CN108507696B - Temperature measuring device - Google Patents
Temperature measuring device Download PDFInfo
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- CN108507696B CN108507696B CN201810164082.1A CN201810164082A CN108507696B CN 108507696 B CN108507696 B CN 108507696B CN 201810164082 A CN201810164082 A CN 201810164082A CN 108507696 B CN108507696 B CN 108507696B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/22—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor
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Abstract
Provided is a temperature measuring device which does not output an overvoltage even if the ambient temperature is significantly reduced. When the temperature of the negative temperature coefficient thermistor element (7) is lower than the threshold temperature, a transistor element (11) of a heating element control circuit (5) is turned on, and the positive temperature coefficient thermistor element (10) generates heat to heat the negative temperature coefficient thermistor element (7), so that the temperature of the negative temperature coefficient thermistor element (7) is increased, and the resistance value of the negative temperature coefficient thermistor element (7) is decreased, thereby preventing an overvoltage from being output from the voltage output terminal (2).
Description
Technical Field
The present invention relates to a temperature measuring device including a voltage dividing circuit for temperature measurement composed of a fixed resistance element and a negative temperature coefficient thermistor element; and more particularly, to a temperature measuring device that does not output an overvoltage even if an ambient temperature becomes lower than an assumed range, and does not have a malfunction of a subsequent stage circuit due to the overvoltage.
Background
A temperature measuring device in which a voltage dividing circuit for temperature measurement is constituted by a fixed resistance element and a negative temperature coefficient thermistor element, and an ambient temperature is measured from a voltage value at a connection point between the fixed resistance element and the negative temperature coefficient thermistor element is known as a high-precision, simple and inexpensive temperature measuring device. Such a temperature measuring device is disclosed in patent document 1 (Japanese patent laid-open No. 7-27630).
Fig. 4 shows a temperature measuring device (thermistor temperature detecting circuit) 1000 disclosed in patent document 1. Here, fig. 4 is an equivalent circuit diagram of the temperature measuring device 1000.
The temperature measuring device 1000 includes a power supply 101 that supplies a direct-current voltage, a fixed resistance element (voltage dividing resistance) 102, a thermistor element (thermistor) 103, a control circuit 104, a noise prevention filter 105, and a thermistor short circuit 106.
The power source 101 is connected to the fixed resistance element 102. Further, the fixed resistance element 102 is connected to the thermistor element 103. The thermistor element 103 is connected to a ground terminal.
The temperature-measuring voltage-dividing circuit of the temperature-measuring device 1000 is composed of a fixed resistance element 102 and a thermistor element 103. Further, a connection point 107 of the fixed resistance element 102 and the thermistor element 103 is connected to an analog input terminal 104a of the control circuit 104. In addition, in the temperature measuring device 1000, the noise prevention filter 105 is inserted between the connection point 107 and the analog input terminal 104a, but this configuration is not directly related to the present invention.
In the temperature measuring device 1000, the temperature of the thermistor element 103 changes in accordance with a change in the ambient temperature, the resistance value of the thermistor element 103 changes in accordance with a change in the temperature of the thermistor element 103, and the voltage value of the connection point 107 changes in accordance with a change in the resistance value of the thermistor element 103, and the voltage value of the connection point 107 is read via the analog input terminal 104a by a microcomputer (not shown in the figure) incorporated in the control circuit 104, and the ambient temperature is measured from the voltage value of the connection point 107.
In addition, although the temperature measuring apparatus 1000 controls the thermistor short circuit 106 by the control circuit 104 (output terminal 104b) and short-circuits the connection point 107 to the ground when the temperature is not measured, thereby preventing the electrodes of the thermistor element 103 from shifting with time without applying a voltage to the thermistor element 103, this configuration is not directly related to the present invention.
Documents of the prior art
Patent document
Patent document 1: japanese unexamined patent publication No. 7-27630
Disclosure of Invention
Technical problem to be solved by the invention
In the temperature measuring device 1000, a negative temperature coefficient thermistor element may be used as the thermistor element 103. The negative temperature coefficient thermistor element has a resistance value that decreases when the temperature increases, and increases when the temperature decreases.
The negative temperature coefficient thermistor element (thermistor element 103) has a characteristic in which the resistance value significantly increases when the temperature drops below a certain temperature. Further, when the resistance value of the negative temperature coefficient thermistor element (thermistor element 103) becomes significantly high, the voltage value of the connection point 107 becomes significantly high, and an overvoltage is applied to the analog input terminal 104a of the control circuit 104, possibly causing the control circuit 104 to malfunction.
