JP2010262825A - High-frequency power source device for dielectric heating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency power source device for dielectric heating capable of continuing welding operations, in case breakdown or corona discharge generated during a welding operation temporarily occurs without affecting quality of a heated body. <P>SOLUTION: The high-frequency output portion 10 generates and outputs high frequency having a predetermined frequency. A high-frequency impression portion 20 impresses the high frequency outputted from the high-frequency output portion 10 to a pair of electrodes 61, 62 of a processing portion 60. The processing portion 60 uses the high frequency impressed to the pair of electrodes 61, 62 by the high high-frequency impression portion 20 to process a heated body 63. A breakdown detection portion 30 detects a breakdown phenomenon generated at the processing portion 60. A discharge detection portion 40 detects a discharge phenomenon generated at the processing portion 60. Based on the detected results at the breakdown detection portion 30 and the discharge detection portion 40, an output control portion 50 controls the high-frequency output from the high-frequency output portion 10 through a temporary stoppage or a complete shut down. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a high frequency power supply for dielectric heating in which a high frequency is applied between a pair of electrodes sandwiched by a heated object such as a polymer material, and the heated object is heated or welded using a dielectric loss of the material Relates to the device.

  The high-frequency power supply device for dielectric heating is a device that performs processing such as heating or welding on a polymer material having a large dielectric loss such as polyvinyl chloride resin or polypropylene resin. FIG. 8 is a conceptual diagram for explaining an example of the high frequency power supply device for dielectric heating. In FIG. 8, a heated body 63 in which a plurality of resin films are stacked is sandwiched between a pair of electrodes 61 and 62, and a plurality of high-frequency power supplies 100 apply a high frequency between the pair of electrodes 61 and 62. The resin film is welded.

  The time for applying a high frequency between the pair of electrodes 61 and 62 is determined in advance, and normally there is no problem in the welding operation. However, various factors such as variations in the material and shape of the heated body 63 and changes in the temperature and humidity of the work environment may affect the following problems.

The first problem is that the heated body 63 cannot withstand the high frequency voltage during the welding operation, and the dielectric breakdown of the heated body 63 occurs (FIG. 9A).
Secondly, there is a problem that dielectric breakdown occurs between the electrode 61 and the electrode 62 during the welding operation (FIG. 9B). In this problem, there is a possibility that a nearby heated body 63 may be damaged by a spark generated by dielectric breakdown.
Third, there is a problem that corona discharge is generated from the electrode 61 to the space during the welding operation (FIG. 9C). This problem is caused when the heated body 63 is heated rapidly, the heated body 63 has a larger area than the electrode 62 and has a thick shape, and neither of the above-described two types of dielectric breakdown occurs. It is likely to occur.

  As a countermeasure against these problems, a technique is disclosed in which the state of dielectric breakdown is detected and the application of high frequency is stopped to prevent damage to the heated body 63 (see Patent Documents 1 to 3). ).

JP-A-7-249486 JP 2002-334775 A JP 2006-344535 A

  The techniques disclosed in Patent Documents 1 to 3 described above are techniques for stopping application of a high frequency to a pair of electrodes when a state of dielectric breakdown is detected. That is, the high frequency power supply device for dielectric heating is completely stopped.

  However, the dielectric breakdown of the heated object described above may occur temporarily due to contamination of foreign matters during the welding operation, and the dielectric breakdown of several times may not affect the heated object. . Further, it is conceivable that dielectric breakdown between electrodes that does not cause permanent dielectric breakdown or corona discharge to the space does not affect the damage of the heated object even if it occurs multiple times. In such a case, it is possible to continue the welding operation, and if the high frequency power supply device for dielectric heating is completely stopped and the welding operation is interrupted as in the above-described prior art, the manufacturing yield may be deteriorated. Product quality will be reduced.

  Moreover, although the technique disclosed in Patent Documents 1 to 3 described above employs a technique for detecting a DC through current generated between a pair of electrodes due to dielectric breakdown, in this technique, corona discharge generated from the electrodes to the space. It is technically impossible to detect such as.

