Power line carrier communication signal program control attenuation circuit and device

Abstract

The utility model relates to the technical field of power line carrier communication testing, in particular to a programmable attenuation circuit for power line carrier communication signals. The circuit comprises high-frequency signal isolators U1 and U2; the balanced-unbalanced high-frequency isolation converters are U3 and U5; a high-frequency programmable attenuator: U4; a power supply filter U6; a voltage transformer: U7; a controller: U8; an EMI filter: U9; according to the utility model, the strong current programmable attenuator combines strong current and high-frequency signals into one, carrier communication networking test is completed in a one-stop manner, and channels are closer to application. No extra working power supply is needed, and no external interface is added. Equipment is modularized, the structure is simple, and the cost is low; the problem of channel difference caused by the fact that a twisted pair is replaced by a coaxial cable in a power line carrier communication equipment test is solved, and the problem that AC 220V current cannot pass through a weak current programmable attenuator is solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to power line carrier communication test technical field especially relates to a kind of power line carrier communication signal program control attenuation circuit. BACKGROUND

[0002] China's power grid system uses centralized meter reading equipment to collect end-user power data, and the centralized meter reading equipment relies on smart meters and mobile Internet of Things, and through the additional communication module, the power consumption data monitored by the meter is transmitted to the power consumption billing server of the power grid in real time.For power consumption, power lines are the transmission pipeline for electric energy, and for billing, power lines are the transmission and reception channel for power consumption data.Power lines achieve this dual function by taking advantage of the huge difference between power frequency (50 / 60 Hz) and high-frequency carrier communication frequency (0.78 MHz or higher).The communication module can easily separate the high-frequency carrier signal from the power line.

[0003] The power supply of the meter reading equipment is obtained from the power line, and there is no additional power supply interface.To make the meter reading equipment work normally, both power and communication signals must be provided, and to automate the network performance testing of the meter reading equipment, the power intensity of the communication signal must be programmable adjusted, which requires the use of a strong electric program attenuator that can pass through AC 220V strong current, high-frequency carrier signal, and programmable accurate adjustment of the amplitude of the high-frequency carrier signal.

[0004] Currently, high-frequency carrier communication network automation testing basically does not use strong electric high-frequency signal program attenuators, but modifies the tooling to separate the power line from the communication line, i.e., the twisted power line delivers electric energy, and the coaxial communication line transmits high-frequency carrier signals.This avoids the problem of strong and weak current sharing the same line, and only a normal weak electric high-frequency signal program attenuator is needed in the weak electric channel to adjust the signal intensity.Weak electric high-frequency signal program attenuators do not need to consider high voltage and large current, avoiding safety problems, as well as carrier signal and power isolation problems, signal leakage problems, and power load problems.

[0005] Although the method of separating strong and weak currents can complete automation performance testing, it requires two sets of testing solutions to test strong and weak items separately, and cannot complete all performance testing in one station.In addition, the weak electric channel is different from the strong electric channel, and after separating strong and weak currents, the weak electric channel becomes cleaner and more stable, so the test results tend to be ideal and deviate from reality.Based on this, a power line carrier communication signal program control attenuation device is proposed. UTILITY MODEL CONTENTS

[0006] The utility model aims at the problems in the background art, propose a kind of power line carrier communication signal program control attenuation device, solve the channel difference problem faced in power line carrier communication equipment test, twisted pair is replaced by coaxial cable, and the problem that weak electric program control attenuator cannot pass AC 220V current.

[0007] The utility model technical scheme

[0008] The utility model discloses a first aspect provides a kind of power line carrier communication signal program control attenuation circuit, comprising:

[0009] High-frequency signal isolator U1, U2;For high impedance to high-frequency signal, block high-frequency energy through;To power frequency low impedance, power frequency large current can pass through;

[0010] Balanced-unbalanced high-frequency isolation converter: U3, U5;Based on internal high-pass filter let high-frequency signal pass through, and the differential mode of twisted pair and the balanced mode of coaxial line are converted to each other;

[0011] High-frequency program control attenuator: U4;For according to external attenuation requirement, the access or bypass of internal attenuation unit is switched;

[0012] Power filter: U6;For cutting off the common mode, differential mode EMI interference generated by front and rear circuit;

[0013] Voltage transformer: U7;For AC 220V voltage reduction, provide working power supply for control circuit;

[0014] Controller: U8;For receiving external attenuation instruction by serial port, the access attenuation of high-frequency program control attenuator is controlled;

[0015] EMI filter: U9;For inhibiting the EMI interference brought by external serial port.

