JP3204089B2 - Induction heating cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an induction heating cooker.

[0002]

2. Description of the Related Art In recent years, induction heating cookers have attracted attention in the market for their good heat responsiveness, and are safe and clean because they can be cooked without using fire, and their penetration rate is increasing year by year. I have. However, in cooking fried foods and the like, when the oil is heated, if it is left heated, the temperature will be excessively high.

[0003] Therefore, products having an over-temperature prevention function of detecting the temperature of the insulating member and stopping the heating before the temperature of the load pan excessively increases are increasing. A conventional induction heating cooker will be described.

FIG. 3 is a block diagram showing a configuration of a conventional induction heating cooker provided with a function of preventing an overheating of an insulating member.

In the figure, a main control unit 1 has a microcomputer 2, a D / A converter 3, and an inverter driving unit 4, 5 is an inverter including a heating coil 5a, 6 is a rectifier circuit, and 7 is an electric insulating member. Reference numeral 8 denotes a load pan, 9 denotes a temperature measuring unit, 10 denotes a commercial power supply, and 11 denotes a power switch.

[0006] The operation of the induction heating cooker configured as described above will be described below. When a multi-bit signal is output from the microcomputer 2 in the main control unit 1, the D / A converter 3 outputs an analog signal corresponding to the bit to the inverter driving unit 4. Inverter drive unit 4
Drives the switching element of the inverter 5 according to the on / off time determined by the analog signal of the D / A converter 3. The inverter 5 converts the direct current rectified by the rectifier circuit 6 of the commercial power supply 10 into a high-frequency alternating current, generates a high-frequency magnetic flux in the heating coil 5a, and heats the pot 8 of the load.

Normally, since the microcomputer 2 controls the output of the inverter 5, the temperature of the load pan 8 does not become excessively high even if the load pan 8 is erroneously heated. However, the microcomputer 2 temporarily runs away or is destroyed by the influence of electric noise or the like, and the output of the inverter 5 cannot be adjusted.
If the inverter 5 continues to heat the pot 8 of the load, the temperature of the pot 8 of the load may exceed about 250 ° C. and become excessively high. However, the excessive temperature rise prevention means 12 detects that the temperature of the pot 8 of the load has reached about 250 ° C. based on the measurement result of the temperature measurement unit 9 and stops the output of the D / A converter 3. Therefore, the inverter driving unit 4 stops driving the inverter 5.

[0008]

However, in the above-mentioned conventional induction heating cooker, the drive of the inverter is stopped by the output of the overheating prevention means. However, when the microcomputer runs away, the microcomputer is not operated. There is a possibility that the control signal for driving the inverter at the maximum output is continuously output. In this state, when the temperature of the pot of the load decreases and the temperature of the temperature measuring unit becomes equal to or lower than the second temperature and the overheat prevention means releases the output stop of the D / A converter, the switching element of the inverter is instantaneously connected However, there is a problem in that an overcurrent may flow and the loss may exceed an allowable range and cause a breakdown.

An object of the present invention is to provide an induction heating cooker in which the switching element is not destroyed even if the overheating prevention means releases the output stop of the D / A converter. .

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention converts a rapidly changing output signal of a D / A converter for determining an on / off time of a switching element of an inverter into a slowly changing output signal. This is provided with gradual change means.
By this gradual change means, the rapidly changing output signal of the D / A converter is converted into a gradual output signal and transmitted to the inverter driving unit, so that the switching element is not instantaneously driven to the maximum output, and the loss of the switching element is suppressed. , Can be destroyed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An induction heating cooker according to the present invention
A member and a heating coil disposed opposite to the insulating member.
To convert direct current to high frequency alternating current and apply high voltage to the heating coil.
An inverter for supplying frequency current, and an output of the inverter.
A microcomputer for performing force control;
Outputs analog signals according to the multi-bit output of the computer
D / A converter, and an analog signal of the D / A converter
On'o of switching elements of said inverter on the basis of
An inverter drive for determining and driving the
The temperature of the member or the negative
A temperature measuring unit for measuring the temperature of the loading pan, and the temperature measuring unit
The temperature of the insulating member measured at the temperature is equal to or higher than the first temperature.
When the output of the D / A converter is detected,
And outputs the signal to the microcomputer.
An overheating prevention means for outputting a signal for stopping the control of the burner;
When the temperature overheating prevention unit detects that the temperature of the insulating member measured by the temperature measurement unit has become equal to or lower than the second temperature, the unit outputs a signal for canceling the output stop of the D / A converter. the output signals of the control unpause the inverter microcomputer after a predetermined time has elapsed, the My
The computer stops the control stop of this inverter.
When a signal is input, the output of the inverter will gradually increase.
Control .

[0012] Thus, since the microcomputer can perform gradual control output after canceling the output stop of the D / A converter, the switching element is not instantaneously driven to the maximum output, the loss of the switching element is suppressed, and the switching element is destroyed. Can be eliminated.

[0013]

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIG.

The same parts as those shown in the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

In the figure, reference numeral 13 denotes a gradual change means constituted by a capacitor or the like, which has a time constant for the analog signal of the D / A converter 3 to gently change the output.

The microcomputer 2 outputs a bit signal corresponding to the output of the inverter 5. The D / A converter 3 outputs an analog signal corresponding to the bit signal to the inverter driving unit 4. The inverter drive unit 4 controls the switching elements based on the analog signal so that the inverter output becomes maximum when the bit signal is maximum, and the inverter output is minimum when the bit signal is minimum.

