KR100628043B1 - Method for checking error of temperature sensing circuit - Google Patents

Abstract

The present invention provides a thermistor whose resistance value Rth varies with temperature change, first and second reference resistors R1 and R2 connected in parallel with each other in series with the thermistor, and second reference resistor R2. In the temperature sensor circuit for selectively sensing the temperature in the high temperature region and the low temperature region having a switching means for controlling the connection state of the, the switching means is turned on in parallel with the first and second reference resistors (R1) (R2) Reading the first divided voltage V1 based on the summation resistance and the resistance of the thermistor; Reading the second divided voltage V2 according to the resistance value of the first reference resistor R1 and the thermistor by turning off the switching means; When the first divided voltage (V1) is less than or equal to the second divided voltage (V2) provides a method for detecting an error of the temperature sensor circuit comprising the step of determining that the switching means is defective and displaying the error state of the switching means.

Accordingly, the present invention can minimize the user inconvenience and improve the reliability of the product by detecting the presence or absence of component abnormalities in the temperature sensor circuit and guiding whether or not an error is displayed and cooking according to the component abnormality state.

Temperature Sensor Circuit, Thermistor, Low Temperature Area, High Temperature Area, Component Defect

Description

Method for checking error of temperature sensing circuit

1 is a circuit diagram showing a temperature sensor circuit used in a low temperature and a high temperature region using one thermistor.

Figure 2 is a graph showing the sensor output according to the temperature in the low temperature and high temperature region

3 is a flowchart illustrating an error detection method of a temperature sensing circuit in a cooking apparatus according to the present invention.

* Explanation of symbols for main parts of the drawings

R1, R2: basic resistance Q1: transistor

1: thermistor 2: micom

The present invention relates to a temperature sensor circuit, and more particularly, to an error detection method of a temperature sensor circuit for detecting a temperature of a low temperature region and a high temperature region using one temperature sensor.

As a cooking apparatus for cooking at home, an electric oven, a microwave oven, a gas range, a gas oven range, and the like are frequently used.

Among them, the electric oven is a cooking apparatus for cooking food using an electric heater as a main heating source, and is commercialized by being mounted on a cook-top such as a compound cooker.

In addition, the microwave oven uses microwaves as a main heating source to heat the object to be cooked in the cooking chamber, and recently, a microwave oven with a heater is provided in order to provide various heating conditions.

In general, the cooking apparatus includes a temperature sensor circuit for sensing the internal temperature of the cooking chamber heated by the heating source.

In cooking equipment, thermistors are mainly used for temperature detection.Thermistors have a negative temperature coefficient (NTC) type that decreases resistance when the temperature increases and a positive temperature coefficient that increases when the temperature increases. ) Type.

1 shows a temperature sensor circuit composed of a PTC type thermistor.

A general temperature sensor circuit is composed of a circuit capable of sensing a temperature in a low temperature region and a high temperature region with one thermistor 1.

As shown in the drawing, the conventional temperature sensor circuit includes a transistor Q1 for switching a connection state between the first and second reference resistors R1 and R2, the second reference resistor R2, and a resistor according to a temperature change. The transistor Q1 is controlled according to the variable thermistor 1 and the temperature region, and the current temperature is determined by the resistance values Rth of the first and second reference resistors R1 and R2 and the thermistor 1. It is composed of a microcomputer (2).

According to this configuration, the microcomputer 2 performs temperature sensing using thermistor 1 by dividing the low temperature region and the high temperature region.

First, when the low temperature region is to be detected, the transistor Q1 is turned on by outputting a control signal through the output port P0.

In this case, since the second reference resistor R2 is connected in parallel with the first reference resistor R1, the microcomputer 2 has a parallel summation resistance (R1 * of the first and second reference resistors R1 and R2). The current temperature is determined based on the voltage divided by the resistance value Rth of R2) / (R1 + R2)) and the thermistor 1.

That is, the microcomputer 2 turns on the transistor Q1 and determines the current temperature corresponding to the voltage level input through the input port P1 using the temperature-specific temperature table for the low temperature region.

On the other hand, if the high temperature area is to be detected, the control signal is output through the output port P0 to turn off the transistor Q1.

In this case, since the second reference resistor R2 is separated, the microcomputer 2 determines the current temperature through the divided voltages of the first reference resistor R1 and the thermistor 1.

In other words, the microcomputer 2 turns off the transistor Q1 and determines the current temperature corresponding to the voltage level input through the input port P1 using the temperature-specific temperature table for the high temperature region.

As shown in FIG. 2, even at the same voltage level, the sensing temperature T1 in the low temperature region and the sensing temperature T2 in the high temperature region are significantly different according to the on / off of the transistor Q1.

