JP2927609B2 - 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 magnetron driving transformer for protecting a magnetron of an inverter type high frequency heating device such as a microwave oven, a control circuit system, and a control microcomputer control system. .

[0002]

2. Description of the Related Art An outline of a conventional high frequency heating apparatus for driving a magnetron with an inverter power supply will be described with reference to FIG.

[0003] A commercial power supply 1 is rectified by a rectifying bridge 2 and smoothed by a chiyo coil 3 and a smoothing capacitor 4 to form a rectifying and smoothing circuit 50.

A rectifying / smoothing circuit 50 is connected to a step-up transformer 6 (transformer) for driving a magnetron.
A resonance capacitor 5 is connected in series or in parallel (parallel in the drawing) to form a resonance circuit, and a semiconductor switching element 7 is connected to the resonance circuit to thereby form an inverter circuit 2.
9.

A high voltage diode 11 and a high voltage capacitor 12 are connected to a secondary circuit of the transformer 6 constituting the inverter circuit 29 to form a voltage doubler circuit.
This serves as a magnetron drive circuit, and a magnetron 10 is further connected.

[0006] The cathode of the magnetron 10 is connected to the secondary winding 22 of the transformer 6, and the cathode voltage of the magnetron 10 is connected to the control circuit 40 via the capacitor 12 and the secondary winding 22. By sending a signal to the drive circuit 30 by the circuit 40, the optimum control by feedback is performed. That is, the control circuit 40
In accordance with a magnetron output setting signal from the main control device 70 for controlling the entire system, the drive circuit 30 controls the output based on the detection result of the input / output voltage and current.
The driving pulse width and the driving timing of the semiconductor switching element 7 are adjusted through the control.

Here, the resistor 14 is for detecting a magnetron anode current, and the voltage across the resistor is input to the control circuit 40 as a current value.

The output of the control winding 24 is input to a control circuit 40 for synchronization and output voltage detection.

[0009] An input current of the high-frequency heating device is detected from a consumed current detection circuit 60 and input to the control circuit 40.

The above is the outline of the high-frequency heating device for driving the magnetron with the inverter power supply.

[0011]

In the conventional method, when an abnormal oscillation of the magnetron 10 occurs, the phenomenon is detected, the information is inputted to the control circuit 40, and the information is adjusted in accordance with the detected information. 10 does not have a protection function to stop the progress of characteristic deterioration.

Therefore, once the abnormal oscillation occurs, the self-heating becomes excessive and the anode temperature of the magnetron 10 rises rapidly, so that the magnetron 10 itself is destroyed.

In FIG. 14, the control winding 24 is provided for detecting the output voltage. However, since the above-described abnormality occurs rapidly, the control winding 24 disposed on the primary side is provided.
However, the detection was not sufficient and there was an inconvenience in practical use.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a high-frequency heating apparatus capable of preventing a rise in the anode temperature of a magnetron during abnormal oscillation and improving durability.

[0015]

As shown in FIGS. 1 and 8, a means for solving the problems according to the present invention comprises a magnetron 10 for high-frequency heating, a driving transformer 6 for supplying a step-up power to the magnetron 10, and An inverter circuit 29 connected to the primary side of the driving transformer 6, a driving circuit 30 for driving the switching element 7 of the inverter circuit 29, and a magnetron output setting signal supplied to the driving circuit 30 to provide the whole system. In a high-frequency heating device provided with a control device 70 for controlling the operation, a detection winding 25 for detecting the oscillation state of the magnetron 10 and the magnetron oscillation abnormality based on the output result _VA from the detection winding 25 And a drive stopping means 77 for outputting a signal for stopping the driving of the switching element 7. The detection winding 25 is connected to the magnetron cathode voltage. Of the secondary winding 2
2 is arranged on the secondary side of the driving transformer 6 so as to satisfy the same condition as 2 , and is wound more sparsely than the secondary winding 22 .

