Voltage-mode Digital Active EMI Filtering Method and Circuit Based on Switching Spectrum Analysis and Reconstruction

Abstract

This application relates to a voltage - type digital active EMI filtering method and circuit based on switching spectrum analysis and reconstruction. Among them, the method includes: obtaining the common - mode noise data and 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, parasitic capacitors, and LISN impedances, calculating the common - mode compensation voltage data and differential - mode compensation voltage data at each frequency point to obtain compensation voltage data; outputting the compensation voltage data through a DAC synchronously with the PWM, and injecting the compensation voltage data into the positive bus and the negative bus through an injection inductor for noise compensation. Using the voltage - type digital active EMI filtering method and circuit based on switching spectrum analysis and reconstruction provided by this application, it is suitable for scenarios dominated by differential - mode noise, and can achieve the co - suppression of common - mode and differential - mode interferences while without detection and reducing the volume.

Description

Technical Field

[0001] This application relates to the technical field of EMI suppression for power electronic converters mainly with differential-mode noise, and particularly to a digital active EMI filtering method and circuit based on switching spectrum analysis and voltage reconstruction. 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 higher switching frequencies and higher power densities. However, higher 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 two types: passive and active. Among them, the passive EMI filter is composed of passive devices such as inductors and capacitors, which can suppress electromagnetic interference. However, its volume is relatively 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, thereby effectively reducing the volume. However, it has high bandwidth requirements for active devices. While the cost is relatively high, it also requires an additional isolated power supply.

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

[0005] However, in the above digital active EMI filtering technology, the ADC in the detection loop and the DAC in the injection loop still require relatively high costs. Moreover, the existing digital active EMI filtering technology usually suppresses interference for the positive bus and the negative bus, rather than for common-mode interference and differential-mode interference. As a result, the EMI suppression ability cannot be fully utilized, leading to problems such as the mutual conversion between common-mode interference and differential-mode interference. In addition, most of the existing EMI suppression technologies only suppress common-mode or differential-mode separately and cannot achieve common suppression.

[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 voltage - type digital active EMI filtering method and circuit based on switching spectrum analysis and reconstruction, which is suitable for scenarios mainly with differential - mode noise, and can suppress both common - mode and differential - mode interferences while reducing the volume.

[0008] To achieve the objectives of the present application, the following technical solutions are provided:

[0009] In a first aspect, the present application provides a voltage - type digital active EMI filtering method based on switching spectrum analysis and reconstruction, including:

[0010] Obtain the common - mode noise data and differential - mode noise data of the measured buck - down circuit (Buck circuit) at the switching frequency points; the common - mode noise data includes common - mode noise spectrum amplitude data and phase data, and the differential - mode noise data includes 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 parasitic capacitance, and the impedance of a linear impedance stabilization network (LISN), calculate the common - mode compensation voltage data and differential - mode compensation voltage data at each frequency point, and obtain the compensation voltage data;

[0012] Output the compensation voltage data through a DAC synchronously with pulse - width modulation (PWM), and inject the compensation voltage data into the positive bus and the negative bus through an injection inductor for noise compensation; wherein, the common - mode compensation voltage data is injected into the positive bus and the negative bus through the positive - bus injection inductor and the negative - bus injection inductor to compensate for the common - mode noise, and the differential - mode compensation voltage data is injected into the positive bus through the positive - bus injection inductor to compensate for the differential - mode noise.

[0013] In a possible implementation, after the step of outputting the compensation voltage data through a DAC synchronously with PWM and injecting the compensation voltage data into the positive bus and the negative bus through an injection inductor for noise compensation, it further includes:

[0014] Measure the noise voltage on the LISN as the noise - source voltage, calculate the iterative compensation voltage data, and superimpose it on the compensation voltage data to perform iteration on the compensation voltage data.

[0015] In a possible implementation, the step of obtaining the common - mode noise data and differential - mode noise data of the Buck circuit at the switching frequency points includes:

[0016] Measure the common-mode noise voltage time-domain waveform data and differential-mode noise voltage time-domain waveform data on the LISN through a noise separator and an oscilloscope;

[0017] According to the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data, obtain the common-mode noise data and the differential-mode noise data at the switching frequency points through fast Fourier transform (FFT).

