Broken line detection circuit based on analog input signal

Abstract

A broken line detection circuit based on an analog input signal relates to the technical field of electronics and comprises a signal receiving unit, a broken line detection unit, a voltage comparison unit, an AD acquisition unit, a reference isolation power supply and a control unit. A first loop input pin of the signal receiving unit is electrically connected with the broken line detection unit, and a first loop output pin of the signal receiving unit is electrically connected with the voltage comparison unit; a second loop input pin of the signal receiving unit is electrically connected with an external input wire, and a second loop output pin of the signal receiving unit is electrically connected with the AD acquisition unit; a signal input pin of the broken line detection unit is electrically connected with an external input wiring, and a power supply input pin of the broken line detection unit is electrically connected with a reference isolation power supply; the voltage comparison unit is electrically connected with the control unit through the digital isolation unit; the AD acquisition unit is electrically connected with the control unit through the communication isolation unit; the circuit has the advantages of being accurate in detection result and capable of identifying the wire breakage condition.

Description

Technical Field

[0001] The invention relates to the field of electronic technology, and in particular to a disconnection detection circuit based on analog input signals. Background Art

[0002] In industrial control equipment, analog signals are generally used as the input of the equipment to support the transmission of related status and control signals, which plays a vital role in the normal operation of the system. Analog signals are generally collected and converted using analog input boards.

[0003] Since industrial control equipment often experiences vibration and impact in application scenarios, which may cause the external wiring of the equipment to loosen, have poor contact or fall off, the industrial control equipment is easily disturbed by the site when the line is disconnected and collects abnormal values, thus affecting the quality of the overall collected data.

[0004] In addition, traditional analog quantity acquisition is generally directly implemented using an AD sampling circuit. However, this sampling circuit only processes the collected analog quantity signal and cannot make an effective judgment on whether the industrial control equipment is disconnected. Therefore, it cannot avoid collecting abnormal values ​​that jump;

[0005] Therefore, we propose a circuit that has accurate detection results and can also identify line breakage. Summary of the invention

[0006] In order to overcome the deficiencies in the background technology, the present invention discloses a disconnection detection circuit based on an analog input signal.

[0007] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0008] A disconnection detection circuit based on analog input signals, comprising a signal receiving unit, a disconnection detection unit, a voltage comparison unit, an AD acquisition unit, a reference isolation power supply and a control unit;

[0009] The first loop input pin of the signal receiving unit is electrically connected to the disconnection detection unit, and the first loop output pin of the signal receiving unit is electrically connected to the voltage comparison unit; the second loop input pin of the signal receiving unit is electrically connected to the external input wiring, and the second loop output pin of the signal receiving unit is electrically connected to the AD acquisition unit;

[0010] The signal input pin of the disconnection detection unit is electrically connected to the external input wiring, and the power input pin of the disconnection detection unit is electrically connected to the reference isolation power supply;

[0011] The voltage comparison unit is electrically connected to the control unit via the digital isolation unit;

[0012] The AD acquisition unit is electrically connected to the control unit via the communication isolation unit.

[0013] Preferably, the reference isolated power supply is used to receive an external power supply and generate ±12Vviso power supplies, wherein the +12Vviso voltage is used as a positive voltage for the disconnection detection unit to operate, and the -12Vviso voltage is used as a reference detection voltage for the disconnection detection unit.

[0014] Preferably, the reference isolated power supply comprises an isolation chip, a filter circuit and a voltage stabilization circuit, wherein the filter circuit is used to filter out noise of the external power supply;

[0015] The isolation chip is used to convert the filtered power supply into a ±12Vviso power supply;

[0016] The voltage stabilizing circuit is used to stabilize the +12Vviso power supply and the -12Vviso reference power supply, and then outputs them to the disconnection detection unit.

[0017] Preferably, the filtering circuit includes a filter inductor L1, a filter capacitor C1 and a filter capacitor C2, wherein the +24VDC of the external power supply is electrically connected to the isolation chip through the filter inductor L1, and filter capacitors C1 and C2 are respectively connected in parallel at both ends of the filter inductor L1, and both filter capacitors C1 and C2 are grounded.

