JP2004253297A - Electromagnetic induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic induction heating cooker in which cooking can be continued without stopping an inverter circuit which automatically stops the operation of a pot detection circuit when cooking is carried out by setting a power setting value at small, and the problem of determining a small pot as having no-pot due to the difference of the size of the diameter of the pot can be solved also. <P>SOLUTION: This electromagnetic induction heating cooker comprises a phase difference detector circuit for outputting a phase differential detected signal by detecting the phase differential between an output voltage and an output current of an inverter circuit, and a pot detection circuit which, when the value of the phase differential detected signal is larger than the phase differential determination signal determined beforehand, determines that the pot is not mounted and outputs a no-pot detected signal, and by stopping the drive of the inverter drive circuit, stops the supply of a high frequency current. A frequency-corresponding pot-detection control circuit is provided which drives the inverter drive circuit SD regardless of the no-pot detected signal, when the output frequency of the inverter circuit is higher than the frequency judgement signal determined beforehand. Then, it controls the drive of the inverter drive circuit according to the no-pot detected signal, when the output frequency is lower than the frequency determination signal. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electromagnetic induction heating cooker that supplies a high-frequency current to an induction heating coil using an inverter circuit and heats a cooking pot by electromagnetic induction, and is particularly mounted on a top plate on an upper surface of the induction heating coil. The present invention relates to a technique for determining the presence or absence of a pot.
[0002]
[Prior art]
FIG. 8 is an electrical connection diagram of a conventional electromagnetic induction heating cooker. 8, 1 is a commercial power supply, 2 is a rectifying circuit for rectifying the commercial power supply 1, 10 is a smoothing circuit 3 for smoothing the output of the rectifying circuit 2 to DC, an induction heating coil 4, a resonance capacitor 4, and a bipolar transistor. And an inverter circuit having a switching element 6 having an anti-parallel diode, 7 is an oscillation control unit for controlling on / off of the switching element 6, and 8 is a load for determining whether a load magnetically coupled to the induction heating coil 4 is appropriate or inappropriate. The detection device 9 is a switch for turning on and off the output signal of the load detection device 8 to the oscillation control unit 7.
[0003]
Normally, the user keeps the switch 9 closed. If the load is appropriate, no signal is output from the load detection device, the oscillation control unit 7 drives the switching element 6, and the switching element 6 is driven by induction heating. The coil 4 is energized to overheat the load. If the load is improper, such as a knife or fork placed incorrectly, the load detector 8 outputs a signal, the oscillation controller 7 stops the oscillation to the switching element 6, and if the load is inappropriate, the heating is not performed.
[0004]
Next, a case in which a load determined to be inappropriate by the load detection device 8, for example, a load having a small shape is to be heated will be described. The user keeps the switch 9 open. The load detection device 8 determines that the load is inappropriate, and outputs a signal. However, since the switch 9 is open, the signal is not input to the oscillation control unit 7, the oscillation control unit 7 oscillates to the switching element 6, and the switching element 6 energizes the induction heating coil 4 to apply an improper load. Heat. However, if the user forgets to close the switch 9 and keeps it open, the inappropriate load is heated. (See Patent Document 1)
[0005]
The electromagnetic induction heating cooker of the prior art 2 includes a phase difference detection circuit that detects a phase difference between the output voltage and the current of the inverter circuit, and increases the output frequency of the inverter when the current exceeds a set value of the current setter. A current holding circuit that holds the current below the set value, the phase difference detection value is compared with the phase difference set value of the phase difference setter, and when the detected value is larger than the set value, the load container is a non-magnetic material. Alternatively, a load discriminating circuit for judging that there is no load and judging that the load container is a magnetic material when the detected value is equal to or less than the set value is provided. However, as the output frequency of the inverter circuit increases, the accuracy of the phase difference detection value deteriorates.
