Reconstruction voltage type digital active EMI filtering method and circuit based on switching spectrum analysis

Abstract

The invention relates to a reconstruction voltage type digital active EMI filtering method and circuit based on switching spectrum analysis, and the method comprises the steps: obtaining common-mode noise data and differential-mode noise data of a Buck circuit at a switching frequency point; constructing a common-mode equivalent circuit and a differential-mode equivalent circuit comprising a noise source, a compensation voltage source, a parasitic capacitor and LISN impedance, and calculating common-mode compensation voltage data and differential-mode compensation voltage data of each frequency point to obtain compensation voltage data; the compensation voltage data and PWM are synchronously output through a DAC, and the compensation voltage data are injected into a positive bus and a negative bus through an injection inductor for noise compensation. The reconstruction voltage type digital active EMI filtering method and circuit based on switch spectrum analysis are suitable for scenes with differential mode noise as a main part, and common suppression of common mode interference and differential mode interference can be achieved while no detection exists and the size is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of EMI suppression of power electronic converters mainly based on differential mode noise, and in particular to a voltage-type digital active EMI filtering method and circuit based on switching spectrum analysis and reconstruction. Background Art

[0002] At present, power electronics technology is developing rapidly, and power electronic converters are increasingly widely used in new energy, electric vehicles, industrial control and other fields. With the popularization of wide bandgap semiconductor devices (such as SiC and GaN), converters are driven to develop in the direction of high switching frequency and high power density. However, high switching frequency can easily lead to higher voltage change rate (dv / dt) and current change rate (di / dt), as well as stronger electromagnetic coupling between components, further exacerbating the electromagnetic interference (EMI) problem of power electronic converters.

[0003] In the face of electromagnetic interference from power electronic converters, EMI filters are usually used to suppress it. Traditional EMI filters are divided into two types: passive and active. Among them, passive EMI filters are composed of passive devices such as inductors and capacitors, which can suppress electromagnetic interference, but their size is large and it is difficult to adapt to the needs of high power density. Active EMI filters detect the electromagnetic interference voltage or current generated by the power electronic converter, amplify it through an operational amplifier, and then inject it into the system through an injection circuit, thereby effectively reducing the size, but the bandwidth requirements for active devices are high, and the cost is 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 is obtained by combining digital control with active EMI filters, such as Fig.12 As shown, its core principle is the same as the 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 reducing costs and size.

[0005] However, in the above-mentioned digital active EMI filtering technology, the ADC in the detection loop and the DAC in the injection loop still require relatively high costs, and the existing digital active EMI filtering technology usually performs interference suppression on the positive bus and the negative bus, rather than suppressing common-mode interference and differential-mode interference, so that the EMI suppression capability cannot be fully utilized, and leads to the problem of mutual conversion between common-mode interference and differential-mode interference. At the same time, most of the existing EMI suppression technologies only suppress the common mode or differential mode separately, and cannot achieve common suppression.

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

[0007] In response to 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 dominated by differential mode noise and can achieve common-mode and differential-mode interference suppression while reducing the volume.

[0008] To achieve the purpose of this application, this application provides the following technical solutions:

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

[0010] Acquire common-mode noise data and differential-mode noise data of the buck circuit under test at the switching frequency point; 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, parasitic capacitance, and a linear impedance stabilization network (LISN) impedance, calculate the common-mode compensation voltage data and the differential-mode compensation voltage data of each frequency point, and obtain the compensation voltage data;

[0012] The compensation voltage data is output synchronously with pulse width modulation (PWM) through DAC, and the compensation voltage data is injected into the positive bus and the negative bus through the injection inductor to perform 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 synchronously with PWM through a DAC, and injecting the compensation voltage data into a positive bus and a negative bus through an injection inductor to perform noise compensation, the method further includes:

[0014] The noise voltage on the LISN is measured as the noise source voltage, and iterative compensation voltage data is calculated and superimposed on the compensation voltage data to iterate the compensation voltage data.

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

[0016] The common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data on the LISN are measured by a noise separator and an oscilloscope;

[0017] The common mode noise data and the differential mode noise data at the switching frequency are obtained by fast Fourier transform (FFT) according to the common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data.

