CN215344565U

CN215344565U - Circuit module for power line carrier communication test platform and test platform

Info

Publication number: CN215344565U
Application number: CN202120661609.9U
Authority: CN
Inventors: 山峰
Original assignee: Ningbo Sanxing Medical and Electric Co Ltd
Current assignee: Ningbo Sanxing Electric Co Ltd; Ningbo Sanxing Medical and Electric Co Ltd
Priority date: 2021-03-31
Filing date: 2021-03-31
Publication date: 2021-12-28
Anticipated expiration: 2031-03-31

Abstract

The utility model relates to a circuit module for a power line carrier communication test platform and a corresponding test platform, the circuit module comprises a power supply filtering module (1) with one end connected with a power frequency power supply and the other end connected with a testing machine (3) or a tested device (4), and a signal coupling module (2) connected between the power supply filtering module (1) and the testing machine (3) or the tested device (4), the signal coupling module (2) comprises a high-pass filter (21) capable of providing low impedance in a frequency band range of carrier communication, and a coupling transformer (22) which is connected with the high-pass filter (21) and can increase the common-mode impedance between a first power line (31) and the ground between the testing machine (3) and the power supply filtering module (1) and between a second power line (41) and the ground between the tested device (4) and the power supply filtering module (1) through self isolation characteristics to reduce the common-mode voltage on the ground line. The application improves the test accuracy.

Description

Circuit module for power line carrier communication test platform and test platform

Technical Field

The utility model relates to the technical field of power electronics, in particular to a circuit module for a power line carrier communication test platform and a corresponding test platform.

Background

The power line carrier communication is a communication mode in which a power transmission line is used as a transmission medium of carrier signals, is economical and reliable because a communication line does not need to be additionally laid, and is a communication means preferentially adopted by all power departments in the world. In order to simulate the power line carrier communication and detect the receiving sensitivity of the tested device, it is a common measure in laboratories to establish a power line carrier communication test platform.

The main structure of the existing power line carrier communication test platform is shown in fig. 1, a test machine and a tested device are respectively connected to an artificial power network, the artificial power network separates a high-frequency carrier signal from a power frequency voltage and outputs the high-frequency carrier signal through a weak current port, the two artificial power networks are connected through an adjustable attenuator and used for adjusting the strength of the signal, meanwhile, the artificial power network and the adjustable attenuator are interconnected through a shielding wire, and a power filter is arranged at the front end of a power supply port of the artificial power network to weaken the influence of external power noise on a test result. The artificial power supply network is a standardized product, and the basic structure of the artificial power supply network is shown in fig. 2, namely, impedance isolation is realized through an L1/L2 inductor and a preceding power supply, a power frequency signal is blocked through a C1/C2 capacitor, a high-frequency signal is separated through an R1/R2 resistor, and the high-frequency signal is connected with the ground through an R1/R2 resistor.

The receiving sensitivity of the power line carrier communication product is very high (25 dBuV-45 dBuV), so that very high requirements are put on a test platform. However, because all devices in the existing test platform are not ideal, two paths of L1-C1-R1 and L2-C2-R2 are not in an ideal balance state, an alternating current signal, that is, a high-frequency carrier signal, generates a common mode current on the ground line shown in fig. 2 during operation, and meanwhile, when the device to be tested and the test machine are in operation, a common mode current consistent with the high-frequency carrier signal is generated and flows through the ground line shown in fig. 2, and common mode noise caused by the common mode current is converted into a differential mode signal to be received by the test machine or the device to be tested, so that the real receiving sensitivity of the device cannot be measured, and meanwhile, the common mode current causes the carrier signal not to be transmitted according to a predetermined path, so that the carrier signal skips over the adjustable attenuator, and the measured receiving sensitivity of the device is far better than the actual receiving sensitivity.

In order to solve the problem, the artificial power supply network needs to be grounded with extremely low impedance to prevent common-mode current from flowing through large ground impedance to generate common-mode signals consistent with carrier signals, which requires that a low-impedance ground stub is provided in an office environment, but the common office environment cannot meet the requirement.

