Temperature signal input differential circuit

Abstract

The utility model relates to a temperature signal input differential circuit mainly solves the technical problem that traditional temperature signal input circuit temperature drift is big, common mode suppression is insufficient, temperature measurement range is limited, anti -interference ability is poor and depends on the problem of the technology of putting. The utility model discloses power supply anti -reversal circuit, power supply voltage signal acquisition circuit, voltage division differential processing circuit, power supply anti -reversal circuit is the power supply voltage signal acquisition circuit, voltage division differential processing circuit power supply, obtains the output voltage of power supply anti -reversal circuit through power supply voltage signal acquisition circuit, gathers voltage signal after voltage division through voltage division differential processing circuit, gathers the voltage of temperature sensor both ends. According to voltage division resistance R3, R4 calculates the resistance of temperature sensor, to obtain corresponding ambient temperature, realized simple structure, low in cost, high accuracy, temperature drift compensation, common mode suppression, temperature measurement range is big, anti -interference ability is strong, the temperature signal input differential circuit of diagnosable fault.

Description

Technical Field

[0001] This utility model relates to a temperature signal input circuit, specifically a temperature signal input differential circuit. Background Technology

[0002] In vehicle electronic controllers (such as electronic control units (ECUs), retarder control units (RCUs), battery management systems (BMSs), etc.), accurate acquisition of temperature signals is crucial to system reliability.

[0003] Traditional temperature signal input circuits often employ single-ended amplification or filtering designs. The single-ended amplification circuit works as follows: the signal output from sensors such as thermistors and thermocouples is input to the non-inverting or inverting input of an operational amplifier (op-amp) through a resistor network. The op-amp amplifies the input signal based on the ratio of the feedback resistor to the input resistance. The amplified signal can then be directly used for subsequent processing or display. Filtering circuits typically consist of one or more capacitors and resistors, used to filter the input signal.

[0004] Patent CN104748877B discloses a linear signal acquisition circuit for a temperature sensor, including a voltage divider circuit, a single operational amplifier (first operational amplifier), a series voltage circuit, and a differential signal filtering and amplification circuit. The voltage divider circuit outputs a set voltage to the non-inverting input of the first operational amplifier, and the inverting input and output of the first operational amplifier are respectively connected to the series voltage circuit, which includes an NTC-type temperature sensor.

[0005] However, traditional temperature signal input circuits have the following problems: 1) Large temperature drift: The temperature drift characteristics of ordinary operational amplifiers affect the measurement accuracy under low temperature (-40℃) or high temperature (125℃) conditions. Low-power and highly integrated operational amplifiers experience increased threshold voltage drift and nonlinear effects when approaching ultra-low temperatures; 2) Insufficient common-mode rejection: When the sensor leads are long, common-mode noise (such as ground interference) is difficult to filter out effectively; 3) Limited temperature measurement range: To maximize the accuracy of temperature acquisition and resolution, traditional temperature signal input circuits usually shorten the temperature measurement range; 4) Poor anti-interference capability: Electromagnetic interference in the vehicle environment (such as radiation from motors and high-voltage wiring harnesses) can easily lead to signal distortion; 5) Dependence on operational amplifiers, resulting in complex circuits and increased costs. Utility Model Content

[0006] The purpose of this invention is to solve the technical problems of traditional temperature signal input circuits, such as large temperature drift, insufficient common-mode rejection, limited temperature measurement range, poor anti-interference ability, as well as complex circuits and increased costs. A differential temperature signal input circuit is proposed.

[0007] To solve the above-mentioned technical problems, the technical solution provided by this utility model is as follows:

[0008] A temperature signal input differential circuit is characterized by including a power supply anti-reverse circuit, a power supply voltage signal acquisition circuit, and a voltage divider differential processing circuit.

[0009] The power supply anti-reverse circuit is used to supply power to the power supply voltage signal acquisition circuit and the voltage divider differential processing circuit.

[0010] The power supply voltage signal acquisition circuit includes resistors R1 and R2 for voltage division, and a filter capacitor C1; one end of resistor R1 is connected to the output terminal TEM POWER of the power supply anti-reverse circuit, and the other end is connected to one end of resistor R2 at point D; the other end of resistor R2 is grounded; the filter capacitor C1 is connected in parallel with resistor R2.

