Power supply equipment conducted electromagnetic interference measurement and filtering test teaching experiment device and design method thereof

Abstract

The invention discloses a teaching experiment device for power supply equipment conducted electromagnetic interference measurement and filtering test, which comprises a conducted EMI experiment platform, and the conducted EMI experiment platform is provided with a conducted EMI experiment module, a conducted EMI measurement module and a computer which are connected in sequence. The invention also discloses a design method of the teaching experiment device for measuring the conducted electromagnetic interference of the power supply equipment and testing the filtering, the experiment device designed by the invention can reflect the influence of the working condition and condition change of the power supply on the transmission of the conducted electromagnetic interference in the experiment process, and meanwhile, the problem of crosstalk between cables is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of development of practical teaching devices for electrical majors in colleges and universities, and relates to a teaching experimental device for measuring conducted electromagnetic interference and filtering tests of power supply equipment. The invention also relates to a design method for the teaching experimental device for measuring conducted electromagnetic interference and filtering tests of power supply equipment. Background Art

[0002] At present, there is no systematic teaching demonstration for the standardized measurement of conducted electromagnetic interference, and there is no intuitive teaching demonstration equipment for the design of EMI filters. At present, mature filtering devices are designed for single types of filters such as passive EMI filters, active EMI filters and digital active EMI filters; however, for power supply equipment with wide bandwidth and complex electromagnetic environment, hybrid EMI filters that combine the advantages of various filters for filtering can better meet the needs of power supply equipment, but there is currently no device that can intuitively demonstrate the difference in filtering capabilities between hybrid filtering and single filtering under different power supply equipment. In addition, during the measurement of conducted electromagnetic interference, the placement of the power supply equipment and the layout of the connecting cables will affect the conducted electromagnetic interference, resulting in low measurement accuracy and inaccurate estimation of filtering performance. Summary of the invention

[0003] The purpose of the present invention is to provide a teaching experimental device for measuring conducted electromagnetic interference and filtering test of power supply equipment, through which switching between single filtering and mixed filtering in the teaching device can be realized, and the crosstalk problem between cables is solved at the same time.

[0004] Another object of the present invention is to provide a design method for a teaching experimental device for measuring and filtering the conducted electromagnetic interference of a power supply device.

[0005] The first technical solution adopted by the present invention is a power supply equipment conducted electromagnetic interference measurement and filtering test teaching experiment device, including a conducted EMI experiment platform, on which a conducted EMI experiment module, a conducted EMI measurement module, and a computer are connected in sequence.

[0006] The first technical solution of the present invention is also characterized in that:

[0007] The conducted EMI experiment module includes a measurement block, a filter block and a power load block which are connected in sequence.

[0008] The measurement panel includes two impedance stabilizers. The L and N AC power lines are connected to the two impedance stabilizers respectively. The PE line is first connected to the PE on-off module and then to the two impedance stabilizers. One end of the two impedance stabilizers is connected to one end of the filter mode switching module, and the other end of the filter mode switching module is the OUT output end.

[0009] The filter plate comprises a filter module. The input end and the output end of the filter module are respectively connected to a slide slot. Three wire clamps are equidistantly arranged on each slide slot.

[0010] The power load plate includes a test object module, the + line and the - line of the DC power line in the test object module are connected to the load module, the test object module is connected to one end of the controller, and the other end of the controller is respectively connected to the duty cycle regulator and the switching frequency regulator. A wire clamp is installed between the test object module and the controller to fix the signal line, and the wire clamp is installed on the slide slot.

[0011] The load module includes n load resistors and n load switching switches, and each load resistor is connected in series with a load switching switch.

[0012] The filter module includes L1, N1, and PE1 lines arranged in parallel, a passive filter module is connected in series on the L1, N1, and PE1 lines, and an active filter module and a digital active filter module are also connected in parallel on the L1, N1, and PE1 lines. Both ends of the passive filter module are respectively provided with a filter mode switching switch, and the active filter module and the digital active filter module are each provided with a filter mode switching switch on the connection line with the L1, N1, and PE1 lines.

[0013] The second technical solution adopted by the present invention is a design method for a teaching experimental device for measuring and filtering the conducted electromagnetic interference of power supply equipment, a conducted EMI experimental platform, a distance l1 between the impedance stabilizer and the test object module, and a spacing design of the line clamps.

[0014] The second technical solution of the present invention is also characterized in that:

[0015] The design process of the table height h of the conducted EMI experimental platform is as follows:

[0016] Based on the capacitive coupling mechanism of the power supply equipment, the power supply equipment generates parasitic capacitance C through the switch tube and the metal base plate. k , the table height h of the conducted EMI experimental platform and the parasitic capacitance C k The formula is:

[0017]

[0018] Where ε0 is the dielectric constant of vacuum; ε r1 is the relative dielectric constant; a SMPS is the length of the power supply equipment; b SMPS is the width of the power supply device; according to the common mode noise loop formed by the power supply device and the impedance stabilizer, the common mode noise loop satisfies the following equation:

[0019]

[0020] Among them, U CM is the common mode interference source voltage; I EMI is the common mode interference current; R LISN is the internal resistance of the impedance stabilizer; C LISN is the internal capacitance of the impedance stabilizer; C k is the parasitic capacitance between the switch tube and the metal base plate; f SMPS is the switching frequency of the switch tube;

[0021] The table height h of the conducted EMI test platform satisfies the following relationship:

[0022]

[0023] The distance between the conducted EMI experiment module and the rear metal side panel is x. Based on the capacitive coupling mechanism of the power supply device, a common mode noise loop is constructed. According to formulas (1) to (3), the size of x satisfies:

