NTC temperature detection circuit

Abstract

The application relates to an NTC temperature detection circuit, which comprises a voltage division unit, an NTC resistor, a conduction unit, a main control unit and an analog-digital conversion port. The main control unit is provided with a signal port for controlling the sampling mode of the circuit. The voltage division unit is connected between a power supply and the analog-digital conversion port and forms a voltage division path with the NTC resistor and the conduction unit; the conduction unit is grounded and is controlled by the main control unit to be turned on or turned off. The main control unit pre-sets a sampling mode and a voltage threshold value, initially samples a first voltage of the NTC resistor in a forward sampling mode, and judges whether to switch to a reverse sampling mode based on the comparison result of the voltage and the threshold value. The main control unit controls the output level of the signal port according to the result, realizes the switching of the circuit structure, samples a second voltage of the NTC resistor to calculate the temperature, and realizes the temperature detection in a wide temperature range.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of temperature detection, and in particular to an NTC temperature detection circuit. BACKGROUND

[0002] NTC (Negative Temperature Coefficient) thermistors are widely used in temperature detection applications, such as household appliances, industrial control, and automotive electronics, due to their characteristic of decreasing resistance with increasing temperature. Conventional NTC temperature detection circuits typically use fixed pull-up or pull-down voltage division structures to convert temperature information into voltage through a voltage division resistor connected in series with the NTC, and then transmit the voltage to the main control unit for processing after analog-to-digital conversion (ADC).

[0003] However, such detection circuits in the prior art can usually only adapt to a certain temperature range of the NTC resistance variation curve, such as the low temperature section or the high temperature section, and it is difficult to achieve accurate voltage distribution and resolution in the full temperature range. The defects of this structure mainly manifest in (1) limited temperature detection range: a single pull-up or pull-down structure cannot cover the entire temperature range, especially in extremely cold or high temperature environments, the detection accuracy is significantly reduced, (2) poor circuit flexibility: the detection mode is fixed and cannot be dynamically adjusted according to the actual temperature interval, (3) low software control participation: the existing solution is a pure hardware architecture, and the main control unit only reads data and cannot actively optimize the sampling path.

[0004] Therefore, there is an urgent need for an improved NTC temperature detection scheme that can expand the temperature detection range and improve the detection accuracy through software and hardware cooperation without significantly increasing hardware costs, to meet the technical needs of temperature monitoring in a wide temperature range. SUMMARY

[0005] The present application provides an NTC temperature detection circuit to solve the problems of limited detection range, insufficient sampling accuracy, and inability to dynamically switch sampling structures according to temperature intervals in existing NTC temperature detection circuits.

[0006] In a first aspect, the present application provides an NTC temperature detection circuit, comprising: a voltage division unit, an NTC resistor, a conduction unit, a main control unit, and an analog-to-digital conversion port, wherein the main control unit comprises a signal port;

[0007] The first end of the voltage division unit is connected to a power supply, and the second end is connected to the analog-to-digital conversion port and the first end of the NTC resistor, respectively;

[0008] The third end of the voltage division unit is connected to the first end of the conduction unit;

[0009] The second end of the NTC resistor is connected to the third end of the main control unit and the conduction unit, respectively.

[0010] The second end of the conducting unit is connected to the ground;

[0011] The master control unit presets a sampling mode and a voltage threshold value, and the sampling mode includes a forward collection mode and a reverse collection mode;

[0012] The master control unit defaults the forward collection mode and detects a first voltage of the NTC resistor;

[0013] The master control unit determines whether to switch the sampling mode based on the first voltage and the size of the voltage threshold value;

[0014] The master control unit controls the signal port to output a high level or a low level based on the sampling mode, so as to switch a voltage sampling path and detect a second voltage of the NTC resistor;

[0015] The master control unit calculates the temperature of the NTC resistor according to the second voltage of the NTC resistor.

