Communication isolation circuit, electric energy meter and radiation rectification method of electric energy meter

Abstract

The application discloses a communication isolation circuit, an electric energy meter and a radiation rectification method of the electric energy meter, and is suitable for the electric energy meter. The communication isolation circuit comprises an isolation chip, an input matching unit, an output matching unit, an input bias unit and an output bias unit. The input matching unit is used for impedance matching of signals input into the isolation chip of a metering unit. The output matching unit is used for impedance matching of signals input into a management unit of the isolation chip. The input bias unit comprises a first bias resistor. The output bias unit comprises a second bias resistor. By adding and improving the communication isolation circuit in the electric energy meter, the radiation problem caused by the electric energy meter in the communication process is suppressed from the source. The electric energy meter using the radiation rectification method provided by the application changes the disadvantages of the traditional trial-and-error method of blind rectification, and realizes accurate positioning and efficient solution of the radiation interference.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic compatibility technology for smart meters, and in particular to an SPI communication isolation circuit suitable for smart meters, a power meter including the circuit, and a method for rectifying radiation interference from power meters. Background Technology

[0002] Currently, the industry generally adopts a traditional trial-and-error method to rectify excessive SPI radiation in electricity meters. This involves repeatedly debugging by blindly adding ferrite beads, filtering devices, and adjusting device parameters, which has many drawbacks: First, it lacks precise interference location methods, resulting in blind rectification, long R&D cycles, and high testing costs; second, it does not optimize for defects in the signal itself, ignoring overshoot and ringing issues of high-speed signals, and failing to suppress high-frequency harmonic radiation at the source; third, it lacks crosstalk protection solutions adapted to the long wiring structure of electricity meters, and crosstalk between lines further aggravates excessive radiation; fourth, conventional rectification methods have insufficient margin, making it difficult to meet the 5dB standard requirement, resulting in a low product mass production pass rate. Summary of the Invention

[0003] This invention provides a communication isolation circuit, an energy meter, and a radiation rectification method. The purpose is to solve the problems of excessive radiation interference and blind and inefficient rectification in the scenario of long-line SPI communication of energy meters. It aims to suppress high-frequency radiation from the signal source and build a closed-loop rectification process, thereby significantly improving rectification efficiency and compliance rate.

[0004] This invention provides a communication isolation circuit suitable for use in electricity meters, comprising an isolation chip, an input matching unit, an output matching unit, an input bias unit, and an output bias unit; An input matching unit is disposed between the metering unit of the energy meter and the input side of the isolation chip, adjacent to the signal output pin of the metering unit, and is used to perform impedance matching on the signal input from the metering unit to the isolation chip; An output matching unit is disposed between the management unit of the energy meter and the output side of the isolation chip, and is used to perform impedance matching on the signal input from the isolation chip to the management unit; The input bias unit includes a first bias resistor, which is located between a first power supply and a first enable pin of the isolation chip. The output bias unit includes a second bias resistor between the second power supply and the second enable pin of the isolation chip.

[0005] In some embodiments, the input matching unit includes a plurality of input matching circuits; Each of the input matching circuits includes an input matching resistor and an input matching capacitor; The first end of each input matching resistor is connected to a communication data port of the metering unit, and the second end of the input matching resistor is connected to the input pin of the isolation chip. The first end of each input matching capacitor is connected to the connection node between the input matching resistor and the input pin of the isolation chip, and the second end of the input matching capacitor is grounded.

[0006] In some embodiments, the output matching unit includes a plurality of output matching circuits, each output matching circuit including an output matching resistor, the first end of each output matching resistor being connected to an output pin of the isolation chip, and the second end being connected to a communication data port of the management unit.

[0007] In some embodiments, the input matching circuit includes a common-mode choke connected in series on the signal line of the communication data port between the metering unit and the isolation chip; or connected in series on the signal line of the communication data port between the management unit and the isolation chip.

[0008] In some embodiments, when wiring the communication isolation circuit, ground copper foil is laid on both sides of the signal line of the communication data port and on adjacent layers, and the ground copper foil is connected to the inner layer ground plane through spaced grounding vias.

[0009] In some embodiments, the communication isolation circuit adopts a four-layer stacked structure of top layer, first inner layer, second inner layer and bottom layer during wiring. The signal lines of the communication data port are laid on the top layer, and the first inner layer and the second inner layer are used as reference return planes.