[0011] The voltage divider differential processing circuit includes a temperature sensor installed on the target under test, resistors R3, R4, R5, and R7, and a voltage acquisition module.

[0012] One end of resistor R3 is connected to the output terminal TEM POWER of the power supply circuit, and the other end is connected to one end of the temperature sensor at point A. The other end of the temperature sensor is connected to one end of resistor R4 at point C, and the other end of resistor R4 is grounded.

[0013] The voltage acquisition module is used to acquire voltage signals and send the voltage signals to an external processing circuit for calculation.

[0014] One end of the resistor R5 is connected to point A, and the other end is connected to the first acquisition port ADC H of the voltage acquisition module; the first acquisition port ADC H is used to acquire the voltage signal at point A.

[0015] One end of the resistor R7 is connected to point C, and the other end is connected to the second acquisition port ADCL of the voltage acquisition module; the second acquisition port ADCL is used to acquire the voltage signal at point C.

[0016] The third acquisition port ADC POWER of the voltage acquisition module is connected to point D and is used to acquire the voltage signal at point D.

[0017] Furthermore, the voltage divider differential processing circuit also includes inductor L1 and capacitors C2 and C3;

[0018] One end of the inductor L1 is connected to point A, and the other end is connected to one end of the temperature sensor at point B. The equivalent resistance of the inductor L1 is 0 to 1 Ω.

[0019] The capacitors C2 and C3, together with the inductor L1, form a π-type filter module.

[0020] Furthermore, the voltage divider differential processing circuit also includes a voltage clamping circuit, which includes diodes D2, D3, D4, and D5.

[0021] The positive terminals of diodes D2 and D4 are grounded, and their negative terminals are connected to the positive terminals of diodes D3 and D5, respectively. The negative terminals of diodes D3 and D5 are connected to a 5V power supply.

[0022] The negative terminals of diodes D2 and D4 are also connected to the other ends of resistors R5 and R7, respectively.

[0023] Furthermore, the voltage divider differential processing circuit also includes an RC filter circuit, which includes resistors R6 and R8, and capacitors C4 and C5.

[0024] One end of resistor R6 is connected to the other end of resistor R5. The other end of resistor R6 is simultaneously connected to the first acquisition port ADC H of the voltage acquisition module and one end of capacitor C4. The other end of capacitor C4 is grounded, forming an RC filter circuit.

[0025] One end of resistor R8 is connected to the other end of resistor R7. The other end of resistor R8 is connected to the second acquisition port ADC L of the voltage acquisition module and one end of capacitor C5. The other end of capacitor C5 is grounded, forming another RC filter circuit.

[0026] Furthermore, the temperature sensor is an NTC sensor with a resistance of 10kΩ at 25℃ and an operating temperature range of -40℃ to 150℃. The resistance of the temperature sensor decreases as the ambient temperature increases.

[0027] Furthermore, the resistors R3 and R4 are of the same type, with an accuracy class of ±0.1% or higher, a temperature drift of less than or equal to 25ppm / ℃, and a resistance value of less than 1kΩ.

[0028] Furthermore, the resistors R1 and R2 are of the same type, and the accuracy class of resistors R1 and R2 is higher than or equal to ±0.1%, and the temperature drift is less than or equal to 25ppm / ℃;

[0029] Resistors R1 and R2 have the same resistance value, both ranging from 30K to 50K.

[0030] The capacitance of the filter capacitor C1 is 100NF.

[0031] Furthermore, the power supply anti-reverse circuit includes a 5V power supply and a diode D1; the positive terminal of the diode D1 is connected to the power supply, and the negative terminal serves as the output terminal TEM POWER of the power supply anti-reverse circuit.

[0032] Furthermore, the sum of the resistance values ​​of resistors R5 and R6 is greater than 10kΩ and less than 40kΩ;

[0033] The sum of the resistance values ​​of resistors R7 and R8 is greater than 10kΩ and less than 40kΩ;

[0034] The resistors R5 and R7 have the same resistance value, and the resistors R6 and R8 have the same resistance value.