According to a second aspect of the present invention, there is provided a high-frequency heating apparatus according to the first aspect, wherein the driving stop means is provided.
7 is provided with drive return means 85 for prohibiting the output of the stop signal of 7 after a lapse of a certain period of time t ₂ -t ₃ and returning the driving of the switching element 7.

According to a third aspect of the present invention, there is provided a high-frequency heating apparatus according to the first or second aspect,
The stop signal output of the drive stopping means 77 is output to the magnetron 10
Is provided with a start-up transmission prohibiting means 86 for prohibiting the oscillation within a certain period ΔT at the time of the rise of the oscillation.

According to a fourth aspect of the present invention, in the high frequency heating apparatus according to the first, second, or third aspect , the oscillation state from the detection winding 25 is detected when the oscillation of the magnetron 10 rises. 2. A detection means 80a, and an abnormality detection counter 7 which counts an abnormal oscillation signal from the detecting means 80a and outputs an abnormal oscillation signal to the drive stopping means 77 according to claim 1 when the oscillation abnormal signal is continuously detected a plurality of times.
6 is provided.

The problem-solving means according to the invention claimed in claim 5, the detection winding 25 of claim 1 wherein, the core 6 of the traction transformer 6
This is disposed on the arm 6c on the secondary side of FIG.

According to a sixth aspect of the present invention, there is provided a high-frequency heating apparatus according to the first, second, or third aspect, wherein: a detecting means 80a for detecting an oscillation state from the detecting winding 25; A micro computer for judging whether the magnetron oscillation operation is normal or abnormal based on the oscillation abnormality signal from the means 80a, wherein the drive stopping means 77 is incorporated in the micro computer to stop the supply of the magnetron output setting signal. It is configured to do so.

[0021]

According to the first, fifth and sixth aspects of the present invention, since the detection winding 25 is disposed on the secondary side of the driving transformer 6, an output waveform similar to that of the secondary winding 22 is obtained. can get. Therefore, the oscillation state of the magnetron 10 can be detected more accurately than providing the detection winding 25 on the primary side. Therefore, when oscillation is abnormal, the output of the detection winding is
Thus, the differential fluctuation corresponding to the fluctuation of the cathode voltage of the magnetron 10 appears. Based on this, the driving stop means 77 outputs a stop signal to stop the driving of the switching element 7. Here, the detection winding 25 is less sparse than the secondary winding 22.
, The cathode to the drive stopping means 77
Reduce the effect of voltage fluctuations.

According to the second aspect, when the oscillation is abnormal, the control circuit
A stop signal to 0 to transmit a predetermined period _t 2 -t _3, the magnetron 10 is stopped for a certain period of time _t 2 -t _3. The transmission of the stop signal is prohibited by the drive return means 85. Then, not only can the magnetron 10 escape from the abnormal oscillation state, but also can automatically return to the normal oscillation state. Such an operation is performed every time abnormal oscillation of the magnetron 10 occurs.

According to the third aspect, when the magnetron 10 is started or restarted, the oscillation of the magnetron 10 becomes unstable. At this time, if the magnetron 10 is stopped many times by detecting the abnormal oscillation, the result is that the heating cannot be performed even if it waits for a long time. Therefore, during a certain period ΔT at the time of rising, transmission of a stop signal is prohibited by the transmission prohibiting means 86 at the time of starting, and the stop of the magnetron 10 is prevented. Carry out such an operation every time the abnormal oscillation of Ma Gunetoron 10 occurs.

According to the fourth aspect, a state similar to the abnormal oscillation is exhibited even during an unstable operation such as when the oscillation of the magnetron 10 rises. Therefore, the signal output for stopping the driving of the switching element 7 by the drive stopping means 77 is prohibited. In addition, considering the influence of noise, etc., if the protection function is operated only by one abnormal oscillation detection, it will cause malfunction, so it is judged that abnormal oscillation is the first time with multiple consecutive abnormal detections, and the accuracy of detection Improve. Carry out such an operation every time the abnormal oscillation of Ma Gunetoron 10 occurs.

