Current-Type Digital Active EMI Filtering Method and Circuit Based on Switching Spectrum Analysis and Reconstruction

Abstract

This application relates to a current-mode digital active EMI filtering method and circuit based on switching spectrum analysis and reconstruction. The method includes: obtaining the initial common-mode noise data and initial differential-mode noise data of the Buck circuit at the switching frequency points; constructing a common-mode equivalent circuit and a differential-mode equivalent circuit including noise sources, compensation voltage sources, compensation capacitors, parasitic capacitors, and LISN impedances, calculating the initial compensation voltage common-mode data and initial compensation voltage differential-mode data at each frequency point to obtain the initial compensation voltage data; synchronously outputting the initial compensation voltage data through a DAC for initial noise compensation; measuring the noise voltage on the LISN as the noise source voltage, calculating the secondary compensation voltage data, and performing superposition iteration on the compensation voltage data. It is suitable for scenarios mainly with common-mode noise, and can achieve composite suppression of common-mode and differential-mode while detecting without detection and reducing the volume, and continuously optimize the EMI suppression effect through iterative update.

Description

Technical Field

[0001] This application relates to the technical field of EMI suppression for power electronic converters mainly with common-mode noise, and particularly relates to a switching spectrum analysis and reconstruction current-mode digital active EMI filtering method and circuit. Background Art

[0002] At present, power electronic technology has developed rapidly, and power electronic converters are increasingly widely used in fields such as new energy, electric vehicles, and industrial control. With the popularization of wide-bandgap semiconductor devices (such as SiC and GaN), it promotes the development of converters towards high switching frequencies and high power densities. However, high switching frequencies are likely to lead to higher rates of voltage change (dv / dt) and current change (di / dt), as well as stronger electromagnetic coupling between components, further exacerbating the electromagnetic interference problem (EMI) of power electronic converters.

[0003] In the face of electromagnetic interference of power electronic converters, EMI filters are usually used for suppression. Traditional EMI filters are divided into passive and active types. Among them, the passive EMI filter is composed of passive devices such as inductors and capacitors and can suppress electromagnetic interference. However, its volume is large and it is difficult to meet the requirements of high power density. The active EMI filter detects the electromagnetic interference voltage or current generated by the power electronic converter, amplifies it in reverse through an operational amplifier, and then injects it into the system through an injection circuit, thus effectively reducing the volume. However, it has high bandwidth requirements for active devices, high costs, and also requires an additional isolated power supply.

[0004] In the prior art, with the rise of digital control technology, by combining digital control with active EMI filters, digital active EMI filtering technology has been obtained. As Figure 12 shown, its core principle is the same as that of traditional active EMI filtering technology, but only replaces the active devices with digital controllers, adds an analog-to-digital converter (ADC) in the detection circuit, and adds a digital-to-analog converter (DAC) in the injection circuit, thereby achieving cost reduction and volume reduction.

[0005] However, in the above digital active EMI filtering technology, the ADC in the detection circuit and the DAC in the injection circuit still require high costs. Moreover, in order to improve the EMI suppression effect, a decoupling inductor needs to be added between the detection point and the injection point of the circuit, further increasing the volume. At the same time, the existing digital active EMI filtering technology usually suppresses interference for the positive bus and the negative bus, resulting in incomplete utilization of EMI suppression capabilities, as well as mutual conversion between common-mode interference and differential-mode interference.

[0006] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present disclosure, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0007] In view of the above problems, the present application provides a method and circuit for reconstructing a current-mode digital active EMI filter based on switch spectrum analysis, which is suitable for scenarios mainly with common-mode noise, can reduce the volume while achieving composite suppression of common-mode and differential-mode, and continuously optimize the EMI suppression effect through iterative update.

[0008] To achieve the object of the present application, the present application provides the following technical solutions:

[0009] In a first aspect, the present application provides a method for reconstructing a current-mode digital active EMI filter based on switch spectrum analysis, including:

[0010] Obtain the initial common-mode noise data and initial differential-mode noise data of the measured buck circuit at the switching frequency points; the initial common-mode noise data includes initial common-mode noise spectrum amplitude data and phase data, and the initial differential-mode noise data includes initial differential-mode noise spectrum amplitude data and phase data;

[0011] Construct a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor, and the impedance of a linear impedance stabilization network (LISN), and calculate the initial compensation voltage common-mode data and initial compensation voltage differential-mode data at each frequency point according to the initial common-mode noise data and the initial differential-mode noise data to obtain initial compensation voltage data; the initial compensation voltage data includes: the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data, the initial compensation voltage common-mode data includes: initial compensation voltage common-mode spectrum amplitude data and phase data, and the initial compensation voltage differential-mode data includes: initial compensation voltage differential-mode spectrum amplitude data and phase data;

[0012] Output the initial compensation voltage data through a DAC in synchronization with pulse width modulation (PWM) for initial noise compensation; wherein, the initial compensation voltage common-mode data is output to a common-mode compensation capacitor to generate an initial common-mode compensation current input to the ground wire to compensate for common-mode noise, and the initial compensation voltage differential-mode data is output to a differential-mode compensation capacitor to generate an initial differential-mode compensation current input to the positive bus to compensate for differential-mode noise;

[0013] After the initial noise compensation is completed, measure the noise voltage on the LISN as the noise source voltage, calculate the secondary compensation voltage data, and superimpose it on the initial compensation voltage data to iterate the compensation voltage data.