In this case, since the parallel summation resistances of the first and second reference resistors R1 and R2 are used in the low temperature region, the slope of the sensor output voltage according to the temperature is relatively larger than the high temperature region.

Therefore, by changing the reference resistance by changing the slope of the sensor output voltage according to the temperature it is possible to sense the temperature of the low temperature region and the high temperature region with only one thermistor (1).

However, in the conventional case, the low temperature region and the high temperature region are selected and used by turning on / off of the transistor, and accurate temperature sensing is impossible in the event of opening or shorting between the terminals (collector-base and collector-emitter) of the transistor. .

In other words, according to the abnormality of the transistor, the cooking temperature is burned or undercooked due to abnormal temperature sensing, which lowers the cooking performance and reduces the user's confidence in the product.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an error detection method of a temperature sensor circuit for detecting a component abnormality of a means for switching a low temperature region and a high temperature region in a temperature sensor circuit.

It is an object of the present invention to provide an error detection method of a temperature sensor circuit which minimizes inconvenience for a user by determining whether cooking proceeds according to an abnormality of a switching means.

In order to achieve the above object, the present invention provides a thermistor whose resistance value (Rth) is variable in accordance with the temperature change, the first and second reference resistor (R1) (R2) connected in parallel to each other in series with the thermistor, In a temperature sensor circuit having a switching means for controlling a connection state of a second reference resistor R2 to selectively sense a temperature in a high temperature region and a low temperature region, the switching means is turned on so that the first and second reference resistors ( Reading the first divided voltage V1 based on the parallel summation resistance of R1) and R2 and the resistance value of the thermistor; Reading the second divided voltage V2 according to the resistance value of the first reference resistor R1 and the thermistor by turning off the switching means; When the first divided voltage (V1) is less than or equal to the second divided voltage (V2) provides a method for detecting an error of the temperature sensor circuit comprising the step of determining that the switching means is defective and displaying the error state of the switching means.

When the switching means is determined to be defective, the present invention reads the divided voltage according to the temperature change for a predetermined time to calculate a slope of the sensor output, and if the calculated slope is greater than a preset reference value, the switching means. Judging by the short state and displaying the temperature sensing error in the high temperature region, and determining the open state of the switching means and displaying the temperature sensing error in the low temperature region when the calculated slope is smaller than a preset reference value. It provides an error detection method of the temperature sensor circuit further comprising a step.

Therefore, according to the present invention, it is possible to minimize the inconvenience of the user and improve the reliability of the product by detecting the presence or absence of component abnormalities in the temperature sensor circuit and guiding whether to display an error or cooking according to the component abnormality.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described.

The present invention relates to a temperature sensor circuit of a cooking apparatus for sensing a heating temperature of a cooking chamber heated by a heat source such as a heater, and is characterized in determining whether there is an abnormality of a circuit element constituting the temperature sensor circuit.

As shown in FIG. 1, a temperature sensor circuit of a cooking appliance includes a thermistor 1 having a resistance value Rth varying with a temperature change, and a first connected to the thermistor 1 in series with each other in parallel. And switching means for controlling a connection state between a second reference resistor (R1) and a second reference resistor (R2), and controlling the switching means for selecting temperature sensing in a low temperature region and a high temperature region. It consists of the microcomputer 2.

At this time, one end of the first reference resistor R1 is connected to the power supply terminal Vcc, the other end is connected to the thermistor 1, and the second reference resistor R2 is parallel to the first reference resistor R1. Connected.

The switching means includes an npn type transistor having a base connected to the output port P0 of the microcomputer 2, an emitter connected to one end of the second reference resistor R2, and a collector connected to the power supply terminal Vcc. It consists of (Q1).

With this configuration, the microcomputer 2 of the present invention outputs a high signal that can turn on the transistor Q1 when performing temperature sensing in a low temperature region and detects temperature sensing in a high temperature region. In this case, a control signal (low signal) for turning off the transistor Q1 is output.

Therefore, the temperature sensing in the low temperature region is input to the divided voltage V1 by the parallel summation resistance of the first and second reference resistors R1 and R2 and the resistance value Rth of the thermistor 1, and then to the low temperature region. The temperature corresponding to the input voltage (V1) level is determined using the temperature table for each voltage.

The temperature detection in the high temperature region is performed by receiving a divided voltage V2 based on the first reference resistance R1 and the resistance value Rth of the thermistor 1 and using a temperature-specific temperature table for the high temperature region. Determine the temperature corresponding to the (V2) level.