[0024]

[0025] Among them, x0 is the distance between the power supply equipment and the wall;

[0026] The design process of the distance l1 between the impedance stabilizer and the test object module is:

[0027] Based on the principle of conduction coupling, the common-mode circuits of the L line and the N line share the PE line. When there is interference current in the L line, the interference voltage generated on the L line will affect the N line, resulting in conduction coupling. According to the conduction coupling equivalent circuit of the L line common-mode loop, the following formula is obtained:

[0028]

[0029] Among them, k c is the crosstalk of L line to PE line; U CM is the common mode interference source voltage; Z L1 is the load impedance between L line and PE line; Z L2 is the load impedance between the N line and the PE line; Z S1 is the source impedance between L line and PE line; Z S2 is the source impedance between the N line and the PE line; Z C is the PE line impedance;

[0030] PE line impedance Z C The impedance Z is related to the distance l1 between the impedance stabilizer and the test object module. C It is expressed by formula (6):

[0031]

[0032] Among them, ρ lineis the resistivity of the conductor;

[0033] According to formula (5) and formula (6), the distance l1 between the impedance stabilizer and the test object module is:

[0034]

[0035] Among them, k c is the crosstalk of L line to PE line; Z L1 is the load impedance between L line and PE line, Z L2 is the load impedance between the N line and the PE line, Z S2 is the source impedance between the N line and the PE line, ρ line is the resistivity of the wire.

[0036] The design process of the spacing of the wire clamp is as follows:

[0037] The input and output ends of the filter module are respectively connected to a set of slides, and three wire clamps are arranged at equal intervals in each set of slides. At this time, the two sets of slides and the three corresponding wire clamps constitute H1 and H2; among them, H1 is located between the impedance stabilizer and the filter module; H2 is located between the filter module and the test object module; the distance d1 between the L line and the N line is adjusted by moving the wire clamp on the slide, and the design process of the distance d1 between the L line and the N line is:

[0038] Based on the electric field coupling theory, when the common mode noise voltage exists, the L line and the N line are close to each other and a coupling capacitor C is generated. LN , and then crosstalk is generated between the L line and the N line. According to the equivalent circuit of the capacitive coupling between the L line and the N line, the following formula (8) is obtained:

[0039]

[0040] Among them, k t is the crosstalk of L line to N line; Z L1 is the load impedance between L line and PE line; Z L2 is the load impedance between the N line and the PE line; Z S1 is the source impedance between L line and PE line; Z S2 is the source impedance between the N line and the PE line; C LG is the capacitance of L line to ground; C NG is the capacitance of N line to ground; C LN is the coupling capacitance between the L line and the N line; f SMPS is the switching frequency of the switch tube;

[0041] According to the principle of capacitance between conductors, the L line and the N line generate coupling capacitance at high frequencies. LN The capacitance C is related to the distance d1 between the two lines. LNIt is expressed by formula (9):

[0042]

[0043] Where, ε0 is the dielectric constant of air; d1 is the distance between L line and N line; l1 is the distance between the impedance stabilizer and the test object module; r line is the radius of the wire;

[0044] According to the principle of parallel plate capacitor, the L line and the N line generate a L line to ground capacitance C at high frequency. LG and an N-line to ground capacitor C NG , these two capacitors are related to the height h of the conduction EMI experimental platform. The capacitor C LG and C NG It is expressed by formula (10):

[0045]

[0046] Where, l1 is the distance between the impedance stabilizer and the test object module; r line is the radius of the wire;

[0047] According to formula (8) to formula (10), the distance d1 between line L and line N is:

[0048] d1=2r line e m (11)

[0049] in:

[0050]

[0051] k t is the crosstalk of L line to N line, ε0 is the relative dielectric constant; Z L1 is the load impedance between L line and PE line, Z S1 is the source impedance between L line and PE line, f SMPS is the switching frequency of the switch tube; in order to balance the common mode interference between the L line and the N line, the distance from the PE line to the L line and the distance from the PE line to the N line are

[0052] A wire clamp is installed between the test object module and the controller to fix the signal line. The wire clamp is installed on the slide slot to form H3. The distance d2 between the signal line of the controller and the power supply line is adjusted by moving the wire clamp on the slide slot. Based on the electric field coupling theory, according to formulas (8) to (12), the distance d2 between the signal line of the controller and the power supply line satisfies the following relationship:

[0053] d2=2r line e n (13)

[0054] in:

[0055]

[0056] The beneficial effect of the present invention is that the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device proposed by the present invention takes into account the generation mechanism of conducted electromagnetic interference and the influencing factors of conducted electromagnetic interference of power supply equipment, and designs a teaching device that can demonstrate the emission process of electromagnetic interference of power supply equipment changing with the test conditions. In the design method of the device of the present invention, starting from the suppression ability of the filter on the filtered system, the impedance mismatch effect between the filter and the source impedance and the load impedance is considered. By designing the filter module in the device, the filtering performance test of the filtered object by passive, active, digital active and hybrid filtering can be realized. In the design method of the device of the present invention, the crosstalk problem between cables is taken into account, and the layout parameters of the cables can be quantitatively obtained, thereby improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a structural schematic diagram of a teaching experimental device for measuring and filtering the conducted electromagnetic interference of a power supply device of the present invention;

[0058] Figure 2 It is a structural diagram of the conducted EMI experiment module of the teaching experiment device for conducting electromagnetic interference measurement and filtering test of power supply equipment of the present invention;

[0059] Figure 3 A structural diagram of a filter module of the teaching experimental device for measuring and filtering the conducted electromagnetic interference of a power supply device of the present invention;

[0060] Figure 4 It is a conducted EMI emission measurement waveform diagram of the conducted electromagnetic interference measurement and filtering test teaching experimental device of the power supply equipment of the present invention;

[0061] Figure 5 It is a passive filtering mode performance test waveform diagram of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device of the present invention;

[0062] Figure 6 It is a performance test waveform diagram of active filter mode of the teaching experimental device for measuring conducted electromagnetic interference and filtering test of power supply equipment of the present invention;

[0063] Figure 7 This is a performance test waveform diagram of the passive and active filtering mixed mode of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device of the present invention.

