Temperature detection circuit

Abstract

The utility model discloses a temperature detection circuit which comprises a power supply voltage, a reference voltage source, an output voltage, a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a first resistor R1 to an eighth resistor R8 and a triode Q1, the non-inverting input end of the U1 is connected with the reference voltage source, the inverting input end of the U1 is grounded through R3, the output end of the U1 is connected with the base electrode of the Q1 through R1, and the output end of the U1 is connected with the base electrode of the triode Q1 through R3. A collector electrode of the Q1 is connected with a power supply voltage, an emitter electrode is connected with a reverse input end of the U1 through an R2, an emitter electrode is connected with a reverse input end of the U2 through an R4, a non-inverting input end of the U2 is grounded, an output end of the U2 is connected with a reverse input end of the U2 through an R6, an emitter electrode is connected with a reverse input end of the U3 through an R5, the output end of the U2 is connected with the reverse input end of the U3 through an R7, and the reverse input end of the U3 is connected with the output end of the U3 through an R8. The non-inverting input end of the U3 is grounded, and the output end of the U3 is connected with output voltage; the R6 is a thermistor, the output voltage and the resistance change of the R6 are in a linear relation, and temperature measurement is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of temperature detection, and particularly to a temperature detection circuit. Background Art

[0002] During the operation of an electric vehicle, some power devices will have relatively serious heat generation due to the flow of large currents, posing a risk of device burnout and thus affecting driving safety. Therefore, it is necessary to detect the temperature of these devices and provide protection when necessary. For temperature detection, an NTC (Negative Temperature Coefficient) thermistor is generally used to sample the temperature. Its resistance value decreases as the temperature rises, and the corresponding temperature value is determined by detecting the resistance value of the NTC.

[0003] In the currently commonly used temperature detection circuit, the thermistor RT is connected in series with the resistor R to form a voltage division circuit, which is powered by VCC (Volt Current Condenser). When the resistance value of RT changes with temperature, the output voltage Vo across RT changes accordingly. By sampling the voltage value Vo, the real-time resistance value of RT can be calculated, and then the real-time temperature of the device under test can be deduced. However, in this measurement method, VCC may fluctuate, affecting the accuracy of the detection result.

[0004] Therefore, it is urgent to study a temperature detection circuit to reduce the influence of the power supply voltage fluctuation on the temperature measurement of the thermistor and improve the measurement accuracy. Summary of the Utility Model

[0005] This specification provides a temperature detection circuit to overcome at least one technical problem existing in the related art.

[0006] According to an embodiment of this specification, a temperature detection circuit is provided, including a power supply voltage, a reference voltage source, an output voltage, a first operational amplifier, a second operational amplifier, a third operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, and a triode, wherein

[0007] One end of the reference voltage source is connected to the supply voltage, and the other end is grounded. The non-inverting input terminal of the first operational amplifier is connected to the reference voltage source. The inverting input terminal of the first operational amplifier is grounded through the third resistor. The output terminal of the first operational amplifier is connected to one end of the first resistor. The other end of the first resistor is connected to the base of the triode. The collector of the triode is connected to the supply voltage. The emitter of the triode is connected to one end of the second resistor. The other end of the second resistor is connected to the inverting input terminal of the first operational amplifier. One end of the fourth resistor is connected to the emitter of the triode. The other end of the fourth resistor is connected to the inverting input terminal of the second operational amplifier. The non-inverting input terminal of the second operational amplifier is grounded. The output terminal of the second operational amplifier is connected to one end of the sixth resistor. The other end of the sixth resistor is connected to the inverting input terminal of the second operational amplifier. One end of the fifth resistor is connected to the emitter of the triode. The other end of the fifth resistor is connected to the inverting input terminal of the third operational amplifier. One end of the seventh resistor is connected to the output terminal of the second operational amplifier. The other end of the seventh resistor is connected to the inverting input terminal of the third operational amplifier. One end of the eighth resistor is connected to the inverting input terminal of the third operational amplifier. The other end of the eighth resistor is connected to the output terminal of the third operational amplifier. The non-inverting input terminal of the third operational amplifier is grounded. The output terminal of the third operational amplifier is connected to the output voltage;

[0008] The resistance value of the fourth resistor is equal to that of the fifth resistor. The sixth resistor is a thermistor. The resistance value of the seventh resistor is the resistance value of the sixth resistor at 0 °C. The output voltage has a linear relationship with the change in the resistance value of the sixth resistor, realizing temperature measurement.

[0009] Optionally, the reference voltage source model is REF192, and the output is +2.5V, that is

[0010] V REF =V C =+2.5V,

[0011] where, V REF is the voltage value of the reference voltage source, and V C is the supply voltage value.