[0010] In some embodiments, the communication isolation circuit further includes an input power supply unit and an output power supply unit; An input power supply unit is disposed between the metering unit of the energy meter and the input side of the isolation chip, including at least one first current-limiting resistor and at least one first decoupling capacitor; the first end of the first current-limiting resistor is connected to the first power supply, and the second end of the first current-limiting resistor is connected to the first power supply pin of the isolation chip; at least one first decoupling capacitor is connected in parallel between the first current-limiting resistor and ground. An output power supply unit is disposed between the management unit of the energy meter and the output side of the isolation chip, and includes at least one second current-limiting resistor and at least one second decoupling capacitor; the second end of the second current-limiting resistor is connected to the second power supply, and the first end of the second current-limiting resistor is connected to the second power supply pin of the isolation chip; at least one second decoupling capacitor is connected in parallel between the second current-limiting resistor and ground.

[0011] This application embodiment also provides an energy meter, including a metering unit and a management unit, and further including a first communication circuit and a second communication circuit; The first communication circuit is connected to the output terminal of the metering unit and the input terminal of the management unit, and is used to transmit the signal output by the metering unit to the management unit. The second communication circuit is connected to the output terminal of the metering unit and the input terminal of the management unit, and is used to transmit the signal output by the metering unit to the management unit; At least one of the first communication circuit and the second communication circuit is the communication isolation circuit described in any of the above embodiments, the input matching unit is disposed between the metering unit and the input side of the isolation chip, and the output matching unit is disposed between the management unit and the output side of the isolation chip.

[0012] This application also provides a method for rectifying radiation from an electricity meter, applicable to the electricity meter described in the above embodiments, including: An oscilloscope was used to measure the energy meter to determine whether there were overshoot and ringing defects in the signal waveform, and the signal integrity parameters were recorded. When the signal waveform exhibits overshoot and ringing, a spectrum analyzer is used in conjunction with a near-field probe to scan and pinpoint the specific location of the radiated interference source. Based on the signal integrity defects and interference source location results, a target rectification plan is formulated, which includes adjusting the position of the matching resistor, optimizing its parameters, and processing the signal line ground wrap. The electricity meter is rectified based on the target rectification plan until the remeasured signal waveform and near-field radiation intensity both meet the preset threshold. The energy meter that meets the preset threshold is sent into an anechoic chamber for full-band radiation interference test verification.

[0013] This invention provides a communication isolation circuit, an electricity meter, and a radiation mitigation method. By adding and improving the isolation circuit within the electricity meter, the radiation problem caused by the electricity meter during communication is suppressed at its source. Compared with the prior art, this invention has the following advantages: Source-end matching design suppresses radiation at the source: By setting the input matching unit close to the SPI signal output pin of the metering unit, source-end impedance matching is completed before the signal enters the long trace, effectively offsetting the signal reflection caused by impedance discontinuity of the long trace. This can reduce the SPI signal overshoot rate from more than 40% to less than 15%, fundamentally weakening the generation of 70MHz~100MHz high-frequency harmonics, which is different from the failure design of traditional isolation chip end or load end matching.

[0014] End-to-end collaborative optimization for long-trace scenarios: A multi-dimensional collaborative solution is adopted, including source impedance matching, signal line ground shielding, and a complete reference ground plane. This not only suppresses signal self-reflection but also blocks crosstalk between lines and reduces the radiation loop area. It is perfectly adapted to the working conditions where the overall structure of the electricity meter is limited and the SPI traces are long. After the rectification, the radiation interference is reserved with a safety margin of more than 5dB, which meets the electricity meter standards.

[0015] The closed-loop rectification method significantly improves efficiency: It establishes a closed-loop rectification process that includes oscilloscope signal integrity diagnosis, spectrum analyzer near-field interference localization, targeted rectification, and dual-dimensional verification iteration. It establishes a mapping relationship between signal defects and radiated interference, replacing the traditional blind trial and error method. This can reduce the number of anechoic chamber tests by more than 60%, significantly shorten the rectification cycle, and reduce R&D testing costs.

[0016] Low cost and high compatibility: All rectification measures only involve the adjustment of passive component parameters and optimization of PCB layout, without increasing additional material costs, and retain the maximum communication rate of 6Mbps and multi-level sampling function throughout the process, without affecting the metering accuracy and data transmission stability, and have strong mass production adaptability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of a communication isolation circuit in one embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of an electricity meter in one embodiment of the present invention.

[0020] Figure 3 This is a flowchart of a radiation rectification method for an electricity meter in one embodiment of the present invention.

[0021] Figure 4 This is a waveform diagram before radiation rectification in one embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram of the waveform after radiation rectification in one embodiment of the present invention.

[0023] Figure 6 This is a near-field spectral scan spectrum before radiation rectification in one embodiment of the present invention.

[0024] Figure 7 This is a near-field spectral scan spectrum after radiation rectification in one embodiment of the present invention.

[0025] Figure 8 This is an actual test spectrum of radiation interference of the device before radiation rectification in one embodiment of the present invention.

[0026] Figure 9 This is an actual test spectrum of radiation interference of the device after radiation rectification in one embodiment of the present invention.

