JPH05113373A - Temperature sensing device - Google Patents

Abstract

PURPOSE:To obtain a temperature sensing device which can determine a temperature accurately without being affected by ON resistance of a semiconductor switch when the resistance of a resistor which is connected in series to a temperature sensor by the semiconductor switch is switched. CONSTITUTION:When a resistor R11 is connected in series to a temperature sensor 1, semiconductor switches S1 and S3 are turned on by a control signal from an output terminal O1 of a microcomputer 2. When a resistor R12 is connected in series to a temperature sensor 1 by a microcomputer 2. semiconductor switches S2 and S4 are turned on by a control signal from an output terminal O2 of the microcomputer 2. Since an A/D conversion circuit in the microcomputer 2 obtains a reference voltage BREF via the semiconductor switches S1 and S2 where the resistors R11 or R12 are connected in series to the temperature sensor 1, no error is induced in a conversion value even if the ON resistances of the semiconductor switches S1 and S2 vary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature determination device.

[0002]

2. Description of the Related Art FIG. 4 shows a temperature detection circuit for using a temperature sensor 1 such as a negative characteristic thermistor and taking out a change in resistance value according to the temperature detected by the temperature sensor 1 as a voltage change. In the detection circuit, the temperature sensor 1 is connected to the DC voltage source V _CC via the series resistor R ₁ so that the voltage V _TH across the temperature sensor 1 that changes due to the change in the resistance value of the temperature sensor 1 depending on the detected temperature is taken out. Is becoming

The temperature determination device is capable of A / D converting the voltage V _TH across both ends and taking it into a microcomputer (hereinafter abbreviated as a microcomputer) to determine the detected temperature and perform temperature control based on this determination. is there. By the way, there has recently been provided a heating cooker which detects the pot bottom temperature by the temperature sensor 1 and controls the gas supply of the heating means, for example, the gas burner according to the detected pot bottom temperature.

When the heating temperature is controlled by detecting the pot bottom temperature as described above, the temperature detection circuit is as wide as about 60 ° C. to about 350 ° C. Therefore, the temperature detecting circuit as shown in FIG. 4 is used. In this case, the relationship between the temperature detected by the temperature sensor 1 and the voltage across both terminals V _TH (maximum 5 V) is as shown in FIG.
The amount of change in voltage in the low temperature region and the high temperature region was small, and fine control could not be performed.

When the temperature sensor 1 is disconnected or short-circuited, it is necessary to stop heating. For the above reasons, the microcomputer determines whether the voltage change due to disconnection or short-circuit or the voltage change due to temperature change. Becomes difficult, and therefore, it is necessary to deal with the problem by using an external circuit, which leads to an increase in cost. Therefore, there is a method in which the value of the resistance connected in series to the temperature sensor 1 is switched so that the temperature detection range is switched between high (a) and low (b) as shown in FIG.

FIG. 6 shows a conventional temperature determination device for performing this switching. In the temperature detection circuit, a series circuit of a resistor R ₁ and a temperature sensor 1 is connected to a DC voltage source Vcc and is connected in parallel with the resistor R ₁ . Semiconductor switch S and resistor R ₂
And the A series circuit semiconductor switch S is a high resistance value of only the resistor R ₁ to the temperature sensor 1 connected in series when the off, the resistor R ₂ in parallel to the resistor R ₁ when the semiconductor switch S is ON The resistance connected in series with the temperature sensor 1 has a low resistance value.

A microcomputer 2 having a built-in A / D conversion circuit is used as a circuit for taking in the voltage V _TH across the temperature sensor 1 and determining the temperature.
The voltage V _TH across the temperature sensor 1 is connected between the A / D input terminal I _AD and the Vss terminal for the D conversion circuit to provide a built-in A / D
The D conversion circuit performs A / D conversion of the voltage V _TH between both ends using the voltage taken in the V _REF terminal as a reference voltage, and performs temperature detection and control processing based on the A / D converted digital value. is there. Here, the microcomputer 2 is a DC voltage source Vc
are connected with the Vcc terminal, a V _REF terminal of the internal A / D converter circuit to c. Further, a control signal for the semiconductor switch S for resistance value switching is output from the output terminal O, and the control signal is output from the output terminal O according to the detected temperature region to turn on / off the semiconductor switch S, The value of the resistor connected in series with the sensor 1 is switched.