In particular, the present invention is characterized in determining whether there is an abnormality in the switching means, that is, the transistor Q1, used to distinguish the low temperature region from the high temperature region.

Referring to Figure 3, the error detection method of the temperature sensor circuit according to the present invention will be described.

First, the microcomputer 2 outputs a control signal for turning on the transistor Q1 of the temperature sensor circuit and reads the first divided voltage V1 input through the input port P1 in the low temperature region (S10). ).

Thereafter, the control signal for turning off the transistor Q1 is output and the second divided voltage V2 input through the input port P1 is read in the high temperature region (S20).

In operation S30, it is determined whether the read first divided voltage V1 is smaller than or equal to the second divided voltage V2.

As a result of the determination (S30), when the first divided voltage V1 read in the low temperature region is larger than the second divided voltage V2 read in the high temperature region, the transistor Q1 exhibits a normal driving state, and thus the low temperature region and the high temperature region. All cooking progress of the area is possible (S40).

Since the parallel sum resistance (R1 * R2) / (R1 + R2) of the first and second reference resistors R1 and R2 is smaller than the first reference resistor R1, the transistor Q1 In the steady state, the first divided voltage V1 has a larger value than the second divided voltage V2.

On the other hand, if the first divided voltage V1 read in the low temperature region is smaller than or equal to the second divided voltage V2 read in the high temperature region, the determination result S30 determines that the transistor Q1 is defective ( S50).

In order to determine whether the transistor Q1 is in an open state or a short state, a heat source (heater, etc.) is driven for a preset time T1 to read a temperature sensor output according to a temperature change, and a temperature from the temperature sensor output. The slope of the rise is calculated (S60).

It is determined whether the slope of the calculated temperature rise is greater than a preset reference value (S70).

In the case of the temperature sensor circuit using one thermistor 1, since the temperature rising slope in the low temperature region is relatively large compared to the high temperature region, the temperature sensor circuit is used to determine whether the transistor Q1 is in a short state or in an open state. can do.

As a result of the determination (S70), when the slope of the temperature rise is greater than the reference value, the transistor Q1 is determined to be 'bad state short'. At this time, when the transistor Q1 is in the short state, temperature sensing in the low temperature region is possible, but temperature sensing in the high temperature region is not possible, so this error is displayed and only cooking in the low temperature region is performed (S80).

On the other hand, if the slope of the temperature rise of the determination result (S70) is less than the reference value, the transistor Q1 is determined to be 'bad open state'. That is, when the transistor Q1 is in an open state, temperature sensing in a high temperature region is possible while temperature sensing in a low temperature region is impossible, so a corresponding error is displayed and only cooking in a high temperature region is performed (S90).

Accordingly, the present invention determines whether the cooking proceeds and displays an error according to whether the temperature region of the cooking to be processed corresponds to a temperature region where the temperature can be sensed after checking the defective parts of the temperature sensor circuit.

The present invention is not limited to the above-described embodiments, and as can be seen in the appended claims, modifications can be made by those skilled in the art to which the invention pertains, and such modifications are within the scope of the present invention.

The error detection method of the temperature sensor circuit according to the present invention described above has the following effects.

The present invention determines whether or not the cooking proceeds according to whether or not the cooking to be carried out by checking the component failure of the temperature sensor circuit corresponds to the temperature range where the temperature can be detected and displays an error.

That is, by preventing the progress of cooking in an abnormal state in advance, it is possible to minimize the inconvenience of the user and improve the reliability of the product.

Claims (2)

The connection state of the thermistor whose resistance value Rth varies with temperature change, the 1st and 2nd reference resistors R1 and R2 connected in parallel with each other and connected in series with the thermistor, and the 2nd reference resistor R2 In the temperature sensor circuit for selectively sensing the temperature in the high temperature region and the low temperature region having a switching means for controlling the, Reading the first divided voltage V1 according to the parallel summation resistance of the first and second reference resistors R1 and R2 and the resistance value of the thermistor by turning on the switching means; Reading the second divided voltage V2 according to the resistance value of the first reference resistor R1 and the thermistor by turning off the switching means; If the first divided voltage V1 is less than or equal to the second divided voltage V2, determining that the switching means is defective and displaying an error state of the switching means. . The method of claim 1, If it is determined that the switching means is defective, calculating a slope of the sensor output by reading the divided voltage according to the temperature change for a predetermined time; Determining the short state of the switching means and displaying a temperature sensing error in a high temperature region when the calculated slope is greater than a preset reference value; And determining the open state of the switching means and displaying a temperature sensing error in a low temperature region when the calculated slope is smaller than a predetermined reference value.

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