[0027] In the figure, 10 is the input matching unit; 20 is the output matching unit; 11 is the input bias unit; 21 is the output bias unit; 12 is the input matching circuit; 22 is the output matching circuit; 13 is the input power supply unit; 23 is the output power supply unit; 1 is the metering unit; 2 is the management unit; 3 is the first communication circuit; and 4 is the second communication circuit. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0029] This invention provides a communication isolation circuit suitable for use within electricity meters, such as... Figure 1 As shown, it includes an isolation chip U1, an input matching unit 10, an output matching unit 20, an input bias unit 11, and an output bias unit 21; An input matching unit 10 is disposed between the metering unit 1 of the energy meter and the input side of the isolation chip U1, adjacent to the signal output pin of the metering unit 1, and is used to perform impedance matching on the signal input from the metering unit 1 to the isolation chip U1. The output matching unit 20 is disposed between the management unit 2 of the energy meter and the output side of the isolation chip U1, and is used to perform impedance matching on the signal input from the isolation chip U1 to the management unit 2. The input bias unit 11 includes a first bias resistor R1, which is located between the first power supply VOP and the first enable pin ENA of the isolation chip U1. The output bias unit 21 includes a second bias resistor R2, which is located between the second power supply SVCC and the second enable pin ENB of the isolation chip U1.

[0030] In one example, the communication isolation circuit mainly includes an isolation chip U1, an input matching unit 10, and an output matching unit 20. The isolation chip U1 is responsible for providing electrical isolation while transmitting signals between the metering unit 1 and the management unit 2, in order to meet the safety requirements of the electricity meter.

[0031] The input matching unit 10 is positioned between the metering unit 1 and the input side of the isolation chip U1. It performs source-end impedance matching processing on the signal output from the metering unit 1, ensuring impedance adjustment is completed before the signal enters the isolation chip U1. Unlike traditional designs where the matching network is placed arbitrarily or at the rear end of the isolation chip U1, this approach intervenes in signal control from the source, effectively absorbing reflected energy caused by impedance discontinuities in long traces, reducing signal edge steepness, and thus suppressing signal integrity issues such as overshoot and ringing.

[0032] The output matching unit 20 is located between the output side of the isolation chip U1 and the management unit 2. It is used to perform secondary impedance matching on the signal after isolation transmission to ensure that the signal is well matched with the impedance of the load end when it enters the interface of the management unit 2, so as to avoid signal distortion and additional radiation caused by terminal reflection or capacitive load mismatch.

[0033] By setting an input matching unit 10 between the metering unit 1 and the isolation chip U1, and setting an output matching unit 20 between the isolation chip U1 and the management unit 2, impedance matching of the communication signal can be performed, which can effectively reduce signal reflection caused by the discontinuity of the wiring impedance, suppress overshoot and ringing from the source, reduce high-frequency harmonic radiation energy, provide a basic circuit structure for the electromagnetic compatibility of the electricity meter, and does not increase the cost of additional components.

[0034] The communication isolation circuit also includes an input bias unit 11 and an output bias unit 21 to ensure stable chip operation and suppress level noise. The input bias unit 11 includes at least one first bias resistor R1, which is connected in series between the first power supply VOP and the first enable pin ENA of the isolation chip U1; the output bias unit 21 includes at least one second bias resistor R2, which is connected in series between the second power supply SVCC and the second enable pin ENB.

[0035] By setting the input bias unit 11 and output bias unit 21, which are composed of resistors, the enable pin of the isolation chip U1 is fixed at a certain level, preventing logic indeterminacy and functional abnormality caused by the pin being floating, and ensuring stable and reliable operation of the circuit during power-on and operation.

[0036] In some embodiments, the input matching unit 10 includes a plurality of input matching circuits 12; Each of the input matching circuits 12 includes an input matching resistor R3 and an input matching capacitor C1; The first end of each input matching resistor R3 is connected to a communication data port of the metering unit 1, and the second end of the input matching resistor R3 is connected to the input pin of the isolation chip U1. The first end of each input matching capacitor C1 is connected to the connection node between the input matching resistor R3 and the input pin of the isolation chip U1, and the second end of the input matching capacitor C1 is grounded.

[0037] In one example, each input matching circuit 12 in the input matching unit 10 includes not only a series-connected input matching resistor R3, but also an input matching capacitor C1 connected in parallel between the second terminal of the input matching resistor R3 and ground, forming an RC filter combination. As an example, each of the three input matching resistors R3 is connected in series between a communication data port and an input pin of an isolation chip U1. For example, one input matching resistor R3 is connected in series between the input terminal EX_HSCLK and input pin VI1 of the communication data port, between the input terminal EX_HSMOSI and input pin VI2 of the communication data port, and between the input terminal EX_HSCS and input pin VI3 of the communication data port. The three input matching capacitors C1 are then connected in parallel between each input matching resistor R3 and ground, forming three sets of RC filter combinations.

