A full-temperature-range NTC acquisition circuit for automobiles

Abstract

This utility model relates to an NTC acquisition circuit for a full-temperature range automotive circuit, including an NTC resistor, a power supply, and an MCU, as well as a multi-level pull-up resistor switching module. The multi-level pull-up resistor switching module consists of three parallel pull-up resistor switching branches. Each pull-up resistor switching branch includes a MOSFET and a pull-up resistor. The gate of the MOSFET in each branch is connected to different output enable terminals of the MCU. The MCU controls and only controls the MOSFET in any one of the pull-up resistor switching branches to conduct. Using the above technical solution, this utility model intelligently controls the three MOSFETs through the MCU, automatically switching them to the matching pull-up resistors (47k ohms, 4.7k ohms, and 1k ohms) according to the real-time temperature range. This ensures that the voltage division between the NTC resistor and the pull-up resistor is always within the optimal acquisition range of the ADC, thus maintaining high-precision sampling over a wide temperature range from -40℃ to 150℃, significantly improving the accuracy and reliability of temperature measurement.

Description

Technical Field

[0001] This utility model relates to the field of automotive temperature detection technology, and in particular to an NTC acquisition circuit for the full temperature range of automobiles. Background Technology

[0002] In automotive electronic systems, the accuracy and reliability of temperature monitoring are crucial for the safe operation and performance of vehicles. NTC resistors (negative temperature coefficient thermistors) are widely used as temperature sensing elements due to their advantages such as high sensitivity, fast response speed, and low cost. However, the automotive operating environment is complex, with a wide temperature range, extending from -40°C in cold regions to 150°C near the engine compartment. Within this extreme temperature range, the resistance of NTC resistors changes dramatically: at -40°C, the resistance can reach hundreds of kiloohms, while at 150°C it is only a few ohms.

[0003] Traditional NTC acquisition circuits typically use a single fixed-value pull-up resistor for voltage division sampling, which has significant drawbacks: In low-temperature regions, the NTC resistor value is too large, causing the sampling voltage to approach the power supply voltage, resulting in a significant decrease in the effective sampling resolution of the ADC (Analog-to-Digital Converter) and a substantial increase in measurement error; in high-temperature regions, the NTC resistor value is too small, causing the sampling voltage to approach 0V, which also leads to insufficient ADC resolution and a severe decrease in measurement accuracy. This single-resistor structure is difficult to maintain high sampling accuracy across the entire temperature range, limiting its application in high-precision temperature monitoring scenarios such as automotive.

[0004] Therefore, an NTC acquisition circuit that can adapt to different temperature ranges and dynamically adjust the pull-up resistor value is needed to improve the sampling accuracy and system reliability across the entire temperature range. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing an automotive full-temperature-range NTC acquisition circuit, which solves the problem that the single resistor structure in traditional NTC acquisition circuits makes it difficult to maintain high sampling accuracy across the entire temperature range.

[0006] The technical solution of this utility model is as follows: an NTC acquisition circuit for a full temperature range of automobiles, including an NTC resistor, a power supply, and an MCU, and further including a multi-level pull-up resistor switching module connected in series with the NTC resistor and connected between the power supply and ground; the multi-level pull-up resistor switching module consists of three parallel pull-up resistor switching branches; each of the pull-up resistor switching branches includes a MOSFET and a pull-up resistor, and the pull-up resistor values ​​in the three pull-up resistor switching branches are different;

[0007] The gate of the MOS transistor in each of the pull-up resistor switching branches is connected to different output enable terminals of the MCU. Based on the MCU, the MOS transistor in any one of the pull-up resistor switching branches is turned on, thereby driving the pull-up resistor and NTC resistor in that pull-up resistor switching branch to divide the voltage and generate a corresponding voltage divider signal. The generated voltage divider signal is received by the input enable terminal of the MCU connected between the multi-position pull-up resistor switching module and the NTC resistor.

[0008] A further feature of this invention is that the multi-position pull-up resistor switching module includes a first pull-up resistor switching branch composed of a first MOS transistor and a first pull-up resistor, a second pull-up resistor switching branch composed of a second MOS transistor and a second pull-up resistor, and a third pull-up resistor switching branch composed of a third MOS transistor and a third pull-up resistor.

[0009] One end of the first pull-up resistor, one end of the second pull-up resistor, and one end of the third pull-up resistor are respectively connected to the drain of the first MOSFET, the second MOSFET, and the third MOSFET. The other ends of the first pull-up resistor, the second pull-up resistor, and the third pull-up resistor are all connected to the NTC resistor. The sources of the first MOSFET, the second MOSFET, and the third MOSFET are connected to the power supply.

[0010] A further feature of this invention is that the resistance values ​​of the first pull-up resistor, the second pull-up resistor, and the third pull-up resistor are 47k ohms, 4.7k ohms, and 1k ohms, respectively.

[0011] A further feature of this invention is that a current-limiting resistor is connected between the gate of the MOS in each of the pull-up resistor switching branches and the corresponding output enable terminal of the MCU.