[0006]
[Patent Document 1]
JP-A-5-10947
[Problems to be solved by the invention]
In a conventional electromagnetic induction heating cooker, the placement of a pot or the like on the top plate is electrically detected, and if it is determined that there is no pot, a measure is taken to stop the output of the inverter for the purpose of preventing waste of power and the like. I was However, when cooking is performed with the power set value set to the minimum, there is a problem in the accuracy of determination of the pan detection circuit described below, and there is a problem that the output of the inverter circuit is stopped and cooking cannot be performed. In addition, there is a problem that a small pot is determined to be no pot due to a difference in the diameter of the pot.
[0008]
[Means for Solving the Problems]
The invention according to claim 1 includes a resonance capacitor C2 and C3, an induction heating coil HL that forms a series resonance with the resonance capacitors C2 and C3, and a rectifier circuit DR1 that rectifies a commercial AC power supply and converts it into a DC voltage. An inverter circuit that supplies a high-frequency current to the induction heating coil HL with the DC voltage of the rectifier circuit DR1 as an input, and a power calculation circuit SA that calculates the input power of the inverter circuit and outputs a power calculation signal Sa, A power setting circuit PC for outputting the power setting signal Pc, a differential amplifier circuit CO for differentially amplifying the power calculation signal Sa and the power setting signal Pc, and the inverter circuit in accordance with the differential amplified signal ΔI. An inverter drive circuit SD for controlling the output frequency of the inverter circuit, and a phase difference between the output voltage Cv2 and the output current Ct2 of the inverter circuit is detected. A phase difference detection circuit PD for outputting the difference detection signal Pd, and determining that the pot is not placed when the value of the phase difference detection signal Pd is larger than a predetermined value of the phase difference determination signal Pr. A pan detection circuit that outputs a non-detection signal Cp to stop driving of the inverter drive circuit SD to stop the supply of the high-frequency current, and that the pan mounted on the induction heating coil HL is actuated by electromagnetic induction. When the output frequency of the inverter circuit is higher than a predetermined value of the frequency determination signal Fr, the operation of the pan detection circuit is stopped when the output frequency of the inverter circuit is higher than the value of the frequency determination signal Fr. An electromagnetic induction heating cooker comprising a frequency corresponding pan detection control circuit for operating the pan detection circuit when the value is lower than the value.
[0009]
The invention according to claim 2 is to stop the operation of the pan detection circuit when the output current of the inverter circuit is smaller than a predetermined value of the current discrimination signal Er, and the output current is larger than the value of the current discrimination signal Er. 2. The electromagnetic induction heating cooker according to claim 1, wherein a current-capable pan detection control circuit that sometimes activates the pan detection circuit is replaced with the frequency-capable pan detection control circuit.
[0010]
The invention according to claim 3 is to stop the operation of the pot detection circuit when the power setting signal Pc is smaller than a predetermined value of the power discriminating signal Pf, and when the power setting signal Pc is smaller than the value of the power discriminating signal Pf. 2. The electromagnetic induction heating cooker according to claim 1, wherein a power-adaptive pan detection control circuit for operating the pan detection circuit when it is large is replaced with the frequency-adaptive pan detection control circuit.
[0011]
The invention according to claim 4 is characterized in that when the pan detection signal Cp of the pan detection circuit is input to the inverter drive circuit SD, a pan-less state is displayed by a display LED. The electromagnetic induction heating cooker according to claim 2 or 3.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an electrical connection diagram of the electromagnetic induction heating cooker of the present invention.
[0013]
In FIG. 1, a rectifier circuit DR1 rectifies the output of a commercial AC power supply and converts it to a DC voltage, and a smoothing capacitor C1 smoothes the voltage converted to DC.
[0014]
The input current detection circuit ID detects an input current value and outputs an input current detection signal Id, and the input voltage detection circuit IV detects an input voltage value and outputs an input voltage detection signal Iv.
