JP2001023770A - Heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily exercise control of input current in a heating cooker that uses a heater. SOLUTION: A DC power supply circuit 3 is connected to an AC power supply 1 and a heater 10 and an IGBT(insulated gate bipolar transistor) 11 are connected in series with the DC power supply circuit 3. A current transformer 21 which detects input currents is provided on the power line of the AC power supply 1 and a voltage detecting circuit 22 for detecting the voltage of the AC power supply 1 is provided on the output side of the DC power supply circuit 3. A control circuit 20 detects input power from a voltage value detected by the voltage detecting circuit 22 and a current value detected by the current transformer 21, and controls the IGBT 11 so that the detected current is less than an upper limit value, and controls the IGBT 11 so that the detected power is equal to or close to predetermined power when the detected current is in the range less than the upper limit value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooking device provided with a heater.

[0002]

Conventionally, for example, in a cooking device provided with a heater for an oven, for example,
In this configuration, a heater and switch means are connected in series to an AC power supply. In this case, since the heating power of the heater is smaller than that of the gas range, the heater capacity is set in advance to a capacity at which a current close to the maximum allowable current flows. However, when the power supply voltage of the AC power supply fluctuates, the input current exceeds the maximum allowable current, and the power supply breaker at home may be cut off.

As a countermeasure, an input current is detected, and when the input current exceeds a predetermined value, the amount of current supplied to the heater is reduced. In this case, a triac is connected in series to the heater, and the conduction angle of the triac is adjusted to perform phase control. However, this phase control has a problem that a zero-cross detection circuit is required, and the firing angle control is also troublesome.

[0004] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heating cooker that can easily perform input current control in a heater using a heater.

[0005]

According to a first aspect of the present invention, there is provided a DC power supply circuit connected to an AC power supply, a heater and a semiconductor switching element connected in series to the DC power supply circuit,
Input current detecting means for detecting an input current from the AC power supply, and input control means for controlling the switching element such that a detected current value of the input current detecting means is less than a set upper limit value. Is done.

In this configuration, the DC power is supplied to the heater, and the heater is turned off by the semiconductor switching element when the heater is turned off. Therefore, a transistor can be used as the semiconductor switching element. Then, the on / off control of the switching element is performed, for example, in a short cycle so that the input current becomes less than the upper limit value. Therefore, even if the power supply voltage of the AC power supply fluctuates, it is possible to prevent the input current from becoming excessive and prevent the power supply breaker from being cut off, and furthermore, the conventional zero-cross detection circuit is unnecessary and troublesome. No need for arc angle control,
The circuit configuration and the switching control are simplified, and the input current control is simplified as a whole.

According to a second aspect of the present invention, in the first aspect of the present invention, there is provided a power supply voltage detecting means for detecting a voltage of the AC power supply, and the input control means is provided with a voltage detected by the power supply voltage detecting means and an input current detecting means. And the input power is detected from the detected current value, and the semiconductor switching element is controlled so that the detected current is less than the upper limit value. A feature is that the semiconductor switching element is controlled so as to approach power.

[0008] Under a constant load condition, the input current changes as the power supply voltage of the AC power supply fluctuates. Also, the higher the amount of heat by the heater is, the better for cooking,
That is, the input power should be closer to the rated power of the cooking device. However, if the upper limit of the input current is set to, for example, the specified current value of the power breaker, the input power exceeds the rated power of the cooking device when the power supply voltage increases. If the upper limit value of the input current is set lower in consideration of this, when the power supply voltage becomes lower, the calorie of the heater decreases.

However, in the invention of claim 2,
Since the input current, that is, the detected current is controlled so as to be less than the upper limit value, it is possible to prevent the input current from becoming excessively large, and furthermore, to make the detected power equal to or smaller than the predetermined power in a range below the upper limit value. , The amount of heat generated by the heater can be increased as much as possible, which is advantageous for heating cooking.

According to a third aspect of the present invention, in the first aspect of the present invention, the DC power supply circuit is provided with a resonance circuit and a high frequency switching element, and an inverter circuit for driving the microwave generator is connected. Having. According to the third aspect of the invention, in addition to the heating and cooking by the heater, the heating and cooking by the microwave generator can be performed. In this case, since the same DC power supply circuit as the heater is used as the power supply for the inverter circuit including the resonance circuit for driving the microwave generator and the high-frequency switching element, the configuration can be simplified.

