JP3087546B2 - High frequency heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency heating apparatus for heating a dielectric material such as food by utilizing microwave dielectric heating, and more particularly to a power supply for generating microwaves.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 20, a power supply for a high-frequency heating apparatus of this type is configured so that a magnetron 2 is driven by an inverter power supply 20. The inverter power supply 20 receives power supply from DC obtained by rectifying the commercial power supply 23, and drives the main semiconductor switching element 3, a resonance circuit including a capacitor and an inductor, and a magnetron for converting the power into a high-frequency AC. Transformer 4 for obtaining a high voltage necessary for the power supply, a high-voltage rectifier circuit 21 for rectifying high-voltage alternating current of the boost transformer 4, a drive circuit 6 for driving the main semiconductor switching element 3, and the like. The magnetron 2 oscillates at about 2.4 gigahertz and generates microwaves when energized with a voltage of about -4 kilovolts generated by the inverter power supply 20. The high-frequency heating device is a device for heating an object to be heated such as food using the microwave.

The high voltage generated by the step-up transformer 4 is rectified by a high-voltage rectifier circuit 21. The step-up transformer 4 and the high-voltage rectifier circuit 21 are provided on the same printed circuit board as shown in FIG. 21 and are electrically connected in a pattern. However, the connection between the magnetron 2 and the high-voltage rectifier circuit 21 and the step-up transformer 4 is as shown in FIG.
2 are connected.

FIG. 22 is a circuit diagram of a portion where a high voltage of the inverter power supply 20 is generated. Since high voltage is generated at the points indicated by (a) to (d) in the figure, oil, vapor or dust generated during heating of the food, insects entering the apparatus from the outside, etc. are generated at the high voltage. When such sparks are generated, sparks may be generated in the area, and if the sparks are continuously generated, there is a danger that electric parts such as a printed board and lead wires nearby burn due to sparks and cause a fire. Therefore, it is necessary to immediately stop the inverter power supply 20 when a spark occurs.

[0005] The term "spark" as used herein means that a part of an electric component to which a high voltage is applied has a relatively low impedance. That is, it is not intended to positively detect a discharge such as a corona discharge having a very small change in impedance or a discharge caused by a discharge having an impedance close to the impedance (several hundred ohms) of a magnetron. Actually generated sparks often include cockroaches and the like, which come into contact with high voltage portions to induce sparks, and such sparks have very low impedance. Therefore, the conventional high-frequency heating device has a configuration in which the input current and the secondary side current of the step-up transformer 4 are detected to detect the occurrence of spark, and the occurrence of spark is detected by comparing the average value of each current. Has adopted.

More specifically, referring to FIG. 20, a current supplied from a commercial power supply 23 as an input current is detected by a first current detection circuit 24 including a current transformer, a rectifier circuit, and a smoothing circuit, and output as a voltage. Further, the secondary side current of the step-up transformer 4 is similarly converted into a current transformer, a rectifier circuit,
The second current detection circuit 25 including a smoothing circuit outputs a voltage, and the output voltage value of both is compared by a comparator 26. The comparator 26 is connected to the drive circuit 6 and has a function of forcibly stopping the drive circuit 6 according to the output value. The relationship between the output voltage values of the first current detection circuit 24 and the second current detection circuit 25 described above is set as shown in FIG. In the figure, V1 is the output voltage value of the first current detection circuit 24, and V2 is the second current detection circuit 2.
The output voltage value is 5, and in a normal case, V1> V2 (1).

If the parts shown in FIG.
When a spark (equivalent to a sharp drop in impedance) occurs in the portion (1), an excessive current flows through the loop including the second current detection circuit 25 on the secondary side of the step-up transformer 4. Accordingly, the output voltage value of the second current detection circuit 25 rapidly increases and becomes V2 'shown in FIG. 23, and the relationship with the output voltage value V1 of the first current detection circuit 24 is V1 <V2'. (2) and the relation is inverted as compared with the equation (1). Therefore, the output level of the comparator 26 for comparing the magnitudes of the two is inverted, and the driving circuit 6 can be forcibly stopped.

