Protective isolation circuit and detection device

Abstract

The embodiment of the invention provides a protection isolation circuit and a detection device. The protection isolation circuit comprises a power supply processing module which comprises a power supply protection module which is configured to perform filtering processing on a first power supply signal, and an output end of the power supply processing module outputs a second power supply signal; the power supply isolation module comprises a transformer, the transformer generates a third power supply signal on the output side based on the second power supply signal, and the third power supply signal supplies power to the detection instrument; in the communication isolation module, a first communication chip is coupled with a second communication chip through a first optical coupling isolation device and a second optical coupling isolation device, and the communication isolation module can enable a second side node to generate a corresponding communication signal based on the communication signal of the first side node. According to the technical scheme, the influence of external noise on the detection instrument is reduced, the stability of the detection instrument such as a water meter and a gas meter is improved, and the detection precision is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of industrial detection, and in particular to a protective isolation circuit and a detection device. Background Art

[0002] In industry, external power supplies are often used to power water meters or gas meters to increase the service life of the meter under high communication frequencies. In the prior art, external DC power is directly provided to the meter, and the external device directly communicates with the meter. When the meter is in a harsh environment, it is easy to cause the meter to work unstably and have low measurement accuracy. Summary of the invention

[0003] The embodiments of the present disclosure provide a protective isolation circuit and a detection device to solve or alleviate one or more technical problems in the prior art.

[0004] As a first aspect of an embodiment of the present disclosure, an embodiment of the present disclosure provides a protection isolation circuit, including:

[0005] A power processing module, comprising a power protection module, wherein the power protection module is configured to filter the received first power signal, and an output end of the power processing module outputs a second power signal;

[0006] A power isolation module, comprising a transformer, wherein an input side of the transformer is coupled to an output end of the power processing module, and a third power signal is generated at an output side based on the second power signal, and the third power signal provides power to the detection instrument;

[0007] A communication isolation module, comprising a first communication chip, a first optical coupling isolation device, a second communication chip and a second optical coupling isolation device, wherein the first communication chip is coupled to a first communication node and a second communication node, the first communication chip is coupled to an input side of the first optical coupling isolation device, the output side of the first optical coupling isolation device is coupled to the second communication chip, the second communication chip is coupled to an input side of the second optical coupling isolation device, the output side of the second optical coupling isolation device is coupled to the first communication chip, the second communication chip is also coupled to a third communication node and a fourth communication node, and the third communication node and the fourth communication node are connected to a detection instrument; the communication isolation module can enable a second side node to generate a corresponding communication signal based on a communication signal of a first side node, the first side node is a group of nodes among the first communication node and the second communication node, the third communication node and the fourth communication node, and the second side node is another group of nodes;

[0008] The second power supply signal provides power to the first communication chip, the input side of the first optocoupler isolation device, and the output side of the second optocoupler isolation device, and the third power supply signal provides power to the second communication chip, the output side of the first optocoupler isolation device, and the input side of the second optocoupler isolation device.

[0009] In some embodiments, the power protection module includes a first surge protection circuit and a filter circuit, the input end of the first surge protection circuit receives the first power signal, and the first surge protection circuit is used to filter out the surge signal in the first power signal;

[0010] The filtering circuit includes a first common-mode inductor and a second common-mode inductor connected in series, an input end of the first common-mode inductor is coupled to an output end of the first surge protection circuit, an output end of the second common-mode inductor is coupled to an output end of the power processing module, and an inductance value of the first common-mode inductor is smaller than an inductance value of the second common-mode inductor.

[0011] In some embodiments,

[0012] A first capacitor and a second capacitor connected in series are arranged between the two input ends of the first common-mode inductor, and a third capacitor is also arranged; a fourth capacitor and a fifth capacitor connected in series are arranged between the two output ends of the first common-mode inductor, and a sixth capacitor is also arranged; a seventh capacitor is arranged between the two output ends of the second common-mode inductor; and / or,

[0013] The inductance value of the first common mode inductor is less than one fifth of the inductance value of the second common mode inductor.

[0014] In some embodiments, a first voltage regulator diode is arranged between the positive output terminal of the second common-mode inductor and the first power supply node, an eighth capacitor is arranged between the first power supply node and the first reference ground node, the negative output terminal of the second common-mode inductor is coupled to the first reference ground node, and the first power supply node and the first reference ground node are respectively coupled to the positive output terminal and the negative output terminal of the power processing module.

[0015] In some embodiments, the power processing module further includes a transformer module, an input end of the transformer module is connected to an output end of the power protection module, and the transformer module is configured to convert the filtered first power signal into a second power signal and output it.

[0016] In some embodiments, the power isolation module further includes a power isolation driver chip and a voltage stabilization circuit.

[0017] The power isolation driver chip is used to receive the second power signal and provide a driving voltage to the input side of the transformer, so that the output side of the transformer generates a third power signal;

[0018] The voltage stabilizing circuit is used for performing voltage stabilization processing on the third power supply signal.

[0019] In some embodiments, the protection isolation circuit further includes a power output module, and the power output module includes a linear regulated power supply;

[0020] The voltage stabilizing circuit includes a second voltage stabilizing diode, a ninth capacitor, a first resistor and a tenth capacitor;

[0021] The positive output terminal of the transformer is coupled to the second power supply node through the second voltage regulator diode, the ninth capacitor and the first resistor are connected in parallel between the second power supply node and the second reference ground node, the negative output terminal of the transformer is coupled to the second reference ground node, and the second reference ground node is also coupled to the first reference ground node through the tenth capacitor, the second power supply node and the second reference ground node are respectively coupled to the positive input terminal and the negative input terminal of the power output module; the positive output terminal and the negative output terminal of the power output module are respectively coupled to the positive input terminal and the negative input terminal of the detection instrument.

[0022] In some embodiments, further comprising a first communication protection module and a second communication protection module;

[0023] The first communication protection module is coupled to the first communication node and the second communication node, and is configured to filter the received first communication signal and transmit the filtered first communication signal to the first communication node and the second communication node;

[0024] The third communication node and the fourth communication node are connected to the detection instrument through the second communication protection module, and the second communication protection module is configured to filter the second communication signal from the detection instrument and transmit the filtered second communication signal to the third communication node and the fourth communication node;

[0025] The A pin and B pin of the first communication chip are coupled to the first communication node and the second communication node respectively; the RO pin of the first communication chip is coupled to the base of the first transistor, the collector of the first transistor is coupled to the negative pole of the input side of the first optocoupler isolation device, and the emitter of the output side of the first optocoupler isolation device is coupled to the RE pin of the second communication chip; the RO pin of the second communication chip is coupled to the base of the second transistor, the collector of the second transistor is coupled to the negative pole of the input side of the second optocoupler isolation device, and the emitter of the output side of the second optocoupler isolation device is coupled to the RE pin of the first communication chip; the A pin and B pin of the second communication chip are coupled to the third communication node and the fourth communication node respectively.

