JP2007280897A - Electromagnetic induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to automatically establish a determination reference value of existence of a pot mounted on an electromagnetic induction heating cooker. <P>SOLUTION: The cooker comprises a power calculation circuit SA for calculating input power value; a control circuit SC which controls so that the power calculation value is nearly equal to the power set value; and a phase difference detection circuit PD, to detect the phase difference between the output voltage and output current, and a current-maintaining circuit EP for maintaining peak of the output current, and determines that there is no pot, when the phase difference detection value is larger than the phase reference value and the current maintaining value is larger than the current reference value. The cooker is equipped with a phase/current detection control circuit PE, which outputs a phase/current detection start signal, when a prescribed button OA is pushed after the pot PB is removed; a phase reference setting circuit PR which automatically sets the phase reference value, based on the phase difference detection value Pd, when the phase/current detection start signal is input; and a current reference setting circuit ER which automatically sets the current reference value, based on the current maintaining value Ep when the phase/current detection start signal is input. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnetic induction heating cooker that uses an inverter circuit to supply a high-frequency current to an induction heating coil to heat a cooking pan by electromagnetic induction, and is particularly mounted on a top plate on the upper surface of the induction heating coil. The present invention relates to a technique for determining the presence or absence of a pan.

  When the electromagnetic induction heating cooker is shipped from the factory, the operator confirms that the presence or absence of the pan is properly determined before shipping. However, there are many cases where a normal induction heating coil is replaced with another induction heating coil and used by changing the specification after shipment. At this time, the presence / absence of the pan may not be correctly determined due to the difference in the inductance value of the induction heating coil. Therefore, it is necessary to reset the determination reference value so that the operator can normally determine the presence or absence of the pan manually. Hereinafter, the electromagnetic induction heating cooker which can set the discrimination | determination reference value of a pan manually is demonstrated.

  FIG. 5 is an electrical connection diagram of a conventional electromagnetic induction heating cooker. In the figure, a rectifier circuit DR1 rectifies the output of a commercial AC power supply and converts it into a DC voltage, and a smoothing capacitor C1 smoothes the voltage converted into DC. 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.

  The switching element TR1 and the switching element TR2 are switching elements that form a half-bridge type inverter circuit, and 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 pan PB is placed on the induction heating coil HL and heated by electromagnetic induction.

  The inverter drive circuit SD performs PFM control that modulates the pulse frequency with a constant pulse width ratio according to the value of the control signal Sc from the control circuit SC, and alternately drives the switching element TR1 and the switching element TR2. The switching element drive signal Sd1 and the switching element drive signal Sd2 are output.

  The power calculation circuit SA inputs the input current detection signal Id and the input voltage detection signal Iv, calculates the input power of the inverter, and outputs it as a power calculation signal Sa. The power setting circuit PC sets a predetermined power setting value and outputs it as a power setting signal Pc.

  The differential amplifier circuit CO differentially amplifies the power setting signal Pc and the power calculation signal Sa, and outputs the value of the differential amplification signal ΔI. The control circuit SC starts operation when a heating start signal Ts is input from the heating switch TS, performs calculation according to the value of the differential amplification signal ΔI, and performs control processing when the value of the differential amplification signal ΔI is large. On the contrary, when the value of the signal Sc is decreased, the value of the control processing signal Sc is increased when the value of the differential amplification signal ΔI is small. Further, the phase setting value and the current setting value preset by the operation panel OA are output as the phase difference reference signal Pr and the current reference signal Er.

  When the value of the control signal Sc input from the control circuit SC is small, the inverter drive circuit SD increases the frequency of the PFM control to increase the impedance value of the resonant tank including the induction heating coil HL and the resonant capacitors C2 and C3. The current flowing through the induction heating coil HL is reduced. On the contrary, when the value of the control calculation 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.

  The phase difference detection circuit PD shown in FIG. 5 is formed by the pulsing circuit PK and the phase difference / voltage conversion circuit PV shown in FIG. 6, and the pulsing circuit PK detects the output current of FIG. 8B shown below. The positive time width of the signal Ct2 is converted into a pulse signal Pk shown in FIG. The output voltage detection circuit CV2 performs half-wave rectification on the AC output voltage of an inverter circuit (not shown) and outputs an output voltage detection signal Cv2 shown in FIG. The phase difference / voltage conversion circuit PV detects the phase difference θ between the pulse signal Pk and the output voltage detection signal Cv2, converts this phase difference θ into a voltage, and outputs it as a phase difference detection signal Pd. On the other hand, when the value of the phase difference θ is large, the output voltage becomes high. Conversely, when the value of the phase difference θ is small, the output voltage becomes small.