[0008]

The voltage V _TH across the temperature sensor 1 is V _TH = (Vcc x resistance value of the temperature sensor 1) / (R ₁ + temperature sensor 1 when the semiconductor switch S is off. When the semiconductor switch S is on, V _TH = (Vcc × resistance value of temperature sensor 1) / {[(R ₂
× ON resistance of the semiconductor switch S) / (R ₂ + ON resistance of the semiconductor switch S)] + resistance value of the temperature sensor 1}, and when the semiconductor switch S is OFF, there is no problem.
When the semiconductor switch S is ON, there is a problem that the ON resistance R of the semiconductor switch S cannot be ignored and accurate temperature determination cannot be performed.

Further, when the ON resistances of the semiconductor switches S are varied, there is a problem that even if the same circuit is used, the voltage V _TH across the temperature sensor 1 is greatly different, and a stable performance circuit cannot be manufactured. Of course, if a mechanical switch such as an electromagnetic relay is used, the above-mentioned variation due to the on-resistance is eliminated, but there is a problem that the mounting area of the board is increased at the time of mounting the component and the cost is further increased.

The present invention has been made in view of the above problems, and an object thereof is to turn on the resistance of a semiconductor switch when the value of the resistance connected in series to the temperature sensor is switched using the semiconductor switch. An object of the present invention is to provide a temperature determination device capable of performing accurate temperature determination without the influence of the above.

[0011]

To achieve the above object, the present invention provides a temperature sensor having a temperature-resistance characteristic, a plurality of series resistors for converting a resistance change amount of the temperature sensor into a voltage, and A / D is a semiconductor switch that switches and connects the series resistance to the temperature sensor according to the temperature detected by the temperature sensor, and the voltage across the temperature sensor that is connected to the DC voltage source via the series resistance and the semiconductor switch is A / D. Convert A
A / D conversion means, a correction means for correcting the conversion value of the A / D conversion means according to the ON resistance value of the semiconductor switch connected in series to the temperature sensor, and the A / D corrected by the correction means.
And a determination unit that determines the temperature detected by the temperature sensor based on the D-converted value.

[0012]

According to the above configuration of the present invention, since the series resistance is switched and connected to the temperature sensor according to the temperature detected by the temperature sensor, a voltage across the temperature sensor that can be determined from a low temperature to a high temperature can be obtained. Therefore, the short circuit and the disconnection of the temperature sensor can be detected by the conversion output of the A / D conversion means.

Further, since the conversion value of the A / D conversion means can be corrected by the correction means in accordance with the on-resistance value of the semiconductor switch, the influence of the variation in the on-resistance value of the semiconductor switch is eliminated, so that the difference between the circuits. There is an effect that a temperature determination error is eliminated and a circuit with stable performance can be manufactured. Further, since a semiconductor switch is used, the mounting area of the board can be reduced and cost can be reduced as compared with the case where a mechanical switch is used. Can be achieved.

[0014]

EXAMPLES The present invention will be described below with reference to examples. (Embodiment 1) FIG. 1 shows a circuit of this embodiment. In the circuit of this embodiment, a resistor R ₁₁ having a high resistance value and a resistor R ₁₂ having a low resistance value are used, and the respective resistors R ₁₁ and R ₁₂ are used. Is connected to the temperature sensor 3 and the other end is connected to the DC voltage source Vcc via semiconductor switches S ₁ and S _{2, respectively,} and the V _REF terminal of the built-in A / D conversion circuit of the microcomputer 2 is connected to the semiconductor switch S 1. ₃ ,
The S ₄ respectively via connection point between the semiconductor switch S ₂ and the resistor R _12, and connected to a connection point between the semiconductor switch S ₁ and the resistor R _11, the output terminal O of the semiconductor switch S _2, S ₄ the microcomputer 2 It is turned on / off by the control signal from ₂ , and the semiconductor switches S ₁ and S ₃ are turned on / off by the control signal from the output terminal O ₁ of the microcomputer 2.