[0014] In a possible implementation, the step of obtaining the initial common-mode noise data and the initial differential-mode noise data of the Buck circuit at the switching frequency point includes:

[0015] Measuring the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data on the LISN through a noise separator and an oscilloscope;

[0016] According to the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data, obtaining the initial common-mode noise data and the initial differential-mode noise data at the switching frequency point through fast Fourier transform (FFT).

[0017] In a possible implementation, the step of measuring the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data on the LISN through a noise separator and an oscilloscope includes:

[0018] Separating the common-mode noise and the differential-mode noise on the LISN through a noise separator;

[0019] According to the separated common-mode noise and differential-mode noise, measuring the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data through an oscilloscope.

[0020] In a possible implementation, the step of constructing a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor, and the LISN impedance, and calculating the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data at each frequency point according to the initial common-mode noise data and the initial differential-mode noise data to obtain the initial compensation voltage data includes:

[0021] Constructing the common-mode equivalent circuit and the differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor, and the LISN impedance;

[0022] Ignoring the parasitic capacitance in the picofarad order, obtaining the relationship between the equivalent model compensation voltage common-mode data and the equivalent model noise source voltage common-mode data according to the superposition cancellation principle, and constructing a first formula;

[0023] Obtaining the relationship between the equivalent model compensation voltage differential-mode data and the equivalent model noise source voltage differential-mode data according to the superposition cancellation principle, and constructing a second formula;

[0024] Calculating the amplitude and phase of the common-mode compensation voltage required at each switching frequency point according to the first formula, and calculating the amplitude and phase of the differential-mode compensation voltage required at each switching frequency point according to the second formula;

[0025] The sinusoidal waves of the common-mode compensation voltage amplitude and phase at each switching frequency point are superimposed to obtain the initial common-mode compensation voltage data, and the sinusoidal waves of the differential-mode compensation voltage amplitude and phase at each switching frequency point are superimposed to obtain the initial differential-mode compensation voltage data.

[0026] In a possible implementation, the first formula is:

[0027] ;

[0028] Where is the common-mode compensation voltage amplitude, is the common-mode compensation voltage phase, is the LISN equivalent resistance, is the LISN equivalent impedance, is the impedance of the common-mode compensation capacitor, is the common-mode noise source voltage amplitude, is the common-mode noise source voltage phase;

[0029] The second formula is:

[0030] ;

[0031] Where is the differential-mode compensation voltage amplitude, is the differential-mode compensation voltage phase, is the impedance of the input capacitor in the differential-mode equivalent circuit, is the impedance of the common-mode compensation capacitor, is the differential-mode noise source voltage amplitude, is the differential-mode noise source voltage phase.

[0032] In a possible implementation, the sinusoidal waves of the common-mode compensation voltage amplitude and phase at each switching frequency point are superimposed through the third formula, and the third formula is:

[0033] ;

[0034] Where is the initial common-mode compensation voltage data, is the switching frequency, is the time;

[0035] The sinusoidal waves of the differential-mode compensation voltage amplitude and phase at each switching frequency point are superimposed through the fourth formula, and the fourth formula is:

[0036] ;

[0037] Where is the initial differential-mode compensation voltage data.

[0038] In a possible implementation, the step of synchronously outputting the initial compensation voltage data through a DAC with PWM for initial noise compensation includes:

[0039] Set the compensation voltage reference point to the negative bus through the common-mode equivalent circuit and the differential-mode equivalent circuit;

[0040] Output the initial compensation voltage common-mode data to the common-mode compensation capacitor to generate an initial common-mode compensation current input to the ground wire to compensate for common-mode noise;

[0041] Output the initial compensation voltage differential-mode data to the differential-mode compensation capacitor to generate an initial differential-mode compensation current input to the positive bus to compensate for differential-mode noise.

[0042] In a possible implementation, the starting moment of outputting the initial compensation voltage common-mode data is aligned with the starting moment of the initial common-mode noise data, and the starting moment of outputting the initial compensation voltage differential-mode data is aligned with the starting moment of the initial differential-mode noise data, that is, the starting points of the measured common-mode and differential-mode noise data corresponding to the PWM are the synchronous output points of the compensation voltage and the PWM.