  The current holding circuit EP shown in FIG. 7 performs a peak hold operation constituted by the double-wave rectifier circuit WD, the amplifier circuit OP, the diode DR2, the capacitor C4, and the resistor R1. Both-wave rectifier circuit WD rectifies both-wave 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 by a predetermined time by the return resistor R1.

  The pan detection circuit is formed by the first comparison circuit CP, the second comparison circuit CP2, and the AND circuit AND. When the output signal Ad of the AND circuit AND becomes High level, it is determined that there is no pan, and the operation of the inverter drive circuit SD is performed. Stop.

  FIG. 8 is a waveform diagram for explaining the operation of the prior art. FIG. 8A shows the output voltage detection signal Cv2, and FIG. 8B shows when the pan PB is placed or placed. The output current detection signal Ct2 when the pan PB is not placed is shown, FIG. 5C shows the pulse signal Pk when the pan PB is not placed, and FIG. (E) shows the phase difference detection signal Pd when the pan PB is placed or not, and FIG. (F) shows the pan signal Pk when the pan PB is placed. Shows the current holding signal Ep when is mounted or not mounted.

  Next, the discrimination | determination operation | movement when the pan PB is not mounted in the induction heating coil HL using the waveform diagram shown in FIG. 8 is demonstrated. When the induction heating coil HL is heated without the pan, the phase difference / voltage conversion circuit PV detects the phase difference θ between the output voltage detection signal Cv2 in FIG. 8A and the pulse signal Pk in FIG. . At this time, the value of the phase difference θ increases when there is no pan, and the phase difference θ is converted into a voltage and output as a phase difference detection signal Pd shown in FIG. The first comparison circuit CP compares the phase difference detection signal Pd with a predetermined phase reference value Pr and determines that there is no pan when the phase difference detection signal Pd is greater than the phase reference value Pr. The comparison signal Cp is set to High level and output to the AND circuit AND.

  When the induction heating coil is replaced with another induction heating coil by changing the specification or the like and the induction heating coil HL is heated without a pan, for example, the position shown in FIG. The value of the phase difference θ decreases, and the value of the phase difference detection signal Pd shown in FIG. The first comparison circuit CP compares the phase difference detection signal Pd with the phase reference value Pr, and determines that there is a pan when the phase difference detection signal Pd is smaller than the phase reference value Pr, and can normally determine the presence or absence of a pan. Disappear. At this time, the operator operates the operation panel OA to reset the phase reference value Pr to a value at which the presence / absence of the pan can be normally determined. However, it takes time for the operator to find and set the optimum value of the phase reference value Pr.

  Similarly, due to the difference in the inductance value of the induction heating coil, for example, the output current detection signal Ct2 shown in FIG. 8B also becomes smaller, and the current holding signal shown in FIG. 8F corresponds to the output current detection signal Ct2. The value of Ep also decreases. The second comparison circuit CP2 compares the current holding signal Ep with a predetermined current reference value Er and determines that there is a pan when the current holding signal Ed is smaller than the current reference value Er, and normally determines whether there is a pan. become unable. Also at this time, the operator operates the operation panel to reset the value of the current reference value Er to a value at which the presence / absence of the pan can be normally determined. However, it takes time for the operator to find the optimum value of the current reference value Er.

  As described above, in the prior art, when the induction heating coil is replaced with another induction heating coil by using a specification change after shipment, the operator needs to manually reset the discrimination reference value of the pan. . In addition, a large set time is required to manually reset the two parameters of the phase reference signal Pr and the current reference signal Er. (For example, Patent Document 1)

JP 2004-253297 A

  The electromagnetic induction heating cooker is shipped after confirming that the operator can normally determine the presence or absence of the pan at the time of factory shipment. However, in response to changes in the environment actually used after shipment, the standard induction heating coil installed at the time of shipment from the factory is often replaced with another induction heating coil. At this time, the presence or absence of the pan may not be normally determined due to the difference in the inductance value of the induction heating coil. Therefore, the operator manually resets the discrimination reference value so that the presence or absence of the pan can be discriminated normally.