  Therefore, the object of the present invention is to provide dielectric heating that can continue the welding operation when the dielectric breakdown or corona discharge that occurs during the welding operation does not affect the quality of the object to be heated. It is to provide a high frequency power supply apparatus for use.

  The present invention is directed to a dielectric heating high frequency power supply apparatus that heats or welds an object to be heated using dielectric loss due to high frequency. In order to achieve the above object, a high-frequency power supply device for dielectric heating according to an aspect of the present invention includes a high-frequency output unit, a high-frequency application unit, a dielectric breakdown detection unit, a discharge detection unit, and an output control unit. .

  The high frequency output unit outputs a high frequency having a predetermined frequency. The high frequency application unit applies the high frequency output from the high frequency output unit between a pair of electrodes between which the heated object is held. The dielectric breakdown detector monitors a change in voltage generated between the pair of electrodes and detects a dielectric breakdown phenomenon. The discharge detection unit monitors a change in voltage generated between a high frequency traveling between the pair of electrodes from the high frequency application unit and a high frequency reflected from the pair of electrodes to the high frequency application unit, and detects a corona discharge phenomenon. . The output control unit temporarily stops the high-frequency output from the high-frequency output unit for a predetermined time when a phenomenon is detected in either the dielectric breakdown detection unit or the discharge detection unit.

  Here, when the cumulative number of phenomenon detections in the dielectric breakdown detection unit exceeds a first predetermined value or the cumulative number of phenomenon detections in the discharge detection unit exceeds a second predetermined value, the output control unit outputs a high-frequency output. The high-frequency output from the unit should be stopped completely.

  Note that a typical breakdown detection unit is connected to the output of the high-frequency application unit, and detects a voltage that drops due to a through current generated by a short circuit between a pair of electrodes, and a through current detection unit A breakdown determination unit that compares the voltage detected in step 1 with a predetermined threshold value to determine the occurrence of a breakdown phenomenon.

  In addition, a typical discharge detection unit includes a directional coupler that extracts a high-frequency voltage that travels between the pair of electrodes from the high-frequency application unit and a high-frequency voltage that is reflected from the pair of electrodes to the high-frequency application unit, Differentiating each of the two voltages extracted by the directional coupler, a differential circuit for detecting a change in the two voltages, and obtaining a difference between the two voltage changes, comparing with a predetermined threshold, and discharging phenomenon It is comprised by the discharge determination part which determines generation | occurrence | production of. The high-frequency application unit includes a high-frequency phase that travels from the high-frequency application unit to the pair of electrodes and a high-frequency phase that is reflected from the pair of electrodes to the high-frequency application unit when a corona discharge phenomenon occurs in the heated object. However, it is desirable to provide a phase adjustment circuit that adjusts the phase so as to have an in-phase relationship.

  Further, the output control unit outputs a control signal for instructing a temporary stop of the high frequency output to the high frequency output unit for a predetermined time when the phenomenon is detected in either the dielectric breakdown detection unit or the discharge detection unit. A counter that cumulatively counts the number of times the timer outputs a control signal for each dielectric breakdown phenomenon and discharge phenomenon, and when the count value of the counter exceeds the first or second predetermined value, complete high-frequency output It can be configured by a latch circuit that outputs a control signal instructing the stop to the high-frequency output unit.

  According to the present invention, when the dielectric breakdown or corona discharge that occurs during the welding operation is temporary and does not affect the quality of the heated object, the welding operation is continued and the quality of the heated object is affected. In such a case, since the welding operation is stopped, it is possible to minimize damage caused by damage to the heated body and the electrode while maintaining the quality of the heated body. This effect is significant in welding operations performed at the final stage of the manufacturing process.

