JP2007294343A - Electromagnetic induction heating control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic induction heating control device capable of performing a stable return operation and a starting operation from a memorized control process. <P>SOLUTION: An induction heating control circuit 9, when power supply is input, reads out a memory control process step stored in a nonvolatile memory 10, and establishes this as a step number of a control process to implement this. A processing corresponding to each control process step is carried out, and when the process of that step is completed, the control process step is changed, and the present control process step is stored in the nonvolatile memory 10 as a memory control process step. Even during the time any of processing from the control process steps "0"-"3" is being carried out, power failure or the like occurs and the induction heating control circuit 9 is initialized, when the power supply is returned and the program is started again, operation can be started again from the process step before the power failure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electromagnetic induction heating control apparatus that controls a heating means that generates a high-frequency magnetic field to electromagnetically heat a load.

  An electromagnetic induction heating apparatus such as an electromagnetic cooker is equipped with an electromagnetic induction heating control apparatus that advances cooking by changing the heating output from the electromagnetic induction heating means according to a predetermined control process. In the electromagnetic induction heating control device, when a voltage drop or power failure occurs before the control process is completed, the volatile work memory is initialized, and when the power is restored, the control process is started from the beginning. I had to start over. In order to avoid this, Patent Document 1 discloses an induction heating cooker configured to store a control state in a storage unit at the time of a voltage drop or a power failure.

Further, in an electromagnetic induction heating device (for example, Patent Document 2) that heats a member to be heated by electromagnetic induction heating means, energization to the electromagnetic induction heating means is switched when a zero cross of a power source is detected.
Japanese Patent Laying-Open No. 2005-50725 JP 2004-22501 A

  However, when the power is low or when a power failure occurs, the power supply is unstable and the control status may not be stored in the storage means. There is a risk that it will be impossible.

  Further, when the heating elements are alternately heated by the electromagnetic induction heating means, the smoothing time constant of the input current detection circuit is designed to be sufficiently longer than the power supply period in order to stably take in the input current from the power supply. For this reason, since it took time to respond to the change in the input current, while the one heating element was heated, the other heating element was cooled, and it was difficult to make the temperature distribution uniform. .

  In view of the above problems, it is a first object of the present invention to provide an electromagnetic induction heating control device that can perform a stable return operation and can start the operation from a stored control process.

  It is a second object of the present invention to provide an electromagnetic induction heating control device that can energize a plurality of heating means in order to make the temperature distribution of the heating element uniform.

  In the electromagnetic induction heating control apparatus according to the first aspect of the present invention, when the control process changes, information necessary for resuming the control process before the operation stop when returning from the operation stop due to the voltage drop is stored in a nonvolatile manner. By storing the information in the means, necessary information can be reliably held when the voltage is normal, and a stable power failure recovery operation can be performed.

  In the electromagnetic induction heating control apparatus according to the second aspect of the present invention, when the voltage becomes unstable, the heating output of the heating means is stopped, and based on the information stored in the storage means when the voltage returns to the normal state. By performing the control, the operation can be resumed from the step before the voltage drop.

  In the electromagnetic induction heating control apparatus according to the third aspect of the present invention, since the waveform indicating the change in current is taken into the control means without being smoothed, the change in the current can be detected at high speed, and a plurality of heating means can be detected in a short time. Can be sequentially energized.

  According to claim 1 of the present invention, it is possible to provide an electromagnetic induction heating control device capable of performing a stable return operation and starting operation from a stored control process.

  According to claim 2 of the present invention, operation can be resumed from the step before the voltage drop even if the voltage is temporarily lowered.

  According to the third aspect of the present invention, it is possible to make the temperature distribution of the heated member uniform by improving the responsiveness to the current and controlling the energization of the plurality of heating means during a predetermined period of the power supply cycle. An electromagnetic induction heating control device can be provided.

  Hereinafter, preferred embodiments of an electromagnetic induction heating control apparatus according to the present invention will be described with reference to the accompanying drawings.