For example, there is a case where a microcomputer built in the control circuit 104 malfunctions due to overvoltage applied to the analog input terminal 104 a.
Technical scheme for solving technical problem
The present invention has been made to solve the above problems, and a temperature measuring device of the present invention as a means thereof includes a power supply for supplying a constant voltage, a 1 st fixed resistance element, a negative temperature coefficient thermistor element as a temperature measuring element, a voltage output terminal, and a ground terminal; wherein the power supply is connected to the 1 st fixed resistive element; the 1 st fixed resistance element is connected to the NTC thermistor element; the negative temperature coefficient thermistor element is connected with the grounding terminal; the 1 st fixed resistance element and the negative temperature coefficient thermistor element are connected to the voltage output terminal; the temperature measuring voltage dividing circuit is composed of a 1 st fixed resistance element and a negative temperature coefficient thermistor element, measures the environment temperature according to the voltage value of the voltage output terminal, and comprises a switch element and a heating element which is electrified and generates heat when the switch element is switched on; the voltage output terminal is connected with the control end of the switch element; the heating element and the negative temperature coefficient thermistor element are thermally coupled.
In the temperature measuring device of the present invention, for example, the temperature of the ntc thermistor element changes in accordance with a change in the ambient temperature, the resistance value of the ntc thermistor element changes in accordance with a change in the temperature of the ntc thermistor element, and the voltage value of the voltage output terminal changes in accordance with a change in the resistance value of the ntc thermistor element; when the temperature of the NTC thermistor element is lower than a predetermined threshold temperature, the resistance value of the NTC thermistor element is higher than a predetermined resistance value, and the voltage value of the voltage output terminal is higher than a predetermined voltage value, the switching element is turned on, the heating element generates heat, and the NTC thermistor element is heated; when the temperature of the NTC thermistor element is restored to a temperature higher than the threshold temperature, the resistance value of the NTC thermistor element becomes smaller than a predetermined resistance value, and the voltage value of the voltage output terminal becomes smaller than a predetermined voltage value, the switching element is turned off, the heat generating body stops generating heat, and the heating of the NTC thermistor element is stopped.
Preferably, the device further comprises a 2 nd fixed resistance element and a 3 rd fixed resistance element; the voltage output terminal is connected to the 2 nd fixed resistance element; the 2 nd fixed resistive element is connected with the 3 rd fixed resistive element; the 3 rd fixed resistance element is connected to the ground terminal; the connection point of the 2 nd fixed resistance element and the 3 rd fixed resistance element is connected to the control terminal of the switching element. In this case, by appropriately selecting the resistance value of the 2 nd fixed resistance element and the resistance value of the 3 rd fixed resistance element, the threshold temperature of the negative temperature coefficient thermistor element that turns on or off the switching element can be easily set.
In the temperature measuring device of the present invention including the 2 nd fixed resistance element and the 3 rd fixed resistance element, for example, the temperature of the ntc thermistor element changes in accordance with a change in the ambient temperature, the resistance value of the ntc thermistor element changes in accordance with a change in the temperature of the ntc thermistor element, and the voltage value of the voltage output terminal changes in accordance with a change in the resistance value of the ntc thermistor element; when the temperature of the NTC thermistor element becomes equal to or lower than a predetermined threshold temperature, the resistance value of the NTC thermistor element becomes equal to or higher than a predetermined resistance value, the voltage value of the voltage output terminal becomes equal to or higher than a predetermined voltage value, and the voltage value of the connection point between the 2 nd fixed resistor element and the 3 rd fixed resistor element becomes equal to or higher than a predetermined voltage value, the switching element is turned on, the heating element generates heat, and the NTC thermistor element is heated; when the temperature of the NTC thermistor element is restored to a temperature higher than the threshold temperature, the resistance value of the NTC thermistor element becomes lower than a predetermined resistance value, the voltage value of the voltage output terminal becomes lower than a predetermined voltage value, and the voltage value of the connection point of the 2 nd fixed resistor element and the 3 rd fixed resistor element becomes lower than a predetermined voltage value, the switching element is turned off, the heat-generating body stops generating heat, and the heating of the NTC thermistor element is stopped.
Preferably, the switching element is connected to the ground end side of the heating element. In this case, it is possible to suppress erroneous operation of the switching element due to external noise. That is, since the ground potential is most stable in the circuit, by connecting the switching element to the ground end side instead of the heat generating element, it is possible to suppress an erroneous operation of the switching element due to external noise.
