JPH0935867A - Combined cooking device - Google Patents

Abstract

(57) [Abstract] [Purpose] If the secondary high-voltage side of the step-up transformer is in an abnormal state such as discharge for some reason, it provides a combined cooker that can detect the abnormal state and stop the inverter circuit. To do. [Arrangement] Abnormality judging means 1 for judging an abnormality by comparing outputs of an input current detecting means 14 and a collector voltage detecting means 15.
6 is provided and the output thereof is input to the output control unit 11 to stop the inverter circuit 2 when the secondary high voltage side of the step-up transformer 4 is in an abnormal state such as discharge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined cooker for performing cooking by using induction heating with a heating coil and microwave heating with magnetron oscillation.

[0002]

2. Description of the Related Art A conventional combined heating cooker will be described below with reference to FIG.

Unidirectional power source 1 obtained by rectifying a commercial power source
In addition, one end of an inverter circuit 2 including a smoothing circuit having a function of preventing noise generated by switching from being superimposed on a power supply line is provided with a changeover switch 6 at a heating coil 3 and a step-up transformer 4 for applying a high voltage to a magnetron 5. Connected through. The secondary side of the step-up transformer 4 is voltage-doubled and rectified by a capacitor and a diode, and a high voltage of about 4 kV is applied to the magnetron 5. Step-up transformer 4
Output current is detected by the output current detection means 10 configured by the first current transformer 8 and the first rectifier circuit 9 that rectifies the output, and the input current from the commercial power source is the second current transformer. 12 and a second rectifying circuit 13 for rectifying the output thereof is detected by the input current detecting means 14. Further, the output current and the detected value of the input current are input to the output control unit 11 to control the required conduction time of the switching element 7 of the inverter circuit 2. Also,
The collector-emitter voltage of the switching element 7 is input to the output control section 11 via the collector voltage detecting means 15, and during induction heating, the outputs of the input current detecting means 14 and the collector voltage detecting means 15 are compared with each other to be heated. It is determined whether or not the load is present and whether the load is appropriate. The output control section 11 can also control the conduction time of the switching element 7 so that the output of the collector voltage detection means 15 becomes constant.

With the above configuration, the changeover switch 6 is provided as necessary.
Can be switched to induction-heat the object to be heated with the high-frequency power from the inverter circuit 2 via the heating coil 3, or microwaves can be generated from the magnetron 5 to heat the object to be heated. Here, the input power is controlled at a constant level by the output of the input current detecting means 14 during the induction heating and by the output of the output current detecting means 10 of the step-up transformer 4 during the microwave heating.

[0005]

However, the composite heating cooker having the above-mentioned conventional structure has the following problems. That is, when the magnetron 5 is used, it is necessary to perform constant control of the anode current in order to prevent abnormal oscillation called moding. At this time, the inverter circuit 2 has priority over the input current detection means 14 and the output current detection means. Since the conduction time of the switching element 7 is controlled by the output of 10, if the secondary high voltage side of the step-up transformer 4 is discharged for some reason, no power is supplied to the magnetron 5 and the input current becomes small. Current continues to flow on the secondary high voltage side. Therefore, the output control unit 11 does not recognize that an abnormality has occurred, and the inverter circuit 2 continues to operate according to the output from the output current detection unit 10. Therefore, there is a problem that the secondary high voltage side is likely to continue to be discharged.

The present invention solves the above-mentioned conventional problems. Power is supplied by performing constant control of the input current during induction heating by the heating coil and by performing constant control of the anode current during normal operation of the magnetron. In addition, when the secondary high-voltage side of the step-up transformer is discharged for some reason, an abnormality is detected, and the controller for the combined heating cooker that detects the abnormality and stops the inverter circuit is provided.
The purpose is.

A second object of the present invention is to make it possible to detect a discharge abnormality on the secondary high voltage side of the step-up transformer in a state where the degree of freedom in designing the abnormality determining means and its peripheral circuits is widened. .

A third object of the present invention is to make it possible to detect an abnormal condition such as a discharge on the secondary high voltage side of the step-up transformer with higher accuracy.

Further, even when the magnetron is not oscillated, an abnormality such as discharge on the secondary high voltage side of the step-up transformer is caused.
The fourth purpose is to detect with higher accuracy.