[0018] Preferably, the voltage stabilizing circuit includes a voltage stabilizing inductor L1, a voltage stabilizing capacitor C1, a voltage stabilizing inductor L2 and a voltage stabilizing capacitor C2, wherein the voltage stabilizing inductor L1 is electrically connected to the isolation chip and the +12Vviso power supply, respectively, and the voltage stabilizing capacitor C1 is connected in parallel between the voltage stabilizing inductor L1 and the +12Vviso power supply; the voltage stabilizing inductor L2 is electrically connected to the isolation chip and the -12Vviso reference power supply, respectively, and the voltage stabilizing capacitor C2 is connected in parallel between the voltage stabilizing inductor L2 and the -12Vviso reference power supply; the voltage stabilizing capacitor C1 and the voltage stabilizing capacitor C2 are both grounded.

[0019] Preferably, the disconnection detection unit includes a pull-up resistor R6, a resistor R7, a voltage comparator U2B and an equivalent resistor R8, wherein both ends of the resistor R7 are electrically connected to the voltage signal of the external input wiring and the in-phase input pin of the voltage comparator U2B respectively, and a pull-up resistor R6 is connected in parallel between the resistor R7 and the voltage signal of the external input wiring, and the pull-up resistor R6 is electrically connected to the -12Vviso reference power supply;

[0020] The output pin of the voltage comparator U2B is electrically connected to the first loop input pin of the signal receiving unit, and the inverting input pin of the voltage comparator U2B is electrically connected to the output pin of the voltage comparator U2B through an equivalent resistor R8.

[0021] Preferably, a protection diode D1 is connected in parallel between the resistor R7 and the voltage signal of the external input connection, and the protection diode D1 is grounded.

[0022] Preferably, the voltage comparison unit includes a voltage-dividing resistor R1, a voltage-dividing resistor R2 and a voltage comparator U1B, wherein the non-inverting input terminal of the voltage comparator U1B is electrically connected to the first loop output pin of the signal receiving unit, and the inverting input terminal of the voltage comparator U1B is electrically connected to the voltage-dividing resistor R1 and the voltage-dividing resistor R2 respectively, wherein the voltage-dividing resistor R1 is grounded, and the voltage-dividing resistor R2 is electrically connected to a -12Vviso reference power supply;

[0023] The output pin of the voltage comparator U1B is electrically connected to the digital isolation unit.

[0024] Preferably, a voltage-dividing resistor R4 is connected in parallel between the output pin of the voltage comparator U1B and the digital isolation unit, and a voltage-dividing resistor R5 is connected in series, and the voltage-dividing resistor R4 is electrically connected to an external +5Vviso power supply.

[0025] Preferably, a diode D2 is connected in parallel between the output pin of the voltage comparator U1B and the digital isolation unit, and the diode D2 is grounded.

[0026] Due to the adoption of the above-mentioned technical solution, the present invention has the following beneficial effects:

[0027] The present invention discloses a disconnection detection circuit based on analog input signals, which can realize disconnection detection and signal collection in parallel through a signal receiving unit, so as to achieve data collection without packet loss and ensure accurate detection results;

[0028] In addition, through the digital isolation unit and the communication isolation unit, the disconnection detection result and the signal acquisition result can be isolated, ensuring that the disconnection detection signal and the acquisition signal received by the control unit are independent of each other, avoiding interference between the signals;

[0029] In addition, the cooperation between the voltage comparison unit and the line break detection unit can realize real-time detection of line break conditions, further ensuring the accuracy of the line break detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A structural schematic diagram of the present invention;

[0031] Figure 2 It is a structural diagram of the reference isolation power supply;

[0032] Figure 3 It is a structural schematic diagram of a line break detection unit;

[0033] Figure 4 Schematic diagram of the structure of the voltage comparison unit.