[0043] In a possible implementation, after the initial noise compensation, measure the noise voltage on the LISN as the noise source voltage, calculate the secondary compensation voltage data, and superimpose it on the initial compensation voltage data. The steps of iteratively compensating the compensation voltage data include:

[0044] After the initial noise compensation, measure the noise voltage on the LISN as the noise source voltage;

[0045] Obtain the secondary common-mode noise data and the secondary differential-mode noise data through the noise source voltage;

[0046] According to the secondary common-mode noise data and the secondary differential-mode noise data, calculate the secondary compensation voltage common-mode data and the secondary compensation voltage differential-mode data at each frequency point to obtain the secondary compensation voltage data;

[0047] After superimposing the secondary compensation voltage data and the initial compensation voltage data, output them synchronously with the PWM through a DAC for secondary noise compensation.

[0048] In a second aspect, the present application also provides a current-mode digital active EMI filtering circuit based on switch spectrum analysis and reconstruction, which is used to execute the above-mentioned current-mode digital active EMI filtering method based on switch spectrum analysis and reconstruction. The circuit includes an injection circuit and a digital control circuit;

[0049] The digital control circuit is connected to the equipment under test (EUT) through an injection circuit, and includes a digital controller connecting two DACs. The digital controller is used to drive a switching tube, and to obtain the common-mode noise data and differential-mode noise data of the step-down circuit under test at the switching frequency point, and to calculate the common-mode compensation voltage data and differential-mode compensation voltage data for each frequency point according to the common-mode noise data and the differential-mode noise data to obtain compensation voltage data, and to perform compensation voltage superposition, and to control the synchronization of the PWM and the output of the DAC. The DAC is used to perform analog output on the compensation voltage data.

[0050] The injection circuit includes a common-mode compensation capacitor and a differential-mode compensation capacitor. The common-mode compensation capacitor is used to generate a common-mode compensation current to input to the ground wire through the common-mode compensation voltage data to compensate for common-mode noise. The differential-mode compensation capacitor is used to generate a differential-mode compensation current to input to the positive bus through the differential-mode compensation voltage data to compensate for differential-mode noise.

[0051] The technical solution provided by this application may include the following beneficial effects:

[0052] Through a current-mode digital active EMI filtering method and circuit based on switching spectrum analysis and reconstruction provided by this application, it is suitable for scenarios mainly with common-mode noise, without a detection circuit, and can reduce costs and volume at the same time. At the same time, it fully utilizes the EMI suppression ability to achieve compound suppression of common-mode and differential-mode interference, avoids mutual conversion between common-mode interference and differential-mode interference, and continuously iterates to optimize the EMI suppression effect. After a single iteration, the low-frequency band of the common-mode noise drops by 10 - 30 dB, and the differential-mode noise drops by 10 - 40 dB. After two iterations, the low-frequency band of the common-mode noise spectrum drops by 20 - 30 dB, and the differential-mode noise spectrum drops by 20 - 40 dB.

[0053] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this disclosure. Description of the Drawings

[0054] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. Obviously, the drawings in the following description are only some embodiments of this disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0055] Figure 1 It is a schematic flow chart of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of this application.

[0056] Figure 2 Schematic diagram of the process of step S100 of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0057] Figure 3 Schematic diagram of the process of step S200 of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0058] Figure 4 Schematic diagram of the process of step S300 of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0059] Figure 5 Schematic diagram of the process of step S400 of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0060] Figure 6 Logic diagram of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0061] Figure 7 Schematic diagram of the common-mode equivalent circuit model of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0062] Figure 8 Schematic diagram of the differential-mode equivalent circuit model of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0063] Figure 9 Schematic diagram of the common-mode simulation spectrum effect of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0064] Figure 10 Schematic diagram of the differential-mode simulation spectrum effect of a current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0065] Figure 11 Schematic diagram of the structure of a current-mode digital active EMI filtering circuit based on switching spectrum analysis and reconstruction provided by an embodiment of the present application;

[0066] Figure 12 Schematic diagram of the circuit structure in the existing digital active EMI filtering technology in the background art of the present application. Detailed implementation manners

[0067] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments.

[0068] In this example embodiment, a method for dynamically managing interference power based on switched spectrum analysis and reconstructing a current-mode digital active EMI filter under feedback sparsity and observation loss conditions is first provided. Refer to Figure 1 As shown in, the method for reconstructing a current-mode digital active EMI filter based on switched spectrum analysis may include the following steps:

[0069] Step S100: Obtain the initial common-mode noise data and initial differential-mode noise data at the switching frequency points of the Buck circuit; the initial common-mode noise data includes initial common-mode noise spectrum amplitude data and phase data, and the initial differential-mode noise data includes initial differential-mode noise spectrum amplitude data and phase data.