[0016] Optionally, the voltage dividing unit includes a first resistor and a second resistor, and the conducting unit is a triode;

[0017] The first end of the first resistor is connected to the power supply, and the second end is connected to the first end of the second resistor and the collector of the triode, respectively;

[0018] The first end of the second resistor is connected to the collector of the triode, and the second end is connected to the analog-digital conversion port and the first end of the NTC resistor, respectively;

[0019] The second end of the NTC resistor is connected to the signal port;

[0020] The base of the triode is connected to the signal port, and the emitter of the triode is connected to the ground;

[0021] Optionally, the master control unit defaults the forward collection mode, controls the signal port to output a low level, the triode is in a cut-off state, the voltage sampling path adopts an up-pull voltage dividing sampling path, and the analog-digital conversion port collects the first voltage of the NTC resistor.

[0022] Optionally, if the first voltage is greater than the voltage threshold value, the forward collection mode is continued to be adopted, the signal port is controlled to output a low level, the triode is in a cut-off state, the voltage sampling path adopts an up-pull voltage dividing sampling path, and the analog-digital conversion port collects the second voltage of the NTC resistor.

[0023] Optionally, if the first voltage is less than the voltage threshold, switching to the reverse collection mode, controlling the signal port to output a high level, the transistor is in a conducting state, the voltage sampling path is a pull-down voltage division sampling path, and the analog-digital conversion port collects a second voltage of the NTC resistor.

[0024] Optionally, the pull-up voltage division sampling path comprises:

[0025] The first end of the NTC resistor is connected to the analog-digital conversion port, the second end of the NTC resistor is connected to the ground, and the first resistor and the second resistor constitute a series pull-up voltage division structure.

[0026] The analog-digital conversion port collects the first voltage and the second voltage across the NTC resistor.

[0027] Optionally, the pull-down voltage division sampling path comprises:

[0028] The first end of the NTC resistor is connected to the power supply, the second end of the NTC resistor is connected to the ground through the second resistor, and the second resistor is a pull-down resistor.

[0029] The analog-digital conversion port collects the second voltage of the connection node of the second resistor and the NTC resistor.

[0030] Optionally, the temperature detection circuit further comprises a protection resistor, the base of the transistor is connected to the signal port through the protection resistor, for suppressing the base current and preventing damage to the main control unit.

[0031] Optionally, the analog-digital conversion port transmits the second voltage to the main control unit.

[0032] The main control unit calculates the resistance value of the NTC resistor based on the second voltage and a preset voltage division formula, and converts the temperature value of the NTC resistor based on the resistance value of the NTC resistor.

[0033] Optionally, the main control unit outputs the calculated temperature value of the NTC resistor to a display module. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, those skilled in the art can obtain other drawings from these drawings without any creative effort.

[0036] One or more embodiments are illustrated by way of example in the figures that are part of this disclosure and which are illustrative, but not restrictive, of the embodiments, wherein like references numerals designate corresponding, similar or like parts throughout the figures, and in which:

[0037] Figure 1 A circuit schematic diagram of a first NTC temperature detection circuit provided for an embodiment of the present application;

[0038] Figure 2 A circuit schematic diagram of a pull-up voltage division sampling path provided for an embodiment of the present application;

[0039] Figure 3 A circuit schematic diagram of a pull-down voltage division sampling path provided for an embodiment of the present application;

[0040] Figure 4 A circuit schematic diagram of a second NTC temperature detection circuit provided for an embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0042] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplification, the components and arrangements of the specific examples are described in the following. Of course, they are only examples and are not intended to limit the present application. In addition, the present application can repeatedly refer to the reference numerals and / or letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not indicate the relationship between the various embodiments and / or arrangements discussed.

[0043] Figure 1 A circuit schematic diagram of a NTC temperature detection circuit provided for an embodiment of the present application.