[0015]
The switching element TR1 and the switching element TR2 are switching elements forming a half-bridge type inverter circuit. For example, MOSFETs or IGBTs are used. The induction heating coil HL forms a series resonance with the resonance capacitor C2 and the resonance capacitor C3. The pot PB is placed on the induction heating coil HL and is heated by electromagnetic induction.
[0016]
The inverter drive circuit SD performs PFM control for modulating the pulse frequency with a constant pulse width ratio according to the value of the control processing signal Sc from the control operation circuit SC, and alternately switches the switching elements TR1 and TR2. And outputs a switching element drive signal Sd1 and a switching element drive signal Sd2 to drive the switching element.
[0017]
The power calculation circuit SA receives the input current detection signal Id and the input voltage detection signal Iv and calculates the input power of the inverter. The power setting circuit PC sets a predetermined power setting signal Pc.
[0018]
The differential amplifier circuit CO differentially amplifies the power setting signal Pc and the power operation signal Sa, and outputs the value of the differential amplified signal ΔI. The control operation circuit SC starts operation when the heating start signal Ts is input from the heating switch TS, performs an operation according to the value of the differential amplified signal ΔI, and performs the operation when the value of the differential amplified signal ΔI is large. The value of the control processing signal Sc is reduced, and conversely, when the value of the differential amplified signal ΔI is small, the value of the control processing signal Sc is increased. Further, a predetermined phase difference set value and a predetermined frequency set value inputted by the operation panel OA are calculated, converted into a phase difference discrimination signal Pr and a frequency discrimination signal Fr, and outputted.
[0019]
When the value of the control processing operation signal Sc input from the control operation circuit SC is small, the inverter drive circuit SD increases the frequency of the PFM control to increase the impedance value of the resonance tank including the induction heating coil HL and the resonance capacitors C2 and C3. And the current flowing through the induction heating coil HL is reduced. Conversely, when the value of the control operation signal Sc is large, the current flowing through the induction heating coil HL is increased by lowering the frequency of the PFM control and decreasing the impedance value of the resonance tank to increase the current flowing through the induction heating coil HL. Perform current control. When the output signal from the AND circuit AND becomes High level, the operation of the inverter drive circuit SD is stopped.
[0020]
The pan detection circuit is formed by a phase difference detection circuit PD and a comparison circuit CP. The comparison circuit CP compares the phase difference detection signal Pd with the phase difference determination signal Pr, and the phase difference detection signal Pd When it is larger than the phase difference determination signal Pr, it is determined that there is no pot, and a no-pan detection signal Cp is output.
[0021]
The phase difference detection circuit PD is formed by the pulsating circuit PK shown in FIG. 2 and the phase difference / voltage conversion circuit PE, and the pulsing circuit PK outputs the positive time of the output current detection signal Ct2 shown in FIG. The width is converted to a pulse signal Pk shown in FIG. The output voltage detection circuit CV2 half-wave rectifies the AC output voltage of the inverter circuit (not shown) and outputs an output voltage detection signal Cv2 shown in FIG. The phase difference / voltage conversion circuit PE detects a phase difference θ between the pulse signal Pk and the output voltage detection signal Cv2, converts the phase difference θ into a voltage, and outputs the voltage as a phase difference detection signal Pd. If the value of the phase difference θ is large, the output voltage increases, and if the value of the phase difference θ is small, the output voltage decreases.
[0022]
The frequency corresponding pot detection control circuit is formed by a frequency / voltage conversion circuit FV, a second comparison circuit CP2, and an AND circuit AND, and the frequency / voltage conversion circuit FV converts the frequency of the output voltage detection signal Cv2 into a voltage, When the frequency is high, the output voltage increases, and when the frequency is low, the output voltage decreases. The second comparison circuit CP2 compares the frequency / voltage conversion signal Fv with the frequency determination signal Fr, and when the frequency / voltage conversion signal Fv is larger than the frequency determination signal Fr, sets the pan detection control signal Cp2 to Low. Output to level. The AND circuit AND operates the inverter drive circuit SD regardless of the pan detection signal Cp when the pan detection control signal Cp2 goes low.