1 is a functional block diagram showing a configuration of a high frequency power supply device 1 for dielectric heating according to an embodiment of the present invention. The figure which shows an example of the concrete circuit of the switching circuit 12 The figure which shows an example of the concrete circuit of the matching circuit 24 The figure which shows an example of the concrete circuit of the dielectric breakdown detection part 30 The figure which shows an example of the concrete circuit of the discharge detection part 40 The figure which shows an example of the concrete circuit of the output control part 50 The figure explaining the impedance characteristic of the phase adjustment circuit 23 and a transmission line Conceptual diagram illustrating an example of a high frequency power supply device for dielectric heating The figure explaining the dielectric breakdown and corona discharge which occur in the high frequency power supply device for dielectric heating

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a functional block diagram showing a configuration of a high frequency power supply device 1 for dielectric heating according to an embodiment of the present invention. In FIG. 1, a high frequency power supply device 1 for dielectric heating according to the present invention includes a high frequency output unit 10, a high frequency application unit 20, a dielectric breakdown detection unit 30, a discharge detection unit 40, an output control unit 50, and a processing unit 60. With. The processing unit 60 has a structure in which a heated body 63 to be subjected to processing such as heating and welding is sandwiched between a pair of electrodes (or dies constituting the electrodes) 61 and 62.

First, the outline | summary of each structure of the high frequency power supply device 1 for dielectric heating is demonstrated.
The high frequency output unit 10 generates and outputs a high frequency having a predetermined frequency. The high frequency application unit 20 applies the high frequency output from the high frequency output unit 10 to the pair of electrodes 61 and 62 of the processing unit 60. The processing unit 60 processes the heated object 63 using the high frequency applied to the pair of electrodes 61 and 62 by the high frequency applying unit 20. The dielectric breakdown detector 30 detects a dielectric breakdown phenomenon that occurs in the processing unit 60. The discharge detection unit 40 detects a discharge phenomenon that occurs in the processing unit 60. The output control unit 50 controls the high frequency output from the high frequency output unit 10 based on the detection results in the dielectric breakdown detection unit 30 and the discharge detection unit 40.

Next, the detailed configuration and operation of each configuration of the dielectric heating high-frequency power supply device 1 will be described.
The high frequency output unit 10 includes an oscillation circuit 11 and a switching circuit 12. The oscillation circuit 11 is a circuit that generates a high frequency having a frequency suitable for dielectric heat treatment, and for example, a crystal oscillation circuit, a phase control oscillation circuit, a DDS oscillation circuit, a CR oscillation circuit, or an LC oscillation circuit is used. The oscillation method of the oscillation circuit 11 may be either a semiconductor method or an electron tube (vacuum tube) method. The high frequency output from the oscillation circuit 11 is a small signal of several mW level. The switching circuit 12 is a circuit for switching whether or not to output the high frequency generated by the oscillation circuit 11 to the high frequency applying unit 20 in accordance with a control signal supplied from the output control unit 50. A high-frequency switch or the like that switches the cutoff state is used. FIG. 2 is a diagram showing an example of a specific circuit of the switching circuit 12, a circuit using a high speed diode (FIG. 2A), and a circuit for cutting off the base bias of the transistor (FIG. 2B). A circuit for switching the gate voltage of the two-gate FET (FIG. 2C) and a double balance circuit (FIG. 2D) are shown. The output switching performed by the switching circuit 12 is preferably performed at a speed of 1 μsec or less.