[0025]

【Example】

(First Embodiment) FIG. 1 is a control block diagram of a high-frequency heating apparatus showing a first embodiment of the present invention, FIG. 2 is a side view showing an example of a driving transformer, and FIG. FIG. 4 is a waveform diagram showing the magnetron cathode voltage in the normal state and the corresponding detection winding output, FIG. 5 is a waveform diagram showing the magnetron cathode voltage in the abnormal state and the corresponding detection winding output, and FIG. FIG. 7 is a timing chart showing an abnormal oscillation signal and a gate signal at the time of rising, and FIG. 7 is a timing chart showing an abnormal oscillation signal and a gate signal at a normal time. FIG.
4, members having the same functions as those of the conventional example are denoted by the same reference numerals.

As shown in FIG. 1, a high-frequency heating apparatus (microwave oven) of the present embodiment includes a magnetron 10 for high-frequency heating,
The driving transformer 6 (transformer) having the secondary winding 22 connected to the magnetron 10 and the primary winding 21 connected to the inverter circuit 29, and the primary winding 21 of the driving transformer 6 A resonance capacitor 5 connected to form a resonance circuit; a switching element 7 connected to the primary winding 21 and the resonance capacitor 5; and an inverter circuit composed of the switching element 7 and the resonance circuit by rectifying and smoothing the commercial power supply 1 Rectifying / smoothing circuit 50 for supplying DC power to the power supply 29
A driving circuit 30 for driving the switching element 7
A control circuit 40 for controlling the drive circuit 30; and a main control device 70 for supplying a magnetron output setting signal to the control circuit 40 and controlling the operation of the entire system.

The driving transformer 6 is, as shown in FIGS.
A bobbin 6b divided and formed in a plurality of stages is attached to a core 6a having a rectangular shape in cross section, a primary winding 21 is wound around one region of the bobbin 6b, and a secondary winding 22 is wound around another region of the bobbin 6b. It is wound.

In FIG. 1, reference numeral 11 denotes a high-voltage diode, and 12 denotes a high-voltage capacitor, which are connected to form a voltage doubler circuit as a magnetron drive circuit.

Reference numeral 14 denotes a resistor for detecting a magnetron anode current. The voltage across the resistor 14 is input to the control circuit 40 as a current value.

When the current value becomes larger than the predetermined value, the control circuit 40 stops driving the switching element 7. Since only the current value is detected from the resistor 14, abnormal oscillation of the magnetron 10 cannot be detected.

Reference numeral 23 denotes a heat winding for heating the magnetron 10. The cathode of the magnetron 10 is connected to the heat winding 23, and the cathode voltage of the magnetron 10 is controlled by a signal from the control circuit 40.

Further, reference numeral 24 denotes a primary control winding inputted to the control circuit 40 for synchronization and output voltage detection.

[0033] Then, the in traction transformer 6 includes a detection coil 25 for detecting the oscillation state of the magnetron 10, the drive control circuit 40 when the oscillation abnormality based on the output result V _A from該検Demaki line 25 And a detection winding output shaping circuit 80 for transmitting a reset pulse as a stop signal for stopping the operation. The output shaping circuit 80 and the control circuit 40 constitute a drive stopping means 77.

As shown in FIGS. 2 and 3, the detection winding 25 is arranged in parallel with the secondary winding 22 in a region on the secondary side of the bobbin 6b, and as shown in FIGS. The output fluctuation of the cathode voltage is differentially extracted.
5 is connected to the output shaping circuit 80.

