by the current flowing through the first, second, third, and fourth current paths on the substrate when supplying high-frequency current to the first and second heating coils.

[0164] (Technology 9) An induction cooker according to any one of Techniques 2 to 5, wherein each of the first inverter circuit and the second inverter circuit has a voltage sensor that detects a voltage value corresponding to the power supply voltage of the AC power supply that supplies power, and when the induction cooker starts cooking, the control unit sets an upper limit on the on time of the first main switching element and an upper limit on the on time of the second main switching element according to the voltage value detected by the voltage sensor. This configuration makes it possible to suppress damage to the first inverter circuit and the second inverter circuit, even when the range of power supply voltage of the connected AC power supply is wide.

[0165] (Technology 10) An induction cooker according to any one of Techniques 2 to 5, comprising a voltage sensor that detects a voltage value corresponding to the power supply voltage of an AC power supply that supplies power to each of the first inverter circuit and the second inverter circuit, wherein when the induction cooker starts cooking, the control unit controls the current values ​​of the first inverter circuit and the second inverter circuit according to the voltage value detected by the voltage sensor so that the sum of the power consumption of the first heating coil and the power consumption of the second heating coil is a predetermined value. With this configuration, even when the range of power supply voltage of the connected AC power supply is wide, the sum of the power consumption of the first heating coil and the power consumption of the second heating coil can be controlled to a predetermined value.

[0166] (Technical 11) An induction heating cooker according to any one of Technical 2 to Technical 5, comprising: a first current sensor for detecting a first current value which is a current value input to the first inverter circuit; and a second current sensor for detecting a second current value which is a current value input to the second inverter circuit, wherein the control unit has a container presence / absence detection unit for detecting the presence or absence of the heating container, and the container presence / absence detection unit detects the presence or absence of the heating container based on at least one of the first current value and the on-time of the first main switching element, and the second current value and the on-time of the second main switching element. This configuration allows for accurate detection of the presence or absence of a pot, even when the voltage range of the connected AC power supply is wide. Therefore, for example, when the absence of a pot is detected, the power supply to the first inverter circuit and the second inverter circuit can be stopped, and the user can be notified.

[0167] (Technical 12) A control device for an induction cooker, comprising: a first heating coil for heating the central region of the bottom surface of a heating container; a second heating coil arranged concentrically with the first heating coil for heating the outer peripheral region of the central region of the heating container; a first inverter circuit for supplying a high-frequency current to the first heating coil; and a second inverter circuit for supplying a high-frequency current to the second heating coil, wherein the control device operates the first inverter circuit and the second inverter circuit at substantially the same operating frequency when supplying a high-frequency current to the first heating coil and the second heating coil. This configuration produces the same effect as the induction cooker described in Technology 1.

[0168] (Technical 13) A control method for an induction heating cooker having a first heating coil for heating the central region of the bottom surface of a heating container, a second heating coil arranged concentrically with the first heating coil for heating the outer peripheral region of the central region of the heating container, a first inverter circuit for supplying a high-frequency current to the first heating coil, and a second inverter circuit for supplying a high-frequency current to the second heating coil, wherein when supplying a high-frequency current to the first heating coil and the second heating coil, the first inverter circuit and the second inverter circuit are operated at substantially the same operating frequency. This configuration produces the same effect as the induction cooker described in Technology 1. [Industrial applicability]

[0169] As described above, the induction cooker, the control device for the induction cooker, and the control method for the induction cooker according to the present invention can be used for applications that suppress interference noise. [Explanation of Symbols]

[0170] 100 Rice cookers (induction heating cookers) 11. First heating coil 12. Second heating coil 2. Inverter Circuit 21. First Inverter Circuit 22 Second Inverter Circuit 3. Inverter drive circuit 4. Control Unit (Control Device) 41 processors 411 Voltage acquisition section 412 ON time setting section 413 Power consumption setting section 414 Frequency setting section 415 Phase Control Unit 416 Current acquisition section 417 Pot presence / absence detection unit (container presence / absence detection unit) 42 memory 421 Control Program C11 First resonant capacitor C12 First smoothing capacitor (smoothing capacitor) C13 First auxiliary capacitor C21 Second resonant capacitor C22 Second smoothing capacitor (smoothing capacitor) C23 Second auxiliary capacitor DM1 First main reverse-connected diode DM2 Second main reverse-connected diode DS1 First auxiliary reverse-connected diode DS2 Second auxiliary reverse-connected diode F, F1, F2 operating frequency L1 First smoothing coil L2 Second smoothing coil PT pot (heating container) RC1 First current path RC2 Second current path RC3 Third current path RC4 Fourth current path SA1 First Current Sensor SA2 Second Current Sensor SC1 First Series Circuit SC2 2nd series circuit SM1 First main switching element SM2 First Main Switching Element SS1 First auxiliary switching element SS2 Second Auxiliary Switching Element SV voltage sensor T time TM1 First main transistor (main IGBT) TM2 Second main transistor (main IGBT) TS1 First auxiliary transistor (auxiliary IGBT) TS2 Second auxiliary transistor (auxiliary IGBT)

Claims

1. A first heating coil that heats the central region of the bottom surface of the heating container, A second heating coil is positioned concentrically with the first heating coil and heats the outer peripheral region of the central region of the heating container, A first inverter circuit that supplies high-frequency current to the first heating coil, A second inverter circuit that supplies high-frequency current to the second heating coil, The system comprises a control unit that controls the first inverter circuit and the second inverter circuit, When the control unit supplies high-frequency current to the first heating coil and the second heating coil, it operates the first inverter circuit and the second inverter circuit at substantially the same operating frequency. Induction heating cooker.

