Heating Regulator

Abstract

To provide a heating cooker in which a fluctuation of a current due to a correction is suppressed.SOLUTION: A heating cooker 100 includes a magnetron 10, a rectifier 12, a step-up transformer 14, a high pressure rectifier 16, a semiconductor element 18, a resistance element 20, and a control part 22. The rectifier 12 rectifies an AC input voltage so as to produce a unidirectional voltage between a first terminal and a second terminal. The step-up transformer 14 has a primary winding one end of which is connected to the first terminal, and a secondary winding connected to the magnetron 10 via the high pressure rectifier 16. The semiconductor element 18 is connected between the other end of the primary winding and the second terminal. The resistance element 20 is connected to the semiconductor element 18 in series. With regard to a current value indicated by current information acquired from the resistance element 20, when a deviation value from an objective indicates a predetermined minimum area, the control part 22 waits until a next cycle of the AC input voltage. As far as the deviation value continuously indicates the minimum area, the control part 22 corrects the length of an on-time of the semiconductor element 18.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cooking device. [Background technology]

[0002] Cooking appliances that use microwave heating are known. The power supply device described in Patent Document 1 uses a semiconductor element to switch a unidirectional voltage obtained by rectifying an AC input voltage, and a step-up transformer generates a high-voltage AC voltage from the current obtained by switching, and then applies a high-voltage DC voltage generated in a high-voltage rectifier to a magnetron. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-281134 Summary of the Invention [Problem to be solved by the invention]

[0004] In the power supply device described in Patent Document 1, in order to keep the microwave output of the magnetron constant, the switching of the semiconductor element is controlled so that the power determined by the unidirectional voltage and the current flowing through the semiconductor element is kept constant. Specifically, a target is set for the current flowing through the semiconductor element, and if the current flowing through the semiconductor element deviates from the target, control is performed to correct it so that it returns to its original state. However, if excessive correction is performed, the current will fluctuate.

[0005] An object of the present invention is to provide a cooking device in which fluctuations in current due to correction are suppressed. [Means for solving the problem]

[0006] The cooking device of the present invention includes a magnetron, a rectifier, a step-up transformer, a high-voltage rectifier, a semiconductor element, a resistive element, and a control unit. The magnetron generates microwaves. The rectifier rectifies an AC input voltage to generate a unidirectional voltage between a first terminal and a second terminal. The step-up transformer has a primary winding having one end connected to the first terminal and a secondary winding connected to the magnetron. The high-voltage rectifier is interposed between the secondary winding and the magnetron. The semiconductor element is connected between the other end of the primary winding and the second terminal. The resistive element is connected in series to the semiconductor element. The control unit controls the switching operation of the semiconductor element based on information on the unidirectional voltage and current information obtained from the resistive element. When the deviation value from the target for the current value indicated by the current information indicates a predetermined minimum region, the control unit waits until the next period of the AC input voltage, and corrects the length of the on-time of the semiconductor element only when the deviation value indicates the minimum region continuously. Effect of the Invention

[0007] According to the present invention, there is provided a cooking device in which fluctuations in current due to correction are suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a circuit diagram of the cooking device according to the embodiment. [Diagram 2] FIG. 4 is a waveform diagram of a current flowing through a semiconductor element. [Diagram 3] 3 is a waveform diagram of an AC input voltage and a current flowing through a semiconductor element. [Figure 4] FIG. 13 is a diagram illustrating an example of a correction table. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and description thereof will not be repeated.

[0010] First, a circuit of a cooking device 100 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit diagram of the cooking device 100. The cooking device 100 is, for example, a microwave oven or an oven range.

[0011] As shown in FIG. 1, the cooking device 100 includes a magnetron 10, a rectifier unit 12, a step-up transformer 14, a high-voltage rectifier unit 16, a semiconductor element 18, a resistive element 20, and a control unit 22.

[0012] The magnetron 10 is a device that generates microwaves, and has an anode, a cathode, and a heater for heating the cathode.

[0013] The rectifier 12 rectifies the AC input voltage Vac to generate a unidirectional voltage V1 between the first terminal D1 and the second terminal D2. The rectifier 12 includes, for example, a full-wave rectifier circuit.

[0014] The step-up transformer 14 has a primary winding W1, a secondary winding W2, and a tertiary winding W3. One end of the primary winding W1 is connected to a first terminal D1. The secondary winding W2 is connected to the anode and cathode of the magnetron 10 via a high-voltage rectifier 16. The tertiary winding W3 is connected to the cathode and heater of the magnetron 10.

[0015] The high voltage rectifier 16 includes, for example, a full-wave voltage doubler rectifier circuit. The high voltage rectifier 16 receives an AC high voltage from the secondary winding W2. The anode of the magnetron 10 is grounded. The high voltage rectifier 16 supplies a DC high voltage (-HV) to the cathode of the magnetron 10.

[0016] The semiconductor element 18 is connected between the other end of the primary winding W1 and the second terminal D2. The semiconductor element 18 is, for example, an IGBT (Insulated Gate Bipolar Transistor). The semiconductor element 18 configured as an N-channel IGBT has a gate, a collector, and an emitter. The collector of the semiconductor element 18 is connected to the other end of the primary winding W1.

[0017] The resistive element 20 is connected in series to the semiconductor element 18. Specifically, the resistive element 20 is connected between the emitter of the semiconductor element 18 and the second terminal D2. The resistive element 20 supplies current information indicating a current I1 flowing through the semiconductor element 18 to the control unit 22 as voltage information.

[0018] The control unit 22 controls the voltage supplied to the gate of the semiconductor element 18 so as to control the switching operation of the semiconductor element 18 based on information about the unidirectional voltage V1 and current information obtained from the resistance element 20.