[0044] The NTC temperature detection circuit comprises a voltage division unit, an NTC resistor, a conduction unit, a master control unit and an analog-digital conversion port, wherein the master control unit comprises a signal port;

[0045] A first end of the voltage division unit is connected with a power supply, and a second end thereof is connected with the analog-digital conversion port and a first end of the NTC resistor, respectively;

[0046] a third end of the voltage division unit is connected with a first end of the conducting unit;

[0047] a second end of the NTC resistor is connected with a third end of the main control unit and the conducting unit respectively;

[0048] a second end of the conducting unit is connected with the ground;

[0049] the main control unit pre-sets a sampling mode and a voltage threshold, the sampling mode including a forward sampling mode and a reverse sampling mode;

[0050] the main control unit defaults the forward sampling mode, and detects a first voltage of the NTC resistor;

[0051] the main control unit judges whether to switch the sampling mode based on the first voltage and the voltage threshold;

[0052] the main control unit controls the signal port to output a high level or a low level based on the sampling mode, so as to switch a voltage sampling path and detect a second voltage of the NTC resistor;

[0053] the main control unit calculates the temperature of the NTC resistor according to the second voltage of the NTC resistor.

[0054] The NTC thermistor is a semiconductor device whose resistance decreases with temperature rise. Its basic principle is to use the temperature characteristics of the material for temperature sensing. Specifically, the resistance value of the NTC thermistor has an exponential relationship with the temperature. In the temperature detection circuit, the NTC thermistor is often designed to form a voltage division network with a voltage division unit (R1 and R2) to convert temperature changes into voltage changes. The main control unit collects the voltage value through the ADC and reverses the current temperature according to the known voltage division relationship and the NTC resistance temperature curve. As shown in Figure 1 , a first resistor R1, a second resistor R2, a triode Q1, an analog-to-digital conversion port ADC, a signal port GPIO, a protection resistor R3, and an NTC resistor NTC1. Figures 2-4 The meanings of the marked names of all components and the division of unit modules are consistent with Figure 1 , which will not be repeated hereinafter.

[0055] Further, the voltage division unit includes a first resistor and a second resistor, and the conducting unit is a triode.

[0056] A first end of the first resistor is connected with the power supply, and a second end thereof is connected with a first end of the second resistor and a collector of the triode respectively.

[0057] The first end of the second resistor is connected with the collector of the transistor, and the second end is connected with the analog-digital conversion port and the first end of the NTC resistor respectively;

[0058] The second end of the NTC resistor is connected with the signal port;

[0059] The base of the transistor is connected with the signal port, and the emitter of the transistor is connected with the ground.

[0060] In the embodiment of the application, the preset sampling mode and voltage threshold value are in the master control unit, the sampling mode includes the forward sampling mode and the reverse sampling mode, based on different sampling modes, the high level or low level is outputted from the control signal output port, so as to switch the voltage sampling path. The first detection is based on the default forward sampling mode, the approximate range of the voltage value of the NTC resistor is detected according to the size of the first voltage and the voltage threshold value, the approximate range of the temperature of the NTC resistor belongs to the high temperature range or the low temperature range is calculated according to the approximate range of the voltage value, when the temperature of the NTC resistor is in the high temperature range, the forward sampling mode is used in the second detection, when the temperature of the NTC resistor is in the low temperature range, the reverse sampling mode is used in the second detection. Through the two voltage detections of the NTC resistor, the temperature value of the NTC resistor is more accurately obtained.

[0061] Firstly, the first detection is by default in the forward sampling mode, and the first voltage of the NTC resistor is detected. Then, whether the reverse sampling mode needs to be switched or the forward sampling mode needs to be kept is judged according to the size of the first voltage and the voltage threshold value. Next, the second detection is carried out based on the result after the judgment, and the second voltage of the NTC resistor is detected. Finally, the resistance value of the NTC resistor is calculated according to the second voltage of the NTC resistor, and the temperature value of the NTC resistor is calculated according to the resistance value of the NTC resistor.