Moreover, because a large number of electrical equipment such as computers and printers exist in an office environment, power noise is high, so that power noise of a power grid is very high, the existing power filter can only provide a requirement for enabling the electrical equipment to meet electromagnetic compatibility, and the power noise cannot be reduced to a level lower than the carrier communication sensitivity of a product.

SUMMERY OF THE UTILITY MODEL

In view of the above problems, an object of the present invention is to provide a circuit module for a power line carrier communication test platform, which can reduce a common mode voltage by reducing a common mode current on a ground line, and ensure test accuracy.

The utility model also aims to provide a circuit module for a power line carrier communication test platform, which can ensure that the noise of a power grid is suppressed to an extremely low level.

The utility model also aims to provide a power line carrier communication test platform adopting the circuit module.

In order to achieve the purpose, the technical scheme of the utility model is as follows: a circuit module for a power line carrier communication test platform comprises a power supply filtering module and a signal coupling module, wherein one end of the power supply filtering module is connected with a power frequency power supply, the other end of the power supply filtering module is connected with a test machine or a tested device, and the signal coupling module is connected between the power supply filtering module and the test machine or the tested device, and the circuit module is characterized in that:

the signal coupling module comprises a high-pass filter which can provide low impedance in the frequency band range of carrier communication, and a coupling transformer which is connected with the high-pass filter and can increase the common-mode impedance between a first power line and the ground between the testing machine and the power supply filtering module and between a second power line and the ground between the tested device and the power supply filtering module through the isolation characteristic of the coupling transformer to reduce the common-mode voltage on the ground line.

Further, the high-pass filter is composed of a first capacitor.

Further, the capacitance value of the first capacitor is 1 uF.

Further, the parasitic capacitance capacity value of the coupling transformer is between 10pF and 30 pF.

Further, the power supply filtering module is a multistage filter.

Furthermore, the power supply filtering module comprises a primary filter consisting of a first inductor, a second capacitor, a third capacitor and a second inductor, and a secondary filter consisting of a third inductor, a fourth capacitor, a fifth capacitor and a fourth inductor;

the third inductor is connected between the second capacitor and the fourth capacitor, and the fourth inductor is connected between the third capacitor and the fifth capacitor;

the power supply filtering module further comprises a fifth inductor and a sixth inductor, wherein one end of the fifth inductor is connected with the fourth capacitor, the other end of the fifth inductor is used as a live wire output end, the inductance value of the fifth inductor is equal to that of the first inductor, one end of the sixth inductor is connected with the fifth capacitor, the other end of the sixth inductor is used as a zero wire output end, and the inductance value of the sixth inductor is equal to that of the second inductor.

Furthermore, the inductance of the first inductor to the sixth inductor is more than 0.5mH, and the frequency of the primary filter and the frequency of the secondary filter are less than or equal to 1 kHz.

Furthermore, the secondary side of the coupling transformer is connected with a fixed attenuation module which can perform primary attenuation on the high-frequency signal, and the output end of the fixed attenuation module is connected with a splitter/combiner module.

The utility model provides a power line carrier communication test platform which characterized in that: the power line carrier communication test platform adopts the circuit module.

Further, the tester and the corresponding circuit module in the power line carrier communication test platform are arranged in the first shielding box, and the tested device and the corresponding circuit module are arranged in the second shielding box.

Compared with the prior art, the utility model has the advantages that:

the carrier signal is transmitted through the coupling transformer, and the isolation characteristic of the coupling transformer is utilized to increase the common-mode impedance formed between the power line between the testing machine/tested equipment and the power supply filter module and the ground, so that the common-mode voltage on the grounding line, namely the common-mode voltage output to the back-end circuit, is reduced through a voltage division mode, and the accuracy of sensitivity testing is ensured; the setting of multi-stage power supply filtering and the selection of larger inductance and capacitance value improve the attenuation effect and better reduce the influence of external noise on the test effect; the arrangement of the fixed attenuator ensures that the output amplitude of the signal is within the acceptance range of the test equipment, and the splitter/combiner module improves the function of the test platform.

