Low-pass filtering, sampling and amplifying circuit applied to alternating current insulation monitoring device

Abstract

The utility model discloses a low-pass filtering sampling amplification circuit applied to an AC insulation monitoring device, comprising a sampling circuit, a filtering circuit and an operational amplification circuit, the sampling circuit comprises a bidirectional transient suppression diode, a resistor R104 and a resistor R8, the filtering circuit comprises an RC second-order filtering circuit and an RCR third-order filtering circuit, and the operational amplification circuit is connected with the RC second-order filtering circuit and the RCR third-order filtering circuit. The operational amplifier circuit comprises a first operational amplifier circuit and a second operational amplifier circuit, the first operational amplifier circuit comprises a first operational amplifier and a peripheral circuit thereof, and the second operational amplifier circuit comprises a second operational amplifier and a peripheral circuit thereof; an analog semaphore is input to the sampling circuit, sequentially passes through the filter circuit, the first operational amplifier circuit and the second operational amplifier circuit and then is output. The low-pass filtering sampling amplification circuit provided by the utility model can eliminate clutter signal interference of a power grid, improve the accuracy of sampling data, and guarantee the fault positioning function of a load branch of a device.

Description

Technical Field

[0001] The utility model relates to the technical field of amplifier circuits, in particular to a low-pass filtering sampling amplifier circuit applied to an AC insulation monitoring device. Background Art

[0002] AC insulation monitoring devices can be used to detect the insulation resistance of a ship's three-phase AC power grid to ground. As waterborne vehicles, ships are typically equipped with a three-phase AC power grid to meet their power needs. In electrical systems, to ensure safety, equipment or circuits must be sufficiently insulated from the ground. Insulation resistance is a measure of this insulation performance. If the insulation resistance is too low, there may be a risk of a short circuit to ground, causing a power grid trip or safety incident. When the AC insulation monitoring device detects a power grid insulation failure to ground, it activates the load fault branch location function, alerting personnel to promptly troubleshoot and address potential faults or issues.

[0003] Conventional detection methods include detecting the leakage current of each load branch through an AC sensor installed at the lower end of each load branch; collecting leakage current data from sensors throughout the ship through a preset sampling circuit, comparing and deriving the faulty branch, and realizing the positioning function of the load fault branch.

[0004] However, as various loads are put into operation, the power grid is affected by interference factors such as unbalanced three-phase load branches, uneven distributed capacitance, increased capacitance to ground, and various clutter signals. This can easily lead to inaccurate leakage current detection or saturation of the sampling circuit, ultimately causing inaccurate positioning of the load fault branch and false alarms. Utility Model Content

[0005] In view of the above-mentioned deficiencies in the current sampling circuit, the utility model provides a low-pass filtering sampling amplifier circuit applied to an AC insulation monitoring device, which can eliminate the interference of clutter signals in the power grid, improve the accuracy of the sampling data, and ensure the load branch fault location function of the device.

[0006] In order to achieve the above-mentioned purpose, the embodiments of the present invention adopt the following technical solutions:

[0007] A low-pass filtering sampling and amplifying circuit for an AC insulation monitoring device includes a sampling circuit, a filtering circuit, and an operational amplifier circuit. The sampling circuit includes a bidirectional transient suppression diode, a resistor R104, and a resistor R8. The filtering circuit includes an RC second-order filtering circuit and an RCR third-order filtering circuit. The operational amplifier circuit includes a first operational amplifier circuit and a second operational amplifier circuit. The first operational amplifier circuit includes a first operational amplifier and its peripheral circuits, and the second operational amplifier circuit includes a second operational amplifier and its peripheral circuits. The output end of the sampling circuit is connected to the filtering circuit, the output end of the filtering circuit is connected to the input end of the first operational amplifier circuit, and the output end of the first operational amplifier circuit is connected to the input end of the second operational amplifier circuit. An analog signal is input to the sampling circuit and is output after passing through the filtering circuit, the first operational amplifier circuit, and the second operational amplifier circuit in sequence.

[0008] According to one aspect of the present invention, the bidirectional transient suppression diode, resistor R104, and resistor R8 are connected in parallel, one end of the bidirectional transient suppression diode is connected to the analog signal input end, and the other end of the bidirectional transient suppression diode is grounded.