[0062] It should be noted that in the application, the resistance value, voltage value and temperature value of the NTC resistor can be converted by the formula, for example, the temperature threshold value corresponding to the voltage threshold value can be obtained by the formula, when the first voltage is higher than the voltage threshold value, it means that the temperature value of the NTC resistor is higher than the temperature threshold value, then the temperature value of the NTC resistor is in the high temperature range, the forward sampling mode is used; on the contrary, when the first voltage is lower than the voltage threshold value, it means that the temperature value of the NTC resistor is lower than the temperature threshold value, then the temperature value of the NTC resistor is in the low temperature range, the reverse sampling mode is used.

[0063] Further, the master control unit defaults the forward acquisition mode, controls the signal port to output a low level, the transistor is in a cutoff state, the voltage sampling path adopts a pull-up voltage division sampling path, and the analog-digital conversion port acquires a first voltage of the NTC resistor.

[0064] In the embodiment of the present application, the acquisition mode corresponds to the level output by the signal port. When the acquisition mode is forward acquisition, the signal port outputs a low level, the transistor is in a cutoff state, and the voltage sampling path is equivalent to a pull-up voltage division sampling path, as shown in FIG. 1, and the analog-digital conversion port acquires a first voltage of the NTC resistor. Figure 2

[0065] Further, if the first voltage is greater than the voltage threshold, the forward acquisition mode is continued, the signal port is controlled to output a low level, the transistor is in a cutoff state, the voltage sampling path adopts a pull-up voltage division sampling path, and the analog-digital conversion port acquires a second voltage of the NTC resistor.

[0066] In the embodiment of the present application, the temperature threshold corresponding to the voltage threshold is obtained by a formula according to the characteristics of the thermistor. If the first voltage is greater than the voltage threshold, that is, the temperature value of the NTC resistor is greater than the temperature threshold, the temperature value of the NTC resistor is in a high temperature range, the forward acquisition mode is continued, the signal port is controlled to output a low level, the transistor is in a cutoff state, the voltage sampling path adopts a pull-up voltage division sampling path, and the analog-digital conversion port measures a second voltage between the two ends of the NTC resistor. The present application detects the voltage of the NTC resistor twice. The first detection obtains the first voltage and compares it with the voltage threshold. In order to determine the approximate range of the voltage of the NTC resistor, the characteristics of the NTC resistor are used to determine that the temperature of the NTC resistor is in the approximate range, which is the high temperature range. The second detection obtains the second voltage to more accurately obtain the accurate voltage value in the approximate range, and then the accurate temperature value of the NTC resistor is obtained by a formula calculation.

[0067] Further, the pull-up voltage division sampling path comprises:

[0068] The first end of the NTC resistor is connected to the analog-digital conversion port, the second end of the NTC resistor is connected to the ground, and the first resistor and the second resistor constitute a series pull-up voltage division structure.

[0069] The analog-digital conversion port acquires the first voltage signal and the second voltage signal between the two ends of the NTC resistor.

[0070] As shown in FIG. 1, the first end of the NTC resistor is connected to the analog-digital conversion port, the second end of the NTC resistor is connected to the ground, and the first resistor and the second resistor constitute a series pull-up voltage division structure. Figure 2 ​As shown, in the high-temperature range, the NTC resistor is relatively small, forming an effective voltage divider with the pull-up resistor. This results in a wide voltage variation range, which is beneficial for improving the resolution and accuracy of ADC sampling. Therefore, the pull-up voltage divider structure is often used in detection areas with high temperatures. This structure requires only two voltage divider resistors (fixed resistors R1 and R2 + one NTC), does not rely on complex circuits, and is suitable for most applications where temperature acquisition requirements are not high or cost is a primary concern.