[0008]

However, the above configuration has the following problems. First, in order to detect the occurrence of a conventional spark, an input current and a secondary current of the step-up transformer 4 are detected by a first current detection circuit and a second current detection circuit, respectively, and the respective voltage values V1 and V1 are detected.
In the configuration using the fact that the relationship between the two when the spark is normal and the relationship when the spark occurs is given by the expression (2), the relationship shown in FIG. There is a problem that a spark cannot be detected at (a) which is both ends of the secondary winding of the boosting transformer shown and (d) which is a loop not including the second current detection circuit. That is, when sparks occur at the points (a) and (d), the voltage output value V1 of the first current detection circuit and the voltage output value V2 ″ of the second current detection circuit are V1 >> V2 ″. (3) This is because the conventional spark detection means cannot detect sparks at all locations.

Further, in the conventional example, the high-voltage rectification is a half-wave voltage rectification system. In this system, the voltage for energizing the magnetron is a half-wave rectification as shown by V4 in FIG. The current flowing through the magnetron also has a half-wave current waveform corresponding to the voltage. Therefore, when increasing the output of the magnetron, the current I4
Will increase, but the life of the magnetron depends on the current peak of the magnetron.
The peak value is preferably lower.

Therefore, in order to solve this problem, a full-wave rectifier circuit shown in FIG. 25 is employed for the high-voltage rectifier circuit. It is known that when a full-wave rectifier circuit is employed, the voltage V4 'for energizing the magnetron and the radio wave I4' flowing through the magnetron are as shown in FIG.
However, the half-wave voltage doubler rectifier circuit requires only one diode and one capacitor. However, a full-wave rectifier circuit requires two diodes and two capacitors, which increases the number of components. As shown in FIGS. 25A to 25H, the number of parts where sparks may occur due to the increase in the number of parts also increases as compared with the half-wave rectifier circuit. There is a problem that means for performing the above must be adopted.

In addition, the following problem arises by employing the full-wave rectifier circuit. That is, in the case of employing a configuration in which the input current and the secondary side current of the step-up transformer 4 are detected as in the conventional example, and the occurrence of spark is detected by comparing the average value of the respective currents, In the voltage doubler rectification method, as shown in FIG. 22, the line where the current transformer 11 is inserted to detect the secondary current is the chassis potential 12 (the chassis is grounded).
In the case of the full-wave rectifier circuit shown in FIG.
Since a high voltage is applied to the line 27 into which the current transformer is inserted in order to detect the secondary current of
It is necessary to strengthen the insulation of the current transformer, and as a result, there is a problem that the current transformer becomes very large.

Further, the connection between the magnetron 2 and the step-up transformer 4 or the high voltage rectifier circuit 5 will be described. As described in the conventional example, these connections are made with the lead wires 22. However, if the connection of the lead wires 22 is forgotten in the assembling process and the high-frequency heating device is operated as it is, the magnetron 2 does not operate. However, a high voltage is generated in the printed circuit board. In this state, a serviceman tries to repair the high-frequency heating device.
If you remove the chassis cover of the high-frequency heating device and touch the printed circuit board, it will be very dangerous. For this reason, when the connection of the lead wire 22 is forgotten, there is a problem that the inverter circuit must be stopped immediately.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a structure for reliably detecting a spark in a high-voltage portion, detecting a disconnection between a magnetron and an inverter circuit, and immediately stopping the inverter circuit.

[0014]

In order to solve the above problems SUMMARY OF THE INVENTION, the high-frequency heating apparatus first aspect of the present invention, a power supply source,
A first current detection circuit for detecting an average amount of current supplied from the power supply source, a switching element for converting DC power to high-frequency AC power, and a high-frequency power required for driving the magnetron. A step-up transformer for boosting a voltage, a high-voltage rectifier circuit using a full-wave voltage rectification method for rectifying high-voltage AC power of the step-up transformer, a drive circuit for the switching element, and a plurality of components constituting the high-voltage rectifier circuit. A second current detection circuit that obtains an average amount of current of at least one component of the electrical component that becomes a chassis potential of the electrical component; an output of the first current detection circuit;
Input the output of the second current detection circuit and drive the calculation result after the calculation.
Comparing means for outputting the first current
Time constant τ1 consisting of a resistor and a capacitor in the detection circuit
When the second current detection circuit consists of a resistor and a capacitor
The constant τ2 is configured so that τ1 <τ2.
You.