[0034] In the figure: 1. Signal receiving unit; 2. Line break detection unit; 3. Voltage comparison unit; 4. AD acquisition unit; 5. Reference isolation power supply; 6. Digital isolation unit; 7. Communication isolation unit; 8. Control unit; 9. External input wiring. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be described below in conjunction with the drawings in the embodiments of the present invention. In the description, it should be understood that if there are terms such as "upper", "lower", "front", "back", "left", "right" and the like indicating directions or positional relationships, they are only corresponding to the drawings of the present invention, for the convenience of describing the present invention, and do not indicate or imply that the devices or components referred to must have a specific direction:

[0036] Embodiment 1 is:

[0037] Combined with Figure 1 The disconnection detection circuit based on analog input signal comprises a signal receiving unit 1, a disconnection detection unit 2, a voltage comparison unit 3, an AD acquisition unit 4, a reference isolation power supply 5 and a control unit 8;

[0038] The first loop input pin of the signal receiving unit 1 is electrically connected to the disconnection detection unit 2, and the first loop output pin of the signal receiving unit 1 is electrically connected to the voltage comparison unit 3; the second loop input pin of the signal receiving unit 1 is electrically connected to the external input wiring 9, and the second loop output pin of the signal receiving unit 1 is electrically connected to the AD acquisition unit 4;

[0039] The signal receiving unit 1 is a two-way connector, and the first circuit and the second circuit inside it are two independent signal transmission circuits that do not interfere with each other; therefore, the signal receiving unit 1 can simultaneously receive the line break detection signal and the external input signal, and then transmit the two signals to the voltage comparison unit 3 and the AD acquisition unit 4 respectively, so as to realize the parallel of line break detection and signal acquisition, that is, the line break detection is performed while the signal is being acquired. If the control unit 8 receives a signal confirming that a line break has occurred, the signal acquired when the line break occurs can be removed in time, thereby ensuring that there are no abnormal values ​​in the real-time acquired signal, thereby improving the acquired signal quality.

[0040] The signal input pin of the disconnection detection unit 2 is electrically connected to the external input wiring 9, and the power input pin of the disconnection detection unit 2 is electrically connected to the reference isolation power supply 5; the disconnection detection unit 2 determines whether a disconnection occurs by comparing the reference isolation voltage and the external input signal, and since the judgment process is processed in real time and continuously, the accuracy of the disconnection detection result can be further ensured.

[0041] The voltage comparison unit 3 is electrically connected to the control unit 8 via the digital isolation unit 6;

[0042] The AD acquisition unit 4 is electrically connected to the control unit 8 via the communication isolation unit 7;

[0043] Through the digital isolation unit 6 and the communication isolation unit 7, isolation between the line break detection result and the signal acquisition result can be achieved, ensuring that the line break detection signal and the acquisition signal received by the control unit 8 are independent of each other, avoiding interference between the signals, and also to ensure the accuracy of the line break detection signal and the acquisition signal obtained by the control unit 8.

[0044] Embodiment 2 is:

[0045] Based on Example 1, Figure 2 , further defining the reference isolated power supply 5, the reference isolated power supply 5 is used to receive an external power supply and generate a ±12Vviso power supply, wherein the +12Vviso voltage is used as a positive voltage for the disconnection detection unit 2 to work, and the -12Vviso voltage is used as a reference detection voltage for the disconnection detection unit 2;

[0046] It should be noted that the ±12Vviso power supply also provides power to the disconnection detection unit 2 and the voltage comparison unit 3 .

[0047] In addition, the reference isolation power supply 5 includes an isolation chip, a filter circuit and a voltage stabilization circuit, and the filter circuit is used to filter out the noise of the external power supply;

[0048] The isolation chip is used to convert the filtered power supply into a ±12Vviso power supply;

[0049] The voltage stabilizing circuit is used to stabilize the +12Vviso power supply and the -12Vviso reference power supply, and then outputs them to the disconnection detection unit 2 .

[0050] According to the needs, the filtering circuit includes a filtering inductor L1, a filtering capacitor C1 and a filtering capacitor C2, wherein the +24VDC of the external power supply is electrically connected to the isolation chip through the filtering inductor L1, and the two ends of the filtering inductor L1 are respectively connected in parallel with the filtering capacitor C1 and the filtering capacitor C2, and the filtering capacitor C1 and the filtering capacitor C2 are both grounded;

[0051] It should be noted that the filter circuit is used to filter out power supply noise to ensure that the output ±12Vviso power supply is more stable and clean, where inductor L1 is used to prevent high-frequency noise from passing through, while capacitors C1 and C2 are used to absorb the noise, thereby making the output voltage purer.

