JPH09320750A - Cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the safety of a cooker in inexpensive constitution, even if water is splashed by arranging a signal pattern wiring of a switching element between high voltage pattern wirings, and fusing a fuse by the short circuit between the high voltage pattern wirings. SOLUTION: AC current of a commercial power source is supplied to a rectifier through a fuse, and DC current obtained is supplied to an inverter circuit parallel to a smoothing capacitor. High-frequency current produced with a resonance capacitor and a switching element is supplied to a heating coil, and a highfequency magnetic field is generated to heat a cooking pot. In a copper foil side of a printed circuit board 13 of a cooker, a signal pattern wiring 16 of about 15V between an inverter driving circuit and the switching element 5 is wired between a high voltage side pattern wiring 14 of about 140V of a smoothing capacitor 9 and a low voltage side pattern wiring 15 of about 14V. When short circuit occurs from attaching of water, an input terminal of the switching element 5 is broken, a short circuit is generated between a collector and an emitter, and the fuse is blown.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an induction heating type cooking device.

[0002]

2. Description of the Related Art In recent years, induction heating type cookers have become popular in order to cook and cook delicious rice. Conventionally, the circuit of the induction heating type cooker is composed of a rectifier circuit, a fuse, an inverter circuit, a drive circuit, and a control circuit, and each part is electrically formed by a pattern formed on the copper foil surface. Were connected to each other.

[0003]

However, in the cooker adopting the conventional induction heating system as described above, water or spilled liquid flows into the inside of the cooker main body from the gap of the cooker main body, and the water is blown onto the printed wiring board. If liquid is dripped and liquid is accumulated on the parts or the patterns connecting the parts, the patterns connecting the terminals of the parts or the parts may be short-circuited.

In particular, the inverter circuit is constructed so that a high voltage exceeding 600 V is applied between the pattern and component terminals during heating oscillation, and the high voltage part and the low voltage part are short-circuited. If the liquid drops completely, the liquid may cause a current leak on the substrate, which may cause tracking.

Then, as a countermeasure, a part or a terminal is connected.
Costs increase by covering with a coating agent, securing the distance between the patterns to the extent that liquid does not short circuit, and using an expensive printed wiring board with high tracking resistance. There was also.

The present invention solves the above-mentioned conventional problems, and provides a cooker which is inexpensive and ensures safety even when liquid such as water splashes on the copper foil side of a printed wiring board. The purpose is to

[0007]

In order to achieve the above object, a cooker according to the present invention comprises a commercial power source, a rectifier circuit for converting an alternating current of the commercial power source into a direct current, and a high frequency magnetic field connected to the rectifier circuit. An inverter circuit including a heating coil that generates and heats a pot, a resonance capacitor that forms a resonance circuit together with the heating coil, and a switching element that is connected to the resonance circuit and that generates a resonance current; and the switching circuit. A drive circuit for driving the element, a control circuit for controlling the drive circuit for cooking control, and a printed wiring board on which at least the rectifier circuit, fuse, and inverter circuit are mounted, and the printed wiring board is provided with water. A liquid leaks between the high-voltage pattern wiring and the high-voltage pattern wiring where current leakage occurs and tracking occurs due to the adhesion of liquid such as It has a configuration in which wire the down - more current Li - signal to destroy the switching element when the click occurred pattern.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, even if a liquid such as water drops and scatters on a printed wiring board and a current leak occurs between high voltage pattern wirings and tracking occurs, a switching element is operated. By breaking, the fuse can be effectively blown.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram of a cooking device according to an embodiment of the present invention. Reference numeral 1 is a pot for putting water and rice, and 2 is a heating coil for heating the pot 1.
Reference numeral 3 is an inverter circuit, which is a resonance capacitor 4 which forms a resonance circuit with the heating coil 2 and an IGBT which is a switching element which is connected to the resonance circuit and generates a resonance current.
The heating coil 2 is provided with a high frequency current. Reference numeral 6 is a rectifier that rectifies the commercial power supply 7 into direct current, and 8 is a fuse connected to the rectifier 6 and the commercial power supply 7. When the fuse 8 is melted, the power supply to the rectifier 6 is stopped. . Reference numeral 9 is a smoothing capacitor that smoothes the output of the rectifier 6. Reference numeral 10 is an inverter drive circuit that sends a drive signal to the switching element 5, and 11 is a micro computer (hereinafter referred to as a microcomputer) that controls the inverter drive circuit 10 for controlling cooking, and a key switch 12 Input information is given with. The inverter circuit 3, the rectifier 6, the fuse 8 and the smoothing capacitor 9 are mounted on a printed wiring board (not shown).

FIG. 2 is an external view of a printed wiring board according to an embodiment of the present invention as viewed from the component mounting surface. Thirteen
1 is the printed wiring board described in FIG. 1 and is equipped with a resonance capacitor 4, an IGBT 5, a rectifier 6, a fuse 8 and a smoothing capacitor 9, and the pattern wiring for connecting each component is a copper foil surface on the back side. Is wired to.