[0070] Step S200: Construct a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor, and an LISN impedance. According to the initial common-mode noise data and the initial differential-mode noise data, calculate the initial compensation voltage common-mode data and initial compensation voltage differential-mode data at each frequency point to obtain initial compensation voltage data; the initial compensation voltage data includes: the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data, the initial compensation voltage common-mode data includes: initial compensation voltage common-mode spectrum amplitude data and phase data, and the initial compensation voltage differential-mode data includes: initial compensation voltage differential-mode spectrum amplitude data and phase data.

[0071] Step S300: Output the initial compensation voltage data through a DAC in synchronization with the PWM for initial noise compensation; wherein, the initial compensation voltage common-mode data is output to a common-mode compensation capacitor to generate an initial common-mode compensation current input to the ground wire to compensate for the common-mode noise, and the initial compensation voltage differential-mode data is output to a differential-mode compensation capacitor to generate an initial differential-mode compensation current input to the positive bus to compensate for the differential-mode noise.

[0072] Step S400: After the initial noise compensation is completed, measure the noise voltage on the LISN as the noise source voltage, calculate the secondary compensation voltage data, and superimpose it on the initial compensation voltage data to iterate the compensation voltage data.

[0073] Through the above current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction, it is suitable for scenarios dominated by common-mode noise. It can generate a common-differential mode composite compensation voltage synchronized with the DAC to inject a compensation capacitor, convert it into a compensation current to input the positive bus and ground wire, and perform noise compensation. The traditional detection circuit and decoupling inductor are omitted, reducing the volume and cost. At the same time, as Figures 9 - 10 shown, after a single iteration, the low-frequency band of the common-mode noise can be reduced by 10 - 30 dB, and the differential-mode noise can be reduced by 10 - 40 dB. After two iterations, the low-frequency band of the common-mode noise spectrum can be reduced by 20 - 30 dB, and the differential-mode noise spectrum can be reduced by 20 - 40 dB.

[0074] Next, reference will be made to Figures 2 to 6 to explain each step of the above current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction in the embodiment of this example in more detail. Figure 6 In

[0075] In step S100, the initial common-mode noise data and initial differential-mode noise data at the switching frequency points of the Buck circuit are obtained; the initial common-mode noise data includes the initial common-mode noise spectrum amplitude data and phase data, and the initial differential-mode noise data includes the initial differential-mode noise spectrum amplitude data and phase data.

[0076] It should be noted that the initial common-mode noise data and initial differential-mode noise data are the noise data at the switching frequency points of the Buck circuit for a single iteration, that is, the noise voltage of the Buck circuit on the measured LISN. The Buck circuit is the equipment under test (EUT), that is, the measured buck circuit. At the same time, to obtain the initial common-mode noise data and initial differential-mode noise data, a simulation circuit can be constructed through simulation software such as MATLAB and PSIM, then the noise voltage on the LISN of the simulation circuit is measured, and finally the initial common-mode noise data and initial differential-mode noise data are obtained through noise voltage separation.

[0077] In a possible implementation manner, step S100 may further include the following sub-steps:

[0078] In step S110, the time-domain waveform data of the common-mode noise voltage and the time-domain waveform data of the differential-mode noise voltage on the LISN are measured through a noise separator and an oscilloscope.

[0079] In step S120, according to the time-domain waveform data of the common-mode noise voltage and the time-domain waveform data of the differential-mode noise voltage, the initial common-mode noise data and the initial differential-mode noise data at the switching frequency points are obtained through FFT.

[0080] It should be noted that the FFT significantly reduces the computational complexity of the DFT through a specific algorithm structure (such as butterfly operations, etc.), thereby quickly converting the time-domain waveform data into frequency-domain data. In the above scenario, the FFT can convert the time-domain waveform data of the common-mode and differential-mode noise voltages collected by the oscilloscope into frequency-domain data, and then obtain the common-mode and differential-mode noise data at the switching frequency points, which is convenient for analyzing the characteristics of the noise at specific frequency points.

[0081] Furthermore, step S110 may include:

[0082] In step S111, the common-mode noise and differential-mode noise on the LISN are separated by a noise separator.

[0083] It should be noted that the noise separator mainly works based on principles such as the impedance characteristics of the circuit and Kirchhoff's laws. Taking the separation of the common-mode and differential-mode signals in this application as an example, in the equivalent circuit model, the working principle formula is:

[0084] ;

[0085] Where, is the common-mode noise voltage, is the differential-mode noise voltage, is the noise voltage of the positive bus to the ground wire, is the noise voltage of the negative bus to the ground wire.