When the resistor R ₁₁ is connected to the temperature sensor 1 in series, the semiconductor switches S ₁ and S ₃ are turned on by the control signal from the output terminal O ₁ of the microcomputer 2, and the resistor R ₁₂ is turned on.
Is connected to the temperature sensor 3 in series, the semiconductor switch S ₂ is controlled by the control signal from the output terminal O ₂ of the microcomputer ₂ .
Turn on S ₄ . In this embodiment, the temperature sensor 1 has a resistance R
_Since the reference voltage V _REF of the A / D conversion circuit built in the microcomputer ₂ is obtained via the semiconductor switch S ₁ or S _{2 in} which ₁₁ or R ₁₂ are connected in series, there is a variation in the on-resistance of the semiconductor switches S ₁ and S _2. However, since the reference voltage V _REF of the A / D conversion circuit also changes in accordance with this, the variation in the ON resistance is corrected, and no error occurs in the conversion value of the A / D conversion circuit. The microcomputer 2 can accurately determine the temperature, and the control based on the temperature determination can also be accurately performed.

FIG. 2 shows an example in which the present embodiment is used for controlling the temperature of a heating and cooking apparatus. The temperature sensor 1 is brought into contact with the bottom of a pan 6 placed on a Gotoku 3 and heated by a gas burner 4. The temperature sensor 1 is adapted to detect the pot bottom temperature. The voltage V _TH across the temperature sensor 1 is taken into the temperature determination device 5 having the same configuration as the device of the present invention shown in FIG. This taken-in voltage signal is A / D converted by the microcomputer 2 of the temperature determination device 5 to determine the detected temperature. At the start of heating, the semiconductor switch S ₁ is turned on to turn on the high resistance resistor. By connecting R ₁₁ in series to the temperature sensor 1 and setting the temperature detection range to the low temperature range shown in FIG. 7B, the temperature detected by the temperature sensor 1 rises and the voltage V _{TH at} both ends falls below the point A in FIG. When it is determined that the temperature has been detected, the microcomputer 2 turns off the semiconductor switch S ₁ and turns on the semiconductor switch S ₂ to switch the resistance connected in series with the temperature sensor 1 to the low resistance value resistor R ₁₂ , The detection range is set to the high temperature range shown in FIG.

Eventually, the temperature detected by the temperature sensor 1 becomes a constant temperature.
When it reaches the limit, the microcomputer 2 consists of a solenoid valve and a proportional control valve.
Gas supply to the gas burner 4 by controlling the gas supply controller 7
Shut off or reduce the gas burner 4 to extinguish, or
Set the gas burner 4 to a low heat to prevent overheating. This fire extinguishing
The temperature detected by the temperature sensor 1 drops due to small fire.
Both-end voltage V _THIs higher than point B, the semiconductor switch
S₁, S₃The semiconductor switch S₂,
S_FourAnd turn off the resistor connected to the temperature sensor 1.₁₂Or
R₁₁Switch to.

In the above operation, the semiconductor switch S ₃ ,
ON S _4, detection not influenced by the ON resistance of the semiconductor switch S ₁ or S ₂ for the reference voltage V _REF of the internal A / D converter of the microcomputer 2 obtained via the semiconductor switches S ₁ or S ₂ by off Can judge temperature, gas burner 4
The control of gas supply can be controlled accurately. In addition, 8 in FIG. 2 is a main plug.

Example 2 In Example 1, the temperature sensor
The resistance value to be connected in series with the ₁₁, R
₁₂This is done by switching the
Then, as in the conventional example of FIG.₁To
The temperature sensor 1 is connected to the DC voltage source Vcc via
Resistance R₁In parallel with the resistor R via the semiconductor switch S₂To
Connection, and connect a high resistance resistor in series with the temperature sensor 1.
In this case, turn off the semiconductor switch S and turn on the resistor R₁Warm only
Temperature sensor 1 connected in series and a low resistance resistor
Turn on the semiconductor switch S when connecting in series with the sensor 1.
And resistance R₁Resistance R₂Connected in parallel and this parallel circuit
It is connected in series to the temperature sensor 1.