  The high frequency application unit 20 includes an excitation amplifier circuit 21, a power amplifier circuit 22, a phase adjustment circuit 23, and a matching circuit 24. The excitation amplification circuit 21 amplifies the high frequency output from the oscillation circuit 11 to a level at which the power amplification circuit 22 can operate. The power amplifying circuit 22 further amplifies the high frequency amplified by the excitation amplifying circuit 21 until power necessary for the dielectric heating process is obtained. For the power amplification circuit 22, an amplification element such as an electron tube or a power semiconductor is used. The phase adjustment circuit 23 adjusts the phase of the high frequency power amplified by the power amplification circuit 22. Specifically, the impedance when the matching circuit 24 is viewed from the power amplifier circuit 22 is higher when the heated body 63 is short-circuited (abnormal state) than when the heated body 63 is not short-circuited (steady state). It is adjusted to become. For this phase adjustment circuit 23, for example, a reflective hybrid circuit, a coaxial cable, or the like is used. The matching circuit 24 inputs the high frequency output from the phase adjustment circuit 23 via the discharge detection unit 40, and in order to efficiently supply the electric power generated at the high frequency to the heated body 63, the matching circuit 24 has an impedance with the heated body 63. Perform matching. As the matching circuit 24, for example, the configuration of FIG. Since the object to be heated 63 also changes the complex impedance at the same time as the temperature and physical dimensions change due to heating, the matching circuit 24 is configured so that optimum impedance matching can always be performed by automatically following this change. Is desirable.

  Generally, in a dielectric heating work environment, the processing unit 60 may be provided at a physical distance from the high-frequency application unit 20. In this case, it is more efficient to arrange the matching circuit 24 near the heated body 63 with less power loss. Therefore, it is preferable to construct the transmission line from the phase adjustment circuit 23 to the matching circuit 24 using a coaxial line, a parallel line, or the like. If the line length of this transmission line is set appropriately, it can function as the phase adjustment circuit 23, and the phase adjustment circuit 23 can be omitted.

  In addition, in the conventional device that self-oscillates using an electron tube type oscillation circuit, a problem well-known to those skilled in the art (description is omitted), the occurrence of dielectric breakdown in the heated body 63, and the accompanying impedance reduction. The present invention addresses the problem of repeated vicious circles of further expansion of dielectric breakdown due to this decrease as follows.

That is, when dielectric breakdown occurs in the heated body 63, the phase of the high frequency (traveling wave) traveling from the power amplifier circuit 22 to the matching circuit 24 and the high frequency (reflected wave) reflected from the matching circuit 24 to the power amplifier circuit 22. The phase adjustment circuit 23 and / or the transmission line is set in advance so that the phase of the phase is in-phase. As a result, when the matching circuit 24 is viewed from the power amplifier circuit 22, the abnormal impedance Rl ′ when the reflected wave is generated transitions to a higher side compared to the stationary impedance Rl when the reflected wave is generated. It will be. On the other hand, since the output power Po of the power amplifier circuit 22 is approximated by Po = Vdd ² / (2 · Rl), the output power Po transitions to the lower side.

For this reason, even if dielectric breakdown occurs in the heated body 63, it operates in a direction to reduce the dielectric breakdown, and damage to the electrodes 61 and 62 and the heated body 63 can be minimized. For example, assuming that the phase constant of the phase adjustment circuit 23 and / or the transmission line is β, the characteristic impedance is Zo, and the input impedance of the matching circuit 24 at the time of dielectric breakdown is Zl, the impedance Rl ′ at the time of abnormality is generally It can be expressed by an equation (see FIG. 7).
Rl ′ = Zo · (Zl + jZo · tan β) / (Zo + jZl · tan β)
If tan β is selected to an appropriate value in this equation, Rl << Rl ′ is established, and the output power Po of the power amplifier circuit 22 is reduced.

  The processing unit 60 has a pair of an electrode 61 (hot side) connected to the output of the matching circuit 24 and an electrode 62 (cold side) connected to the ground. The heated body 63 is a thermoplastic material such as a polyvinyl chloride resin film or a polypropylene resin film, or wood, and is sandwiched between the electrode 61 and the electrode 62.

  The dielectric breakdown detection unit 30 is connected to the electrode 61 that is an output of the matching circuit 24 and detects dielectric breakdown of the heated body 63 and dielectric breakdown between the electrode 61 and the electrode 62 that occur in the processing unit 60. This dielectric breakdown detection unit 30 is realized, for example, with the configuration shown in FIG. The dielectric breakdown detection unit 30 illustrated in FIG. 4 includes a through current detection circuit 31 and a dielectric breakdown determination circuit 32.