[0086] In step S112, according to the separated common-mode noise and differential-mode noise, the time-domain waveform data of the common-mode noise voltage and the time-domain waveform data of the differential-mode noise voltage are measured by an oscilloscope.

[0087] In step S200, a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor, and the LISN impedance are constructed. According to the initial common-mode noise data and the initial differential-mode noise data, the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data at each frequency point are calculated to obtain the initial compensation voltage data.

[0088] It should be noted that the initial compensation voltage data includes: the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data. The initial compensation voltage common-mode data includes: the initial compensation voltage common-mode spectrum amplitude data and phase data. The initial compensation voltage differential-mode data includes: the initial compensation voltage differential-mode spectrum amplitude data and phase data.

[0089] In a possible implementation manner, step S200 may further include the following sub-steps:

[0090] In step S210, the common-mode equivalent circuit and the differential-mode equivalent circuit including the noise source, the compensation voltage source, the compensation capacitor, the parasitic capacitor, and the LISN impedance are constructed.

[0091] It should be noted that the common-mode equivalent circuit and the differential-mode equivalent circuit can be as Figures 7 - 8 shown. By abstracting components such as the noise source, the compensation capacitor, the parasitic capacitor, and the LISN impedance in the actual circuit into a mathematical model, a simplified framework is provided for theoretical analysis, avoiding complex actual circuit debugging.

[0092] In step S220, the parasitic capacitor in the picofarad order is ignored, and according to the superposition cancellation principle, the relationship between the equivalent model compensation voltage common-mode data and the equivalent model noise source voltage common-mode data is obtained, and a first formula is constructed.

[0093] It should be noted that ignoring the parasitic capacitor in the picofarad order such as , , , the main impedances and are retained.

[0094] In step S230, according to the superposition cancellation principle, the relationship between the equivalent model compensation voltage differential-mode data and the equivalent model noise source voltage differential-mode data is obtained, and a second formula is constructed.

[0095] In step S240, according to the first formula, the amplitude and phase of the common-mode compensation voltage required at each switching frequency point are calculated, and according to the second formula, the amplitude and phase of the differential-mode compensation voltage required at each switching frequency point are calculated.

[0096] In step S250, the sine waves of the amplitude and phase of the common-mode compensation voltage at each switching frequency point are superimposed to obtain the initial common-mode compensation voltage data, and the sine waves of the amplitude and phase of the differential-mode compensation voltage at each switching frequency point are superimposed to obtain the initial differential-mode compensation voltage data.

[0097] It should be noted that, by way of example, the switching frequency , then the switching frequency points include , , etc.

[0098] Furthermore, the first formula is:

[0099] ;

[0100] where is the amplitude of the common-mode compensation voltage, is the phase of the common-mode compensation voltage, is the LISN equivalent resistance, is the equivalent impedance of the LISN, is the impedance of the common-mode compensation capacitor, is the amplitude of the common-mode noise source voltage, is the phase of the common-mode noise source voltage.

[0101] The second formula is:

[0102] ;

[0103] Among them, is the amplitude of the differential-mode compensation voltage, is the phase of the differential-mode compensation voltage, is the impedance of the input capacitor in the differential-mode equivalent circuit, is the impedance of the common-mode compensation capacitor, is the amplitude of the differential-mode noise source voltage, is the phase of the differential-mode noise source voltage.

[0104] It should be noted that , , , , among which, is the common-mode compensation capacitor, is the differential-mode compensation capacitor, is the internal capacitor of the LISN, is other capacitors in the differential-mode equivalent circuit.

[0105] Furthermore, the amplitudes and phases of the common-mode compensation voltages at each switching frequency point are sinusoidally superimposed through the third formula, and the third formula is:

[0106] ;

[0107] Among them, is the common-mode data of the initial compensation voltage, is the switching frequency, is the time;

[0108] The amplitudes and phases of the differential-mode compensation voltages at each switching frequency point are sinusoidally superimposed through the fourth formula, and the fourth formula is:

[0109] ;

[0110] Among them, is the differential-mode data of the initial compensation voltage.

[0111] In step S300, the initial compensation voltage data is output synchronously with PWM through a DAC for initial noise compensation. Among them, the initial compensation voltage common-mode data is output to a common-mode compensation capacitor to generate an initial common-mode compensation current input to the ground wire to compensate for common-mode noise, and the initial compensation voltage differential-mode data is output to a differential-mode compensation capacitor to generate an initial differential-mode compensation current input to the positive bus to compensate for differential-mode noise.

[0112] It should be noted that common-mode noise is the in-phase interference between the positive / negative bus and the ground wire. By adjusting the voltage of the ground wire (relative to the negative bus), the common-mode noise can be cancelled out. Differential-mode noise is the potential difference between the positive bus and the negative bus, and the compensation voltage directly injected into the positive bus can cancel out this interference. In this way, the phase shift caused by multiple reference points can be avoided.

