JPH097761A - Control device for compound cooker - Google Patents

Abstract

PURPOSE: To simplify the constitution by dispensing with a booster transformer secondary side high voltage detecting winding in order to detect an abnormal condition where a magnetron is not oscillated at an inverter starting. CONSTITUTION: A booster transformer 4 furnishes only a winding to drive a magnetron 5 but does not furnish a secondary side high voltage detecting winding. The output of the first transformer 7 to detect the output current of a booster transformer, and the output of the second current transformer 11 to detect the input current of a commercial power source, are compared with a specific third standard voltage given by the third standard voltage generating circuit 20 through a comparing circuit 19. When a magnetron is not oscillated in a high-frequency heating process when an inverter circuit 2 is started, the consumption power is reduced so as to reduce the output of a current transformer, and an abnormal condition can be detected. The second standard voltage given by the second standard voltage generating circuit 14 is reduced, and the control by the output of a collector voltage detecting means 10 is given the priority, so as to control the conducting time of a switching element 9 smaller than a normal operating condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for driving a heating coil and a magnetron with the same inverter circuit, and more particularly to stable control of the magnetron.

[0002]

2. Description of the Related Art In recent years, a composite heating cooker capable of switching between induction heating processing and high-frequency heating processing has been developed, but the problem is to simplify the structure.

A conventional control device for a composite cooker will be described below with reference to the drawings. FIG. 5 is a circuit block diagram showing a configuration of a conventional controller for a composite heating cooker. In the figure, 1 is a unidirectional power supply obtained by rectifying a commercial power supply, 2 is an inverter circuit equipped with a smoothing circuit for preventing switching noise from being superimposed on a power supply line, 3
Is a heating coil for inductively heating an object to be heated, 4 is a step-up transformer, 5 is a magnetron for generating high frequency for high-frequency heating, and 6 is one end of the inverter circuit 2 which is connected to the heating coil 3 or the step-up transformer 4 by switching. Switch of
7 is a first current transformer that detects the output current of the step-up transformer 4, 8 is a secondary high-voltage detection winding of the step-up transformer 4, and 9
Is a switching element, 10 is a collector voltage detecting means for detecting a collector voltage of the switching element 9, 11 is a second current transformer for detecting an input current of a commercial power supply, and 12 is a first first reference voltage for generating a predetermined first reference voltage. Reference voltage generating circuit, 13 is a second switch for switching the level of the first reference voltage, and 14 is a second switch for generating a predetermined second reference voltage.
Reference voltage generating circuit, 15 and 16 are differential amplifiers, 1
7 is an output control circuit for controlling the inverter circuit 2 according to the conduction time of the switching element 9, and 18 is an output control circuit 17
A drive circuit for driving the switching element 9 under the control of 1, a comparator 19 and a third reference voltage generation circuit 20 for generating a predetermined third reference voltage.

The mutual relationship and operation of the above-mentioned components will be described. The low-voltage secondary winding output of the step-up transformer 4 supplies the heater current of the magnetron, and the high-voltage secondary winding output is double-voltage rectified by the capacitor and the diode.
A high voltage of about 4 KV is applied to the magnetron 5 to generate a high frequency. The differential amplifier 15 compares the outputs of the first current transformer 7 and the second current transformer 11 with the first reference voltage, and the differential amplifier 16 compares the output of the collector voltage detecting means 10 with the second reference voltage. The larger one is differentially amplified and input to the output control circuit 17, and the output control circuit 17 controls the conduction time of the switching element 9 via the drive circuit 18 by the input. In order to reliably control the magnetron 5 having a power factor lower than that of the heating coil 3 by the output current of the step-up transformer 4, the second reference voltage level is set to the second switch 13 when operating the magnetron 5. The comparator 19 compares the output of the secondary high-voltage detection winding 8 with the third reference voltage, and the output of the secondary high-voltage detection winding 8 is higher than the third reference voltage. When it is higher, the level of the second reference voltage is lowered.