[0026] In some embodiments, a second surge protection circuit is further included, the second surge protection circuit includes a positive signal input terminal and a negative signal input terminal, a first TSS tube and a second TSS tube connected in series are arranged between the positive signal input terminal and the negative signal input terminal, a first fuse is arranged between the positive signal input terminal and the positive node, a second fuse is arranged between the negative signal input terminal and the negative node, an eighth TVS tube is arranged between the positive node and the ground signal, a sixth TVS tube is arranged between the negative node and the ground signal, and a seventh TVS tube is arranged between the positive node and the negative node;

[0027] The first communication protection module and / or the second communication protection module both include a second surge protection circuit.

[0028] In some embodiments,

[0029] In the first communication protection module, the first communication node is coupled to the first positive signal node through the second resistor, and the second communication node is coupled to the first negative signal node through the first resistor; the positive node of the second surge protection circuit is coupled to the first positive signal node, the negative node of the second surge protection circuit is coupled to the first negative signal node, a second capacitor is provided between the first positive signal node and the third reference ground node, and a first capacitor is provided between the first negative signal node and the third reference ground node;

[0030] In the second communication protection module, the third communication node is coupled to the second positive signal node through the eighteenth resistor, and the fourth communication node is coupled to the second negative signal node through the seventeenth resistor; the positive node of the second surge protection circuit is coupled to the second positive signal node, and the negative node of the second surge protection circuit is coupled to the second negative signal node, a sixth capacitor is arranged between the second positive signal node and the fourth reference ground node, and a fifth capacitor is arranged between the second negative signal node and the fourth reference ground node.

[0031] As a second aspect of an embodiment of the present disclosure, an embodiment of the present disclosure provides a detection device, including the protection isolation circuit of any one of the present disclosure, and also including a detection instrument, the third power supply signal in the protection isolation circuit is connected to the power input terminal of the detection instrument, and the third communication node and the fourth communication node in the protection isolation circuit are connected to the communication interface of the detection instrument.

[0032] According to the technical solution of the embodiment of the present disclosure, a first power signal provided by an external power supply is first filtered by a power protection module, and a power processing module outputs a second power signal at an output end based on the filtered first power signal; an output end of the power processing module is coupled to an input side of a transformer, and the transformer generates a third power signal at an output side based on the second power signal, and the input side and the output side of the transformer are isolated from each other, so that the third power signal is isolated from the second power signal, and therefore, the third power signal will not be interfered by the front-end signal of the transformer, so that the power provided by the third power signal to the detection instrument is a stable power supply, which reduces the influence of common-mode interference and differential-mode interference introduced by the external power supply on the detection instrument, avoids the influence of noise introduced by the external power supply on the detection instrument, improves the stability of the instrument power supply, and thus can improve the stability and detection accuracy of the instrument detection.

[0033] In addition, the external device can be connected to the first communication node and the second communication node, and the external device is connected to the detection instrument through the communication isolation module. The communication isolation module realizes complete isolation of the communication signals on both sides, which can avoid the noise introduced by the external communication bus from affecting the measurement performance of the detection instrument, improve the anti-interference ability of the detection instrument, reduce the impact of the external environment on the detection instrument, and improve the measurement accuracy of the detection instrument.

[0034] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present disclosure will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments according to the present disclosure and should not be regarded as limiting the scope of the present disclosure.

[0036] Figure 1 This is a schematic diagram of the structure of a protective isolation circuit in an embodiment of the present disclosure;

[0037] Figure 2 It is a schematic diagram of a power protection module in a protection isolation circuit according to an embodiment of the present disclosure;

[0038] Figure 3 This is a schematic diagram of the circuit structure of a power protection module in a protection isolation circuit according to an embodiment of the present disclosure;

[0039] Figure 4 This is a schematic diagram of the circuit structure of a power isolation module in a protection isolation circuit according to an embodiment of the present disclosure;

[0040] Figure 5 It is a circuit diagram of a protection isolation circuit in another embodiment of the present disclosure;

[0041] Figure 6 This is a schematic diagram of power connection of a communication isolation module in an embodiment of the present disclosure;

[0042] Figure 7 Schematic diagram of the structure of a second surge protection circuit in an embodiment of the present disclosure.

[0043] Description of reference numerals:

[0044] 11. Power supply protection module; 111. First surge protection circuit; 112. Filter circuit; 12. Transformer module; 20. Power supply isolation module; 30. Power supply output module; 40. First communication protection module; 50. Communication isolation module; 60. Second communication protection module. DETAILED DESCRIPTION

[0045] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0046] Herein, coupling may include: direct physical contact between two ends or indirect connection between two ends (eg, connection between two ends via a signal line). The embodiment of the present invention does not limit the coupling method between two ends.

[0047] In the field of industrial automation control, there are a large number of electromagnetic interference sources, such as the start and stop of motors, the operation of frequency converters, etc. It is a very common solution in industry to use external power supplies to power instruments and exchange data through the 485 bus. However, since the installation site is specified by the customer, the instrument often needs to be installed in a large pump room with a harsh electromagnetic environment, and the external power of the instrument and the power supply on the pump valve are not separated. Inevitably, the external power supply and signal lines will introduce interference from the external environment, affecting the metering data of the instrument.

[0048] In order to reduce the impact of the external environment on the instrument, an embodiment of the present disclosure provides a protective isolation circuit.

[0049] Figure 1 FIG. 1 is a schematic diagram of a protective isolation circuit in an embodiment of the present disclosure. Figure 1 As shown, the protection isolation circuit includes a power processing module, a power isolation module 20 and a communication isolation module 50. The protection isolation circuit may also include a power output module 30.

[0050] The power processing module includes a power protection module 11, and the input end of the power protection module 11 is connected to an external power supply. The first power signal Power1 can be provided to the power protection module 11 by the external power supply. The power protection module 11 is configured to filter the received first power signal Power1. The output end of the power protection module 11 is connected to the output end of the power processing module, and the output end of the power processing module can output a second power signal Power2 based on the filtered first power signal Power1. The second power signal Power2 can have the same voltage as the first power signal Power1, or it can be different.

[0051] The power isolation module 20 includes a transformer T3, the input side of the transformer T3 can be coupled to the output end of the power processing module, the input side of the transformer T3 receives the second power signal Power2, and generates a third power signal Power3 on the output side based on the second power signal Power2. The third power signal Power3 provides power to the detection instrument. The detection instrument can be a water meter or a gas meter, etc.