The switching element may be connected in multiple stages. That is, the number of switching elements is not limited to one, and may be plural.
For example, a transistor element or an FET (Field effect transistor) can be used as the switching element. When a transistor element is used as the switching element, the temperature measurement device can be manufactured at low cost. When an FET is used as the switching element, the switching element can be switched at high speed.
For example, a positive temperature coefficient thermistor element can be used as the heat generating element. Since the ptc thermistor device has excellent temperature-rising characteristics, when the ptc thermistor device is used as a heating device, the heating element generates heat in a short time after the switching element is turned on, and the negative temperature coefficient thermistor device can be heated. Further, since the positive temperature coefficient thermistor element suppresses the current by increasing the resistance value when an abnormality occurs, and the temperature does not continue to increase, there is no risk of smoke or fire, and therefore, when the positive temperature coefficient thermistor element is used as a heat generating body, the safety of the temperature measuring device is improved.
Effects of the invention
In the temperature measuring device of the present invention, when the ambient temperature becomes lower than the predetermined range, the temperature of the ntc thermistor element becomes equal to or lower than the predetermined threshold temperature, the resistance value of the ntc thermistor element becomes equal to or higher than the predetermined resistance value, the voltage value of the voltage output terminal becomes equal to or higher than the predetermined voltage value, and the voltage value of the connection point between the 2 nd fixed resistor element and the 3 rd fixed resistor element becomes equal to or higher than the predetermined voltage value, the switching element is turned on, the heating element generates heat, the ntc thermistor element is heated, the temperature of the ntc thermistor element is increased, the resistance value of the ntc thermistor element is decreased, and the voltage value of the voltage output terminal is not increased any more, so that no overvoltage is output, and no malfunction due to overvoltage occurs in the subsequent circuit.
Drawings
Fig. 1 is an explanatory diagram showing the configuration of a temperature measuring device 100 according to embodiment 1 (showing both an equivalent circuit diagram and a heat transfer path).
Fig. 2 is a graph showing a relationship between the temperature of the negative temperature coefficient thermistor element 7 and the resistance value in the temperature measuring device 100.
Fig. 3 is a graph showing the relationship between the temperature of the negative temperature coefficient thermistor element 7 and the voltage value of the voltage output terminal 2 in the temperature measuring device 100.
Fig. 4 is an explanatory diagram illustrating a configuration of a temperature measuring device 200 according to embodiment 2.
Fig. 5 is an explanatory diagram illustrating a configuration of a temperature measuring device 300 according to embodiment 3.
Fig. 6 is an equivalent circuit diagram showing the temperature measuring device 1000 disclosed in patent document 1.
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The embodiments are merely examples of the present invention, and the present invention is not limited to the contents of the embodiments. In addition, the contents described in the different embodiments may be combined, and the contents of implementation in this case are also included in the present invention. In addition, the drawings are provided to assist understanding of the specification, and there are cases where the drawings are drawn schematically, and there are cases where the proportion of the dimensions of the components or between the components drawn does not coincide with the proportion of the dimensions described in the specification. Note that there are cases where constituent elements described in the specification are omitted from the drawings, and where the drawings are drawn with the number of the elements omitted.
[ embodiment 1]
Fig. 1 shows a temperature measuring device 100 according to embodiment 1. Here, fig. 1 is an explanatory diagram showing both an equivalent circuit diagram of the temperature measurement device 100 and a heat transfer path.
The temperature measuring device 100 includes a power supply 1, a voltage output terminal 2, a ground terminal 3, a temperature measuring voltage dividing circuit 4, and a heating element control circuit 5.
The power supply 1 always supplies a voltage of 5V.
The temperature-measuring voltage-dividing circuit 4 includes a 1 st fixed resistance element 6 and a negative temperature coefficient thermistor element 7 connected in series with each other. The 1 st fixed resistance element 6 of the temperature-measuring voltage-dividing circuit 4 is connected to the power supply 1, and the negative temperature coefficient thermistor element 7 of the temperature-measuring voltage-dividing circuit 4 is connected to the ground terminal 3. Further, a connection point of the 1 st fixed resistance element 6 and the negative temperature coefficient thermistor element 7 of the temperature-measuring voltage-dividing circuit 4 is connected to the voltage output terminal 2.
The heating element control circuit 5 includes a 2 nd fixed resistance element 8, a 3 rd fixed resistance element 9, a positive temperature coefficient thermistor element 10 as a heating element, and an NPN-type transistor element 11 as a switching element.