2. The first inverter circuit is, A first main switching element connected in series with the first heating coil, A first resonant capacitor connected in parallel with the first heating coil, A first series circuit consisting of a first auxiliary switching element and a first auxiliary capacitor is connected in parallel with the first resonant capacitor, It has, The second inverter circuit is, A second main switching element connected in series with the second heating coil, A second resonant capacitor connected in parallel with the second heating coil, A second series circuit is connected in parallel with the second resonant capacitor and consists of a second auxiliary switching element and a second auxiliary capacitor, Having, The induction heating cooker according to claim 1.

3. When supplying high-frequency current to the first heating coil and the second heating coil, the control unit shifts the timing of the second main switching element turning on by a predetermined time relative to the timing of the first main switching element turning on. The induction heating cooker according to claim 2.

4. When supplying high-frequency current to the first heating coil and the second heating coil, the control unit makes the current flowing through the second heating coil substantially out of phase with respect to the current flowing through the first heating coil. The induction heating cooker according to claim 2.

5. When supplying high-frequency current to the first heating coil and the second heating coil, the control unit makes the current flowing through the second heating coil substantially in phase with the current flowing through the first heating coil. The induction heating cooker according to claim 2.

6. The control unit consists of one computer. The induction heating cooker according to claim 1.

7. When supplying high-frequency current to the first heating coil and the second heating coil, the control unit operates the first heating coil and the second heating coil at substantially the same operating frequency, and periodically changes the operating frequency. The induction heating cooker according to claim 1.

8. The system comprises a smoothing circuit that supplies power to the first inverter circuit and the second inverter circuit. The smoothing circuit has a smoothing capacitor, Each of the first main switching element and the second main switching element is composed of a main IGBT and a main reverse-connected diode. Each of the first auxiliary switching element and the second auxiliary switching element is composed of an auxiliary IGBT and an auxiliary reverse-connected diode. A first current path flows sequentially through the main reverse-connected diode, the first resonant capacitor, and the smoothing capacitor that constitute the first main switching element, The auxiliary reverse-connected diode, the first auxiliary capacitor, and the second current path through which the current flows sequentially through the first resonant capacitor, which constitute the first auxiliary switching element, are each arranged in a roughly figure-eight shape. A third current path flows sequentially through the main reverse-connected diode, the second resonant capacitor, and the smoothing capacitor that constitute the second main switching element, The auxiliary reverse-connected diode, the second auxiliary capacitor, and the second resonant capacitor constituting the second auxiliary switching element, each of which flows sequentially through the fourth current path, are arranged in a roughly figure-eight shape. An induction heating cooker according to any one of claims 2 to 5.

9. Each of the first inverter circuit and the second inverter circuit is equipped with a voltage sensor that detects a voltage value corresponding to the power supply voltage of the AC power supply that provides power, When the induction heating cooker starts cooking, the control unit sets the upper limit of the on-time of the first main switching element and the upper limit of the on-time of the second main switching element according to the voltage value detected by the voltage sensor. An induction heating cooker according to any one of claims 2 to 5.

10. The system includes a voltage sensor that detects a voltage value corresponding to the power supply voltage of the AC power supply that provides power to each of the first inverter circuit and the second inverter circuit, When the induction heating cooker starts cooking, the control unit controls the current values ​​of the first inverter circuit and the second inverter circuit so that the sum of the power consumption of the first heating coil and the power consumption of the second heating coil becomes a predetermined value, according to the voltage value detected by the voltage sensor. An induction heating cooker according to any one of claims 2 to 5.

11. A first current sensor that detects a first current value which is the current value input to the first inverter circuit, A second current sensor detects a second current value, which is the current value input to the second inverter circuit, Equipped with, The control unit has a container presence / absence detection unit that detects the presence or absence of the heating container, The container presence / absence detection unit detects the presence or absence of the heating container based on at least one of the first current value and the on-time of the first main switching element, and the second current value and the on-time of the second main switching element. An induction heating cooker according to any one of claims 2 to 5.

12. A first heating coil that heats the central region of the bottom surface of the heating container, A second heating coil is positioned concentrically with the first heating coil and heats the outer peripheral region of the central region of the heating container, A first inverter circuit that supplies high-frequency current to the first heating coil, A control device for an induction cooker, comprising a second inverter circuit that supplies a high-frequency current to the second heating coil, The control device, when supplying high-frequency current to the first heating coil and the second heating coil, operates the first inverter circuit and the second inverter circuit at substantially the same operating frequency. Control device for induction heating cookers.

13. A first heating coil that heats the central region of the bottom surface of the heating container, A second heating coil is positioned concentrically with the first heating coil and heats the outer peripheral region of the central region of the heating container, A first inverter circuit that supplies high-frequency current to the first heating coil, A control method for an induction heating cooker, comprising a second inverter circuit that supplies a high-frequency current to the second heating coil, When supplying high-frequency current to the first heating coil and the second heating coil, the first inverter circuit and the second inverter circuit are operated at substantially the same operating frequency. A method for controlling an induction heating cooker.

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