A fourth aspect of the present invention is characterized in that, in the third aspect, a switching means for selectively switching between a case where the output of the DC power supply circuit is applied to the heater and a case where the output is applied to the inverter circuit is provided. In the invention of claim 4, since the heating cooking using the heater and the heating cooking using the microwave generator are selectively executed, that is, the heating cooking is not performed simultaneously, the input current has an upper limit value. There is no such thing.

According to a fifth aspect of the present invention, a DC power supply circuit connected to an AC power supply, a heater connected to the DC power supply circuit, a resonance circuit and a high-frequency switching element connected to the DC power supply circuit are provided. An inverter circuit for driving the wave generator, a switching unit that selectively switches between a case where the heater and the high-frequency switching element are connected, and a case where the resonance circuit and the high-frequency switching element are connected, Input current detection means for detecting an input current from the AC power supply, and input control means for controlling the high-frequency switching element so that a detection current value of the input current detection means is less than a set upper limit value. Be composed.

According to the fifth aspect of the present invention, even if the power supply voltage of the AC power supply fluctuates, it is possible to prevent the input current from becoming excessively large, and furthermore, the conventional zero-cross detection circuit is unnecessary and the ignition angle is cumbersome. No control is required, and the circuit configuration and the switching control are simplified, and the input current control is simplified as a whole. Further, since the heating and cooking using the heater and the heating and cooking using the microwave generator are selectively executed, the input current does not exceed the upper limit value. In addition, the high-frequency switching element of the inverter circuit can be used for switching the heater, which also simplifies the circuit configuration.

The invention of claim 6 is characterized in that, in the invention of claim 3 or 5, a noise filter is connected between the AC power supply and the DC power supply circuit. When driving a microwave generator with an inverter circuit,
Noise may be generated by the switching of the high-frequency switching element, and the noise may enter the other electric devices from the AC power supply. According to the sixth aspect of the present invention, since the noise filter is connected between the AC power supply and the DC power supply circuit, the noise generated in the inverter circuit can be prevented from being output to other electric devices. In addition, noise may be generated when the heater is turned off by the semiconductor switching element or the high-frequency switching element. In this case as well, the noise filter can prevent noise leakage.

According to a seventh aspect of the present invention, in the fourth or fifth aspect, the switching means switches at a relatively high speed so that the heating operation by the heater is continuous and the heating operation by the microwave generator is continuous. It is characterized by being adapted to be operated. According to the present invention, the heating action by the heater and the heating action by the microwave generator can be simultaneously obtained while preventing the input current from becoming excessive.

An eighth aspect of the present invention is characterized in that, in the third or fifth aspect, the input current is controlled to be less than the upper limit value when the heater is energized and when the microwave generator is energized. According to the present invention, it is possible to prevent the input current from becoming excessively large both when the heater is energized and when the microwave generator is energized.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. First, an electrical configuration will be described with reference to FIG. A DC power supply circuit 3 is connected to the AC power supply 1 via a noise filter 2. The noise filter 2 includes two capacitors 4 and 5 and a common mode choke coil 6 connected as shown in FIG. The DC power supply circuit 3 includes a full-wave rectifier circuit 7 and a choke coil 8. A capacitor 9 is connected to output terminals 3a and 3b of the DC power supply circuit 3. Further, in parallel with the capacitor 9, a resistor 10 for an oven and an IG as a semiconductor switching element are connected.
A series circuit including the BT11 is connected. In addition,
FIG. 2 shows an AC voltage waveform and an output voltage waveform of the full-wave rectifier circuit 7.

Further, the output terminals 3a, 3a of the DC power supply circuit 3
The resonance circuit 12 and the IGBT 13 which is a high-frequency switching element are connected in series between b. The resonance circuit 12 includes a primary coil 14a of a high-frequency transformer 14 and a resonance capacitor 15 connected as shown in the figure.
A freewheel diode 16 is connected to the IGBT 13 in anti-parallel. In the resonance circuit 12 and the IGBT 13, an inverter circuit 17 is configured by a freewheel diode 16. The high-frequency transformer 14
The magnetron 19 as a microwave generator is connected to the secondary coil 14b via a rectifier circuit 18.
The inverter circuit 17 generates a high-frequency current in the primary coil 14a of the high-frequency transformer 14 by turning on and off the IGBT 13 at an appropriate on-off timing, and thereby the magnetron 19 on the side of the secondary coil 14b.
Is driven to generate microwaves.