[0064] In the figure, 1. Conducted EMI experiment module, 2. Conducted EMI measurement module, 3. Computer, 4. Conducted EMI experiment platform, 5. Impedance stabilizer, 6. Filter module, 7. Test object module, 8. Load module, 9. Controller, 10. Filter mode switching module, 11. Load resistor, 12. CM / DM calculation module, 13. Slide, 14. Wire clamp, 15. PE on-off module, 16. Load switching switch, 17. Filter mode switching switch, 18. Duty cycle regulator, 1 9. Switching frequency regulator, 20. Passive filter module, 21. Active filter module, 22. Digital active filter module, 23. Filter module switching switch, 24. Passive filter device cut-in switch, 25. Filter inductor, 26. Filter capacitor, 27. Detection network, 28. Operation network, 29. Injection network, 30. ADC module, 31. FPGA module, 32. DAC module, 33. Amplification network, 34. Measurement section, 35. Filter section, 36. Power supply load section. DETAILED DESCRIPTION

[0065] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0066] Example 1

[0067] The present invention provides a teaching experimental device for measuring and filtering the conducted electromagnetic interference of a power supply device. Figure 1 As shown, it includes a conducted EMI experiment module 1, a conducted EMI (Electro Magnetic Interference) measurement module 2, a computer 3 and a conducted EMI experiment platform 4. The conducted EMI experiment module 1 is composed of three major blocks: a measurement block 34, a filter block 35 and a power supply load block 36. The conducted EMI measurement module 2 uses Rohde & Schwarz It can measure the conducted EMI spectrum of the switching power supply. Computer 3 uses Lenovo's Ideapad 330, which uses the Win10 operating system and is equipped with EMI spectrum measurement host computer software, which can display and control the EMI spectrum measured by the conducted EMI measurement module 2. The measurement board 34 in the conducted EMI experiment module 1 and the conducted EMI measurement module 2 are connected by an RF cable, and the conducted EMI measurement module 2 and the computer 3 communicate via Ethernet. The conducted EMI experiment module 1, the conducted EMI measurement module 2 and the computer 3 are located on the table of the conducted EMI experiment platform 4.

[0068] The structure diagram of the conducted EMI experiment module of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experiment device of the present invention is as follows Figure 2 As shown, it includes three blocks: a measurement block 34 , a filter block 35 and a power load block 36 .

[0069] Example 2

[0070] The measurement block 34 includes an impedance stabilizer 5, a filter mode switching module 10 and a PE on-off module 15. The connection relationship of each module is as follows: the L and N AC power lines are connected to the two impedance stabilizers 5 respectively, the PE line is first connected to the PE on-off module 15 and then connected to the two impedance stabilizers 5, and the two impedance stabilizers 5 are connected together; one end of the filter mode switching module 10 is connected to the two impedance stabilizers 5, and the other end is the OUT output end. The filter mode switching module 10 is composed of a CM / DM calculation module 12 and a filter mode switching switch 17. The PE (Protective Earthing) on-off module 15 can change the conducted EMI experiment module 1 into two modes, grounded and ungrounded, so that students can understand and analyze the flow loop of the conducted EMI of the system with and without ground wires. The impedance stabilizer 5 can provide a stable 50Ω load impedance. The CM / DM (Common Mode / Differential Mode) calculation module 12 can calculate the conducted EMI on the L line and the N line, thereby obtaining the CM and DM noise on the line. The filter mode switch 17 can select the conducted EMI to be measured.

[0071] Example 3

[0072] The filter block 35 includes a filter module 6, a chute 13 and a wire clamp 14. The connection relationship between each module is as follows: the input and output ends of the filter module 6 are connected to a chute 13 and three wire clamps 14; each wire clamp 14 fixes a wire on the input and output ends of the filter module 6, and three wire clamps 14 on each side are installed on a chute 13, forming two groups H1 and H2. The chute 13 and the wire clamp 14 fix the connection lines between each block and control the distance of the connection lines, thereby reducing the interference problem between the L line and the N line.

[0073] Example 4

[0074] The power load block 36 includes a test object module 7, a load module 8, a controller 9, a slide 13, a wire clamp 14, a duty cycle regulator 18 and a switching frequency regulator 19. The connection relationship between each module is as follows: the + line and the - line of the DC power line coming out of the test object module 7 are connected to the load module 8; one end of the controller 9 is connected to the test object module 7, and the other end of the controller 9 is connected to the duty cycle regulator 18 and the switching frequency regulator 19. A wire clamp 14 is installed between the test object module 7 and the controller 9 to fix the signal line; the wire clamp 14 is installed on the slide 13 to form a group H3. The load module 8 includes R1, R2 to R nThere are n load resistors 11 and n load switching switches 16 from K1, K2 to Kn, and each load resistor 11 is connected in series with a load switching switch 16. The corresponding load is connected by pressing different load switching switches 16. The PWM output of the controller 9 is changed by rotating the knobs of the duty cycle regulator 18 and the switching frequency regulator 19, thereby changing the working conditions of the switch tube of the test object module 7, thereby controlling the test object module and the entire EMI experiment module. The slide 13 and the wire clamp 14 fix the signal line between the test object module 7 and the controller 9, and control the distance between the signal line and the DC power line, thereby reducing the interference problem between the power line and the signal line.