  The electrical configuration in the first embodiment will be described with reference to FIG. 1. 1 is a commercial power source of, for example, AC 100V, and 2 is a diode bridge that converts AC power from the commercial power source 1 serving as AC power into DC input power. 2a and a smoothing capacitor 2b. The DC input power from the rectifying and smoothing circuit 2 is supplied to a series circuit of a resonance capacitor 8 and a switching element 4 incorporating a reverse diode. Reference numeral 3 denotes an induction heating coil as a heating means, and the induction heating coil 3 is connected in parallel with the resonance capacitor 8. A series circuit of the switching element 4 and a circuit in which the resonance capacitor 8 is connected in parallel to the induction heating coil 3 corresponds to an inverter circuit that converts the DC input power into high-frequency power. Then, the switching element 4 is switched by a pulse drive signal supplied to the gate of the switching element 4 to cause resonance between the induction heating coil 3 and the resonance capacitor 8, thereby allowing a high frequency current to flow through the induction heating coil 3. It is configured as follows.

  As power feedback control means for outputting the induction heating coil 3 at a desired set power, an input voltage detection means 6 for detecting an input voltage (power supply voltage) supplied from the commercial power supply 1 to the inverter circuit, and a commercial power supply 1 based on the detection result obtained by the input current detection means 7 for detecting the input current supplied from 1 to the inverter circuit and the input voltage detection means 6 and the input current detection means 7, that is, An induction heating control circuit 9 is provided as heating control means comprising, for example, a microcomputer for variably controlling the ON time. 10 is a nonvolatile memory such as EEPROM, and 11 is a signal input means for operating the induction heating control circuit 9 with arbitrary power by inputting operation instructions such as operation start, stop, and heating control process. The induction heating control circuit 9 is electrically connected. Reference numeral 5 denotes a heated member made of a magnetic material that generates heat by a high-frequency magnetic field generated from the induction heating coil 3.

  Next, the effect | action is demonstrated about the said structure. The rectifying and smoothing circuit 2 converts AC power supplied from the commercial power source 1 into DC input power, and supplies this DC input power to the induction heating coil 3. The induction heating control circuit 9 switches the switching element 4 at a timing at which resonance occurs between the resonance capacitor 8 and the induction heating coil 3 that forms a parallel circuit with the resonance capacitor 8. As a result, a high-frequency current is supplied to the induction heating coil 3, an alternating magnetic field is generated from the induction heating coil 3, and the heated member 5 placed in the vicinity of the induction heating coil 3 is heated by electromagnetic induction.

  The induction heating control circuit 9 is input from the input voltage and input current respectively input from the input voltage detection means 6 and the input current detection means 7 so as to perform heating control in accordance with the operation instruction input from the signal input means 11. The power is calculated, and the constant power control is performed by changing the ON time of the switching element 4 so as to obtain a predetermined input power. That is, the induction heating control circuit 9 feeds back and feeds back the DC input power at regular intervals based on the detection outputs respectively input from the input voltage detection means 6 and the input current detection means 7. The DC input power is compared with the set power, and the heating power output of the induction heating coil 3 is updated so as to approach the set power. Thereby, the current flowing through the induction heating coil 3 and the induction heating power supplied to the member to be heated 5 are controlled so that the amount of heating to the member to be heated 5 becomes a desired value, and induction heating control is performed.

  Hereinafter, the operation of the induction heating control circuit 9 will be described in more detail. FIG. 2 is a flowchart showing the control data storage process of the induction heating control circuit 9 in the first embodiment. The induction heating control circuit 9 is pre-installed with an induction heating control pattern corresponding to each step of the control process, and the control process executed here completes a series of processes up to three steps.

  When the power is turned on, the induction heating control circuit 9 reads out the memory control process steps stored in the nonvolatile memory 10 and sets it as the number of steps of the control process for executing this (step S1). If the control process step is “0”, the ON signal of the signal input means 11 (operation start switch) is discriminated, and if it is ON, the control process step is changed to “1” (steps S2 to S4). The current control state such as a process step is stored in the nonvolatile memory 10 as a memory control process step corresponding to information such as control data. In the case of this figure, the memory control step “1” is stored in the nonvolatile memory 10 (step S5). If the control process step is not “0” but “1”, the induction heating control process corresponding to the control process step “1” is executed, and the control process step is set to “2” when the process of the step is completed. The memory control process step “2” is stored in the nonvolatile memory 10 (steps S2, S7 to S10). If the control process step is “2”, the induction heating control process corresponding to the control process step “2” is executed, and the control process step is changed to “3” when the process of the control process step “2” is completed. Then, the memory control process step “3” is stored in the nonvolatile memory 10 (steps S11 to S15). If the control process step is “3”, the induction heating control process corresponding to the control process step “3” is executed, and the control process step is reset to “0” when the control process step “3” is completed. (Initialization), the memory control step “0” is stored in the nonvolatile memory 10, and the operation is stopped (steps S11, S16 to S20).