[0018] 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:

[0019] Separate the common-mode noise and differential-mode noise on the LISN through a noise separator;

[0020] According to the separated common-mode noise and differential-mode noise, measure the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data through an oscilloscope.

[0021] 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 parasitic capacitance, and an LISN impedance, calculating the common-mode compensation voltage data and the differential-mode compensation voltage data at each frequency point, and obtaining the compensation voltage data includes:

[0022] Construct the common-mode equivalent circuit and the differential-mode equivalent circuit including a noise source, a compensation voltage source, a parasitic capacitance, and an LISN impedance;

[0023] According to the superposition cancellation principle, obtain the relationship between the common-mode compensation voltage data of the equivalent model and the common-mode data of the equivalent model noise source voltage, and construct a first formula;

[0024] According to the superposition cancellation principle, obtain the relationship between the differential-mode compensation voltage data of the equivalent model and the differential-mode data of the equivalent model noise source voltage, and construct a second formula;

[0025] According to the first formula, calculate the amplitude and phase of the common-mode compensation voltage required at each switching frequency point, and according to the second formula, calculate the amplitude and phase of the differential-mode compensation voltage required at each switching frequency point;

[0026] Superpose the sine waves of the common-mode compensation voltage amplitude and phase at each switching frequency point to obtain the common-mode compensation voltage data, and superpose the sine waves of the differential-mode compensation voltage amplitude and phase at each switching frequency point to obtain the differential-mode compensation voltage data.

[0027] In a possible implementation, the first formula is:

[0028] ;

[0029] 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 equivalent impedance of the parasitic capacitance of the common-mode equivalent circuit, is the common-mode noise source voltage amplitude, is the common-mode noise source voltage phase;

[0030] The second formula is:

[0031] ;

[0032] Among them, is the differential-mode compensation voltage amplitude, is the differential-mode compensation voltage phase, is the equivalent impedance of the parasitic capacitance of the differential-mode equivalent circuit, is the differential-mode noise source voltage amplitude, is the differential-mode noise source voltage phase.

[0033] In a possible implementation, the common-mode compensation voltage amplitude and phase at each switching frequency are sinusoidally superimposed through a third formula, and the third formula is:

[0034] ;

[0035] Among them, is the common-mode compensation voltage data, is the switching frequency, is the time;

[0036] The differential-mode compensation voltage amplitude and phase at each switching frequency are sinusoidally superimposed through a fourth formula, and the fourth formula is:

[0037] ;

[0038] Among them, is the differential-mode compensation voltage data.

[0039] In a possible implementation, the step of outputting the compensation voltage data synchronously with the PWM through the DAC and injecting the compensation voltage data into the positive bus and the negative bus through the inductor for noise compensation includes:

[0040] Inject the common-mode compensation voltage data into the positive bus and the negative bus through the positive-bus injection inductor and the negative-bus injection inductor to compensate for the common-mode noise;

[0041] The differential-mode compensation voltage data is injected into the positive bus through the positive-bus injection inductor to compensate for differential-mode noise.

[0042] In a possible implementation, the steps of measuring the noise voltage on the measurement LISN as the noise source voltage, calculating the iterative compensation voltage data, and superimposing it on the compensation voltage data for iterative processing of the compensation voltage data include:

[0043] Measuring the noise voltage on the measurement LISN as the noise source voltage;

[0044] Obtaining iterative common-mode noise data and iterative differential-mode noise data through the noise source voltage;

[0045] According to the iterative common-mode noise data and the iterative differential-mode noise data, calculating the iterative common-mode compensation voltage data and iterative differential-mode compensation voltage data at each frequency point to obtain iterative compensation voltage data;

[0046] After superimposing the iterative compensation voltage data and the compensation voltage data, outputting them synchronously with the PWM through the DAC for noise compensation.

[0047] In a second aspect, the present application further provides a voltage-type digital active EMI filtering circuit based on switching spectrum analysis and reconstruction, which is used to execute the above-mentioned voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction. The circuit includes an injection circuit and a digital control circuit;

[0048] The digital control circuit includes a digital controller and a dual-output DAC connected to each other. The digital controller 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 common-mode compensation voltage data and differential-mode compensation voltage data at each frequency point according to the common-mode noise data and the differential-mode noise data to obtain compensation voltage data, and is used to control the synchronization of the PWM and the DAC. The DAC is used to perform analog output on the compensation voltage data;

[0049] The injection circuit includes a positive-bus injection inductor and a negative-bus injection inductor. The positive-bus injection inductor is used to inject the common-mode compensation voltage data and the differential-mode compensation voltage data into the positive bus to compensate for differential-mode noise and part of the common-mode noise. The negative-bus injection inductor is used to inject the common-mode compensation voltage data into the negative bus to compensate for the remaining common-mode noise.