[0016] Preferably, the flow path of high-frequency carrier signal is:

[0017] The flow path of external power frequency current is:

[0018] The current path of working power supply is: 1-L / 1-L→U1→2-L / 2-N→U6→U7→U8, or 3-L / 3-N→U2→2-L / 2-N→U6→U7→U8.

[0019] Preferably, the high-frequency signal isolator includes independent inductance L1, L2, L3, L4, safety capacitor C1, C2, C3, C4, C5 and resistance R1;

[0020] The independent inductors L1, L2, L3 and L4 present high reactance to high frequency signals and block the high frequency signals from passing through;

[0021] The independent inductors L1, L2, L3 and L4 and the capacitors C1, C2, C3, C4 and C5 together form a low-pass filter; the high frequency signals leaked from the independent inductors L1, L2, L3 and L4 are bypassed to prevent the leakage to the next stage of the power grid; after the power grid is disconnected, the safety capacitor R1 is used to discharge the charge on the capacitor. Since two high frequency signal isolators are cascaded back-to-back, the total isolation degree is equal to the sum of the isolation degrees of the two isolators. If the maximum attenuation of the program-controlled attenuator is A dB, the total isolation degree should be greater than A+15 dB to improve the accuracy of the maximum attenuation value. In addition, the working power is taken from the signal isolation end, which does not affect the high frequency signal.

[0022] Preferably, the balanced-unbalanced high frequency isolation transformer includes safety capacitors C6, C7 and C8, a coupling transformer T1 and safety resistors R2 and R3.

[0023] The safety capacitors C6 and C7 together with the coupling transformer T1 form a high-pass filter to block the power frequency current and allow the high frequency carrier signal to pass directly; after the power grid is disconnected, the safety resistor R2 is used to discharge the charge on the safety capacitor;

[0024] The primary circuit of the transformer T1 adopts a balanced structure, and the secondary circuit adopts an unbalanced structure, which is used to convert the signal from differential mode to single-ended mode or from single-ended mode to differential mode. The high frequency signal isolator and the balanced-unbalanced high frequency isolation transformer both use ferrite cores, which have small insertion loss in the low frequency band and slightly larger insertion loss in the high frequency band. R3 and C8 are used for frequency equalization to adjust the insertion loss of the high and low frequency bands to be equal.

[0025] Preferably, the high frequency program-controlled attenuator is composed of N levels of program-controlled π attenuating units which are similar in form. The first level of program-controlled attenuating unit includes resistors R1, R3 and R5 to form a basic π attenuating unit. The input / output impedance of each π attenuating unit is equal. By switching through the relay, the π attenuating unit or the bypass is connected to achieve the purpose of adjusting the attenuation.

[0026] When working normally, if V ATT =L, the triode Q1 is cut off, the relay RY1 is released, the center contact o of the two switches JK1 and JK2 is connected to the a end, the signal is straight through, and the attenuation is 0; if V ATT=H, the triode Q1 is saturated and turned on, the relay RY1 is attracted, the center contact o of the two side switches JK1 and JK2 is connected to the b end, the signal is transmitted to the next stage through the π attenuator with the attenuation of x dB, the total attenuation is increased by x dB, and the total attenuation is equal to the sum of the attenuations of the N cascaded π attenuating units.

[0027] The second aspect of the utility model provides a kind of power line carrier communication signal program control attenuation device, using the power line carrier communication signal program control attenuation circuit described above, for the meter reading test test work of intelligent electric meter.

[0028] Compared with prior art, the utility model has the following beneficial technical effects:

[0029] 1, the utility model adopts 2 high-frequency signal isolators of back-to-back, extracts working power from middle isolation end, reduces mutual influence;

[0030] 2, the utility model adopts RC equalization circuit, and adjusts high-frequency and low-frequency access loss to be substantially equal.