[0071] A pull-up voltage divider structure typically consists of fixed resistors (pull-up resistors R1 and R2) connected in series with an NTC thermistor, with its two ends connected to the power supply. The intermediate node connects to ground (GND) and the analog-to-digital converter (ADC). Its function is to convert the resistance change of the NTC resistor (which varies with temperature) into a voltage signal that the ADC can read. Since the NTC resistance decreases with increasing temperature, in the pull-up structure, as the temperature rises... Decrease manifests as The temperature decreases, forming a monotonically decreasing relationship, which makes it easier for the main control unit to calculate the current temperature by looking up a table or function.

[0072] Under this structure, the output voltage (i.e., the voltage at the ADC sampling point) is:

[0073]

[0074] in, The first and second voltages are measured by the analog-to-digital converter (ADC). This is the power supply voltage. This refers to the resistance value of the NTC resistor. The resistance values ​​of the pull-up voltage divider structure are (R1 resistance value + R2 resistance value).

[0075] Furthermore, if the first voltage is less than the voltage threshold, the system switches to the reverse acquisition mode, controls the signal port to output a high level, the transistor is in the on state, the voltage sampling path is a pull-down voltage divider sampling path, and the analog-to-digital conversion port acquires the second voltage signal of the NTC resistor.

[0076] like Figure 3 As shown, Figure 3The circuit schematic diagram of the pull-down voltage division sampling path provided by the embodiment of the application. In the embodiment of the application, the temperature threshold corresponding to the voltage threshold is obtained by formula according to the characteristics of the NTC resistor. If the first voltage is less than the voltage threshold, that is, the temperature value of the NTC resistor is less than the temperature threshold, the temperature value of the NTC resistor is in the low temperature range, and the negative sampling mode is switched to, the control signal port outputs a high level, the transistor is in the on state, and the voltage sampling path adopts the pull-down voltage division sampling path. At this time, the analog-digital conversion port measures the second voltage signal of the second resistance and the NTC resistance connection node.

[0077] The application detects the voltage of the NTC resistor twice. The first detection obtains the first voltage and compares it with the voltage threshold. In order to determine the approximate interval range of the NTC resistor voltage, the temperature of the NTC resistor is determined to be in the approximate interval range according to the characteristics of the NTC resistor. The second detection obtains the second voltage more accurately in the approximate range to obtain the accurate voltage value. Then, the accurate temperature value of the NTC resistor is calculated by formula.

[0078] Further, the pull-down voltage division sampling path comprises:

[0079] The first end of the NTC resistor is connected to the power supply, and the second end of the NTC resistor is connected to the ground through the second resistance, which is a pull-down resistance;

[0080] The analog-digital conversion port collects the second voltage signal of the second resistance and the NTC resistance connection node.

[0081] In the embodiment of the application, the NTC resistor is large in the low temperature range. If the pull-up structure is used, the voltage is close to , the change range is small, the ADC resolution is low, and it is not conducive to temperature measurement. When the pull-down structure is used, the voltage value is low and the voltage change is sensitive, which is more suitable for detecting temperature change in a low temperature environment, improving the resolution, and the pull-down structure circuit is simple to implement, only NTC and a resistance are connected in series to the ground, which is suitable for various master control platforms, especially for automatic sampling path switching in software and hardware collaborative design.

[0082] In the NTC temperature detection circuit, the pull-down voltage division structure refers to connecting the NTC thermistor and the fixed resistance R2 in series, and connecting them between the power supply and the ground. The NTC is close to the power supply end, the fixed resistance R2 is close to the ground end, and the analog-digital conversion port (ADC) is connected to the intermediate node of the NTC and the fixed resistance R2, so as to realize voltage detection of temperature.

[0083] Under this structure, the output voltage (i.e. the ADC sampling point voltage) is:

[0084]

[0085] wherein, the first voltage and the second voltage measured by an analog-to-digital conversion port ADC, a power supply voltage, a resistance value of the NTC resistor, a resistance value (R2 resistance value) of a pull-down voltage division structure.

[0086] Further, the temperature detection circuit further comprises a protection resistor, a base of the triode is connected with the signal port through the protection resistor, for suppressing base current and preventing damage of the main control unit.

