JPS62288537A - Temperature detector - Google Patents

Abstract

PURPOSE:To provide a highly accurate temp. detector receiving no effect of a switch means, by simple constitution such that a bridge circuit is constituted of 4 or more electrical loads each containing a temp.-sensitive element and the switch means is not contained in the bridge circuit. CONSTITUTION:A temp.-sensitive element TH1 comprises a resistor having a negative temp. characteristic and constitutes a bridge circuit along with reference resistors RK1, RK2 being electrical loads and a set resistor RS1. The connection point A of the temp.-sensitive element TH1 and the reference resistor RK1 is connected to a power source Vcc to receive DC voltage and the connection point B of the reference resistor RK2 and the set resistor RS1 opposed to the terminal of said power source is connected to the other terminal GND of the power source through a transistor Q11 constituting a switching element. A comparator 11 connects an input terminal so as to detect the potential difference between a terminal other than the aforementioned ones, that is, the connection point C of the reference resistor RK1 and the reference resistor RK2 and the connection point D of the temp.-sensitive element TH12 and the set resistor RS1 to output a comparing result.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a device for detecting and controlling temperature and the like.

Conventional technology Conventionally, means for detecting and controlling temperature etc. are as shown in Figs.
It had a circuit configuration as shown in FIG. The operation of FIG. 4 will be explained as follows.

The resistor R1 and the resistor R2 are for setting a reference voltage, and are set to the same resistance value, and a voltage of XhVc is inputted to the single power of the comparator 2. Transistor Q1 is provided to switch the operation of the series-connected circuit of temperature sensing element 1 and resistor R3, and is normally on.If the on-resistance of transistor Q1 is ignored, then the ten inputs of comparator 2 The inversion level of comparator 2 seen from the side is %Vc. Temperature Tl' to be detected
If the resistance value of the temperature sensing element 1 at C is 'kT, L,
The resistance value of resistor R3 is set to RkTa. That is, when the resistance value of the temperature sensing element 1 becomes RkTa, the input voltage of the comparator 2 is V2VC, which corresponds to the above-mentioned inversion level. When the ambient temperature of temperature sensing element 1 changes, the resistance value of this temperature sensing element changes, so the relationship between this ambient temperature and the point at which the output of comparator 2 is reversed between low and high voltage is based on the temperature around temperature sensing element 1. Temperature is TI
Corresponds to L°C. The microcomputer 3 inputs the output of the comparator 2, and if the temperature characteristic of the temperature sensing element 1 is negative with respect to temperature, the resistance value of the temperature sensing element 1 is greater than RkTa at a temperature lower than Ta°C. The output of the comparator 2 is a low voltage, and conversely, at high temperatures, it becomes smaller than RkTa, so the output of the comparator 2 becomes a high voltage, and the microcomputer 3 inputs this to detect the temperature detected by the temperature sensing element 1. It can detect whether it is a dog or not based on temperature.

Further, the example shown in FIG. 4 can also be applied as shown in FIG. 6th
In the figure, the operations with the same numbers are the same as in Figure 4, and the resistor R
A resistor R4 and a transistor Q2, which operate in the same manner, are connected in parallel to the resistor R4 and the transistor Q1. In this case, the switching of transistor Q1 and transistor Q2 is controlled by the microcomputer 3 so that they operate exclusively, and when transistor Q1 is on and transistor Q2 is off, it is the same as if resistor R4 and transistor Q2 were not present. , and when transistor Q2 is on and transistor Q1 is off, resistor R3
and the transistor Q1 are the same as those without, the circuit configuration is the same as that shown in FIG. 4, and the operation is also the same as that shown in FIG. 4. The advantage of the case of FIG. 6 is that the temperature of the temperature sensing element 1 corresponding to the resistance value set for the resistor R3 or the resistor R4 can be detected, and the temperature can be detected at two points.

Furthermore, by increasing the number of combinations of resistor R4 and transistor Q2, multiple temperatures can be detected.

FIG. 6 shows the circuit configuration of FIG. 4 in which the on-resistance of the transistor Q1 is corrected using a variable resistor R5.