In a normal state when the heating coil 3 is connected to the inverter circuit 2 by the first switch 6 to inductively heat the object to be heated, the second switch 12 is closed to lower the first reference voltage. The output of the second current transformer 11, which is set and is set to be larger than the output of the collector voltage detection means 10, is compared with the first reference voltage by the first differential amplifier 15 to obtain the first output. The conduction time of the switching element 9 is controlled by being differentially amplified so as to be the same as the reference voltage.

In addition, when the step-up transformer 4 is connected to the inverter circuit 2 by the first switch 6 and the magnetron 5 generates microwaves to heat the object to be heated by microwaves, the second switch 12 is activated. Open to set the first reference voltage high, and the output of the first current transformer 7, which is set higher than the output of the collector voltage detection means 10 and the output of the second current transformer 11, is The differential amplifier 15 of No. 1 compares it with the first reference voltage, and differentially amplifies it to the same as the first reference voltage to control the conduction time of the switching element 9. Further, in the abnormal state where the cathode of the magnetron 5 is not oscillating at low temperature when the inverter circuit 2 is started, the output of the secondary high voltage detection winding 8 is utilized by utilizing the fact that the secondary side output voltage of the step-up transformer 4 rises. Is compared with a third reference voltage by a comparator 19, and if the third reference voltage is exceeded, the output of the comparator 19 lowers the second reference voltage, and the output of the collector voltage detection means 10 and the second reference voltage. The control by the differential amplifier 16 is prioritized over the control by the current transformer and the first differential amplifier 15, and the conduction time of the switching element 9 is controlled to be smaller than that in the steady state. This prevents the occurrence of abnormal oscillation due to insufficient cathode temperature and the breakdown of diodes and capacitors, which are high-voltage components.

[0007]

In such a conventional controller for a composite heating cooker, the step-up transformer 4 has a large leakage inductance in order to cover the low dynamic impedance characteristic of the magnetron 5.
It is composed of a leaky transformer having a constant current source characteristic by increasing the impedance when the primary side is viewed from the secondary side.
Therefore, in order to detect the output proportional to the secondary high voltage, the secondary high voltage detection winding 8 is provided, and the winding is in the vicinity of the secondary high voltage and is insulated by a certain insulation distance or insulator. However, there is a problem that the price is high and there is a limit to miniaturization.

An object of the present invention is to solve the above problems and an object of the present invention is to provide a controller for a composite heating cooker which does not require a secondary high voltage detection winding of a step-up transformer and has a simple structure.

[0009]