  Even when a power failure occurs during execution of any one of the control process steps “0” to “3” and the induction heating control circuit 9 is initialized, the power is restored and the program is restarted. The induction heating control circuit 9 first reads out the memory control process step stored in the nonvolatile memory 10 and sets it as the number of control process steps to be executed. Therefore, the operation can be resumed from the process step before the occurrence of the power failure. it can. In addition to the case where the program is restarted due to a power failure, the input voltage detection means 6 is used to stop the induction heating control heating when the power supply voltage drops below a predetermined voltage such as AC80V, and the voltage is normal. Induction heating control circuit so as to resume operation from the step before the power supply voltage drop by reading out the memory control step stored in the nonvolatile memory 10 and setting it as the number of steps of the control step to be executed when returning to 9 can also be configured.

  As described above, in the first embodiment, the input voltage detection means 6 for detecting the power supply voltage of the commercial power supply 1, the nonvolatile memory 10 as the storage means for storing the control data necessary for control, and the heated member 5 are provided. An induction heating control device comprising an induction heating control circuit 9 as a heating control means for controlling an induction heating coil 3 as a heating means for electromagnetic induction heating, wherein the nonvolatile memory 10 retains the control data without a power source The induction heating control circuit 9 stores the control state at that time in the nonvolatile memory 10 as the control data when the control process of the induction heating control circuit 9 changes, and the power supply voltage decreases. When the power supply voltage is restored after the induction heating control circuit 9 has stopped operating, the control is based on the control data stored in the nonvolatile memory 10 Characterized in that there.

  In this way, when returning from the operation stop due to the power supply voltage drop, the control data necessary for resuming the control process before the operation stop is stored in the nonvolatile nonvolatile memory 10 when the control process changes. The control data required when the power supply voltage is normal is reliably retained, and a stable power failure recovery operation can be performed. Therefore, it is possible to provide an electromagnetic induction heating control device that can perform a stable return operation and start the operation from the stored control process.

  In the first embodiment, the induction heating control circuit 9 is configured to stop the heating output of the induction heating coil 3 when the voltage detected by the input voltage detection means 6 is lower than a predetermined voltage. It is characterized by being.

  Thus, when the power supply voltage becomes unstable, the heating output of the induction heating coil 3 is stopped, and control is performed based on the control data stored in the nonvolatile memory 10 when the power supply voltage returns to the normal state. By performing the operation, the operation can be resumed from the step before the power supply voltage is lowered. Therefore, even if the power supply voltage is temporarily lowered, the operation can be resumed from the process before the power supply voltage is lowered.

  FIG. 3 shows a second embodiment of the present invention, in which 1 is an AC power source, 2 is a rectifying and smoothing circuit for rectifying and smoothing an AC power source voltage from a commercial power source 1 and converting it to DC input power. The rectifying / smoothing circuit 2 includes a diode bridge 2a, a choke coil 2c, and a smoothing capacitor 2b. One end of a parallel circuit of the induction heating coil 3 and the resonance capacitor 8 and one end of a parallel circuit of the induction heating coil 23 and the resonance capacitor 28 are connected to the output side of the rectifying and smoothing circuit 2. Switching elements 4 and 24 made of IGBT are connected to the other ends of these parallel circuits, respectively. Each series circuit of the switching elements 4 and 24 and the circuit in which the resonance capacitors 8 and 28 are connected in parallel to the induction heating coils 3 and 23 corresponds to an inverter circuit that converts the DC input power into high-frequency power. Then, the switching elements 4 and 28 are alternately switched by a pulse drive signal supplied to the gates of the switching elements 4 and 28, and the induction heating coil 3 and the resonance capacitor 8 or the induction heating coil 23 and the resonance capacitor 28 are switched. Is caused to cause a high-frequency current to flow through the induction heating coils 3 and 23.