[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] The common mode noise on the LISN is separated from the differential mode noise by a noise separator;

[0020] The common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data are obtained by measuring with an oscilloscope according to the separated common-mode noise and the differential-mode noise.

[0021] In a possible implementation, the steps of constructing a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a parasitic capacitor, and a LISN impedance, calculating common-mode compensation voltage data and differential-mode compensation voltage data at each frequency point, and obtaining compensation voltage data include:

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

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

[0024] According to the superposition and 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;

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

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

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

[0028] ;

[0029] in, 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] in, 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 voltage amplitude of the differential mode noise source, is the voltage phase of the differential mode noise source.

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

[0034] ;

[0035] in, is the common mode compensation voltage data, is the switching frequency, For time;

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

[0037] ;

[0038] in, It is the differential mode compensation voltage data.

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

[0040] 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;

[0041] 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.

[0042] In a possible implementation, the step of measuring the noise voltage on the LISN as the noise source voltage, calculating iterative compensation voltage data, and superimposing it on the compensation voltage data, and iterating the compensation voltage data includes:

[0043] Measure the noise voltage on the LISN as the noise source voltage;

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

[0045] Calculating 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 iterative compensation voltage data;

[0046] After the iterative compensation voltage data is superimposed on the compensation voltage data, the data is output synchronously with the PWM through the DAC to perform noise compensation.

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

[0048] The digital control circuit comprises a digital controller and a dual-output DAC connected to each other; the digital controller is used to obtain common-mode noise data and differential-mode noise data of the buck circuit under test at the switching frequency point, and is used to calculate the common-mode compensation voltage data and differential-mode compensation voltage data of 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 PWM and the DAC synchronization; the DAC is used to perform analog output of 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 this application may have the following beneficial effects:

[0051] The present application provides a voltage-type digital active EMI filtering method and circuit based on switch spectrum analysis and reconstruction, which is suitable for scenarios dominated by differential mode noise, does not require a detection circuit, and can reduce costs while reducing volume; at the same time, common mode and differential mode interference are suppressed, so that the EMI suppression capability is fully utilized, and the mutual conversion between common mode interference and differential mode interference is avoided, and common mode and differential mode are jointly suppressed. It can achieve a 5-30dB reduction in the low-frequency band of the common mode noise spectrum, and a 10-30dB reduction in the low-frequency band of the differential mode noise spectrum.

[0052] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The accompanying 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 of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure. For those of ordinary skill in the art, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0054] Figure 1 A schematic diagram of a flow chart of a voltage-type digital active EMI filtering method based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0055] Figure 2 A flowchart of step S100 of a method for reconstructing a voltage-type digital active EMI filter based on switch spectrum analysis provided in an embodiment of the present application;

[0056] Figure 3 A flowchart of step S200 of a method for reconstructing a voltage-type digital active EMI filter based on switch spectrum analysis provided in an embodiment of the present application;

[0057] Figure 4 A flowchart of step S300 of a method for reconstructing a voltage-type digital active EMI filter based on switch spectrum analysis provided in an embodiment of the present application;

[0058] Figure 5 A flowchart of step S400 of a method for reconstructing a voltage-type digital active EMI filter based on switch spectrum analysis provided in an embodiment of the present application;

[0059] Figure 6 A logic schematic diagram of a voltage-type digital active EMI filtering method based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0060] Figure 7A schematic diagram of a common-mode equivalent circuit model of a voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction provided in an embodiment of the present application;

[0061] Figure 8 A schematic diagram of a differential mode equivalent circuit model of a voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction provided in an embodiment of the present application;

[0062] Fig. 9 A common simulation spectrum effect diagram of a voltage-type digital active EMI filtering method based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0063] Fig.10 A differential simulation spectrum effect diagram of a voltage-type digital active EMI filtering method based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0064] Fig.11 A schematic diagram of a voltage-type digital active EMI filter circuit based on switch spectrum analysis and reconstruction provided in an embodiment of the present application;

[0065] Fig.12 This is a schematic diagram of the circuit structure of the existing digital active EMI filtering technology in the background technology of this application. DETAILED DESCRIPTION

[0066] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the disclosure will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0067] In this example implementation, a voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction for dynamic interference power management under sparse feedback and missing observation conditions is first provided. Figure 1 As shown in , the voltage-type digital active EMI filtering method based on switch spectrum analysis and reconstruction may include the following steps:

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

[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 common-mode compensation voltage data and differential-mode compensation voltage data at each frequency point, and obtain compensation voltage data.

