Temperature sampling circuit and system

Abstract

The embodiment of the utility model provides a temperature sampling circuit and system, and the circuit comprises a power module and a circuit following module. The circuit following module comprises a noise suppression unit, a phase compensation unit, a follower and an operational amplifier, the power supply module is connected with a first end of the noise suppression unit, and a second end and a third end of the noise suppression unit are respectively connected with a positive input end and a negative input end of the operational amplifier; the fourth end of the noise suppression unit is connected with the output end of the follower, the output end of the operational amplifier is connected with the positive input end of the follower through a fifth resistor, and the phase compensation unit is connected with the negative input end and the output end of the follower, so that the influence of the temperature drift of the operational amplifier on the temperature acquisition precision is reduced; and the oscillation of the operational amplifier follower is avoided.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a temperature sampling circuit and system. Background Technology

[0002] In the design of temperature acquisition circuits, the performance stability of components is a crucial factor. Operational amplifiers, as key components in signal conditioning, directly affect the accuracy and reliability of temperature acquisition. However, in practical applications, operational amplifiers and other components commonly exhibit temperature drift, meaning that the output signal fluctuates with changes in the ambient temperature. This temperature-induced signal variation significantly reduces the sampling accuracy of the temperature acquisition system, thus impacting subsequent data analysis and processing.

[0003] To improve the accuracy of temperature acquisition, designers often need to consider how to reduce the impact of operational amplifier (op-amp) temperature drift. A widely adopted technique to reduce this drift is to configure the op-amp as a follower, directly connecting its output to the inverting input to achieve signal buffering and isolation, thereby suppressing the impact of external interference and internal noise on acquisition accuracy to some extent. However, this connection method easily leads to a new problem in practical applications: circuit oscillation. Because op-amps have high input impedance and relatively low output impedance, when the output is directly connected to the inverting input, improper circuit parameter design can easily create positive feedback, causing self-oscillation and severely affecting the stability and accuracy of the temperature acquisition circuit. Utility Model Content

[0004] The main objective of this application is to propose a temperature sampling circuit and system that aims to reduce the impact of operational amplifier temperature drift on temperature acquisition accuracy and to prevent operational amplifier follower oscillation.

[0005] To achieve the above objectives, a first aspect of this application provides a temperature sampling circuit, the circuit comprising:

[0006] Power supply module and circuit follower module;

[0007] The circuit follower module includes a noise suppression unit, a phase compensation unit, a follower, and an operational amplifier, wherein:

[0008] The power supply module is connected to the first end of the noise suppression unit. The second and third ends of the noise suppression unit are connected to the positive and negative input ends of the operational amplifier, respectively. The fourth end of the noise suppression unit is connected to the output end of the follower. The output end of the operational amplifier is connected to the positive input end of the follower through a fifth resistor. The phase compensation unit is connected to the negative input end and the output end of the follower.

[0009] The beneficial effects of this application embodiment are: it reduces the impact of operational amplifier temperature drift on temperature acquisition accuracy and avoids operational amplifier follower oscillation. By effectively suppressing operational amplifier temperature drift, high accuracy and stability of temperature acquisition data can be ensured, avoiding data acquisition distortion caused by operational amplifier follower oscillation, which may also damage circuit components and even affect the normal operation of the entire system. This improves the accuracy and stability of temperature acquisition, and also enhances the system's anti-interference capability and overall reliability.

[0010] In one possible implementation, the power module includes a voltage source, a first resistor, a second resistor, and a thermistor, wherein a first terminal of the first resistor is connected to the positive terminal of the power source, a second terminal of the first resistor is connected to a first terminal of the voltage source, a second terminal of the voltage source is connected to both the first terminal of the second resistor and the first terminal of the voltage source, a third terminal of the voltage source is grounded, a second terminal of the second resistor is connected to a first terminal of the thermistor, and a second terminal of the thermistor is grounded.

[0011] In one possible implementation, the voltage source is a TL431 voltage regulator, used for voltage regulation and signal processing at the connection between the second terminal of the voltage source and the first terminal of the second resistor.

[0012] In one possible implementation, the noise suppression unit includes a third resistor, a third capacitor, and an eighth resistor. The third resistor is connected to the eighth resistor through the third capacitor. The third resistor and the eighth resistor are used to eliminate signal reflections, and the third capacitor is used to cancel interference signals.