  However, there are two reference values (phase reference value and current reference value) for the discrimination reference value, and it is foreseeable how much it will increase or decrease even if the operator manually resets the two reference values. It is very difficult to do so, and it takes a long time to reset the two reference values by cut-and-try. In addition, the discrimination reference value to be set manually is obtained by first obtaining a discrimination reference value for discriminating that there is no pan in a state where no pan is placed on the induction heating coil, and placing the pan on the induction heating coil, There is a problem in the accuracy of the discrimination reference value because a complicated operation is required to manually obtain the discrimination reference value for discriminating that there is a pan with the set value being minimized.

  Then, this invention is providing the electromagnetic induction heating cooking appliance which can solve the subject mentioned above.

  In order to solve the above-described problem, a first invention includes a resonance capacitor, an induction heating coil that forms a series resonance circuit with the resonance capacitor, an inverter circuit that supplies a high-frequency current to the induction heating coil, A power calculation circuit that calculates an input power value of the inverter circuit and outputs it as a power calculation signal, a power setting circuit that sets a predetermined input power value and outputs it as a power setting signal, and the value of the power calculation signal is A control circuit that controls the output frequency of the inverter circuit so as to be substantially equal to the value of the power setting signal, and a phase difference that detects a phase difference between the output voltage and output current of the inverter circuit and outputs a phase difference detection signal The detection circuit, the current holding circuit that detects the peak value of the output current of the inverter circuit and outputs it as a current holding signal, and the value of the phase difference detection signal A pan detecting circuit for detecting that no pan is placed on the induction heating coil when the current holding signal is larger than a reference value and the value of the current holding signal is larger than the current reference value, and stopping the inverter circuit. In an electromagnetic induction heating cooker, when the pan is not placed on the induction heating coil and the predetermined button on the operation panel is pressed, the inverter circuit is driven and the phase / current detection start signal is output. A detection control circuit; a phase reference setting circuit that automatically sets the phase reference value based on the value of the phase difference detection signal when the phase / current detection start signal is input; and the current reference value is set to the phase / current An electromagnetic induction heating cooker comprising: a current reference setting circuit that automatically sets based on the value of the current holding signal when a detection start signal is input A.

  According to a second aspect of the present invention, a resonance capacitor, an induction heating coil that forms a series resonance circuit with the resonance capacitor, an inverter circuit that supplies a high-frequency current to the induction heating coil, and an input power value of the inverter circuit are calculated. A power calculation circuit that outputs as a power calculation signal, a power setting circuit that sets a predetermined input power value and outputs it as a power setting signal, and the value of the power calculation signal is substantially equal to the value of the power setting signal A control circuit for controlling the output frequency of the inverter circuit, a phase difference detection circuit for detecting a phase difference between the output voltage and output current of the inverter circuit and outputting a phase difference detection signal, and an output of the inverter circuit A frequency detection circuit that detects the frequency and outputs it as a frequency detection signal; and when the value of the phase difference detection signal is greater than a phase reference value and the frequency An electromagnetic induction heating cooker comprising: a pan detection circuit that detects that a pan is not placed on the induction heating coil when a value of a detection signal is greater than a frequency reference value, and stops the inverter circuit. Is not placed on the induction heating coil, and when a predetermined button on the operation panel is pressed, the inverter circuit is driven and a phase / frequency detection start signal is output, and the phase reference is output. When the phase / current detection start signal is input, a phase reference setting circuit that automatically sets the value based on the value of the phase difference detection signal, and when the phase / frequency detection start signal is input as the frequency reference value An electromagnetic induction heating cooker comprising: a frequency reference setting circuit that automatically sets based on the value of the frequency detection signal.

  According to the first invention, when the induction heating coil of the electromagnetic induction heating cooker is used by replacing it with another induction heating coil, two discrimination reference values for presence / absence of a pan caused by a difference in inductance value of the induction heating coil are used. Since the resetting of the (phase reference value and current reference value) can be automatically set, the operator can reset the discrimination reference value manually, and the time can be greatly reduced, and the working efficiency is improved. In addition, the operator obtains two discrimination reference values manually by cut-and-try, whereas the two discrimination reference values (phase reference value and current reference value) obtained by automatic setting are much more accurate. It will lead to better product quality.