  As power feedback control means for outputting the induction heating coil 3 with a desired set power, an input current detection means 7 for detecting an input current supplied from the commercial power source 1 to the inverter circuit, and the input current detection means 7 On the basis of the detection result obtained in the above, an induction heating control circuit 9 composed of, for example, a microcomputer for variably controlling the switching operation, that is, the on-time of the switching elements 4, 24 is provided. The input current detection means 7 includes a current transformer 1 inserted in a line connecting the commercial power source 1 and the diode bridge 2a, and a rectifier stack 31 as a rectifier that rectifies the detected current obtained on the secondary side of the current transformer 1. And a smoothing circuit including a resistor 32 and a smoothing capacitor 33 for smoothing the detected voltage after the rectification at the subsequent stage of the rectification stack 31. The microcomputer constituting the induction heating control circuit 9 periodically takes in the detected voltage after smoothing by the smoothing circuit from the A / D input port and performs induction heating control.

  Conventionally, after rectification by the rectification stack 31, the waveform is smoothed by hardware and the current A / D value is taken into the microcomputer and averaged, for example, 50 times every 1 ms. FIG. 4 shows the A / D input port voltage waveform of the induction heating control circuit 9 and corresponds to the power supply voltage waveform of the commercial power supply 1. As shown in the figure, in the present invention, the capacitance of the smoothing capacitor 33 as the smoothing means is made minute (for example, 0.1 μF) to such an extent that the waveform rectified by the rectifying stack 31 is not deformed. Then, the A / D conversion value of the detected current is taken into the induction heating control circuit 9 a plurality of times, for example, at a period of 1 ms, which is sufficiently shorter than a half period of the AC voltage waveform of the commercial power supply 1 (half period T in FIG. 4). The change of the input current from the commercial power source 1 is detected at high speed by performing the averaging process with software. Thereby, the induction heating coils 3 and 23 can be alternately switched and controlled at the zero-cross timing (timing when the input current becomes zero) of the half cycle of the commercial power source 1.

  As described above, in the second embodiment, the input current detection means 7 for detecting the input current supplied from the commercial power source 1 to the induction heating coils 3 and 23 as the heating means, and the change in the input current based on the change in the input current. An induction heating control device comprising an induction heating control circuit 9 as a heating control means for controlling a plurality of induction heating coils 3 and 23 for electromagnetically heating the heating member 5, wherein the input current detection means 7 The induction heating control circuit 9 includes a rectification stack 31 as a rectifier for rectifying current and a smoothing capacitor 33 having a capacity that does not deform the waveform after rectification by the rectification stack 31. The change of the input current is detected by taking in the current value of the input current a plurality of times from the input current detection means 7 in the meantime.

  In this way, since the waveform indicating the change in the input current is taken into the induction heating control circuit 9 without being smoothed, the change in the input current can be detected at high speed, and the plurality of induction heating coils 3, 23 can be detected in a short time. Can be sequentially energized. Therefore, an electromagnetic wave capable of improving the responsiveness to the input current and making the temperature distribution of the member to be heated 5 uniform by controlling energization of the plurality of induction heating coils 3 and 23 in a half cycle of the commercial power source 1. An induction heating control device can be provided.

  FIG. 5 shows a third embodiment of the present invention, in which the commercial power source 1 supplies AC power to the induction heating coils 3 and 23. 50 is an inverter circuit as a switching means provided with a switching element for driving the induction heating coil 3, detects a high frequency current supplied to the induction heating coil 3, and sends a current detection signal 52 to the induction heating control circuit 9. Output. On the other hand, 60 is an inverter circuit as a switching means provided with a switching element for driving the induction heating coil 23, detects a high-frequency current supplied to the induction heating coil 23, and sends a current detection signal to the induction heating control circuit 9. 62 is output. The induction heating control circuit 9 receives output setting signals 53 and 63 for determining the heating output of the induction heating coils 3 and 23, respectively, and current detection signals 52 and 62 as feedback signals input from the inverter circuits 50 and 60, respectively. Accordingly, the PWM signals 51 and 61 that are PWM-controlled are configured as the inverter circuits 50 and 60 so that the heating outputs of the induction heating coils 3 and 23 become the outputs determined by the output setting signals 53 and 63, respectively. The heating output is input to each switching element and the heating output is feedback-controlled.