[0035] The detection coil output shaping circuit 80, as shown in FIG. 1, the peak of V _A peak value is compared with Suretsushiyu voltage value V _N of the reference value voltage V _A from the detection winding 25 side V _N A comparison circuit 81 that determines that the magnetron is in an abnormal oscillation state when the comparison circuit 81
Signal (reset pulse) to the switching element 7 based on the determination result (abnormal magnetron oscillation signal)
A pulse generating circuit 84 that transmits a certain period a stop signal at the pulse generation circuit 84 when the oscillation abnormality (t in FIG. 7 ₂ -
t ₃ between) the reset circuit 85 as a driving return means for returning the driving of the switching-element 7 prohibits the transmission after transmitting, said predetermined period of time oscillation rise of the magnetron 10 (t ₃ in FIG. 7 -t (For about 5 seconds between ₄ ), a start-up transmission inhibiting means 86 for inhibiting the transmission of the stop signal of the pulse generation circuit 84.

As the comparison circuit 81 (comparator) and AND circuit 82, a general differential amplifier is used.

The pulse generating circuit 84 is, as shown in FIG.
A stop signal (reset pulse) is transmitted to the control circuit 40 to perform off control.

The reset circuit 85 has a timer, and outputs a prohibition signal to the pulse generation circuit 84 after a lapse of a certain period of time t ₂ -t ₃ from the time when the stop signal of the pulse generation circuit 84 is transmitted. The period t ₂ -t ₃ is set to about 5 seconds. However, if the magnet rises immediately thereafter, the magnetron abnormally oscillates as described later, so that overheating of the magnetron is prevented. A sufficient period is taken for the cooling.

The start-up transmission inhibiting means 86 is introduced for the following purpose. That is, as shown in FIG. 6, during the period of ΔT from the start of oscillation, the magnetron oscillation operation becomes unstable.
The object of the present invention is to ensure the driving of the magnetron 10 and to prohibit the magnetron 10 from stopping at the time of startup.

That is, the start-up transmission prohibiting means 86 reads the magnetron output setting signal from the main controller 70, delays it by ΔT, and outputs it as a gate signal. And a logical AND circuit 82 for transmitting the determination result from the pulse generation circuit 84 to the pulse generation circuit 84 in synchronization with the gate signal from the delay signal generation circuit 83. Therefore, during the magnetron oscillation rising transition period ΔT, the gate signal is not output from the delay signal generation circuit 83 and the abnormal oscillation signal (pulse generation trigger signal) is not output from the AND circuit 82. This period ΔT is because if the abnormal oscillation state continues for a long time, the magnetron 10 is overheated and destroyed, so that it takes about 5 seconds.

The inverter circuit 29 is composed of a connection composed of the switching element 7, the resonance capacitor 5, and the primary winding 21.

The rectifying / smoothing circuit 50 rectifies the commercial power supply 1 with a rectifying bridge 2 and smoothes the rectified smoothing with a chiyo coil 3 and a smoothing capacitor 4.

The control circuit 40 includes a main controller 70
Is connected to a pulse generator circuit 84 of the detection winding output shaping circuit 80, and a stop signal is supplied to the control winding 24.
The driving of the switching element 7 is controlled via the drive circuit 30 so that the magnetron 10 oscillates at the output given by the output setting signal in synchronization with the signal from the control circuit. That is, when the stop signal is not supplied, the switching element 7 is driven in response to the supply of the magnetron output setting signal. 7 is stopped.

The main control device 70 receives a signal from an operation button of an operation section of the high-frequency heating device, displays this information on a display panel, and sends a magnetron output setting signal to the control circuit 40 when the magnetron 10 is driven. Send

The detection winding output shaping circuit 80 and the control circuit 40 use a circuit unit having a plurality of elements mounted on a substrate such as an IC.
Common micro competent Yu <br/> over data having a ROM and a RAM is used.

In FIG. 1, reference numeral 60 denotes a consumed current detecting circuit for detecting an input current of the high frequency heating device and inputting the detected current to the control circuit 40.

The high-frequency heating device having the above configuration operates as follows. First, the current supplied from the commercial power supply via the rectifying / smoothing circuit 50 is turned on / off by the switching element 7 of the inverter circuit 29, whereby the resonance circuit is resonated, and the power is supplied to the magnetron 10 via the driving transformer 6. Supply.