[0070] 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 to perform 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.

[0071] The voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction is suitable for scenarios dominated by differential mode noise. It can generate a common-differential mode composite compensation voltage and output it synchronously with the DAC, inject the compensation voltage into the positive bus and the negative bus through the injection inductor, omit the traditional detection circuit, reduce the size and reduce the cost; at the same time, Fig. 9 As shown, the low-frequency band of the common-mode noise spectrum can be reduced by 5-30dB, and the low-frequency band of the differential-mode noise spectrum can be reduced by 10-30dB.

[0072] Next, we will refer to Figures 2 to 6 The various steps of the above-mentioned method for reconstructing voltage-type digital active EMI filtering based on switching spectrum analysis in this exemplary implementation are described in more detail.

[0073] In step S100, common mode noise data and differential mode noise data of the Buck circuit at a switching frequency are obtained.

[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 through simulation software such as MATLAB and PSIM, and then the noise voltage on the simulation circuit LISN is measured. Finally, the common-mode noise data and the differential-mode noise data are obtained by separating the noise voltage.

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

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

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

[0078] It should be noted that FFT greatly reduces the amount of DFT calculations through specific algorithm structures (such as butterfly operations, etc.), thereby quickly converting time domain waveform data into frequency domain data. In the above scenario, FFT can be used to convert the common-mode and differential-mode noise voltage time domain waveform data collected by the oscilloscope into frequency domain data, and then obtain the common-mode and differential-mode noise data at the switching frequency point, which is convenient for analyzing the characteristics of noise at specific frequency points.

[0079] Furthermore, step S110 may include:

[0080] In step S111 , the common mode noise and the 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 the impedance characteristics of the circuit and Kirchhoff's law. Taking the common mode and differential mode signal separation of the present application as an example, under the equivalent circuit model, the working principle formula is:

[0082] ;

[0083] in, is the common mode noise voltage, is the differential mode noise voltage, is the noise voltage from the positive bus to the ground, is the noise voltage from the negative bus to the ground.

[0084] In step S112, the common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data are obtained by measuring with an oscilloscope according to the separated common mode noise and the differential mode noise.

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

[0087] In a possible implementation, 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 capacitor and a LISN impedance are constructed.

[0089] It should be noted that the common mode equivalent circuit and the differential mode equivalent circuit can be Figure 7-8 As shown in the figure, by abstracting the noise source, compensation voltage source, parasitic capacitance and LISN impedance in the actual circuit into a mathematical model, a simplified framework is provided for theoretical analysis to avoid complex actual circuit debugging; among them, the LISN impedance is represented by a resistor With capacitor Parallel composition.

[0090] In step S220, 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 according to the superposition cancellation principle, and a first formula is constructed.

[0091] In step S230, 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 according to the superposition cancellation principle, and a second formula is constructed.

[0092] In step S240, the common-mode compensation voltage amplitude and phase required at each switching frequency point are calculated according to the first formula, and the differential-mode compensation voltage amplitude and phase required at each switching frequency point are calculated according to the second formula.

[0093] In step S250, the common-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the common-mode compensation voltage data, and the differential-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the differential-mode compensation voltage data.

[0094] It should be noted that, for example, the switching frequency , then the switching frequency includes , , wait.

[0095] Furthermore, the first formula is:

[0096] ;

[0097] in, 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.

[0098] The second formula is:

[0099] ;

[0100] in, is the differential mode compensation voltage amplitude, is the differential mode compensation voltage phase, is the equivalent impedance of the input capacitor of the differential mode equivalent circuit, is the voltage amplitude of the differential mode noise source, is the voltage phase of the differential mode noise source.

[0101] It should be noted that , , ,in, , is the output filter capacitor, is the parasitic capacitance, is the LISN internal capacitance, is the input capacitance in the differential mode equivalent circuit.