According to a first aspect of the present invention, a unidirectional power source obtained by rectifying a commercial power source and an inverter for connecting and disconnecting the unidirectional power source output input through a smoothing circuit with a switching element are provided. A circuit, a heating coil for inductively heating an object to be heated, a magnetron for generating microwaves, a step-up transformer for generating high-voltage power on the secondary side to supply the magnetron, the heating coil and the inverter circuit. A first switch that switches and connects the primary side of the step-up transformer, a first current transformer that detects the secondary side output current of the step-up transformer, and a second current that detects the input current of the commercial power supply. For switching a transformer, a collector voltage detection circuit that detects the collector voltage of the switching element, and a second switch that interlocks with the first switch. A first reference voltage generating circuit for generating a predetermined first reference voltage in two steps, a second reference voltage generating circuit for generating a predetermined second reference voltage, and a predetermined third reference voltage A third reference voltage generating circuit for generating
A first differential amplifier circuit, which receives the output of the first current transformer and the output of the second current transformer, compares the output with the first reference voltage, and differentially amplifies, and the collector voltage detection means. A second differential amplifier circuit for inputting the output of the second reference voltage and performing differential amplification by comparing with the second reference voltage, and outputs of the first current transformer and the second current transformer, A comparator that changes the second reference voltage in comparison with a third reference voltage, an output of the first differential amplifier circuit, and an output of the second differential amplifier circuit are input, and the maximum difference between them is input. An output control circuit for controlling the conduction time of the switching element by a dynamic amplification output, and a drive circuit for driving the switching element by the output of the output control circuit are provided, and the heating coil is driven by the inverter circuit by the first switch. To When the induction heating is continuously performed, the first reference voltage is set high by the second switch, and the output of the collector voltage detecting means is controlled by the differential amplification output of the second current transformer output. When the conduction time of the switching element is controlled prior to the control by the differential amplification output, and when the step-up transformer is connected to the inverter circuit by the first switch to perform high frequency heating, the second switch is used to When the first reference voltage is set low and the output of the first current transformer and the output of the second current transformer are higher than the third reference voltage in the steady operation, the difference between the outputs of the first current transformer is set. The control by the dynamic amplified output is superior to the control by the differential amplified output of the output of the second current transformer and the differential amplified output of the output of the collector voltage detecting means. And by controlling the conduction time of the switching element, the first current transformer output and the second current transformer output the third
At the time of abnormal operation that is less than or equal to the reference voltage of, by lowering the second reference voltage by the comparator,
The control by the differential amplification output of the output of the collector voltage detection means is prioritized over the control by the differential amplification output of the output of the first current transformer and the output of the second current transformer to reduce the conduction time of the switching element. The present invention according to claim 2 is the control device for a composite heating cooker, which is controlled so as to be shorter than during the steady operation. The present invention according to claim 2 further includes a third switch for lowering the third reference voltage and a third reference voltage. When the induction coil is provided in the generating circuit and the third coil lowers the third reference voltage when induction heating is performed by the heating coil, even if the output of the second current transformer is lower than that in the steady operation, The control of the output of the current transformer by the differential amplification output must always control the conduction time of the switching element with priority over the control of the output of the collector voltage detection means by the differential amplification output. According to another aspect of the present invention, there is provided a controller for a composite heating cooker according to the present invention, and the present invention according to the third aspect provides a diode provided in a forward direction from a third reference voltage output to a second switch for heating. When the induction heating is performed by the coil, the second reference voltage and the third reference voltage are set by the second switch.
Even if the output voltage of the second current transformer becomes lower than that during the steady operation, the differential amplification output control of the output of the second current transformer causes the difference in the output of the collector voltage detection means. The control device for a composite heating cooker according to claim 1, wherein the conduction time of the switching element is controlled with priority over the control by the dynamic amplification output, and the invention according to claim 4 is a reference of a comparison circuit. A fourth switch for switching the voltage input is provided, which is connected to the third reference voltage when high frequency heating is performed by the magnetron, and is switched to be connected to the output of the collector voltage detecting means when induction heating is performed by the heating coil. A combined heating cooker according to any one of claims 1 to 3, wherein when the circuit is reversed, it is determined that the heating load is inappropriate. A control device.

[0010]

In the present invention according to claim 1, in the high frequency heat treatment by the magnetron, the comparison circuit compares the outputs of the first current transformer and the second current transformer with the third reference voltage, and then the third reference voltage. When the voltage is equal to or lower than the voltage, the second reference voltage is lowered, and the conduction time of the switching element is controlled to be shorter than that in the steady operation by giving priority to the control by the second differential amplifier. That is, in an abnormal state in which the magnetron is not oscillating when the inverter circuit is started, the power consumption is small, and the outputs of the first current transformer and the second current transformer are small, so that the voltage becomes equal to or lower than the predetermined third reference voltage. By detecting an abnormal state by controlling the conduction time of the switching element shorter than that during steady operation,
The secondary high voltage detection winding in the conventional example is unnecessary.
The other operations are the same as in the conventional example. Also,
In the present invention according to claim 2, in the induction heating process by the heating coil, the third switch lowers the third reference voltage, and even if the output of the second current transformer decreases when the inverter circuit is started, The reference voltage of 3 or less, that is, the comparison circuit does not lower the second reference voltage, so that the control by the output of the second current transformer is ensured. Further, in the present invention according to claim 3, when the diode connecting the third reference voltage output and the second switch lowers the first reference voltage by the second switch in the induction heating process, By lowering the reference voltage of 3 as well, the second reference voltage is prevented from being lowered, and the control by the output of the second current transformer is ensured as in the second aspect. Further, in the present invention according to claim 4, in the induction heating process, the fourth switch applies the output of the collector voltage detecting means as the reference voltage of the comparison circuit, and the comparison circuit reverses when the induction heating load is improper. By doing so, the improper heating load is detected.