[0010]

In order to achieve the above first object, the present invention is an inverter circuit for converting a commercial power source into high frequency power using a switching element, and a heating coil for induction heating an object to be heated. A magnetron for generating microwaves, a step-up transformer for generating high-voltage power in the magnetron, a changeover switch for switching power supply from the inverter circuit between the heating coil and the step-up transformer, and an input from the commercial power supply. An input current detecting means for detecting a current, an output current detecting means for detecting an output current of the step-up transformer, a collector voltage detecting means for detecting a collector voltage of the switching element, and at least an output of the output current detecting means. And an output control unit for controlling the conduction time of the switching element. It is made to stop the inverter circuit in response to the comparison output of the input current detecting means and the collector voltage detection means.

In order to achieve the second object,
The present invention relates to an inverter circuit that converts a commercial power source into high frequency power using a switching element, a heating coil that induction-heats an object to be heated, a magnetron that generates microwaves, and a step-up transformer that generates high-voltage power to the magnetron. , A changeover switch for switching power supply from the inverter circuit between the heating coil and the step-up transformer, input current detection means for detecting an input current from the commercial power supply, and an output for detecting an output current of the step-up transformer. A current detection unit and an output control unit that controls the conduction time of the switching element according to at least the output of the output current detection unit, and the output control unit compares the input current detection unit with a predetermined reference voltage. According to the above, the inverter circuit is stopped.

Further, in order to achieve the third object,
The output control section of the present invention controls the conduction time of the switching element particularly in accordance with the outputs of the input current detecting means and the output current detecting means.

Further, a step-up transformer having a detection winding as an anode voltage detecting means of the magnetron is provided, and the output control section is prioritized over the output of the input current detecting means in the non-oscillating state of the magnetron at the time of starting the inverter. The fourth object is achieved by making the voltage detection means the input object of the comparison output.

[0014]

According to the present invention, when the power is supplied to the magnetron, when the secondary high voltage side of the step-up transformer is discharged for some reason, the output of the collector voltage detecting means and the input current detecting means causes the inverter circuit to operate. It is possible to significantly improve the safety of the parts and the like that make up the high voltage circuit by acting to stop the operation of.

Further, by providing the reference voltage to be compared with the anode voltage detecting means and the input current detecting means, it is possible to detect the abnormality without considering the change of the collector voltage during the induction heating and the microwave heating. The degree of freedom in designing the abnormality determination unit and its peripheral circuits can be expanded.

Further, the output control section is configured to control the conduction time of the switching element according to the output of the input current detecting means and the output current detecting means, so that the discharge on the secondary high voltage side of the step-up transformer is performed. Such an abnormality can be detected more accurately.

Further, the step-up transformer having a detection winding as an anode voltage detecting means of the magnetron is provided, and the output control section gives priority to the output of the input current detecting means in the non-oscillating state of the magnetron at the time of starting the inverter. By setting the voltage detection means as the input target of the comparison output, it is possible to accurately detect an abnormality such as discharge on the secondary high voltage side of the step-up transformer when the magnetron is not oscillating when the inverter is started.

[0018]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, a unidirectional power source 1 including a commercial power source and a rectifying bridge is connected to an inverter circuit 2 including a smoothing circuit that prevents power line noise due to switching. Inverter circuit 2
One end of is connected to a heating coil 3 and a step-up transformer 4 for applying a high voltage to a magnetron 5 via a changeover switch 6. The secondary side of the step-up transformer 4 is voltage-doubled and rectified by a capacitor and a diode, and a high voltage of about 4 kV is applied to the magnetron 5. During microwave heating due to the operation of the magnetron 5, the output current of the step-up transformer 4 is detected by the output current detection means 10 including the first current transformer 8 and the first rectifier circuit 9 that rectifies the output of the first current transformer 8. . Further, the detected value of the output current is input to the output control unit 11, and the switching element 7 of the inverter circuit 2 is controlled so that the anode current of the magnetron 5 becomes constant.
Control the required conduction time of the. In addition, the switching element 7
The collector-emitter voltage of the collector voltage detector means 1
Inverter circuit 2 so that the output of collector voltage detecting means 15 is input to output control section 11 via 5
The required conduction time of the switching element 7 is controlled. Further, the output of the input current detecting means 14 of the commercial power source is detected by the input current detecting means 14 constituted by the second current transformer 12 and the second rectifying circuit 13 for rectifying the output, and the output of the collector voltage detecting means 15 is detected. The abnormality determination unit 16 compares the output and the output, and outputs a signal for operating or stopping the inverter to the output control unit 11.

