Analog input detection circuit with circuit breaking detection function

Abstract

The utility model discloses a kind of analog input detection circuit with circuit-breaker detection function, characteristics include power module, second resistance, third resistance, voltage follower and signal conditioning module;Signal conditioning module includes seventh resistance, eighth resistance, ninth resistance, tenth resistance, second operational amplifier, eleventh resistance and second capacitor;Advantages are by second operational amplifier, seventh resistance, eighth resistance, ninth resistance and tenth resistance constitute direct current bias inverter amplifier, external input signal is obtained an output voltage after in turn through voltage follower and direct current bias inverter amplifier, according to this DSP chip determines whether external input is abnormal, not only improve the reliability of detection system, but also improve fault diagnosis capability.

Description

Technical Field

[0001] This utility model relates to a detection circuit, and more particularly to an analog input detection circuit with open circuit detection function. Background Technology

[0002] In modern industrial automation, power monitoring, instrumentation, and IoT devices, analog input detection circuits are the core component for acquiring sensor signals (such as temperature, pressure, current, and voltage). However, in practical applications, signal line breaks often occur due to sensor damage, aging wiring, or loose connectors, leading to misreading of "zero signal" or "fixed level" by the system, which in turn causes control misjudgments or safety hazards. Therefore, designing an analog input detection circuit with integrated "open-circuit detection function" is of great significance for improving system reliability and fault diagnosis capabilities. Summary of the Invention

[0003] The technical problem to be solved by this utility model is to provide an analog input detection circuit with open circuit detection function, which not only improves the reliability of the detection system, but also improves the fault diagnosis capability.

[0004] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: an analog input detection circuit with open circuit detection function, including a power supply module, a second resistor, a third resistor, a voltage follower and a signal conditioning module;

[0005] The power supply module has a working negative voltage output terminal and a detection voltage output terminal. The signal conditioning module includes a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a second operational amplifier, an eleventh resistor, and a second capacitor. One end of the second resistor, one end of the third resistor, and the input terminal of the voltage follower are connected to an external input signal. The other end of the second resistor is connected to the working negative voltage output terminal. One end of the seventh resistor is connected to the output terminal of the voltage follower. The other end of the seventh resistor and one end of the eighth resistor are connected to the inverting input terminal of the second operational amplifier. One end of the ninth resistor is connected to the detection voltage output terminal. The other end of the ninth resistor and one end of the tenth resistor are connected to the non-inverting input terminal of the second operational amplifier. The other end of the eighth resistor, the output terminal of the second operational amplifier, and one end of the eleventh resistor are connected. The other end of the eleventh resistor is connected to one end of the second capacitor and serves as the output terminal of the signal conditioning module. The output terminal of the signal conditioning module is used to connect to the detection terminal of the DSP chip. The other ends of the third resistor, the tenth resistor, and the second capacitor are all grounded.

[0006] Compared with the prior art, the advantages of this utility model are that the second operational amplifier, the seventh resistor, the eighth resistor, the ninth resistor, and the tenth resistor constitute a DC biased inverting amplifier, which is used to invert and amplify the input signal. When the voltage at the output terminal of the signal conditioning module detected by the DSP chip is always less than the detection voltage, it is determined that the analog input is normal and fault-free. When the external input signal is a zero-level signal, the voltage at the input terminal is approximately zero. The DSP chip detects that the voltage at the output terminal of the signal conditioning module is equal to the detection voltage, and determines that the analog input is zero. When an external signal line is open-circuited, due to the voltage division effect of the seventh and tenth resistors, a negative voltage relative to ground is generated at the input terminal of the voltage follower. In this fault mode, the DSP chip detects that the voltage at the output terminal of the signal conditioning module is greater than the detection voltage, thereby determining that the external input is abnormal and ensuring that the fault can be identified. The voltage follower is used to isolate the preceding and following stage circuits. The output signal is basically equivalent to the input signal, but the load-carrying capacity is improved.

[0007] Furthermore, the voltage follower includes a fourth resistor, a fifth resistor, a first capacitor, a sixth resistor, and a first operational amplifier. One end of the fourth resistor is connected to an external input signal, and the other end of the fourth resistor is connected to one end of the fifth resistor. The other end of the fifth resistor and one end of the first capacitor are connected to the non-inverting input of the first operational amplifier. The inverting input of the first operational amplifier is connected to one end of the sixth resistor. The other end of the sixth resistor is connected to the output of the first operational amplifier and serves as the output of the voltage follower. The other end of the first capacitor is grounded. The voltage follower can achieve a buffering effect of high input impedance and low output impedance, effectively isolating the preceding and following circuits. The first capacitor acts as a filter, thereby suppressing noise interference.