[0052] The communication isolation module 50 includes a first communication chip, a first optical coupling isolation device, a second communication chip, and a second optical coupling isolation device. The first communication chip is coupled to the first communication node and the second communication node, the first communication chip is coupled to the input side of the first optical coupling isolation device, the output side of the first optical coupling isolation device is coupled to the second communication chip, the second communication chip is coupled to the input side of the second optical coupling isolation device, the output side of the second optical coupling isolation device is coupled to the first communication chip, and the second communication chip is also coupled to the third communication node and the fourth communication node. The third communication node and the fourth communication node are connected to the detection instrument. The communication isolation module can enable the second side node to generate a corresponding communication signal based on the communication signal of the first side node. The first side node is a group of nodes among the first communication node and the second communication node, the third communication node and the fourth communication node, and the second side node is another group of nodes.

[0053] For example, when the first communication node and the second communication node receive a communication signal, the first side node includes the first communication node and the second communication node, and the second side node includes the third communication node and the fourth communication node; when the third communication node and the fourth communication node receive a communication signal, the first side node includes the third communication node and the fourth communication node, and the second side node includes the first communication node and the second communication node.

[0054] Since the first communication chip and the second communication chip are isolated and connected through the first optocoupler isolation device and the second optocoupler isolation device, the communication signals of the first communication node and the second communication node are isolated from the communication signals of the third communication node and the fourth communication node, thereby realizing isolated communication between the first side node and the second side node.

[0055] The second power signal Power2 provides power to the first communication chip, the input side of the first optocoupler isolation device, and the output side of the second optocoupler isolation device. The third power signal Power3 provides power to the second communication chip, the output side of the first optocoupler isolation device, and the input side of the second optocoupler isolation device.

[0056] The power output module 30 is configured to receive the third power signal and provide a preset working voltage to the detection instrument. The preset working voltage may be the same as the voltage of the third power signal.

[0057] In the technical solution disclosed in the present invention, the first power signal Power1 provided by the external power supply is first filtered by the power protection module 11, and the power processing module outputs the second power signal Power2 at the output end based on the filtered first power signal Power1; the output end of the power processing module is coupled to the input side of the transformer T3, and the transformer T3 generates a third power signal Power3 at the output side based on the second power signal Power2, and the input side and the output side of the transformer T3 are isolated from each other, so that the third power signal Power3 is isolated from the second power signal Power2, and therefore, the third power signal Power3 will not be interfered by the front-end signal of the transformer T3, so that the power provided by the third power signal Power3 to the detection instrument is a stable power supply, which reduces the influence of common-mode interference and differential-mode interference introduced by the external power supply on the detection instrument, avoids the influence of noise introduced by the external power supply on the detection instrument, improves the stability of the instrument power supply, and thus can improve the stability and detection accuracy of the instrument detection.

[0058] In addition, in the technical solution disclosed in the present invention, the communication isolation module 50 uses optical coupling isolation technology to isolate the signal, and the power supply signals of the optical coupling input and output are also isolated from each other, which realizes the complete electrical isolation between the circuits on both sides of the communication isolation module 50, so that the insulation resistance on both sides is very high, which can effectively prevent the noise, interference or fault in the circuit on one side from being transmitted to the circuit on the other side, and ensure the stability and safety of the circuit. For sensitive electronic equipment or circuits, optical coupling isolation can avoid common mode interference and ground loop interference caused by electrical connection, and improve the quality and reliability of the signal.

[0059] The external device can be connected to the first communication node and the second communication node. The external device is connected to the detection instrument through the communication isolation module 50. The communication isolation module 50 realizes complete isolation of the communication signals on both sides, which can avoid the noise introduced by the external communication bus from affecting the measurement performance of the detection instrument, improve the anti-interference ability of the detection instrument, reduce the impact of the external environment on the detection instrument, and improve the measurement accuracy of the detection instrument.

[0060] Figure 2 Schematic diagram of a power protection module in a protection isolation circuit according to an embodiment of the present disclosure. Figure 3 FIG. 1 is a schematic diagram of the circuit structure of a power supply protection module in a protection isolation circuit according to an embodiment of the present disclosure. Figure 2As shown, the power protection module 11 may include a first surge protection circuit 111 and a filter circuit 112. The input end of the first surge protection circuit 111 may receive a first power supply signal. The positive input end of the first surge protection circuit 111 is connected to the positive electrode V-IN of the external power supply, and the negative input end of the first surge protection circuit 111 is connected to the negative electrode GND-IN of the external power supply. The first surge protection circuit 111 is used to filter out surge signals in the first power supply signal.

[0061] For example, the first surge protection circuit 111 can be a protection circuit composed of a fuse (also called a fuse) and a surge protection device, etc., which filters high-voltage and high-current pulses (such as lightning coupling, large motor starting, electrostatic discharge, etc.) entering from an external power supply to ensure the service life of the back-end devices. The specific structure of the first surge protection circuit 111 can adopt a common structure in the art and is not specifically limited here.

[0062] The filter circuit 112 is used to filter the first power supply signal. The filter circuit 112 may include components such as inductors and capacitors. The filter circuit 112 filters the common mode noise and differential mode noise of the first power supply signal through the components such as inductors and capacitors.

[0063] The filter circuit 112 may include a first-stage filter unit and a second-stage filter unit. The first-stage filter unit may perform preliminary filtering on common-mode noise of lower frequencies, and the second-stage filter unit may further attenuate common-mode noise of higher frequencies remaining after the first stage. After preliminary filtering by the first-stage filter unit, the remaining common-mode noise is further suppressed in the second-stage filter unit, so that the common-mode noise component in the final output signal is significantly reduced, thereby achieving effective suppression of common-mode noise within a wider frequency range. The leakage inductance on the first-stage filter unit may perform preliminary attenuation on differential-mode noise, and the leakage inductance on the second-stage filter unit may further suppress differential-mode noise remaining after the first-stage processing, thereby improving the suppression capability of the entire filter circuit 112 on differential-mode noise.

[0064] like Figure 3 As shown, the filter circuit 112 may include a first common-mode inductor L1 and a second common-mode inductor L2 connected in series. The input end of the first common-mode inductor L1 is coupled to the output end of the first surge protection circuit 111. For example, the two input ends of the first common-mode inductor L1 are respectively coupled to the positive output end and the negative output end of the first surge protection circuit 111. The two output ends of the first common-mode inductor L1 are respectively coupled to the two input ends of the second common-mode inductor L2. The output end of the second common-mode inductor L2 is coupled to the output end of the power processing module. The inductance value of the first common-mode inductor L1 may be less than the inductance value of the second common-mode inductor L2. The inductance values ​​of the first common-mode inductor L1 and the second common-mode inductor L2 may be set as needed.