[0023]
FIG. 3 is a waveform diagram illustrating the operation of the present invention. 3A shows the output voltage detection signal Cv2, and FIG. 3B shows the output current detection signal Ct2 when the pot PB is placed or not placed. 3 (C) shows the pulse signal Pk when the pot PB is not placed, and FIG. 3 (D) shows the pulse signal Pk when the pot PB is placed. E) shows the phase difference detection signal Pd when the pot PB is placed or not placed, and FIG. 3E shows when the pot PB is placed or placed. 7 shows the frequency / voltage conversion signal Fv when there is no signal.
[0024]
Next, the operation of determining whether or not there is a pan on the top plate will be described with reference to the waveform diagram shown in FIG.
[0025]
First, when the power is set to a predetermined value that normally uses the value of the power setting signal Pc and the heating is performed without the pan, the pan detection circuit uses the phase difference / voltage conversion circuit PE for the pan detection circuit in FIG. 3) is detected from the output voltage detection signal Cv2 of FIG. 3) and the pulse signal Pk of FIG. 3C. At this time, the value of the phase difference θ increases, and the phase difference θ is converted into a voltage and output as a phase difference detection signal Pd shown in FIG. The comparison circuit CP compares the phase difference detection signal Pd with the phase difference discrimination signal Pr so that the phase difference detection signal Pd becomes larger than the phase difference discrimination signal Pr. Cp is set to High level and output to the AND circuit AND. Further, by changing the value of the above-mentioned phase difference determination signal Pr from the operation panel, it is possible to determine that a small pan has been determined to be without a pan but has a pan.
[0026]
The frequency / voltage conversion circuit FV of the frequency corresponding pan detection control circuit converts the frequency of the output voltage detection signal Cv2 into a voltage, and outputs the frequency / voltage conversion signal Fv shown in FIG. At this time, the power setting signal Pc is set to the normally used power, and when the heating is performed without the pan, a current flows through the induction heating coil HL, and the frequency of the output voltage detection signal Cv2 decreases. The value of the voltage conversion signal Fv decreases. The second comparison circuit CP2 compares the frequency / voltage conversion signal Fv with the frequency determination signal Fr, makes the frequency / voltage conversion signal Fv smaller than the frequency determination signal Fr, and sets the pan detection control signal to High level. Output to AND circuit AND. The AND circuit AND sets the output signal to the high level so that the pan detection control signal Cp2 and the pan non-detection signal Cp go to the high level, and stops the operation of the inverter drive circuit SD.
[0027]
When the value of the power setting signal Pc is set to the power to be used normally and heating is performed in the state where the pan is present, the pan detection circuit uses the phase difference / voltage conversion circuit PE to output the output voltage detection signal Cv2 of FIG. The phase difference θ shown in FIG. 3D from the pulse signal Pk of FIG. 3D is detected. At this time, the value of the phase difference θ is smaller than in the panless state, and the phase difference detection signal Pd is smaller. The comparison circuit CP compares the phase difference detection signal Pd with the phase difference discrimination signal Pr, determines that the phase difference detection signal Pd is smaller than the phase difference discrimination signal Pr, determines that there is a pan, and sets the pan non-detection signal Cp to Low. And output to the AND circuit AND. When the pot absence detection signal Cp goes low, the output signal of the AND circuit AND goes low, and the inverter drive circuit SD operates. The value of the phase difference θ also changes depending on the size of the diameter of the pot PB, and the smaller the diameter, the larger the value of the phase difference θ. As described above, depending on the value of the phase difference determination signal Pr, a pan with a small diameter may be determined to be in a panless state. Further, in the present invention, by setting the phase difference determination signal Pr to an optimum value using the operation panel OA, it is possible to determine that the pan PB having the small diameter is in the pan state.