[0075] The impedance stabilizer 5 in the measurement block 34 is connected to H1 consisting of a slide slot 13 and three wire clamps 14 in the filter block 35; the test object module 7 in the power load block 36 is connected to H2 consisting of a slide slot 13 and three wire clamps 14 in the filter block 35.

[0076] Example 5

[0077] The structure diagram of the filter module 6 of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device of the present invention is as follows Figure 3As shown, it includes a passive filter module 20, an active filter module 21, a digital active filter module 22, a filter mode switching switch 23 and three power lines L1, N1, and PE1. A passive filter module 20 is connected in series on the L1, N1, and PE1 lines of the filter module 6, and the active filter module 21 and the digital active filter module 22 are connected in parallel on the L1, N1, and PE1 lines. There is a filter mode switching switch 23 at both ends of the passive filter module 20, and the filter mode switching switches are T2 and T3, and a branch of the filter mode switching switch 23 is connected in parallel on the outside of the two filter mode switching switches 23, and the switch on the branch is T1. There is a filter mode switching switch 23 on the connection line between the active filter module 21 and the digital active filter module 22 and the L1, N1, and PE1 lines, which are T4, T5, T6, and T7 respectively. Students can connect different filters to the filtered system by toggling different filter mode switching switches 23. They can test the filtering performance of a single filter, or the mixed filtering performance of passive and active, digital and analog filters. And by switching the filter mode switching switch 23, it is very convenient to connect and disconnect the filter in the filtered system, which is convenient for calculating the insertion loss IL. The passive filter module 20 includes a passive filter structure switching switch 24, a filter inductor 25 and a filter capacitor 26. There are 12 passive filter structure switching switches 24, namely S1, S2 to S12; there are 6 filter inductors 25, all of which are connected in series between the L1 and N1 lines, represented by L; there are 6 filter capacitors 26, two of which are connected in parallel between the L1 and N1 lines, represented by C x Indicates that there are four parallel connections between L1 or N1 and PE1, with C y Students connect different filter inductors 25 and filter capacitors 26 to the circuit by turning on and off different passive filter structure switching switches 24, thereby forming common-mode or differential-mode passive EMI filters of different structural types, such as C-type, L-type, Γ-type, reverse Γ-type, T-type and Π-type.

[0078] The active filter module 21 includes a detection network 27 , a calculation network 28 and an injection network 29 .

[0079] The digital active filter module 22 includes a detection network 27, an injection network 29, an ADC (Analog to Digital Converter) module 30, an FPGA (Field Programmable Gate Array) module 31, a DAC (Digital to Analog Converter) module 32 and an amplification network 33. This filter module is used as a conducted EMI suppressor in the teaching process of students completing the conducted electromagnetic interference suppression experiment of the switching power supply. It combines the emerging technology of conducted EMI filters, allowing students to master the knowledge points of active EMI filters, digital active EMI filters and hybrid filter suppression while learning the filter suppression principle and filter selection. It allows students to intuitively feel the impact of different filters on the filtering performance, as well as the changes in the filtering performance caused by the hybrid filter.

[0080] The conducted EMI emission measurement waveform of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device of the present invention is as follows Figure 4 As shown (no filter power supply is added), this waveform is a measured waveform of the conducted EMI emission on the L line of the test object with a duty cycle of 50%, a switching frequency of 150kHz, and a load resistance of 50Ω in the unfiltered mode. Among them, switches K3 (n=3 in the load switching switch 16) and T1 are closed, the other switches are open, and the filter mode switching switch selects the L line of the switching power supply. The waveform is a frequency domain waveform with a frequency of 150kHz to 30MHz and an amplitude of 23dBμV to 67dBμV. In the waveform, 20 frequency points exceed the specified horizontal line on the figure, and the maximum exceeds 12dB.

[0081] The passive filtering mode performance test waveform of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device of the present invention is as follows: Figure 5 As shown, the waveform is a measured waveform of the conducted EMI emission on the L line when the test object with a duty cycle of 50%, a switching frequency of 150kHz, and a load resistance of 50Ω is selected in the passive filtering mode, and the L line-common mode-T type passive EMI filter is selected. Among them, the switch K3 (n=3 in the load switching switch 16), T2, T3, S3, S4, S5, S6 and S9 are closed, and the other switches are open, and the filter mode switching switch selects the L line of the switching power supply. The waveform is a frequency domain waveform with a frequency of 150 to 30MHz and an amplitude of 20dBμV to 57dBμV. In the waveform, all frequency points are lower than the specified horizontal line on the figure, and the difference between them and the specified horizontal line is 10 to 20dB.

[0082] The performance test waveform of the active filter mode of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device of the present invention is as follows: Figure 6 As shown, the waveform is a measured waveform of the conducted EMI emission on the L line of the test object with a duty cycle of 50%, a switching frequency of 150kHz, and a load resistance of 50Ω in the active filtering mode. Among them, switch K3 (n=3 in the load switching switch 16), T1, T4 and T5 are closed, and the remaining switches are open, and the filter mode switching switch selects the L line of the switching power supply. The waveform is a frequency domain waveform with a frequency of 150kHz to 30MHz and an amplitude of 20dBμV to 37dBμV. In the waveform, all frequency points are lower than the specified horizontal line on the figure, and the difference between them and the specified horizontal line is 20 to 25dB.