[0065] The filter circuit 112 is configured to filter out common-mode interference signals and / or differential-mode interference signals in the first power supply signal.

[0066] For example, Figure 3 As shown, the filter circuit 112 may also include a plurality of capacitors. A first capacitor C1 and a second capacitor C2 connected in series are provided between the two input ends of the first common mode inductor L1, and a third capacitor C3 is also provided. The first capacitor C1 and the second capacitor C2 are connected in series between the two input ends of the first common mode inductor L1, and the third capacitor C3 is provided between the two input ends of the first common mode inductor L1. The first capacitor C1 and the second capacitor C2 are close to the first surge protection circuit 111 relative to the third capacitor C3. The connection point of the first capacitor C1 and the second capacitor C2 is connected to the earth EARTH.

[0067] A fourth capacitor C4 and a fifth capacitor C5 connected in series are provided between the two output ends of the first common mode inductor L2, and a sixth capacitor C6 is also provided. The fourth capacitor C4 and the fifth capacitor C5 are connected in series between the two output sections of the first common mode inductor L2, and the sixth capacitor C6 is provided between the two output ends of the first common mode inductor L1. The fourth capacitor C4 and the fifth capacitor C5 are closer to the output end of the first common mode inductor L1 relative to the sixth capacitor C6. The connection point of the fourth capacitor C4 and the fifth capacitor C5 is connected to the earth EARTH.

[0068] A first TVS tube D1 is also provided between the two output ends of the first common mode inductor L2. The first TVS tube D1 is close to the output end of the first common mode inductor L1 relative to the fourth capacitor C4 and the fifth capacitor C5. The output end of the first common mode inductor L2 corresponding to the negative pole of the power supply is also connected to the reference ground GND.

[0069] A seventh capacitor C7 is arranged between two output terminals of the second common mode inductor.

[0070] from Figure 3 It can be seen that the filter circuit 112 includes two common-mode inductors L1 and L2, and multiple capacitors. The filter circuit 112 can filter out common-mode and differential-mode interference entering from the external power line, while also avoiding its own interference with the power grid. By setting two common-mode inductors and multiple capacitors, the filtering of interference signals is enhanced.

[0071] Among them, the first-stage filtering unit includes a first common-mode inductor L1, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, and a sixth capacitor C6. The first-stage filtering unit can effectively filter out most of the common-mode and differential-mode interference introduced by the external power supply. The second-stage filtering unit includes a second common-mode inductor and a seventh capacitor C7, and the second-stage filtering unit can further filter out the remaining interference. Exemplarily, the inductance value of the first common-mode inductor L1 is less than one-fifth of the inductance value of the second common-mode inductor L2. Each capacitor needs to select a capacitor with a high withstand voltage. The first common-mode inductor L1 can also play a role in decoupling between the first TVS tube D1 and the first surge protection circuit 111, so that the high-voltage and high-current pulse first passes through the first surge protection circuit 111 and then passes through the first TVS tube D1 for secondary protection, which more effectively reduces the value of the transient voltage.

[0072] In one embodiment, in order to stabilize the output voltage of the filter circuit 112, as Figure 3 As shown, a first voltage zener diode D2 is provided between the positive output terminal of the second common-mode inductor L2 and the first power supply node V-OUT1. An eighth capacitor C8 is provided between the first power supply node V-OUT1 and the first reference ground node GND-1. The negative output terminal of the second common-mode inductor L2 is coupled to the first reference ground node GND-1, and the first power supply node V-OUT1 and the first reference ground node GND-1 are coupled to the positive output terminal and the negative output terminal of the power processing module, respectively.

[0073] In one embodiment, Figure 1 As shown, the power processing module may further include a transformer module 12, and the output end of the power protection module 11 is connected to the output end of the power processing module through the transformer module 12. Exemplarily, the input end of the transformer module 12 is connected to the output end of the power protection module 11, and the output end of the transformer module 12 is connected to the output end of the power processing module, and the output end of the transformer module 12 may be the output end of the power processing module. The transformer module 12 is configured to convert the filtered first power signal into a second power signal and output it, so that the output end of the power processing module outputs the second power signal.

[0074] When the voltage transformation module 12 is not provided, the voltage of the second power signal is the same as the voltage of the first power signal, which requires that the voltage provided by the external power supply must be the same as the required second power signal.

[0075] By setting the transformer module 12, when the filtered first power signal passes through the transformer module 12, the transformer module 12 performs a voltage step-up or voltage step-down process on the received first power signal, and converts the first power signal into a second power signal, so that the voltage range of the first power signal can be increased, so that the range of external power supplies applicable to the normal operation of the protection isolation circuit is larger. The input voltage range of the external power supply is determined by the working range of the transformer module 12. Exemplarily, the voltage range of the external power supply can be 4.5V to 36V, and the voltage of the second power signal can be 24V.

[0076] It should be noted that Figure 3 FIG. 1 shows an exemplary structure of the filter circuit 112. A person skilled in the art can understand that Figure 3 The filter circuit 112 shown in the figure can be a structure. Those skilled in the art can modify it based on the conventional technology in the field. Figure 3 The filter circuit 112 structure can achieve its function by adding or reducing components. As long as the filter circuit 112 includes two common-mode inductors connected in series and can achieve a filtering effect, it belongs to the protection scope of the filter circuit 112 of the present disclosure.

[0077] Figure 4 FIG. 1 is a schematic diagram of the circuit structure of a power isolation module in a protection isolation circuit according to an embodiment of the present disclosure. Figure 4 As shown, the power isolation module 20 may include a power isolation driver chip and a voltage stabilizing circuit. The power isolation driver chip is used to receive the second power signal and provide a driving voltage to the input side of the transformer T3, so that the output side of the transformer T3 generates a third power signal. The voltage stabilizing circuit is used to stabilize the third power signal so that the voltage of the output third power signal is more stable.

[0078] The power isolation driver chip converts the second power signal into a driving signal of the transformer T3 and outputs it to the transformer T3, driving the transformer T3 to generate a magnetic field for energy transfer, thereby realizing electrical isolation on the power supply, so that the output side of the transformer T3 generates a third power signal, and the third power signal is isolated from the second power signal. The voltage stabilizing circuit stabilizes the voltage transmitted from the output side of the transformer T3, thereby improving the stability of the output voltage of the transformer T3.

[0079] The power isolation driver chip can be selected as appropriate as needed, and any chip that can achieve its function can be selected. The transformer T3 can be selected as appropriate as needed, and any transformer that can achieve its function can be selected.