[0012] A further feature of this invention is that a filter resistor is connected between the multi-position pull-up resistor switching module and the input enable terminal of the MCU, and a first capacitor is connected between the input enable terminal of the MCU and ground. The filter resistor and the first capacitor constitute an RC filter circuit.

[0013] A further feature of this invention is that a second capacitor for anti-static purposes is connected between the NTC resistor and ground.

[0014] This utility model's automotive full-temperature-range NTC acquisition circuit achieves high-precision acquisition of NTC resistance across the entire temperature range of -40℃ to 150℃ by employing three MOSFETs to switch pull-up resistors with different resistance values. It offers the following significant advantages:

[0015] 1. High-precision measurement across the entire temperature range: Traditional NTC acquisition circuits use a single fixed-value pull-up resistor. At extreme temperatures (such as extremely high NTC resistance at low temperatures and extremely low resistance at high temperatures), the ADC sampling voltage will approach the power supply voltage or ground level, significantly reducing the effective resolution and measurement accuracy of the ADC. This invention uses an MCU to intelligently control three MOSFETs, automatically switching to the matching pull-up resistors (47k ohms, 4.7k ohms, and 1k ohms) according to the real-time temperature range. This ensures that the voltage division between the NTC resistor and the pull-up resistor is always within the optimal acquisition range of the ADC, thus maintaining high-precision sampling over a wide temperature range from -40℃ to 150℃, significantly improving the accuracy and reliability of temperature measurement.

[0016] 2. Strong adaptability and fast response: This invention features adaptive control logic. The MCU can determine the current temperature range based on the collected voltage value and quickly switch to the corresponding pull-up resistor path. This process requires no external intervention, achieving fully automatic and real-time resistor matching, adapting to the rapidly changing temperature environment in automobiles, and ensuring the timeliness and stability of the system response.

[0017] 3. Strong anti-interference capability, suitable for harsh automotive environments: The circuit design includes current-limiting resistors (R1, R2, R3), port anti-static capacitors (C2), and RC filter circuits (R7, C1), which effectively suppress electromagnetic interference and voltage fluctuations, and have good anti-interference and environmental adaptability.

[0018] 4. Simple structure and controllable cost: This utility model achieves the switching of multiple pull-up resistors by using a common combination of MOSFETs and pull-up resistors. It does not require complex analog front-ends or high-cost ADC devices. The circuit structure is simple and clear, easy to implement and integrate, and has good engineering feasibility and economy.

[0019] 5. Good compatibility and expandability: This circuit design allows for flexible adjustment of the pull-up resistor value and switching strategy according to specific NTC resistor models and temperature range requirements, exhibiting excellent customizability and expandability, and is suitable for different types of automotive electronic temperature sensing applications. Attached Figure Description

[0020] Figure 1 This is a circuit schematic diagram of a specific embodiment of the present invention. Detailed Implementation

[0021] The technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0022] Furthermore, the technical solutions of the various embodiments of this utility model can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0023] like Figure 1 As shown, an automotive full-temperature range NTC acquisition circuit includes an NTC resistor, a power supply, and an MCU, and also includes a multi-position pull-up resistor switching module connected in series with the NTC resistor and then connected between the power supply and ground.

[0024] The multi-position pull-up resistor switching module consists of three parallel pull-up resistor switching branches; each of the pull-up resistor switching branches includes a MOSFET and a pull-up resistor, and the pull-up resistor values ​​in the three pull-up resistor switching branches are different.

[0025] The gates of the MOSFETs in each pull-up resistor switching branch are connected to different output enable pins of the MCU. The MCU controls only one MOSFET in each pull-up resistor switching branch to turn on, thereby driving the pull-up resistor and NTC resistor in that branch to divide the voltage and generate a corresponding voltage divider signal. This voltage divider signal is received by the MCU_A_Check input enable pin of the MCU, which is connected between the multi-position pull-up resistor switching module and the NTC resistor. The MCU_A_Check input enable pin is the ADC enable pin.

[0026] Specifically, the multi-position pull-up resistor switching module includes a first pull-up resistor switching branch composed of a first MOS transistor and a first pull-up resistor, a second pull-up resistor switching branch composed of a second MOS transistor and a second pull-up resistor, and a third pull-up resistor switching branch composed of a third MOS transistor and a third pull-up resistor.

[0027] The resistance values ​​of the first pull-up resistor, the second pull-up resistor, and the third pull-up resistor are selected as 47k ohms, 4.7k ohms, and 1k ohms, respectively.

[0028] One end of the first pull-up resistor R4, one end of the second pull-up resistor R5, and one end of the third pull-up resistor R6 are connected to the drains of the first MOSFET MOS1, the second MOSFET MOS2, and the third MOSFET MOS3, respectively. The other ends of the first pull-up resistor R4, the second pull-up resistor R5, and the third pull-up resistor R6 are all connected to an NTC resistor. The NTC resistor is connected to the ICD_A_Check position. The sources of the first MOSFET MOS1, the second MOSFET MOS2, and the third MOSFET MOS3 are connected to the power supply NW0_5V0. In this embodiment, the first MOSFET MOS1, the second MOSFET MOS2, and the third MOSFET MOS3 are P-channel MOSFETs, which are turned on when the gate is low (controlled by the MCU).