Drawings

Fig. 1 is a block diagram of a conventional test platform for power line carrier communication.

Fig. 2 is a schematic diagram of an artificial power network in a conventional power line carrier communication test platform.

Fig. 3 is a schematic diagram of a circuit module for a power line carrier communication test platform according to the present invention.

Fig. 4 is a block diagram of a structure of a power line carrier communication test platform according to the present application.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

As shown in fig. 3, the circuit module for the plc test platform of the present application includes a power filter module 1 terminating at a power frequency power supply and terminating at a test machine or a device under test, and a signal coupling module 2 connected between the power filter module 1 and the test machine or the device under test. The power frequency power supply is input through the L-IN port and the N-IN port, and the testing machine or the tested machine is connected through the L-OUT port and the N-OUT port.

As described above, due to the non-ideal state of the device and the working environment of the device under test and the testing machine, the testing platform may generate a common mode current during the working process, which may further affect the testing accuracy of the receiving sensitivity of the device under test. The common-mode current is mainly output to the back-end circuit through the ground wire, obviously, when the ground impedance corresponding to the ground wire is smaller, the generated common-mode signal is smaller, the influence on the test result is weaker, so the ground impedance is reduced as much as possible, the problem of the common-mode signal can be solved to a certain extent, but the common-mode current has extremely high requirements on a test field, and the common-mode current is unlikely to be realized in an actual test environment.

The artificial power supply network is improved, the influence of common-mode signals is effectively reduced on the basis that the ground impedance is not changed, specifically, the artificial power supply network is replaced by the signal coupling module 2, the signal coupling module 2 comprises a high-pass filter 21 capable of providing low impedance in the frequency band range of carrier communication, and a coupling transformer which is connected with the high-pass filter 21 and can increase the common-mode impedance between a first power line 31 between the testing machine 3 and the power supply filtering module 1 and the ground and between a second power line 41 between the tested device 4 and the power supply filtering module 1 and the ground through the isolation characteristic of the coupling transformer to reduce the common-mode voltage on the ground line.

That is, the parasitic capacitance of the coupling transformer can increase the common-mode impedance between the first power line 31 and the ground, and between the second power line 41 and the ground, and the common-mode impedance and the ground impedance on the ground line share a common voltage.

This improvement can effectively weaken common mode signal's influence under the prerequisite that does not change ground connection impedance, in other words, the improvement of this application can reduce the requirement to service environment for even can accomplish the experiment in ordinary office space, obtain accurate test result simultaneously, make the suitability of this equipment obtain promoting greatly.

In this embodiment, the high-pass filter 21 is formed by a first capacitor C1, and the capacitance value is 1uF, but the capacitance value may be other values as long as it can provide low impedance and high-pass filtering action in the frequency band range of carrier communication.

The simple components for forming the coupling transformer T1 avoid the disadvantage that the original artificial power supply network needs a plurality of components, and each component is not ideal, resulting in a large common mode current, that is, the simple components of the coupling transformer make the common mode current of the original artificial power supply network due to the unbalance of the components not exist.

Meanwhile, when the coupling transformer T1 is adopted in the application, although parasitic capacitance exists, generally, the parasitic capacitance is between 10pF-30pF, common mode impedance can be caused to be affected to a certain degree and be reduced, even if the common mode impedance is reduced, the resistance value of the common mode impedance is far greater than the common mode impedance 25 omega of the artificial power supply network, so that more common mode voltages which are generated by the tested device and the testing machine during working and are consistent with high-frequency carrier signals and originally loaded on the grounding wire are shared through the voltage division effect, the common mode voltage on the grounding wire is greatly reduced, and the measurement accuracy is effectively ensured.

The impedance calculation formula of the capacitor is Zc-1/2 pi fC, where f is the carrier frequency and C is the capacitance value of the parasitic capacitor, and in the original artificial power supply network, the common-mode impedance 25 Ω of the artificial power supply network is formed by connecting R1 and R2 in parallel. In addition, it should be mentioned that the coupling transformer T1 can isolate strong electricity while transmitting carrier signals.