  In FIG. 4, the through current detection circuit 31 applies a DC power source Vcc to the electrode 61 via a serially connected resistance R for detecting breakdown and an inductor L for suppressing high-frequency current, and the resistance R and the inductor L are connected to each other. In this configuration, the voltage appearing at the connection point a is extracted. With this configuration, in the steady state, the voltage Hi obtained by dividing the DC power source Vcc by the resistance R, the inductor L, and the internal resistance of the heated body 63 appears at the connection point a, and in the abnormal state in which the dielectric breakdown occurs, Since the internal resistance of the body 63 is short-circuited and a through current flows between the electrodes 61 and 62, a voltage Lo obtained by dividing the DC power source Vcc by only the resistor R and the inductor L appears at the connection point a. That is, when the transition from the steady state to the abnormal state occurs, the voltage appearing at the connection point a decreases from the voltage Hi to the voltage Lo.

  The dielectric breakdown determination circuit 32 inputs a voltage appearing at the connection point a of the through current detection circuit 31 and compares it with a predetermined threshold value Vdc to determine whether or not dielectric breakdown has occurred. Specifically, the threshold value Vdc is set to an arbitrary value between the voltage Hi and the voltage Lo, and the dielectric breakdown determination circuit 32 indicates that the dielectric breakdown has occurred if the input voltage is equal to or lower than the threshold value Vdc. A trigger signal for notifying is output.

  Referring again to FIG. 1, the discharge detection unit 40 is provided between the phase adjustment circuit 23 and the matching circuit 24 of the high-frequency application unit 20 and detects corona discharge from the electrode 61 generated in the processing unit 60 to the space. . The discharge detection unit 40 is realized by the configuration shown in FIG. 5, for example. The discharge detection unit 40 illustrated in FIG. 5 includes a directional coupler 41, detection circuits 42 and 43, differentiation circuits 44 and 45, a subtraction circuit 46, and a corona discharge determination circuit 47.

  In FIG. 5, the directional coupler 41 extracts a high frequency (traveling wave) voltage traveling from the power amplifier circuit 22 to the matching circuit 24 via the phase adjustment circuit 23 and outputs the voltage to the detection circuit 42. Further, the directional coupler 41 extracts a high frequency (reflected wave) voltage reflected from the matching circuit 24 to the power amplifier circuit 22 via the phase adjustment circuit 23 and outputs the voltage to the detection circuit 43. This extraction is performed by separating each high frequency by 1/1000 times or less. The detection circuit 42 detects the traveling-wave AC voltage output from the directional coupler 41 to obtain the DC voltage Vf. The detection circuit 43 detects the AC voltage of the reflected wave output from the directional coupler 41 and obtains the DC voltage Vr. The differentiating circuit 44 differentiates the direct-current voltage Vf (dVf / dt) to calculate a traveling wave change (acceleration). The differentiating circuit 45 differentiates the DC voltage Vr (dVr / dt) and calculates the change (acceleration) of the reflected wave.

  As is well known, at the moment when corona discharge or the like occurs in the heated body 63, the reflected wave changes in the increasing direction and the traveling wave changes in the decreasing direction. In order to detect this phenomenon, the subtraction circuit 46 subtracts the differential value of the DC voltage Vf from the differential value of the DC voltage Vr to obtain a difference in change (= dVr / dt−dVf / dt). Then, the corona discharge determination circuit 47 inputs the difference between the changes and compares it with a predetermined threshold value Vth to determine whether or not corona discharge has occurred. This threshold value Vth is arbitrarily determined based on the size of the electrodes 61 and 62, the size and material of the heated body 63, and the corona discharge determination circuit 47 determines that the difference in the input change is equal to or greater than the threshold value Vth. A trigger signal for notifying that a corona discharge has occurred is output. Note that this trigger signal is not output when the traveling wave changes and the reflected wave changes in the same direction due to impedance mismatching or the like.