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

[0103] ;

[0104] in, is the common mode compensation voltage data, is the switching frequency, For time.

[0105] The differential mode compensation voltage amplitude and phase of each switching frequency point are sinusoidally superimposed by a fourth formula, and the fourth formula is:

[0106] ;

[0107] in, It 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 to perform 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.

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

[0110] Optionally, the DAC may adopt a DAC with dual output terminals or use two DACs.

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

[0112] In step S310, 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.

[0113] In step S320, 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.

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

[0115] After step S300, the method further includes: step S400: measuring the noise voltage on the LISN as the noise source voltage, calculating iterative compensation voltage data, and superimposing it on the compensation voltage data to iterate the compensation voltage data.

[0116] It should be noted that by repeating the method of S100-S300, the compensation voltage is iterated to further improve the EMI suppression effect, such as Fig.10 As shown, two iterations can achieve a 15-40dB reduction in the low-frequency band of the common-mode noise spectrum and a 20-40dB reduction 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 , a noise voltage on the LISN is measured as a noise source voltage.

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

[0120] In step S430, iterative common-mode compensation voltage data and iterative differential-mode compensation voltage data of each frequency point are calculated according to the iterative common-mode noise data and the iterative differential-mode noise data to obtain iterative compensation voltage data.

[0121] In step S440, the iterative compensation voltage data is superimposed on the compensation voltage data and then outputted synchronously with the PWM through the DAC to perform 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 compensation voltage data sequence to eliminate the delay. The specific method can be to actually test 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 compensation voltage phase , aligned with the noise source.

[0123] Furthermore, in this exemplary embodiment, a voltage-type digital active EMI filter circuit based on switch spectrum analysis and reconstruction is provided, which is used to perform the above-mentioned voltage-type digital active EMI filter method based on switch spectrum analysis and reconstruction. Fig.11 As 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 common-mode noise data and differential-mode noise data of the buck circuit under test at the switching frequency point, and is used to calculate the common-mode compensation voltage data and differential-mode compensation voltage data of each frequency point based on the common-mode noise data and the differential-mode noise data to obtain compensation voltage data, and is used to control PWM and the DAC to output synchronously; the DAC is used to analog output 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 if Fig.11 As shown, the LISN contains a power supply Resistors in series ,inductance With capacitor , The low-pass filter and load resistor , used for impedance matching to ensure EMI measurement accuracy. The injection circuit includes a positive busbar injection inductor Injection inductor with negative bus , Connect to the positive bus to inject common mode and differential mode compensation voltage, Connect to the negative bus to inject common mode compensation voltage. The buck circuit under test includes: switch tube and , Switching tube parasitic capacitance , , Node switch , Connect inductor , Input Capacitance Output Capacitor ,load , output filter capacitor and , parasitic capacitance and drive ; control and Alternate conduction to achieve the voltage reduction function. Connect the switch node to the protective ground wire; when the switch tube is turned on or off, The point voltage changes at high frequency, through The common mode noise current is coupled to the protection ground line, 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 appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

[0128] The above embodiments are only used to illustrate the technical solution of the present application, but not to limit it. The present application is not limited to the exact structure described above and illustrated in the accompanying drawings, and it cannot be determined that the specific implementation of the present application is limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, various changes and modifications made without departing from the concept of the present application should be deemed to belong to 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: include: Obtain the common-mode noise data and differential-mode noise data of the Buck circuit at the switching frequency; 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, parasitic capacitance, and LISN impedance, calculate the common-mode compensation voltage data and the differential-mode compensation voltage data of each frequency point, and obtain the compensation voltage data; The compensation voltage data is output synchronously with PWM through DAC, and the compensation voltage data is injected into the positive bus and the negative bus through the injection inductor to perform 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 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.

2. The voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 1 is characterized in that: After the step of outputting the compensation voltage data synchronously with PWM through DAC, and injecting the compensation voltage data into the positive bus and the negative bus through injection inductance to perform noise compensation, the method further includes: The noise voltage on the LISN is measured as the noise source voltage, and iterative compensation voltage data is calculated and superimposed on the compensation voltage data to iterate the compensation voltage data.