[0050] The technical solution provided by the present application may include the following beneficial effects:

[0051] A voltage - type digital active EMI filtering method and circuit based on switching spectrum analysis and reconstruction provided by this application are suitable for scenarios mainly with differential - mode noise. Without a detection circuit, it can reduce costs and volume while suppressing both common - mode and differential - mode interferences, making full use of the EMI suppression ability, avoiding the mutual conversion between common - mode and differential - mode interferences, and suppressing both common - mode and differential - mode simultaneously. It can achieve a 5 - 30 dB drop in the low - frequency band of the common - mode noise spectrum and a 10 - 30 dB drop in the low - frequency band of the differential - mode noise spectrum.

[0052] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and do not limit the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used 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 the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0054] Figure 1 It is a schematic flowchart of a voltage - type digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of this application;

[0055] Figure 2 It is a schematic flowchart of step S100 of a voltage - type digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of this application;

[0056] Figure 3 It is a schematic flowchart of step S200 of a voltage - type digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of this application;

[0057] Figure 4 It is a schematic flowchart of step S300 of a voltage - type digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of this application;

[0058] Figure 5 It is a schematic flowchart of step S400 of a voltage - type digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of this application;

[0059] Figure 6 It is a logical schematic diagram of a voltage - type digital active EMI filtering method based on switching spectrum analysis and reconstruction provided by an embodiment of this application;

[0060] Figure 7Schematic diagram of the common - mode equivalent circuit model for a voltage - type digital active EMI filtering method based on switch spectrum analysis and reconstruction provided by an embodiment of this application;

[0061] Figure 8 Schematic diagram of the differential - mode equivalent circuit model for a voltage - type digital active EMI filtering method based on switch spectrum analysis and reconstruction provided by an embodiment of this application;

[0062] Figure 9 Effect diagram of the common - mode simulation spectrum for a voltage - type digital active EMI filtering method based on switch spectrum analysis and reconstruction provided by an embodiment of this application;

[0063] Figure 10 Effect diagram of the differential - mode simulation spectrum for a voltage - type digital active EMI filtering method based on switch spectrum analysis and reconstruction provided by an embodiment of this application;

[0064] Figure 11 Schematic diagram of the structure of a voltage - type digital active EMI filtering circuit based on switch spectrum analysis and reconstruction provided by an embodiment of this application;

[0065] Figure 12 Schematic diagram of the circuit structure in the existing digital active EMI filtering technology in the background art of this application. Detailed implementation mode

[0066] Now, example embodiments will 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 more complete and comprehensive, and will fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0067] In this example embodiment, a dynamic interference power management based on switch spectrum analysis and reconstruction voltage - type digital active EMI filtering method under feedback sparsity and observation loss conditions is first provided. Referring to Figure 1 as shown in, this voltage - type digital active EMI filtering method based on switch spectrum analysis and reconstruction can include the following steps:

[0068] Step S100: Obtain the common - mode noise data and differential - mode noise data of the Buck circuit at the switching frequency points.

[0069] Step S200: Construct a common - mode equivalent circuit and a differential - mode equivalent circuit including a noise source, a compensation voltage source, parasitic capacitance, and LISN impedance, calculate the common - mode compensation voltage data and differential - mode compensation voltage data at each frequency point, and obtain the compensation voltage data.

[0070] Step S300: Output the compensation voltage data synchronously with PWM through a DAC. The compensation voltage data is injected into the positive bus and the negative bus through an injection inductor for noise compensation. Among them, the common-mode compensation voltage data is injected into the positive bus and the negative bus through the positive-bus injection inductor and the negative-bus injection inductor to compensate for common-mode noise, and the differential-mode compensation voltage data is injected into the positive bus through the positive-bus injection inductor to compensate for differential-mode noise.