[0035] The beneficial effects of this utility model are:

[0036] 1. This utility model discloses a temperature signal input differential circuit, comprising a power supply reverse protection circuit, a power supply voltage signal acquisition circuit, and a voltage divider differential processing circuit. The power supply reverse protection circuit supplies power to the power supply voltage signal acquisition circuit and the voltage divider differential processing circuit. The power supply voltage signal acquisition circuit acquires the output voltage of the power supply reverse protection circuit, and the voltage divider differential processing circuit acquires the voltage signal after voltage division, thereby acquiring the voltage across the temperature sensor. The resistance value of the temperature sensor is calculated based on the voltage divider resistors R3 and R4, thereby obtaining the corresponding ambient temperature. This invention achieves a temperature signal input differential circuit with simple structure, low cost, high accuracy, temperature drift compensation, common-mode rejection, large temperature measurement range, strong anti-interference ability, and fault diagnosis capability.

[0037] 2. This utility model discloses a temperature signal input differential circuit. In the power supply reverse protection circuit, the voltage difference of diode D1 changes with the ambient temperature, and the voltage at the output terminal TEM POWER of the power supply reverse protection circuit changes accordingly. Resistors R1 and R2 in the power supply voltage signal acquisition circuit are of the same type and have the same resistance value, which can reduce the impact of temperature drift on the acquired signal; larger resistance values ​​of R1 and R2 can reduce power consumption; and the accuracy class of R1 and R2 is higher than or equal to ±0.1%, increasing the acquisition accuracy of the power supply voltage signal acquisition circuit.

[0038] 3. This utility model discloses a temperature signal input differential circuit. In the voltage divider differential processing circuit, R3 and R4 are selected as high-precision low-temperature drift resistors of the same type. When the ambient temperature rises / falls, the resistance values ​​of R3 and R4 will increase / decrease simultaneously. Therefore, the voltage V at point A will change. A Voltage at point C V C The difference can eliminate the influence of temperature drift on components other than the temperature sensor, thereby realizing a high-precision, temperature drift-compensated temperature signal acquisition circuit. In the layout of the controller circuit PCB, the two lines from point A to the first acquisition port ADCH and from point C to the second acquisition port ADCL adopt a differential design layout. Due to the differential design of the circuit, the anti-interference performance of the temperature acquisition signal can be further improved, and common-mode rejection can also be formed.

[0039] 4. This utility model provides a temperature signal input differential circuit. The temperature sensor is an NTC, and the temperature measurement range of the voltage divider differential processing circuit is the temperature range of the NTC. Compared with ordinary temperature signal input circuits, the temperature measurement range is increased.

[0040] 5. This utility model provides a temperature signal input differential circuit, in which inductor L1, capacitors C2 and C3 form a π-type filter module to increase the circuit's anti-interference capability.

[0041] 6. This utility model discloses a temperature signal input differential circuit. When diodes D2, D3, D4, and D5 are working, the anode-cathode voltage difference is within 0.7V. By grounding and connecting to 5V, the voltage V collected at the first acquisition port ADC H and the second acquisition port ADC L can be converted. A V C The voltage is clamped between -0.7V and 5.7V to provide overvoltage protection for the voltage acquisition module port and to enable diagnostics of power supply and ground short circuits at the temperature sensor input terminal. Attached Figure Description

[0042] Figure 1 This is a power supply anti-reverse circuit diagram in an embodiment of a temperature signal input differential circuit of this utility model;

[0043] Figure 2 This is a circuit diagram of the power supply voltage signal acquisition circuit in an embodiment of the temperature signal input differential circuit of this utility model;

[0044] Figure 3 This is a circuit diagram of a voltage divider differential processing circuit in an embodiment of a temperature signal input differential circuit according to this utility model. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] This utility model discloses a temperature signal input differential circuit, including a power supply anti-reverse circuit, a power supply voltage signal acquisition circuit, and a voltage divider differential processing circuit.