[0031] 3, the utility model integrates strong current and high-frequency signal into one by strong current program control attenuator, and channel is closer to application in one station for carrier communication networking test.No additional access working power is needed, and no external interface is increased.Equipment is modular, structure is simple, and cost is lower. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is system architecture schematic diagram of the utility model;

[0033] Figure 2 It is circuit diagram of high-frequency signal isolator in the embodiment of the utility model;

[0034] Figure 3 It is circuit diagram of balanced-unbalanced high-frequency isolation converter in the embodiment of the utility model;

[0035] Figure 4 It is circuit diagram of single-stage program control attenuator in the embodiment of the utility model;

[0036] Figure 5 It is high-frequency signal isolator implementation example circuit diagram in the embodiment of the utility model;

[0037] Figure 6 It is balanced-unbalanced high-frequency isolation converter implementation example circuit diagram in the embodiment of the utility model;

[0038] Figure 7The utility model discloses embodiment high frequency program control attenuator implementation example circuit diagram. DETAILED DESCRIPTION

[0039] Embodiment 1

[0040] As Figure 1 The utility model provides a kind of power line carrier communication signal program control attenuation circuit, comprising:

[0041] High frequency signal isolator U1, U2;For high impedance to high frequency signal, block high frequency energy to pass through;For low impedance to power frequency, power frequency large current can pass through;

[0042] Balanced-unbalanced high frequency isolation converter: U3, U5;Based on internal high pass filter let high frequency signal pass through, and the differential mode of twisted pair line and the balanced mode of coaxial line are converted to each other;

[0043] High frequency program control attenuator: U4;For according to external attenuation amount requirement, the access or bypass of internal attenuation unit is switched;

[0044] Power filter: U6;For cutting off common mode, differential mode EMI interference generated by preceding and subsequent stage circuit;

[0045] Voltage transformer: U7;For AC 220V voltage reduction, provide working power supply for control circuit;

[0046] Controller: U8;For receiving external attenuation instruction through serial port, the access attenuation amount of high frequency program control attenuator is controlled;

[0047] EMI filter: U9;For inhibiting the EMI interference brought by external serial port.

[0048] In the embodiment, the flow path of high frequency carrier signal is: The flow path of external power frequency current is: The current path of working power supply is: 1-L / 1-L→U1→2-L / 2-N→U6→U7→U8, or 3-L / 3-N→U2→2-L / 2-N→U6→U7→U8.

[0049] As Figure 2As shown, the high-frequency signal isolator includes independent inductors L1, L2, L3, L4, safety capacitors C1, C2, C3, C4, C5 and resistor R1; the independent inductors L1, L2, L3, L4 present high reactance to high-frequency signals and block the high-frequency signals from passing through; the safety capacitor C1 is an X capacitor, and the safety capacitors C2, C3, C4, C5 are Y capacitors; the independent inductors L1, L2, L3, L4 and the capacitors C1, C2, C3, C4, C5 together form a low-pass filter; the high-frequency signals leaked from the independent inductors L1, L2, L3, L4 are bypassed to prevent the leakage to the next stage of the power grid; after the power grid is disconnected, the safety resistor R1 is used to discharge the charge on the capacitors. Since two high-frequency signal isolators are cascaded back-to-back, the total isolation degree is equal to the sum of the isolation degrees of the two isolators, and if the maximum attenuation of the program-controlled attenuator is AdB, the total isolation degree should be greater than A+15dB to improve the accuracy of the maximum attenuation value. In addition, the working power is taken from the signal isolation end, which will not affect the high-frequency signals.