[0083] The passive and active filtering mixed mode performance test waveform of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device of the present invention is as follows: Figure 7 As shown, the waveform is a test object with a duty cycle of 50%, a switching frequency of 150kHz, and a load resistance of 50Ω in a passive and active filtering mixed mode, and the passive selection of the L-line-common-mode-T-type passive EMI filter, and the measured L-line conducted EMI emission measurement waveform. Among them, switch K3 (n=3 in the load switching switch 16), T2, T3, T4, T5, S3, S4, S5, S6 and S9 are closed, and the remaining switches are open, and the filter mode switching switch selects the L line of the switching power supply. The waveform is a frequency domain waveform, with a frequency of 150kHz to 30MHz and an amplitude of 20dBμV to 33dBμV. In the waveform, all frequency points are lower than the specified horizontal line on the figure, and the difference between them and the specified horizontal line is 25 to 30dB.

[0084] Example 6

[0085] The design method of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device of the present invention is as follows:

[0086] (1) Design of the Conductive EMI Experimental Platform 4: The bottom surface of the Conductive EMI Experimental Platform 4 is a metal bottom plate, the rear side is a metal side plate, and the rest are made of non-conductive wood materials, and these two metal plates are connected to the ground. In order to ensure that a sufficiently large amount of conducted electromagnetic interference can be measured in experimental teaching, and considering the working scene of the power supply equipment, the table height h of the entire Conductive EMI Experimental Platform 4 is designed: Based on the capacitive coupling mechanism of the power supply equipment, the power supply equipment generates a parasitic capacitance C through the switch tube and the metal bottom plate k , the height of the table h and the parasitic capacitance C k The formula is:

[0087]

[0088] Where ε0 is the dielectric constant of vacuum; ε r1is the relative dielectric constant of the wooden table between the power supply device and the metal base plate (its dielectric constant is 4); a SMPS is the length of the power supply equipment; b SMPS is the width of the power supply device; only when there is a common-mode noise loop, the common-mode electromagnetic interference of the power supply device will exist. According to the common-mode noise loop formed by the power supply device and the impedance stabilizer, the KVL equation of the loop is:

[0089]

[0090] Among them, U CM is the common mode interference source voltage; I EMI is the common mode interference current; R LISN is the internal resistance of the impedance stabilizer; C LISN is the internal capacitance of the impedance stabilizer; C k is the parasitic capacitance between the switch tube and the metal base plate; f SMPS is the switching frequency of the switch tube. From formula (1), we can know that the larger the height h of the table, the greater the parasitic capacitance C generated by the switch tube and the metal base plate. k From formula (2), we can know that the parasitic capacitance C generated by the switch tube and the metal base plate is k The smaller the common mode interference current I EMI The smaller the electromagnetic interference noise is, the voltage across the internal resistor of the impedance stabilizer is measured. This voltage is related to the common mode interference current I EMI In order to prevent the electromagnetic interference noise voltage measured by students from being too low and not conducive to teaching demonstration, it is stipulated that the minimum noise voltage should not be less than one tenth of the common mode interference source voltage. At the same time, in order to simulate the working scene of the power supply equipment, the height of the table should not be lower than the height of the common power supply equipment from the ground. Based on this, the table height h of the conducted EMI experimental platform 4 can be derived as follows:

[0091]

[0092] Among them, h0 is the height of common power supply equipment from the ground. For equipment below 500W, h0 is 0.8m; ε0 is the vacuum dielectric constant; ε r1 is the relative dielectric constant of the wooden table between the power supply device and the metal base plate (its dielectric constant is 4); a SMPS is the length of the power supply equipment; b SMPS is the width of the power supply device; R LISN is the internal resistance of the impedance stabilizer; C LISN is the internal capacitance of the impedance stabilizer; f SMPSis the switching frequency of the switch tube. The distance from the conducted EMI experiment module 1 to the rear metal side panel is x. In order to ensure that a sufficiently large conducted electromagnetic interference can be measured in the experimental teaching, and to prevent the conducted electromagnetic interference from being too large and causing damage to the power supply equipment, a common-mode noise loop is constructed based on the capacitive coupling mechanism of the power supply equipment. According to formulas (1) to (3), the size of x should satisfy:

[0093]

[0094] Among them, x0 is the distance between the common power supply equipment and the wall, which is generally 0.1m; ε0 is the vacuum dielectric constant; ε r2 is the relative dielectric constant of the air between the power supply device and the metal side plate (its dielectric constant is 1.00053); a SMPS is the length of the power supply device; c SMPS is the high of the power supply equipment; R LISN is the internal resistance of the impedance stabilizer; C LISN is the internal capacitance of the impedance stabilizer; f SMPS is the switching frequency of the switch tube. When simulating a desktop power supply device, the table height h of the conducted EMI experimental platform 4 is designed according to formula (3), and the distance x from the conducted EMI experimental module 1 to the rear metal side panel is 0.1m; when simulating a wall-mounted power supply device, the table height h of the conducted EMI experimental platform 4 is 0.8m, and the distance x from the conducted EMI experimental module 1 to the rear metal side panel is designed according to formula (4).

[0095] (2) Design of impedance stabilizer 5: When testing the filter performance, in order to facilitate the impedance matching problem of the load impedance, a stable 50Ω load impedance needs to be provided at the input end. Therefore, the Rohde & Schwarz V-NETWORK ESH3-Z6 model is selected.