[0013] In one possible implementation, the phase compensation unit includes a second capacitor and a seventh resistor, which are connected in parallel.

[0014] In one possible implementation, the first end of the fifth resistor is connected to the first end of the sixth resistor, the second end is connected to the fourth resistor, the second end of the sixth resistor is connected to the first end of the first capacitor, and is also connected to the microcontroller, and the second end of the first capacitor is grounded.

[0015] In one possible implementation, the thermistor is an NTC resistor used to adjust its resistance value according to temperature changes.

[0016] In one possible implementation, the third resistor and the third capacitor form a first low-pass filter, and the sixth resistor and the first capacitor form a second low-pass filter. The first low-pass filter and the second low-pass filter are used to suppress high-frequency interference.

[0017] In one possible implementation, the output voltage of the follower is the same as the negative input voltage of the operational amplifier.

[0018] In a second aspect, a temperature sampling system is provided, which, when executed, implements the temperature sampling circuit as described in any possible implementation of the first aspect.

[0019] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in one or more embodiments or prior art of this specification, the accompanying drawings used in the description of one or more embodiments or prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a temperature sampling circuit provided in an embodiment of this application;

[0022] Figure 2 This is a schematic diagram of a temperature sampling circuit provided in an embodiment of this application.

[0023] Figure reference numerals: Voltage source D1, follower U1, operational amplifier U2, first resistor R1, second resistor R2, third resistor R3, fourth resistor R4, fifth resistor R5, sixth resistor R6, seventh resistor R7, eighth resistor R8, thermistor TC, first capacitor C1, second capacitor C2, third capacitor C3, microcontroller MCU. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in one or more embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described one or more embodiments are merely some embodiments of this specification, and not all embodiments. All other embodiments obtained by those skilled in the art based on one or more embodiments of this specification without creative effort should fall within the protection scope of this document.

[0025] It should be noted that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] Furthermore, the technical features involved in the various embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other. The embodiments of this utility model will be further described below with reference to the accompanying drawings.

[0029] like Figure 1 and Figure 2 As shown, Figure 1 This is a schematic diagram of a temperature sampling circuit provided in an embodiment of this application. Figure 2 This is a schematic diagram of a temperature sampling circuit provided in an embodiment of this application. The circuit includes a power supply module and a circuit follower module. The circuit follower module includes a noise suppression unit, a phase compensation unit, a follower U1, and an operational amplifier U2. The power supply module is connected to the first terminal of the noise suppression unit. The second and third terminals of the noise suppression unit are connected to the positive and negative input terminals of the operational amplifier U2, respectively. The fourth terminal of the noise suppression unit is connected to the output terminal of the follower U1. The output terminal of the operational amplifier U2 is connected to the positive input terminal of the follower U1 through a fifth resistor R5. The phase compensation unit is connected to the negative input terminal and the output terminal of the follower U1.

[0030] It should be noted that in this embodiment, the follower U1 and the operational amplifier U2 are two op-amps on the same substrate with similar parameters. They have similar temperature drift characteristics so that they can cancel each other out. The output of the follower U1 is connected to the negative input of the operational amplifier U2 through the first and second terminals of the noise suppression unit. In the static state, the output of the operational amplifier U2 will generate a voltage due to its own offset voltage. At the same time, the follower U1 will also generate an opposite voltage due to the same offset voltage, which is fed back to the negative input of the operational amplifier U2. The two voltages cancel each other out at the output of the operational amplifier U2, making the output offset voltage close to zero, thereby suppressing the temperature drift of the op-amp. Temperature drift, the phenomenon where the output offset voltage of operational amplifier U2 changes with temperature, is a major obstacle in precision electronic measurement and signal processing. By suppressing temperature drift, the linearity and stability of the circuit can be significantly improved. That is, the output signal of the circuit can maintain high accuracy under different ambient temperatures, reducing errors caused by temperature changes. In addition, suppressing temperature drift also helps to extend the service life of the operational amplifier and the entire electronic system. High temperatures not only cause the performance of the operational amplifier to degrade, but may also accelerate the aging of components and shorten their service life. By controlling temperature drift, the operating temperature of components can be reduced, thereby improving the reliability and durability of the system. Small changes in output offset voltage can affect the accuracy of temperature acquisition. Therefore, suppressing the temperature drift of the operational amplifier can ensure high accuracy and stability of temperature acquisition data.