[0087] In the embodiments of the present application, as shown in Figures 1-3 the circuit further comprises a protection resistor R3, the triode is an NPN triode, and the base of the triode is connected with the signal port through the protection resistor, for suppressing base current and preventing damage of the main control unit.

[0088] Further, the analog-to-digital conversion port transmits the second voltage signal to the main control unit;

[0089] The main control unit calculates the resistance value of the NTC resistor based on the second voltage signal and a preset voltage division formula, and converts the resistance value of the NTC resistor into a temperature value of the NTC resistor.

[0090] In the embodiments of the present application, the NTC thermistor is a semiconductor device whose resistance value decreases with the increase of temperature, and its basic principle is to use the resistance-temperature characteristics of materials for temperature sensing. Specifically, the resistance value of the NTC thermistor is exponentially related to the temperature T, and the commonly used approximate formula is:

[0091]

[0092] wherein, the NTC resistance value at the current temperature T (unit: K), the resistance value at the reference temperature (generally 25°C, i.e. 298.15K), B is the B constant of the material, with the unit of K, which depends on the material characteristics, and e is the base of the natural logarithm.

[0093] In the temperature detection circuit, the NTC thermistor is often designed to form a voltage division network with a fixed resistor of voltage division (such as the pull-up voltage division structure composed of R1 and R2, or the pull-down voltage division structure composed of R2 alone), to convert temperature change into voltage change. The main control unit collects the voltage value through the ADC and reverses the current temperature according to the known voltage division relationship and the NTC resistance temperature curve.

[0094] The preset voltage division formula is:

[0095]

[0096] in, R is the power supply voltage, and R is the fixed resistor for the voltage divider. The resistance of the thermistor at the current temperature is determined by... The measurement can be used to solve for... The temperature value can then be obtained by looking up a table or calculating using a function.

[0097] like Figure 4 As shown, Figure 4 This is a circuit diagram of the second NTC temperature detection circuit provided in the embodiments of this application. It includes a first resistor R1, a second resistor R2, a transistor Q1, an analog-to-digital converter (ADC), a signal port GPIO, a protection resistor R3, and an NTC resistor NTC1. The circuit principle is as described above. Figure 1 As described in the description, the temperature detection circuit includes a voltage divider unit, an NTC resistor, a conduction unit, a main control unit, and an analog-to-digital converter port. The main control unit includes a signal port, and the conduction unit is a transistor. The NTC thermistor and the voltage divider unit (R1 and R2) form a voltage divider network, converting temperature changes into voltage changes. The main control unit acquires this voltage value via an ADC and deduces the current temperature based on the known voltage divider relationship and the NTC resistance-temperature curve.

[0098] First, the main control unit defaults to the forward acquisition mode, outputting a low level at the control signal port to cut off the transistor. The voltage sampling path uses a pull-up voltage divider sampling path, and the analog-to-digital converter port samples the first voltage across the NTC resistor. If the first voltage is greater than the voltage threshold, the forward acquisition mode continues, with the control signal port outputting a low level to cut off the transistor. The voltage sampling path uses a pull-up voltage divider sampling path, and the analog-to-digital converter port samples the second voltage across the NTC resistor.

[0099] Compared with the prior art, this application has the following beneficial effects:

[0100] (1) Achieve wide temperature range coverage and improve detection accuracy: By setting the GPIO port of the main control unit to output high or low level, the transistor can be controlled to turn on or off, thereby dynamically switching the voltage divider structure where the NTC thermistor is located: In the default forward acquisition mode (GPIO output low level), the NTC and the pull-up resistor are connected in series to form a voltage divider network; if the voltage signal corresponding to the temperature is lower than the set threshold, the main control unit controls the GPIO to output high level, so that the transistor turns on and switches to the reverse acquisition mode. At this time, the NTC is located at the power supply end and forms a new voltage divider structure with the pull-down resistor.