  According to the second aspect of the invention, since the reference value (phase reference value and frequency reference value) for determining the presence / absence of the pan caused by the difference in inductance of the induction heating coil can be automatically set as described above, work efficiency is improved. . Furthermore, the operator obtains two discrimination reference values manually by cut and try, whereas the two discrimination reference values (phase reference value and frequency reference value) obtained by automatic setting are far more accurate. It will lead to better product quality.

[Embodiment 1]
FIG. 1 is an electrical connection diagram of an electromagnetic induction heating cooker according to Embodiment 1 of the present invention. In the figure, components having the same reference numerals as those in the electrical connection diagram of the prior art inverter device shown in FIG.

  The phase / current detection control circuit PE selects the phase / current detection start signal Pe according to the selection signal Os corresponding to the panless detection adjustment mode 1 or the panless detection adjustment mode 2 selected by pressing a predetermined button on the operation panel OA. And the inverter drive signal Pi are output. At this time, when mode 1 is selected, the phase / current detection start signal Pe outputs a one-pulse signal, and when mode 2 is selected, a two-pulse signal is output. The inverter drive signal Pi is continuously output for a predetermined time (for example, about 8 seconds) from when the selection signal Os is input to the phase / current detection control circuit PE.

  The phase reference setting circuit PR starts its operation when a predetermined phase correction reference value ΔP is prepared and a one-pulse phase / current detection start signal Pe (panless detection adjustment mode 1) is input. Continue operation for a time (eg, about 8 seconds). Subsequently, based on the value of the phase difference detection signal Pd, the phase reference value Pr is calculated from the phase difference detection signal Pd−phase correction reference value ΔP and automatically set. When a two-pulse phase / current detection start signal Pe (no pan detection adjustment mode 2) is input, a phase reference value is obtained from the phase difference detection signal Pd + phase correction reference value ΔP based on the value of the phase difference detection signal Pd. Pr is calculated and automatically set.

  The current reference setting circuit ER starts operation when a predetermined current correction reference value ΔE is prepared and a one-pulse phase / current detection start signal Pe (no pan detection adjustment mode 1) is input. Continue operation for a time (eg, about 8 seconds). Subsequently, based on the value of the current holding signal Ep, the current reference value Er is calculated from the current holding signal Ep−the current correction reference value ΔE and automatically set. Further, when a two-pulse phase / current detection start signal Pe (no pan detection adjustment mode 2) is input, the current reference value Er is obtained from the current holding signal Ep + current correction reference value ΔE based on the value of the current holding signal Ep. Calculated and automatically set.

  2A and 2B are waveform diagrams for explaining the operation of the first embodiment. FIG. 2A shows a phase / current detection start signal Pe, FIG. 2B shows an inverter drive signal Pi, and FIG. (C) shows the phase difference detection signal Pd when the pan PB is not placed, and FIG. 4D shows the current holding signal Ep when the pan PB is not placed.

  Next, setting of the phase reference value and the current reference value when the induction heating coil HL is replaced with another induction heating coil HL by changing the specification after shipment will be described with reference to the waveform diagram of FIG.

  At time t = t1 shown in FIG. 2, the phase reference setting circuit PR and the current reference setting circuit ER hold the phase reference value Pr and the current reference value Er set before the induction heating coil HL is replaced.

  At time t = t2, when the operator selects the panless detection adjustment mode 1 by pressing a predetermined button on the operation panel OA, the phase / current detection control circuit PE outputs the inverter drive signal Pi shown in FIG. 2 (B). Also, a one-pulse phase / current detection start signal Pe shown in FIG.

  When a one-pulse phase / current detection start signal Pe is input to the phase reference setting circuit PR at time t = t2, the phase reference value Pr held before time t = t2 is initialized. Subsequently, the inverter circuit starts operating in response to the inverter drive signal Pi, and starts reading the value of the phase difference detection signal Pd detected by the phase difference detection circuit PD. Similarly, when a one-pulse phase / current detection start signal Pe is input to the current reference setting circuit ER, the current reference value Er held before time t = t2 is initialized. Subsequently, reading of the value of the current holding signal Ep detected by the current holding circuit EP is started.