[0038] The purpose of introducing the input matching capacitor C1 is to form a filter network in conjunction with the resistor, which can more directly bypass and attenuate the high-frequency components at the signal edges. Compared with the circuit configuration of pure resistors, the RC filter combination can more finely control the high-frequency impedance characteristics, further suppress harmonic radiation caused by steep edges, and has a certain degree of attenuation effect on both common-mode and differential-mode noise.

[0039] By adding several input matching resistors R3 and input matching capacitors C1 to the input matching circuit 12, several RC low-pass filter networks are formed, which can selectively filter out high-frequency components at the signal edges, further eliminate signal overshoot and ringing defects, and improve the targeting and accuracy of radiation interference suppression.

[0040] In some embodiments, the output matching unit 20 includes a plurality of output matching circuits 22, each output matching circuit 22 including an output matching resistor R4, the first end of each output matching resistor R4 being connected to the output pin of the isolation chip U1, and the second end being connected to a communication data port of the management unit 2.

[0041] In one example, the output matching unit 20 includes a plurality of output matching resistors R4. The first end of each output matching resistor R4 is connected to an output pin of the isolation chip U1, and the second end is connected to the output of the corresponding communication data port. In one example, the three output matching resistors R4 are connected in series between the output pin EXT_SPICLK of the communication data port and the output pin VO1, between the output pin EXT_SPIMOSI of the communication data port and the output pin VO2, and between the output pin EXT_SPICS of the communication data port and the output pin VO3, respectively.

[0042] By adding an output matching circuit 22 to the output side of the isolation chip U1, the residual signal reflection after long-line transmission is absorbed, preventing signal resonance at the communication data port corresponding to the management unit 2 and avoiding secondary high-frequency harmonics. This enables the signal path between the output side of the isolation chip U1 and the management unit 2 to have adjustable impedance matching capability, which can be flexibly adjusted according to the actual load characteristics, avoiding secondary reflections caused by output impedance mismatch, and further consolidating the integrity of the overall signal link and its anti-radiation performance.

[0043] In some embodiments, the input matching circuit 12 includes a common-mode choke, which is connected in series on the signal line of the communication data port between the metering unit 1 and the isolation chip U1; or connected in series on the signal line of the communication data port between the management unit and the isolation chip U1.

[0044] In one example, the radiation suppression effect can be further enhanced by adding a common-mode choke. Specifically, a common-mode choke is inserted in series on the signal line of the communication data port between isolation chip U1 and metering unit 1, or on the signal line of the communication data port between isolation chip U1 and management unit 2. The common-mode choke can provide high impedance while ensuring the normal passage of data signals, thereby blocking the flow of common-mode current and effectively suppressing electromagnetic radiation.

[0045] In some embodiments, when wiring the communication isolation circuit, ground copper foil is laid on both sides of the signal line of the communication data port and on adjacent layers, and the ground copper foil is connected to the inner layer ground plane through spaced grounding vias.

[0046] In one example, when implementing a grounding design for communication isolation circuits on the PCB, ground copper foil of a certain width needs to be laid parallel to both sides of the signal line, maintaining a constant distance from the signal line. For example, the distance between the signal line and the ground copper foil should be 2 to 3 times the width of the signal line. Ground copper foil should also be laid in the corresponding area of ​​the adjacent signal layer, thereby forming a semi-enclosed or fully enclosed grounding shield cavity around the signal line. Grounding vias are placed along the edge of the ground copper foil at certain intervals (e.g., adjustable within the range of 4mm to 6mm depending on the PCB space) to reliably connect the ground copper foil to the inner complete ground plane.

[0047] By grounding the signal lines of the communication data port, laying ground copper foil on both sides and adjacent layers of the signal lines and grounding through vias, electromagnetic crosstalk between long traces can be effectively suppressed, radiation sources can be isolated, and the antenna effect of the traces can be reduced. It is particularly suitable for working conditions where the structure of the energy meter is limited and the traces are long, and it greatly reduces the high-frequency radiation exceeding the standard caused by crosstalk superposition.

[0048] In some embodiments, the communication isolation circuit adopts a four-layer stacked structure of top layer, first inner layer, second inner layer and bottom layer during wiring. The signal lines of the communication data port are laid on the top layer, and the first inner layer and the second inner layer are used as reference return planes.