[0031] It should also be noted that when an operational amplifier is used as a follower, the output terminal is directly connected to the negative input terminal, which generates an additional phase shift. When these phase shifts accumulate to a certain extent, causing the negative feedback to turn into positive feedback at certain frequency points, the follower is prone to oscillation, leading to unstable output signals. The phase compensation unit is used to change the phase of the feedback signal. The compensation element in the phase compensation unit can introduce a phase change opposite to the original phase shift, thereby canceling part or all of the original phase shift, allowing the negative feedback to maintain its negative feedback characteristics over a wider frequency range. Specifically, phase compensation can keep the phase difference between the feedback signal and the input signal within 180 degrees at frequencies with high follower gain, thus avoiding the formation of positive feedback. In this way, even if there are parasitic oscillations inside the follower or external interference, their effects can be suppressed through phase compensation, ensuring the stable operation of the follower.

[0032] The beneficial effects of this application embodiment are: it reduces the impact of operational amplifier temperature drift on temperature acquisition accuracy and avoids operational amplifier follower oscillation. By effectively suppressing operational amplifier temperature drift, high accuracy and stability of temperature acquisition data can be ensured, avoiding data acquisition distortion caused by operational amplifier follower oscillation, which may also damage circuit components and even affect the normal operation of the entire system. This improves the accuracy and stability of temperature acquisition, and also enhances the system's anti-interference capability and overall reliability.

[0033] In one possible implementation, the power module includes a voltage source D1, a first resistor R1, a second resistor R2, and a thermistor TC. The first terminal of the first resistor R1 is connected to the positive terminal of the power supply, the second terminal of the first resistor R1 is connected to the first terminal of the voltage source D1, the second terminal of the voltage source D1 is connected to the first terminal of the second resistor R2 and the first terminal of the voltage source D1, the third terminal of the voltage source D1 is grounded, the second terminal of the second resistor R2 is connected to the first terminal of the thermistor TC, and the second terminal of the thermistor TC is grounded.

[0034] In some embodiments, the second terminal of voltage source D1 is connected to the first terminal of the second resistor R2 and the first terminal of voltage source D1. Voltage source D1 is used to clamp and filter the voltage at the connection point between the first terminal of the second resistor R2 and the second terminal of voltage source D1. Clamping refers to limiting the voltage at a certain point to a specific range. Voltage source D1 is used to ensure that the voltage at the connection point does not exceed a predetermined range due to fluctuations in the power supply voltage. Voltage source D1 contains a reference voltage source. When the voltage at the connection point exceeds the voltage of this reference voltage source, voltage source D1 will conduct and maintain a stable output voltage by adjusting the current between the anode and cathode. Filtering refers to removing unwanted frequency components from the signal. When there are fluctuations or noise in the power supply voltage, these fluctuations or noises will attempt to affect the voltage at the connection point. However, due to the clamping effect of voltage source D1, the voltage at the connection point is limited to a relatively stable range, thus effectively suppressing or reducing fluctuations and noise.

[0035] In one possible implementation, the voltage source D1 is a TL431 voltage regulator, used to regulate and process the voltage at the connection between the second terminal of the voltage source D1 and the first terminal of the second resistor R2.

[0036] It should be noted that the TL431 is an adjustable precision parallel voltage regulator, characterized by adjustable output voltage, fast dynamic response, low output impedance, good linearity, and high thermal stability. The internal structure of the TL431 mainly includes a 2.5V precision reference voltage source, an error amplifier, and a power regulation transistor. Its working principle is based on the internal error amplifier. When the voltage at the connection point between the first terminal of the second resistor R2 and the second terminal of the voltage source D1 changes, the error amplifier detects this change and adjusts the conduction level of the power regulation transistor to change the output voltage, maintaining a preset relationship between the output voltage and the voltage at the connection point. Specifically, when the voltage at the connection point increases, the error amplifier outputs a larger control signal, increasing the conduction level of the power regulation transistor, thereby reducing the output voltage; conversely, when the voltage at the connection point decreases, the error amplifier outputs a smaller control signal, decreasing the conduction level of the power regulation transistor, thereby increasing the output voltage.