The 2 nd fixed resistance element 8 is connected to the voltage output terminal 2, that is, a connection point of the 1 st fixed resistance element 6 and the negative temperature coefficient thermistor element 7 of the temperature-measuring voltage-dividing circuit 4. Further, the 2 nd fixed resistance element 8 is connected to the 3 rd fixed resistance element 9. Also, the 3 rd fixed resistance element 9 is connected to the ground terminal 3. The 2 nd fixed resistance element 8 and the 3 rd fixed resistance element 9 connected in series constitute a voltage dividing circuit for controlling the transistor element 11.
A positive temperature coefficient thermistor element 10 as a heat generating body is connected to the power supply 1. Here, the type of the heat generating element is arbitrary, and is not limited to the positive temperature coefficient thermistor element, and may be, for example, a heater element, a fixed resistance element (chip resistor), a nichrome wire, or the like. In the present embodiment, the ptc thermistor element 10 is connected to the power supply 1 as the power supply of the temperature-measuring voltage-dividing circuit 4, but instead, the ptc thermistor element 10 may be connected to a power supply different from the power supply 1.
A positive temperature coefficient thermistor element 10 as a heat generating body is thermally coupled to the negative temperature coefficient thermistor element 7. That is, the positive temperature coefficient thermistor element 10 and the negative temperature coefficient thermistor element 7 are configured such that the temperature of the negative temperature coefficient thermistor element 7 rises due to heat generation of the positive temperature coefficient thermistor element 10.
The transistor element 11 includes a collector C, an emitter E, and a base B. The transistor element 11 is turned on when a voltage value of 0.6V or more is applied to the base B, and is turned off when a voltage value of less than 0.6V is applied thereto. The base B becomes the control terminal.
The positive temperature coefficient thermistor element 10 is connected to the collector C of the transistor element 11. Further, a connection point of the 2 nd fixed resistance element 8 and the 3 rd fixed resistance element 9 is connected to the base B of the transistor element 11. The emitter E of the transistor element 11 is connected to the ground terminal 3.
Table 1 shows the respective resistance values of the 1 st fixed resistance element 6, the negative temperature coefficient thermistor element 7, the 2 nd fixed resistance element 8, the 3 rd fixed resistance element 9, and the positive temperature coefficient thermistor element 10. Fig. 2 shows the relationship between the temperature of the negative temperature coefficient thermistor element 7 and the resistance value.
[ Table 1]
| Resistance value | |
| 1 st fixed |
10kΩ |
| Negative temperature coefficient thermistor element 7 | 10kΩ(25℃) |
| No. 2 fixed |
5.1MΩ |
| No. 3 fixed |
1MΩ |
| Positive temperature |
68Ω(25℃) |
As shown in fig. 2, the negative temperature coefficient thermistor element 7 changes in resistance value when its own temperature changes corresponding to the ambient temperature. Specifically, the resistance value decreases when the temperature increases, and increases when the temperature decreases.
The voltage value at the voltage output terminal 2, that is, the voltage value at the connection point between the 1 st fixed resistance element 6 and the ntc thermistor element 7 of the voltage divider circuit 4 for temperature measurement varies depending on the resistance value of the ntc thermistor element 7. Specifically, when the resistance value of the ntc thermistor element 7 decreases, the voltage value of the voltage output terminal 2 decreases, and when the resistance value of the ntc thermistor element 7 increases, the voltage value of the voltage output terminal 2 increases.
The temperature measuring apparatus 100 reads the voltage value of the voltage output terminal 2 by, for example, a microcomputer (not shown in the figure) or the like to measure the ambient temperature.
As described above, the resistance value of the negative temperature coefficient thermistor element 7 increases when the temperature decreases. When the temperature of the ntc thermistor element 7 drops below a predetermined temperature and the resistance value of the ntc thermistor element 7 rises above a predetermined resistance value, the voltage value of the voltage output terminal 2 rises above an assumed voltage value, which may cause an overvoltage, and a subsequent circuit (such as a microcomputer) connected to the voltage output terminal 2 may be damaged.
Therefore, when the temperature of the negative temperature coefficient thermistor element 7 falls below the predetermined threshold temperature, the temperature measuring apparatus 100 turns on the transistor element 11 to energize the positive temperature coefficient thermistor element 10, thereby causing the positive temperature coefficient thermistor element 10 to generate heat to heat the negative temperature coefficient thermistor element 7. More specifically, the temperature of the ntc thermistor element 7 falls below a predetermined threshold temperature, the resistance value of the ntc thermistor element 7 rises above a predetermined resistance value, the voltage value of the voltage output terminal 2 rises above a predetermined voltage value, and the voltage value of the connection point of the 2 nd fixed resistor element and the 3 rd fixed resistor element rises above a predetermined voltage value, whereby the transistor element 11 is turned on, and the ptc thermistor element 10 generates heat to heat the ntc thermistor element 7.