[0049] In one example, a four-layer board stack can be used in the circuit routing design of the communication isolation circuit: a top layer, a first inner layer, a second inner layer, and a bottom layer. The top layer is the top signal layer, the first inner layer is a complete ground plane, the second inner layer is the power and auxiliary ground plane, and the bottom layer is the bottom signal layer. All critical signal lines, such as EX_HSCLK, EX_CLK2, and EX_HSMOSI, are preferentially placed on the top layer, with the first and second inner layers serving as reference return planes. This design utilizes the mirror plane effect: when signal current flows along the top layer trace, its return current concentrates on the path directly below the trace in the ground plane. The electromagnetic fields formed by these two currents cancel each other out, compressing the equivalent radiation loop area to the board thickness scale, thereby significantly reducing differential mode radiation efficiency. Other low-speed control signals or non-critical signals can be placed on the bottom layer. Furthermore, parameters such as the spacing between layers and the dielectric constant can be conventionally controlled according to the target characteristic impedance to ensure signal consistency. This four-layer stack-up scheme, together with the aforementioned ground plane treatment and matching resistor arrangement, can construct a comprehensive radiation suppression system from the physical layer to the circuit layer of a single board.

[0050] In some embodiments, the communication isolation circuit further includes an input power supply unit 13 and an output power supply unit 23; The input power supply unit 13 is disposed between the metering unit 1 of the energy meter and the input side of the isolation chip U1, and includes at least one first current-limiting resistor R5 and at least one first decoupling capacitor C2; the first end of the first current-limiting resistor R5 is connected to the first power supply VOP, and the second end of the first current-limiting resistor R5 is connected to the first power supply pin VDDA of the isolation chip U1; at least one first decoupling capacitor C2 is connected in parallel between the first current-limiting resistor R5 and ground; The output power supply unit 23 is located between the management unit 2 of the energy meter and the output side of the isolation chip U1, and includes at least one second current-limiting resistor R6 and at least one second decoupling capacitor C3; the second end of the second current-limiting resistor R6 is connected to the second power supply SVCC, and the first end of the second current-limiting resistor R6 is connected to the second power supply pin VDDB of the isolation chip U1; at least one second decoupling capacitor C3 is connected in parallel between the second current-limiting resistor R6 and ground.

[0051] In one example, the communication isolation circuit also includes an input power supply unit 13 and an output power supply unit 23 for supplying power to the communication isolation circuit. The input power supply unit 13 and the output power supply unit 23 are located at the power supply pins on the input and output sides of the isolation chip U1, respectively.

[0052] When the isolation chip U1 is working normally, its power supply pins consume a certain amount of transient current, especially during the transition of digital signals, which can cause high-frequency current surges. If the impedance of the power distribution network is not low enough, high-frequency voltage ripples can easily be generated on the power lines. These ripples may couple into the signal path and affect signal quality, or they may radiate outwards through the power lines themselves. Therefore, it is necessary to set up an input power supply unit 13 and an output power supply unit 23 on both sides of the isolation chip U1 to filter out radiated interference while ensuring normal operation.

[0053] The input power supply unit 13 is located on the input side of the metering unit 1 and mainly consists of a first current-limiting resistor R5 and several first decoupling capacitors C2. As an example, the first end of the first current-limiting resistor R5 is connected to the first power supply VOP, and the second end is connected to the first power supply pin VDDA of the isolation chip U1. The first decoupling capacitor C2 is connected in parallel between the first power supply pin VDDA and ground. Specifically, one end of the first decoupling capacitor C2 is connected to the second end of the first current-limiting resistor R5, and the other end is grounded, forming a filter network for filtering and stabilization. Similarly, the output power supply unit 23 is located on the input side of the management unit 2 and mainly consists of a second current-limiting resistor R6 and several second decoupling capacitors C3. As an example, the second current-limiting resistor R6 is connected in series between the second power supply SVCC and the second power supply pin VDDB of the isolation chip U1, and the second decoupling capacitor C3 is connected in parallel between the second power supply pin VDDB and ground. Specifically, one end of the second decoupling capacitor C3 is connected to the second end of the second current-limiting resistor R6, and the other end is grounded, forming a filter network for filtering and stabilization.

[0054] By adding an input power supply unit 13 and an output power supply unit 23, which consist of a current-limiting resistor and a decoupling capacitor, high-frequency noise in signal transmission can be effectively filtered out, ripple interference on the power supply pin of the isolation chip U1 can be reduced, power supply noise can be prevented from coupling to the signal channel, and the signal quality and anti-interference capability of the communication circuit can be further improved.

[0055] This application also provides an electricity meter, such as... Figure 2 As shown, it includes a metering unit 1 and a management unit 2, as well as a first communication circuit 3 and a second communication circuit 4; The first communication circuit 3 is connected to the output terminal of the metering unit 1 and the input terminal of the management unit 2, and is used to transmit the signal output by the metering unit 1 to the management unit 2. The second communication circuit 4 is connected to the output terminal of the metering unit 1 and the input terminal of the management unit 2, and is used to transmit the signal output by the metering unit 1 to the management unit 2. At least one of the first communication circuit 3 and the second communication circuit 4 is the communication isolation circuit described in any of the above embodiments. The input matching unit 10 is disposed between the input side of the metering unit 1 and the isolation chip U1, and the output matching unit 20 is disposed between the management unit 2 and the output side of the isolation chip U1.