The operation of the induction cooking device configured as described above will be described below. When the microcomputer 2 is controlling the inverter 5 at the maximum output, and the microcomputer 2 runs out of control with the maximum output continued due to temporary electric noise, the pot 8 of the load is continuously heated. Then, the temperature detected by the temperature measuring section 9 is about 25.
When the temperature reaches 0 ° C., the excessive temperature rise prevention means 12 lowers the analog signal output of the D / A converter 3 to a level at which the inverter 5 stops. When the temperature of the pot 8 of the load whose heating has been stopped decreases and the temperature detected by the temperature measuring unit 9 reaches about 230 ° C., the overheating prevention means 12 returns the output of the D / A converter 3 to the original state. At this time, the output of the D / A converter 3 rises in about 4 ms from about 0 V corresponding to the stop of the inverter to about 4.2 V corresponding to the maximum output of the inverter. Slow change means 13 is D
A time constant is provided so that the rise time of the output of the / A converter 3 is about 40 ms. As a result, the switching element of the inverter is not driven at the maximum output instantaneously,
Loss can be suppressed and destruction can be eliminated.

Embodiment 2 Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

In the figure, the output of the overheating prevention means 12 is connected to the output of the D / A converter 3 and
It is also connected to the microcomputer 2.

The operation of the induction heating cooker configured as described above will be described below. When the microcomputer 2 is controlling the inverter 5 at the maximum output, and the microcomputer 2 runs out of control with the maximum output continued due to temporary electric noise, the pot 8 of the load is continuously heated. Then, the temperature detected by the temperature measuring section 9 is about 25.
When the temperature reaches 0 ° C., the excessive temperature rise prevention means 12 lowers the analog signal output of the D / A converter 3 to a level at which the inverter 5 stops. At the same time, the microcomputer 2 outputs an output for stopping the control of the inverter. At this time, when the electrical noise is eliminated and the microcomputer 2 returns to the normal state, the control output of the inverter can be stopped by the output of the overheating prevention means 12. Thereafter, the temperature of the pot 8 of the load whose heating has been stopped decreases, and the temperature measurement unit 9
When the detected temperature of the temperature reaches about 230 ° C.,
Releases the output stop of the D / A converter 3 and simultaneously outputs the control output stop release of the inverter to the microcomputer 2. Thus, the microcomputer 2 gradually increases the output from the stopped state to the maximum output before the stop.
As a result, the switching element of the inverter is not instantaneously driven to maximum output, so that loss can be suppressed and destruction can be eliminated.

Embodiment 3 Hereinafter, a third embodiment of the present invention will be described with reference to FIG.

In the present embodiment , the overheat prevention means 12 described in the second embodiment is configured to provide a time difference between the release of the output stop to the D / A converter 3 and the release of the output stop to the microcomputer 2. . The temperature detected by the temperature measuring section 9 is about 230
When the temperature reaches ° C, the overheat prevention means 12 cancels the output stop of the D / A converter 3, and outputs the control output stop release of the inverter to the microcomputer 2 after about 100 ms. Accordingly, when the microcomputer 2 starts controlling the inverter, the output of the D / A converter 3 is always released, so that the switching element is driven by the gradual control of the microcomputer 2 to suppress loss and eliminate destruction. Becomes possible.

[0023]

According to the present invention, there is provided an overheating prevention means.
The start of switching element drive at the time of force stop
The loss of the switching element
Therefore, the reliability of the inverter is further improved.
You.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an induction heating cooker according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an induction heating cooker according to second and third embodiments of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional induction heating cooker.

[Explanation of symbols]

 2 Microcomputer 3 D / A converter 4 Inverter driving unit 5 Inverter 5a Heating coil 7 Insulating member 9 Temperature measuring unit 12 Overheating prevention means 13 Slow change means

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shinobu Machida 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-112689 (JP, A) JP-A-62- 10892 (JP, A) JP-A-59-154790 (JP, A) JP-A-62-188196 (JP, A) JP-A-5-114473 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 6/12

Claims (1)

(57) [Claims] A first insulating member disposed between the insulating member and the insulating member;
Including a heating coil, which converts DC to high-frequency AC,
An inverter for supplying a high-frequency current to the heating coil;
Microcomputer for controlling the output of the inverter
And according to the multi-bit output of the microcomputer.
A D / A converter that outputs an analog signal;
Switch of the inverter based on the analog signal of the converter.
Inverter that determines and drives the on / off time of the switching element
A drive unit and a temperature of the insulating member or the high-frequency current
Temperature measuring unit that measures the temperature of the pot of the load heated by the
And the temperature of the insulating member measured by the temperature measuring unit is
Upon detecting that the temperature has become equal to or higher than the first temperature, the D / A conversion is performed.
The output signal of the converter is stopped.
Output a signal to the computer to stop the control of the inverter
An excessive temperature rise prevention means, wherein the temperature excess rise prevention means cancels the output stop of the D / A converter when detecting that the temperature of the insulating member measured by the temperature measuring section has become equal to or lower than the second temperature. after outputting the signal, and outputs a signal of the control unpause the inverter to the microcomputer after elapse of a predetermined time, the microcomputer, the inverter
When the control stop release signal is input, the inverter
Induction heating cooker that controls to increase the output of the .