[0101] The switching mechanism makes the voltage distribution of the NTC corresponding to different temperature ranges more uniform, effectively avoiding the problem of too low sampling resolution in a certain voltage range. Through technical derivation, for a temperature interval in which the NTC resistance changes by several orders of magnitude, when a single voltage division mode is used, voltage compression or a too flat change interval may occur, causing the ADC sampling accuracy to decrease, and the dual-mode structure can map the NTC resistance corresponding to different temperature ranges to a more reasonable voltage change range, improving the overall temperature measurement accuracy.

[0102] (2) Realize the soft and hardware cooperative control, and dynamically adjust the sampling structure: the application utilizes the voltage threshold set by the master control unit to judge the working interval of the current NTC, and autonomously switches the GPIO output level, realizes the dynamic adjustment of the circuit structure, and breaks through the limitation of the pure hardware structure of the traditional NTC detection circuit.

[0103] Specifically, the NTC resistance changes with temperature, and its voltage division result also changes accordingly. The master control unit can judge the current temperature interval by comparing the sampling voltage with the preset threshold. It can be technically deduced that in the low temperature range (such as 40°C to 25°C), the NTC resistance is large, and is suitable for the pull-up voltage division mode; and in the high temperature range (such as 25°C to 250°C), the NTC resistance decreases, and is suitable for the pull-down voltage division mode. By switching the voltage division path, the sampling system can maintain an appropriate voltage dynamic range in different temperature ranges, and cooperate with the fixed reference voltage ADC, to effectively improve the overall response ability and resolution of the circuit. 40°C to 25°C), the NTC resistance is large, and is suitable for the pull-up voltage division mode; and in the high temperature range (such as 25°C to 250°C), the NTC resistance decreases, and is suitable for the pull-down voltage division mode. By switching the voltage division path, the sampling system can maintain an appropriate voltage dynamic range in different temperature ranges, and cooperate with the fixed reference voltage ADC, to effectively improve the overall response ability and resolution of the circuit.

[0104] (3) Reduce the cost and structural complexity: the application only introduces a triode to realize the automatic switching of the voltage division path, avoids the high-cost structure such as multiple NTCs in parallel and complex analog switch array in the traditional wide temperature range detection scheme, simplifies the overall hardware design, and reduces the production and maintenance cost.

[0105] (4) Enhance the environmental adaptability: the scheme is suitable for complex environments such as extremely cold start and high temperature operation, has higher response ability and adaptability to temperature changes, and is widely applicable to various application scenarios such as household appliances, automobiles, industrial control, etc.

[0106] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is taken as an example for description, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction, and do not limit the protection scope of the present application. The specific working process of the units and modules in the system can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0107] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in detail in a certain embodiment can be referred to the related description of other embodiments.

[0108] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in the present application can be realized in electronic hardware or in combination of computer software and electronic hardware. Whether the functions are executed in hardware or software mode depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods for each specific application to implement the described functions, but such implementation should not be considered beyond the scope of the present application.

[0109] In the embodiments provided in the present application, it should be understood that the disclosed apparatus / terminal device and method can be implemented in other ways. For example, the apparatus / terminal device embodiments described above are only schematic, and the division of the modules or units is only a logical function division, and there can be another division in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0110] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0111] The integrated module / unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. The computer program can implement the steps of the above-mentioned various method embodiments when executed by a processor. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms. The computer readable medium can include any entity or device, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (Read-Only Memory, ROM), random access memory (Random Access Memory, RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc. that can carry the computer program code. It should be noted that the contents included in the computer readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.

[0112] The above-mentioned embodiment methods can also be completed by a computer program product, which, when running on a terminal device, enables the terminal device to execute the steps in the above-mentioned various method embodiments.

[0113] The above-mentioned embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some 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 application, and should be included in the protection scope of the present application.