[0009] According to one aspect of the present invention, the bidirectional transient voltage suppression diode is a SMBJ3.3CA diode.

[0010] According to one aspect of the present invention, the RCR third-order filter circuit includes a resistor R4, a capacitor C4 and a resistor R6, one end of the resistor R4 is connected to the analog signal input terminal, and the other end is connected to the resistor R6 and then connected to the inverting input port of the first operational amplifier; one end of the capacitor C4 is connected between the resistor R4 and the resistor R6, and the other end of the capacitor C4 is connected to the resistor R12 and then connected to the non-inverting input port of the first operational amplifier; the other end of the resistor C4 is also grounded.

[0011] According to one aspect of the present invention, the RC second-order filter circuit includes a resistor R2 and a capacitor C2, one end of the resistor R2 is connected between the resistor R4 and the resistor R6, and the other end of the resistor R2 is connected to the capacitor C2 and the output end of the first operational amplifier; the other end of the capacitor C2 is connected to the resistor R6 and the inverting input port of the first operational amplifier.

[0012] According to one aspect of the present invention, the peripheral circuit of the first operational amplifier circuit includes a resistor R15, a resistor R16, a resistor R20, a resistor R22, a capacitor C6, and a capacitor C8. One end of the resistor R16 is connected to the inverting input terminal of the first operational amplifier and the capacitor C6, the other end of the resistor R16 is connected to the resistor R15, the capacitor C8, and the resistor R20, the other end of the resistor R15 is connected to the output terminal of the first operational amplifier, the other end of the capacitor C8 is connected to the resistor R22 and then to the non-inverting input terminal of the first operational amplifier, and the other end of the resistor R20 is connected to the capacitor C6 and the output terminal of the first operational amplifier circuit.

[0013] According to one aspect of the present invention, the peripheral circuit of the second operational amplifier circuit includes a resistor R9, a resistor R17 and a resistor R23. The output end of the first operational amplifier circuit is connected to the resistor R23 and then to the non-inverting input end of the second operational amplifier. One end of the resistor R17 is connected to the output end of the second operational amplifier, and the other end is connected to the inverting input end of the second operational amplifier and the resistor R9. The other end of the resistor R9 is grounded.

[0014] Advantages of the implementation of the present invention: The present invention eliminates clutter interference signals in the AC power grid by designing a low-pass filter circuit in the sampling and amplifying circuit, adjusting the parameters of the low-pass filter circuit, and setting a suitable cut-off frequency, thereby effectively improving the accuracy of data sampling and providing a strong guarantee for the load branch fault locating function of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 A circuit diagram of a sampling amplifier circuit in the prior art;

[0017] Figure 2 This is a circuit diagram of the low-pass filtering sampling and amplifying circuit described in the present utility model;

[0018] Figure 3 This is a schematic diagram of the principle of the sampling device described in the present utility model. DETAILED DESCRIPTION

[0019] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, removable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this utility model based on specific circumstances.

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] The specific values ​​or models of the components such as resistors, capacitors, diodes, and operational amplifiers described in this embodiment can refer to the circuit marking information shown in the accompanying drawings. Some numerical parameters may be slightly adjusted due to the influence of the external measurement environment.

[0022] like Figure 1 The figure shows a conventional sampling and amplification circuit in the prior art. The sampling circuit lacks a filtering circuit, resulting in significant interference from noise in the analog input signal. Due to the unbalanced three-phase load branches, uneven distributed capacitance, increased capacitance to ground, and other interference factors in the 50Hz AC power grid, these noise interference signals are also amplified after the analog input collected by the sensor is amplified by the operational amplifier. As interference signals increase, leakage current detection may be inaccurate or the analog output of the sampling circuit may become saturated, ultimately leading to inaccurate data calculation results.

[0023] like Figure 2 As shown, this embodiment provides a low-pass filtering sampling and amplification circuit for an AC insulation monitoring device, comprising a sampling circuit, a filtering circuit, and an operational amplifier circuit. By incorporating a low-pass filtering circuit into the circuit and combining it with an improved measurement method, interference factors such as clutter can be eliminated, improving the accuracy of the sampled data.

