JP2023109036A - heating cooker - Google Patents

Abstract

To provide a heating cooker in which an inrush current flowing into a semiconductor element 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. The control part 22 controls a switching operation of the semiconductor element 18 according to a transition period modulation table different from a stable period modulation table so that an inrush current flowing into the semiconductor element 18 within a predetermined time from a start-up of the magnetron 10 is suppressed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heat cooker.

A heating cooker that employs a microwave heating method is known. The power supply device described in Patent Document 1 switches a unidirectional voltage obtained by rectifying an AC input voltage with a semiconductor element, obtains an AC high voltage with a step-up transformer from the current obtained by the switching, and then converts the high voltage. A DC high voltage generated by the rectifier is applied to the magnetron.

JP-A-11-281134

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 constant. . However, there is no means for suppressing the rush current flowing through the semiconductor element when the magnetron starts up.

An object of the present invention is to provide a heating cooker in which rush current flowing through a semiconductor element is suppressed.

A heating cooker of the present invention includes a magnetron, a rectifying section, a step-up transformer, a high voltage rectifying section, a semiconductor element, a resistance element, and a control section. The magnetron generates microwaves. The rectifier unit 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 one end of which is 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 with the semiconductor element. The control section controls the switching operation of the semiconductor element based on the information on the unidirectional voltage and the current information obtained from the resistance element. The control unit controls a transition period modulation table different from a stable period modulation table used during steady-state operation of the magnetron so that an inrush current flowing through the semiconductor element is suppressed within a predetermined time after the rise of the magnetron. to control the switching operation according to.

ADVANTAGE OF THE INVENTION According to this invention, the heating cooker by which the inrush current which flows into a semiconductor element is suppressed is provided.

1 is a circuit diagram of a heating cooker according to an embodiment; FIG. FIG. 2 is a waveform diagram of current flowing through a semiconductor element; FIG. 4 is a waveform diagram of an AC input voltage and a current flowing through a semiconductor element;

An embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

First, referring to FIG. 1, the circuit of the heating cooker 100 according to the embodiment will be described. FIG. 1 is a circuit diagram of the heating cooker 100. As shown in FIG. Heat cooker 100 is, for example, a microwave oven or an oven range.

As shown in FIG. 1, the heating cooker 100 includes a magnetron 10, a rectifying section 12, a step-up transformer 14, a high voltage rectifying section 16, a semiconductor element 18, a resistance element 20, and a control section 22. .

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

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. Rectifying section 12 includes, for example, a full-wave rectifying circuit.

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 the first terminal D1. The secondary winding W2 is connected to the anode and cathode of the magnetron 10 via the high voltage rectifier 16. As shown in FIG. A tertiary winding W3 is connected to the cathode of the magnetron 10 and the heater.

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

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

A resistive element 20 is connected in series with 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 resistance element 20 supplies current information indicating the current I1 flowing through the semiconductor element 18 to the control section 22 as voltage information.

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 the information on the unidirectional voltage V1 and the current information obtained from the resistance element 20 .

Next, the current I1 flowing through the semiconductor element 18 will be described with reference to FIGS. 1 and 2. FIG. FIG. 2 is a waveform diagram of the current I1 flowing through the semiconductor element 18. As shown in FIG.

As shown in FIG. 2, the control unit 22 controls the voltage supplied to the gate of the semiconductor element 18 so that the current I1 flows through the semiconductor element 18 at a period of about 20 μs to 50 μs based on the information on the unidirectional voltage V1. . The control unit 22, for example, observes the peak values (M1 to M4) of the current I1 over four cycles, and recognizes the average value of the four peak values obtained by observation as the measured value of the current I1.

Next, the waveforms of the AC input voltage Vac and the current I1 flowing through the semiconductor element 18 will be described with reference to FIGS. 1 to 3. FIG. FIG. 3 is a waveform diagram of AC input voltage Vac and current I1.

As shown in FIG. 3, the AC input voltage Vac exhibits a sinusoidal waveform of commercial frequency. For example, when the commercial frequency is 60 Hz, the length of the half cycle of the AC input voltage Vac is approximately 8.3 ms. The waveform of the current I1 can be grasped from the measurement result of the current I1 every moment by the method explained in FIG. In order to keep the microwave output of the magnetron 10 constant, the control unit 22 controls the switching operation 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 is constant. .