[0096] (3) Design of the test object module 7: For the test object module 7, the present invention is aimed at the conducted electromagnetic interference of the switching power supply, so the test object module 7 uses a switching power supply module with controllable switching tubes. The switching power supply module is designed as a switching power supply combined with AC / DC and DC / DC. The AC / DC uses a bridge full-controlled rectifier circuit, and the DC / DC uses a flyback circuit. The input voltage of the switching power supply is 220VAC, the output voltage is adjustable to 5-48V DC, and the switching frequency of the switching tube is adjustable between 50kHz-200kHz. For the driving circuit of the switching tube, Infineon's 1ED020I12-F2 driver chip is used to drive the switching tube to work.

[0097] (4) Design of the distance l1 between the impedance stabilizer 5 and the test object module 7: In the present invention, in order to improve the accuracy of the measured conducted electromagnetic interference of the test object, to facilitate students to understand the conducted electromagnetic interference characteristics of the L line and the N line, and to reduce the influence of the crosstalk between the L line and the N line on the test results, it is necessary to design the distance l1 between the impedance stabilizer 5 and the test object module 7: Based on the conduction coupling theory, the common mode circuits of the L line and the N line both share the PE line. When there is an interference current in the L line, the interference voltage generated on the L line will affect the N line, resulting in conduction coupling. According to the conduction coupling equivalent circuit of the L line common mode loop, it can be obtained:

[0098]

[0099] Among them, k c is the crosstalk of L line to PE line; U CM is the common mode interference source voltage; Z L1 is the load impedance between L line and PE line; Z L2 is the load impedance between the N line and the PE line; Z S1 is the source impedance between L line and PE line; Z S2 is the source impedance between the N line and the PE line; Z C is the PE line impedance. PE line impedance Z C The impedance Z is related to the distance l1 between the impedance stabilizer 5 and the test object module 7. C It can be expressed by formula (6), where ρ line is the resistivity of the conductor;

[0100] Z C =ρ line l1 (6)

[0101] According to formula (5) and formula (6), the distance l1 between the impedance stabilizer 5 and the test object module 7 can be obtained as:

[0102]

[0103] Among them, k c is the crosstalk between L line and PE line, take 0; Z L1 is the load impedance between the L line and the PE line, 50Ω provided by the impedance stabilizer; Z L2 is the load impedance between the N line and the PE line, 50Ω provided by the impedance stabilizer; Z S2 is the source impedance between the N line and the PE line, which is 50Ω; line is the resistivity of the wire.

[0104] (5) Design of controller 9: In the present invention, in order to be able to perform real-time control on the test object module 7 and adjust the duty cycle and switching frequency of the switch tube, the TMS320F28335 real-time microcontroller of Texas Instruments is selected.

[0105] (6) Design of duty cycle regulator 18 and switching frequency regulator 19: The design parameters of duty cycle regulator 18 and switching frequency regulator 19 are exactly the same, and the selected models are also exactly the same. In order to facilitate students to intuitively adjust the duty cycle and switching frequency of the switch tube of the test object module, a potentiometer model 3590S-2-103L is selected. The precision of the potentiometer is ±5%, and the rated power is 2W.

[0106] (7) Design of load module 8: There are n load resistors 11 and n load switching switches 16 on the load module 8. According to the output voltage of the switching power supply combined with different load resistors, load powers P0 of different power levels can be simulated. Students can connect different loads by pressing different load switching switches 16 according to the required load power level. The present invention will take 3 load resistors and 3 load switching switches as an example to describe the switching strategy for power realization of the power supply device. Among them, the load resistors are R1=10Ω, R2=20Ω and R3=50Ω respectively, and the rated output voltage U0 of the switching power supply is 48V.

[0107] Calculate the maximum rated power P of the load resistor according to the rated output voltage U0 of the test object emax for: Where R1||R2 is the minimum load resistance under the switch switching strategy example. Because 345.43W<400W, based on this, the power of the load resistance selected by the present invention is 400W. The selected load resistor is from Fenghua High-Tech. A load switching switch 16 is connected in series on the branch of each load resistor, for a total of 3. The design parameters of these 3 load switching switches are exactly the same, and the selected models are also exactly the same. According to the maximum current and voltage on the output side, the present invention selects a single-pole single-throw button switch M2011B2B1W02, with a rated voltage of 125V and a rated current of 4A.

[0108] The switching strategy for power supply device power implementation is as follows:

[0109] When simulating power devices with power below 100W, such as chargers, the load power P0 satisfies At this time, switch K3 should be closed and switches K1 and K2 should be opened;

[0110] When simulating a laptop computer or other power supply device with a power of 100-150W, the load power P0 satisfies At this time, switch K2 should be closed and switches K1 and K3 should be opened;

[0111] When simulating a power supply device with a power of 150-200W, such as a TV, the load power P0 satisfies At this time, switches K2 and K3 should be closed, and switch K1 should be opened;

[0112] When simulating a power supply device with a power of 200-250W, such as a refrigerator, the load power P0 satisfies At this time, switch K1 should be closed and switches K2 and K3 should be opened;

[0113] When simulating a power supply device with a power of 250-300W, such as a water dispenser, the load power P0 satisfies At this time, switches K1 and K3 should be closed, and switch K2 should be opened;

[0114] When simulating a power supply device with a power of 300-350W, such as a washing machine, the load power P0 satisfies At this time, switches K1 and K2 should be closed and switch K3 should be opened.