[0056] In traditional electricity meter designs, the lack of proper impedance matching and the placement of the matching network far from the signal drive source cause severe reflections due to impedance discontinuities during long-distance signal transmission, leading to overshoot and ringing. This results in the electricity meter exhibiting severely excessive radiated interference during electromagnetic compatibility certification testing.

[0057] As an example, the electricity meter provided in this embodiment includes: a metering unit 1, a management unit 2, a first communication circuit 3, and a second communication circuit 4. The first communication circuit 3 is connected between the metering unit 1 and the management unit 2, and is used to transmit the signal output by the metering unit 1 to the management unit 2; the second communication circuit 4 is also connected between the metering unit 1 and the management unit 2, and can undertake the data transmission task of another signal.

[0058] At least one of the first communication circuit 3 and the second communication circuit 4 employs a communication isolation circuit as described in any of the above embodiments, namely, a complete communication isolation circuit including an isolation chip U1, an input matching unit 10, and an output matching unit 20. Specifically, the input matching unit 10 in this communication isolation circuit is positioned as an integral functional module between the metering unit 1 and the input side of the isolation chip U1, and its physical location is configured near the signal drive pin of the metering unit 1, thereby completing source-end impedance matching before the signal enters the long trace and the isolation chip U1. The output matching unit 20, as an integral functional module, is positioned between the output side of the isolation chip U1 and the management unit 2, performing secondary impedance matching on the isolated signal. Simultaneously, in the PCB layout of the energy meter, grounding is applied to the signal lines, current-limiting resistors and decoupling capacitors are configured in the power supply circuit of the isolation chip U1, and the enable pin is fixed at a certain level through a bias resistor, forming a full-link signal integrity and electromagnetic compatibility optimization system from the signal source to the load.

[0059] By employing the aforementioned communication isolation circuit, the energy meter provided in this example can resolve overshoot and ringing issues caused by reflections from long traces, suppress high-frequency harmonic radiation, and significantly reduce radiated interference in this frequency band. Furthermore, the entire optimization scheme involves only adjustments to the PCB layout and reasonable additions or subtractions of passive resistors and capacitors, without involving expensive materials or structural changes. Hardware costs remain virtually unchanged, manufacturability is high, and it fully meets the economic requirements for mass production.

[0060] This application also provides a method for rectifying radiation from an electricity meter, applicable to the electricity meters described in the above embodiments, such as... Figure 3 As shown, it includes: S1: Use an oscilloscope to measure the electricity meter, determine whether there are overshoot and ringing defects in the signal waveform, and record the signal integrity parameters; S2: When the signal waveform exhibits overshoot and ringing, a spectrum analyzer is used in conjunction with a near-field probe to scan and locate the specific position of the radiated interference source. S3: Based on the signal integrity defects and interference source location results, formulate a target rectification plan, which includes adjusting the position of the matching resistor, optimizing parameters, and grounding the signal line. S4: Based on the target rectification plan, rectify the electricity meter until the remeasured signal waveform and near-field radiation intensity both meet the preset threshold. S5: The energy meter that meets the preset threshold is sent into an anechoic chamber for full-band radiation interference test verification.

[0061] As an example, in step S1, an oscilloscope with a high-impedance active probe is used to reduce the load effect. The signal waveforms of each communication data port on the energy meter are sequentially probed, with particular attention paid to high-speed signals such as EX_HSCLK, EX_HSMOSI, and EX_HSCS. The waveforms are observed for obvious overshoot and ringing phenomena, with particular attention to recording the overshoot amplitude, ringing duration, and frequency. Using a high-impedance active oscilloscope probe, the SPI interface pins of the metering MCU (EX_HSCLK, EX_HSMOSI, EX_HSCS, etc.) are sequentially probed, acquiring signal waveforms and recording parameters such as rising edge, falling edge, overshoot amplitude, and ringing period to determine if overshoot and ringing defects exist. In this embodiment, the preset overshoot threshold is 15%. If the positive overshoot exceeds 15%, it is determined that a signal integrity defect exists. Due to the high signal communication rate and steep edges, if signal integrity problems exist, such as... Figure 4 As shown, it often manifests as damped oscillations near the rising or falling edge in the time domain.