[0050] As shown in Figure 3 , the balanced-unbalanced high-frequency isolation converter includes safety capacitors C6, C7, C8, a coupling transformer T1 and safety resistors R2, R3; the safety capacitors C6, C7 and the coupling transformer T1 together form a high-pass filter to block the power frequency current and allow the high-frequency carrier signal to pass directly; after the power grid is disconnected, the safety resistor R2 is used to discharge the charge on the safety capacitors; the primary circuit of the transformer T1 adopts a balanced structure, and the secondary circuit is an unbalanced structure, which is used to convert the signal from differential mode to single-ended mode or from single-ended mode to differential mode. The high-frequency signal isolator and the balanced-unbalanced high-frequency isolation converter both use ferrite cores, which have small insertion loss in the low-frequency band and slightly larger insertion loss in the high-frequency band. R3 and C8 are used for frequency equalization to adjust the insertion loss of the high-frequency band and the low-frequency band to be equal.

[0051] As shown in Figure 4 , the high-frequency program-controlled attenuator is formed by cascading N stages of similar program-controlled π attenuating units. The first stage of the program-controlled attenuating unit includes resistors R1, R3 and R5 to form a basic π attenuating unit. The input / output impedance of each π attenuating unit is equal. By switching through a relay, the π attenuating unit or a bypass is connected to achieve the purpose of adjusting the attenuation.

[0052] When working normally, if V ATT = L, the triode Q1 is cut off, the relay RY1 is released, the center contact o of the two switches JK1 and JK2 is connected to the a terminal, the signal is directly passed through, and the attenuation is 0; if V ATT=H, the triode Q1 is saturated and turned on, the relay RY1 is attracted, the center contact o of the two side switches JK1 and JK2 is connected to the b end, the signal is transmitted to the next stage through a π attenuator with an attenuation of x dB, the total attenuation is increased by x dB, and the total attenuation is equal to the sum of the attenuations of all N cascaded π attenuating units. Due to the existence of the distributed parameters, the attenuation of the high frequency band is slightly larger than that of the low frequency band (about 0.1-0.2 dB), and R4 and C1 are used for frequency equalization to reduce the attenuation value of the high frequency band, so that the attenuation values of the low frequency band are equal.

[0053] The scheme is described in detail below by using a specific case:

[0054] The specific implementation circuit of the scheme comprises three key parts: a high-frequency signal isolator as shown in Figure 5 , a balanced-unbalanced high-frequency isolation transformer as shown in Figure 6 , and a high-frequency program-controlled attenuator as shown in Figure 7 .

[0055] 1) High-frequency signal isolator

[0056] Single-stage isolation degree: > 46 dB at 0.5 MHz;

[0057] Access loss: 0.3 dB at 0.5 MHz, 1.5 dB at 10 MHz;

[0058] 2) Balanced-unbalanced high-frequency isolation transformer

[0059] Insertion loss: 0.2 dB at 0.5 MHz, 0.6 dB at 10 MHz;

[0060] Balanced loss: 1.7 dB.

[0061] 3) Program-controlled attenuator

[0062] Attenuation accuracy: after optimizing the program-controlled combination of π attenuating units, single-stage ± 0.25 dB, 8-stage ± 0.5 dB;

[0063] 3.3V signal relay attraction current: 56mA / 3.3V.

[0064] In this embodiment, the strong current program-controlled attenuator combines the strong current and the high-frequency signal, and the carrier communication networking test is completed in one station, and the channel is closer to the application. No additional working power supply is needed, and no external interface is added. The device is modularized, the structure is simple, and the cost is low.

[0065] Embodiment 2

[0066] The utility model provides a kind of power line carrier communication signal program-controlled attenuation device, uses the power line carrier communication signal program-controlled attenuation circuit of embodiment 1, for the meter reading test test work of intelligent electric meter.

[0067] The embodiment adopts two back-to-back high-frequency signal isolators, extracts working power from the middle isolation end, and reduces mutual influence; and adopts an RC equalization circuit to adjust the high-frequency and low-frequency insertion loss to be substantially equal.

[0068] The above has made detailed description on the embodiment of the utility model in combination with the drawings, but the utility model is not limited to this, within the knowledge range possessed by the technical personnel in the technical field, various changes can also be made without departing from the purpose of the utility model.