At this time, the output of the detection winding 25 is input to the comparison circuit 81 of the detection winding output shaping circuit 80, and as shown in FIG.
In response to the detection coil output peak value of the normal oscillation, compared with Suretsushiyu a predetermined voltage value V _N.

[0049] Here, in the normal state as shown in FIG. 4, V _N is because it is larger than the detection winding output, the comparison circuit 81 outputs nothing.

[0050] However, as shown in FIG. 5, abnormal oscillation sometimes the peak voltage level _{V A,} so is V A> _{V N,} the comparison circuit 81 outputs "H" signal, the signal AND circuit 8
Input to 2. That is, this output signal becomes a magnetron abnormal oscillation signal.

If this time is a predetermined period ΔT when the magnetron oscillation rises, the delay signal generation circuit 83
Therefore, as shown in FIG. 6, the abnormal oscillation signal is blocked by the AND circuit 82 to prevent the signal from proceeding to the next stage. This prevents the magnetron 10 from being stopped by mistake.

On the other hand, this time is a certain period of rise Δ
After the lapse of T, as shown in FIG. 7, the gate signal is supplied from the delay signal generation circuit 83 to the AND circuit 82, and the abnormal oscillation signal is supplied to the pulse generation circuit 84.

The abnormal oscillation signal that has passed through the logical product circuit 82 is a pulse generation trigger signal for the pulse generation circuit 84, which generates a stop signal to the control circuit 40.

At this point, the control circuit 40 continues to supply the magnetron output setting signal from the main control unit 70, but changes the switching element drive signal to the drive circuit 30 to the drive circuit 30 for a certain period of time t ₂ based on the stop signal. -t ₃ stops, oscillation of the magnetron 10 is stopped to prevent destruction by overheating of the magnetron 10 by the abnormal oscillation.

After a certain period of time t ₂ -t _{3 has} elapsed, the stop signal (reset pulse) from the pulse generation circuit 84 is inhibited by the signal from the reset circuit 85. Then, the control circuit 40 supplies the switching element drive signal to the drive circuit 30 again based on the output setting signal, and
The oscillation of 10 is restarted.

At the time of the rise of the re-oscillation, the output of the pulse generating circuit 84 is connected to the delay signal generating circuit 83, so that a predetermined period ΔT after the elapse of the stop period t ₂ -t _3.
(About 5 seconds), as described above, the detection winding output shaping circuit 8
No gate signal is transmitted from the 0 delay signal generating circuit 83. That is, as shown in FIG.
The output of 3 is a total period _TG of the magnetron stop period t ₂ -t ₃ due to the occurrence of abnormal oscillation and the period t ₃ -t ₄ = ΔT from the start of re-oscillation until the operation is stabilized. Stop for a while.

The above operation is repeated every time an abnormal oscillation occurs, so that the magnetron 10 can automatically escape from the abnormal oscillation. Moreover, magnetron 10
Prevents self-destruction and contributes to extending operating life.

(Second Embodiment) FIG. 8 is a control block diagram of a high-frequency heating apparatus according to a second embodiment of the present invention, and FIG. 9 is a waveform diagram showing a magnetron cathode voltage and a corresponding detection winding output at the time of abnormality. FIG. 10 is a waveform diagram showing a state of occurrence of an abnormal oscillation signal, and FIG. 11 is a control flowchart of the main control device. Note that members having the same functions as those of the conventional example of FIG.

As shown in FIG. 8, in the high-frequency heating device of the present embodiment, the main control device 70 for supplying the magnetron output setting signal to the switching element 7 has a magnetron protection function at the time of detecting abnormal oscillation. Things.

[0060] As the main controller 70, when driving the magnetron 10, the control circuit 40 as to transmit the micro output setting signal, the first embodiment and the same general control micro competent Yoo over data unit A key input device 73 for operating the device 71 and a control micro-computer
It is connected to a display device 72 for displaying the information in response to a signal from Yu over data section 71.