[0052] In addition, the voltage stabilizing circuit includes a voltage stabilizing inductor L1, a voltage stabilizing capacitor C1, a voltage stabilizing inductor L2 and a voltage stabilizing capacitor C2, wherein the voltage stabilizing inductor L1 is electrically connected to the isolation chip and the +12Vviso power supply respectively, and the voltage stabilizing capacitor C1 is connected in parallel between the voltage stabilizing inductor L1 and the +12Vviso power supply; the voltage stabilizing inductor L2 is electrically connected to the isolation chip and the -12Vviso reference power supply respectively, and the voltage stabilizing capacitor C2 is connected in parallel between the voltage stabilizing inductor L2 and the -12Vviso reference power supply; the voltage stabilizing capacitor C1 and the voltage stabilizing capacitor C2 are both grounded;

[0053] The voltage stabilizing circuit can make the output +12Vviso power supply and -12Vviso reference power supply more stable, thereby facilitating the provision of a stable reference power supply during subsequent disconnection detection.

[0054] Embodiment 3 is:

[0055] Based on Example 1, Figure 3 , the disconnection detection unit 2 is further limited, that is, the disconnection detection unit 2 includes a pull-up resistor R6, a resistor R7, a voltage comparator U2B and an equivalent resistor R8, wherein both ends of the resistor R7 are electrically connected to the voltage signal of the external input wiring 9 and the in-phase input pin of the voltage comparator U2B respectively, and a pull-up resistor R6 is connected in parallel between the resistor R7 and the voltage signal of the external input wiring 9, and the pull-up resistor R6 is electrically connected to a -12Vviso reference power supply;

[0056] The output pin of the voltage comparator U2B is electrically connected to the first loop input pin of the signal receiving unit 1, and the inverting input pin of the voltage comparator U2B is electrically connected to the output pin of the voltage comparator U2B through an equivalent resistor R8;

[0057] As a specific embodiment: pull down Input+ to -12Vviso through the pull-up resistor R6 to implement the line break detection unit and generate the line break detection signal Break_Detect; and put the line break detection signal point at the front end of the filter of the analog acquisition circuit to help reduce the interference of the acquisition circuit.

[0058] In addition, when the external connection is disconnected, Input+ is provided by -12Vviso, and Break_Detect is locked to -12V; when there is an external signal, the external signal is provided by a voltage source U with an output of 0-5V. Since the impedance of the op amp input is infinite, the R7 loop is equivalent to an open circuit, and the resistor R6 and the power supply -12Vviso are equivalent to the load RL of the external voltage source. Then the voltage value of Input+ is equal to the external signal voltage value, so the obtained Break_Detect≥0V.

[0059] In particular, a protection diode D1 is connected in parallel between the resistor R7 and the voltage signal of the external input connection 9, and the protection diode D1 is grounded; the role of the protection diode D1 in this circuit is to protect other circuit components from the influence of reverse current or overvoltage. In the circuit of the disconnection detection unit, the specific role of D1 can be inferred based on common circuit design;

[0060] In addition, in general, the functions of diode D1 can include:

[0061] Protection circuit: Prevent reverse current from entering sensitive circuit parts, such as preventing current backflow when the power supply is reversed, protecting the subsequent circuit from damage.

[0062] Clamping function: Ensure that the voltage in the circuit does not exceed a certain threshold to prevent excessive voltage from damaging the circuit.

[0063] Rectification: If there is an AC component in the circuit, the diode can be used to rectify it to ensure that only current flows in one direction.

[0064] According to the context, in the wire break detection unit, the specific function of D1 is to prevent the influence of overvoltage, pulse spike voltage, or static electricity, ensuring that other parts of the circuit will not be affected by unexpected voltage during the wire break detection process.