[0071] Through the above method for reconstructing a voltage-mode digital active EMI filter based on switching spectrum analysis, it is suitable for scenarios dominated by differential-mode noise. It can generate and output synchronously with the DAC through a common-differential-mode composite compensation voltage, and inject the compensation voltage into the positive bus and the negative bus through an injection inductor, omitting the traditional detection circuit, reducing the volume and cost. At the same time, as Figure 9 shown, a 5 - 30 dB reduction in the low-frequency band of the common-mode noise spectrum and a 10 - 30 dB reduction in the low-frequency band of the differential-mode noise spectrum can be achieved.

[0072] Next, reference will be made to Figures 2 to 6 for a more detailed description of each step of the above method for reconstructing a voltage-mode digital active EMI filter based on switching spectrum analysis in this exemplary embodiment.

[0073] In step S100, obtain the common-mode noise data and differential-mode noise data at the switching frequency points of the Buck circuit.

[0074] It should be noted that the common-mode noise data includes common-mode noise spectrum amplitude data and phase data, and the differential-mode noise data includes differential-mode noise spectrum amplitude data and phase data. A simulation circuit can be constructed using simulation software such as MATLAB and PSIM, then the noise voltage on the LISN of the simulation circuit is measured, and finally the common-mode noise data and differential-mode noise data are obtained through noise voltage separation.

[0075] In a possible implementation, step S100 may further include the following sub-steps:

[0076] In step S110, measure the common-mode noise voltage time-domain waveform data and differential-mode noise voltage time-domain waveform data on the LISN through a noise separator and an oscilloscope.

[0077] In step S120, according to the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data, obtain the common-mode noise data and the differential-mode noise data at the switching frequency points through FFT.

[0078] It should be noted that the FFT significantly reduces the computational complexity of the DFT through a specific algorithm structure (such as butterfly operation, etc.), and thus quickly converts the time-domain waveform data into frequency-domain data. In the above scenario, the time-domain waveform data of the common-mode and differential-mode noise voltages collected by the oscilloscope can be converted into frequency-domain data through the FFT, and then the common-mode and differential-mode noise data at the switching frequency points can be obtained, which is convenient for analyzing the characteristics of the noise at specific frequency points.

[0079] Furthermore, step S110 may include:

[0080] In step S111, the common-mode noise and differential-mode noise on the LISN are separated by a noise separator.

[0081] It should be noted that the noise separator mainly works based on principles such as the impedance characteristics of the circuit and Kirchhoff's law. Taking the separation of common-mode and differential-mode signals in this application as an example, in the equivalent circuit model, the working principle formula is:

[0082] ;

[0083] 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.

[0084] 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.

[0085] In step S200, a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a parasitic capacitance, and the LISN impedance are constructed, and the common-mode compensation voltage data and differential-mode compensation voltage data at each frequency point are calculated to obtain the compensation voltage data.

[0086] It should be noted that the compensation voltage data includes: the common-mode compensation voltage data and the differential-mode compensation voltage data. The common-mode compensation voltage data includes: the common-mode spectrum amplitude data and phase data of the compensation voltage, and the differential-mode compensation voltage data includes: the differential-mode spectrum amplitude data and phase data of the compensation voltage.

[0087] In a possible implementation manner, step S200 may further include the following sub-steps:

[0088] In step S210, the common-mode equivalent circuit and the differential-mode equivalent circuit including a noise source, a compensation voltage source, a parasitic capacitance, and the LISN impedance are constructed.

[0089] 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 noise sources, compensation voltage sources, parasitic capacitors, and LISN impedances in the actual circuit into a mathematical model, a simplified framework is provided for theoretical analysis, avoiding complex actual circuit debugging. Among them, the LISN impedance is composed of a resistor and a capacitor in parallel.

[0090] In step S220, according to the superposition cancellation principle, the relationship between the common-mode compensation voltage data of the equivalent model and the common-mode data of the noise source voltage of the equivalent model is obtained, and the first formula is constructed.

[0091] In step S230, according to the superposition cancellation principle, the relationship between the differential-mode compensation voltage data of the equivalent model and the differential-mode data of the noise source voltage of the equivalent model is obtained, and the second formula is constructed.

[0092] 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.

[0093] 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 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 differential-mode compensation voltage data.

[0094] It should be noted that, by way of example, if the switching frequency , then the switching frequency points include , , , etc.