[0061] Then, the control micro competent Yoo over data unit 71, based on the output result V _A from the detection winding 25 are connected to the detection coil output shaping circuit 80a for detecting the oscillation abnormal state, the control circuit 40 Output setting signal transmitting means 74 for transmitting a micro output setting signal to the
A determining means 75 for determining whether or not the oscillation operation of the magnetron 10 is in a normal state based on the magnetron abnormal oscillation signal returned from 0a, and outputting an abnormal signal when the result of the determination is abnormal; When an abnormal signal is continuously input a plurality of times (three times), an abnormal detection counter 76 that outputs an abnormal detection signal for the first time, and an output setting signal transmitting unit 74 based on the abnormal detection signal from the abnormal detection counter 76 And a driving stop means 77 for outputting a signal for stopping the driving. As in the first embodiment, a drive return unit 85 and a transmission prohibiting unit 86 are provided.

[0062] The determining means 75, as shown in FIG. 9, is set in advance abnormal oscillation determined Suretsushiyureberu voltage V _TH, and the Suretsushiyureberu voltage V _TH, abnormal oscillation from the detection winding output shaping circuit 80a If the voltage value of the abnormal oscillation signal is higher than V _TH , it is determined that the oscillation is normal, and if the voltage value is equal to or lower than V _TH , it is determined that the oscillation is abnormal.

As shown in FIG. 11, the abnormality detection counter 76 counts up each time an abnormality is detected by the judging means 75, and when the abnormality is detected three times, the driving stop means 77 is activated.
Turn on.

The output setting signal transmitting means 74 and the judging means 7
5. The operations of the abnormality detection counter 76, the drive stopping means 77, the drive returning means 85, and the transmission inhibiting means 86 are driven based on a program in the ROM.

The detection winding output shaping circuit 80a as the detection means is provided for detecting the winding 2 when abnormal magnetron oscillation occurs.
A diode 91 for cutting the negative side (-) of the output of the output terminal 5;
A Zener diode 92 which is substantially equal to the connected Zener voltage V _Z is the detection winding output peak value V _N of the normal oscillation the diode 91, the Zener diode 9
Having a base connected transistor 93 to 2, and a capacitor 94 interposed between the collector electrode and ground of the transistor 93.

[0066] Then, with the capacitor 94, to the connection point of the collector electrode of the transistor 93, the power supply _{V C} is connected via a resistor 95.

The other configuration is the same as that of the first embodiment, and the description is omitted.

The output waveform shown in FIG. 9 is a waveform extracted from the points (1) to (5) in FIG.

In the above configuration, when an abnormal oscillation occurs in the magnetron 10, the output of the detection winding 25 is cut by the diode 91 on the negative side (-) as shown in FIG.

Next, the detection winding output shaping circuit 80a, Zener voltage _{V Z} of the Zener diode 92,
Since the set substantially equal to the detection winding output peak value V _N of the normal oscillation, as shown in the figure, the voltage is not applied except when the abnormal oscillation to the base of the transistor 93.

By the way, the capacitor 94, the charge through the resistor 95 from _{V C} is charged, the voltage across Upon successful oscillation, shows a substantially _{V C.} Then, the voltage across V _C is transmitted to the main control unit 70.

On the other hand, when an abnormal oscillation occurs, the base voltage of the transistor 93 is applied as shown in FIG. 9 and the transistor 93 is driven, so that the electric charge charged in the capacitor 94 causes the transistor 93 to operate. Discharge through.

Then, during normal oscillation, the voltage V _C across capacitor 94 transmitted to main controller 70 is transmitted.
Is cut off. This becomes an abnormal oscillation signal.

[0074] Further, there is no base voltage of the transistor 93, the transistor 93 is turned OFF, the power source _{V C} to charge the transistor 93 again via resistor 95.