Claims

1. An NTC temperature detection circuit, characterized by, The NTC temperature detection circuit comprises a voltage dividing unit, an NTC resistor, a conducting unit, a master control unit and an analog-digital conversion port, wherein the master control unit comprises a signal port; a first end of the voltage dividing unit is connected with a power supply, and a second end thereof is connected with the analog-digital conversion port and a first end of the NTC resistor respectively; a third end of the voltage dividing unit is connected with a first end of the conducting unit; a second end of the NTC resistor is connected with a third end of the master control unit and the conducting unit respectively; a second end of the conducting unit is connected with a ground; the master control unit is preset with a sampling mode and a voltage threshold value, and the sampling mode comprises a forward sampling mode and a reverse sampling mode; the master control unit defaults the forward sampling mode and detects a first voltage of the NTC resistor; the master control unit judges whether to switch the sampling mode based on the size of the first voltage and the voltage threshold value; the master control unit controls the signal port to output a high level or a low level based on the sampling mode, so as to switch a voltage sampling path and detect a second voltage of the NTC resistor; the master control unit calculates the temperature of the NTC resistor according to the second voltage of the NTC resistor; the voltage dividing unit comprises a first resistor and a second resistor, and the conducting unit is a triode; a first end of the first resistor is connected with the power supply, and a second end thereof is connected with a first end of the second resistor and a collector of the triode respectively; a first end of the second resistor is connected with the collector of the triode, and a second end thereof is connected with the analog-digital conversion port and the first end of the NTC resistor respectively; a second end of the NTC resistor is connected with the signal port; a base of the triode is connected with the signal port, and an emitter of the triode is connected with the ground.

2. The NTC temperature detection circuit according to claim 1, characterized in that, the master control unit defaults the forward sampling mode, controls the signal port to output a low level, the triode is in a cut-off state, the voltage sampling path adopts an up-pull voltage dividing sampling path, and the analog-digital conversion port collects the first voltage of the NTC resistor.

3. The NTC temperature detection circuit according to claim 2, characterized in that if the first voltage is greater than the voltage threshold value, the forward sampling mode is continuously adopted, the signal port is controlled to output a low level, the triode is in a cut-off state, the voltage sampling path adopts the up-pull voltage dividing sampling path, and the analog-digital conversion port collects a second voltage of the NTC resistor.

4. The NTC temperature detection circuit according to claim 2, characterized in that, if the first voltage is less than the voltage threshold value, the reverse sampling mode is switched, the signal port is controlled to output a high level, the triode is in a conducting state, the voltage sampling path is a down-pull voltage dividing sampling path, and the analog-digital conversion port collects the second voltage of the NTC resistor.

5. The NTC temperature detection circuit according to claim 2 or 3, characterized in that, the up-pull voltage dividing sampling path comprises: a first end of the NTC resistor is connected with the analog-digital conversion port, a second end thereof is connected with the ground, and the first resistor and the second resistor constitute a series up-pull voltage dividing structure; the analog-digital conversion port collects the first voltage and the second voltage between the two ends of the NTC resistor.

6. The NTC temperature detection circuit according to claim 4, characterized in that, the down-pull voltage dividing sampling path comprises: The first end of the NTC resistance is connected to the power supply, and the second end of the NTC resistance is connected to the second resistance, which is a pull-down resistance; The analog-digital conversion port collects a second voltage of a node where the second resistance and the NTC resistance are connected.

7. The NTC temperature detection circuit according to claim 1, characterized in that, The temperature detection circuit further comprises a protection resistance, and the base of the triode is connected to the signal port through the protection resistance, so as to inhibit the base current and prevent the main control unit from being damaged.

8. The NTC temperature detection circuit according to claim 1, characterized in that, The analog-digital conversion port transmits the second voltage to the main control unit. The main control unit calculates the resistance value of the NTC resistance based on the second voltage and a preset voltage division formula, and converts the resistance value of the NTC resistance into a temperature value of the NTC resistance.

9. The NTC temperature detection circuit according to claim 8, characterized in that, The main control unit outputs the calculated temperature value of the NTC resistance to a display module.

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