[0047] like Figure 1 As shown, the reverse power supply protection circuit includes a 5V power supply and a diode D1. The positive terminal of the diode D1 is connected to the power supply, and the negative terminal serves as the output terminal TEM POWER of the reverse power supply protection circuit, which is used to power the power supply voltage signal acquisition circuit and the voltage divider differential processing circuit. The 5V power supply is the total power supply for the entire temperature signal input differential circuit. The diode D1 is used to isolate the potential of the negative terminal to prevent the high potential of the negative terminal from affecting the safety of the power supply terminal.

[0048] like Figure 2As shown, the power supply voltage signal acquisition circuit includes resistors R1 and R2 for voltage division and a filter capacitor C1. One end of resistor R1 is connected to the output terminal TEM POWER of the power supply reverse protection circuit, and the other end is connected to one end of resistor R2 at point D. The other end of resistor R2 is grounded. The filter capacitor C1 is connected in parallel with resistor R2. Resistors R1 and R2 form a voltage divider circuit, and the filter capacitor C1 is used for filtering. Resistors R1 and R2 are of the same type, with an accuracy class higher than or equal to ±0.1% and a temperature drift less than or equal to 25ppm / ℃. The resistance values ​​of resistors R1 and R2 are the same, both 30K to 50K. This can reduce the impact of temperature drift on the voltage at the third acquisition port ADCPOWER. The larger resistance values ​​of R1 and R2 can reduce power consumption. The accuracy class of R1 and R2 is higher than or equal to ±0.1%, increasing the acquisition accuracy of the power supply voltage signal acquisition circuit. The filter capacitor C1 has a capacitance of 100NF and is used to filter out noise of a certain frequency.

[0049] like Figure 3 As shown, the voltage divider differential processing circuit includes resistor R3, inductor L1, capacitors C2 and C3, a temperature sensor, resistors R4, R5, and R7, an RC filter circuit, a voltage acquisition module, and a voltage clamping circuit. The equivalent resistance of inductor L1 is in the range of 0 to 1 Ω. The voltage acquisition module is used to acquire voltage signals and send them to an external processing circuit for calculation. In other embodiments, the voltage acquisition module is an MCU, which also calculates temperature sensor data based on the acquired voltage signals.

[0050] One end of resistor R3 is connected to the output terminal TEM POWER of the power supply reverse protection circuit, and the other end is connected to one end of inductor L1 at point A. The other end of inductor L1 is connected to one end of the temperature sensor at point B, and the other end of the temperature sensor is connected to one end of resistor R4 at point C. The other end of resistor R4 is grounded. To improve the accuracy of NTC voltage divider acquisition, resistors R3 and R4 are of the same type, with an accuracy class greater than or equal to ±0.1%, a temperature drift less than or equal to 25ppm / ℃, and a resistance value less than 1kΩ.

[0051] In this embodiment, the temperature sensor uses an NTC type thermistor with a resistance of 10kΩ at 25℃ and an operating temperature range of -40℃ to 150℃. The resistance of the temperature sensor decreases as the ambient temperature increases, which helps improve the acquisition resolution of the voltage acquisition module. The NTC can be placed in the environment where temperature needs to be acquired, such as oil, water, or air, via connectors, wiring harnesses, etc. In other embodiments, a PTC type temperature sensor can also be used as needed.

[0052] Inductor L1, capacitors C2 and C3 form a π-type filter module to increase the circuit's anti-interference capability. Specifically, one end of capacitor C2 is connected to one end of inductor L1, and the other end is grounded; one end of capacitor C3 is connected to the other end of inductor L1, and the other end is grounded.

[0053] One end of resistor R5 is connected to point A, and one end of resistor R7 is connected to point C. Resistors R5 and R7 have the same resistance value.

[0054] The RC filter circuit includes resistors R6 and R8, and capacitors C4 and C5. One end of resistor R6 is connected to the other end of resistor R5, and the other end of resistor R6 is simultaneously connected to the first acquisition port ADC H of the voltage acquisition module and one end of capacitor C4. The other end of capacitor C4 is grounded, forming one RC filter circuit. One end of resistor R8 is connected to the other end of resistor R7, and the other end of resistor R8 is simultaneously connected to the second acquisition port ADC L of the voltage acquisition module and one end of capacitor C5. The other end of capacitor C5 is grounded, forming another RC filter circuit. Resistors R6 and R8 have the same resistance value. The sum of the resistance values ​​of resistors R5 and R6 is greater than 10kΩ and less than 40kΩ; the sum of the resistance values ​​of resistors R7 and R8 is greater than 10kΩ and less than 40kΩ.