[0024] The sampling circuit includes a bidirectional transient suppression diode, a resistor R104 and a resistor R8, the filtering circuit includes an RC second-order filtering circuit and an RCR third-order filtering circuit, the operational amplifier circuit includes a first operational amplifier circuit and a second operational amplifier circuit, the first operational amplifier circuit includes a first operational amplifier U2 and its peripheral circuits, and the second operational amplifier circuit includes a second operational amplifier U3 and its peripheral circuits.

[0025] The output end of the sampling circuit is connected to the filtering circuit, the output end of the filtering circuit is connected to the input end of the first operational amplifier circuit, the output end of the first operational amplifier circuit is connected to the input end of the second operational amplifier circuit, and the analog signal is input to the sampling circuit, and is output after passing through the filtering circuit, the first operational amplifier circuit, and the second operational amplifier circuit in sequence.

[0026] In practical applications, the bidirectional transient suppression diode D2, resistor R104, and resistor R8 in the sampling circuit are connected in parallel, one end of the bidirectional transient suppression diode D2 is connected to the analog signal input terminal S1, and the other end of the bidirectional transient suppression diode is grounded, and the resistors R104, R8, R12, and capacitor C4 are grounded.

[0027] In this embodiment, the bidirectional transient suppression diode D2 is an SMBJ3.3CA type diode, which is used to protect the circuit from transient voltage interference. When overvoltage or overcurrent occurs in the circuit, the bidirectional transient suppression diode D2 can quickly absorb the overvoltage or overcurrent, thereby protecting other components in the circuit from damage.

[0028] In practical applications, the RCR third-order filter circuit in the filter circuit includes a resistor R4, a capacitor C4 and a resistor R6. One end of the resistor R4 is connected to the analog signal input terminal S1, and the other end is connected to the resistor R6 and then connected to the inverting input port of the first operational amplifier U2; one end of the capacitor C4 is connected between the resistor R4 and the resistor R6, and the other end of the capacitor C4 is connected to the resistor R12 and then connected to the non-inverting input port of the first operational amplifier U2; the other end of the resistor C4 is grounded.

[0029] In practical applications, the RC second-order filter circuit in the filter circuit includes a resistor R2 and a capacitor C2. One end of the resistor R2 is connected between the resistor R4 and the resistor R6, and the other end of the resistor R2 is connected to the capacitor C2 and the output end of the first operational amplifier U2; the other end of the capacitor C2 is connected to the resistor R6 and the inverting input port of the first operational amplifier U2.

[0030] In actual applications, the peripheral circuit of the first operational amplifier circuit includes resistor R15, resistor R16, resistor R20, resistor R22, capacitor C6, and capacitor C8. One end of resistor R16 is connected to the inverting input terminal of the first operational amplifier U2 and capacitor C6, and the other end of resistor R16 is connected to resistor R15, capacitor C8, and resistor R20. The other end of resistor R15 is connected to the output terminal of the first operational amplifier U2, the other end of capacitor C8 is connected to resistor R22 and then to the non-inverting input terminal of the first operational amplifier U2, and the other end of resistor R20 is connected to capacitor C6 and the output terminal of the first operational amplifier circuit.

[0031] In actual applications, the peripheral circuit of the second operational amplifier circuit includes resistor R9, resistor R17 and resistor R23. The output end of the first operational amplifier circuit is connected to resistor R23 and then connected to the non-inverting input end of the second operational amplifier U3. One end of resistor R17 is connected to the output end of the second operational amplifier U3, and the other end is connected to the inverting input end of the second operational amplifier U3 and resistor R9. The other end of resistor R9 is grounded.

[0032] like Figure 3 As shown, the sampling device adopts the principle of the low-pass filter sampling amplifier circuit of this embodiment. The working principle of the device in the power grid is to inject a 1.25Hz low-frequency AC detection signal into the power grid through the signal source Us set inside the measuring host, and send the detected leakage current signal to the sampling device through the AC sensor 10 set at the lower end of each load branch, and send the leakage current signal to the detection point ( Figure 2 The analog input terminal S1 shown in the figure is configured to filter out frequencies above 1.25 Hz by adjusting the parameters of the low-pass filter circuit and setting a suitable cutoff frequency (based on actual working conditions), thereby reducing interference, especially the numerous interference signals caused by the 50 Hz working condition on the device measurement. Finally, the analog output signal after filtering and amplification is sent to the AD conversion chip, which converts the analog signal into a digital signal that is easy to calculate and transmits it to the MCU for calculation. This greatly improves the accuracy of the load fault branch locating function.