[0062] As an example, in step S2, after confirming the presence of signal overshoot or ringing, a spectrum analyzer is activated and a near-field probe is connected. The resolution bandwidth is set to a small value to obtain higher sensitivity. The near-field probe scans each area of ​​the energy meter sequentially. After confirming the existence of signal integrity defects, the spectrum analyzer is used in conjunction with the near-field probe, setting the scanning frequency band to 30MHz~1GHz, focusing on the 70MHz~100MHz band, and scanning the MCU area, isolation chip U1 area, SPI trace path, and management unit 2 interface area of ​​the PCB board one by one. By comparing the radiation field strength amplitude of each area, the specific location of the strongest radiation is located, the main interference source is determined, and thus the main signal node or area contributing to the main radiation is accurately identified.

[0063] As an example, in step S3, based on the signal integrity diagnosis and radiation source location results, one or more rectification measures are selected specifically, and the parameter and location adjustment scheme is determined. Rectification measures include, but are not limited to: adjusting or adding the values ​​and positions of the input matching resistor R3 and input matching capacitor C1 within the input matching unit 10 (details omitted here), or grounding the traces with strong radiation (details omitted here). Each rectification measure corresponds to a specific physical modification, aiming to reduce near-field radiation intensity and improve the signal waveform. The signal waveform after rectification is as follows: Figure 5 As shown, the waveform is smoother. Furthermore, the near-field spectrum scan before rectification is shown below. Figure 6 As shown, the rectified near-field spectrum scan is as follows: Figure 7 As shown in the figure, before the rectification, the radiated power of the high-speed SPI interference frequencies was prominent, and the noise level across the entire frequency band was high; after the rectification, the radiated power of the aforementioned key interference frequencies was significantly reduced, and the overall near-field radiated noise was significantly reduced. Previously, the signal lines lacked grounding, resulting in large return loops and a tendency to form radiating antennas; after the rectification, the matching resistor was placed at the far end, the high-speed signal lines were grounded throughout, the ground return path was optimized, and the radiated loop area was significantly reduced. The measured radiated interference spectrum before the rectification is shown in the figure. Figure 8 As shown, the measured spectrum of radiation interference after rectification is as follows: Figure 9 As shown, before the rectification, the risk of exceeding the radiation interference peak was high, with many peaks approaching the limit; after the rectification, the interference peak of this frequency band decreased significantly, and the radiation limit requirements were met across the entire frequency band, with the EMC radiation index meeting the standards.

[0064] As an example, in step S4, after rectification, the same signal waveform is measured again using an oscilloscope to confirm that overshoot and ringing have disappeared or significantly decreased. Then, a spectrum analyzer is used with a near-field probe to scan the original strong interference point to observe whether the radiation intensity has decreased below the reference limit. If the radiation decreases after rectification but still exceeds the standard, steps S2-S4 are repeated until the near-field radiation meets the predetermined standard. Finally, the rectified prototype is sent to the certification anechoic chamber for full-band formal radiated interference testing to obtain the final pass data.

[0065] As an example, in step S5, the rectified electricity meter is sent into a standard anechoic chamber for a full-band radiation interference formal test to confirm that the final test results meet the standard requirements and have a margin of more than 5dB.

[0066] The radiation rectification method provided in this application establishes a mapping relationship between signal integrity defects and electromagnetic radiation through a closed-loop process of "oscilloscope diagnosis of signal overshoot and ringing—spectrum analyzer near-field scanning to locate the interference source—formulation of target rectification plan—verification of rectification effect." This enables precise location of the interference source, guides targeted adjustment of component parameters and layout positions, completely changes the blindness of traditional trial-and-error methods, significantly shortens the rectification cycle, reduces R&D and repeated testing costs, and achieves efficient and low-cost radiation interference rectification.

[0067] The isolation circuit, electricity meter, and radiation rectification method provided in this application adopt a closed-loop precision detection and rectification system, replacing the traditional trial-and-error method. This eliminates the need for repeated debugging and testing, significantly shortening the rectification cycle and greatly reducing the costs of electricity meter R&D, debugging, and on-site rectification. It solves the industry pain points of traditional rectification methods, which are characterized by high blindness, high cost, and low efficiency. By using a filtering network to specifically eliminate signal overshoot and ringing defects, and precisely suppressing high-frequency harmonic interference, it addresses the core issue of excessive radiation from the signal source, making the rectification highly targeted. The structure of placing matching resistors nearby achieves precise impedance matching, effectively eliminating signal reflection and waveform distortion problems in long wiring, allowing the impedance matching structure to truly play its anti-interference role and significantly improving signal integrity. The full-length ground shielding structure perfectly adapts to the working conditions of electricity meter structures with long wiring, completely solving the problem of crosstalk between long lines and preventing radiation exceeding standards caused by crosstalk superposition, demonstrating extremely high adaptability. Through multi-dimensional collaborative optimization, while ensuring electricity meter standards, it retains the highest communication rate and multi-level sampling function throughout the process. The metering accuracy and data transmission stability are not affected in any way, and the product mass production yield is greatly improved.