[0080] like Figure 4As shown, the voltage stabilizing circuit may include a second voltage stabilizing diode D3, a ninth capacitor C9, a first resistor R1 and a tenth capacitor C10. The positive output terminal of the transformer T3 is coupled to the second power supply node V-OUT2 through the second voltage stabilizing diode D3. The ninth capacitor C9 and the first resistor R1 are connected in parallel between the second power supply node V-OUT2 and the second reference ground node GND-2. The negative output terminal of the transformer T3 is coupled to the second reference ground node GND-2, and the second reference ground node GND-2 is also coupled to the first reference ground node GND-1 through the tenth capacitor C10. The second power supply node V-OUT2 and the second reference ground node GND-2 are coupled to the positive input terminal and the negative input terminal of the power output module 30, respectively.

[0081] The first resistor R1 is used to improve the stability of the output voltage when no-load, and the tenth capacitor C10 is used to suppress common-mode interference and electrostatic discharge (ESD) protection. The tenth capacitor C10 needs to be a high-voltage capacitor.

[0082] The output end of the power output module 30 can be connected to the detection instrument, and the positive output end and the negative output end of the power output module 30 can be coupled to the positive input end and the negative input end of the detection instrument. The power output module 30 can include a linear voltage-stabilized power supply. After the power output module 30 receives the third power signal, the third power signal is further stabilized by a linear voltage-stabilized power supply, and the stabilized power supply is provided to the detection instrument, thereby providing a preset working voltage to the detection instrument. The preset working voltage can be the same as the voltage of the third power signal.

[0083] like Figure 1 As shown, the protection isolation circuit may further include a first communication protection module 40 and a second communication protection module 60 .

[0084] The first communication protection module 40 receives a first communication signal from an external device. The first communication protection module 40 is configured to filter the received first communication signal and transmit the filtered first communication signal to the communication isolation module 50. The communication isolation module 50 can enable the third communication node and the fourth communication node to generate a corresponding third communication signal based on the first communication signal, and transmit it to the detection instrument through the second communication protection module 60. The second communication protection module 60 is configured to filter the second communication signal from the detection instrument and transmit the filtered second communication signal to the communication isolation module 50. The communication isolation module 50 can enable the first communication node and the second communication node to generate a fourth communication signal based on the second communication signal, and transmit it to the external device through the first communication protection module 40. In this way, communication between the detection instrument and the external device can be achieved. Exemplarily, the detection instrument can perform RS485 communication with the external device.

[0085] Figure 5FIG. 1 is a circuit diagram of a protective isolation circuit in another embodiment of the present disclosure. Figure 5 As shown, the first communication protection module 40 is coupled to the first communication node P1 and the second communication node N1, and the first communication protection module 40 transmits the filtered first communication signal to the first communication node P1 and the second communication node N1.

[0086] The communication isolation module 50 includes a first communication chip U1, a first optocoupler isolation device U2, a second communication chip U4 and a second optocoupler isolation device U3. Among them, the A pin and the B pin of the first communication chip U1 are coupled to the first communication node P1 and the second communication node N1 respectively. The RO pin of the first communication chip is coupled to the base of the first transistor Q1, and the collector of the first transistor Q1 is coupled to the negative electrode of the input side of the first optocoupler isolation device U2. The emitter on the output side of the first optocoupler isolation device U2 is coupled to the RE pin of the second communication chip U4. The RE pin of the second communication chip U4 is short-circuited with the DE pin.

[0087] The RO pin of the second communication chip U4 is coupled to the base of the second transistor Q2, and the collector of the second transistor Q2 is coupled to the negative electrode of the input side of the second optocoupler isolation device U3. The emitter of the output side of the second optocoupler isolation device U3 is coupled to the RE pin of the first communication chip U1, and the RE pin of the first communication chip U1 is short-circuited with the DE pin.

[0088] The A pin and the B pin of the second communication chip U4 are coupled to the third communication node P2 and the fourth communication node N2 respectively.

[0089] The second communication protection module 60 is coupled to the third communication node P2 and the fourth communication node N2, and transmits the filtered second communication signal to the third communication node P2 and the fourth communication node N2.

[0090] Exemplarily, the first communication chip and the second communication chip may both be 485 chips. In actual implementation, other types of communication chips may also be selected as needed.

[0091] Figure 5 The detailed circuit diagram of the communication isolation module in one embodiment is exemplarily shown. The first communication node P1 is coupled to the third power supply node V-P1 through a pull-up resistor R5, and the second communication node N1 is coupled to the third reference ground node GND-P1 through a pull-down resistor R3. A fourth resistor R4 is provided between the first communication node P1 and the second communication node N1. The third communication node P2 is coupled to the fourth power supply node V-P2 through a pull-up resistor R16, and the fourth communication node N2 is coupled to the fourth reference ground node GND-P2 through a pull-down resistor R14. A fifteenth resistor R15 is provided between the third communication node P2 and the fourth communication node N2.

[0092] Figure 6 FIG. 1 is a schematic diagram of the power connection of the communication isolation module in one embodiment of the present disclosure. Figure 6 As shown, the second power signal Power2 is provided to the first communication chip U1, the input side of the first optical coupling isolation device U2, and the output side of the second optical coupling isolation device U3. Figure 6 As shown, the second power signal Power2 output by the transformer module 12 provides a voltage to the third power node V-P1 and the third reference ground node GND-P1. Exemplarily, the second power signal Power2 can be provided to a linear regulated power supply, which regulates the second power signal, and then provides a regulated voltage to the third power node V-P1 and the third reference ground node GND-P1.

[0093] like Figure 5 As shown, the VCC pin of the first communication chip U1 is coupled to the third power supply node V-P1, and the GND pin and DI pin of the first communication chip U1 are both coupled to the third reference ground node GND-P1. The positive pin on the input side of the first optocoupler isolation device U2 is coupled to the third power supply node V-P1 through a pull-up resistor R8, and the emitter of the first transistor Q1 is coupled to the third reference ground node GND-P1. The base on the output side of the second optocoupler isolation device U3 is coupled to the third power supply node V-P1, and the collector on the output side of the second optocoupler isolation device U3 is coupled to the third power supply node V-P1 through a pull-up resistor R9. The emitter on the output side of the second optocoupler isolation device U3 is coupled to the third reference ground node GND-P1.

[0094] like Figure 6 As shown, the third power signal Power3 provides a power signal to the second communication chip U4, the output side of the first optocoupler isolation device U2, and the input side of the second optocoupler isolation device U3. Exemplarily, the third power signal Power3 can provide a voltage to the fourth power node V-P2 and the fourth reference ground node GND-P2 through the power output module 30.

