JPH0738976Y2 - Integrated circuit device for heating cooker - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an integrated circuit device for home appliances including a temperature sensor such as a microwave oven and an electric rice cooker.

<Prior Art> There are many home electric appliances such as microwave ovens and electric rice cookers that have integrated circuits (1-chip microcomputers) and have improved functions in the market.

The functions of this kind of home electric appliances are increasing year by year.For example, the cooking time is displayed in Arabic numerals on the display device, or a simple English message is displayed in alphabet during cooking. Enrichment is being measured. The required number of input / output ports of an integrated circuit has increased with the enhancement of functions, and an integrated circuit with a large number of input / output ports and a large package size has been demanded.

FIG. 4 is an electric circuit diagram of a main part of a conventional integrated circuit device in a microwave oven, in which 1 is an integrated circuit (LSI) generally called a microcomputer, which is input by a built-in program. Based on the key input from the device 2, a buzzer 3 for alarm sound, a control component 4 such as a relay, or a display tube 5
Etc. control the entire microwave oven.

The display on the display tube 5 is performed by a dynamic drive display signal of a segment signal and a digit signal.

Reference numeral 6 denotes a temperature sensor, and a detachable temperature probe is used in the microwave oven, which contributes to temperature measurement and finish control of the food. The temperature detection circuit 7 using the temperature sensor 6 is a detachable temperature probe R _T and a resistor R ₁ connected in series between the A / D conversion reference voltage (V _REF ) terminal of the integrated circuit 1 and the ground (GND). It is composed of R ₂ and R _3, and has resistance R ₁
The voltage signal at the connection point of the resistor R ₂ and the resistor R ₂ is input to the input port K of the integrated circuit 1 as the output signal of the temperature detection circuit 7.

The resistance value R _{T of} the thermistor built in the temperature probe R _T changes depending on the temperature. The change in the resistance value R _T is converted into an analog voltage signal by the temperature detection circuit 7, and the analog voltage signal is input to the input port K and converted into a digital signal by the A / D conversion circuit in the integrated circuit 1.

The integrated circuit 1 converts the above digital signal into temperature and controls heating and displays the temperature on the display tube 5, but the resistance value is abnormal due to the user forgetting to attach the temperature probe _RT or the thermistor conduction failure. If it is too high, the heating control cannot be performed, so there is a risk that the food will become charred and a fire will occur. Therefore, it is judged (temperature sensor abnormality judgment) and the user is notified and cooking is stopped. There is a need.

That is, it is necessary to detect with high sensitivity the resistance change of the thermistor in the normal temperature measurement state and the high resistance in the conduction failure state of the thermistor.

Therefore, a switching circuit 8 is connected in parallel with the resistor R ₃ and the switching signal of “HIGH” or “LOW” from the S ₀ port of the integrated circuit 1 is connected to the base of the transistor Q ₁ of the switching circuit 8 as shown in FIG. Is output to periodically switch between the normal temperature measurement mode and the thermistor abnormality determination mode.

As shown in the flow chart of FIG. 6, when the “HIGH” signal is output from the S ₀ port of the integrated circuit 1, the resistor R ₃ is short-circuited and the normal temperature measurement mode is set, and the signal is input to the input port K. Voltage Is converted to a digital value n by the A / D conversion circuit, and whether or not the digital value n is within the normal temperature measurement range is compared with the predetermined value (250) to determine if it is within the normal temperature measurement range. The temperature is converted into a temperature and displayed on the display tube 5.

When a "LOW" signal is output from the S ₀ port of the integrated circuit 1, the temperature sensor is set to the abnormality determination mode and the voltage input to the input port K is set. Is converted into a digital value n by the A / D conversion circuit, and whether or not the digital value n is in the conduction failure area of the thermistor is compared with a predetermined value (128). If it is in the conduction failure area, the temperature sensor is detected. Is displayed on the display tube 5. The resistance value of the resistor R ₃ is Is set so that it can be determined that the thermistor has poor conduction.

<Problems to be solved by the device> The S ₀ port of the integrated circuit 1 is an output port that outputs a switching signal of “HIGH” and “LOW”, and the other output signals of “HIGH” and “LOW” are used. There was a possibility that it could be abolished by doing.

<Means for Solving Problems> A dynamic drive display digit signal is used as a switching signal of the switching circuit 8.

<Operation> Since the switching circuit 8 is switched by the digit signal, the S ₀ port of the conventional example becomes unnecessary.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an electric circuit diagram showing the integrated circuit device of the present invention in a microwave oven. The digit signal Di of the digit signal output port of the integrated circuit 1 is connected so as to be used as a switching signal of the switching circuit 8 and S It is the same as the conventional example except that the ₀ port is not required.

The one-digit signal Di is a repetitive signal of "HIGH" and "LOW" as shown in FIG. 2, and although the cycle is different from the switching signal of the conventional example, the same control as the conventional example is performed based on the flowchart of FIG. Done.

<Effect> The integrated circuit device for a heating cooker of the present invention is configured as described above, and detects the temperature of food at a part of the cycle of the digit signal (at the time of signal output) and judges the conduction failure of the temperature sensor at the other part. Therefore, it is possible to reliably prevent overheating shortage and fire due to heating due to erroneous detection of food temperature due to poor conduction of the temperature sensor with a simple configuration, and moreover, the integrated circuit for heating cooker as described above. The apparatus places the food on the turntable, rotates the turntable to heat the food by the heating means, and inserts a detachable temperature probe having a temperature sensor into the food to detect the temperature of the food. When used in a cooking device, it is possible to detect not only the temperature of food but also the fall of the temperature probe, and it is possible to reliably prevent a fire due to overheating caused by the fall of the temperature probe.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of an integrated circuit device of the present invention, FIG. 2 is a waveform diagram of a digit signal, FIG. 3 is a flow chart according to the present invention, and FIG. 4 is a conventional integrated circuit device. Circuit diagram showing the fifth
FIG. 6 is a waveform diagram of the switching signal, and FIG. 6 is a flowchart of the conventional example. Reference numeral 1: Integrated circuit, 5: Display tube 6: Temperature sensor, 7: Temperature detection circuit 8: Switching circuit

Claims (1)

[Scope of utility model registration request] 1. A temperature detection circuit comprising a temperature sensor for detecting the temperature of food and a plurality of resistors connected in series to the temperature sensor, a resistance value of the resistance for temperature measurement, and a continuity failure judgment of the temperature sensor. And a switching circuit for switching to and a temperature detection circuit for inputting an output signal of the temperature detection circuit to output a temperature display signal to display means of dynamic drive and controlling the heating means for heating food by the output signal, In an integrated circuit device for a heating cooker comprising a control means for performing measurement and determination of conduction failure related to the temperature sensor, the switching circuit operates when the temperature of food is detected by the temperature sensor. A transistor for short-circuiting one of them is provided, and the transistor is driven by a signal corresponding to one digit of the digit signal from the control means for driving the display means. An integrated circuit device for a heating cooker, characterized in that the digit signal output terminal of the control means is connected to the base of the transistor for operating.