In this case, the main control device 70
The signal inside is input as an abnormal oscillation signal. And
As shown in FIG. 10, the judging means 75 looks for an abnormal oscillation signal at a timing synchronized with the frequency of the commercial power supply, and compares the abnormal oscillation signal at this time with the abnormal oscillation occurrence judgment threshold level voltage V _TH . comparison, the voltage value of the abnormal oscillation signal is determined to be normal oscillation mode is greater than V _TH. On the other hand, if the voltage value is equal to or lower than _VTH , it is determined that abnormal oscillation has occurred.

In such a case, a single noise or the like may be detected. However, if the protection function is operated only by detecting the abnormal oscillation once and the device is stopped each time,
This may cause malfunction and drive the device inefficiently .

Therefore, as shown in FIG. 11, a signal is output to the drive stopping means 77 as an abnormal oscillation state only when this abnormality detection is continuously performed a plurality of times (three times). Then, it is possible to prevent the magnetron 10 from being stopped until it immediately returns to the normal state with only one abnormality due to the influence of noise or the like. Control may be exercised.

[0078] Incidentally, during unstable operation such as during oscillation rise of the magnetron 10, so exhibits the same state as when filed even abnormal oscillation is normal, Yotsute during transmission prohibiting means 86 rise, the drive stop means 77 Operation is prohibited.

[0079] Then, the output setting signal transmission means 74, drive
Based on the signal from the operation stopping means 77, the micro output setting signal to the control circuit 40 is stopped, the oscillation of the magnetron 10 is stopped, and the progress of the characteristic deterioration due to the abnormal oscillation is temporarily stopped.

After stopping for a certain period of time t ₂ -t ₃ , the output setting signal transmitting means 74 is brought into a normal operation state by the drive return means 85, and the micro output setting signal is supplied again to start the oscillation of the magnetron 10.

The above operation is repeated each time abnormal oscillation occurs, as in the previous example.

The present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention.

For example, in FIGS.
Is provided in parallel with the secondary winding 22, but instead of this,
As shown in FIGS. 12 and 13, the detection winding 25 may be configured to be pulled out above the opposite side of the primary winding 21 at the arm 6c portion of the core 6b. Here, FIG. 12 is a side view showing a traction transformer, 13 is a B-B sectional view of FIG. 12.

In the second embodiment, the abnormality detection counter 7
6 is provided inside the main control device 70, but may be incorporated in the drive stop means 77 or the control circuit 40, for example.

[0085]

As is apparent from the above description, according to the first, fifth, and sixth aspects of the present invention, since the detection winding is on the secondary side of the driving transformer, it is abrupt under the same conditions as the secondary winding. The magnetron oscillation abnormality can be detected with high accuracy, the magnetron can be prevented from being overheated at an early stage, and its destruction can be prevented. Also detect
Since the winding is wound loosely compared to the secondary winding,
The influence of the fluctuation of the cathode voltage on the stopping means can be reduced,
Abnormality can be reliably detected.

According to the second aspect of the present invention, the magnetron can be automatically returned again after a certain period of time after the magnetron is stopped after the abnormal transmission by the drive return means, so that even if an oscillation abnormality occurs, there is no burden on the user. Without providing, a desired high-frequency heating operation can be performed. Moreover, since the return operation is performed after a certain period of time after the magnetron is stopped, the magnetron is restarted after being cooled, and the life of the magnetron can be extended.

According to the third aspect of the present invention, the start-up transmission inhibiting means does not stop the operation of the magnetron at the rising edge when the oscillation of the magnetron becomes unstable. The rising of the heating operation can be secured.

According to the fourth aspect of the present invention, the magnetron
At the rising edge when oscillation becomes unstable, abnormal oscillation is determined for the first time by detecting multiple abnormalities continuously, so the magnetron does not stop even if it malfunctions momentarily due to noise etc. effective.

[Brief description of the drawings]

FIG. 1 is a control block diagram of a high-frequency heating device showing a first embodiment of the present invention.

FIG. 2 is a side view showing an example of a driving transformer.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a waveform chart showing a magnetron cathode voltage and a corresponding detection winding output in a normal state.