[0012] Optionally, the emitter of the triode is point A, and the output terminal of the second operational amplifier is point B. According to the circuit structure, there is:

[0013] V A / R4 + V B / (R + ΔR) = 0, that is V B = -R(1 + δ)V A / R4,

[0014] where, R + ΔR is the resistance value of the thermistor R6, R is the resistance value of the thermistor at 0 °C, ΔR is the resistance change caused by temperature, and δ = ΔR / R; R4 is the resistance value of the fourth resistor, and V A is the voltage at point A, VB is the voltage at point B;

[0015] Also, there is: V A / R5 + V B / R + V O / R8 = 0, and R4 = R5, where R5 is the resistance value of the fifth resistor and R8 is the resistance value of the eighth resistor, and V O is the output voltage;

[0016] Then there is V O = R8 × V A ×δ / R4, then the output voltage V O has a linear relationship with the change in the resistance value of the thermistor and the sixth resistor. According to the output voltage V O the resistance value of the thermistor can be obtained, and then the measured temperature can be obtained.

[0017] The beneficial effects of the embodiments of this specification are as follows:

[0018] The embodiments of this specification provide a temperature detection circuit, including a power supply voltage, a reference voltage source, an output voltage, a first operational amplifier, a second operational amplifier, a third operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, and a triode. Through the circuit structure formed by the combined connection of the operational amplifier and the triode in this example, the power supply voltage is subjected to a voltage stabilization conversion, and based on the stable voltage, the resistance value of the thermistor is detected to obtain the required temperature value. It has high measurement accuracy, stable performance, simple debugging, low requirements for devices, and strong practicability.

[0019] The innovation points of the embodiments of this specification include:

[0020] 1. In this specification, through the circuit structure formed by the combined connection of three operational amplifiers, eight resistors, and a triode, the power supply voltage is subjected to a voltage stabilization conversion, and based on the stable voltage, the resistance value of the thermistor is detected to obtain the required temperature value, which is one of the innovation points of the embodiments of this specification.

[0021] 2. In this specification, the system has high measurement accuracy, stable performance, simple debugging, low requirements for devices, and strong practicability, which is one of the innovation points of the embodiments of this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of this specification or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 A structural schematic diagram of a temperature detection circuit provided in an embodiment of this specification. Specific implementation manners

[0024] Next, the technical solutions in the embodiments of this specification will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of this specification. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] It should be noted that the terms "including" and "having" and any variations thereof in the embodiments of this specification are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0026] An embodiment of this specification discloses a temperature detection circuit, which will be described in detail below.

[0027] Figure 1 A structural schematic diagram of a temperature detection circuit provided in an embodiment of this specification. As Figure 1 shown, a temperature detection circuit includes a supply voltage VCC, a reference voltage source REF, an output voltage VO, a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a triode Q1, where

[0028] One end of the reference voltage source REF is connected to the supply voltage VCC, and the other end is grounded. The non-inverting input terminal of the first operational amplifier U1 is connected to the reference voltage source REF. The inverting input terminal of the first operational amplifier U1 is grounded through the third resistor R3. The output terminal of the first operational amplifier U1 is connected to one end of the first resistor R1. The other end of the first resistor R1 is connected to the base of the triode Q1. The collector of the triode Q1 is connected to the supply voltage VCC. The emitter of the triode Q1 is connected to one end of the second resistor R2. The other end of the second resistor R2 is connected to the inverting input terminal of the first operational amplifier U1. One end of the fourth resistor R4 is connected to the emitter of the triode Q1. The other end of the fourth resistor R4 is connected to the inverting input terminal of the second operational amplifier U2. The non-inverting input terminal of the second operational amplifier U2 is grounded. The output terminal of the second operational amplifier U2 is connected to one end of the sixth resistor R6. The other end of the sixth resistor R6 is connected to the inverting input terminal of the second operational amplifier U2. One end of the fifth resistor R5 is connected to the emitter of the triode Q1. The other end of the fifth resistor R5 is connected to the inverting input terminal of the third operational amplifier U3. One end of the seventh resistor R7 is connected to the output terminal of the second operational amplifier U2. The other end of the seventh resistor R7 is connected to the inverting input terminal of the third operational amplifier U3. One end of the eighth resistor R8 is connected to the inverting input terminal of the third operational amplifier U3. The other end of the eighth resistor R8 is connected to the output terminal of the third operational amplifier U3. The non-inverting input terminal of the third operational amplifier U3 is grounded. The output terminal of the third operational amplifier U3 is connected to the output voltage VO.

[0029] The resistance value of the fourth resistor R4 is equal to that of the fifth resistor R5. The sixth resistor R6 is a thermistor. The resistance value of the seventh resistor R7 is the resistance value of the sixth resistor R6 at 0°C. The output voltage VO has a linear relationship with the change in the resistance value of the sixth resistor R6, realizing temperature measurement.

[0030] In specific implementation, the model of the reference voltage source is REF192, and the output is +2.5V, that is

[0031] V REF =V C =+2.5V,

[0032] wherein, V REF is the voltage value of the reference voltage source, and V C is the supply voltage value.