[0011]

【Example】

(Embodiment 1) An embodiment of the control device for a composite heating cooker according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of this embodiment. The same components as those of the conventional example shown in FIG. 5 are assigned the same reference numerals and detailed explanations thereof will be omitted. The present embodiment is different from the conventional example in that the step-up transformer 4 does not include the secondary high voltage detection winding, and the magnetron 5 is activated when the inverter circuit 2 is started.
In the abnormal state where is not oscillating, the output of the current transformer is lower than that in the steady operation because the power consumption is small, and the comparator 19 outputs the outputs of the first current transformer 7 and the second current transformer 11. Is compared with a predetermined third reference voltage, the second reference voltage is controlled to be lowered when the voltage is lower than the third reference voltage, and the conduction time of the switching element 9 is narrowed compared to the steady state. There is something I did.

The operation of the above configuration will be described. The operation of the induction heating process by the heating coil 3 is the same as that of the conventional example, and the description thereof is omitted. In a normal state when the microwave is generated by the magnetron 5 to heat the object to be heated by microwaves, the second switch 13 is opened to set the first reference voltage to a high level as in the conventional example, and The output of the first current transformer 7, which is set to be larger than the output of the collector voltage detection means 10 and the output of the second current transformer 11, is compared with the first reference voltage by the first differential amplifier 15. Also, the conduction time of the switching element 9 is controlled by being differentially amplified so as to be the same as the first reference voltage, as in the conventional example.

On the other hand, when the magnetron 5 has a low cathode temperature and is not oscillating when the inverter circuit 2 is started, the heater from the commercial power source consumes only several tens of watts of electric power from the commercial power source. The outputs of the current transformer 7 and the second current transformer 11 are smaller than the third reference voltage, and the output of the comparator 19 lowers the second reference voltage. As a result, the control by the output of the collector voltage detecting means 10 and the second differential amplifier 16 has priority over the control by the current transformer output and the first differential amplifier 15, and the output of the collector voltage detecting means 10 is the second. Is comparatively amplified to be equal to the reference voltage of, and the conduction time of the switching element 9 is narrowed down to be smaller than that in the steady state.
This prevents the occurrence of abnormal oscillation due to insufficient cathode temperature and the destruction of diodes and capacitors, which are high-voltage components.

As described above, according to this embodiment, the step-up transformer 4 is not provided with the secondary high voltage detection winding, and the first current transformer is used in an abnormal state in which the magnetron 5 does not oscillate when the inverter circuit 2 is started. 7 and second current transformer 11
It is said that the abnormal oscillation due to the cathode temperature shortage is caused by narrowing the conduction time of the switching element 9 as compared with the steady state by detecting the decrease of the output of the comparator 19 by the comparator 19 and decreasing the second reference voltage. Moding,
It is possible to prevent damage to the diode and capacitor, which are high-voltage parts, and to realize a compact and low-cost booster transformer.

(Embodiment 2) An embodiment of the control device for a composite heating cooker according to the present invention will be described below with reference to the drawings. FIG. 2 is a circuit diagram showing the configuration of this embodiment. The same components as those in FIG. 1 are assigned the same reference numerals and detailed explanations thereof will be omitted. This embodiment is the first embodiment.
The third difference is that the third reference voltage generating circuit 20 is provided with a third switch 21 and the third reference voltage is switched to a lower value when induction heating is performed by the heating coil 3 than when high frequency heating is performed by a magnetron. I have done so. In the means of the first embodiment, when the outputs of the first and second current transformers are equal to or lower than the third reference voltage, the magnetron is in the non-oscillation abnormal state. Also performs the same operation when the output of the second current transformer is small when the inverter circuit is started. However, in the induction heating, the above operation is not necessary. This embodiment solves that problem by lowering the third reference voltage during the induction heating so that the comparator can reduce the second output even when the output of the current transformer is small at the time of starting the inverter circuit.
The reference voltage of is not changed.