Problems to be Solved by the Invention In the conventional examples shown in FIGS. 4 and 5, the on-resistances of the transistors Q1 and Q2 were ignored. However, in cases where accuracy of the detected temperature is required, or when it is unavoidable to use a transistor with poor on-resistance characteristics for transistor Q1 or Q2,
The on-resistance of this transistor cannot be ignored.

As a countermeasure for this, the selection of resistor R3 or R4 is designed taking into consideration the on-resistance of transistors Q1 and Q2. Also,
As shown in the example of FIG. 6, it has also been considered to correct the on-resistance of the transistor Q1 by adjusting it using a variable resistor R5. However, such correction only works temporarily.

For example, the on-resistance of transistor Q1 has temperature characteristics, and the conditions change depending on the temperature.
There are many problems such as the current flowing through transistors Q1 and Q2 differs depending on the resistance value of transistors Q1 and
Even if the on-resistance shown in Figure 2 is taken into consideration, it is not effective against variations in component characteristics and temperature characteristics due to mass production. This method has a problem in that it is not effective when it is desired to detect multiple temperatures.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention configures four or more electrical loads including temperature sensing elements into a bridge circuit, and connects one connection point of the bridge circuit to one side of the power supply. A connection terminal opposite to the connection point is connected to the other end of the power supply terminal via a switch means, and a comparator is provided to compare potential differences at connection points other than the connection point. .

Effect: In the above configuration, the switch means provided for switching is not included in the bridge circuit for temperature detection.
In other words, the configuration is such that the temperature detected by the switch means is not affected.

Embodiment FIG. 1 is a specific circuit diagram of a temperature detection device showing an embodiment of the present invention. In the figure, THl is a temperature sensing element, which is made of a resistor having negative temperature characteristics, and is provided to detect the temperature to be detected. This temperature sensing element TH1 constitutes a bridge circuit together with a reference resistor RK1, a reference resistor RK2 and a setting resistor R81 which are electrical loads, and the temperature sensing element TH
The connecting point B between the reference resistor RK2 and the setting resistor R81 facing this terminal is connected to the power supply Vcc to receive the DC voltage, and the connecting point B between the reference resistor RK2 and the setting resistor R81 facing this terminal receives the DC voltage through the transistor Q11 constituting the switching element. It is connected to the other terminal of the power supply, that is, GND. The comparator 11 connected its input terminals so as to detect the potential difference between terminals other than those mentioned above, that is, the connection point C between the reference resistor RK1 and the reference resistor RK2, and the connection point between the temperature sensing element TH1 and the setting resistor R81. Output the results. This output is input to the microcomputer 12, and the transistor Q11 is connected to the output terminal section.
are connected to control the switching of the Also, each resistance value is reference resistance RK1 = reference resistance RK
2, the voltage of A of the voltage between the connection black and B is B-0
The resistance of the setting resistor R51 should be between the temperature sensing element T and the resistance of the setting resistor R51.
If the temperature to be detected by H1 is Ts ℃, and the resistance value of temperature sensing element TH1 at this time is RTHl(TS)Ω, then design the setting resistance R8' ” RTHl(TS). Ambient temperature of temperature sensing element TH1 When becomes Ts°C, the voltage appearing between the contacts and B becomes the voltage A of the voltage between the contacts and B.

The operation of the embodiment of FIG. 1 constructed as described above will be described below.