[0028]
When cooking is performed with the value of the power setting signal Pc set to the minimum power consumption, the frequency of the output voltage and the output current of the inverter circuit becomes extremely high. At this time, the value of the phase difference θ by the phase difference / voltage conversion circuit PE causes an error in the phase difference detection because the frequency of the output voltage and the output current becomes extremely high. A problem arises in sex.
[0029]
When the value of the power setting signal Pc is set to the minimum power consumption, the frequency corresponding pan detection control circuit increases the frequency of the output voltage detection signal Cv2 and increases the value of the frequency / voltage conversion signal Fv. The second comparison circuit CP2 compares the frequency / voltage conversion signal Fv with the frequency discrimination signal, and when the frequency / voltage conversion signal Fv becomes larger than the frequency discrimination signal, sets the pan detection control signal to Low level and sets the AND circuit. Output to AND. When the pan detection control signal Cp2 goes low, the output signal of the AND circuit AND goes low regardless of the pan non-detection signal Cp, and the inverter drive circuit SD operates. As described above, even when cooking is performed with the power setting signal Pc set to the minimum power consumption, cooking is not stopped by the pan detection circuit. At this time, even if small items such as knives and forks are placed, they are not heated because of the minimum power.
[0030]
[Example 2]
FIG. 4 is an electrical connection diagram of the electromagnetic induction heating cooker according to the second embodiment. In the figure, the same reference numerals as those of the electrical connection diagram of the electromagnetic induction heating cooker of the present invention shown in FIG. 1 perform the same operation, and therefore the description thereof will be omitted and different operations will be described.
[0031]
The current-corresponding pan detection control circuit is formed by a current holding circuit EP, a third comparison circuit CP3, and an AND circuit AND.
[0032]
The current holding circuit EP shown in FIG. 5 performs a peak hold operation including a double-wave rectifier circuit WD, an amplifier circuit OP, a diode DR2, a capacitor C4, and a resistor R1. The double-wave rectifier circuit WD performs double-wave rectification on the output current detection signal Ct2. The current holding circuit EP holds the highest signal value of the input signal at both ends of the capacitor C4, and discharges the charge of the capacitor C4 for a predetermined time by the return resistor R1.
[0033]
FIG. 6 is a waveform chart for explaining the operation of the second embodiment. 6A shows the output voltage detection signal Cv2, and FIG. 6B shows the output current detection signal Ct2 when the pot PB is placed or not placed. 6 (C) shows the pulse signal Pk when the pot PB is not placed, and FIG. 6 (D) shows the pulse signal Pk when the pot PB is placed. E) shows the phase difference detection signal Pd when the pot PB is placed or not placed, and FIG. 6E shows when the pot PB is placed or placed. The current holding signal Ep when there is no current is shown.
[0034]
First, when the value of the power setting signal Pc is set to the normally used power and heating is performed without the pan, the pan detection circuit uses the phase difference / voltage conversion circuit PE to output the phase difference shown in FIG. Detect θ. At this time, the value of the phase difference θ increases, and the phase difference θ is converted into a voltage and output as a phase difference detection signal Pd shown in FIG. The comparison circuit CP compares the phase difference detection signal Pd with the phase difference discrimination signal Pr, determines that the phase difference detection signal Pd is larger than the phase difference discrimination signal Pr, determines that there is no pan, and generates the pan no detection signal Cp. High level is output to the AND circuit AND.
[0035]
The current holding circuit EP of the current-capable pot detection control circuit holds the peak current of the output current detection signal Ct2 and outputs the current holding signal Ep shown in FIG. At this time, when the power setting signal Pc is set to the power to be used normally and heating is performed without the pan, a current flows through the induction heating coil HL, and the current holding signal Ep is a current determination signal as shown in FIG. The third comparison circuit CP3 sets the pan detection control signal Cp3 to High level and outputs the signal to the AND circuit AND. The AND circuit AND sets the output signal to the high level because the pan detection control signal Cp3 and the pan non-detection signal Cp are at the high level, and stops the operation of the inverter drive circuit SD.