[0113] Optionally, the DAC can be a DAC with dual output terminals or two DACs can be used.

[0114] In a possible implementation, step S300 may further include the following sub-steps:

[0115] In step S310, the compensation voltage reference point is set to the negative bus through a common-mode equivalent circuit and a differential-mode equivalent circuit.

[0116] In step S320, the initial compensation voltage common-mode data is output to a common-mode compensation capacitor to generate an initial common-mode compensation current input to the ground wire to compensate for common-mode noise.

[0117] In step S330, the initial compensation voltage differential-mode data is output to a differential-mode compensation capacitor to generate an initial differential-mode compensation current input to the positive bus to compensate for differential-mode noise.

[0118] It should be noted that the starting moment of the output of the initial compensation voltage common-mode data is aligned with the starting moment of the initial common-mode noise data, and the starting moment of the output of the initial compensation voltage differential-mode data is aligned with the starting moment of the initial differential-mode noise data. That is, the starting points of the measured common-mode and differential-mode noise data corresponding to the PWM moment are the synchronous output points of the compensation voltage and the PWM.

[0119] It can be understood that the starting points of the measured common-mode and differential-mode noise data corresponding to the PWM moment are the synchronous output points of the compensation voltage output and the PWM.

[0120] In step S400, after the initial noise compensation is completed, the noise voltage on the LISN is measured as the noise source voltage, the secondary compensation voltage data is calculated, and is superimposed on the initial compensation voltage data to iterate the compensation voltage data.

[0121] It should be noted that by repeating the method of S100 - S300, the compensation voltage is iterated to further improve the EMI suppression effect.

[0122] In a possible implementation manner, the step S400 may further include the following sub - steps:

[0123] In step S410, after the initial noise compensation ends, measure the noise voltage on the LISN as the noise source voltage.

[0124] In step S420, obtain the secondary common - mode noise data and secondary differential - mode noise data through the noise source voltage.

[0125] In step S430, according to the secondary common - mode noise data and the secondary differential - mode noise data, calculate the secondary compensation voltage common - mode data and secondary compensation voltage differential - mode data for each frequency point to obtain the secondary compensation voltage data.

[0126] In step S440, after superimposing the secondary compensation voltage data and the initial compensation voltage data, output them synchronously with the PWM through the DAC for secondary noise compensation.

[0127] It should be noted that if there is a delay or out - of - sync situation in the compensation voltage, the compensation voltage can be reconstructed by adjusting the order of the compensation voltage data to eliminate the delay. The specific method can be to measure the time difference between the PWM signal and the DAC - output compensation voltage through actual testing ; move the first n data in the compensation voltage array to the end of the array to advance the phase of the compensation voltage and align it with the noise source.

[0128] Furthermore, in this exemplary implementation manner, a current - type digital active EMI filtering circuit based on switch spectrum analysis reconstruction is also provided for performing the above - mentioned current - type digital active EMI filtering method based on switch spectrum analysis reconstruction. Refer to Figure 11 As shown in, the circuit may include an injection circuit and a digital control circuit.

[0129] The digital control circuit is connected to the EUT through the injection circuit and includes a digital controller connecting two DACs; the digital controller is used to drive the switch tube, and is used to obtain the common - mode noise data and differential - mode noise data of the measured buck circuit at the switching frequency points, and is used to calculate the compensation voltage common - mode data and compensation voltage differential - mode data for each frequency point according to the common - mode noise data and the differential - mode noise data to obtain the compensation voltage data, and is used to perform compensation voltage superposition, and is used to control the PWM and the DAC output to be synchronous; the DAC is used to perform analog output on the compensation voltage data.

[0130] The injection circuit includes a common-mode compensation capacitor and a differential-mode compensation capacitor. The common-mode compensation capacitor is used to generate a common-mode compensation current through the common-mode data of the compensation voltage and input it to the ground wire to compensate for common-mode noise. The differential-mode compensation capacitor is used to generate a differential-mode compensation current through the differential-mode data of the compensation voltage and input it to the positive bus to compensate for differential-mode noise.