[0115] For example, when U0 is 48V, if we want to simulate the conducted electromagnetic interference of energy-saving lamps, considering that the power of energy-saving lamps is below 100W, it meets At this time, the switch K3 is closed, and the switches K1 and K2 are opened. When power supply devices of other power levels are to be simulated, the switch switching strategy is similar.

[0116] The present invention takes three load resistors as an example and can simulate the conducted electromagnetic interference of a power supply device with a power below 350W. If the power level of the power supply device is to be increased or the power level of the power supply device is to be subdivided, the number of load resistors can be increased and load resistors with different resistance values ​​can be selected.

[0117] (8) Design of PE on-off module 15: The PE on-off module 15 of the present invention changes the entire conducted EMI measurement module 2 into two situations: with a PE ground wire and without a PE ground wire by connecting and disconnecting the interface. The PE on-off module 15 uses a banana connector for connection. Because it is installed at the input end of the conducted EMI measurement module 2, the 25.502.1 banana connector of ams is selected. The rated voltage of the product is 600V and the rated current is 32A.

[0118] (9) Design of the spacing of the wire clamp 14: The present invention has three sets of slides and wire clamps, of which H1 and H2 are composed of one slide and three wire clamps, which are located between the impedance stabilizer 5 and the filter module 6 and between the filter module 6 and the test object module 7. The distance d1 between the L line and the N line can be adjusted by moving the wire clamp on the slide. The design of the distance d1 between the L line and the N line is as follows: Based on the electric field coupling theory, when the common mode noise voltage exists, the L line and the N line will be close to each other and a coupling capacitor C will be generated. LN, and then crosstalk occurs between the L line and the N line. According to the equivalent circuit of capacitive coupling between the L line and the N line, we can get:

[0119]

[0120] Among them, k t is the crosstalk of L line to N line; Z L1 is the load impedance between L line and PE line; Z L2 is the load impedance between the N line and the PE line; Z S1 is the source impedance between L line and PE line; Z S2 is the source impedance between the N line and the PE line; C LG is the capacitance of L line to ground; C NG is the capacitance of N line to ground; C LN is the coupling capacitance between the L line and the N line; f SMPS is the switching frequency of the switch tube.

[0121] According to the principle of capacitance between conductors, the L line and the N line will generate coupling capacitance at high frequencies (above 20kHz). LN The capacitance C is related to the distance d1 between the two lines. LN It can be expressed by formula (9).

[0122]

[0123] Where, ε0 is the dielectric constant of air; d1 is the distance between L line and N line; l1 is the distance between the impedance stabilizer and the test object module; r line is the radius of the wire.

[0124] According to the principle of parallel plate capacitor, the L line and the N line will generate an L line to ground capacitance C at high frequency. LG and an N-line to ground capacitor C NG , these two capacitors are related to the height h of the conduction EMI experimental platform. LG and C NG It can be expressed by formula (10).

[0125]

[0126] Among them, ε0 is the relative dielectric constant; ε r1 is the relative dielectric constant of the wooden table between the power supply device and the metal base plate (its dielectric constant is 4); h is the height of the table of the conducted EMI experimental platform; l1 is the distance between the impedance stabilizer and the module of the test object; r line is the radius of the conductor. According to formula (8) to formula (10), the distance d1 between line L and line N can be obtained as:

[0127] d1=2rline e m (11)

[0128]

[0129] Among them, k t is the crosstalk of L line to N line, which is taken as 0; ε0 is the relative dielectric constant; ε r1 is the relative dielectric constant of the wooden table between the power supply device and the metal base plate (its dielectric constant is 4); Z L1 is the load impedance between the L line and the PE line, 50Ω provided by the impedance stabilizer; Z S1 is the source impedance between L line and PE line, take 50Ω; f SMPS is the switching frequency of the switch tube; h is the height of the tabletop of the conducted EMI experimental platform; l1 is the distance between the impedance stabilizer and the module of the test object; r line is the radius of the wire. In order to balance the common mode interference between the L line and the N line, the distance from the PE line to the L line and the N line should be consistent, that is, the distance from the PE line to the L line and the distance from the PE line to the N line are H3 is composed of a slide and a wire clamp, which is located between the test object module 7 and the controller 9. By moving the wire clamp on the slide, the distance d2 between the signal line of the controller and the power supply line can be adjusted. Based on the electric field coupling theory, according to formulas (8) to (12), the design of the distance d2 between the signal line of the controller and the power supply line can be obtained:

[0130] d2=2r line e n (13)

[0131]

[0132] Where: k s is the crosstalk of the power line to the signal line, which is taken as 0; ε0 is the relative dielectric constant; ε r1 is the relative dielectric constant of the wooden table between the power supply device and the metal base (its dielectric constant is 4); Z L is the load impedance on the output side of the power line; Z Lx is the load impedance of the signal line to ground, which is 50Ω; Z S is the source impedance of the power line to ground, which is 50Ω; Z Sx is the source impedance of the signal line to ground, which is 50Ω; f SMPS is the switching frequency of the switch tube; h is the height of the tabletop of the conducted EMI experimental platform; l2 is the wire length of the power line; l3 is the wire length of the signal line; r line is the radius of the wire. For the distance d2 between the controller's signal line and the power supply line, the load impedance Z at the output side of the power line LFor this load impedance, Z L In the present invention, the resistance value is consistent with the load resistance. Therefore, when different load resistances are selected to simulate power supply devices of different powers, the distance d2 between the signal line of the controller and the power supply line will be adjusted according to formula (13).