[0036]
When the value of the power setting signal Pc is set to the power to be used normally and heating is performed in the state with the pan, the value of the phase difference θ becomes small. The comparison circuit CP compares the phase difference detection signal Pd with the phase difference determination signal Pr, determines that the phase difference detection signal Pd is smaller than the phase difference determination signal Pr, determines that there is a pan, and sets the pan non-detection signal Cp to the low level. And outputs it to the AND circuit AND. When the pan absence detection signal Cp goes to a low level, the AND circuit AND sets the output to a low level irrespective of the pan detection control signal Cp3 to operate the inverter drive circuit SD.
[0037]
When the value of the power setting signal Pc is set to the minimum power consumption, the current corresponding pan detection control circuit reduces the current flowing through the induction heating coil HL, and the current holding signal Ep becomes the current discrimination signal as shown in FIG. Fr becomes smaller than Fr, and the third comparison circuit CP sets the pan detection control signal Cp3 to Low level and outputs it to the AND circuit AND. When the pan detection control signal Cp3 becomes low level, the AND circuit AND sets the output signal to low level regardless of the pan non-detection signal Cp to operate the inverter drive circuit SD.
[0038]
[Example 3]
FIG. 7 is an electrical connection diagram of the electromagnetic induction heating cooker according to the third embodiment. In the figure, the same reference numerals as those of the electrical connection diagram of the electromagnetic induction heating cooker of the present invention shown in FIG. 1 perform the same operation, and therefore the description thereof will be omitted and different operations will be described.
[0039]
The electric power corresponding pan detection control circuit is formed by the fourth comparison circuit CP4 and the AND circuit AND.
[0040]
The fourth comparison circuit CP4 compares the power setting signal Pc with the power discrimination signal Pf and outputs a pan detection control signal Cp4.
[0041]
When the value of the power setting signal Pc is set to the power normally used, the power setting signal Pc becomes larger than the power determination signal Pf, and the fourth comparison circuit CP4 of the power corresponding pot detection control circuit sets The pan detection control signal is set to a high level and output to the AND circuit AND. Therefore, the AND circuit AND sets the output signal to the high level when the panless detection signal Cp goes to the high level, and stops the inverter drive circuit SD.
[0042]
When the value of the power setting signal Pc is set to the minimum used power, the power setting signal Pc becomes smaller than the power discrimination signal Pf, and the fourth comparison circuit CP4 of the power corresponding pot detection control circuit sets the pot detection control signal Cp4 to Low level. Is output to the AND circuit AND. When the pan detection control signal Cp goes low, the output signal goes low, regardless of the pan non-detection signal Cp, and the AND circuit AND operates the inverter drive circuit SD.
[0043]
When the output signal of the AND circuit AND becomes High level and the inverter driving circuit SD is stopped, the indicator LED is turned on to display the panless state.
【The invention's effect】
In the electromagnetic induction heating cooker according to the present invention, the cooking operation can be continued without stopping the inverter circuit, in which the operation of the pot detection circuit is automatically stopped when cooking is performed with the power set value set small. Further, it is possible to solve the problem that a small pot is determined to be no pot due to a difference in the diameter of the pot.
[Brief description of the drawings]
FIG. 1 is an electrical connection diagram of the electromagnetic induction heating cooker of the present invention.
FIG. 2 is a detailed connection diagram of the phase difference detection circuit shown in FIG.
FIG. 3 is a waveform diagram illustrating the operation of the present invention.
FIG. 4 is an electrical connection diagram of the electromagnetic induction heating cooker according to the second embodiment.
FIG. 5 is a detailed connection diagram of the current holding circuit shown in FIG.
FIG. 6 is a waveform chart for explaining the operation of the second embodiment.
FIG. 7 is an electrical connection diagram of the electromagnetic induction heating cooker according to the third embodiment.