The operation of the composite cooker configured as described above will be described below. When the object to be heated is induction-heated, the inverter circuit 2 is connected to the heating coil 3 by the first changeover switch 6, but the output current does not flow through the first current transformer 8, so that the output of the collector voltage detecting means 15 is output. Is prioritized, and the required conduction time of the switching element 7 of the inverter circuit 2 is controlled so that the output of the collector voltage detection means 15 becomes constant. The output of the input current detecting means 14 becomes constant by controlling the output of the collector voltage detecting means 15 to be constant. When the object to be heated is microwave-heated, the inverter circuit 2 is connected to the step-up transformer 4 by the changeover switch 6, and the output control unit 1
1, the switching element 7 of the inverter circuit 2 is required so that the output current detected by the first current transformer 8, which is equivalent to the anode current of the magnetron 5 in preference to the output of the collector voltage detection means 15, becomes constant. The conduction time is controlled, and the magnetron 5 oscillates at a constant output. At this time, the output of the input current detecting means 14 is set to be larger than the output of the collector voltage detecting means 15. Even if the secondary high-voltage side of the step-up transformer 4 is discharged for some reason, the output of the output current detecting means 10 shown in FIG. 2 (b) is compared with the normal state (FIG. 2 (a)). Then, almost the same current flows through the current transformer 8 and the inverter circuit 2 tries to continue operating, so that the output of the collector voltage detecting means 15 reaches about 700 V which is almost the same as in the normal state. However, since the secondary high voltage side of the step-up transformer 4 does not reach the oscillation start voltage of the magnetron 5, the magnetron 5
2 is not supplied with electric power, the output of the input current detection means 14 of the commercial power source flowing through the second current transformer 12 becomes smaller than that in the normal state as shown in FIG. The output of the input current detection means 14 becomes smaller than the output of the collector voltage detection means 15, the abnormality determination means 16 inverts the output with respect to a normal state, and sends an operation stop signal of the inverter circuit 2 to the output control section 11.

As described above, according to this embodiment, the output of the input current detecting means 14 is indirectly controlled while the induction heating is performed by the heating coil 3, and the magnetron 5 is controlled.
By performing constant anode current control during normal operation of
Prevents abnormal oscillation called moding caused by an increase in anode current with temperature rise of magnetron 5,
When the secondary high voltage side of the step-up transformer 4 is discharged for some reason, the output of the input current detection means 14 and the output of the collector voltage detection means 15 are compared to detect the abnormality and the inverter circuit 2 is stopped. be able to.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG. FIG. 1
2 is different from that of FIG. 2 in that the second current transformer 12 has a plurality of outputs, a third rectifier circuit 27 is provided separately from the second rectifier circuit, and this output is connected to the output current detection means 10. , And both are configured to be input to the output control unit 11. The components other than the above are the same as those in the first embodiment, and the description thereof will be omitted.

The operation of the composite heating cooker configured as described above will be described below. In the present embodiment, the inverter circuit 2 is stopped by detecting an abnormality such as discharge on the secondary high voltage side of the step-up transformer 4 during microwave oscillation, and the object to be heated is placed during induction heating by the heating coil 3. Even if it is not opened or if it is an aluminum pot, this is surely detected and the inverter circuit 2 is stopped. Therefore, during normal operation of the magnetron 5 by microwave heating, the output control unit 11
Then, the input current detecting means 24 is prioritized so that the output current detected by the first current transformer 8, which is equivalent to the anode current of the magnetron 5, becomes constant, and the heating coil 3 appropriately heats the output current. During the induction heating of the object, the required conduction time of the switching element 7 of the inverter circuit 2 is controlled so that the output of the input current detecting means 14 detected by the second current transformer 12 becomes constant. Here, when an abnormality such as discharge occurs on the secondary high voltage side of the step-up transformer 4 during operation of the magnetron 5, the secondary high voltage side of the step-up transformer 4 does not reach the oscillation start voltage of the magnetron 5,
Since the magnetron 5 is not supplied with power, the second
The output of the input current detecting means 14 of the commercial power source flowing in the current transformer 12 becomes smaller than that in the normal state, and accordingly, the output of the input current detecting means 14 becomes smaller than the output of the collector voltage detecting means 15, resulting in an abnormality. The determination means 16 has its output inverted with respect to the normal state and sends an operation stop signal of the inverter circuit 2 to the output control section 11. Also, during induction heating,
In the case of an improper load such as no object to be heated or an aluminum pot, the power is not supplied to the load, so the output of the input current detecting means 14 becomes small, and the load is compared with the output of the collector voltage detecting means 15. Detect what is.