  Referring again to FIG. 1, the output control unit 50 is connected to the dielectric breakdown detection unit 30 and the discharge detection unit 40, and individually switches the switching circuit 12 of the high-frequency output unit 10 according to the trigger signal output from each detection unit. To control. The output control unit 50 is realized, for example, with the configuration shown in FIG. The output control unit 50 shown in FIG. 6 includes first and second timers 51 and 52, first and second counters 53 and 54, and first and second latch circuits 55 and 56.

  The first timer 51 is connected to the output of the dielectric breakdown detection unit 30. When the first timer 51 receives a trigger signal from the dielectric breakdown determination circuit 32 of the dielectric breakdown detection unit 30, the first timer 51 is connected between the input and output terminals of the switching circuit 12 until a predetermined time elapses from the input time point. A control signal to be cut off is output to the switching circuit 12. A typical control signal is a pulse signal. By this control, when dielectric breakdown occurs in the processing unit 60, the application of the high frequency from the high frequency output unit 10 to the processing unit 60 is temporarily stopped for a predetermined time. After the elapse of a predetermined time, the input / output terminals of the switching circuit 12 return to the conductive state, and the application of high frequency from the high frequency output unit 10 to the processing unit 60 is automatically resumed.

  The first counter 53 receives a control signal output from the first timer 51 and cumulatively counts the number of temporary stops that the first timer 51 has performed on the switching circuit 12. This counting is performed, for example, by detecting the rising edge of the pulse signal. The first counter 53 notifies the first latch circuit 55 when the counted cumulative number reaches a predetermined value (counting up).

  In a normal state, the first latch circuit 55 outputs a signal (or no signal) for conducting the input / output terminal of the switching circuit 12 to the switching circuit 12, and receives a count-up notification from the first counter 53. A control signal for shutting off the input / output terminals of the switching circuit 12 is output to the switching circuit 12. The output of this control signal is maintained until it is released by a manual operation by the welding operator. By this control, when dielectric breakdown occurs in the processing unit 60 continuously a plurality of times, the application of the high frequency from the high frequency output unit 10 to the processing unit 60 is completely stopped.

  The trigger signal output from the discharge detection unit 40 is the same as that described in the dielectric breakdown detection unit 30 using the second timer 52, the second counter 54, and the second latch circuit 56. Similar temporary stop and complete stop processing is performed. Note that the predetermined value counted up by the first counter 53 and the predetermined value counted up by the second counter 54 may be the same or different.

As described above, according to the high frequency power supply device 1 for dielectric heating according to an embodiment of the present invention, if the number of occurrences of dielectric breakdown or corona discharge is less than or equal to a predetermined value, the application of high frequency is temporarily performed for a predetermined time. If it exceeds a predetermined value, it stops completely.
As a result, if the dielectric breakdown or corona discharge that occurs during the welding operation is temporary and does not affect the quality of the heated body 63, the welding operation is continued and the quality of the heated body 63 is affected. In this case, the welding operation can be stopped, so that it is possible to minimize damage caused by damage to the heated body 63 and the electrode 62 (mold) while maintaining the quality of the heated body 63.
Further, since the output of the oscillation circuit 11 is controlled by the switching circuit 12, the high-frequency output can be stopped at high speed.

Note that the detailed circuits of the high-frequency application unit 20, the dielectric breakdown detection unit 30, the discharge detection unit 40, and the output control unit 50 described in the above embodiment are examples, and the same applies to any circuit having an equivalent function. It is possible to apply to the present invention.
Further, the structure of the processing unit 60 is not limited to that shown in FIG. 1, and any other structure may be applied as long as it includes a pair of electrodes for applying a high frequency.

  The apparatus of the present invention can be used when processing a polymer material or the like having a large dielectric loss. Especially, the dielectric breakdown or corona discharge generated during the welding operation does not affect the quality of the object to be heated. It is suitable when you want to continue welding work.