The IGBTs 11 and 13 are driven by a control circuit 20. This control circuit 20
Is configured to include a microcomputer, and a drive circuit including a photocoupler is provided at an output stage for the IGBTs 11 and 13.

A current transformer 21 serving as input current detecting means is provided on an AC power supply line between one power supply terminal of the AC power supply 1 and one input terminal of the full-wave rectification source circuit 7. The detected current value is supplied to the control circuit 20. Further, the voltage detection circuit 22 serving as power supply voltage detection means detects the voltage of the AC power supply 1 by detecting the output voltage of the DC power supply circuit,
The detected voltage value is input to the control circuit 20. The control circuit 20 receives a switch signal from a switch input circuit 23 having various switches. Among these various switches, a switch that specifies cooking using a heater, a switch that specifies cooking using a magnetron, a switch that specifies cooking using both, a start switch,
It includes a time setting switch and the like.

The control circuit 20 functions as input control means. Hereinafter, control of the heater 10 by the control circuit 20 will be described with reference to the flowchart of FIG. The rated power of the cooking device of this embodiment is, for example, 1.5 kW, and the upper limit current value is 15 A. The flowchart of FIG. 4 is started when a switch for designating cooking using a heater is operated, a time setting switch is operated, and a start switch is operated. First, in step S1, the IGBT 11 is PWM-controlled with an initial duty ratio as shown in FIG. 3, for example, so that the heater current is controlled to be the minimum input current. In this case, the IGBT 11
The input current increases as the on-duty ratio (t / T) increases.

In the next step S2, the current value detected by the current transformer 21 is read, and in the next step S3, it is determined whether or not this detected current value is less than an upper limit value (for example, 15 A which is the same as the rated current value). Is determined, and if less, the process proceeds to step S4. In step S4, the detected voltage value by the voltage detection circuit 22 is read, and the input power is calculated from the detected current value. And step S
5, the input power is set to a predetermined power (for example, rated power 1..
5 kW). If the input power is equal to the predetermined power, the process returns to step S2 without changing the on-duty ratio.
The on-duty ratio of the IGBT 11 is increased by a predetermined amount (an amount by which the power is increased by 10%). ) Make it smaller.

As described above, in this embodiment, the detected current value is controlled so as to be less than the upper limit value of 15 A, and the detected power becomes 1.5 kW which is the predetermined power in a range less than the upper limit value. Or to approach the predetermined power. For example, if the power supply voltage of the AC power supply is 100 V, the input current becomes approximately 15V.
At A, the input power is controlled to be approximately 1.5 kW.

When the power supply voltage of the AC power supply is 110 V, which is the maximum voltage in the expected voltage fluctuation range, if the above-mentioned control input current is 15 A, the input power becomes 1.65 kW. However, in this embodiment, the input power is 1.
Since the IGBT 11 is controlled to be less than 5 kW,
The input current will be suppressed to approximately 13.6A.

Further, when the power supply voltage of the AC power supply is 90 V which is the minimum voltage in the expected voltage fluctuation range, if an attempt is made to obtain 1.5 kW as input power, the input current at that time becomes approximately 16 kW. However, in this embodiment, since the input current is controlled to be less than 15 A, the input power is 1.35 kW.

As can be understood from the above, since the input current is controlled to be less than the upper limit value, it is possible to prevent the input current from becoming excessively large and to prevent the power supply breaker from being cut off. In addition, since the detected power is controlled so as to be equal to or close to the predetermined power in a range less than the upper limit, the amount of heat generated by the heater can be increased as much as possible, which is advantageous for heating cooking.

Further, according to the present embodiment, since the DC power supply circuit 3 is connected to the inverter circuit 17 for driving the magnetron 19 with the resonance circuit 12 and the IGBT 13 as a high-frequency switching element, the heating by the heater 10 is performed. In addition to cooking, heating cooking by the magnetron 19 can be performed. In this case, since the same DC power supply circuit 3 as the heater 10 is used as the power supply of the inverter circuit 17 for driving the magnetron 19, the configuration can be simplified.