The operation of the above configuration will be described. The heating coil 3 is connected to the inverter circuit 2 by the first switch 6.
When the induction heating is performed by connecting to, the third switch 21 is closed as in the first embodiment, and the third switch 21 in the third reference voltage generation circuit 20 is closed. The level of the reference voltage is changed to a value lower than that in the case of high frequency heating by the magnetron 5. Therefore,
The output of the comparator 19 does not have the operation of changing the second reference voltage in a state where the current does not sufficiently flow when the inverter circuit 2 is started, and the output of the second current transformer 11 and the first differential amplifier 15 The energization time of the switching element 9 is controlled by the control by. The operation when supplying power to the magnetron 5 is the same as that in the first embodiment, and the description thereof is omitted.

As described above, according to the present embodiment, the third switch 21 for changing the third reference voltage is provided so that the third reference voltage is changed to a lower value during induction heating than during high frequency heating. Thus, during high frequency heating, the same effect as in the first embodiment can be obtained, and during induction heating, the operation of changing the second reference voltage is performed even when the output of the second current transformer 11 is small when the inverter circuit 2 is started. Instead, it is possible to reliably control the conduction time of the switching element 9 only by the output of the second current transformer 11 and the first differential amplifier 15.

(Embodiment 3) An embodiment of the present invention according to claim 3 will be described below with reference to the drawings. FIG. 3 is a circuit diagram showing the configuration of this embodiment. The same components as those in FIG. 1 are assigned the same reference numerals and detailed explanations thereof will be omitted. The present embodiment is different from the second embodiment in that a diode 22 is inserted in the forward direction via a resistor between the third reference voltage output and the second switch, and induction heating is performed by the heating coil 3. In addition, when the second reference voltage is lowered by the second switch 13, the third reference voltage is also lowered at the same time, and the third switch in the second embodiment is not necessary. .

The operation of the above configuration will be described. The heating coil 3 is connected to the inverter circuit 2 by the first switch 6.
When the induction heating is performed by connecting to, the second switch 13 is closed to reduce the first reference voltage as in the first embodiment. At this time, the third reference voltage output terminal is changed by the second switch 13. Since it is grounded via the resistor and the diode 22, the third reference voltage also drops. Therefore, similarly to the second embodiment, it is possible to prevent the operation of lowering the second reference voltage by the comparator 19 when the inverter circuit 2 is started during the induction heating. When the second switch 13 is opened during high frequency heating, the first reference voltage and the second reference voltage are separated by the diode 22. The other operations are the same as those in the first and second embodiments, and detailed description thereof will be omitted.

As described above, according to this embodiment, the third reference voltage output is connected to the second switch via the diode and the resistor, and only the closing operation of the second switch 13 is performed during the induction heating. By lowering the first reference voltage and the third reference voltage, the same effect as that of the second embodiment can be obtained with a simple configuration.

(Embodiment 4) An embodiment of the present invention according to claim 4 will be described below with reference to the drawings. FIG. 4 is a circuit diagram showing the configuration of this embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. The present embodiment differs from the first embodiment in that a fourth switch 23 for switching the reference voltage of the comparator 19 between the third reference voltage and the output of the collector voltage detecting means 10 is provided, and when induction heating is performed by the heating coil 3. The reference voltage of the comparator 19 is switched from the third reference voltage to the output of the collector voltage detecting means 10 so as to be connected so that the properness of the heating load at the time of induction heating can be determined.