[0019] 1 and 2, the current I1 flowing through the semiconductor element 18 will be described. FIG 2 is a waveform diagram of the current I1 flowing through the semiconductor element 18.

[0020] 2, control unit 22 controls the voltage supplied to the gate of semiconductor element 18 so that current I1 flows through semiconductor element 18 in a cycle of approximately 20 μs to 50 μs based on information about unidirectional voltage V1. Control unit 22 observes peak values ​​(M1 to M4) of current I1 over, for example, four cycles, and recognizes the average value of the four peak values ​​obtained by the observation as the measurement value of current I1.

[0021] 1 to 3, a description will be given of the waveforms of the AC input voltage Vac and the current I1 flowing through the semiconductor element 18. Fig. 3 is a waveform diagram of the AC input voltage Vac and the current I1.

[0022] As shown in FIG. 3, the AC input voltage Vac exhibits a sinusoidal waveform of a commercial frequency. FIG. 3 further shows eleven arrows, from a first arrow Y1 to an eleventh arrow Y11. Each of the first arrow Y1 to the eleventh arrow Y11 indicates a current measurement timing. At each of these current measurement timings, the control unit 22 obtains a measurement value of the current I1 by the method described in FIG. 2. For example, when the commercial frequency is 60 Hz, the length of a half cycle of the AC input voltage Vac is about 8.3 ms. The time interval between two adjacent arrows is, for example, 0.5 ms.

[0023] In order to keep the microwave output of the magnetron 10 constant, the control unit 22 controls the switching of the semiconductor element 18 so that the power determined by the unidirectional voltage V1 and the current I1 flowing through the semiconductor element 18 remains constant. The waveform of the current I1 is grasped from the measurement results at the current measurement timings indicated by each of the first arrow Y1 to the eleventh arrow Y11.

[0024] Next, with reference to FIGS. 1 to 4, the relationship between the deviation value X from the target of the current I1 flowing through the semiconductor element 18 and the correction value will be described. FIG. 4 is a diagram showing an example of a correction table.

[0025] The control unit 22 corrects according to the correction table shown in FIG. 4 so that the current I1 returns to the original state when it deviates from the target. For example, when the deviation value X from the target of the current I1 is +200 or more, the control unit 22 sets the correction value to "-7" so that the current I1 decreases rapidly. When the deviation value X is between -1 and +1, the control unit 22 sets the correction value to "0" so that the current value of the current I1 is maintained.

[0026] The problem here is the case where the deviation value X indicates the minimum region. When the deviation value X indicates the minimum region on the positive side, "+1 ≦ X < +2", the control unit 22 sets the correction value to "-1". When the deviation value X indicates the minimum region on the negative side, "-2 < X ≦ -1", the control unit 22 sets the correction value to "+1".

[0027] If the control unit 22 immediately corrects the length of the on-time of the semiconductor element 18 when the deviation value X indicates the minimum region on the positive or negative side, the current I1 will fluctuate. Since there is a fluctuation around the target value, in the minimum region, correction may cause the current I1 to fluctuate significantly even when approaching the target value. Therefore, when the deviation value X indicates the minimum region on the positive or negative side, the control unit 22 corrects the length of the on-time of the semiconductor element 18 only when the deviation value X also indicates the minimum region even if the next period of the AC input voltage Vac is waited for. However, when the deviation value X indicates a region other than the minimum region, the control unit 22 determines to correct the length of the on-time of the semiconductor element 18 without waiting until the next period of the AC input voltage Vac. In the regions other than the minimum region, correction without waiting until the next period does not cause a large fluctuation, so the target value can be approached quickly.

[0028] According to the embodiment, a cooking device 100 is provided in which fluctuations in the current I1 due to correction are suppressed.

[0029] The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments, and can be implemented in various aspects without departing from the gist of the present invention. In addition, various inventions can be formed by appropriately combining multiple components disclosed in the above embodiments. For example, some components may be deleted from all components shown in the embodiments. The drawings are mainly shown schematically for ease of understanding, and the number of each component shown may differ from the actual number due to the convenience of drawing. In addition, each component shown in the above embodiments is an example, is not particularly limited, and various modifications are possible within a range that does not substantially deviate from the effects of the present invention. [Industrial Applicability]

[0030] The present invention can be used in the field of cooking appliances. [Explanation of symbols]

[0031] 10. Magnetron 12 Rectifier 14 Step-up transformer 16 High voltage rectifier 18 Semiconductor elements 20 Resistance element 22 Control section 100 Cooker D1 1st terminal D2 2nd terminal W1 Primary winding W2 Secondary winding

Claims

1. A magnetron that generates microwaves; a rectification unit that rectifies an AC input voltage to generate a unidirectional voltage between a first terminal and a second terminal; a step-up transformer having a primary winding connected at one end to the first terminal and a secondary winding connected to the magnetron; a high-voltage rectifier interposed between the secondary winding and the magnetron; a semiconductor element connected between the other end of the primary winding and the second terminal; A resistive element connected in series to the semiconductor element; a control unit that controls a switching operation of the semiconductor element based on information on the unidirectional voltage and current information obtained from the resistance element; Equipped with When the current value indicated by the current information indicates a deviation value from a target value that falls within a predetermined minimum range, the control unit waits until the next period of the AC input voltage, and corrects the length of the on-time of the semiconductor element only when the deviation value continuously indicates the minimum range.

2. The cooking device according to claim 1 , wherein the control unit, when the deviation value indicates a region other than the minimum region, decides to correct the length of the on-time without waiting until a next period of the AC input voltage.

3. The cooking device according to claim 1 or 2, wherein the rectification unit includes a full-wave rectification circuit.

4. The cooking device according to claim 1 , wherein the semiconductor element is an IGBT (Insulated Gate Bipolar Transistor).

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