Furthermore, according to the present embodiment, since the noise filter 2 is connected between the AC power supply 1 and the DC power supply circuit 3, the following effects can be obtained. That is, when the magnetron 19 is driven by the inverter circuit 17, noise is generated due to the switching of the IGBT 13, and there is a possibility that the noise may enter the AC power supply 1 to another electric device. However, according to this embodiment, the inverter circuit 1
The noise generated in step 7 can be prevented from being output to the other electric devices. In addition, noise may be generated even when the heater 10 is turned off by the IGBT 11. In this case, the noise filter 2 can also prevent noise leakage.

In the above embodiment, the input current value is changed within the range below the upper limit value in consideration of the input voltage. However, the input current value is controlled so as to be uniquely maintained at the upper limit value. Even so, the intended purpose can be achieved.
In this case, when the power supply voltage of the AC power supply is 110 V which is the maximum voltage in the predicted voltage fluctuation range, 13.6 A is set as the upper limit of the current so as not to exceed a predetermined power, for example, 1.5 kW. Is preferred.

Next, FIG. 5 shows a second embodiment of the present invention. In the second embodiment, the case where the output of the DC power supply circuit 3 is applied to the heater 10 and the case where the output of the DC power supply circuit 3 is applied to the inverter circuit 17 are described. This is characterized in that a changeover switch 31 which is a changeover means for selectively changing over is provided. That is, the movable contact 31c of the changeover switch 31 is connected to the other output terminal 3b of the DC power supply circuit 3, one fixed contact 31a is connected to the emitter of the IGBT 11, and the other fixed contact 31b is connected to the emitter of the IGBT 13. ing. The changeover switch 31 is controlled by the control circuit 20.
The contact (ca) and the contact (c-b) are selectively closed. In the second embodiment, the heating cooking using the heater 10 and the magnetron 19
To execute the cooking and cooking using
Since they are not executed at the same time, the input current does not exceed the upper limit.

In the second embodiment, the changeover switch 31 is set at a relatively high speed (for example, the contact point (ca)) so that the heating operation by the heater 10 is continuous and the heating operation by the magnetron 19 is continuous. The switching operation may be performed at a contact (c-b) for 2 seconds after the closing for 2 seconds. Then, the input current control described above may be performed in the closed state (contact of the heater 10) for 2 seconds between the contacts (ca). In this case, the contact (c-
b) Closed state for 2 seconds between (magnetron 19 can be energized)
However, the input current control described above may be performed.
This prevents the input current from becoming excessively large, and prevents the heating operation of the heater 10 and the magnetron 19.
And the heating effect by the heating can be obtained at the same time.

FIG. 6 shows a third embodiment of the present invention. This embodiment differs from the first embodiment in the following points. That is, when the heater 10 is connected to the IGBT 13 which is a high-frequency switching element,
There is provided a changeover switch 32 for switching between connection between the IGBT 13 and the IGBT 13. That is, the movable contact 32c of the changeover switch 32 is connected to the collector of the IGBT 13, one fixed contact 32a is connected to the heater 10,
The other fixed contact 32b is connected to the resonance circuit 12. The changeover switch 32 is selectively closed by the control circuit 20 between the contacts (ca) and between the contacts (c-b).

In the third embodiment, the heater 10
And the cooking using the magnetron 19 are executed alternatively, and the input current does not exceed the upper limit. In addition, the IGBT 13 which is a high-frequency switching element of the inverter circuit 17 can be used for switching of the heater 10, which also simplifies the circuit configuration.

[0034]

As apparent from the above description, the present invention has the following effects. According to the first aspect of the present invention, it is possible to prevent the input current from becoming excessively large, to prevent the power breaker from being cut off, and to simplify the circuit configuration and the power cutoff control. In general, input current control can be simplified. According to the invention of claim 2, since the input current is controlled to be less than the upper limit value, it is possible to prevent the input current from becoming excessively large,
In addition, since the detected power is controlled so as to be equal to or close to the predetermined power in a range less than the upper limit, the amount of heat generated by the heater can be increased as much as possible.
This is advantageous for heating cooking.