Specifically, for example, when the threshold temperature of the negative temperature coefficient thermistor element 7 is set to 0 ℃, and the temperature of the negative temperature coefficient thermistor element 7 drops to 0 ℃ or lower, the resistance value of the negative temperature coefficient thermistor element 7 increases to 27k Ω or higher, the voltage value of the voltage output terminal 2 increases to 3.65V or higher, and the voltage value of the connection point between the 2 nd fixed resistor element and the 3 rd fixed resistor element increases to 0.6V or higher, whereby the transistor element 11 is turned on, and the positive temperature coefficient thermistor element 10 generates heat to heat the negative temperature coefficient thermistor element 7. As a result, the temperature of the ntc thermistor element 7 is restored to a temperature higher than 0 ℃, and the resistance value of the ntc thermistor element 7 is decreased to 27k Ω or less, whereby the voltage value of the voltage output terminal 2 is decreased, and overvoltage applied from the voltage output terminal 2 to a subsequent circuit is prevented.
The temperature measuring apparatus 100 sets the vicinity of the set threshold temperature as the lower limit of the measurable temperature range. The temperature measurement device 100 cannot measure an ambient temperature below a threshold temperature. A relationship between the temperature of the negative temperature coefficient thermistor element 7 (ambient temperature) and the voltage value of the voltage output terminal 2 when the threshold temperature is set to 0 ℃.
In the above description, although the case where the threshold temperature is set to 0 ℃ has been described, the threshold temperature can be freely set by changing at least one of the resistance value of the 2 nd fixed resistance element 8 and the resistance value of the 3 rd fixed resistance element 9. The threshold temperature may be set to 0 ℃ or lower, or 0 ℃ or higher.
In the temperature measuring device 100, when the temperature (ambient temperature) of the negative temperature coefficient thermistor element 7 falls below the threshold temperature, the positive temperature coefficient thermistor element 10 generates heat to heat the negative temperature coefficient thermistor element 7, so that the resistance value of the negative temperature coefficient thermistor element 7 falls, overvoltage does not occur from the voltage output terminal 2, and a subsequent circuit does not malfunction due to overvoltage.
In addition, in the temperature measuring apparatus 100, since the transistor element 11 is connected to the ground side of the positive temperature coefficient thermistor element 10 as a heat generating body, it is possible to suppress an erroneous operation of the transistor element 11 due to external noise. That is, since the potential of the ground terminal is most stable in the circuit, the temperature measuring device 100 in which the transistor element 11 is connected to the ground terminal 3 side of the ptc thermistor element 10 can suppress the malfunction of the transistor element 11 caused by external noise.
[ 2 nd embodiment ]
Fig. 4 shows a temperature measuring device 200 according to embodiment 2. Fig. 4 is an explanatory diagram showing both an equivalent circuit diagram of the temperature measuring device 200 and a heat transfer path.
The temperature measurement device 200 according to embodiment 2 is a modification of the temperature measurement device 100 according to embodiment 1. Specifically, the temperature measuring device 200 omits the 2 nd fixed resistance element 8 and the 3 rd fixed resistance element 9 from the temperature measuring device 100. The temperature measuring device 200 changes the resistance value of the 1 st fixed resistive element 6 from 10k Ω of the temperature measuring device 100 to 1.8k Ω. The temperature measuring device 200 changes the resistance value (the resistance value at 25 ℃) of the negative temperature coefficient thermistor element 7 from 10k Ω of the temperature measuring device 100 to 0.15k Ω. The temperature measuring device 200 will be briefly described below.
The temperature measuring device 200 includes a power supply 1, a voltage output terminal 2, a ground terminal 3, a temperature measuring voltage dividing circuit 4, and a heating element control circuit 5. The power supply 1 always supplies a voltage of 5V.
The temperature-measuring voltage-dividing circuit 4 includes a 1 st fixed resistance element 6 and a negative temperature coefficient thermistor element 7 connected in series with each other. The 1 st fixed resistance element 6 of the temperature-measuring voltage-dividing circuit 4 is connected to the power supply 1, and the negative temperature coefficient thermistor element 7 of the temperature-measuring voltage-dividing circuit 4 is connected to the ground terminal 3. Further, a connection point of the 1 st fixed resistance element 6 and the negative temperature coefficient thermistor element 7 of the temperature-measuring voltage-dividing circuit 4 is connected to the voltage output terminal 2.