In order to satisfy the noise suppression effect within the range of the carrier communication frequency band (the low frequency part is considered to be at least within 30 kHz), reduce the influence of the external noise on the test, simultaneously increase the common-mode impedance between the first power line 31 and the second power line 41 and the ground as much as possible, prevent the carrier product at the opposite end from receiving the common-mode voltage signal, increase the common-mode impedance between the first power line 31 and the second power line 41 and the input power 220VAC as much as possible, and prevent the carrier signal from entering the carrier product at the opposite end from the external 220VAC power supply through the form of the common-mode voltage, the power filter module 1 of the present application adopts a multi-stage filter during the design.

Specifically, the power filter module 1 includes a first-stage filter formed by a first inductor L1, a second capacitor C2, a third capacitor C3 and a second inductor L2, and a second-stage filter formed by a third inductor L3, a fourth capacitor C4, a fifth capacitor C5 and a fourth inductor L4, wherein the third inductor L3 is connected between the second capacitor C2 and the fourth capacitor C4, and the fourth inductor L4 is connected between the third capacitor C3 and the fifth capacitor C5.

Since the common mode impedance between the first power line 31 and the second power line 41 and the ground and the common mode impedance between the first power line 31 and the second power line 41 and the input power source 220VAC are determined by the inductance of the inductor, the inductance is larger as the inductance is larger, and therefore, in order to further reduce the influence of the common mode signal, the inductance of the first to fourth inductors is 0.5mH or more.

Since the product of the inductor and the capacitor determines the noise suppression capability of the external input power supply 220VAC, the larger the product, the stronger the noise suppression capability, and the product determines the turning frequency of the filter, the turning frequency formed by the product of the inductor and the capacitor is within 1kHz for better filtering effect.

In order to achieve better filtering, the power filter module 1 further includes a fifth inductor L5 having one end connected to the fourth capacitor C4 and the other end serving as the live output terminal LOUT and having an inductance equal to that of the first inductor L1, and a sixth inductor L6 having one end connected to the fifth capacitor C5 and the other end serving as the neutral output terminal NOUT and having an inductance equal to that of the second inductor L2. Thus, the filtering function can be achieved no matter the signal is input from the left end side of the power supply filter or the signal is input from the right end side of the power supply filter, and the power grid noise can be effectively reduced to the level lower than the carrier communication sensitivity of the product.

The application is also provided with a splitter/combiner module 5 at the rear end of the signal coupling module 2, which is used for expanding the external interface of the signal, facilitating the access of a spectrum analyzer and an oscilloscope, observing the amplitude of the carrier signal at each interface, facilitating the access of a signal generator to inject a noise signal and evaluating the receiving performance of the product in a noise environment.

Meanwhile, in order to avoid that the amplitude of the input signal of the equipment is too large, so that the signal overflows or the equipment is damaged, the device is used for protecting external equipment such as a spectrum analyzer, a signal generator, an oscilloscope and the like, the fixed attenuation module 6 capable of performing primary attenuation on the high-frequency signal is connected to the secondary side of the coupling transformer T1, and the splitter/combiner module 5 is connected to the output end of the fixed attenuation module 6.

The fixed attenuator module 6 is composed of a first resistor R1, a second resistor R2 and a third resistor R3, and since the input and output impedances of the fixed attenuator 6 are all 50 Ω, the values of R1 and R3 are the same, and the values of R1 and R3 determine the attenuation.

The splitter/combiner module 5 is composed of a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10 and an eleventh resistor R11, input and output impedances of 4 ports of the module are all 50 Ω, and in order to realize that the ports are interchangeable, that is, the ports have the same insertion loss, it is required that the fourth resistor R4, the fifth resistor R5, the eighth resistor R8 and the tenth resistor R10 have the same resistance, and the sixth resistor R6, the seventh resistor R7, the ninth resistor R9 and the eleventh resistor R11 have the same resistance.

In order to make the structure concise and facilitate operation and management, each module of the present application is integrated on one circuit board. The test platform is convenient to carry and assemble when being assembled, and meanwhile, the assembled test platform is miniaturized due to the integrated design, so that the space is saved.