[0008] Furthermore, it also includes an analog signal type switching circuit, which includes a header with pins 1 and 2 and a first resistor. Pin 2 is connected to an external input signal, pin 1 is connected to one end of the first resistor, and the other end of the first resistor is grounded. Through the physical shorting operation of the header and the synergistic effect of the grounding path of the first resistor, low-cost and reliable switching between current and voltage input modes is achieved. Therefore, it can be widely used in the acquisition and processing of voltage-type (e.g., 0-10V) and current-type (e.g., 0-20mA) signals. Attached Figure Description

[0009] Figure 1 This is a circuit diagram of the present invention. Detailed Implementation

[0010] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0011] Example 1: As Figure 1 As shown, an analog input detection circuit with open circuit detection function includes a power supply module (not shown), a second resistor R2, a third resistor R3, a voltage follower, and a signal conditioning module.

[0012] The power supply module has a negative operating voltage output terminal (-15V) and a detection voltage output terminal (+1.5V). The voltage follower includes a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a sixth resistor R6, and a first operational amplifier U1. The signal conditioning module includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a second operational amplifier U2, an eleventh resistor R11, and a second capacitor C2. One end of the second resistor R2, one end of the third resistor R3, and one end of the fourth resistor R4 are connected to the external input signal (ANIN). The other end of the second resistor R2 is connected to the negative operating voltage output terminal. The other end of the fourth resistor R4 is connected to one end of the fifth resistor R5. The other end of the fifth resistor R5 and one end of the first capacitor C1 are connected to the non-inverting input terminal of the first operational amplifier U1. The inverting input terminal of the first operational amplifier U1 is connected to the sixth resistor R6. One end of the first operational amplifier U1 is connected to the second operational amplifier U2. The other end of the sixth resistor R6 and the output of the first operational amplifier U1 are connected to one end of the seventh resistor R7. The other end of the seventh resistor R7 and one end of the eighth resistor R8 are connected to the inverting input of the second operational amplifier U2. One end of the ninth resistor R9 is connected to the detection voltage output. The other end of the ninth resistor R9 and one end of the tenth resistor R10 are connected to the non-inverting input of the second operational amplifier U2. The other end of the eighth resistor R8 and the output of the second operational amplifier U2 are connected to one end of the eleventh resistor R11. The other end of the eleventh resistor R11 is connected to one end of the second capacitor C2 and serves as the output of the signal conditioning module (AI). The output of the signal conditioning module is used to connect to the detection terminal of the DSP chip. The other ends of the third resistor R3, the first capacitor C1, the tenth resistor R10, and the second capacitor C2 are all grounded.

[0013] The working principle of this embodiment is as follows:

[0014] 1) The core processing unit of the analog input detection circuit consists of two operational amplifier circuits:

[0015] 1. A voltage follower is formed by the first operational amplifier U1 (model TPA2674-TS2R), the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, and the first capacitor C1. This provides a buffer for high input impedance and low output impedance, effectively isolating the preceding and following circuits. The first capacitor C1 acts as a filter, thereby suppressing noise interference.

[0016] 2. A DC biased inverting amplifier is constructed using the second operational amplifier U2 (model TPA2674-TS2R), the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10. It performs two functions: first, it inverts and amplifies the input signal (the amplification factor is determined by the relevant resistors); second, it introduces a specific DC bias voltage to adjust the processed signal to the appropriate detection range of the DSP chip.

[0017] 2) The processing and fault detection mechanism for analog input signals is as follows:

[0018] 1. In normal input mode:

[0019] When the external input signal AN1N is a voltage signal V in At that time, the voltage signal V in After passing through a voltage follower and a DC-biased inverting amplifier in sequence, and with the amplification factor adjusted, the output voltage V o Set the resistance of the fourth resistor R4 to 15KΩ, the fifth resistor R5 to 15KΩ, the sixth resistor R6 to 30KΩ, the seventh resistor R7 to 30KΩ, the eighth resistor R8 to 3.9KΩ, the ninth resistor R9 to 3.9KΩ, and the tenth resistor R10 to 30KΩ. o =1.5-V in ×1.3 / 10, when the DSP chip detects V o If the voltage is consistently lower than the detection voltage, the analog input is considered normal and fault-free. The detection voltage is set to 1.5V.