[0131] It should be noted that the common-mode noise data and differential-mode noise data can be stored in the digital controller in advance, such as Figure 11 As shown, the LISN includes a resistor connected in series with the power supply , an inductor and a capacitor , forming a low-pass filter and the LISN impedance , which are used for impedance matching to ensure the accuracy of EMI measurement. The injection circuit includes a common-mode compensation capacitor and a differential-mode compensation capacitor . It is connected to the PE to inject the common-mode compensation current, connected to the positive bus to inject the differential-mode compensation current. The reference points of the two capacitors are the implicitly connected neutral bus and negative bus, and they work under the drive of the digital control circuit. The buck circuit to be measured, the Buck circuit, includes: a switching transistor and , the parasitic capacitance of the switching transistor , , the node switch , the connecting inductor , the input capacitor the output capacitor , the load , the parasitic capacitances of the positive and negative buses at the output terminal to the ground and , the parasitic capacitance and the drive ; The controls and alternately conduct to achieve the buck function. is the parasitic capacitance between the switch node and the ground wire; when the switching transistor is turned on or off, the voltage at the point changes rapidly at high frequency, and a common-mode noise current is coupled to the ground wire through , becoming an EMI source. The digital control circuit has a digital controller connected to two DACs, and the two DACs are respectively used to output the common-mode and differential-mode compensation voltages.

[0132] Those skilled in the art will readily conceive of other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include known common general knowledge or conventional technical means in the technical field not disclosed in the present disclosure. The specification and examples are only illustrative, and the true scope and spirit of the present disclosure are pointed out by the appended claims.

[0133] The above embodiments are only used to illustrate the technical solutions of this application, rather than to limit it. This application is not limited to the exact structures described above and illustrated in the drawings, and it cannot be considered that the specific implementation of this application is only limited to these descriptions. For those of ordinary skill in the technical field to which this application belongs, various changes and modifications made without departing from the concept of this application should be regarded as falling within the protection scope of this application.

Claims

1. A current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction, characterized in that, including: Obtaining initial common-mode noise data and initial differential-mode noise data of the Buck circuit at the switching frequency points; The initial common-mode noise data includes initial common-mode noise spectrum amplitude data and phase data, and the initial differential-mode noise data includes initial differential-mode noise spectrum amplitude data and phase data; Constructing a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a compensation capacitor, a parasitic capacitor, and an LISN impedance, and calculating initial compensation voltage common-mode data and initial compensation voltage differential-mode data at each frequency point according to the initial common-mode noise data and the initial differential-mode noise data to obtain initial compensation voltage data; The initial compensation voltage data includes: the initial compensation voltage common-mode data and the initial compensation voltage differential-mode data, the initial compensation voltage common-mode data includes: initial compensation voltage common-mode spectrum amplitude data and phase data, and the initial compensation voltage differential-mode data includes: initial compensation voltage differential-mode spectrum amplitude data and phase data; specifically including: Constructing the common-mode equivalent circuit and the differential-mode equivalent circuit including the noise source, the compensation voltage source, the compensation capacitor, the parasitic capacitor, and the LISN impedance; Ignoring parasitic capacitors in the picofarad order, obtaining the relationship between the equivalent model compensation voltage common-mode data and the equivalent model noise source voltage common-mode data according to the superposition cancellation principle, and constructing a first formula; Obtaining the relationship between the equivalent model compensation voltage differential-mode data and the equivalent model noise source voltage differential-mode data according to the superposition cancellation principle, and constructing a second formula; Calculating the amplitude and phase of the common-mode compensation voltage required at each switching frequency point according to the first formula, and calculating the amplitude and phase of the differential-mode compensation voltage required at each switching frequency point according to the second formula; Superposing the sine waves of the amplitude and phase of the common-mode compensation voltage at each switching frequency point to obtain the initial compensation voltage common-mode data, and superposing the sine waves of the amplitude and phase of the differential-mode compensation voltage at each switching frequency point to obtain the initial compensation voltage differential-mode data; wherein, the first formula is: ； Among them, is the common-mode compensation voltage amplitude, is the common-mode compensation voltage phase, is the LISN equivalent resistance, is the LISN equivalent impedance, is the impedance of the common-mode compensation capacitor, is the common-mode noise source voltage amplitude, is the common-mode noise source voltage phase; The second formula is: ； Among them, is the amplitude of the differential-mode compensation voltage, is the phase of the differential-mode compensation voltage, is the impedance of the input capacitance in the differential-mode equivalent circuit, is the impedance of the common-mode compensation capacitance, is the amplitude of the differential-mode noise source voltage, is the phase of the differential-mode noise source voltage; Outputting the initial compensation voltage data through a DAC and synchronously outputting it with the PWM for initial noise compensation; wherein, the initial compensation voltage common-mode data is output to a common-mode compensation capacitor to generate an initial common-mode compensation current input to the ground wire to compensate for the common-mode noise, and the initial compensation voltage differential-mode data is output to a differential-mode compensation capacitor to generate an initial differential-mode compensation current input to the positive bus to compensate for the differential-mode noise; After the initial noise compensation is completed, measuring the noise voltage on the LISN as the noise source voltage, calculating to obtain secondary compensation voltage data, and superposing it on the initial compensation voltage data to iterate the compensation voltage data.