When the microcomputer 12 inputs the detected temperature,
First, the output of the output terminal is set to a high voltage output. This turns on transistor Q11, and the terminal of the bridge circuit -
A voltage obtained by subtracting the voltage of the transistor Q11 from VCC is applied between the terminals B and B. Since the comparator 11 inputs the voltage obtained by dividing the voltage between A and B by the reference resistor RK2 and the reference resistor RK1 into one terminal as a reference voltage, the judgment level of the ten terminal input of the comparator 11 is the same as that of the temperature sensing element TH1. = Setting resistance R81”R
It becomes THL (TS). In other words, if the ambient temperature detected by the temperature sensing element TH1 is lower than 78°C, the temperature sensing element TH1>RTHl (TS) = setting resistance R51.
, and the voltage at the connection point C>the voltage at the connection point, so
The output of the comparator 11 outputs a lower signal when the dog is powered by ten people than when it is powered by one person. Furthermore, if the ambient temperature detected by the temperature sensing element TH1 is higher than 78°C, the temperature sensing element TH1<RT
Hl(TS) is an ax constant resistance R81, and the voltage at the connection point C is the voltage at the connection point, and since the output of the comparator 11 is smaller for one person than for ten people, it outputs a high signal. This signal is input to the microcomputer 12, and if the output of the comparator 11 is a low voltage signal, the ambient temperature of the temperature sensing element TH1 is lower than Ts °C, and if the output of the comparator 11 is a high voltage signal, the same applies. It is possible to detect that the temperature is higher than Ts'c.

In this case, the judgment level of the input voltage of the comparator 11 is the point where the ratio of the reference resistance RK1 and the reference resistance RK2 matches the ratio of the temperature sensing element TH1 and the setting resistance R81, and the temperature sensing element TH1
If the setting resistor R81 is selected so that the above ratio matches the temperature to be detected, the microcomputer 12 can obtain accurate information on the ambient temperature of the temperature sensing element TH1.

Moreover, in the temperature detection described above, the transistor Q11
It is completely unaffected by the on-state voltage. Therefore, the accuracy of the temperature that can be detected is high. Furthermore, when no temperature is input, if the output terminal is set to a low voltage by the microcomputer 12, the transistor Q11 is turned off and no current flows through the bridge circuit. Therefore, the circuit also saves energy.

FIG. 2 is a specific circuit diagram showing still another temperature detection means of the present invention.

In the figure, elements with the same symbols as those in the embodiment of FIG. 1, including temperature sensing element TH1, reference resistor RK1, reference resistor RK2, setting resistor R52, transistor Q11, and comparator 11, are the same as those in the embodiment of FIG. The same applies to the configuration and operation. The reference resistor RK3, the setting resistor R52, and the transistor Q12 correspond to the reference resistor RK2, the setting resistor RS1, and the transistor Q11, respectively, and connect to the connection point C1.
It is connected between the connection point and GND and performs the same operation.

Microcomputer 13 inputs the output of comparator 11 and the detected temperature, and controls the switching of transistors Q11 and Q12 via output terminals 1 and 2. Transistor Q11 and transistor Q12 are
The switching is controlled by the microcomputer 13, but they operate mutually exclusive and are not turned on at the same time.

The embodiment shown in FIG. 2 is intended for temperature detection at two points. The temperatures you want to detect are T2L1℃ and Ta 2℃, Ta 1℃
The resistance value of the temperature sensing element TH1 at is RTHl (Ta1
), that at T2L2°C is RTHl (Ta.).

Also, the resistance value of each setting resistor is setting resistor R51=TH
1 (Ta1), R52=TH1 (T2L2). Also, the resistance values of the reference resistors are RK1=RK2=RK
It is set to 3.

The operation of the embodiment of FIG. 2 constructed as above will be described below.

When the microcomputer 13 wants to detect the temperature of the temperature sensing element TH1 with respect to Ta1°C, the microcomputer 13 sets the output terminal 1 to high voltage operation and the output terminal 2 to low voltage operation, and turns on the transistor Q12.
is turned off, and transistor Q11 is turned on. the result,
No current flows through the collector of the transistor Q12, and the reference resistor RK3, setting resistor R82, and transistor Q12 can be ignored in terms of the circuit. That is, the circuit configuration is the same as that of the embodiment shown in FIG. 1, and the operation is also the same. The voltage divided by the setting resistor R81 and the temperature sensing element TH1 is input to the human power of the comparator 11. That is,
When the detected temperature of the temperature sensing element TH1 is lower than Ta1°C, the potential at the connection point becomes the potential at the connection point C, and the comparator 11
The output of is a low voltage output. Conversely, if the detected temperature of the temperature sensing element TH1 is higher than Ta1℃, the potential at the connection point is greater than the potential at the connection point C, and the output of the comparator 11 is a high voltage output. becomes. The output of this comparator 11 is sent to the microcomputer 1.
By inputting 3, it is possible to know whether the current detected temperature is higher or lower than Ta1°C. In addition, the output terminal 1 of the microcomputer 13 is a low voltage output, and the output terminal 2
When is a high voltage output, transistor Q11 is turned off, and no current flows through reference resistor RK2, setting resistor R81, and transistor Q11. In reality, a slight current flows between the connection point C-0, the reference resistor RK2, and the setting resistor R81, but this can be ignored. Therefore, a bridge circuit is configured by the reference resistor RK1, the reference resistor RK3, the temperature sensing element TH1, and the setting resistor R82.