[0055] The third acquisition port ADC POWER of the voltage acquisition module is connected to point D and is used to acquire the voltage signal at point D.

[0056] The voltage clamping circuit includes diodes D2, D3, D4, and D5; the positive terminals of diodes D2 and D4 are grounded, and their negative terminals are connected to the positive terminals of diodes D3 and D5, respectively. The negative terminals of diodes D3 and D5 are connected to a 5V power supply; the negative terminals of diodes D2 and D4 are also connected to the other ends of resistors R5 and R7, respectively.

[0057] When the NTC temperature sensor is short-circuited to ground or power supply at both ends, the voltage clamping circuit performs clamping and diagnostic functions. When point B is short-circuited to power supply / ground, the fault can be determined and troubleshooted based on the voltage collected by the first acquisition port ADC H. When point C is short-circuited to power supply / ground, the fault can be determined and troubleshooted based on the voltage collected by the second acquisition port ADC L.

[0058] Circuit working principle:

[0059] The total voltage output of the power supply anti-reverse circuit at the TEM POWER terminal is V. 总 The voltage signal at point D acquired by the third acquisition port ADC POWER of the voltage acquisition module is V. D According to Figure 2 Calculate V 总 for:

[0060] V 总 =VD ×(R1+R2) / R2;

[0061] Since the equivalent series resistance of inductor L1 is small, the voltage across inductor L1 can be ignored. The voltage from point A to point C is V. AC The voltage from point B to point C is V. BC V AC It can be regarded as V BC When the resistance of the NTC changes with ambient temperature (oil temperature, water temperature, air temperature, etc.), it can be determined by the voltage V at point A. A Voltage at point C V C The voltage value V across the NTC is obtained by calculating the difference. NTC ,Right now:

[0062] V NTC =V A -V C ;

[0063] Based on the voltage value V across the NTC NTC The resistance R of the NTC can be obtained from the calculation. NTC This allows us to obtain the ambient temperature that needs to be collected. NTC With R NTC The relation is:

[0064] V NTC =V 总 ×R NTC / (R3+R NTC +R4);

[0065] When the ambient temperature rises or falls, because R3 and R4 are high-precision, low-temperature-drift resistors of the same type, their resistance values ​​will increase or decrease simultaneously. Therefore, the voltage V at point A will decrease. A Voltage at point C V C The difference can eliminate the impact of temperature drift on components other than the NTC. In the PCB layout of the controller circuit, the two lines from point A to the first acquisition port ADC H and from point C to the second acquisition port ADC L adopt a differential design layout. Due to the differential design of the circuit, the anti-interference performance of the temperature acquisition signal can be further improved, and common-mode rejection can also be formed. Thus, a high-precision, temperature drift-compensated, common-mode-suppressed, anti-interference-capable, fault-diagnostic, simple-structured, and low-cost temperature signal acquisition circuit is realized.

[0066] In the voltage divider differential processing circuit, the temperature measurement range is the same as the temperature range of the NTC, which increases the temperature measurement range compared to ordinary temperature signal input circuits.