3. The voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 1 is characterized in that: The step of obtaining common-mode noise data and differential-mode noise data of the Buck circuit at a switching frequency point includes: The common mode noise voltage time domain waveform data and the differential mode noise voltage time domain waveform data on the LISN are measured by a noise separator and an oscilloscope; The common-mode noise data and the differential-mode noise data at the switching frequency are obtained through FFT according to the common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data.

4. The voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 3 is characterized in that: 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 comprises: The common mode noise on the LISN is separated from the differential mode noise by a noise separator; The common-mode noise voltage time-domain waveform data and the differential-mode noise voltage time-domain waveform data are obtained by measuring with an oscilloscope according to the separated common-mode noise and the differential-mode noise.

5. The voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 1 is characterized in that: The steps of constructing a common-mode equivalent circuit and a differential-mode equivalent circuit including a noise source, a compensation voltage source, a parasitic capacitor and a LISN impedance, calculating common-mode compensation voltage data and differential-mode compensation voltage data at each frequency point, and obtaining compensation voltage data include: Constructing the common-mode equivalent circuit and the differential-mode equivalent circuit including a noise source, a compensation voltage source, a parasitic capacitor and a LISN impedance; According to the superposition and cancellation principle, the relationship between the common-mode compensation voltage data of the equivalent model and the common-mode voltage data of the noise source of the equivalent model is obtained, and the first formula is constructed; According to the superposition and 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; Calculate the common-mode compensation voltage amplitude and phase required at each switching frequency point according to the first formula, and calculate the differential-mode compensation voltage amplitude and phase required at each switching frequency point according to the second formula; The common-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the common-mode compensation voltage data, and the differential-mode compensation voltage amplitude and phase sine waves of each switching frequency point are superimposed to obtain the differential-mode compensation voltage data.

6. The voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 5 is characterized in that: The first formula is: ； in, 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; The second formula is: ； in, is the differential mode compensation voltage amplitude, is the differential mode compensation voltage phase, is the equivalent impedance of the input capacitor of the differential mode equivalent circuit, is the voltage amplitude of the differential mode noise source, is the voltage phase of the differential mode noise source.

7. The voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 5 is characterized in that: The common-mode compensation voltage amplitude and phase at each switching frequency point are sinusoidally superimposed by a third formula, and the third formula is: ； in, is the common mode compensation voltage data, is the switching frequency, For time; The differential mode compensation voltage amplitude and phase of each switching frequency point are sinusoidally superimposed by a fourth formula, and the fourth formula is: ； in, It is the differential mode compensation voltage data.

8. The voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 1 is characterized in that: The step of outputting the compensation voltage data synchronously with PWM through DAC, injecting the compensation voltage data into the positive bus and the negative bus through injection inductance to perform 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; 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.

9. The voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction according to claim 2 is characterized in that: The step of measuring the noise voltage on the LISN as the noise source voltage, calculating iterative compensation voltage data, and superimposing it on the compensation voltage data, and iterating the compensation voltage data includes: Measure the noise voltage on the LISN as the noise source voltage; Obtain iterative common-mode noise data and iterative differential-mode noise data through noise source voltage; Calculating 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 iterative compensation voltage data; After the iterative compensation voltage data is superimposed on the compensation voltage data, the data is output synchronously with the PWM through the DAC to perform noise compensation.

10. A voltage-type digital active EMI filter circuit based on switching spectrum analysis and reconstruction, characterized in that: The circuit is used to perform the voltage-type digital active EMI filtering method based on switching spectrum analysis and reconstruction as described in any one of claims 1 to 9, and the circuit includes an injection circuit and a digital control circuit; The digital control circuit comprises a digital controller and a dual-output DAC connected to each other; the digital controller is used to obtain common-mode noise data and differential-mode noise data of the buck circuit under test at a switching frequency point, and is used to calculate common-mode compensation voltage data and differential-mode compensation voltage data of each frequency point according to the common-mode noise data and the differential-mode noise data, and obtain compensation voltage data for controlling PWM and DAC output synchronization; The DAC is used to perform analog output of the compensation voltage data; The injection circuit comprises a positive bus injection inductor and a negative bus injection inductor, wherein 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 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.

Images