[0037] In one possible implementation, the noise suppression unit includes a third resistor R3, a third capacitor C3, and an eighth resistor R8. The third resistor R3 is connected to the eighth resistor R8 through the third capacitor C3. The third resistor R3 and the eighth resistor R8 are used to eliminate signal reflection, and the third capacitor C3 is used to cancel interference signals.

[0038] In some embodiments, the third resistor R3 and the eighth resistor R8 in the noise suppression unit are used to eliminate signal reflection. For example, when the output impedance of the follower U1 is very small and the input impedance of the operational amplifier U2 is very large, it will cause impedance discontinuity in the signal loop, resulting in signal reflection. The third resistor R3 and the eighth resistor R8 can achieve impedance matching, which helps to reduce reflection. The third capacitor C3 is used to cancel interference signals. For example, when a strong interference is introduced at the positive input terminal of the operational amplifier U2, since the voltage of the capacitor cannot change abruptly, the interference will be introduced at one end of the third capacitor C3. The third capacitor C3 will quickly lead the interference to the other end. That is, if interference is introduced at the positive or negative input terminal of the operational amplifier U2, it will quickly appear at the negative or positive input terminal. Therefore, the interference will be canceled when it passes through the operational amplifier U2.

[0039] In one possible implementation, the phase compensation unit includes a second capacitor C2 and a seventh resistor R7, which are connected in parallel.

[0040] It should be noted that when an operational amplifier is used as a follower, the output terminal is directly connected to the negative input terminal, which generates an additional phase shift. When these phase shifts accumulate to a certain extent, causing the negative feedback to turn into positive feedback at certain frequency points, the follower is prone to oscillation, leading to unstable output signals. A phase compensation unit is used to change the phase of the feedback signal. The compensation element in the phase compensation unit can introduce a phase change opposite to the original phase shift, thereby canceling out part or all of the original phase shift. This allows the negative feedback to maintain its negative feedback characteristics over a wider frequency range. Specifically, phase compensation ensures that at frequencies with high follower gain, the phase difference between the feedback signal and the input signal remains within 180 degrees, thus preventing the formation of positive feedback. In this way, even if there are parasitic oscillations within the follower or external interference, phase compensation can suppress their effects, ensuring stable operation of the follower.

[0041] In one possible implementation, the first end of the fifth resistor R5 is connected to the first end of the sixth resistor R6, and the second end is connected to the fourth resistor R4. The second end of the sixth resistor R6 is connected to the first end of the first capacitor C1 and also connected to the microcontroller MCU. The second end of the first capacitor C1 is grounded.

[0042] It should be noted that the output terminal of operational amplifier U2 is connected to the fourth resistor R4 and the fifth resistor R5. Follower U1 returns to the negative input terminal of operational amplifier U2. Since the current flowing into the eighth resistor R8 can be regarded as zero when operational amplifier U2 is in linear state, that is, the output voltage of follower U1 is the same as the voltage at the negative input terminal of operational amplifier U2, and the voltage at the positive input terminal of follower U1 is the same as the voltage at the output terminal. Therefore, the amplification factor of follower U1 and operational amplifier U2 is 1 + R5 / R4.

[0043] In one possible implementation, the thermistor TC is an NTC resistor used to adjust its resistance value according to temperature changes.

[0044] It's worth noting that NTC resistors offer advantages such as high precision, high stability, small size, and low cost. The resistance of an NTC resistor decreases as temperature increases, resulting in high sensitivity and the ability to accurately detect minute temperature changes. This is particularly important for systems requiring high-precision temperature measurement. Furthermore, NTC resistors exhibit good stability, maintaining consistent performance even at high temperatures without losing accuracy due to environmental changes. In addition, their small size makes them easy to integrate into various devices, minimizing space requirements. Their relatively low cost and ease of manufacturing and use reduce overall system costs and improve cost-effectiveness.

[0045] In one possible implementation, the third resistor R3 and the third capacitor C3 form a first low-pass filter, and the sixth resistor R6 and the first capacitor C1 form a second low-pass filter. The first low-pass filter and the second low-pass filter are used to suppress high-frequency interference.