Claims

1. A programmable attenuation circuit for power line carrier communication signals, characterized in that, include: High-frequency signal isolators U1 and U2 are used to present high impedance to high-frequency signals, blocking high-frequency energy from passing through; and to present low impedance to power frequency signals, allowing large power frequency currents to pass through. Balanced-to-unbalanced high-frequency isolation converters: U3, U5; based on an internal high-pass filter, high-frequency signals are allowed to pass through, and the differential mode of twisted-pair cable and the balanced mode of coaxial cable are converted to each other; High-frequency programmable attenuator: U4; used to switch the access or bypass of the internal attenuation unit according to the external attenuation requirements; Power filter: U6; used to isolate common-mode and differential-mode EMI interference generated by the preceding and following circuits; Voltage transformer: U7; used to step down AC 220V to provide operating power for the control circuit; Controller: U8; used to receive external attenuation commands via serial port and control the attenuation of the high-frequency programmable attenuator. EMI filter: U9; used to suppress EMI interference from external serial ports.

2. The power line carrier communication signal programmable attenuation circuit according to claim 1, characterized in that, The path through which the high-frequency carrier signal flows is:

3. The power line carrier communication signal programmable attenuation circuit according to claim 1, characterized in that, The path of the external power frequency current is:

4. The power line carrier communication signal programmable attenuation circuit according to claim 1, characterized in that, The current path of the working power supply is: 1-L / 1-N→U1→2-L / 2-N→U6→U7→U8, or 3-L / 3-N→U2→2-L / 2-N→U6→U7→U8.

5. The power line carrier communication signal programmable attenuation circuit according to claim 1, characterized in that, The high-frequency signal isolator includes independent inductors L1, L2, L3, L4, safety capacitors C1, C2, C3, C4, C5, and resistor R1. Independent inductors L1, L2, L3, and L4 exhibit high reactance to high-frequency signals, thus blocking the passage of high-frequency signals; Safety capacitor C1 is an X capacitor, and safety capacitors C2, C3, C4, and C5 are Y capacitors. Independent inductors L1, L2, L3, and L4, together with capacitors C1, C2, C3, C4, and C5, form a low-pass filter. This filter bypasses high-frequency signals leaking from independent inductors L1, L2, L3, and L4, preventing leakage to the next stage of the power grid. After the power grid is disconnected, safety resistor R1 is used to discharge the charge on the capacitors.

6. The power line carrier communication signal programmable attenuation circuit according to claim 1, characterized in that, The balanced-to-unbalanced high-frequency isolation converter includes safety capacitors C6, C7, and C8, coupling transformer T1, and safety resistors R2 and R3. Safety capacitors C6 and C7, together with coupling transformer T1, form a high-pass filter to block power frequency current and allow high-frequency carrier signals to pass directly; after the power grid is disconnected, safety resistor R2 is used to discharge the charge on the safety capacitors. The primary circuit of transformer T1 adopts a balanced structure, while the secondary circuit adopts an unbalanced structure, which is used to convert signals from differential mode to single-ended mode, or from single-ended mode to differential mode.

7. The power line carrier communication signal programmable attenuation circuit according to claim 1, characterized in that, The high-frequency programmable attenuator is composed of N cascaded programmable π attenuation units with similar shapes. The first-stage programmable attenuation unit consists of resistors R1, R3, and R5 forming a basic π attenuation unit. The input / output impedance of each π attenuation unit is equal. By switching the relay, the π attenuation unit can be connected or bypassed to achieve the purpose of adjusting the attenuation. During normal operation, if V ATT =L, transistor Q1 is cut off, relay RY1 is released, the center contact o of switches JK1 and JK2 on both sides is connected to terminal a, the signal is directly connected, and the attenuation is 0; if V ATT =H, transistor Q1 is saturated and conducting, relay RY1 is energized, the center contact o of switches JK1 and JK2 on both sides is connected to terminal b, the signal is transmitted to the next stage through a π-type attenuator with an attenuation of x dB, the total attenuation increases by x dB, and the total attenuation is equal to the sum of the attenuation of all N cascaded π-type attenuation units.

8. A programmable attenuation device for power line carrier communication signals, characterized in that, The power line carrier communication signal programmable attenuation circuit according to any one of claims 1-7 is used in the meter reading test of smart meters.

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