[0095] like Figure 5 As shown, the VCC pin of the fourth communication chip U4 is coupled to the fourth power supply node V-P2, and the GND pin and DI pin of the fourth communication chip U4 are both coupled to the fourth reference ground node GND-P2. The positive pin on the input side of the second optocoupler isolation device U3 is coupled to the fourth power supply node V-P2 through a pull-up resistor R10, and the emitter of the second transistor Q2 is coupled to the fourth reference ground node GND-P2. The base on the output side of the first optocoupler isolation device U2 is coupled to the fourth power supply node V-P2, and the collector on the output side of the first optocoupler isolation device U2 is coupled to the fourth power supply node V-P2 through a pull-up resistor R11. The emitter on the output side of the first optocoupler isolation device U2 is coupled to the fourth reference ground node GND-P2.

[0096] from Figure 5 It can be seen that the communication isolation module 50 uses optocoupler isolation technology to isolate the signal, and the power supply signals of the optocoupler isolation input and output are also isolated.

[0097] The implementation principle of the communication isolation module 50 is as follows:

[0098] When the signal is sent from the first communication protection module 40 to the second communication protection module 60, according to the transmission characteristics of the 485 signal, when the voltage on the A pin on the first communication chip U1 minus the voltage on the B pin is greater than 0.2V, the R0 pin of the first communication chip U1 outputs a high level, the level on the resistor R7 is a high level, the first transistor Q1 is turned on, the first optocoupler isolation device U2 is turned on, and the 5th pin of the first optocoupler isolation device U2 is connected to the RE and DE pins of the second communication chip U4, so that the RE and DE pins of the second communication chip U4 are low levels. At this time, the second communication chip U4 is in a receiving state, and due to the pull-up resistor R16 and the pull-down resistor R14 on the A and B pins of the second communication chip U4, the A pin of the second communication chip U4 is high and the B pin is low, and the second The voltage of the A pin of the communication chip U4 minus the voltage of the B pin is greater than 0.2V, which is the same as the input signal on the first communication chip U1. Therefore, the A and B pins of the second communication chip U4 transmit the 485 signal to the second communication protection module 60, and then transmit it to the detection instrument; because the voltage of the A pin of the second communication chip U4 minus the voltage of the B pin is greater than 0.2V, the RO pin of the second communication chip U4 is at a high level. At this time, the resistor R12 connected to the RO port of the second communication chip U4 is at a high level, the second transistor Q2 is turned on, the second optocoupler isolation device U3 is turned on, and the 5 pin of the second optocoupler isolation device U3 is connected to the RE and DE pins of the first communication chip U1, so that the RE and DE pins of the first communication chip U1 are at a low level. At this time, the first communication chip U1 is in a receiving state.

[0099] When the voltage on the A pin of the first communication chip U1 minus the voltage on the B pin is less than 0.2V, the R0 pin of the first communication chip U1 outputs a low level, the level on the resistor R7 is a low level, the first transistor Q1 is turned off, the first optocoupler isolation device U2 is turned off, and the 5th pin of the first optocoupler isolation device U2 is connected to the RE and DE pins of the second communication chip U4. At this time, due to the action of the pull-up resistor R11, the RE and DE pins of the second communication chip U4 are high levels. At this time, the second communication chip U4 is in the sending state. Since the DI pin of the second communication chip U4 is at a low level at this time, the A pin of the second communication chip U4 is a low level and the B pin is a high level. In addition, the voltage of the A pin of the second communication chip U4 minus the voltage of the B pin is less than 0.2V, which is the same as the input signal on the first communication chip U1. Therefore, the A and B pins of the second communication chip U4 transmit the 485 signal to the second communication protection module 60, and then transmit it to the detection instrument.

[0100] After the above process, the external 485 signal is effectively transmitted from the first communication protection module 40 to the second communication protection module 60 after being isolated by the communication isolation module 50, and then transmitted to the detection instrument.

[0101] When the signal is sent from the second communication protection module 60 to the first communication protection module 40, according to the transmission characteristics of the 485 signal, when the voltage of the A pin on the second communication chip U4 minus the voltage of the B pin is greater than 0.2V, the R0 pin of the second communication chip U4 outputs a high level, the level on the resistor R12 is a high level, the second transistor Q2 is turned on, the second optocoupler isolation device U3 is turned on, and the 5th pin of the second optocoupler isolation device U3 is connected to the RE and DE pins of the first communication chip U1, so that the RE and DE pins of the first communication chip U1 are low levels. At this time, the first communication chip U1 is in a receiving state. Due to the pull-up resistor R5 and the pull-down resistor R3 on the A and B pins of the first communication chip U1, the A pin of the first communication chip U1 is a high level and the B pin is a low level, and the first communication chip U1 is in a receiving state. The voltage of the A pin of the communication chip U1 minus the voltage of the B pin is greater than 0.2V, which is the same as the input signal on the second communication chip U4. Therefore, the A and B pins of the first communication chip U1 transmit the 485 signal to the first communication protection module 40, and then transmit it to the outside; because the voltage of the A pin of the first communication chip U1 minus the voltage of the B pin is greater than 0.2V, the RO pin of the first communication chip U1 is at a high level. At this time, the resistor R7 connected to the RO port of the first communication chip U1 is at a high level, the first transistor Q1 is turned on, the first optocoupler isolation device U2 is turned on, and the 5 pins of the first optocoupler isolation device U2 are connected to the RE and DE pins of the second communication chip U4 device, so that the RE and DE pins of the second communication chip U4 are at a low level. At this time, the second communication chip U4 is in a receiving state.

[0102] When the voltage on the A pin of the second communication chip U4 minus the voltage on the B pin is less than 0.2V, the R0 pin of the second communication chip U4 outputs a low level, the level on the resistor R12 is a low level, the second transistor Q2 is turned off, the second optocoupler isolation device U3 is turned off, and the 5th pin of the second optocoupler isolation device U3 is connected to the RE and DE pins of the first communication chip U1. Due to the action of the pull-up resistor R9, the RE and DE pins of the first communication chip U1 are high levels at this time, and the first communication chip U1 device is in the sending state. Since the DI pin of the first communication chip U1 is low at this time, the A pin of the first communication chip U1 is low level and the B pin is high level. In addition, the voltage of the A pin of the first communication chip U1 minus the voltage of the B pin is less than 0.2V, which is the same as the input signal on the second communication chip U4. The A and B pins of the first communication chip U1 transmit the 485 signal to the first communication protection module 40, and then transmit it to the outside.

[0103] After the above process, the 485 signal of the detection instrument is effectively transmitted from the second communication protection module 60 to the second communication protection module 60 after being isolated by the communication isolation module 50, and then transmitted to the external data collector.