[0029] Specifically, a current-limiting resistor is connected between the gate of the MOS in each pull-up resistor switching branch and the corresponding output enable terminal of the MCU. In this embodiment, the current-limiting resistor includes resistors R1, R2 and R3.

[0030] The gate of the first MOSFET MOS1 is connected to one end of resistor R3, and the other end of resistor R3 is connected to the output enable terminal MCU_A_Check_EN3 of the MCU; the gate of the second MOSFET MOS2 is connected to one end of resistor R2, and the other end of resistor R2 is connected to the output enable terminal MCU_A_Check_EN2 of the MCU; the gate of the third MOSFET MOS3 is connected to one end of resistor R1, and the other end of resistor R1 is connected to the output enable terminal MCU_A_Check_EN1 of the MCU.

[0031] A filter resistor R7 is connected between the multi-level pull-up resistor switching module and the input enable terminal of the MCU. A first capacitor C1 is connected between the input enable terminal of the MCU and ground. The filter resistor R7 and the first capacitor C1 constitute an RC filter circuit. A second capacitor C2 for anti-static purposes is connected between the NTC resistor and ground. This RC filter circuit and the second capacitor C2 effectively suppress electromagnetic interference and voltage fluctuations, and have good anti-interference and environmental adaptability.

[0032] In this embodiment, temperature testing is performed by placing the temperature control element with the circuit of this embodiment in an environment ranging from -40℃ to 150℃, and testing is conducted every 5℃ to obtain the corresponding pull-up resistor value, resistance error, and temperature accuracy.

[0033]

[0034]

[0035]

[0036] Table 1: Accuracy of Full-Range Temperature Measurement

[0037] The results are shown in Table 1. The resistance error is less than 5%. In the low temperature range, the temperature accuracy measurement does not exceed 1℃. In the high temperature range, the maximum temperature accuracy measurement is only 1.2℃.

[0038] Therefore, this invention automatically switches to the matching pull-up resistor (47k ohms, 4.7k ohms and 1k ohms) according to the real-time temperature range, so that the voltage division between the NTC resistor and the pull-up resistor is always in the optimal acquisition range of the ADC, ensuring high-precision sampling in a wide temperature range of -40℃ to 150℃, making temperature measurement more accurate and reliable.

Claims

1. An automotive full-temperature range NTC acquisition circuit, comprising an NTC resistor, a power supply, and an MCU, characterized in that: It also includes a multi-position pull-up resistor switching module connected in series with an NTC resistor between the power supply and ground; the multi-position pull-up resistor switching module consists of three parallel pull-up resistor switching branches; each of the pull-up resistor switching branches includes a MOSFET and a pull-up resistor, and the pull-up resistor values ​​in the three pull-up resistor switching branches are different. The gate of the MOS transistor in each pull-up resistor switching branch is connected to different output enable terminals of the MCU. Based on the MCU, the MOS transistor in any one of the pull-up resistor switching branches is turned on, thereby driving the pull-up resistor and NTC resistor in that pull-up resistor switching branch to divide the voltage and generate a corresponding voltage divider signal. The generated voltage divider signal is received by the input enable terminal of the MCU connected between the multi-position pull-up resistor switching module and the NTC resistor.

2. The automotive full temperature range NTC collection circuit according to claim 1, characterized in that: The multi-position pull-up resistor switching module includes a first pull-up resistor switching branch composed of a first MOSFET and a first pull-up resistor, a second pull-up resistor switching branch composed of a second MOSFET and a second pull-up resistor, and a third pull-up resistor switching branch composed of a third MOSFET and a third pull-up resistor. One end of the first pull-up resistor, one end of the second pull-up resistor, and one end of the third pull-up resistor are respectively connected to the drain of the first MOSFET, the second MOSFET, and the third MOSFET. The other ends of the first pull-up resistor, the second pull-up resistor, and the third pull-up resistor are all connected to the NTC resistor. The sources of the first MOSFET, the second MOSFET, and the third MOSFET are connected to the power supply.

3. The automotive full temperature range NTC collection circuit according to claim 2, characterized in that: The resistance values ​​of the first pull-up resistor, the second pull-up resistor, and the third pull-up resistor are 47k ohms, 4.7k ohms, and 1k ohms, respectively.

4. The automotive full temperature range NTC collection circuit according to claim 1, characterized in that: A current-limiting resistor is connected between the gate of the MOS in each pull-up resistor switching branch and the corresponding output enable terminal of the MCU.

5. The automotive full temperature range NTC collection circuit according to claim 1, characterized in that: A filter resistor is connected between the multi-level pull-up resistor switching module and the input enable terminal of the MCU. A first capacitor is connected between the input enable terminal of the MCU and ground. The filter resistor and the first capacitor constitute an RC filter circuit.

6. The automotive full temperature range NTC collection circuit according to claim 1, characterized in that: A second capacitor for anti-static purposes is connected between the NTC resistor and ground.

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