  The period from time t = t2 to t3 is an excessive period of the phase difference detection signal Pd, and the value of the phase difference detection signal Pd increases. Subsequently, the phase reference setting circuit PR calculates the phase reference value Pr from the phase difference detection signal Pd−phase correction reference value ΔP based on the stable phase difference detection signal Pd after time t = t4. Similarly, the current reference setting circuit ER calculates the current reference value Er from the current holding signal Ep−the current correction reference value ΔE based on the stable current holding signal Ep after time t = t4.

  At time t = t5, the phase reference setting circuit PR ends the operation time (for example, about 8 seconds), and determines the phase reference value Pr automatically set by the phase difference detection signal Pd−phase correction reference value ΔP. Hold. Similarly, the current reference setting circuit ER ends the operation time (for example, about 8 seconds), and determines and holds the current reference value Er automatically set by the current holding signal Ep−current correction reference value ΔE. Subsequently, when the output time (for example, about 8 seconds) of the inverter drive signal Pi shown in FIG. 2B ends at time t = t6, the operation of the inverter circuit is stopped. Thereafter, the operator presses the predetermined button on the operation panel OA again to return to the normal cooking mode.

  From the above, even if the induction heating coil of the electromagnetic induction heating cooker is replaced with another induction heating coil, the optimum phase reference value and current reference value can be easily set automatically, so that the working efficiency is greatly improved.

  Next, the setting of the phase reference value and the current reference value for enabling heating of a special pan (for example, a pan having a very small diameter) that is discriminated as having no pan in spite of the pan present state will be described. .

  A special pan to be heated is placed on the induction heating coil HL, and the operator presses a predetermined button on the operation panel OA to select the no pan detection adjustment mode 2. At this time, when mode 2 is selected, the phase / current detection start signal Pe becomes a two-pulse signal (not shown). When a two-pulse phase / current detection start signal Pe is input, the phase reference setting circuit PR discriminates the panless detection adjustment mode 2, and based on the value of the phase difference detection signal Pd, the phase difference detection signal Pd + phase correction The phase reference value Pr is automatically set by calculating from the reference value ΔP. At this time, the value of the phase reference value Pr increases and it can be determined that the pan is present.

  When the two-pulse phase / current detection start signal Pe is input, the current reference setting circuit ER discriminates the panless detection adjustment mode 2, and based on the value of the current holding signal Ep, the current holding signal Ep + current correction reference value The current reference value Er is automatically set by calculating from ΔE. At this time, the value of the current reference value Er increases and it can be determined that the pan is present. Thereafter, since the same operation as the above-described no pan detection adjustment mode 1 is performed, the description is omitted.

[Embodiment 2]
FIG. 3 is an electrical connection diagram of the electromagnetic induction heating cooker according to the second embodiment of the present invention. In the figure, the components having the same reference numerals as those in the electric connection diagram of the prior art inverter device shown in FIG. 5 and the electric connection diagram of the electromagnetic induction heating cooker in the first embodiment shown in FIG. Only components that are omitted and different in reference numeral will be described.

  In the second embodiment, the presence / absence of the pan is determined based on the comparison between the current holding signal Ed and the current reference signal Er in the first embodiment, whereas the comparison between the frequency detection signal Fv and the frequency reference value Fr is performed. Based on the above, the presence or absence of a pan is determined.

  A predetermined button on the operation panel OA is pressed to select the no pan detection adjustment mode 1 or the no pan detection adjustment mode 2. The phase / frequency detection control circuit PF outputs a phase / frequency detection start signal Pf and an inverter drive signal Pi in response to the selection signal Os from the operation panel OA. At this time, when mode 1 is selected, the phase / frequency detection start signal Pf outputs a one-pulse signal, and when mode 2 is selected, a two-pulse signal is output. The inverter drive signal Pi is continuously output for a predetermined time (for example, about 8 seconds) from when the selection signal Os is input to the phase / frequency detection control circuit PF.