[0095] Furthermore, the first formula is:

[0096] ;

[0097] 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 LISN equivalent impedance, is the equivalent impedance of the parasitic capacitor of the common-mode equivalent circuit, is the amplitude of the common-mode noise source voltage, is the phase of the common-mode noise source voltage.

[0098] The second formula is:

[0099] ;

[0100] Among them, is the amplitude of the differential-mode compensation voltage, is the phase of the differential-mode compensation voltage, is the equivalent impedance of the input capacitance of the differential-mode equivalent circuit, is the amplitude of the differential-mode noise source voltage, is the phase of the differential-mode noise source voltage.

[0101] It should be noted that , , , among which, , are the output filter capacitors, is the parasitic capacitance, is the internal capacitance of the LISN, is the input capacitance in the differential-mode equivalent circuit.

[0102] Furthermore, the common-mode compensation voltage amplitude and phase at each switching frequency are superimposed by a sine wave through a third formula, and the third formula is:

[0103] ;

[0104] wherein, is the common-mode compensation voltage data, is the switching frequency, is the time.

[0105] The differential-mode compensation voltage amplitude and phase at each switching frequency are superimposed by a sine wave through a fourth formula, and the fourth formula is:

[0106] ;

[0107] wherein, is the differential-mode compensation voltage data.

[0108] In step S300, the compensation voltage data is output synchronously with the PWM through the DAC, and the compensation voltage data is injected into the positive bus and the negative bus through the injection inductor for noise compensation; among them, the common-mode compensation voltage data is injected into the positive bus and the negative bus through the positive-bus injection inductor and the negative-bus injection inductor to compensate for the common-mode noise, and the differential-mode compensation voltage data is injected into the positive bus through the positive-bus injection inductor to compensate for the differential-mode noise.

[0109] It should be noted that according to the common-mode and differential-mode equivalent circuit models, the compensation voltage injection points of this circuit are all in the circuit. Among them, the common-mode compensation points are on the positive bus and the negative bus, and the differential-mode compensation point is on the positive bus. Therefore, the common-mode and differential-mode compensations can be combined. Compensate for the common-mode and differential-mode noises on the L line and the common-mode noise on the N line, as shown in the following formula: ; ; Then, the compensated voltages of the generated positive bus and negative bus are synchronously output through the DAC, and compensated through the injection inductor injection circuit, where the DAC output should be synchronized with the starting point of the noise spectrum measurement in step S100.

[0110] Optionally, the DAC can be a DAC with dual output terminals or two DACs can be used.

[0111] In a possible implementation, step S300 may further include the following sub-steps:

[0112] In step S310, the common-mode compensated voltage data is injected into the positive bus and negative bus through the positive bus injection inductor and negative bus injection inductor to compensate for the common-mode noise.

[0113] In step S320, the differential-mode compensated voltage data is injected into the positive bus through the positive bus injection inductor to compensate for the differential-mode noise.

[0114] It should be noted that the positive bus injection inductor and negative bus injection inductor are connected in series in the main circuit for transmitting the compensated voltage.

[0115] After step S300, it further includes: step S400: Measuring the noise voltage on the LISN as the noise source voltage, calculating the iterative compensated voltage data, and superimposing it on the compensated voltage data to perform iteration on the compensated voltage data.

[0116] It should be noted that by repeating the method of S100 - S300, the iteration of the compensated voltage further improves the EMI suppression effect. As Figure 10 shown, iterating twice can achieve a 15 - 40 dB drop in the low-frequency band of the common-mode noise spectrum and a 20 - 40 dB drop in the low-frequency band of the differential-mode noise spectrum.

[0117] In a possible implementation, step S400 may further include the following sub-steps:

[0118] In step S410, measure the noise voltage on the LISN as the noise source voltage.

[0119] In step S420, obtain the iterative common-mode noise data and iterative differential-mode noise data through the noise source voltage.

[0120] In step S430, according to the iterative common-mode noise data and the iterative differential-mode noise data, calculate the iterative common-mode compensated voltage data and iterative differential-mode compensated voltage data for each frequency point to obtain the iterative compensated voltage data.

[0121] In step S440, after superimposing the iterative compensation voltage data and the compensation voltage data, it is output synchronously with PWM through a DAC for noise compensation.

[0122] It should be noted that if there is a delay or asynchronism 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 actually measure the time difference between the PWM signal and the DAC output compensation voltage ; Move the first n data in the compensation voltage array to the end of the array to advance the phase of the compensation voltage to align with the noise source.

