JPH0541277A - Temperature control device for induction heating cooker - Google Patents

Abstract

PURPOSE:To allow a device to stably function even against noise by comparing voltage inputted into two A/D converter terminals with voltage stored in a memory so as to be converted into temperature, and thereby allowing temperature low in variation to be the temperature of a measured object. CONSTITUTION:In a temperature measurement magnetizing stage 5, voltage at the connection of a base resistor R1 with a thermister 4, is inputted to a first A/D converter input terminal, and voltage at the connection of a base resistor R2 with the thermister 4 is inputted to a second A/D converter terminal. Each voltage is then compared with voltages stored in a memory, so that two results of measurement on the temperature of a pan 9 measured by the thermister 4 can thereby be obtained. These two results of measurement are compared with the result of previous measurement by a temperature determining means 6, so that the result of measurement low in temperature variation is made to be the true result of measurement which is not affected by noise. By this constitution, a temperature control device which stably regulates temperature, can be provided for an induction heating cooker.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for a heating cooker used in general households.

[0002]

2. Description of the Related Art FIGS. 2 to 4 show a temperature measuring method in a general cooking appliance having a temperature control function using a conventional microcomputer.

First, in FIG. 2, Rth is a thermistor of the temperature detecting means, and the resistance value of the thermistor decreases as the temperature rises.

COMP is a comparator that compares the voltages at points a and b, outputs High when point a is a higher voltage than point b, and outputs Low in the opposite case, and outputs the result. Is input to the input 1 terminal of the microcomputer.

R24 to R31 are resistors that change the voltage at point b by dividing the DC power supply by the thermistors Rth and R23 by opening or closing a switch composed of a transistor or the like in the microcomputer.

The operation at that time is shown in FIG. First, in the F section, SW21 to SW28 are in the open state and b
The voltage at the point is a voltage determined by the resistance values of the thermistors Rth and R23. Here, when SW21 is closed, the voltage at the point b is the combined resistance value of R23 and R24 = 1 / like the G part.
(1 / R23 + 1 / R24) becomes the partial pressure of Rth,
When this voltage is compared with the voltage at the point a by the comparator COMP, the output of the comparator COMP is High. As described above, when the SW21 is sequentially opened and closed from the SW21, the voltage at the point b becomes higher than the voltage at the point a at the point H, that is, when the switch SW23 is closed, and the output of the comparator COMP is different from the previous one. Invert. At this time, when the SW23 is closed, the input to the input 1 terminal of the microcomputer is inverted, so that the temperature measured by the thermistor Rth at that time is R
If the temperature is set by the total resistance value of 24 to R26,
It is judged by a microcomputer. When the measured temperature of the thermistor Rth further rises and its resistance value decreases, the output of the comparator COMP does not invert even if SW23 is closed, and the output of the comparator COMP inverts only after SW24 is closed. The total resistance value of R27 is used to judge that the set temperature is reached.

Further, in the conventional circuit configuration of FIG.
The control temperature can be easily changed by changing the resistance values of R31 to R31.

Another conventional temperature measuring method has a circuit configuration shown in FIG. Rth is a thermistor of the temperature detecting means as in FIG. 2, and the resistance value of the thermistor decreases as the temperature rises. R41
Is a resistance, and this resistance value is generally set substantially at the center of the change of Rth in the temperature measurement range by the thermistor.

In the temperature measuring operation according to this configuration, when Rth changes due to a temperature change, the voltage at the point c obtained by dividing the DC power supply Vdd by Rth and R41 is read by the A / D input terminal of the microcomputer according to the change. The resistance value of Rth, that is, the temperature detected by the thermistor is judged by comparing the data read in in advance with the data programmed in the microcomputer. In this configuration, the high speed is achieved as in the first conventional example of FIG. Since such a switching operation is not performed, the noise can be mitigated by the capacitors C1 and C2, etc. even if the noise enters from the thermistor or the like.

2 and 4, the control means controls the high frequency power supply based on the measured temperature result to maintain the temperature of the load as set.