  The frequency detection circuit FV converts the frequency of the output voltage detection signal Cv2 output from the output voltage detection circuit CV2 into a voltage and outputs the voltage as a frequency detection signal Fv. In addition, the current holding signal Ep and the phase difference detection signal Pd increase in signal voltage when the current and the phase difference are large, respectively, whereas the frequency detection signal Fv becomes lower voltage as the frequency is higher.

  The frequency reference setting circuit FR is prepared based on the value of the frequency detection signal Fv when a predetermined frequency correction reference value ΔF is prepared and a one-pulse phase / frequency detection start signal Pf (panless detection adjustment mode 1) is input. Thus, the frequency reference value Fr is calculated from the frequency detection signal Fv−frequency correction reference value ΔF and automatically set. When a two-pulse phase / frequency detection start signal Pf (no pan detection adjustment mode 2) is input, a frequency reference value is calculated from the frequency detection signal Fv + frequency correction reference value ΔF and automatically set.

  FIG. 4 is a waveform diagram for explaining the operation of the second embodiment. (A) shows the phase / frequency detection start signal Pf, (B) shows the inverter drive signal Pi, and (C) shows the phase difference detection when the pan PB is not placed. The signal Pd is shown, and FIG. 4D shows the frequency detection signal Fv when the pan PB is not placed.

  Next, setting of the phase reference value and the frequency reference value when the induction heating coil HL is replaced with another induction heating coil HL by changing the specification after shipment will be described with reference to the waveform diagram of FIG.

  At time t = t1 shown in FIG. 4, the phase reference setting circuit PR and the frequency reference setting circuit FR hold the phase reference value Pr and the frequency reference value Fr that are set before the induction heating coil HL is replaced.

  At time t = t2, when an operator selects a panless detection adjustment mode 1 by pressing a predetermined button on the operation panel OA, the phase / frequency detection control circuit PF outputs an inverter drive signal Pi shown in FIG. 4B. Also, a one-pulse phase / frequency detection start signal Pf shown in FIG.

  When a one-pulse phase / frequency detection start signal Pf is input to the phase reference setting circuit PR at time t = t2, the phase reference value Pr held before time t = t2 is initialized. Subsequently, reading of the value of the phase difference detection signal Pd detected by the phase difference detection circuit PD is started. Similarly, when the one-pulse phase / frequency detection start signal Pf is input to the frequency reference setting circuit FR, the frequency reference value Fr held before time t = t2 is initialized. Subsequently, reading of the value of the frequency detection signal Fv detected by the frequency detection circuit FV is started.

  The frequency reference setting circuit FR calculates the frequency reference value Fr from the frequency detection signal Fv−the frequency correction reference value ΔF based on the stable frequency detection signal Fv after time t = t4.

  At time t = t5, the frequency reference setting circuit FR ends the operation time (for example, about 8 seconds), and determines and holds the frequency reference value Fr automatically set by the frequency detection signal Fv−frequency correction reference value ΔF. To do. As described above, even if the induction heating coil of the electromagnetic induction heating cooker is replaced with another induction heating coil, the optimum phase reference value and frequency reference value can be easily set automatically, so that the work efficiency is greatly improved. Furthermore, the discrimination reference value obtained by automatic setting is far more accurate than the discrimination reference value obtained by the operator manually by cutting and trying, and the product quality is improved.

It is an electrical connection figure of the electromagnetic induction heating cooking appliance which concerns on Embodiment 1 of this invention. It is a wave form diagram explaining operation | movement of the electromagnetic induction heating cooking appliance which concerns on Embodiment 1. FIG. It is an electrical connection figure of the electromagnetic induction heating cooking appliance which concerns on Embodiment 2 of this invention. It is a wave form diagram explaining operation | movement of the electromagnetic induction heating cooking appliance which concerns on Embodiment 2. FIG. It is an electrical connection figure of the electromagnetic induction heating cooking appliance of a prior art. FIG. 6 is a detailed diagram of the phase difference detection circuit shown in FIG. 5. FIG. 6 is a detailed diagram of the current holding circuit shown in FIG. 5. It is a wave form diagram explaining operation | movement of the electromagnetic induction heating cooking appliance of a prior art.