The V _REF terminal of the built-in A / D conversion circuit of the microcomputer 2 is connected to the DC voltage source Vcc through the semiconductor switch S ₅ and also the semiconductor switch S ₆
Is connected to the connection point between the semiconductor switch S and the resistor R ₂ via the resistor, and when the semiconductor switch S is off, that is, the resistor R ₁
When only one is connected to the temperature sensor 1, the semiconductor switch S ₅ is turned on by the control signal from the output terminal O ₂ of the microcomputer ₂ to set the reference voltage of the built-in A / D conversion circuit to the semiconductor switch S 2.
_{When the} semiconductor switch S is turned on by the control signal from the output terminal O ₁ of the microcomputer 2 in order to connect the parallel circuit of the resistors R ₁ and R ₂ to the temperature sensor 1, the semiconductor switch S ₅ is turned off. Semiconductor switch S ₆
Is turned on by the same control signal as that of the semiconductor switch S, and the reference voltage of the built-in A / D conversion circuit is obtained through the semiconductor switch S connected in series with the resistor R _2. By changing the reference voltage by the ON resistance of the ON resistance of the semiconductor switch S, the change in the voltage across the sensor 1 can be corrected and absorbed during A / D conversion.

[0021]

According to the present invention, a temperature sensor having a temperature-resistance characteristic, a plurality of series resistors for converting a resistance change amount of the temperature sensor into a voltage, and the series resistor are controlled according to the temperature detected by the temperature sensor. A / D is used to convert the voltage across the semiconductor switch connected to the sensor and the voltage across the temperature sensor connected to the DC voltage source via the series resistor and the semiconductor switch.
A / D conversion means for converting, correction means for correcting the conversion value of the A / D conversion means according to the ON resistance value of the semiconductor switch connected in series to the temperature sensor, and A / D corrected by the correction means. Since the determination means for determining the temperature detected by the temperature sensor based on the D-converted value is provided, the series resistance can be switched and connected to the temperature sensor according to the temperature detected by the temperature sensor. Up to high temperature,
The voltage across the temperature sensor that can be judged is obtained, and as a result, the short circuit and disconnection of the temperature sensor can be detected by the conversion output of the A / D conversion means, and the A / D value can be changed according to the ON resistance value of the semiconductor switch.
Since the conversion value of the conversion means can be corrected by the correction means, the influence of the variation in the ON resistance value of the semiconductor switch is eliminated, so that there is no temperature judgment error between the circuits and a circuit with stable performance can be manufactured. Further, since the semiconductor switch is used, there is an effect that the mounting area of the substrate can be reduced and the cost can be reduced as compared with the case where the mechanical switch is used.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a heating control device using the first embodiment of the present invention.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional temperature detection circuit.

FIG. 5 is a voltage vs. detected temperature characteristic diagram of the temperature sensor of the circuit of FIG.

FIG. 6 is a circuit diagram of a temperature determination device using another conventional temperature detection circuit.

FIG. 7 is a voltage vs. detected temperature characteristic diagram of the temperature sensor of the circuits of FIGS. 3 and 6;

[Explanation of symbols]

1 Temperature Sensor 2 Microcomputer S _{1 to} S ₄ Semiconductor Switch R ₁₁ , R ₁₂ Resistance R V _REF Reference Voltage O ₁ , O ₂ Output Terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akito Hayano 1-152 Minami-shi Oka, Minato-ku, Osaka City Harman Co., Ltd.

Claims (1)

[Claims] 1. A temperature sensor having a temperature-resistance characteristic, a plurality of series resistors for converting a resistance change amount of the temperature sensor into a voltage, and the series resistor is switched to the temperature sensor according to a temperature detected by the temperature sensor. A / D which converts the voltage across the semiconductor switch to be connected, and the voltage across the temperature sensor connected to the DC voltage source via the series resistor and the semiconductor switch.
D conversion means, correction means for correcting the conversion value of the A / D conversion means according to the ON resistance value of the semiconductor switch connected in series to the temperature sensor, and A / D corrected by the correction means
A temperature determination device comprising: a determination unit that determines the temperature detected by the temperature sensor based on the converted value.