[0015] Secondly, a current detection circuit for detecting an average amount of current supplied from the power supply source, a switching element for converting a DC power into high frequency AC power, the high-frequency AC power for driving the magnetron A step-up transformer for stepping up to a high voltage necessary for the step-up transformer, a high-voltage rectifier circuit using a full-wave voltage doubler rectification method for rectifying the high-voltage AC power of the step-up transformer, The output of the current detection circuit and the generation of the reference level.
Input the output of the road and output the operation result to the drive circuit after the operation
Comparison means and the location after the inverter circuit is started.
A timer circuit for measuring a fixed time, wherein the timer
After a predetermined time measured by the circuit, the reference level generating circuit
An output value 1 which is an output, and a predetermined value different from the output value 1
And the ratio of the output value 2 of the current detection circuit to the output value of the current detection circuit
To lower impedance in the high voltage rectifier circuit or
Disconnection between the magnetron and the step-up transformer
The output value of the current detection circuit is between output value 1 and output value 2.
Inverter circuit that stops the operation of the drive circuit if it comes off
It has a road .

[0016]

By the action of the present invention is the first means, that detects the discharge of the high-voltage portion performs stop of the switching element
Therefore, even when the output is controlled, the spark can be accurately detected.

According to the second means, the disconnection between the magnetron and the step-up transformer can be detected and the switching element can be stopped immediately.

[0018]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment corresponding to the first invention of the present invention. In FIG. 1, an inverter power supply 1 includes a main semiconductor switching element 3 for receiving a supply of DC power obtained by rectifying a commercial power supply and converting it into a high-frequency AC, a resonance circuit including a capacitor and an inductor, and a magnetron 2. Transformer 4 for obtaining a high voltage necessary to drive the power supply, a high-voltage rectifier circuit 5 for rectifying a high-voltage AC of the boost transformer 4, a drive circuit 6 for driving the main semiconductor switching element 3, and a main semiconductor switching element 3. It comprises an applied voltage detecting circuit 7 for detecting an applied voltage, a reference level generating circuit 8, and the like. As described above, in order to reduce the current peak value of the magnetron 2, the high-voltage rectifier circuit 5 employs a full-wave voltage doubler rectifier circuit composed of two diodes and two capacitors.

The magnetron 2 energized by the inverter circuit 1 outputs a microwave. The magnitude of the microwave output (hereinafter referred to as output) generated by the magnetron 2 is adjusted by the inverter circuit 1. The inverter circuit 1 controls the output by a pulse signal from the microcomputer 9.
The pulse signal from the microcomputer 9 supplies a pulse having a frequency corresponding to a desired output to the inverter circuit 1 and a similar pulse signal to the reference level generating circuit 8 at the same time. The reference level generating circuit 8 is provided with a photocoupler and a frequency F of the pulse signal.
Is converted to a voltage V by an F / V converter. The pulse signal from the microcomputer 9 is once insulated via a photocoupler, and the frequency of the pulse signal is converted to a voltage by the F / V converter to obtain a desired output. An appropriate voltage is generated.

On the other hand, the voltage applied to the main semiconductor switching element 3 also changes according to the output. That is, when the output is small, the applied voltage is small, and when the output is large, the applied voltage is large. FIG. 2 shows the output and the main semiconductor switching element 3.
Voltage V of the applied voltage detection circuit 7 for detecting the applied voltage
c and the voltage Vref generated by the reference level generation circuit 8
Is shown. Voltage Vref generated by reference level generating circuit 8
Is set slightly higher than the detection voltage level Vc of the applied voltage detection circuit 7 (Vref> Vc), and the difference ΔV
(Vref−Vc) is kept almost constant irrespective of the magnitude of the output by the function of the reference level generating circuit 8.

If a spark is generated in a high voltage portion at the time of high output, the impedance seen from the primary side of the step-up transformer decreases, and as a result, an excessive current flows through the main semiconductor switching element 3, and an excessive voltage is generated when the semiconductor device is turned off next time. Is generated in the main semiconductor switching element 3. At this time, the relationship between the voltage Vref generated by the reference level generation circuit 8 and the detection voltage Vc ′ of the applied voltage detection circuit 7 reverses (Vc ′> Vr).
ef) Then, the output level of the comparator 10 for comparing the two voltage levels is inverted, whereby the operation of the drive circuit 6 for driving the main semiconductor switching element 3 is stopped.