The heating element control circuit 5 includes a positive temperature coefficient thermistor element 10 as a heating element and an NPN transistor element 11 as a switching element.
A positive temperature coefficient thermistor element 10 as a heat generating body is thermally coupled to the negative temperature coefficient thermistor element 7. That is, the positive temperature coefficient thermistor element 10 and the negative temperature coefficient thermistor element 7 are configured such that the temperature of the negative temperature coefficient thermistor element 7 rises due to heat generation of the positive temperature coefficient thermistor element 10.
The transistor element 11 includes a collector C, an emitter E, and a base B. The transistor element 11 is turned on when a voltage value of 0.6V or more is applied to the base B, and is turned off when a voltage value of less than 0.6V is applied thereto.
A positive temperature coefficient thermistor element 10 as a heat generating body is connected between the power supply 1 and the collector C of the transistor element 11. Further, the voltage output terminal 2 (a connection point of the 1 st fixed resistance element 6 and the negative temperature coefficient thermistor element 7 of the temperature-measuring voltage-dividing circuit 4) is connected to the base B of the transistor element 11. The emitter E of the transistor element 11 is connected to the ground terminal 3.
Table 2 shows the resistance values of the 1 st fixed resistance element 6, the negative temperature coefficient thermistor element 7, and the positive temperature coefficient thermistor element 10, respectively.
[ Table 2]
| Resistance value | |
| 1 st fixed |
1.8kΩ |
| Negative temperature coefficient thermistor element 7 | 0.15kΩ(25℃) |
| Positive temperature |
68Ω(25℃) |
The voltage value of the voltage output terminal 2, that is, the voltage value of the connection point between the 1 st fixed resistance element 6 and the ntc thermistor element 7 of the temperature-measuring voltage-dividing circuit 4 changes in accordance with the resistance value of the ntc thermistor element 7. Specifically, when the resistance value of the ntc thermistor element 7 decreases, the voltage value of the voltage output terminal 2 decreases, and when the resistance value of the ntc thermistor element 7 increases, the voltage value of the voltage output terminal 2 increases.
The temperature measuring device 200 reads the voltage value of the voltage output terminal 2 by, for example, a microcomputer (not shown in the figure) or the like to measure the ambient temperature.
In the temperature measuring device 200, when the temperature of the negative temperature coefficient thermistor element 7 drops to or below a predetermined threshold temperature, the resistance value of the negative temperature coefficient thermistor element 7 rises to or above a predetermined resistance value, and the voltage value of the voltage output terminal 2 rises to or above a predetermined voltage value, the transistor element 11 is turned on, and the positive temperature coefficient thermistor element 10 generates heat to heat the negative temperature coefficient thermistor element 7.
Specifically, for example, when the threshold temperature of the negative temperature coefficient thermistor element 7 is set to 0 ℃, and the temperature of the negative temperature coefficient thermistor element 7 drops to 0 ℃ or lower, the resistance value of the negative temperature coefficient thermistor element 7 increases to 0.4k Ω or higher, and the voltage value of the voltage output terminal 2 increases to 0.6V or higher, so that the transistor element 11 is turned on, and the positive temperature coefficient thermistor element 10 generates heat to heat the negative temperature coefficient thermistor element 7. As a result, the temperature of the ntc thermistor element 7 is restored to a temperature higher than 0 ℃, and the resistance value of the ntc thermistor element 7 is decreased to 0.4k Ω or less, so that the voltage value of the voltage output terminal 2 is decreased, thereby preventing an overvoltage from being applied from the voltage output terminal 2 to a subsequent circuit.
[ embodiment 3 ]
Fig. 5 shows a temperature measuring device 300 according to embodiment 3. Here, fig. 5 is an explanatory diagram showing both an equivalent circuit diagram of the temperature measuring device 300 and a heat transfer path.
The temperature measurement device 300 according to embodiment 3 is a modification of the temperature measurement device 100 according to embodiment 1. Specifically, the temperature measurement device 100 includes one transistor element 11 as a switching element, but the temperature measurement device 300 includes two darlington-connected transistor elements 31 and 32 instead.
Specifically, in the temperature measuring device 300, the connection point of the 2 nd fixed resistance element 8 and the 3 rd fixed resistance element 9 is connected to the base B of the transistor element 31. The collector C of the transistor element 31 is connected to the positive temperature coefficient thermistor element 10. The emitter E of the transistor element 31 is connected to the base B of the transistor element 32.