FIG. 3 shows a part of an external view of a printed wiring board according to an embodiment of the present invention as seen from the copper foil side. However, the parts on the opposite side cannot be seen, so the location is shown by the dotted line. Reference numeral 9 is a smoothing capacitor arranged on the component mounting surface, 14 is a high voltage side pattern wiring of the smoothing capacitor 9, which is connected to the high voltage side output terminal of the rectifier 6, and 15 is a low voltage side pattern. It is connected to the low-voltage side output terminal of the rectifier 6 by a wiring. Reference numeral 16 is a signal pattern wiring for connecting the signal input terminal of the IGBT 5 arranged on the component mounting surface and the inverter drive circuit 10. The high voltage side pattern wiring 14 and the low voltage side pattern wiring 15 are provided. Are wired between.

Next, the operation in this configuration will be described with reference to FIG.
This will be described with reference to FIG. First, when information is input to the microcomputer 11 from the key switch 12 by the user, the microcomputer 11 drives the IGBT 5 through the inverter drive circuit 10 according to the cooking sequence stored in advance, and the inverter circuit 3 To oscillate. Inverter circuit 3
High frequency current is supplied to the heating coil 2 by the oscillation of
Heat pan 1. When the voltage of the commercial power source 7 is 100V, I
Between the terminals of GBT5, the inverter is stopped, about 140V,
A high voltage of 600 V or higher is generated during oscillation, and a high voltage of 600 V or higher is also applied to both ends of the resonance capacitor 4 during oscillation. Further, a high voltage of about 140 V is always applied between the high voltage side pattern wiring 14 and the low voltage side pattern wiring 15 at both ends of the smoothing capacitor 9.

On the other hand, from the inverter drive circuit 10 to the IGB
The voltage of the drive signal output to T5 is about 20V and IGBT5
The withstand voltage of both the signal input terminal and the inverter drive circuit 10 is about 25V. The driving power source of the microcomputer 11 is 5V.

When liquid such as water adheres between the high voltage side pattern wiring 14 and the signal pattern wiring 16 which are wired as described above and short-circuits, the signal pattern wiring 16 and the IGB are connected.
A voltage of about 140 V is applied to the signal input terminal of T5, which exceeds the withstand voltage of the signal input terminal of the IGBT5.
The signal input terminal of GBT5 is destroyed. When the IGBT 5 is destroyed, the collector-emitter is short-circuited, so that an overcurrent flows into the fuse and the fuse 8 is melted.

As described above, according to the embodiment of the present invention, the short circuit between the high-voltage side pattern wiring 14 and the signal pattern wiring 16 destroys the IGBT 5 and causes an overcurrent to the fuse 8. Since the flow fuse 8 is blown out, the power supply to the circuit can be stopped. Although the rice cooker is shown in the embodiment, it goes without saying that it may be a cooker such as a cooking pot.

[0016]

As described above, according to the present invention, the IG is generated by the short circuit between the high voltage side pattern wiring and the signal pattern wiring.
By breaking the BT and melting the fuse, the voltage application to the continuous circuit can be stopped, which prevents the tracking from progressing and prevents liquid from entering the cooker with an inexpensive structure. On the other hand, a safe cooking device can be realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a cooker according to an embodiment of the present invention.

FIG. 2 is an external view of a printed wiring board on the component mounting surface side of the cooking device.

[Fig. 3] Same as above, external view of the printed wiring board on the copper foil side of the cooking device

[Explanation of symbols]

 1 Pan 2 Heating Coil 3 Inverter Circuit 4 Resonant Capacitor 5 IGBT (Switching Element) 6 Rectifier 7 Commercial Power Supply 8 Fuses 9 Smoothing Capacitor 10 Inverter Drive Circuit 11 Micro Computer (Microcomputer) 12 Key Switch 13 Printed wiring board 14 High-voltage side pattern wiring 15 Low-voltage side pattern wiring 16 Signal pattern wiring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Katagasu 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hiroshi Fukuda 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Koji Niiyama, 1006 Kadoma, Kadoma, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Seiichi Takagura, 1006, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A commercial power source, a rectifier circuit for converting alternating current of the commercial power source into direct current, a fuse connected to the commercial power source and the rectifier circuit, and a high frequency magnetic field connected to the rectifier circuit. An inverter circuit including a heating coil for heating a pan, a resonance capacitor that forms a resonance circuit together with the heating coil, and a switching element connected to the resonance circuit to generate a resonance current; and the switching element. A printed circuit board on which a drive circuit for driving, a control circuit for controlling the drive circuit, at least the rectifying circuit, a fuse and an inverter circuit are mounted and pattern wiring for electrically connecting the respective parts is formed. And the pattern wiring is arranged between the high-voltage pattern wirings so as to destroy the switching element when a current leak occurs on the printed wiring board. A cooker with a signal pattern of an itching element.