[0046] It's important to note that low-pass filters can remove high-frequency noise and interference signals. During temperature acquisition, due to the complex environment, the sensor output signal is often affected by various high-frequency noises and interferences. If these noises and interferences are not filtered out, they will seriously affect the accuracy of temperature measurement. Low-pass filters can effectively remove these high-frequency noises and interferences, making the output signal cleaner and thus improving the accuracy of temperature measurement. Secondly, low-pass filters can also smooth the sensor output signal. Since the resistance of an NTC resistor changes with temperature, generating a corresponding voltage signal, this change is often sudden and discontinuous. Directly acquiring and processing this signal may lead to large data fluctuations, affecting the stability of temperature measurement. Low-pass filters can smooth this sudden signal change, making the output signal more stable and thus improving the stability of temperature measurement.

[0047] In one possible implementation, the output voltage of the follower U1 is the same as the negative input voltage of the operational amplifier U2.

[0048] It should be noted that the output terminal of operational amplifier U2 is connected to the fourth resistor R4 and the fifth resistor R5. Follower U1 returns to the negative input terminal of operational amplifier U2. Since the current flowing into the eighth resistor R8 can be regarded as zero when operational amplifier U2 is in linear state, that is, the output voltage of follower U1 is the same as the voltage at the negative input terminal of operational amplifier U2, and the voltage at the positive input terminal of follower U1 is the same as the voltage at the output terminal. Therefore, the amplification factor of follower U1 and operational amplifier U2 is 1 + R5 / R4.

[0049] In a second aspect, a temperature sampling system is provided, which, when executed, implements the temperature sampling circuit as described in any possible implementation of the first aspect.

[0050] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0051] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0052] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0053] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0054] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0055] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A temperature sampling circuit, characterized by, The circuit comprises: a power module and a circuit following module; the circuit following module comprises a noise suppression unit, a phase compensation unit, a follower and an operational amplifier, wherein: the power module is connected to a first end of the noise suppression unit, a second end and a third end of the noise suppression unit are connected to a positive input end and a negative input end of the operational amplifier respectively, a fourth end of the noise suppression unit is connected to an output end of the follower, an output end of the operational amplifier is connected to a positive input end of the follower through a fifth resistor, and the phase compensation unit is connected to a negative input end and an output end of the follower.

2. The temperature sampling circuit of claim 1, wherein, the power module comprises a voltage source, a first resistor, a second resistor and a thermistor, wherein a first end of the first resistor is connected to a positive electrode of a power supply, a second end of the first resistor is connected to a first end of the voltage source, a second end of the voltage source is connected to a first end of the second resistor and a first end of the voltage source, a third end of the voltage source is grounded, and a second end of the second resistor is connected to a first end of the thermistor, and a second end of the thermistor is grounded.

3. The temperature sampling circuit of claim 2, wherein, the voltage source is a TL431 voltage stabilizer, which is used for voltage stabilizing control and signal processing at a connection between the second end of the voltage source and the first end of the second resistor.

4. The temperature sampling circuit of claim 1, wherein, the noise suppression unit comprises a third resistor, a third capacitor and an eighth resistor, the third resistor is connected to the eighth resistor through the third capacitor, the third resistor and the eighth resistor are used for eliminating signal reflection, the third capacitor is used for canceling interference signals, and the third resistor and the third capacitor constitute a first low-pass filter for suppressing high-frequency interference.

5. The temperature sampling circuit of claim 1, wherein, the phase compensation unit comprises a second capacitor and a seventh resistor, and the second capacitor and the seventh resistor are connected in parallel.

6. The temperature sampling circuit of claim 1, wherein, a first end of the fifth resistor is connected to a first end of a sixth resistor, a second end of the fifth resistor is connected to a fourth resistor, a second end of the sixth resistor is connected to a first end of a first capacitor, and the first end of the first capacitor is also connected to a microcontroller, a second end of the first capacitor is grounded, and the sixth resistor and the first capacitor constitute a second low-pass filter for suppressing high-frequency interference.

7. The temperature sampling circuit of claim 2, wherein, the thermistor is an NTC resistor, which is used for adjusting resistance value according to temperature change.

8. The temperature sampling circuit of claim 1, wherein, a voltage at an output end of the follower is the same as a voltage at a negative input end of the operational amplifier.

9. A temperature sampling system, characterized by, a temperature sampling circuit comprising any one of claims 1-8.

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