In the case of a low output, the normal voltage applied to the main semiconductor switching element 3 is small. Therefore, even if a spark occurs in a high voltage portion, an excessive voltage generated in the main semiconductor switching element 3 is also a high output. Lower than

However, as described above, the voltage Vref generated by the reference level generating circuit 8 also decreases according to the low output and ΔV does not change, so that the voltage Vref generated by the reference level generating circuit 8 is the same as in the case of the high output. And the relationship between the detection voltage Vc of the applied voltage detection circuit 7 is reversed (Vc ′> Vr).
ef) Then, the output level of the comparator 10 that compares the two voltage levels is inverted, whereby the operation of the drive circuit 6 that drives the main semiconductor switching element 3 can be stopped. If the voltage Vr generated by the reference level generation circuit 8
If ef is kept constant irrespective of the output (Vre
f ′) The occurrence of spark at the time of low output cannot be detected.

There is a region where the impedance of the magnetron 2 changes rapidly during the period from the start of the inverter circuit 1 to the oscillation of the magnetron 2. In this region, the magnetron 2 performs a kind of abnormal oscillation called moding. At this time, the voltage applied to the main semiconductor switching element 3 rises rapidly. Therefore, if the voltage Vref ″ generated by the reference level generation circuit 8 is not set to a sufficiently high level at the time of startup, the detection voltage Vc ″ of the applied voltage detection circuit 7 exceeds Vref ″ (Vc ′). '> Vre
f '') The output level of the comparator 10 is inverted, which causes a malfunction such that the operation of the drive circuit 6 for driving the main semiconductor switching element 3 is stopped. Since the period from the start of the inverter circuit 1 to the oscillation of the magnetron 2 is about 5 seconds or less, the timer shown in FIG.
The connection between the / V converter and the comparator 10 is cut off. Comparator 1
0 is a sufficiently high level of Vre which is a partial voltage of the resistor.
f '' is given. With such a configuration, malfunction of the comparator 10 can be prevented.

FIG. 3 shows an embodiment corresponding to the second invention of the present invention. In FIG.
Is configured by a full-wave voltage doubler rectification system comprising two diodes and two capacitors, and flows to the cathode of the diode which has the same potential as the chassis potential of the high-frequency heating device (the chassis of the high-frequency heating device is grounded). The current is detected by using current detecting means 11 for detecting the current. The current detecting means 11 includes a current transformer for outputting the magnitude of current flowing to the anode of the diode as a voltage, a diode for rectifying the output of the current transformer, and a resistor for dividing the DC voltage rectified by the diode. . The output of the current detecting means 11 is compared with the output voltage of the reference voltage generating circuit 12 by the comparator 10. The reference voltage generation circuit 12 includes a photocoupler and an F / V converter for converting the frequency of a pulse signal into a voltage, as described in the embodiment corresponding to the first invention of the present invention. Once the signal is insulated via a photocoupler, F / V
The converter converts the frequency of the pulse signal into a voltage and generates a voltage corresponding to a desired output. The magnitude relationship between the output voltage Vref of the reference voltage generation circuit 12 and the output voltage Vout of the current detecting means 11 with respect to the output is set as shown in FIG. 4 (Vref> Vout).

The problem caused by the adoption of the full-wave rectifier circuit is that there is a possibility that a spark may be generated due to an increase in the number of parts, as shown in FIGS. 25A to 25H. Therefore, it is necessary to employ a means for detecting a spark generated at each location.

Therefore, the present invention employs the above-described method to perform spark detection. That is, the current flowing through the cathode of the diode which has the same potential as the chassis potential constituting the high-voltage rectifier circuit 5 is detected by the current detecting means 11 and is compared with the output voltage of the reference voltage generating circuit 12 so that the spark generation shown in FIG. Among the places where
Sparks in (d), (e), (g), and (h) can be detected. This is because an equivalent circuit that can be considered when a spark occurs in (e) of FIG. 5 is as shown in FIG. In the figure, a resistor R equivalently replaces a diode with a small impedance when a spark occurs. The electric charge stored in the capacitor is rapidly discharged in a loop indicated by an arrow.
1, the output voltage Vout 'of the current detecting means 11 rises and exceeds the output voltage Vref of the reference voltage generating circuit 12 as shown in FIG. Can be stopped.

Since the current flowing through the diode for detecting the current is also proportional to the output, the output voltage of the reference voltage generating circuit 12 is generated by the means described above to generate a voltage corresponding to the desired output. As described in the embodiment, there is an effect that the spark can be accurately detected regardless of the magnitude of the output. FIG. 6 shows an equivalent circuit that can be considered when a spark occurs in (d) shown in FIG. In this case, when the secondary side voltage of the step-up transformer is generated in the direction shown in the figure, an overcurrent flows in the loop shown by the arrow, and this overcurrent passes through the current detecting means 11 and can be detected.