[0123] Furthermore, in this exemplary embodiment, a voltage-type digital active EMI filtering circuit based on switch spectrum analysis reconstruction is also provided for performing the above-mentioned voltage-type digital active EMI filtering method based on switch spectrum analysis reconstruction. Refer to Figure 11 shown in, the circuit may include an injection circuit and a digital control circuit.

[0124] The digital control circuit includes a digital controller and a dual-output DAC connected to each other; the digital controller 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 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 is used to control the synchronous output of PWM and the DAC; the DAC is used for analog output of the compensation voltage data.

[0125] The injection circuit includes a positive bus injection inductor and a negative bus injection inductor. The positive bus injection inductor is used to inject the common-mode compensation voltage data and the differential-mode compensation voltage data into the positive bus to compensate for differential-mode noise and part of the common-mode noise; the negative bus injection inductor is used to inject the common-mode compensation voltage data into the negative bus to compensate for the remaining common-mode noise.

[0126] It should be noted that as Figure 11 shown, the LISN includes a resistor connected in series with the power supply , an inductor and a capacitor , a low-pass filter and a load resistor constituted for impedance matching to ensure the accuracy of EMI measurement. The injection circuit includes a positive bus injection inductor and a negative bus injection inductor , connected to the positive bus to inject common-mode and differential-mode compensation voltages, Connected to the negative bus to inject a common-mode compensation voltage. The measured buck converter circuit, namely the Buck circuit, includes: a switching transistor and , the parasitic capacitance of the switching transistor , , the node switch , the connecting inductor , the input capacitance the output capacitance , the load , the output filter capacitance and , the parasitic capacitance and the drive ; The controls and conduct alternately to achieve the buck function, connect the switching node to the protective ground wire; when the switching transistor is turned on or off, the voltage at the point changes rapidly at high frequency, and through couples a common-mode noise current to the protective ground wire, becoming an EMI source. The digital control circuit includes a digital controller and a dual-output DAC connected to each other, and the dual-output DAC can output common-mode compensation voltage data and differential-mode compensation voltage data respectively.

[0127] 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 embodiments are only to be considered as exemplary, and the true scope and spirit of the present disclosure are pointed out by the appended claims.

[0128] The above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit it. The present application is not limited to the exact structures already described and illustrated in the drawings, and it cannot be considered that the specific implementation of the present application is only limited to these descriptions. For those of ordinary skill in the technical field to which the present application pertains, without departing from the concept of the present application, various changes and modifications made should be regarded as falling within the protection scope of the present application.

Claims

1. A voltage - type digital active EMI filtering method based on switching spectrum analysis and reconstruction, characterized in that Including: Obtain the common-mode noise data and differential-mode noise data of the Buck circuit at the switching frequency points; The common-mode noise data includes common-mode noise spectrum amplitude data and phase data, and the differential-mode noise data includes differential-mode noise spectrum amplitude data and phase data; Construct a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a parasitic capacitance, and an LISN impedance, calculate the common-mode compensation voltage data and differential-mode compensation voltage data at each frequency point, and obtain the compensation voltage data; specifically including: Construct the common-mode equivalent circuit and the differential-mode equivalent circuit including the noise source, the compensation voltage source, the parasitic capacitance, and the LISN impedance; According to the superposition cancellation principle, obtain the relationship between the common-mode compensation voltage data of the equivalent model and the common-mode data of the equivalent model noise source voltage, and construct the first formula; According to the superposition cancellation principle, obtain the relationship between the differential-mode compensation voltage data of the equivalent model and the differential-mode data of the equivalent model noise source voltage, and construct the second formula; According to the first formula, calculate the amplitude and phase of the common-mode compensation voltage required at each switching frequency point, and according to the second formula, calculate the amplitude and phase of the differential-mode compensation voltage required at each switching frequency point; Superpose the sine waves of the common-mode compensation voltage amplitude and phase at each switching frequency point to obtain the common-mode compensation voltage data, and superpose the sine waves of the differential-mode compensation voltage amplitude and phase at each switching frequency point to obtain the differential-mode compensation voltage data; Among them, the first formula is: ； wherein, is the amplitude of the common-mode compensation voltage, is the phase of the common-mode compensation voltage, is the equivalent resistance of the LISN, is the equivalent impedance of the LISN, is the equivalent impedance of the parasitic capacitance of the common-mode equivalent circuit, is the amplitude of the common-mode noise source voltage, is the phase of the common-mode noise source voltage; The second formula is: ； wherein, is the amplitude of the differential-mode compensation voltage, is the phase of the differential-mode compensation voltage, is the equivalent impedance of the input capacitance of the differential-mode equivalent circuit, is the amplitude of the differential-mode noise source voltage, is the phase of the differential-mode noise source voltage; Output the compensation voltage data through a DAC in synchronization with the PWM, inject the compensation voltage data into the positive bus and the negative bus through an injection inductor for noise compensation; among them, the common-mode compensation voltage data is injected into the positive bus and the negative bus through the positive-bus injection inductor and the negative-bus injection inductor to compensate for the common-mode noise, and the differential-mode compensation voltage data is injected into the positive bus through the positive-bus injection inductor to compensate for the differential-mode noise.