As described above, according to the present embodiment, the input current constant control is realized during the induction heating by the heating coil 3, while the anode current constant control is performed during the normal operation of the magnetron 5, so that the temperature of the magnetron 5 is controlled. The abnormal oscillation called moding caused by the increase of the anode current due to the rise is prevented, and the output of the input current detection means 14 and the collector voltage detection are detected when the secondary high voltage side of the step-up transformer 4 is discharged for some reason. The inverter circuit 2 detects the abnormality by comparing the outputs of the means 15.
It is possible to prevent the high voltage circuit from continuing to discharge by comparing the output of the input current detection means 14 and the output of the collector voltage detection means 15 during the induction heating to determine whether the load is appropriate. It is possible to provide a combined heating cooker that determines whether or not to do so.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to FIG. In Figure 3
2 is different from the circuit configuration in FIG. 1 in that a detection winding of several turns is provided on the secondary side of the step-up transformer 4 as the anode voltage detection means 28 of the magnetron 5, and its output is connected to the input current detection means 24, both of which are abnormal. The point is that the input is made to the determination means 16. Components other than the above are the same as those in the first embodiment, and a description thereof will be omitted.

The operation of the composite cooker configured as described above will be described below. In this embodiment, in addition to the steady oscillation of the magnetron 5 during microwave heating,
Particularly, when the inverter circuit 2 is started, an abnormality such as discharge on the secondary high voltage side of the step-up transformer 4 that occurs in the non-oscillation state of the magnetron 5 is detected, and the inverter circuit 2 is stopped. When the cathode is not sufficiently heated, the magnetron 5 exhibits a high impedance characteristic and remains in a non-oscillating state. At this time, the anode current does not flow. Therefore, the secondary type of the leakage type step-up transformer 4 having a large leakage inductance is used. The inverter circuit 2 is used as the anode voltage detecting means 28 of the magnetron 5 for detecting the high voltage side.
For a while from the start of activation to the time when the cathode is sufficiently heated, a larger output is generated than when the magnetron 5 oscillates. Since the inverter circuit 2 is operating even when the magnetron 5 is in the non-oscillating state, the output of the collector voltage detecting means 15 becomes almost the same voltage as in the normal state.
In this period, the output of the anode voltage detecting means 28 is compared with the output of the input current detecting means which becomes almost zero, and the output of the anode voltage detecting means 28 is compared with that of the collector voltage detecting means. Therefore, at the time of startup, when an abnormality such as discharge occurs on the secondary high voltage side of the step-up transformer 4, the secondary high voltage side of the step-up transformer 4 does not reach the oscillation start voltage of the magnetron 5, so the anode voltage detection means. The output of 28 drops and becomes smaller than the output of the collector voltage detecting means 15. Therefore, the abnormality determination means 16 has its output inverted with respect to the normal state, and sends an operation stop signal of the inverter circuit 2 to the output control section 11.

As described above, as the anode voltage detecting means 28 of the magnetron 5, the detecting winding of several turns is provided on the secondary side of the step-up transformer 4, and its output is connected to the input current detecting means 24, both of which are abnormal. By inputting to the judgment means 16 and comparing with the collector voltage detection means 15, it is generated on the secondary high voltage side of the step-up transformer 4 in the non-oscillation state of the magnetron 5 at the time of starting the inverter circuit 2 at the time of microwave heating. A combined heating cooker capable of detecting an abnormality such as discharge and stopping the inverter circuit 2 can be provided.

(Fourth Embodiment) A fourth embodiment of the present invention will be described below with reference to FIG. In Figure 4
The difference from the circuit configuration is that the reference voltage 29
Is provided, and this is compared with the anode voltage detecting means 28 and the input current detecting means 14 and input to the abnormality determining means 16.

The operation of the composite heating cooker configured as described above will be described below. In this embodiment, when the larger output of the anode voltage detecting means 28 and the input current detecting means 14 is smaller than the reference voltage 29, it is determined that the secondary high voltage side of the step-up transformer 4 has caused an abnormality such as discharge. The inverter circuit 2 is stopped.
During microwave heating, the output of the anode voltage detecting means 28 is compared with the reference voltage 29 in the non-oscillating state of the magnetron 5 when the inverter circuit 2 is started, and the input current detecting means 14 of the input current detecting means 14 is compared in the steady oscillation state of the magnetron 5. The output and the reference voltage 29 are compared, and if the reference voltage 29 is higher than the reference voltage 29, this is judged to be abnormal and the inverter circuit 2 is stopped.