[0068] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0069] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0070] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A communication isolation circuit, suitable for use within an electricity meter, characterized in that, It includes an isolation chip, an input matching unit, an output matching unit, an input bias unit, and an output bias unit; An input matching unit is disposed between the metering unit of the energy meter and the input side of the isolation chip, adjacent to the signal output pin of the metering unit, and is used to perform impedance matching on the signal input from the metering unit to the isolation chip; An output matching unit is disposed between the management unit of the energy meter and the output side of the isolation chip, and is used to perform impedance matching on the signal input from the isolation chip to the management unit; The input bias unit includes a first bias resistor, which is located between a first power supply and a first enable pin of the isolation chip. The output bias unit includes a second bias resistor between the second power supply and the second enable pin of the isolation chip.

2. The communication isolation circuit according to claim 1, characterized in that, The input matching unit includes multiple input matching circuits; Each of the input matching circuits includes an input matching resistor and an input matching capacitor; The first end of each input matching resistor is connected to a communication data port of the metering unit, and the second end of the input matching resistor is connected to the input pin of the isolation chip. The first end of each input matching capacitor is connected to the connection node between the input matching resistor and the input pin of the isolation chip, and the second end of the input matching capacitor is grounded.

3. The communication isolation circuit according to claim 1, characterized in that, The output matching unit includes multiple output matching circuits, each output matching circuit includes an output matching resistor, the first end of each output matching resistor is connected to the output pin of the isolation chip, and the second end is connected to a communication data port of the management unit.

4. The communication isolation circuit according to claim 1, characterized in that, The input matching circuit includes a common-mode choke, which is connected in series on the signal line of the communication data port between the metering unit and the isolation chip; or connected in series on the signal line of the communication data port between the management unit and the isolation chip.

5. The communication isolation circuit according to claim 1, characterized in that, When wiring the communication isolation circuit, ground copper foil is laid on both sides of the signal line of the communication data port and on the adjacent layer. The ground copper foil is connected to the inner ground plane through spaced grounding vias.

6. The communication isolation circuit according to claim 1, characterized in that, The communication isolation circuit adopts a four-layer stacked structure of top layer, first inner layer, second inner layer and bottom layer during wiring. The signal line of the communication data port is laid on the top layer, and the first inner layer and the second inner layer are used as reference return planes.

7. The communication isolation circuit according to claim 1, characterized in that, The communication isolation circuit also includes an input power supply unit and an output power supply unit; An input power supply unit is disposed between the metering unit of the energy meter and the input side of the isolation chip, including at least one first current-limiting resistor and at least one first decoupling capacitor; the first end of the first current-limiting resistor is connected to the first power supply, and the second end of the first current-limiting resistor is connected to the first power supply pin of the isolation chip; at least one first decoupling capacitor is connected in parallel between the first current-limiting resistor and ground. An output power supply unit is disposed between the management unit of the energy meter and the output side of the isolation chip, and includes at least one second current-limiting resistor and at least one second decoupling capacitor; the second end of the second current-limiting resistor is connected to the second power supply, and the first end of the second current-limiting resistor is connected to the second power supply pin of the isolation chip; at least one second decoupling capacitor is connected in parallel between the second current-limiting resistor and ground.

8. An electricity meter, comprising a metering unit and a management unit, and further comprising a first communication circuit and a second communication circuit; The first communication circuit is connected to the output terminal of the metering unit and the input terminal of the management unit, and is used to transmit the signal output by the metering unit to the management unit. The second communication circuit is connected to the output terminal of the metering unit and the input terminal of the management unit, and is used to transmit the signal output by the metering unit to the management unit; At least one of the first communication circuit and the second communication circuit is a communication isolation circuit according to any one of claims 1-7, the input matching unit is disposed between the metering unit and the input side of the isolation chip, and the output matching unit is disposed between the management unit and the output side of the isolation chip.

9. A method for rectifying radiation from an electricity meter, applicable to the electricity meter described in claim 8, characterized in that, include: An oscilloscope was used to measure the energy meter to determine whether there were overshoot and ringing defects in the signal waveform, and the signal integrity parameters were recorded. When the signal waveform exhibits overshoot and ringing, a spectrum analyzer is used in conjunction with a near-field probe to scan and pinpoint the specific location of the radiated interference source. Based on the signal integrity defects and interference source location results, a target rectification plan is formulated, which includes adjusting the position of the matching resistor, optimizing its parameters, and processing the signal line ground wrap. The electricity meter is rectified based on the target rectification plan until the remeasured signal waveform and near-field radiation intensity both meet the preset threshold. The energy meter that meets the preset threshold is sent into an anechoic chamber for full-band radiation interference test verification.

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