[0033] In Figure 1 the emitter of the triode is point A, and the output terminal of the second operational amplifier is point B. According to the circuit structure, there is:

[0034] V A / R4 + V B / (R + ΔR) = 0, that is V B =-R(1 + δ)V A / R4,

[0035] wherein, R + ΔR is the resistance value of the thermistor R6, R is the resistance value of the thermistor at 0 °C, ΔR is the resistance change caused by temperature, and δ = ΔR / R; R4 is the resistance value of the fourth resistor, V A is the voltage at point A, and V B is the voltage at point B;

[0036] Also, there is: V A / R5 + V B / R + V O / R8 = 0, and R4 = R5, where R5 is the resistance value of the fifth resistor and R8 is the resistance value of the eighth resistor, and V O is the output voltage;

[0037] Then there is V O = R8 × V A × δ / R4, so the output voltage V O has a linear relationship with the resistance change of the thermistor sixth resistor. According to the output voltage V O the resistance value of the thermistor can be obtained, and then the measured temperature can be obtained.

[0038] In summary, the embodiments of this specification provide a temperature detection circuit. Through an operational amplifier, resistors, and a triode, the supply voltage is subjected to a voltage stabilization conversion, and based on the stable voltage, the resistance value of the thermistor is detected to obtain the required temperature value. It has high measurement accuracy, stable performance, simple debugging, low requirements for devices, and strong practicability.

[0039] Those of ordinary skill in the art can understand that the drawings are only schematic diagrams of an embodiment, and the modules or processes in the drawings are not necessarily essential for implementing the present invention.

[0040] Those of ordinary skill in the art can understand that the modules in the device in the embodiment can be distributed in the device in the embodiment according to the description of the embodiment, or can be correspondingly changed to be located in one or more devices different from this embodiment. The modules of the above embodiments can be combined into one module, or can be further split into multiple sub-modules.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A temperature detection circuit, characterized in that, It includes a supply voltage, a reference voltage source, an output voltage, a first operational amplifier, a second operational amplifier, a third operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, and a triode, where One end of the reference voltage source is connected to the supply voltage and the other end is grounded. The non-inverting input terminal of the first operational amplifier is connected to the reference voltage source. The inverting input terminal of the first operational amplifier is grounded through the third resistor. The output terminal of the first operational amplifier is connected to one end of the first resistor. The other end of the first resistor is connected to the base of the triode. The collector of the triode is connected to the supply voltage. The emitter of the triode is connected to one end of the second resistor. The other end of the second resistor is connected to the inverting input terminal of the first operational amplifier. One end of the fourth resistor is connected to the emitter of the triode. The other end of the fourth resistor is connected to the inverting input terminal of the second operational amplifier. The non-inverting input terminal of the second operational amplifier is grounded. The output terminal of the second operational amplifier is connected to one end of the sixth resistor. The other end of the sixth resistor is connected to the inverting input terminal of the second operational amplifier. One end of the fifth resistor is connected to the emitter of the triode. The other end of the fifth resistor is connected to the inverting input terminal of the third operational amplifier. One end of the seventh resistor is connected to the output terminal of the second operational amplifier. The other end of the seventh resistor is connected to the inverting input terminal of the third operational amplifier. One end of the eighth resistor is connected to the inverting input terminal of the third operational amplifier. The other end of the eighth resistor is connected to the output terminal of the third operational amplifier. The non-inverting input terminal of the third operational amplifier is grounded. The output terminal of the third operational amplifier is connected to the output voltage; The resistance value of the fourth resistor is equal to that of the fifth resistor. The sixth resistor is a thermistor. The resistance value of the seventh resistor is the resistance value of the sixth resistor at 0 °C. The output voltage has a linear relationship with the change in the resistance value of the sixth resistor to achieve temperature measurement.

2. The circuit according to claim 1, wherein The model of the reference voltage source is REF192, and the output is +2.5V, that is V REF = V C = +2.5V, Among them, V REF is the reference voltage source voltage value, and V C is the supply voltage value.

3. The circuit according to claim 1, characterized in that, The emitter of the triode is point A, and the output terminal of the second operational amplifier is point B. According to the circuit structure, there is: V A / R4 + V B / (R + ΔR) = 0, that is, V B = -R(1 + δ)V A / R4, Among them, \(R + \Delta R\) is the resistance value of the thermistor \(R6\), \(R\) is the resistance value of the thermistor at \(0^{\circ}C\), \(\Delta R\) is the resistance value change caused by temperature, \(\delta=\Delta R / R\); \(R4\) is the resistance value of the fourth resistor, \(V\) A is the voltage at point \(A\), \(V\) B is the voltage at point \(B\); Also: V A / R5 + V B / R + V O / R8 = 0, and R4 = R5, where R5 is the resistance value of the fifth resistor, R8 is the resistance value of the eighth resistor, V O is the output voltage; Then there is V O = R8 × V A × δ / R4, then the output voltage V O has a linear relationship with the resistance change of the thermistor's sixth resistor. According to the output voltage V O the resistance value of the thermistor can be obtained, and then the measured temperature can be obtained.

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