FIG. 7 shows an equivalent circuit that can be considered when a spark occurs in (h) shown in FIG. In this case, the electric charge stored in the capacitor is rapidly discharged in the loop indicated by the arrow, but the overcurrent at this time passes through the current detecting means 11 and can be detected. FIG.
FIG. 8 shows an equivalent circuit that can be considered when a spark occurs in (g) shown in FIG. In this case, the electric charge stored in the capacitor is rapidly discharged in the loop indicated by the arrow, but the overcurrent at this time passes through the current detecting means 11 and can be detected.

FIG. 9 shows an embodiment corresponding to the third invention of the present invention. Referring to FIG.
Reference numeral 3 denotes a current transformer that outputs the magnitude of current flowing to the cathode of the diode as a voltage, a diode that rectifies the output of the current transformer, a resistor that divides the DC voltage rectified by the diode, and a voltage that is divided. It consists of a capacitor provided to take out as an average amount. The output voltage of the current detecting means 13 is compared by a comparator 14 with the output voltage of the reference voltage generating circuit 12. Output voltage Vr of reference voltage generation circuit 12 with respect to output
The magnitude relationship between ef and the output voltage Vout of the current detection means 13 is set as shown in FIG. 10 (Vref <Vou).
t).

With such a configuration, of the places where a spark is likely to occur as shown in FIG.
Sparks in (a), (b), (c), and (f) can be detected. The reason is that an equivalent circuit that can be considered when a spark occurs in FIG. In this case, since the impedance between the secondary winding terminals of the step-up transformer becomes low, a high voltage necessary for the oscillation of the magnetron cannot be supplied, and as a result, the current passing through the current detecting means 13 decreases rapidly. Therefore, the output voltage Vout ′ of the current detecting means 13 is Vref> V as shown in FIG.
out ', the output of the comparator 10 is inverted, and the inverter circuit 1 can be stopped. FIG. 12 shows an equivalent circuit that can be considered when a spark occurs in (b) shown in FIG. In this case, the electric charge stored in the capacitor is rapidly discharged in the loop shown by the arrow, so that the high voltage for energizing the magnetron decreases,
As a result, the output voltage Vout ′ of the current detecting means 13 is
Vref> Vout ′ as shown in FIG.
And the driving circuit 6 can be stopped. Equivalent circuits that can be considered when sparks occur in (c) and (f) shown in FIG. 25 are as shown in FIGS. 13 and 14, respectively. Also in this case, for the same reason, the current detecting means 13
And the output voltage of the reference voltage generating circuit 12 is inverted, so that the driving circuit 6 can be stopped.

FIG. 15 shows an embodiment corresponding to the fourth invention of the present invention. FIG. 1 shows a configuration in which a comparator 10 compares an output of a first current detecting unit 15 for detecting a current obtained from a commercial power supply as a power supply source with an output of a second current detecting unit 13.

The first current detecting means 15 outputs a current obtained from a commercial power supply as a voltage, a current transformer, a diode for rectifying the output of the current transformer, and a DC voltage rectified by the diode. It is composed of a resistor and a capacitor provided to extract the divided voltage as an average amount.

The second current detecting means 13 measures the magnitude of the current flowing to the anode of the diode which has the same potential as the chassis potential (the chassis of the high-frequency heating device is grounded) constituting the high-voltage rectifier circuit 5 of the full-wave rectification system. From a current transformer that outputs a voltage as a voltage, a diode that rectifies the output of the current transformer, a resistor that divides the DC voltage rectified by the diode, and a capacitor that is provided to take out the divided voltage as an average amount. Be composed.

The resistance R constituting the first current detecting means 15
When charging C1 with 1, R2, and C1, the constant τ1 is represented by τ1 = C1 * R1, and similarly, the time constant for charging C2 with the resistors R3, R4, and C2 constituting the second current detecting means 13. τ2 is represented by τ2 = C2 * R3. These time constants are set so that τ1 <τ2. Also, the output voltage V1 of the first current detecting means 15 and the second current detecting means 13
Are set such that the relationship of V2> V1 shown in FIG. 16 is satisfied. (The average amount of the input current is proportional to the average amount of the diode current.)
When a spark occurs in the high-voltage circuit portion shown in FIG. 5, the impedance from the primary side to the secondary side of the transformer 4 sharply decreases, and as a result, the input current sharply increases. The voltage V1 'increases rapidly. On the other hand, in the high voltage circuit portion shown in FIG.
In the sparks shown in (a), (b), (c) and (f) , the output voltage V2 'of the second current detecting means 13 decreases, so that the relationship shown in FIG. it can.