The operation of the above configuration will be described. When high-frequency heating is performed by the magnetron, the fourth switch 23 applies the third reference voltage as the reference voltage of the comparator 19. The operation at this time is described in the first embodiment.
The detailed description is omitted. On the other hand, when the heating coil 3 is connected to the inverter circuit 2 by the first switch 6 to perform induction heating, the second switch 13 is closed to lower the first reference voltage as in the first embodiment, and The switch 23 applies the output of the collector voltage detecting means 10 as the reference voltage of the comparator 19. At this time, the comparator 19 compares the outputs of the first current transformer 7 and the second current transformer 11 with the output of the collector voltage detecting means 10 to determine whether the heating load is appropriate. For example, when the heating load is an aluminum pan or a small object such as a knife or a fork, the electric power of the inverter circuit 2 is hardly consumed, and the output of the second current transformer 11 is the collector voltage detecting means 1.
The output is smaller than the output of 0, the output of the comparator 19 is inverted, the second reference voltage is lowered, and the conduction time of the switching element 9 is controlled to be smaller than that under normal load. The judgment result of the comparator 19 may be displayed as an abnormal load.

As described above, according to this embodiment, the fourth switch 23 for switching the reference voltage of the comparator 19 between the third reference voltage and the output of the collector voltage detecting means is provided, and when the high frequency heating is performed, the embodiment is used. As in the case of 1, the non-oscillation state is detected by comparing with the third reference voltage, and the output of the collector voltage detecting means 10 is applied during induction heating to determine whether or not the heating load is appropriate. It is possible to realize an efficient control configuration in which the comparator 19 has a plurality of roles.

Although the first switch 6 has a transfer type contact structure in the first to fourth embodiments,
You may make it connect or isolate | separate the inverter circuit 2, the heating coil 3, and the step-up transformer 4 according to a required heating system using two switches provided with the make contact, and the 2nd thru | or 4th. Switches 12, 2
It goes without saying that the switches 1 and 23 may be switches using semiconductor elements such as transistors and ICs.

[0025]