Further, the collector C of the transistor element 32 is also connected to the positive temperature coefficient thermistor element 10. The emitter E of the transistor element 32 is connected to the ground terminal 3.
In the temperature measuring device 300, when the temperature of the ntc thermistor element 7 drops to or below the predetermined threshold temperature, the resistance value of the ntc thermistor element 7 rises to or above the predetermined resistance value, and the voltage value of the voltage output terminal 2 (the connection point between the 1 st fixed resistor element 6 and the ntc thermistor element 7) rises to or above the predetermined voltage value, the transistor element 31 is first turned on, and then the transistor element 32 is turned on, so that the ptc thermistor element 10 generates heat to heat the ntc thermistor element 7.
In the temperature measuring device 300, when the temperature of the ntc thermistor element 7 returns to the threshold temperature or higher and the resistance value of the ntc thermistor element 7 decreases to a predetermined resistance value or lower, the voltage value of the voltage output terminal 2 (the connection point between the 1 st fixed resistor element 6 and the ntc thermistor element 7) decreases, thereby preventing an overvoltage from being applied from the voltage output terminal 2 to the subsequent circuit. In the temperature measuring device 300, when the voltage value of the voltage output terminal 2 drops to or below a predetermined voltage value, the transistor element 31 is turned off first, and then the transistor element 32 is turned off, so that the heat generation of the ptc thermistor element 10 is stopped.
As described above, the number of switching elements (e.g., transistor elements) is not limited to one, and may be plural.
The temperature measuring devices 100, 200, and 300 according to the embodiments have been described above. However, the present invention is not limited to the above, and various modifications can be made in accordance with the spirit of the present invention.
For example, the transistor element 11 is used as the switching element in the temperature measuring device 100, but the type of the switching element is arbitrary, and may be, for example, an FET or the like. When a FET is used, for example, the positive temperature coefficient thermistor element 10 is connected to the drain of the FET. Further, a connection point of the 2 nd fixed resistance element 8 and the 3 rd fixed resistance element 9 is connected to the gate of the FET. Further, the source of the FET is connected to the ground terminal 3. At this time, the gate becomes a control terminal.
In addition, the positive temperature coefficient thermistor element 10 is used as a heat generating element in the temperature measuring device 100, but the type of the heat generating element may be arbitrary, and for example, a heater element, a fixed resistance element, or the like may be used.
In the temperature measuring device 100, the same power supply 1 as that of the temperature measuring voltage dividing circuit 4 is used as the power supply of the heating element control circuit 5, but the power supply of the heating element control circuit 5 may be separately provided without this.
As described above, the resistance values of the 1 st fixed resistance element 6, the negative temperature coefficient thermistor element 7, the 2 nd fixed resistance element 8, the 3 rd fixed resistance element 9, and the positive temperature coefficient thermistor element 10 are not limited to the above values and can be freely changed. In particular, if the resistance values of the 2 nd fixed resistance element 8 and the 3 rd fixed resistance element 9 are changed, the threshold temperature at which the transistor element 11 is turned on to cause the ptc thermistor element 10 to start generating heat can be changed.
Description of the reference symbols
1. power supply
2. voltage output terminal
3. grounding terminal
4-temperature measuring voltage dividing circuit
5. heating element control circuit
6. 1 st fixed resistance element
7. negative temperature coefficient thermistor element
8. 2 nd fixed resistance element
9. 3 rd fixed resistance element
10. positive temperature coefficient thermistor element (heating element)
11. 31, 32. transistor element (switching element)
Claims (8)
1. A temperature measuring device is characterized in that,
comprises a power supply for supplying a constant voltage, a 1 st fixed resistance element, a negative temperature coefficient thermistor element as a temperature measuring element, a voltage output terminal, and a ground terminal,
the power supply is connected to the 1 st fixed resistive element;
the 1 st fixed resistance element is connected to the NTC thermistor element;
the negative temperature coefficient thermistor element is connected to the ground terminal;
a connection point of the 1 st fixed resistance element and the ntc thermistor element is connected to the voltage output terminal;
the temperature measuring voltage dividing circuit is composed of the 1 st fixed resistance element and the negative temperature coefficient thermistor element;
measuring an ambient temperature from a voltage value of the voltage output terminal,
further comprises a switching element and a heating element which is energized to generate heat when the switching element is turned on,
the voltage output terminal is connected to a control terminal of the switching element;
the heating body and the negative temperature coefficient thermistor element are thermally coupled.