DESCRIPTION OF SYMBOLS 1 High frequency power supply device 10 for dielectric heating High frequency output part 11 Oscillation circuit 12 Switching circuit 20 High frequency application part 21 Excitation amplifier circuit 22 Power amplification circuit 23 Phase adjustment circuit 24 Matching circuit 30 Dielectric breakdown detection part 31 Through current detection circuit 32 Dielectric breakdown determination Circuit 40 Discharge detection unit 41 Directional coupler 42, 43 Detection circuit 44, 45 Differentiation circuit 46 Subtraction circuit 47 Corona discharge determination circuit 50 Output control unit 51, 52 Timer 53, 54 Counter 55, 56 Latch circuit 60 Processing unit 61, 62 Electrode 63 Heated object 100 High frequency power supply

Claims (6)

A high-frequency power supply device for dielectric heating that heats or welds an object to be heated using dielectric loss due to high frequency,
A high frequency output section for outputting a high frequency having a predetermined frequency;
A high frequency application unit that applies a high frequency output from the high frequency output unit between a pair of electrodes sandwiched by the heated body;
A dielectric breakdown detector for monitoring a change in voltage generated between the pair of electrodes and detecting a dielectric breakdown phenomenon;
Discharge for monitoring a change in voltage between the high frequency traveling from the high frequency application section to the pair of electrodes and the high frequency reflected from the pair of electrodes to the high frequency application section, and detecting a corona discharge phenomenon. A detection unit;
When a phenomenon is detected in either the dielectric breakdown detection unit or the discharge detection unit, the dielectric heating unit includes an output control unit that temporarily stops the high-frequency output from the high-frequency output unit for a predetermined time. High frequency power supply.   When the cumulative number of phenomenon detections in the dielectric breakdown detection unit exceeds a first predetermined value or the cumulative number of phenomenon detections in the discharge detection unit exceeds a second predetermined value, the output control unit The high frequency power supply device for dielectric heating according to claim 1, wherein the high frequency output from the output unit is completely stopped. The dielectric breakdown detector
A through current detection unit that is connected to the output of the high frequency application unit and detects a voltage that drops due to a through current caused by a short circuit between the pair of electrodes;
The dielectric heating high-frequency power supply device according to claim 1, further comprising a dielectric breakdown determination unit that compares the voltage detected by the through current detection unit with a predetermined threshold value to determine the occurrence of a dielectric breakdown phenomenon. The discharge detector is
A directional coupler that extracts a high-frequency voltage traveling between the pair of electrodes from the high-frequency application unit and a high-frequency voltage reflected from the pair of electrodes to the high-frequency application unit;
A differentiating circuit for differentiating each of the two voltages extracted by the directional coupler and detecting a change in the two voltages;
The high frequency power supply apparatus for dielectric heating according to claim 1, further comprising: a discharge determination unit that obtains a difference between the two voltage changes and compares the predetermined voltage with a predetermined threshold value to determine the occurrence of a discharge phenomenon. The output control unit
When a phenomenon is detected in any one of the dielectric breakdown detection unit and the discharge detection unit, a timer that outputs a control signal instructing a temporary stop of high-frequency output for the predetermined time to the high-frequency output unit;
A counter that cumulatively counts the number of times the timer has output the control signal for each dielectric breakdown phenomenon and discharge phenomenon;
The latch circuit according to claim 2, further comprising: a latch circuit that outputs a control signal instructing complete stop of the high-frequency output to the high-frequency output unit when a count value of the counter exceeds the first or second predetermined value. High frequency power supply for dielectric heating.   When the corona discharge phenomenon occurs in the heated body, the high-frequency applying unit reflects a phase of a high frequency that travels from the high-frequency applying unit to the pair of electrodes, and reflects between the pair of electrodes to the high-frequency applying unit. The high frequency power supply device for dielectric heating according to claim 4, further comprising a phase adjustment circuit that adjusts the phase so that the phase of the high frequency is in phase.

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