The high voltage circuit shown in FIG.
In (d), (e), (g), and (h), the output voltage V2 '"of the second current detecting means 13 increases and the output voltage V1'" of the first current detecting means 15 also increases. However, since the time constant of each current detecting means is larger than the time constant of the first current detecting means 15 as shown in the equation (6), the change of the output voltage V1 '' is
It is faster than the change of 2 ''. Therefore, V1 ″> V
2 ″ is obtained, and the voltage relationship is inverted at the output as compared with the equation (7), so that the drive circuit 6 can be stopped.

FIG. 18 shows an embodiment corresponding to the fifth invention of the present invention. In the figure, a comparator 16 compares a current detecting means 15 for detecting a current obtained from a commercial power supply as a power supply source with an output voltage of a reference voltage generating circuit 12.

The reference voltage generating circuit 12 has the same configuration as that of the embodiment according to the second aspect of the present invention. The output of the comparator 16 is transmitted to the drive circuit 6 via the timer circuit 17. The timer circuit 17 is set for a time of about 10 seconds. This time is about twice as long as the time required from the start of the inverter circuit to the oscillation of the magnetron. Therefore, the output of the comparator 16 is not transmitted to the drive circuit 6 within about 10 seconds. Thus, the timer circuit 1
The reason for using 7 is to prevent malfunction during this period because the input current is extremely small until the magnetron oscillates.

The comparator 16 has a first comparing means 18 and a second comparing means 19, and each of the comparing means is supplied with a reference voltage from the reference voltage generating circuit 12, so that the first comparing means 18 is provided. Is a first reference voltage, and a reference voltage supplied to the second comparing means 19 is a second reference voltage. The second reference voltage is about 0.6 volts lower than the first reference voltage because it has a voltage drop of one diode.

The current detecting means 15 has the same configuration as the first current detecting means 15 of FIG. 15 showing an embodiment corresponding to the fourth invention of the present invention. FIG. 19 shows the relationship between the output (magnetron output) of the output voltage Vref1 of the first reference voltage, the output voltage Vref2 of the second reference voltage, and the output voltage Vout of the current detection means 15 during normal operation. In the figure, Vref1>Vout> Vref
There are two relationships.

Here, "the problem to be solved by the invention"
However, as described above, if the lead wire 22 used to connect the magnetron 2 to the step-up transformer 4 or the high-voltage rectifier circuit 5 is forgotten to be connected, the input current will not exceed the time required for the magnetron to oscillate after startup. Not flowing. Therefore, the output voltage Vout of the current detecting means 14 becomes Vout ′ shown in FIG. 19, so that the output of the comparator 18 is inverted and the drive circuit 6 can be stopped.

When a spark is generated in the high voltage portion or when a spark is generated in the high voltage portion, the impedance as viewed from the primary side of the step-up transformer decreases, and as a result, the input current sharply increases. In this case, the current detecting means 1
4 becomes Vout ″ shown in FIG. 19, the output of the comparator 19 is inverted, and the drive circuit 6 can be stopped.

[0044]

As described above, the inventions according to claims 1 and 2 are described.
According to this, it is possible to effectively know the occurrence of a spark. In particular, according to the second aspect of the present invention, there is an effect that it is possible to detect forgetting to connect a lead wire used for connecting a magnetron to a step-up transformer or a high-voltage rectifier circuit. This utilizes a phenomenon that, when the lead wire is forgotten to be connected, the input current does not flow even after the time required for the magnetron to oscillate after startup.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a power supply configuration of a high-frequency heating device according to one embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining the invention.

FIG. 3 is a circuit diagram showing a power supply configuration of a high-frequency heating device according to another embodiment of the present invention.

FIG. 4 is a characteristic diagram for explaining the present invention.

FIG. 5 is a circuit diagram for explaining the invention.

FIG. 6 is a circuit diagram for explaining the invention.

FIG. 7 is a circuit diagram for explaining the present invention.

FIG. 8 is a circuit diagram for explaining the invention.

FIG. 9 is a circuit diagram showing a power supply configuration of a high-frequency heating device according to another embodiment of the present invention.