[0104] Figure 7 FIG. 1 is a schematic diagram of the structure of a second surge protection circuit in an embodiment of the present disclosure. Figure 5 As shown, the first communication protection module 40 and / or the second communication protection module 60 both include a second surge protection circuit. The second surge protection circuit includes a positive signal input terminal P and a negative signal input terminal N. In the first communication protection module 40, the second surge protection circuit includes a positive signal input terminal P and a negative signal input terminal N connected to a 485 signal line of an external device. In the second communication protection module 40, the second surge protection circuit includes a positive signal input terminal P and a negative signal input terminal N connected to a 485 signal line of a detection instrument.

[0105] A first TSS tube T1 and a second TSS tube T2 connected in series are provided between the positive signal input terminal P and the negative signal input terminal N, and the connection point of the first TSS tube T1 and the second TSS tube T2 is connected to the earth EARTH. A first fuse F3 is provided between the positive signal input terminal P and the positive node P-1, a second fuse F2 is provided between the negative signal input terminal N and the negative node N-1, an eighth TVS tube D8 is provided between the positive node P-1 and the earth EARTH, a sixth TVS tube D6 is provided between the negative node N-1 and the earth EARTH, and a seventh TVS tube D7 is provided between the positive node P-1 and the negative node N-1.

[0106] The external input 485 signal is connected to the positive signal input terminal P and the negative signal input terminal N of the second surge protection circuit. The large current and voltage are first filtered through the first TSS tube T1 and the second TSS tube T2 to play the role of primary protection; the first fuse F3 and the second fuse F2 play the role of decoupling to ensure that the TSS tube works before the rear TVS tube, and the fuse also plays the role of short-circuit protection for the circuit; the TVS tube behind the fuse will further filter the residual voltage after the first-level protection, making the second surge protection circuit more reliable and preventing the rear-end components from being damaged by surge voltage and current.

[0107] Exemplarily, for the first communication protection module 40, the positive node P-1 of the second surge protection circuit is connected to the first communication node P1, and the negative node N-1 of the second surge protection circuit is connected to the second communication node N1.

[0108] For the second communication protection module 60, the positive node P-1 of the second surge protection circuit is connected to the third communication node P2, and the negative node N-1 of the second surge protection circuit is connected to the fourth communication node N2.

[0109] like Figure 5 As shown, in the first communication protection module 40, the first communication node P1 is coupled to the first positive signal node A1_P through the second resistor R2, and the second communication node N1 is coupled to the first negative signal node B1_N through the first resistor R1; the positive node P-1 of the second surge protection circuit is coupled to the first positive signal node A1_P, and the negative node N-1 of the second surge protection circuit is coupled to the first negative signal node B1_N, a second capacitor C2 is arranged between the first positive signal node A1_P and the third reference ground node GND-P1, and a first capacitor C1 is arranged between the first negative signal node B1_N and the third reference ground node GND-P1.

[0110] In the second communication protection module 60, the third communication node P2 is coupled to the second positive signal node A2_P through the eighteenth resistor R18, and the fourth communication node N2 is coupled to the second negative signal node B2_N through the seventeenth resistor R17; the positive node P-1 of the second surge protection circuit is coupled to the second positive signal node A2_P, and the negative node N-1 of the second surge protection circuit is coupled to the second negative signal node B2_N, a sixth capacitor C6 is arranged between the second positive signal node A2_P and the fourth reference ground node GND-P2, and a fifth capacitor C5 is arranged between the second negative signal node B2_N and the fourth reference ground node GND-P2.

[0111] like Figure 5As shown, the first communication protection module 40 may include a first RC filter unit, and the first RC filter unit may include a first capacitor C1, a second capacitor C2, a first resistor R1 and a second resistor R2. When the 485 signal after passing through the second surge protection circuit passes through the first RC filter unit, the first RC filter unit can further filter out the high-frequency interference signal in the 485 signal, and then transmit it to the first communication chip U1 in the communication isolation module 50. The capacitance value of the capacitor and the resistance value of the resistor in the RC filter unit can be selected as needed.

[0112] The second communication protection module 60 may include a second RC filtering unit, and the second RC filtering unit may include a fifth capacitor C5, a sixth capacitor C6, a seventeenth resistor R17, and an eighteenth resistor R18.

[0113] The present disclosure also provides a detection device, including the protection isolation circuit in any embodiment of the present disclosure, and also including a detection instrument. The third power supply signal in the protection isolation circuit is connected to the power input terminal of the detection instrument, and the third communication node and the fourth communication node in the protection isolation circuit are connected to the communication interface of the detection instrument. Exemplarily, the positive signal input terminal P and the negative signal input terminal N of the second surge protection circuit in the second communication protection module 60 of the protection isolation circuit are correspondingly connected to the communication interface of the detection instrument.

[0114] The detection device disclosed in the present invention can be applied in an industrial control system. The protection isolation circuit of the embodiment of the present invention is used at the front end of the detection instrument to improve the stability of the power supply of the detection instrument, improve the anti-interference ability of the detection instrument in an industrial environment, improve the detection accuracy of the detection instrument, improve the accuracy and stability of signal transmission, and ensure the reliable operation of the control system. The protection isolation circuit disclosed in the present invention can be used as an external module of the detection instrument and can be applied to various detection instruments, such as water meters, electricity meters, gas meters, flow meters, etc.

[0115] In the description of this specification, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present disclosure.

[0116] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0117] In the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", "coupled", "fixed" and the like should be understood in a broad sense, for example, it can be fixed coupling, detachable coupling, or integrated; it can be mechanical coupling, electrical coupling, or communication; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0118] In the present disclosure, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being “above”, “above”, and “above” a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0119] The disclosure above provides many different embodiments or examples to implement different structures of the present disclosure. In order to simplify the present disclosure, the components and settings of specific examples are described above. Of course, they are only examples, and the purpose is not to limit the present disclosure. In addition, the present disclosure can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0120] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of various changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A protective isolation circuit, characterized in that: include: A power processing module, comprising a power protection module, wherein the power protection module is configured to filter the received first power signal, and an output end of the power processing module outputs a second power signal; A power isolation module, comprising a transformer, wherein an input side of the transformer is coupled to an output end of the power processing module, and a third power signal is generated at an output side based on the second power signal, wherein the third power signal provides power to the detection instrument; A communication isolation module, comprising a first communication chip, a first optical coupling isolation device, a second communication chip and a second optical coupling isolation device, wherein the first communication chip is coupled to a first communication node and a second communication node, the first communication chip is coupled to an input side of the first optical coupling isolation device, the output side of the first optical coupling isolation device is coupled to the second communication chip, the second communication chip is coupled to an input side of the second optical coupling isolation device, the output side of the second optical coupling isolation device is coupled to the first communication chip, the second communication chip is also coupled to a third communication node and a fourth communication node, the third communication node and the fourth communication node are connected to the detection instrument; the communication isolation module can enable the second side node to generate a corresponding communication signal based on the communication signal of the first side node, the first side node is a group of nodes among the first communication node and the second communication node, the third communication node and the fourth communication node, and the second side node is another group of nodes; The second power supply signal provides power to the first communication chip, the input side of the first optocoupler isolation device, and the output side of the second optocoupler isolation device, and the third power supply signal provides power to the second communication chip, the output side of the first optocoupler isolation device, and the input side of the second optocoupler isolation device.