2. Temperature measuring device according to claim 1,
a temperature of the NTC thermistor element changes in accordance with a change in ambient temperature, a resistance value of the NTC thermistor element changes in accordance with a change in temperature of the NTC thermistor element, and a voltage value of the voltage output terminal changes in accordance with a change in resistance value of the NTC thermistor element;
when the temperature of the ntc thermistor element becomes equal to or lower than a predetermined threshold temperature, the resistance value of the ntc thermistor element becomes equal to or higher than a predetermined resistance value, and the voltage value of the voltage output terminal becomes equal to or higher than a predetermined voltage value, the switching element is turned on, the heating element generates heat, and the ntc thermistor element is heated;
when the temperature of the ntc thermistor element is restored to a temperature higher than the threshold temperature, the resistance value of the ntc thermistor element becomes lower than a predetermined resistance value, and the voltage value of the voltage output terminal becomes lower than a predetermined voltage value, the switching element is turned off, the heat-generating body stops generating heat, and heating of the ntc thermistor element is stopped.
3. Temperature measuring device according to claim 1,
further comprising a 2 nd fixed resistive element and a 3 rd fixed resistive element;
the voltage output terminal is connected to a 2 nd fixed resistance element;
the 2 nd fixed resistive element is connected with the 3 rd fixed resistive element;
the 3 rd fixed resistance element is connected to the ground terminal;
a connection point of the 2 nd fixed resistance element and the 3 rd fixed resistance element is connected to a control terminal of the switching element.
4. Temperature measuring device according to claim 3,
a temperature of the NTC thermistor element changes in accordance with a change in ambient temperature, a resistance value of the NTC thermistor element changes in accordance with a change in temperature of the NTC thermistor element, and a voltage value of the voltage output terminal changes in accordance with a change in resistance value of the NTC thermistor element;
when the temperature of the ntc thermistor element becomes equal to or lower than a predetermined threshold temperature, the resistance value of the ntc thermistor element becomes equal to or higher than a predetermined resistance value, the voltage value of the voltage output terminal becomes equal to or higher than a predetermined voltage value, and the voltage value of the connection point between the 2 nd fixed resistor element and the 3 rd fixed resistor element becomes equal to or higher than a predetermined voltage value, the switching element is turned on, the heating element generates heat, and the ntc thermistor element is heated;
when the temperature of the ntc thermistor element is restored to a temperature higher than the threshold temperature, the resistance value of the ntc thermistor element becomes lower than a predetermined resistance value, the voltage value of the voltage output terminal becomes lower than a predetermined voltage value, and the voltage value of the connection point between the 2 nd fixed resistor element and the 3 rd fixed resistor element becomes lower than a predetermined voltage value, the switching element is turned off, the heat-generating body stops generating heat, and the heating of the ntc thermistor element is stopped.
5. Temperature measuring device according to any of claims 1 to 4,
the switching element is a transistor element or an FET.
6. Temperature measuring device according to any of claims 1 to 4,
the switching element is connected to the ground end side of the heat generating body.
7. Temperature measuring device according to any of claims 1 to 4,
the switching element is connected with a plurality of stages.
8. Temperature measuring device according to any of claims 1 to 4,
the heating element is a positive temperature coefficient thermistor element.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2017035939 | 2017-02-28 | ||
| JP2017-035939 | 2017-02-28 | ||
| JP2018016834A JP6733686B2 (en) | 2017-02-28 | 2018-02-01 | Temperature measuring device |
| JP2018-016834 | 2018-02-01 |
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| Publication Number | Publication Date |
|---|---|
| CN108507696A CN108507696A (en) | 2018-09-07 |
| CN108507696B true CN108507696B (en) | 2020-08-14 |
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| CN201810164082.1A Active CN108507696B (en) | 2017-02-28 | 2018-02-27 | Temperature measuring device |
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Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0727630A (en) * | 1993-07-09 | 1995-01-31 | Fujitsu General Ltd | Thermistor temperature detecting circuit |
| CN101917039B (en) * | 2010-08-05 | 2014-04-16 | 惠州Tcl移动通信有限公司 | Battery and method and circuit for preventing overhigh temperature during charging same |
| CN204511732U (en) * | 2015-01-29 | 2015-07-29 | 中国电子科技集团公司第十三研究所 | A kind of fuel filter electrical heating controller |
| CN205584024U (en) * | 2016-02-01 | 2016-09-14 | 广州视源电子科技股份有限公司 | Take switching power supply circuit of excess temperature protection |
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