[0065] Embodiment 4 is:

[0066] Based on Example 1, Figure 4 , further defining the voltage comparison unit 3, that is, the voltage comparison unit 3 includes a voltage-dividing resistor R1, a voltage-dividing resistor R2 and a voltage comparator U1B, wherein the non-inverting input terminal of the voltage comparator U1B is electrically connected to the first loop output pin of the signal receiving unit 1, and the inverting input terminal of the voltage comparator U1B is electrically connected to the voltage-dividing resistor R1 and the voltage-dividing resistor R2 respectively, wherein the voltage-dividing resistor R1 is grounded, and the voltage-dividing resistor R2 is electrically connected to a -12Vviso reference power supply;

[0067] The output pin of the voltage comparator U1B is electrically connected to the digital isolation unit 6;

[0068] The voltage comparator U1B with open-drain output is used to realize the disconnection state judgment. The voltage is divided by R1 and R2 to generate a -1V voltage; -1V is compared with the voltage on Break_Detect. When the input is in a disconnection state, the disconnection detection signal -12Vviso generates a Break_Detect signal after passing through the voltage follower, so Break_Detect is lower than -1V, and the output Break_State is low after passing through the voltage comparator. When the input is not disconnected, the external input signal generates a Break_Detect signal after passing through the voltage follower. Since the input signal range is 0-5V, Break_Detect is higher than -1V, and the output Break_State is high after passing through the voltage comparator.

[0069] In particular, a voltage-dividing resistor R4 is connected in parallel between the output pin of the voltage comparator U1B and the digital isolation unit 6, and a voltage-dividing resistor R5 is connected in series, and the voltage-dividing resistor R4 is electrically connected to an external +5Vviso power supply;

[0070] The two resistors R4 and R5 are used in the voltage divider network to generate a reference voltage (e.g. -1V) through voltage division. This reference voltage is used to compare with the voltage on Break_Detect. When the Break_Detect voltage is lower than the reference voltage (e.g. in the case of a disconnection, Break_Detect is -12V), the voltage comparator will output a low level (Break_State is low), indicating that the input signal is in a disconnection state. Conversely, when the Break_Detect voltage is higher than the reference voltage (e.g. within the normal input signal range, Break_Detect is 0-5V), the voltage comparator will output a high level (Break_State is high), indicating that the input signal is normal.

[0071] In addition, a diode D2 is connected in parallel between the output pin of the voltage comparator U1B and the digital isolation unit 6, and the diode D2 is grounded; the role of the diode D2 is generally to protect the voltage comparator from the influence of reverse voltage, or to clamp to ensure that the input of the voltage comparator does not exceed its operating range. At the input end of the voltage comparator, D2 can prevent any signal exceeding a predetermined voltage level from damaging the comparator.

[0072] The parts of the present invention that are not described in detail are prior art. It is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention; therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the appended claims rather than the above description. Therefore, it is intended to include all changes within the meaning and scope of the equivalent elements of the claims in the present invention, and any figure marks in the claims should not be regarded as limiting the claims involved.

Claims

1. A disconnection detection circuit based on analog input signal, characterized in that: It comprises a signal receiving unit (1), a disconnection detection unit (2), a voltage comparison unit (3), an AD acquisition unit (4), a reference isolation power supply (5) and a control unit (8); The first loop input pin of the signal receiving unit (1) is electrically connected to the disconnection detection unit (2), and the first loop output pin of the signal receiving unit (1) is electrically connected to the voltage comparison unit (3); the second loop input pin of the signal receiving unit (1) is electrically connected to the external input wiring (9), and the second loop output pin of the signal receiving unit (1) is electrically connected to the AD acquisition unit (4); The signal input pin of the disconnection detection unit (2) is electrically connected to the external input wiring (9), and the power input pin of the disconnection detection unit (2) is electrically connected to the reference isolation power supply (5); The voltage comparison unit (3) is electrically connected to the control unit (8) via the digital isolation unit (6); The AD acquisition unit (4) is electrically connected to the control unit (8) via the communication isolation unit (7).

2. The disconnection detection circuit based on analog input signal as claimed in claim 1, characterized in that: The reference isolation power supply (5) is used to receive an external power supply and generate ±12Vviso power supplies, wherein the +12Vviso voltage is used as a positive voltage for the disconnection detection unit (2) to work, and the -12Vviso voltage is used as a reference detection voltage of the disconnection detection unit (2).