2. The protective isolation circuit according to claim 1, characterized in that: The power protection module includes a first surge protection circuit and a filter circuit, the input end of the first surge protection circuit receives the first power signal, and the first surge protection circuit is used to filter out surge signals in the first power signal; The filtering circuit includes a first common-mode inductor and a second common-mode inductor connected in series, an input end of the first common-mode inductor is coupled to an output end of the first surge protection circuit, an output end of the second common-mode inductor is coupled to an output end of the power processing module, and an inductance value of the first common-mode inductor is smaller than an inductance value of the second common-mode inductor.

3. The protective isolation circuit according to claim 2, characterized in that: A first capacitor and a second capacitor connected in series are arranged between the two input ends of the first common-mode inductor, and a third capacitor is also arranged; a fourth capacitor and a fifth capacitor connected in series are arranged between the two output ends of the first common-mode inductor, and a sixth capacitor is also arranged; a seventh capacitor is arranged between the two output ends of the second common-mode inductor; and / or, The inductance value of the first common mode inductor is less than one fifth of the inductance value of the second common mode inductor.

4. The protective isolation circuit according to claim 2, characterized in that: A first voltage regulator diode is arranged between the positive output terminal of the second common-mode inductor and the first power supply node, an eighth capacitor is arranged between the first power supply node and the first reference ground node, the negative output terminal of the second common-mode inductor is coupled to the first reference ground node, and the first power supply node and the first reference ground node are coupled to the positive output terminal and the negative output terminal of the power processing module respectively.

5. The protective isolation circuit according to claim 1, characterized in that: The power processing module further includes a transformer module, an input end of the transformer module is connected to an output end of the power protection module, and the transformer module is configured to convert the filtered first power signal into the second power signal and output it.

6. The protective isolation circuit according to any one of claims 1, characterized in that: The power isolation module also includes a power isolation driver chip and a voltage stabilizing circuit. The power isolation driver chip is used to receive the second power signal and provide a driving voltage to the input side of the transformer, so that the output side of the transformer generates the third power signal; The voltage stabilizing circuit is used for performing voltage stabilization processing on the third power supply signal.

7. The protective isolation circuit according to claim 6, characterized in that: The protection isolation circuit also includes a power output module, and the power output module includes a linear voltage-regulated power supply; The voltage stabilizing circuit includes a second voltage stabilizing diode, a ninth capacitor, a first resistor and a tenth capacitor; The positive output terminal of the transformer is coupled to the second power supply node through the second voltage regulator diode, the ninth capacitor and the first resistor are connected in parallel between the second power supply node and the second reference ground node, the negative output terminal of the transformer is coupled to the second reference ground node, the second reference ground node is also coupled to the first reference ground node through the tenth capacitor, the second power supply node and the second reference ground node are respectively coupled to the positive input terminal and the negative input terminal of the power output module; the positive output terminal and the negative output terminal of the power output module are respectively coupled to the positive input terminal and the negative input terminal of the detection instrument.

8. The protective isolation circuit according to claim 1, characterized in that: Also includes a first communication protection module and a second communication protection module; The first communication protection module is coupled to the first communication node and the second communication node, and is configured to filter the received first communication signal and transmit the filtered first communication signal to the first communication node and the second communication node; The third communication node and the fourth communication node are connected to the detection instrument through the second communication protection module, and the second communication protection module is configured to filter the second communication signal from the detection instrument and transmit the filtered second communication signal to the third communication node and the fourth communication node; The A pin and B pin of the first communication chip are coupled to the first communication node and the second communication node respectively; the RO pin of the first communication chip is coupled to the base of the first transistor, the collector of the first transistor is coupled to the negative pole of the input side of the first optocoupler isolation device, and the emitter of the output side of the first optocoupler isolation device is coupled to the RE pin of the second communication chip; the RO pin of the second communication chip is coupled to the base of the second transistor, the collector of the second transistor is coupled to the negative pole of the input side of the second optocoupler isolation device, and the emitter of the output side of the second optocoupler isolation device is coupled to the RE pin of the first communication chip; the A pin and B pin of the second communication chip are coupled to the third communication node and the fourth communication node respectively.

9. The protective isolation circuit according to claim 8, characterized in that: The first communication protection module and / or the second communication protection module both include a second surge protection circuit; The second surge protection circuit includes a positive signal input terminal and a negative signal input terminal, a first TSS tube and a second TSS tube connected in series are arranged between the positive signal input terminal and the negative signal input terminal, a first fuse is arranged between the positive signal input terminal and the positive node, a second fuse is arranged between the negative signal input terminal and the negative node, an eighth TVS tube is arranged between the positive node and the ground signal, a sixth TVS tube is arranged between the negative node and the ground signal, and a seventh TVS tube is arranged between the positive node and the negative node.

10. The protective isolation circuit according to claim 9, characterized in that: In the first communication protection module, the first communication node is coupled to the first positive signal node through a second resistor, and the second communication node is coupled to the first negative signal node through a first resistor; the positive node of the second surge protection circuit is coupled to the first positive signal node, the negative node of the second surge protection circuit is coupled to the first negative signal node, a second capacitor is provided between the first positive signal node and a third reference ground node, and a first capacitor is provided between the first negative signal node and the third reference ground node; In the second communication protection module, the third communication node is coupled to the second positive signal node through the eighteenth resistor, and the fourth communication node is coupled to the second negative signal node through the seventeenth resistor; the positive node of the second surge protection circuit is coupled to the second positive signal node, and the negative node of the second surge protection circuit is coupled to the second negative signal node, a sixth capacitor is arranged between the second positive signal node and the fourth reference ground node, and a fifth capacitor is arranged between the second negative signal node and the fourth reference ground node.

11. A detection device, characterized in that: It includes the protection isolation circuit described in any one of claims 1 to 10, and also includes a detection instrument, the third power supply signal in the protection isolation circuit is connected to the power supply input terminal of the detection instrument, and the third communication node and the fourth communication node in the protection isolation circuit are connected to the communication interface of the detection instrument.

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