A half-cycle period indicating a positive voltage in one cycle of the AC input voltage Vac is, for example, a first period T1, a second period T2, a third period T3, a fourth period T4, and a fifth period T5. classified into

During the first period T1, the control section 22 supplies a control pulse having a constant pulse width to the gate of the semiconductor element 18 . That is, the first period T1 is the first waiting period.

In the second period T2, in order to prevent the current I1 from becoming too large, the control section 22 sequentially supplies control pulses to the gate of the semiconductor element 18 so that the ON time of the semiconductor element 18 gradually shortens. That is, the ON time of the control pulse is modulated during the second period T2.

In the third period T3, the control section 22 supplies a control pulse having a constant pulse width to the gate of the semiconductor element 18. FIG. That is, the third period T3 is the second waiting period.

In the fourth period T4, in order to prevent the current I1 from becoming too small, the control section 22 sequentially supplies control pulses to the gate of the semiconductor element 18 so that the ON time of the semiconductor element 18 gradually increases. That is, the ON time of the control pulse is modulated during the fourth period T4.

In the fifth period T5, the control section 22 supplies a control pulse having a constant pulse width to the gate of the semiconductor element 18. FIG. That is, the fifth period T5 is the third waiting period.

A half-cycle period indicating a negative voltage in one cycle of the AC input voltage Vac is also divided into five periods, and similar control is performed.

Next, the transient modulation table will be explained.

In the second period T2, the control unit 22 repeats the step number N of reducing the ON time of the control pulse by the pulse step S every time the fixed time Ts elapses. In the fourth period T4, the control unit 22 repeats the step number N of increasing the ON time of the control pulse by the pulse step S each time the fixed time Ts elapses.

Next, the stable period modulation table will be described.

In the second period T2, the control unit 22 repeats the step number n of times to decrease the ON time of the control pulse by the pulse step s each time the fixed time Ts elapses. In the fourth period T4, the control unit 22 repeats increasing the on-time of the control pulse by the pulse step s every time the fixed time Ts elapses by the number of steps n.

The pulse step S in the second period T2 and the fourth period T4 of the transient period modulation table is set to have a larger rate of change than the pulse step S in the second period T2 and the fourth period T4 of the stable period modulation table. , the inrush current of the magnetron 10 is suppressed.

As described above, the control unit 22 performs the switching operation of the semiconductor element 18 according to the transition period modulation table different from the stable period modulation table within a predetermined time (for example, 4 seconds to 5 seconds) from the start of the magnetron 10. to control. Specifically, the control unit 22 controls the ON time of the semiconductor element 18 so as to suppress the inrush current according to the transient modulation table.

According to the embodiment, a heating cooker 100 is provided in which rush current flowing through the semiconductor element 18 is suppressed.

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-described embodiments, and can be implemented in various aspects without departing from the spirit of the present invention. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be omitted from all components shown in the embodiments. In order to facilitate understanding, the drawings mainly show each component schematically, and the number of each component shown in the figure may differ from the actual number for convenience of drawing preparation. Also, each component shown in the above embodiment is an example and 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 The present invention can be used in the field of heat cookers.

10 magnetron 12 rectifier 14 step-up transformer 16 high-voltage rectifier 18 semiconductor element 20 resistance element 22 control unit 100 cooker D1 first terminal D2 second terminal W1 primary winding W2 secondary winding

Claims (4)

a magnetron that generates microwaves;
a rectifier 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 with one end connected 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 with the semiconductor element;
a control unit that controls the switching operation of the semiconductor element based on the unidirectional voltage information and the current information obtained from the resistance element;
with
The control unit controls a transition period modulation table different from a stable period modulation table used during steady operation of the magnetron so that an inrush current flowing through the semiconductor element is suppressed within a predetermined time from the rise of the magnetron. A heating cooker that controls the switching operation according to. 2. The heating cooker according to claim 1, wherein said control unit controls the ON time of said semiconductor device so as to suppress said inrush current according to said transient modulation table. The heating cooker according to claim 1 or 2, wherein the rectifying section includes a full-wave rectifying circuit. The heating cooker according to any one of claims 1 to 3, wherein the semiconductor element is an IGBT (Insulated Gate Bipolar Transistor).

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