3. The disconnection detection circuit based on analog input signal according to claim 1, characterized in that: The reference isolation power supply (5) comprises an isolation chip, a filter circuit and a voltage stabilization circuit, wherein the filter circuit is used to filter out noise of the external power supply; The isolation chip is used to convert the filtered power supply into a ±12Vviso power supply; The voltage stabilizing circuit is used to stabilize the +12Vviso power supply and the -12Vviso reference power supply, and then outputs them to the disconnection detection unit (2).

4. The disconnection detection circuit based on analog input signal as claimed in claim 3, characterized in that: The filtering circuit includes a filtering inductor L1, a filtering capacitor C1 and a filtering capacitor C2, wherein the +24VDC of the external power supply is electrically connected to the isolation chip through the filtering inductor L1, and the two ends of the filtering inductor L1 are respectively connected in parallel with the filtering capacitor C1 and the filtering capacitor C2, and the filtering capacitor C1 and the filtering capacitor C2 are both grounded.

5. The disconnection detection circuit based on analog input signal as claimed in claim 3, characterized in that: The voltage stabilizing circuit includes a voltage stabilizing inductor L1, a voltage stabilizing capacitor C1, a voltage stabilizing inductor L2 and a voltage stabilizing capacitor C2, wherein the voltage stabilizing inductor L1 is electrically connected to the isolation chip and the +12Vviso power supply respectively, and the voltage stabilizing capacitor C1 is connected in parallel between the voltage stabilizing inductor L1 and the +12Vviso power supply; the voltage stabilizing inductor L2 is electrically connected to the isolation chip and the -12Vviso reference power supply respectively, and the voltage stabilizing capacitor C2 is connected in parallel between the voltage stabilizing inductor L2 and the -12Vviso reference power supply; the voltage stabilizing capacitor C1 and the voltage stabilizing capacitor C2 are both grounded.

6. The disconnection detection circuit based on analog input signal according to claim 1, characterized in that: The disconnection detection unit (2) comprises a pull-up resistor R6, a resistor R7, a voltage comparator U2B and an equivalent resistor R8, wherein two ends of the resistor R7 are electrically connected to the voltage signal of the external input wiring (9) and the in-phase input pin of the voltage comparator U2B respectively, and a pull-up resistor R6 is connected in parallel between the resistor R7 and the voltage signal of the external input wiring (9), and the pull-up resistor R6 is electrically connected to a -12Vviso reference power supply; The output pin of the voltage comparator U2B is electrically connected to the first loop input pin of the signal receiving unit (1), and the inverting input pin of the voltage comparator U2B is electrically connected to the output pin of the voltage comparator U2B via an equivalent resistor R8.

7. The disconnection detection circuit based on analog input signal as claimed in claim 6, characterized in that: A protection diode D1 is connected in parallel between the resistor R7 and the voltage signal of the external input connection (9), and the protection diode D1 is grounded.

8. The disconnection detection circuit based on analog input signal according to claim 1, characterized in that: The voltage comparison unit (3) comprises a voltage dividing resistor R1, a voltage dividing resistor R2 and a voltage comparator U1B, wherein the non-inverting input terminal of the voltage comparator U1B is electrically connected to the first loop output pin of the signal receiving unit (1), and the inverting input terminal of the voltage comparator U1B is electrically connected to the voltage dividing resistor R1 and the voltage dividing resistor R2 respectively, wherein the voltage dividing resistor R1 is grounded, and the voltage dividing resistor R2 is electrically connected to a -12Vviso reference power supply; The output pin of the voltage comparator U1B is electrically connected to the digital isolation unit (6).

9. The disconnection detection circuit based on analog input signal as claimed in claim 8, characterized in that: A voltage dividing resistor R4 is connected in parallel between the output pin of the voltage comparator U1B and the digital isolation unit (6), and a voltage dividing resistor R5 is connected in series. The voltage dividing resistor R4 is electrically connected to an external +5Vviso power supply.

10. The disconnection detection circuit based on analog input signal according to claim 8, characterized in that: A diode D2 is connected in parallel between the output pin of the voltage comparator U1B and the digital isolation unit (6), and the diode D2 is grounded.

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