According to the third aspect of the invention, in addition to the heating and cooking by the heater, the heating and cooking by the microwave generator can be performed, and the resonance circuit and the high frequency switching element for driving the microwave generator are provided. As the power supply for the inverter circuit, the same DC power supply circuit as the heater can be used, and the configuration can be simplified. According to the invention of claim 4, since the heating cooking using the heater and the heating cooking using the microwave generator are selectively executed, that is, the heating cooking is not performed simultaneously, the input current is reduced. It does not exceed the upper limit.

According to the fifth aspect of the present invention, the high-frequency switching element of the inverter circuit is used to selectively perform the heating cooking using the heater and the heating cooking using the microwave generator. In addition to the switching of the device, it can also be used for switching the heater, which also simplifies the circuit configuration. According to the invention of claim 6, since the noise filter is connected between the AC power supply and the DC power supply circuit, leakage of noise generated in the inverter circuit can be eliminated, and noise leakage can be prevented even when the heater is switched. it can. According to the invention of claim 7,
The heating action by the heater and the heating action by the microwave generator can be simultaneously obtained while preventing the input current from becoming excessive.

According to the eighth aspect of the invention, it is possible to prevent the input current from becoming excessively large both when the heater is energized and when the microwave generator is energized.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a waveform diagram of a voltage of an AC power supply and an output voltage of a DC power supply circuit.

FIG. 3 is a diagram showing an on / off state during switching of the IGBT;

FIG. 4 is a flowchart of control contents.

FIG. 5 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;

FIG. 6 is a view corresponding to FIG. 1, showing a third embodiment of the present invention.

[Explanation of symbols]

1 is an AC power supply, 2 is a noise filter, 3 is a DC power supply circuit, 10 is a heater, 11 is an IGBT (semiconductor switching element), 12 is a resonance circuit, 13 is an IGBT (switching element), 14 is a high-frequency transformer, and 17 is an inverter. Circuit, 19 is a magnetron (microwave generator), 2
0 denotes a control circuit (input control means), 21 denotes a current transformer (input current detection means), 22 denotes a voltage detection circuit (power supply voltage detection means), and 31 and 32 denote changeover switches (switching means).

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K086 AA05 BA02 BA08 BB01 DA12 DA13 DB03 DB11 DB16 EA08 3L086 AA02 CC21 DA01 3L087 AA01 AB03 BC19 CA01 CA02 CA03 CA11 DA30

Claims (8)

[Claims] A DC power supply circuit connected to an AC power supply; a heater and a semiconductor switching element connected in series to the DC power supply circuit; input current detection means for detecting an input current from the AC power supply; A heating cooker comprising: input control means for controlling the switching element so that the current value detected by the current detection means is less than a set upper limit value. 2. A power supply voltage detecting means for detecting a voltage of an AC power supply, wherein the input control means detects an input power from a voltage value detected by the power supply voltage detecting means and a current value detected by the input current detecting means. A configuration in which the semiconductor switching element is controlled so that the detected current is less than the upper limit value, and the semiconductor switching element is controlled such that the detected power becomes a predetermined power or approaches the predetermined power in a range less than the upper limit value. The cooking device according to claim 1, wherein: 3. The heating cooker according to claim 1, wherein the DC power supply circuit is connected to an inverter circuit for driving the microwave generator, which is provided with a resonance circuit and a high-frequency switching element. 4. The cooking device according to claim 3, further comprising switching means for selectively switching between the case where the output of the DC power supply circuit is supplied to the heater and the case where the output of the DC power supply circuit is supplied to the inverter circuit. 5. A microwave generator, comprising: a DC power supply circuit connected to an AC power supply; a heater connected to the DC power supply circuit; and a resonance circuit and a high frequency switching element connected to the DC power supply circuit. An inverter circuit for connecting the heater and the high-frequency switching element; a switching unit for selectively switching between a case where the resonance circuit and the high-frequency switching element are connected; and A heating cooker comprising: input current detecting means for detecting an input current; and input control means for controlling the high-frequency switching element such that a detected current value of the input current detecting means is less than a set upper limit. 6. A noise filter is connected between the AC power supply and the DC power supply circuit.
Or the heating cooker according to 5. 7. The switching means is adapted to perform a switching operation at a relatively high speed so that the heating action by the heater is continuous and the heating action by the microwave generator is continuous. Item 6. A heating cooker according to item 4 or 5. 8. The heating cooker according to claim 3, wherein the input current is controlled to be less than the upper limit value when the heater is energized and when the microwave generator is energized.