Explanation of symbols

AND AND circuit CO differential amplifier circuit CP first comparison circuit C1 smoothing capacitor C2 resonance capacitor C3 resonance capacitor C4 capacitor CP2 second comparison circuit CT2 output current detection circuit Ct2 output current detection signal CV2 output voltage detection circuit Cv2 output voltage detection Signal DR1 Rectifier circuit DR2 Diode EP Current holding circuit Ep Current holding signal ER Current reference setting circuit Er Current reference setting signal (Current reference value)
FR frequency reference setting circuit FR frequency reference setting signal (frequency reference value)
FV Frequency / voltage conversion circuit Fv Frequency detection signal HL Induction heating coil ID Input current detection circuit Id Input current detection signal IV Input voltage detection circuit Iv Input voltage detection signal ΔI Differential amplification signal LED display OA Operation panel OP Amplification circuit PB Pan PC power setting circuit Pc power setting signal PD phase difference detection circuit Pd phase difference detection signal PE phase / current detection control circuit Pe phase / current detection control signal PF phase / frequency detection control circuit Pf phase / frequency detection control signal PV phase difference / Voltage conversion circuit PK Pulse circuit PL Top plate PR Phase reference setting circuit Pr Phase reference setting signal (phase reference value)
Pi Inverter drive signal R1 Resistor SA Power operation circuit Sa Power operation signal SC Control circuit Sc Control signal SD Inverter drive circuit Sd1 Switching element drive signal Sd2 Switching element drive signal TS Heating switch Ts Heating start signal TR1 Switching element TR2 Switching element WD Both Wave rectifier circuit

Claims (2)

  A resonance capacitor, an induction heating coil that forms a series resonance circuit with the resonance capacitor, an inverter circuit that supplies high-frequency current to the induction heating coil, and an input power value of the inverter circuit is calculated and output as a power calculation signal A power setting circuit that sets a predetermined input power value and outputs it as a power setting signal, and that the value of the power calculation signal is substantially equal to the value of the power setting signal. A control circuit that controls the output frequency, a phase difference detection circuit that detects a phase difference between the output voltage and output current of the inverter circuit and outputs a phase difference detection signal, and a peak value of the output current of the inverter circuit A current holding circuit that outputs the current holding signal, and when the value of the phase difference detection signal is larger than a phase reference value and the current holding signal In an electromagnetic induction heating cooker comprising a pan detection circuit for detecting that no pan is placed on the induction heating coil when the current is greater than a current reference value, and stopping the inverter circuit, the pan is the induction heating A phase / current detection control circuit that drives the inverter circuit and outputs a phase / current detection start signal when a predetermined button on the operation panel is pressed after being placed on the coil, and the phase reference value is set to the phase A phase reference setting circuit that automatically sets the current detection start signal based on the value of the phase difference detection signal; and the current holding signal that receives the current reference value as the phase / current detection start signal. An electromagnetic induction heating cooker comprising: a current reference setting circuit that automatically sets based on the value of. A resonance capacitor, an induction heating coil that forms a series resonance circuit with the resonance capacitor, an inverter circuit that supplies high-frequency current to the induction heating coil, and an input power value of the inverter circuit is calculated and output as a power calculation signal A power setting circuit that sets a predetermined input power value and outputs it as a power setting signal, and that the value of the power calculation signal is substantially equal to the value of the power setting signal. A control circuit for controlling the output frequency, a phase difference detection circuit for detecting a phase difference between the output voltage and output current of the inverter circuit and outputting a phase difference detection signal, and a frequency for detecting the output frequency of the inverter circuit A frequency detection circuit that outputs a detection signal; and a value of the frequency detection signal when a value of the phase difference detection signal is greater than a phase reference value An electromagnetic induction heating cooker comprising a pan detection circuit that detects that a pan is not placed on the induction heating coil when the frequency is greater than a frequency reference value, and stops the inverter circuit, wherein the pan is the induction heating coil A phase / frequency detection control circuit that drives the inverter circuit and outputs a phase / frequency detection start signal when a predetermined button on the operation panel is pressed after the state is not placed on the control panel; and A phase reference setting circuit that automatically sets a current detection start signal based on the value of the phase difference detection signal, and a frequency reference value of the frequency detection signal when the phase / frequency detection start signal is input. An electromagnetic induction heating cooker comprising: a frequency reference setting circuit that automatically sets based on a value.

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