[0033] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A low-pass filter sampling amplifier circuit used in an AC insulation monitoring device, comprising a sampling circuit, a filter circuit and an operational amplifier circuit, characterized in that: The sampling circuit includes a bidirectional transient suppression diode, a resistor R104 and a resistor R8, the filtering circuit includes an RC second-order filtering circuit and an RCR third-order filtering circuit, the operational amplifier circuit includes a first operational amplifier circuit and a second operational amplifier circuit, the first operational amplifier circuit includes a first operational amplifier and its peripheral circuit, and the second operational amplifier circuit includes a second operational amplifier and its peripheral circuit; the output end of the sampling circuit is connected to the filtering circuit, the output end of the filtering circuit is connected to the input end of the first operational amplifier circuit, the output end of the first operational amplifier circuit is connected to the input end of the second operational amplifier circuit, and the analog signal is input to the sampling circuit, and is output after passing through the filtering circuit, the first operational amplifier circuit, and the second operational amplifier circuit in sequence.

2. The low-pass filtering sampling and amplifying circuit according to claim 1, characterized in that: The bidirectional transient suppression diode, the resistor R104 and the resistor R8 are connected in parallel, one end of the bidirectional transient suppression diode is connected to the analog signal input terminal, and the other end of the bidirectional transient suppression diode is grounded.

3. The low-pass filter sampling and amplifying circuit according to claim 1, characterized in that: The model of the bidirectional transient suppression diode is SMBJ3.3CA diode.

4. The low-pass filtering sampling and amplifying circuit according to claim 1, characterized in that: The RCR third-order filter circuit includes a resistor R4, a capacitor C4 and a resistor R6, one end of the resistor R4 is connected to the analog signal input end, and the other end is connected to the resistor R6 and then connected to the inverting input port of the first operational amplifier; one end of the capacitor C4 is connected between the resistor R4 and the resistor R6, and the other end of the capacitor C4 is connected to the resistor R12 and then connected to the non-inverting input port of the first operational amplifier; the other end of the resistor C4 is also grounded.

5. The low-pass filtering sampling and amplifying circuit according to claim 4, characterized in that: The RC second-order filter circuit includes a resistor R2 and a capacitor C2, one end of the resistor R2 is connected between the resistor R4 and the resistor R6, and the other end of the resistor R2 is connected to the capacitor C2 and the output end of the first operational amplifier; the other end of the capacitor C2 is connected to the resistor R6 and the inverting input port of the first operational amplifier.

6. The low-pass filter sampling and amplifying circuit according to claim 1, characterized in that: The peripheral circuit of the first operational amplifier circuit includes a resistor R15, a resistor R16, a resistor R20, a resistor R22, a capacitor C6, and a capacitor C8. One end of the resistor R16 is connected to the inverting input terminal of the first operational amplifier and the capacitor C6. The other end of the resistor R16 is connected to the resistor R15, the capacitor C8, and the resistor R20. The other end of the resistor R15 is connected to the output terminal of the first operational amplifier. The other end of the capacitor C8 is connected to the resistor R22 and then to the non-inverting input terminal of the first operational amplifier. The other end of the resistor R20 is connected to the capacitor C6 and the output terminal of the first operational amplifier circuit.

7. The low-pass filter sampling and amplifying circuit according to claim 1, characterized in that: The peripheral circuit of the second operational amplifier circuit includes a resistor R9, a resistor R17 and a resistor R23. The output end of the first operational amplifier circuit is connected to the resistor R23 and then connected to the non-inverting input end of the second operational amplifier. One end of the resistor R17 is connected to the output end of the second operational amplifier, and the other end is connected to the inverting input end of the second operational amplifier and the resistor R9. The other end of the resistor R9 is grounded.

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