[0020] 2. Zero-input mode:

[0021] When the external input signal ANIN is a zero-level signal, the voltage at the input terminal is approximately 0V. After the input signal passes through a voltage follower and a DC bias inverting amplifier in sequence, the DSP chip detects a voltage equal to the detection voltage and determines that the analog input is zero. The detection voltage is set to 1.5V.

[0022] 3. In circuit breaker mode:

[0023] When an external signal line is open-circuited, the voltage divider formed by resistors R7 (seventh resistor) and R10 at the input of the DC-biased inverting amplifier will generate a negative voltage relative to ground at the input of the voltage follower. This negative voltage passes through the voltage follower and the DC-biased inverting amplifier in sequence. After adjusting the amplification factor, the output voltage is V. o =1.5-V in×1.3 / 10, in this fault mode, the DSP chip always detects a voltage greater than the detection voltage, thereby determining that the external input is abnormal and ensuring that the fault can be identified. The detection voltage is set to 1.5V.

[0024] Example 2: The rest is the same as in Example 1, except that it also includes an analog signal type switching circuit composed of pin header P and first resistor R1. Pin header P has pin 1 and pin 2. Pin 2 of pin header P is connected to the external input signal, pin 1 of pin header P is connected to one end of the first resistor R1, and the other end of the first resistor R1 is grounded.

[0025] The working principle of this embodiment is as follows:

[0026] In normal input mode:

[0027] When the external input signal ANIN is a current signal I, the pin header P is short-circuited. The current signal I passes through the first resistor R1 (249Ω), and according to Ohm's law, a voltage signal V proportional to the input current is generated across it. R1 =I×R1, voltage signal V R1 After passing through a voltage follower and a DC-biased inverting amplifier in sequence, and with the amplification factor adjusted, the output voltage is V. o =1.5-V R1 ×1.3 / 10, when the DSP chip detects V o If the voltage is consistently lower than the detection voltage, the analog input is considered normal and fault-free. The detection voltage is set to 1.5V.

Claims

1. An analog input detection circuit with open circuit detection function, characterized in that... Includes a power supply module, a second resistor, a third resistor, a voltage follower, and a signal conditioning module; The power supply module has a working negative voltage output terminal and a detection voltage output terminal. The signal conditioning module includes a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a second operational amplifier, an eleventh resistor, and a second capacitor. One end of the second resistor, one end of the third resistor, and the input terminal of the voltage follower are connected to an external input signal. The other end of the second resistor is connected to the working negative voltage output terminal. One end of the seventh resistor is connected to the output terminal of the voltage follower. The other end of the seventh resistor and one end of the eighth resistor are connected to the inverting input terminal of the second operational amplifier. One end of the ninth resistor is connected to the detection voltage output terminal. The other end of the ninth resistor and one end of the tenth resistor are connected to the non-inverting input terminal of the second operational amplifier. The other end of the eighth resistor, the output terminal of the second operational amplifier, and one end of the eleventh resistor are connected. The other end of the eleventh resistor is connected to one end of the second capacitor and serves as the output terminal of the signal conditioning module. The output terminal of the signal conditioning module is used to connect to the detection terminal of the DSP chip. The other ends of the third resistor, the tenth resistor, and the second capacitor are respectively grounded.

2. The analog input detection circuit with open circuit detection function according to claim 1, characterized in that... The voltage follower includes a fourth resistor, a fifth resistor, a first capacitor, a sixth resistor, and a first operational amplifier. One end of the fourth resistor is connected to an external input signal, and the other end of the fourth resistor is connected to one end of the fifth resistor. The other end of the fifth resistor and one end of the first capacitor are connected to the non-inverting input of the first operational amplifier. The inverting input of the first operational amplifier is connected to one end of the sixth resistor. The other end of the sixth resistor is connected to the output of the first operational amplifier and serves as the output of the voltage follower. The other end of the first capacitor is grounded.

3. The analog input detection circuit with open circuit detection function according to claim 1, characterized in that... It also includes an analog signal type switching circuit, which includes a pin header with pins 1 and 2 and a first resistor. Pin 2 is connected to an external input signal, pin 1 is connected to one end of the first resistor, and the other end of the first resistor is grounded.

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