When the frequency of the common mode signal is very high, the common mode signal may affect the test result in a radiation mode, so that the carrier signal is not transmitted according to a set path, but the adjustable attenuator is skipped, and the measured receiving sensitivity is far superior to the actual receiving sensitivity, in order to solve the problem, the test platform constructed by the circuit modules of the application is adopted, and the test machine 3 and the corresponding circuit module are arranged in the first shielding box 7, and the tested device 4 and the corresponding circuit module are arranged in the second shielding box 8.

By adopting the scheme of the application, the requirement on the use environment is reduced, the whole test can be completed in the common office environment, the trouble of building an expensive test laboratory is avoided, and the miniaturization of the test platform is realized.

While embodiments of the utility model have been shown and described, it will be understood by those skilled in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the utility model, the scope of which is defined by the claims and their equivalents.

Claims

1. A circuit module for a power line carrier communication test platform, the module comprising a power filter module (1) having one end connected to a power frequency power supply and the other end connected to a test machine (3) or a device under test (4), and a signal coupling module (2) connected between the power filter module (1) and the test machine (3) or the device under test (4), characterized in that:

the signal coupling module (2) comprises a high-pass filter (21) capable of providing low impedance in a frequency band range of carrier communication, and a coupling transformer (22) which is connected with the high-pass filter (21) and can increase the common-mode impedance between a first power line (31) and the ground between the testing machine (3) and the power supply filtering module (1) and between a second power line (41) and the ground between the tested device (4) and the power supply filtering module (1) through the isolation characteristic of the coupling transformer to reduce the common-mode voltage on the ground line.

2. The circuit module for a power line carrier communication test platform of claim 1, wherein:

the high-pass filter (21) is formed by a first capacitor (C1).

3. The circuit module for a power line carrier communication test platform of claim 2, wherein:

the capacitance value of the first capacitor (C1) is 1 uF.

4. The circuit module for a power line carrier communication test platform of claim 1, wherein:

the parasitic capacitance of the coupling transformer (22) is between 10pF and 30 pF.

5. The circuit module for a power line carrier communication test platform of claim 1, wherein:

the power supply filtering module (1) is a multistage filter.

6. The circuit module for a power line carrier communication test platform of claim 5, wherein:

the power supply filtering module (1) comprises a primary filter formed by a first inductor (L1), a second capacitor (C2), a third capacitor (C3) and a second inductor (L2), and a secondary filter formed by a third inductor (L3), a fourth capacitor (C4), a fifth capacitor (C5) and a fourth inductor (L4);

the third inductor (L3) is connected between the second capacitor (C2) and the fourth capacitor (C4), and the fourth inductor (L4) is connected between the third capacitor (C3) and the fifth capacitor (C5);

the power supply filtering module (1) further comprises a fifth inductor (L5) with one end connected with the fourth capacitor (C4) and the other end used as a live wire output end (LOUT) and the inductance value equal to that of the first inductor (L1), and a sixth inductor (L6) with one end connected with the fifth capacitor (C5) and the other end used as a zero wire output end (NOUT) and the inductance value equal to that of the second inductor (L2).

7. The circuit module for a power line carrier communication test platform of claim 6, wherein:

the inductance of the first inductor to the sixth inductor is more than 0.5mH, and the frequency of the primary filter and the frequency of the secondary filter are less than or equal to 1 kHz.

8. The circuit module for a power line carrier communication test platform of claim 1, wherein:

the secondary side of the coupling transformer is connected with a fixed attenuation module (6) which can attenuate high-frequency signals at one level, and the output end of the fixed attenuation module (6) is connected with a branching device/combiner module (5).

9. The utility model provides a power line carrier communication test platform which characterized in that: the power line carrier communication test platform adopts the circuit module as claimed in any one of claims 1 to 8.

10. The power line carrier communication test platform according to claim 9, wherein:

the tester (3) and the corresponding circuit module in the power line carrier communication test platform are arranged in a first shielding box (7), and the tested equipment (4) and the corresponding circuit module are arranged in a second shielding box (8).