Claims

1. A temperature signal input differential circuit, characterized in that: This includes a power supply anti-reverse circuit, a power supply voltage signal acquisition circuit, and a voltage divider differential processing circuit; The power supply anti-reverse circuit is used to supply power to the power supply voltage signal acquisition circuit and the voltage divider differential processing circuit. The power supply voltage signal acquisition circuit includes resistors R1 and R2 for voltage division, and a filter capacitor C1; one end of resistor R1 is connected to the output terminal TEM POWER of the power supply anti-reverse circuit, and the other end is connected to one end of resistor R2 at point D; the other end of resistor R2 is grounded; the filter capacitor C1 is connected in parallel with resistor R2. The voltage divider differential processing circuit includes a temperature sensor installed on the target under test, resistors R3, R4, R5, and R7, and a voltage acquisition module. One end of resistor R3 is connected to the output terminal TEM POWER of the power supply circuit, and the other end is connected to one end of the temperature sensor at point A. The other end of the temperature sensor is connected to one end of resistor R4 at point C, and the other end of resistor R4 is grounded. The voltage acquisition module is used to acquire voltage signals and send the voltage signals to an external processing circuit for calculation. One end of the resistor R5 is connected to point A, and the other end is connected to the first acquisition port ADC H of the voltage acquisition module; the first acquisition port ADC H is used to acquire the voltage signal at point A. One end of resistor R7 is connected to point C, and the other end is connected to the second acquisition port ADC L of the voltage acquisition module; the second acquisition port ADC L is used to acquire the voltage signal at point C. The third acquisition port ADC POWER of the voltage acquisition module is connected to point D and is used to acquire the voltage signal at point D.

2. The temperature signal input differential circuit according to claim 1, characterized in that: The voltage divider differential processing circuit also includes inductor L1 and capacitors C2 and C3; One end of the inductor L1 is connected to point A, and the other end is connected to one end of the temperature sensor at point B. The equivalent resistance of the inductor L1 is 0 to 1 Ω. The capacitors C2 and C3, together with the inductor L1, form a π-type filter module.

3. The temperature signal input differential circuit according to claim 1, characterized in that: The voltage divider differential processing circuit also includes a voltage clamping circuit, which includes diodes D2, D3, D4, and D5. The positive terminals of diodes D2 and D4 are grounded, and their negative terminals are connected to the positive terminals of diodes D3 and D5, respectively. The negative terminals of diodes D3 and D5 are connected to a 5V power supply. The negative terminals of diodes D2 and D4 are also connected to the other ends of resistors R5 and R7, respectively.

4. The temperature signal input differential circuit according to claim 1, characterized in that: The voltage divider differential processing circuit also includes an RC filter circuit, which includes resistors R6 and R8, and capacitors C4 and C5. One end of resistor R6 is connected to the other end of resistor R5. The other end of resistor R6 is simultaneously connected to the first acquisition port ADC H of the voltage acquisition module and one end of capacitor C4. The other end of capacitor C4 is grounded, forming an RC filter circuit. One end of resistor R8 is connected to the other end of resistor R7. The other end of resistor R8 is connected to the second acquisition port ADC L of the voltage acquisition module and one end of capacitor C5. The other end of capacitor C5 is grounded, forming another RC filter circuit.

5. A temperature signal input differential circuit according to any one of claims 1-4, characterized in that: The temperature sensor is an NTC sensor with a resistance of 10kΩ at 25℃ and an operating temperature range of -40℃ to 150℃. The resistance of the temperature sensor decreases as the ambient temperature increases.

6. A temperature signal input differential circuit according to claim 1, characterized in that: The resistors R3 and R4 are of the same type, with an accuracy class of ±0.1% or higher, a temperature drift of less than or equal to 25ppm / ℃, and a resistance value of less than 1kΩ.

7. A temperature signal input differential circuit according to claim 1, characterized in that: The resistors R1 and R2 are of the same type, and the accuracy class of resistors R1 and R2 is higher than or equal to ±0.1%, and the temperature drift is less than or equal to 25ppm / ℃. Resistors R1 and R2 have the same resistance value, both ranging from 30K to 50K. The capacitance of the filter capacitor C1 is 100NF.

8. A temperature signal input differential circuit according to claim 1, characterized in that: The reverse power supply circuit includes a 5V power supply and a diode D1; the positive terminal of the diode D1 is connected to the power supply, and the negative terminal serves as the output terminal TEM POWER of the reverse power supply circuit.

9. A temperature signal input differential circuit according to claim 4, characterized in that: The sum of the resistance values ​​of resistors R5 and R6 is greater than 10kΩ and less than 40kΩ; The sum of the resistance values ​​of resistors R7 and R8 is greater than 10kΩ and less than 40kΩ; The resistors R5 and R7 have the same resistance value, and the resistors R6 and R8 have the same resistance value.

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