In this case, the circuit configuration is the same as that described above, and the operation is also the same. However, the difference is that setting resistor R82 is different from setting resistor R81.
2=RTH1 (T2L2). In this case, comparator 1
1 and the microcomputer 12 detect Ta2°C.

That is, according to the embodiment shown in FIG. 2, it is possible to detect whether the ambient temperature of the temperature sensing element TH1 is high or low based on the temperatures at two points, 0.degree. C. and T2L2.degree.

In this example, the temperature is at two points, but the setting resistance Rs2
It is of course possible to detect even more temperatures by similarly connecting several combinations such as +reference resistor RKa and transistor Q12 between connection points C, D and GNDO.

FIG. 3 is a circuit diagram showing still another embodiment of the present invention. The circuit elements and their connections in the figure are the same as in the embodiment of FIG. 2, and corresponding numbers are the same. That is, the embodiment shown in FIG. 3 performs the same operation as that shown in FIG. 2, and a description of the operation will be omitted.

By the way, in this embodiment, the transistor Q11 and the transistor Q12 are included in the microcomputer 13. That is, the microcomputer 13
are mainly composed of semiconductor integrated circuits, and include transistors Q11. Q12 can also be included in this, leading to a reduction in the number of parts.

In addition, in the embodiment of FIG. 3, in particular, the transistor Q
11 and Q12 are manufactured together with the microcomputer 13, so their electrical characteristics are not very good. Therefore, when such a transistor is used, the conventional method shown in FIG. 4 is affected by its characteristics, making it difficult to accurately detect temperature. However, when the method of the present invention is used, it is not affected by the characteristics of the transistor, so it is possible to perform temperature detection with high accuracy.

Effects of the Invention As described above, according to the present invention, it is possible to realize a highly accurate temperature detection device that is less affected by the switch means than the conventional one.

Furthermore, since there is no need to use adjustment means such as a variable resistor to improve temperature accuracy, a simple configuration and ease of mass production are realized.

In the embodiments of the present invention, the relative positions of the reference resistor, setting resistor, and temperature sensing element of the bridge circuit may be interchanged, and the relationship of the constants is also fixed to, for example, reference resistor RK1 = reference resistor RK2. Needless to say, you can choose freely.

Furthermore, the combination of the reference resistors RK1 and RK2 does not have to be a resistance element; for example, it can be replaced with a combination of constant voltage diodes having the same voltage-current characteristics, and the reference resistor RK1 can be composed of a plurality of resistors. is also possible.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figures 2 and 3 are circuit diagrams showing one embodiment of the present invention.
The figures are circuit diagrams showing other embodiments, and FIGS. 4 to 6 are circuit diagrams showing conventional examples. RKl, RK2. RK3...Reference resistance, R51
, R82... Setting resistor, THL... Temperature sensing element, Qll, Q12... Transistor, 1
1... Comparator, 12.13... Microcomputer. Name of agent: Patent attorney Toshi Nakao and one other person × C-P!ゝMini! XY-c

Claims (1)

[Claims] Four or more electrical loads including temperature sensing elements are configured in a bridge circuit, one connection point of this bridge circuit is connected to a power supply terminal, and the connection point opposite to this connection point is connected to the power supply terminal through a switch means. A temperature sensing device connected to the other end of the terminal and comprising a comparator connected to compare potential differences at connection points other than the above connection points.