FIG. 5 is a waveform chart showing a magnetron cathode voltage and a detection winding output corresponding to the magnetron cathode voltage at the time of abnormality.

FIG. 6 is a timing chart showing an abnormal oscillation signal and a gate signal at the time of oscillation rising;

FIG. 7 is a timing chart showing a normal abnormal oscillation signal and a gate signal.

FIG. 8 is a control block diagram of a high-frequency heating device showing a second embodiment of the present invention.

FIG. 9 is a waveform diagram showing the magnetron cathode voltage and the corresponding detection winding output at the time of an abnormality.

FIG. 10 is a waveform chart showing a state of occurrence of an abnormal oscillation signal.

FIG. 11 is a control flowchart of the main control device.

FIG. 12 is a side view showing a driving transformer.

13 is a sectional view taken along line BB of FIG.

FIG. 14 is a control block diagram of a conventional high-frequency heating device.

[Explanation of symbols]

 Reference Signs List 6 driving transformer 7 switching element 10 magnetron 21 primary winding 22 secondary winding 25 detection winding 29 inverter circuit 30 drive circuit 40 control circuit 70 main control device 76 abnormality detection counter 77 drive stop means 80, 80a detection winding Output shaping circuit 81 Comparison circuit 82 Logical product circuit 84 Pulse generation circuit 85 Driving recovery means 86 Startup prohibition means

────────────────────────────────────────────────── ─── Continuation of front page (72) Yoshikazu Yamamoto, Inventor 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-3-78995 (JP, A) JP-A-1- 159995 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B ⁶ /64-6/68 F24C 7/02

Claims (6)

(57) [Claims] 1. A high-frequency heating magnetron, a driving transformer for supplying step-up power to the magnetron, an inverter circuit connected to a primary side of the driving transformer, and a switching element of the inverter circuit. A drive circuit;
A high-frequency heating device comprising: a control device that supplies a magnetron output setting signal to the drive circuit to control the operation of the entire system; and a detection winding that detects an oscillation state of the magnetron, and an output from the detection winding. Drive stopping means for outputting a signal for stopping driving of the switching element at the time of magnetron oscillation abnormality based on the result,
The detection winding is arranged on the secondary side of the driving transformer so as to obtain the same condition as the secondary winding by differentially capturing the fluctuation of the magnetron cathode voltage , and is less sparse than the secondary winding. To
A high-frequency heating device which is wound . 2. The high-frequency heating apparatus according to claim 1, further comprising a drive return unit that inhibits the output of the stop signal of the drive stop unit after a lapse of a predetermined period and returns the driving of the switching element. High frequency heating device. 3. The high-frequency heating apparatus according to claim 1, further comprising a start-up transmission prohibiting unit that prohibits a stop signal output of the drive stop unit during a certain period of time when the magnetron rises. A high-frequency heating device, characterized in that: 4. The high-frequency heating device according to claim 1, 2 or 3, wherein the magnetron oscillates at the start of oscillation.
Sometimes, detecting means for detecting the oscillation state from the detection winding,
2. A high-frequency heating apparatus according to claim 1, further comprising an abnormality detection counter for outputting an abnormal oscillation signal to said drive stop means when said oscillation abnormal signal from said detecting means is counted and when the oscillation abnormal signal is detected a plurality of times continuously. apparatus. 5. The high-frequency heating device according to claim 1, wherein the detection winding according to claim 1 is disposed on a secondary arm portion of a core of the driving transformer. 6. A high-frequency heating device according to claim 1, wherein said detecting means detects an oscillating state from said detecting winding, and said magnetron oscillating operation is performed by an oscillating abnormal signal from said detecting means. 2. A high-frequency heating apparatus according to claim 1, further comprising: a micro-computer for judging whether the operation is normal or abnormal, wherein the driving stop means according to claim 1 is incorporated in the micro-computer and stops supplying the magnetron output setting signal. apparatus.