As is apparent from the above description, the control device for a composite heating cooker according to the first aspect of the present invention is inputted via a smoothing circuit and a unidirectional power source obtained by rectifying a commercial power source. An inverter circuit that intermittently switches the unidirectional power output by a switching element, a heating coil that induction-heats an object to be heated, and a magnetron that generates a microwave,
A step-up transformer that generates high-voltage power on the secondary side and supplies it to the magnetron, a first switch that switches and connects the heating coil and the primary side of the step-up transformer to the inverter circuit, and a step-up transformer of the step-up transformer. A first current transformer for detecting a secondary side output current, a second current transformer for detecting an input current of the commercial power source, a collector voltage detection circuit for detecting a collector voltage of the switching element, and the first current transformer. A first reference voltage generation circuit for generating a predetermined first reference voltage in two steps, high and low, by switching a second switch which is interlocked with the switch, and a second reference voltage generation circuit for generating a predetermined second reference voltage. A circuit, a third reference voltage generation circuit for generating a predetermined third reference voltage, and the first
A first differential amplifier circuit for inputting the output of the current transformer and the output of the second current transformer, and performing differential amplification by comparing the output with the first reference voltage; and the output of the collector voltage detecting means. A second differential amplifier circuit that receives and outputs differential amplification by comparing with the second reference voltage, and outputs of the first current transformer and the second current transformer are input, and the third differential amplifier circuit is input. A comparator for changing the second reference voltage in comparison with a reference voltage, an output of the first differential amplifier circuit and an output of the second differential amplifier circuit are input, and a maximum differential amplified output of them is input. An output control circuit for controlling the conduction time of the switching element by means of, and a drive circuit for driving the switching element by the output of the output control circuit, and the heating coil is connected to the inverter circuit by the first switch. hand When conducting heating, the first reference voltage is set high by the second switch, and the differential amplification output of the second current transformer output controls differential amplification of the output of the collector voltage detection means. When the conduction time of the switching element is controlled prior to the control by the output and the step-up transformer is connected to the inverter circuit by the first switch to perform high frequency heating, the second switch is used to perform the first switching. When the reference voltage is set low and the output of the first current transformer and the output of the second current transformer are higher than the third reference voltage in the steady operation, the differential amplification output of the output of the first current transformer. Prior to the control by the differential amplification output of the output of the second current transformer and the differential amplification output of the output of the collector voltage detection means. During abnormal operation in which the output of the first current transformer and the output of the second current transformer are less than or equal to the third reference voltage, the second reference voltage is controlled by the comparator by controlling the conduction time of the switching element. By lowering, the control of the output of the collector voltage detection means by the differential amplification output has priority over the control of the output of the first current transformer and the output of the second current transformer by the switching. By controlling the conduction time of the element to be shorter than that in the steady operation, the step-up transformer 2
With a simple structure that does not require the secondary high-voltage detection winding, it detects abnormal conditions in which the magnetron is not oscillating when the inverter is started, and controls the conduction time of the switching element to be short, making it a moding or high-voltage component. It is possible to prevent destruction of the diode and the capacitor. Also, in the control device for a composite heating cooker according to a second aspect of the present invention, a third switch for lowering the third reference voltage is provided in the third reference voltage generating circuit, and when induction heating is performed by the heating coil, the first switch is used. By lowering the third reference voltage with the switch No. 3, even if the output of the second current transformer is lower than that during steady operation, the control by the differential amplification output of the output of the second current transformer is performed. Since the conduction time of the switching element is controlled by always giving priority to the control of the output of the detection means by the differential amplification output, the same effect as the above can be obtained in the high frequency heat treatment.
In the induction heating process, without shortening the conduction time of the switching element even when the inverter circuit is started,
It is possible to perform reliable control by the output of the current transformer. Also, in the control device for a composite heating cooker according to the third aspect of the present invention, a diode is inserted in the forward direction from the third reference voltage output to the second switch, and when induction heating is performed by the heating coil, the second Switch reduces both the first reference voltage and the third reference voltage, and even if the output of the second current transformer becomes lower than that during steady operation, the differential amplification output of the output of the second current transformer The control by means of controlling the conduction time of the switching element is always prioritized over the control by means of the differential amplification output of the output of the collector voltage detecting means, thereby providing a simpler configuration without providing an extra switch. It is possible to obtain the same effect as that of the present invention according to item 2. Further, the control device for a composite heating cooker according to a fourth aspect of the present invention includes a fourth switch for switching the reference voltage input of the comparison circuit, which is connected to the third reference voltage when high frequency heating is performed by the magnetron, and the heating coil is connected. 5. When the induction heating is performed by the above, the output of the collector voltage detecting means is switched to be connected, and when the comparison circuit is inverted during the induction heating, it is determined that the heating load is improper. In addition to the effect of the present invention relating to No. 3, it is possible to detect the appropriateness of the heating load in the induction heating process using the same current transformer.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a configuration of a second embodiment of the control device for the composite heating cooker according to the present invention.

FIG. 3 is a circuit diagram showing a configuration of a third embodiment of the control device for the composite heating cooker according to the present invention.

FIG. 4 is a circuit diagram showing a configuration of a fourth embodiment of the control apparatus for the composite heating cooker according to the present invention.

FIG. 5 is a circuit diagram showing a configuration of a conventional controller for a composite heating cooker.

[Explanation of symbols]

 1 unidirectional power supply 2 inverter circuit 3 heating coil 4 step-up transformer 5 magnetron 6 first switch 7 first current transformer 8 secondary high voltage detection winding 9 switching element 10 collector voltage detection means 11 second current transformer 12 second 1 reference voltage generation circuit 13 2nd switch 14 2nd reference voltage generation circuit 15 1st differential amplifier (1st differential amplification circuit) 16 2nd differential amplifier (2nd differential amplification circuit) ) 17 output control circuit 18 drive circuit 19 comparator (comparison circuit) 20 third reference voltage generation circuit 21 third switch 22 diode 23 fourth switch