As described above, by comparing the reference voltage 29 with the anode voltage detecting means 28 and the input current detecting means 14, changes in the output of the collector voltage detecting means 15 during induction heating and microwave heating are not considered. Since the abnormality determination level can be set by means of the above, it is possible to provide a control device for a composite heating cooker, which widens the degree of freedom in designing the abnormality determination means 16 and its peripheral circuits, and at the same time, design the collector voltage detection means 15 independently. You can

Although the changeover switch 6 has the transfer type contact structure in the first to fourth embodiments, two changeover switches each having a make contact are used to form the inverter circuit 2 according to the required heating method. It goes without saying that the heating coil 3 and the step-up transformer 4 may be connected or separated.

[0031]

As described above, according to the present invention, since the output control unit is configured to stop the inverter circuit according to the comparison output of the input current detection means and the collector voltage detection means, power is supplied to the magnetron. When the secondary high voltage side of the step-up transformer is discharged for some reason during the operation, the outputs of the collector voltage detecting means and the input current detecting means act to stop the operation of the inverter circuit, thereby forming the high voltage circuit. It is possible to greatly improve the safety of the parts and the like that are installed.

Further, by providing the reference voltage to be compared with the anode voltage detecting means and the input current detecting means, it is possible to detect the abnormality without considering the change of the collector voltage during the induction heating and the microwave heating. The degree of freedom in designing the abnormality determination unit and its peripheral circuits can be expanded.

Further, by configuring the output control unit so as to control the conduction time of the switching element according to the output of the input current detection means and the output current detection means, the discharge on the secondary high voltage side of the step-up transformer. Such an abnormality can be detected more accurately.

Further, the step-up transformer having a detection winding as an anode voltage detecting means of the magnetron is provided, and the output control section gives priority to the output of the input current detecting means in the non-oscillating state of the magnetron at the time of starting the inverter. By setting the voltage detection means as the input target of the comparison output, it is possible to accurately detect an abnormality such as discharge on the secondary high voltage side of the step-up transformer when the magnetron is not oscillating when the inverter is started.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a composite heating cooker according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram of each part of the composite heating cooker.

FIG. 3 is a circuit diagram of a composite heating cooker according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a composite heating cooker according to a third embodiment of the present invention.

FIG. 5 is a circuit diagram of a composite heating cooker according to a fourth embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional combined heating cooker.

[Explanation of symbols]

 1 unidirectional power supply 2 inverter circuit 3 heating coil 4 step-up transformer 5 magnetron 6 changeover switch 7 switching element 8 first current transformer 9 first rectifier circuit 10 output current detection means 11 output control unit 12 second current transformer 13 second 2 rectification circuit 14 input current detection means 15 collector voltage detection means 16 abnormality determination means 27 third rectification circuit 28 anode voltage detection means 29 reference voltage

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsunori Tanie 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Jun Iguchi, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. An inverter circuit for converting a commercial power source into high frequency power by using a switching element, a heating coil for inductively heating an object to be heated, a magnetron for generating a microwave, and a booster for generating high voltage power in the magnetron. A transformer, a changeover switch for switching power supply from the inverter circuit between the heating coil and the step-up transformer, input current detection means for detecting an input current from the commercial power source, and an output current of the step-up transformer. Output current detection means, collector voltage detection means for detecting the collector voltage of the switching element, and an output control section for controlling the conduction time of the switching element at least according to the output of the output current detection means, The output control unit outputs a comparison output of the input current detection means and the collector voltage detection means. In response to this, a combined heating cooker in which the inverter circuit is stopped. 2. An inverter circuit for converting commercial power into high frequency power using a switching element, a heating coil for inductively heating an object to be heated, a magnetron for generating microwaves, and a booster for generating high voltage power to the magnetrons. A transformer, a changeover switch for switching power supply from the inverter circuit between the heating coil and the step-up transformer, input current detection means for detecting an input current from the commercial power source, and an output current of the step-up transformer. Output current detection means, and an output control section for controlling the conduction time of the switching element according to at least the output of the output current detection means, the output control section of the input current detection means and a predetermined reference voltage. A composite cooker in which the inverter circuit is stopped according to the comparison output. 3. The combined heating cooker according to claim 1, wherein the output control section controls the conduction time of the switching element according to the output of the input current detection means and the output current detection means. 4. A step-up transformer having a detection winding as an anode voltage detection means of the magnetron, wherein the output control section gives priority to the output of the input current detection means in the non-oscillation state of the magnetron at the time of starting the inverter. The combined heating cooker according to any one of claims 1 to 3, wherein the voltage detection means is an input target of the comparison output.