FIG. 10 is a characteristic diagram for explaining the present invention.

FIG. 11 is a circuit diagram for explaining the present invention.

FIG. 12 is a circuit diagram for explaining the present invention.

FIG. 13 is a circuit diagram for explaining the present invention.

FIG. 14 is a circuit diagram for explaining the present invention.

FIG. 15 is a circuit diagram showing a power supply configuration of a high-frequency heating device according to another embodiment of the present invention.

FIG. 16 is a characteristic diagram for explaining the present invention.

FIG. 17 is a characteristic diagram for explaining the present invention.

FIG. 18 is a circuit diagram showing a power supply configuration of a high-frequency heating device according to another embodiment of the present invention.

FIG. 19 is a characteristic diagram for explaining the present invention.

FIG. 20 is a circuit diagram showing a power supply configuration of a conventional high-frequency heating device.

FIG. 21 is an external perspective view showing a connection state between a magnetron and an inverter circuit.

FIG. 22 is a circuit diagram illustrating a conventional configuration.

FIG. 23 is a characteristic diagram for explaining conventional characteristics.

24A is a characteristic diagram of voltage and current of the half-wave voltage rectification method, and FIG. 24B is a characteristic diagram of voltage and current of the full-wave voltage rectification method.

FIG. 25 is a diagram showing locations where sparks may occur in the high-voltage rectifier circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inverter circuit 3 switching element 4 step-up transformer 5 high-voltage rectifier circuit 6 drive circuit 7 applied voltage detection circuit 8 reference voltage generation circuit 10 comparator 11 current detection means 12 reference voltage generation circuit 13 current detection means 14 comparator 15 first current Detecting means 16 comparator 18 first comparing means 19 second comparing means

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Haruo Suenaga 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshiro Ishio 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Toyotsugu Matsukura 1006 Okadoma Kadoma, Kadoma City Osaka Pref. Shiro Takeshita 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-4-32191 (JP, A) JP-A-1-313888 (JP, A) JP-A-1- 292790 (JP, A) JP-A-3-57192 (JP, A) JP-A-4-32190 (JP, A) JP-A-4-167394 (JP, A) JP-A-1-313887 (JP, A) Special Akira 61-18318 (JP, B2) (58 ) investigated the field (Int.Cl. ^7, DB name) H05B 6/66 - 6/68

Claims (2)

(57) [Claims] 1. A power supply, a first current detection circuit for detecting an average amount of current supplied from the power supply,
A switching element that converts DC power into high-frequency AC power; a boosting transformer that boosts the high-frequency AC power to a high voltage necessary for driving a magnetron; and a full-wave voltage doubler that rectifies the high-voltage AC power of the boosting transformer. A high-voltage rectifier circuit using a rectification method, a driving circuit of the switching element, and an average amount of current of at least one of the electric components that becomes a chassis potential among a plurality of electric components constituting the high-voltage rectifier circuit. A second current detection circuit and the first
The output of the current detection circuit and the output of the second current detection circuit
A comparator that outputs the calculation result to the drive circuit after the calculation
And a resistor and a resistor in the first current sensing circuit.
The time constant τ1 composed of a capacitor and the second current detection circuit
The time constant τ2 consisting of the resistor and the capacitor becomes τ1 <τ2
A high-frequency heating device configured to be . 2. A current detection circuit for detecting an average amount of current supplied from a power supply source, a switching element for converting DC power into high-frequency AC power, and a switching element required for driving the high-frequency AC power to a magnetron. A step-up transformer for stepping up to a high voltage, and a high-voltage rectifier circuit using a full-wave voltage doubler rectification method for rectifying high-voltage AC power of the step-up transformer,
A reference level generating circuit for changing the level according to the magnitude of the output; an output of the current detection circuit and an output of the reference level generating circuit.
The ratio of inputting force as input and outputting the operation result to the drive circuit after operation
And the predetermined time since the start of the inverter circuit
And a timer circuit that measures
After the measured predetermined time, the output of the reference level generation circuit
Calculate a certain output value 1 and a predetermined value different from the output value 1
And compares the output value 2 obtained from the current detection circuit with the output value.
Low impedance in the high voltage rectifier circuit or
Due to the disconnection between the Guntron and the step-up transformer,
The output value of the flow detection circuit deviates between output value 1 and output value 2.
Then, there is an inverter circuit for stopping the operation of the drive circuit.
High-frequency heating apparatus.