 ─────────────────────────────────────────────────── ─── 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. A unidirectional power source obtained by rectifying a commercial power source, an inverter circuit for connecting and disconnecting the unidirectional power source output input through a smoothing circuit by a switching element, and a heating coil for induction heating a material to be heated. A magnetron for generating microwaves, a step-up transformer for generating high-voltage power on the secondary side and supplying the magnetron to the magnetron, and a switching coil for connecting the heating coil and the primary side of the step-up transformer to the inverter circuit. 1 switch, and a first current transformer for detecting the secondary side output current of the step-up transformer,
A second current transformer that detects an input current of the commercial power supply, a collector voltage detection circuit that detects a collector voltage of the switching element, and a predetermined first switch by switching a second switch that interlocks with the first switch. A first reference voltage generating circuit for generating the reference voltage of 2 in high and low stages, a second reference voltage generating circuit for generating a predetermined second reference voltage, and a third reference voltage generating circuit for generating a predetermined third reference voltage. A reference voltage generating circuit, and a first differential amplifier circuit for inputting the output of the first current transformer and the output of the second current transformer and performing differential amplification by comparing with the first reference voltage. And a second differential amplifier circuit for inputting the output of the collector voltage detection means and performing differential amplification by comparing the output with the second reference voltage, the first current transformer and the second current transformer. Output and input, the third A comparator for changing the second reference voltage in comparison with a reference voltage, an output of the first differential amplifier circuit and an output of the second differential amplifier circuit are input, and a maximum differential amplified output of them is input. An output control circuit for controlling the conduction time of the switching element by means of, and a drive circuit for driving the switching element by the output of the output control circuit, and the heating coil is connected to the inverter circuit by the first switch. When induction heating is performed by the second switch, the first reference voltage is set to a high value by the second switch, and the differential amplification output of the second current transformer output controls differential output of the collector voltage detection means. The conduction time of the switching element is controlled prior to the control by the amplified output, and the step-up transformer is connected to the inverter by the first switch. When high frequency heating is connected to the road, the first by the second switch 1
Of the first current transformer and the output of the second current transformer are higher than the third reference voltage, the differential amplification of the output of the first current transformer is performed. The output control controls the conduction time of the switching element in preference to the differential amplification output of the output of the second current transformer and the differential amplification output of the output of the collector voltage detecting means, and controls the conduction time of the switching element. During an abnormal operation in which the output of the current transformer and the output of the second current transformer are equal to or lower than the third reference voltage, the comparator reduces the second reference voltage to reduce the output of the collector voltage detecting means. The control by the differential amplification output has priority over the control by the differential amplification output of the output of the first current transformer and the output of the second current transformer. Composite heating cooker controller the conduction time of the switching element so as to control shorter than during the steady operation. 2. A third switch for lowering the third reference voltage is provided in the third reference voltage generating circuit, and when induction heating is performed by a heating coil, the third switch is used
Even if the output of the second current transformer is lower than that during the steady operation by lowering the reference voltage of, the control by the differential amplification output of the output of the second current transformer is controlled by the difference of the output of the collector voltage detecting means. The control device for the combined heating cooker according to claim 1, wherein the conduction time of the switching element is always controlled with priority over the control by the dynamic amplification output. 3. A diode is inserted in the forward direction from the third reference voltage output to the second switch, and when induction heating is performed by the heating coil, the first reference voltage and the third reference voltage are applied by the second switch. Even if the output voltage of the second current transformer is lower than that during the steady operation, the control by the differential amplification output of the output of the second current transformer is the differential amplification of the output of the collector voltage detection means. The control device for the combined heating cooker according to claim 1, wherein the conduction time of the switching element is always controlled with priority over the control by the output. 4. A fourth switch for switching the reference voltage input of the comparison circuit is provided, which is connected to the third reference voltage when high frequency heating is performed by the magnetron, and is connected to the output of the collector voltage detection means when induction heating is performed by the heating coil. 4. The control device for a combined heating cooker according to claim 1, wherein the heating load is determined to be inappropriate when the comparison circuit is inverted during induction heating.