[0011]

However, in the structure of the conventional temperature controller for the heating cooker shown in FIG. 2, which is shown in FIG.
The number of measurement temperature points is limited to the number of output terminals of the microcomputer, and it is impossible to make delicate measurements such as the difference in the slope of temperature change, and malfunctions occur even with large noise generated from the high-frequency power source of the induction heating cooker. There was a problem that there was a fear of.

Further, in the structure of the conventional temperature controller for the heating cooker shown in FIG. 4, although it is possible to absorb a considerable amount of noise, it is determined whether the noise that has entered is a noise or a voltage change due to a temperature change. I couldn't do it.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a temperature control device for an induction heating cooker, which operates stably against a large noise of the induction heating cooker.

[0014]

In order to achieve the above object, the present invention is directed to an induction heating device including a high frequency power source and a heating coil, a direct current power source for outputting a predetermined direct current voltage, and an operation using the direct current power source. A microcomputer having an A / D conversion input terminal and a plurality of output terminals, a thermistor of a temperature detecting element for measuring the temperature of a load such as a pot heated by the induction heating device, and one end of the first reference resistor The other end of the DC power source is connected to one end of the thermistor of the temperature detecting element, the other end of the thermistor of the temperature detecting element is connected to one end of the second reference resistor, and the other end of the second reference resistor is connected. In the circuit connected to the negative output of the DC power supply, the voltage at the connection point of the first reference resistor and the thermistor is input to the first A / D conversion input terminal of the microcomputer, and By the reference resistor and the voltage at the connection point of the thermistor to a second A / D conversion input terminal, the first
The voltage of the A / D conversion input terminal and the voltage of the second A / D conversion input terminal are converted into temperature values corresponding to the voltages input to the respective A / D input terminals, which are stored in the microcomputer in advance, and have a constant cycle. Compared to the previous measurement result of the temperature measurement means for measuring the temperature detected by the thermistor by comparing each temperature and the two measurement temperatures by the two A / D conversion input terminals measured by this temperature measurement means. Based on the output of the temperature determining means and the temperature determining means the measurement result of the small amount of temperature change as the true measurement temperature, so that the predetermined temperature stored in the microcomputer,
And a control means for controlling the output of the induction heating cooker.

[0015]

According to the above configuration, the measurement results obtained by converting the respective voltages input to the two A / D conversion input terminals to the voltage values stored in the memory inside the microcomputer, and separately converting the temperatures into temperatures. Among them, the measurement result with a large temperature change amount is deleted as an erroneous measurement due to noise, and the temperature control is performed with the measurement result with a small temperature change amount as the temperature of the pan of the object to be measured.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of a temperature controller for a heating cooker according to the present invention. In FIG. 1, reference numeral 1 denotes an induction heating device, which is composed of a high frequency power source 1a for generating a high frequency voltage from a commercial AC power source and a heating coil 1b. 2 is a DC voltage Vdd = 5V (D
The DC power source 3 for generating C) has an A / D conversion input terminal and a plurality of output terminals in a microcomputer. 4 is a thermistor which is a temperature detecting element, and measures the temperature of the pan 9 which is a load. 5 is a temperature measuring means,
The first reference resistor R1, the thermistor 4, and the second reference resistor R
DC power supply 2 at both ends of the circuit in which 2 are connected in series in this order.
In the circuit to which the output voltage of
The voltage at the connection point between 1 and the thermistor 4 is input to the first A / D conversion input terminal, and the voltage at the connection point between the second reference resistor R2 and the thermistor 4 is input to the second A / D conversion input terminal. Then, by comparing the voltage input to each with the voltage stored in the memory of the microcomputer 3 in advance, two temperature measurement results of the pot 9 by the thermistor 4 are obtained. Further, the temperature measurement by the temperature measuring means 5 is performed every predetermined period.

Reference numeral 6 is a temperature determining means, which compares the two measurement results measured by the temperature measuring means 5 with the previous measurement result and compares the measurement result with the smaller temperature variation with the previous measurement result with noise. The true measurement result is not affected by.