2. The method for reconstructing a voltage-type digital active EMI filter based on switch spectrum analysis according to claim 1, wherein After the step of outputting the compensation voltage data through a DAC in synchronization with the PWM and injecting the compensation voltage data into the positive bus and the negative bus through an injection inductor for noise compensation, it further includes: Measure the noise voltage on the LISN as the noise source voltage, calculate the iterative compensation voltage data, and superimpose it on the compensation voltage data to perform iteration on the compensation voltage data.

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

4. The method for reconstructing a voltage - type digital active EMI filter based on switching spectrum analysis according to claim 3, wherein The step of measuring the common-mode noise voltage time-domain waveform data and differential-mode noise voltage time-domain waveform data on the LISN through a noise separator and an oscilloscope includes: Separate the common-mode noise and differential-mode noise on the LISN through a noise separator; 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 obtained through oscilloscope measurement.

5. The method for reconstructing a voltage - type 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 common-mode compensation voltage 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 differential-mode compensation voltage data.

6. The method for reconstructing a voltage - type digital active EMI filter based on switching spectrum analysis according to claim 1, characterized in that, The step of synchronously outputting the compensation voltage data through a DAC with PWM and injecting the compensation voltage data into the positive bus and the negative bus through an injection inductor for noise compensation includes: Injecting the common-mode compensation voltage data into the positive bus and the negative bus through the positive-bus injection inductor and the negative-bus injection inductor to compensate for the common-mode noise; Injecting the differential-mode compensation voltage data into the positive bus through the positive-bus injection inductor to compensate for the differential-mode noise.

7. The method for reconstructing a voltage-type digital active EMI filter based on switching spectrum analysis according to claim 2, wherein The step of measuring the noise voltage on the LISN as the noise source voltage, calculating the iterative compensation voltage data, and superimposing it on the compensation voltage data for iterative compensation of the compensation voltage data includes: Measuring the noise voltage on the LISN as the noise source voltage; Obtaining the iterative common-mode noise data and iterative differential-mode noise data from the noise source voltage; Calculating the iterative common-mode compensation voltage data and iterative differential-mode compensation voltage data at each frequency point according to the iterative common-mode noise data and the iterative differential-mode noise data to obtain the iterative compensation voltage data; After superimposing the iterative compensation voltage data and the compensation voltage data, outputting them synchronously through a DAC with PWM for noise compensation.

8. A voltage - type digital active EMI filtering circuit based on switching spectrum analysis and reconstruction, characterized in that, The circuit is used to execute the voltage-type digital active EMI filtering method based on switch spectrum analysis and reconstruction as described in any one of claims 1 to 7. The circuit includes an injection circuit and a digital control circuit; The digital control circuit includes a digital controller and a dual-output DAC connected to each other. The digital controller 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 common-mode compensation voltage data and differential-mode compensation voltage data at 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 control the synchronization of the PWM and the output of the DAC; The DAC is used for analog output of the compensation voltage data; The injection circuit includes a positive-bus injection inductor and a negative-bus injection inductor. The positive-bus injection inductor is used to inject the common-mode compensation voltage data and the differential-mode compensation voltage data into the positive bus to compensate for the differential-mode noise and part of the common-mode noise; The negative-bus injection inductor is used to inject the common-mode compensation voltage data into the negative bus to compensate for the remaining common-mode noise.

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