FIG. 8 is an electrical connection diagram of a conventional electromagnetic induction heating cooker.
[Explanation of symbols]
AND AND circuit CO Differential amplifier circuit CP Comparison circuit C1 Smoothing capacitor C2 Resonance capacitor C3 Resonance capacitor C4 Capacitor CP2 Second comparison circuit CP3 Third comparison circuit CP4 Fourth comparison circuit CT2 Output current detection circuit CV2 Output voltage detection circuit DR1 Rectifier circuit DR2 Diode EP Current holding circuit FV Frequency / voltage conversion circuit HL Induction heating coil ID Input current detection circuit IV Input voltage detection circuit LED Display OA Operation panel OP Amplification circuit PB Pot PC Power setting circuit PD Phase difference detection circuit PE Phase difference / voltage conversion circuit PK Pulsing circuit PL Top plate R1 Resistor SA Power calculation circuit SC Control calculation circuit SD Inverter drive circuit TS Heating switch TR1 Switching element TR2 Switching element WD Dual-wave rectification circuit Cp No-pan detection signal Cp2 Pan detection control signal Ct2 Output current detection signal Cv2 Output voltage detection signal Ep Current holding signal Er Current discrimination signal Fv Frequency / voltage conversion signal Fr Frequency discrimination signal Id Input current detection signal Iv Input voltage detection signal ΔI Differential amplification signal Ld Display signal Oa Operation signal Pc Power setting signal Pd Phase difference detection signal Pf Power discrimination signal Pk Pulse signal Pr Phase difference discrimination signal Sa Power calculation signal Sc Control calculation signal Ts Heating start signal Sd1 Switching element drive signal Sd2 Switching element drive signal Wd Dual wave rectification signal

Claims (4)

A resonance capacitor, an induction heating coil that forms a series resonance with the resonance capacitor, a rectification circuit that rectifies a commercial AC power supply and converts the DC voltage to a DC voltage, An inverter circuit that supplies a current, a power operation circuit that calculates an input power of the inverter circuit and outputs a power operation signal, a power setting circuit that outputs a predetermined power setting signal, the power operation signal and the power A differential amplifier circuit that differentially amplifies a setting signal, an inverter drive circuit that controls an output frequency of the inverter circuit according to the differential amplified signal, and a phase difference between an output voltage and an output current of the inverter circuit. A phase difference detection circuit for detecting and outputting a phase difference detection signal; and a pan mounted when a value of the phase difference detection signal is larger than a predetermined phase difference determination value. And a pan detection circuit that outputs a pan-no-detection signal to determine that the high-frequency current has not been supplied and stops the supply of the high-frequency current by outputting a pan-no-detection signal, and that is mounted on the induction heating coil. In an electromagnetic induction heating cooker that heats a pan by an electromagnetic induction effect, when the output frequency of the inverter circuit is higher than a predetermined frequency discrimination value, the operation of the pan detection circuit is stopped, and the output frequency is the frequency discrimination value. An electromagnetic induction heating cooker comprising a frequency-dependent pan detection control circuit for operating the pan detection circuit at a lower temperature. A current-corresponding pan detector that stops the operation of the pan detection circuit when the output current of the inverter circuit is smaller than a predetermined current discrimination value, and operates the pan detection circuit when the output current is larger than the current discrimination value. 2. The electromagnetic induction heating cooker according to claim 1, wherein a control circuit is replaced with said frequency-adaptive pan detection control circuit. The power corresponding pan detection control that stops the operation of the pan detection circuit when the power setting signal is smaller than a predetermined power discrimination value and operates the pan detection circuit when the power setting signal is larger than the power discrimination value. 2. The electromagnetic induction heating cooker according to claim 1, wherein the circuit is replaced with the frequency corresponding pan detection control circuit. 4. The electromagnetic induction according to claim 1, wherein a panless state is displayed by a display when a panless detection signal of the pan detection circuit is input to the inverter drive circuit. Heating cooker.

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