2. The method for reconstructing a current-mode digital active EMI filter based on switching spectrum analysis according to claim 1, wherein The step of obtaining the initial common-mode noise data and the initial differential-mode noise data of the Buck circuit at the switching frequency points includes: Measuring the time-domain waveform data of the common-mode noise voltage and the time-domain waveform data of the differential-mode noise voltage on the LISN through a noise separator and an oscilloscope; According to the time-domain waveform data of the common-mode noise voltage and the time-domain waveform data of the differential-mode noise voltage, obtaining the initial common-mode noise data and the initial differential-mode noise data at the switching frequency points through FFT.

3. The method for reconstructing a current-mode digital active EMI filter based on switching spectrum analysis according to claim 2, wherein The steps of measuring the time-domain waveform data of the common-mode noise voltage and the differential-mode noise voltage on the LISN through a noise separator and an oscilloscope include: Separating the common-mode noise and differential-mode noise on the LISN through a noise separator; Measuring the time-domain waveform data of the common-mode noise voltage and the differential-mode noise voltage through an oscilloscope according to the separated common-mode noise and differential-mode noise.

4. The method for reconstructing a current-mode digital active EMI filter based on switching spectrum analysis according to claim 1, wherein The amplitudes and phases of the common-mode compensation voltages at each switching frequency point are superimposed by a sine wave using the third formula, and the third formula is: ； Among them, is the initial compensation voltage common-mode data, is the switching frequency, is the time; The amplitudes and phases of the differential-mode compensation voltages at each switching frequency point are superimposed by a sine wave using the fourth formula, and the fourth formula is: ； Among them, is the initial compensation voltage differential mode data.

5. The method for reconstructing a current-mode digital active EMI filter based on switching spectrum analysis according to claim 1, wherein The steps of synchronously outputting the initial compensation voltage data through a DAC with PWM for initial noise compensation include: Setting the compensation voltage reference point to the negative bus through a common-mode equivalent circuit and a differential-mode equivalent circuit; Outputting the initial common-mode compensation voltage data to a common-mode compensation capacitor to generate an initial common-mode compensation current input to the ground wire to compensate for the common-mode noise; Outputting the initial differential-mode compensation voltage data to a differential-mode compensation capacitor to generate an initial differential-mode compensation current input to the positive bus to compensate for the differential-mode noise.

6. The method for reconstructing a current-mode digital active EMI filter based on switch spectrum analysis according to claim 5, wherein The starting moment of the output of the initial common-mode compensation voltage data is aligned with the starting moment of the initial common-mode noise data, and the starting moment of the output of the initial differential-mode compensation voltage data is aligned with the starting moment of the initial differential-mode noise data, that is, the starting points of the measured common-mode and differential-mode noise data corresponding to the PWM are the synchronous output points of the compensation voltage and the PWM.

7. The current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 1, wherein After the initial noise compensation, measuring the noise voltage on the LISN as the noise source voltage, calculating the secondary compensation voltage data, and superimposing it on the initial compensation voltage data for iterative steps of the compensation voltage data include: After the initial noise compensation, measuring the noise voltage on the LISN as the noise source voltage; Obtaining secondary common-mode noise data and secondary differential-mode noise data through the noise source voltage; Calculating the secondary common-mode compensation voltage data and secondary differential-mode compensation voltage data at each frequency point according to the secondary common-mode noise data and the secondary differential-mode noise data to obtain the secondary compensation voltage data; After superimposing the secondary compensation voltage data and the initial compensation voltage data, outputting them synchronously through a DAC with PWM for secondary noise compensation.

8. A current-mode digital active EMI filtering circuit based on switching spectrum analysis and reconstruction, characterized in that, The circuit is used to execute the current-mode digital active EMI filtering method based on switching spectrum analysis and reconstruction according to any one of claims 1 to 7, and the circuit includes an injection circuit and a digital control circuit; The digital control circuit is connected to the EUT through an injection circuit and includes a digital controller that connects two DACs. The digital controller is configured to drive a switching transistor, to obtain common-mode noise data and differential-mode noise data of the DUT at the switching frequency point, to calculate common-mode compensation voltage data and differential-mode compensation voltage data for each frequency point based on the common-mode noise data and the differential-mode noise data to obtain compensation voltage data, to perform compensation voltage superposition, and to control the synchronization of the PWM and the output of the DAC. The DAC is configured to perform analog output of the compensation voltage data. The injection circuit includes a common-mode compensation capacitor and a differential-mode compensation capacitor. The common-mode compensation capacitor is configured to generate a common-mode compensation current input to the ground wire through the common-mode compensation voltage data to compensate for common-mode noise. The differential-mode compensation capacitor is configured to generate a differential-mode compensation current input to the positive bus through the differential-mode compensation voltage data to compensate for differential-mode noise.

Images