Numeral 7 is a noise prevention means for attenuating the high frequency noise generated from the induction heating device 1 to prevent the high frequency noise from entering the A / D input terminal and causing the temperature measuring means 5 to malfunction. C1 and electrolytic capacitor C2
It is composed by.

Reference numeral 8 is a control means for controlling the temperature of the pan 9 as a load to be kept at a predetermined temperature based on the measurement result of the memory inside the microcomputer and the temperature measuring means 5.

[0021]

As described above, the effect of the present invention is to provide a direct current power source which outputs a predetermined direct current voltage, a microcomputer having an A / D conversion input terminal and a plurality of output terminals which are operated by the direct current power source, A thermistor of a temperature detecting element for measuring the temperature of a load such as a pan heated by the induction heating device, and one end of the first reference resistor is a positive output of a DC power source and the other end is one end of the thermistor of the temperature detecting element. In the circuit in which the other end of the thermistor of the temperature detecting element and one end of the second reference resistor are connected and the other end of the second reference resistor is connected to the negative output of the DC power supply, The voltage at the connection point of the thermistor is input to the first A / D conversion input terminal of the microcomputer, and the second
The voltage at the connection point between the reference resistance and the thermistor is set to the second A / D
By using the conversion input terminal, the voltage of the first A / D conversion input terminal and the voltage of the second A / D conversion input terminal are input to the respective A / D input terminals stored in advance in the microcomputer. Temperature measurement means for measuring the detected temperature of the thermistor by comparing the converted value of the temperature with respect to the voltage at regular intervals, and two measurements by the two A / D conversion input terminals measured by this temperature measurement means. By providing the temperature determination means for setting the measurement result with a smaller change amount than the previous measurement result among the temperatures as the true measurement temperature,
Since the influence of noise of the high frequency power supply on the temperature measurement can be prevented from becoming large, it is possible to obtain a temperature control device for an induction heating cooker that stably performs temperature adjustment operation.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a heating cooker of a first conventional example.

FIG. 3 is a timing chart showing the operation of the heating cooker of the first conventional example.

FIG. 4 is a configuration diagram of a heating cooker of a second conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Induction heating device 2 DC power supply 3 Microcomputer 4 Thermistor of temperature detecting element 5 Temperature measuring means 6 Temperature determination means 7 Noise prevention means 8 Control means 9 Pan

Claims (1)

[Claims] Claim: What is claimed is: 1. An induction heating device comprising a high frequency power supply and a heating coil, a direct current power supply for outputting a predetermined direct current voltage, an A / D conversion input terminal operated by the direct current power supply, and a plurality of output terminals. A computer, a thermistor of a temperature detecting element for measuring the temperature of a load such as a pan heated by the induction heating device, one end of the first reference resistor is a positive output of a DC power source, and the other end is a thermistor of the temperature detecting element. In the circuit in which the other end of the thermistor of the temperature detecting element and one end of the second reference resistance are connected to each other, and the other end of the second reference resistance is connected to the negative output of the DC power supply, The voltage at the connection point between the reference resistor and the thermistor is input to the first A / D conversion input terminal of the microcomputer, and the voltage at the connection point between the second reference resistor and the thermistor is set at the second A / D conversion input terminal. By the conversion input terminal, the first
The voltage of the A / D conversion input terminal and the voltage of the second A / D conversion input terminal are converted into temperature values corresponding to the voltages input to the respective A / D input terminals, which are stored in the microcomputer in advance, and have a constant cycle. Compared to the previous measurement result of the temperature measurement means for measuring the temperature detected by the thermistor by comparing each temperature and the two measurement temperatures by the two A / D conversion input terminals measured by this temperature measurement means. A temperature determining means for setting a measurement result with a small change amount as a true measurement temperature,
A temperature control device for a heating cooker, comprising: a control means for controlling an output of the induction heating cooker so that a predetermined temperature stored in the microcomputer is reached based on an output of the temperature determining means.