  When the induction heating coils 3 and 23 are simultaneously oscillated, if the difference in the oscillation frequency of each switching element constituting the inverter circuits 50 and 60 is less than the audible sound range (for example, less than 20 KHz), the frequency causes the coil and the heated object to change. It may vibrate and hear annoying sounds. Therefore, it is necessary to control each oscillation frequency so that the difference between the frequencies of the PWM signals 51 and 61 is more than the audible range (20 KHz or more in the above example). In the third embodiment, as shown in the timing chart of FIG. 6, the frequency of the PWM signal 51 is 25 KHz and the frequency of the PWM signal 61 is 45 KHz, so the difference is 45 KHz-25 KHz = 20 KHz, Satisfies. If the output setting signals 53 and 63 are the same setting values, the tuning is performed so that the difference in frequency between the PWM signals 51 and 61 is 20 KHz or more and the same output (watt) can be obtained from both electromagnetic induction heating coils. To do. That is, the pulse conduction widths of the PWM signals 51 and 61 are fixed, and only the period (frequency) is changed so that the difference between the frequencies is 20 KHz or more and the total pulse conduction width per unit time is the same. For example, in FIG. 6, when the single pulse conduction width of the PWM signal 51 is 10 μs and the single pulse conduction width of the PWM signal 61 is 5 μs, the PWM signal 61 is output during one pulse of the PWM signal 51 (one cycle). What is necessary is just to change a frequency so that two pulses may be output. In addition, the above control method can be used also for cookers, such as a rice cooker provided with the cover heating means by electromagnetic induction heating, and the pot heating means.

  As described above, in the third embodiment, the electromagnetic induction heating for controlling the induction heating coil 3 as the first induction heating means for heating the inner pot with the alternating magnetic field and the induction heating coil 23 as the second induction heating means. In the control device, the pulse frequency of the switching element constituting the inverter circuit 50 as the switching means for energizing the induction heating coil 3 and the pulse frequency of the switching element constituting the inverter circuit 60 as the switching means for energizing the induction heating coil 23 Is configured to perform switching operation at a distance greater than the audible range.

  In this way, since the switching operation can be performed so that the difference in pulse frequency between the two inverter circuits 50 and 60 does not fall below the audible range, the two induction heating coils 3 and 23 are driven simultaneously. However, no annoying audible noise associated with the vibration of the coil or heated object is generated.

  The present invention is not limited to the above embodiments, and can be modified without departing from the spirit of the present invention.

It is a circuit diagram which shows the structure of the electromagnetic induction heating apparatus carrying the electromagnetic induction heating control apparatus in 1st Example of this invention. It is a flowchart which shows the control data storage process of an electromagnetic induction heating control apparatus same as the above. It is a circuit diagram which shows the structure of the electromagnetic induction heating apparatus carrying the electromagnetic induction heating control apparatus in 2nd Example of this invention. It is a wave form diagram which shows the A / D input port voltage of an electromagnetic induction heating control apparatus same as the above. It is a block diagram which shows the structure of the electromagnetic induction heating apparatus carrying the electromagnetic induction heating control apparatus in 3rd Example of this invention. It is a timing diagram which shows the control signal of an electromagnetic induction heating control apparatus same as the above.

Explanation of symbols

1 Commercial power supply 3 Induction heating coil (heating means)
5 Heated member 6 Input voltage detection means 7 Input current detection means 9 Induction heating control circuit (heating control means)
10 Non-volatile memory (memory means)
23 Induction heating coil (heating means)
31 Rectifier stack (rectifier)
33 Smoothing capacitor (smoothing means)

Claims (3)

An induction heating control apparatus comprising: a voltage detection means for detecting a voltage; a storage means for storing control information; and a control means for controlling a heating means for electromagnetically heating the member to be heated, wherein the storage means When the control process changes, the control means stores the control state at that time in the storage means as the information, the voltage drops, the control means stops operating, and the voltage is An electromagnetic induction heating control device configured to perform control on the basis of the information stored in the storage means when the storage is restored. The electromagnetic wave according to claim 1, wherein the control means is configured to stop the heating output of the heating means when the voltage detected by the voltage detection means is lower than a predetermined voltage. Induction heating control device. An induction heating control device comprising: current detection means for detecting current supplied from a power supply; and control means for controlling a plurality of heating means for electromagnetically heating a member to be heated, wherein the current detection means A rectifier that rectifies the current; and smoothing means having a capacity that does not deform the rectified waveform. An electromagnetic induction heating control device configured to detect a change in the current by being taken in once.

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