[0133] (10) Design of filter mode switching module 10: The filter mode switching module 10 is composed of a CM / DM calculation module 12 and a filter mode switching switch 17. The CM / DM calculation module 12 uses CYBERTEK's EM5016A, which can process the conducted EMI on the L line and the N line, thereby obtaining the CM and DM noise on the line. The filter mode switching switch 17 uses a four-contact rotary switch MFR01-A2F03LIS-R, which can select the display of the conducted EMI of the L line, N line, CM and DM of the switching power supply. Figure 3 The filter module 6, the design process is as follows:

[0134] (1) Design of filter module switching switch 23: In order to switch between different filters, to open and close the L line, N line and PE line at the same time, considering that the voltage of the main line is 220VAC, the filter module switching switch 23 adopts a three-pole single-throw button switch 651H / 2, whose rated voltage is 250VAC and rated current is 15A. Students switch between different filters by toggling different filter mode switching switches 23, and the filter mode switching is shown in Table 1. It can be switched to a single filter or to a mixed filter between passive and active, digital and analog. It can demonstrate the filtering performance of a single filter to students, and it can also demonstrate the mixed filtering capability under complex working conditions. In addition, it is also very convenient to switch between modes with and without filters, which is convenient for students to measure and calculate the insertion loss IL.

[0135] Table 1 Filter mode switching table

[0136]

[0137]

[0138] (2) Design of passive filter module 20: The passive filter module 20 includes 12 passive filter structure switching switches 24, 6 filter inductors 25 and 6 filter capacitors 26. The passive filter structure switching switch 24 adopts a single-pole single-throw toggle switch 631H / 2, whose rated voltage is 250V and rated current is 15A. The filter inductor 25 is L=5mH, and the filter capacitor 26 is divided into a common mode capacitor C y And differential mode capacitance C x , the value is C y =1μF and C x=470nF. The selected filter inductor and filter capacitor are from Fenghua High-Tech. The passive filter module 20 takes into account the source impedance Z of the filtered system. S and load impedance Z L By turning on and off the different passive filter structure switching switches 24, different filter inductors 25 and filter capacitors 26 are connected to the circuit, and the source impedance Z S and load impedance Z L Impedance matching is performed to form common mode or differential mode passive EMI filters of different structural types, such as C-type, L-type, Γ-type, reverse Γ-type, T-type and Π-type. The method table of the passive EMI filter filter environment impedance matching method of the passive filter module 20 is shown in Table 2.

[0139] Table 2 Passive EMI filter filter environment impedance matching method table

[0140]

[0141]

[0142] For example, when a passive EMI filter is needed to filter the differential-mode conducted electromagnetic interference of a power supply device, the source impedance Z S Close to 0, load impedance Z L If it is also close to 0, then a T-type differential mode passive EMI filter will be selected, and students will close switches S3, S4, S5, S6, and S7 and open switches S1, S2, S8, S9, S10, S11, and S12 to achieve this. For other passive filters, the selection method is the same.

[0143] (3) Design of active filter module 21: The active filter module 21 is an active EMI filter designed based on operational amplifier OPA656 and having a detection network 27, an operation network 28 and an injection network 29. The detection network uses voltage detection, and the injection network uses current injection.

[0144] (4) Design of digital active filter module 22: The digital active filter module 22 is a digital active EMI filter with a detection network 27, an ADC module 30, a DAC module 32, an amplification network 33 and an injection network 29 designed based on an FPGA module 33. The model of the FPGA module 31 is EP4CE10F1717, the model of the ADC module 30 is LTC2240, the model of the DAC module 32 is AD9742, and the model of the amplification network 33 is OPA847.

[0145] The method for using the teaching experimental device for measuring and filtering the conducted electromagnetic interference of power supply equipment and power supply equipment of the present invention is specifically implemented according to the following steps: for the experimental teaching of the influencing factors of conducted EMI, the student connects the PE on-off module 15 to make the conducted EMI experimental module 1 in the mode of the grounding wire, and the student disconnects the PE on-off module 15 to make the conducted EMI experimental module 1 in the mode without the grounding wire. The student changes the voltage of the test object by rotating the duty cycle regulator 18, and changes the switching frequency of the test object by rotating the switching frequency regulator 19. The student connects different loads by pressing different load switching switches 16, thereby changing the power size of the test object. The conducted EMI of the power supply equipment under different working conditions is shown to the students through the changes of grounding and ungrounding and the changes of the test object. For the measurement and display of conducted EMI, the student controls the EMI measurement module 2 through the computer 3 to measure the conducted EMI spectrum, and the measurement results are displayed in the upper computer software of the computer. The student selects the conducted EMI spectrum waveform to be measured by toggling the filter mode switching switch 17.

[0146] For the filter performance test experimental teaching, after learning the conducted EMI emission measurement of the power supply equipment, students need to learn the method of suppressing conducted EMI and the suppression ability of different filters. Under different operating conditions of the power supply equipment, different filter modules are connected to the experimental system by toggling the filter module switching switch 23. Students can learn the filtering capabilities and respective characteristics of the three types of filters: passive EMI filters, active EMI filters, and digital active EMI filters, as well as the mixed filtering capabilities between passive and active, digital and analog filters. When the switched filter contains a passive filtering module, different types of passive EMI filters for different lines are adjusted by toggling the passive filter device cut-in switch 24. Students can learn the difference in filtering capabilities between different types of passive EMI filters.

[0147] Based on this, the present invention designs a teaching experimental device for measuring and filtering the electromagnetic interference conducted by power supply equipment. It has a quantitative design method for the layout of cables and a hybrid EMI filter design that takes into account the source and load impedance characteristics of the filtered object. It can demonstrate the electromagnetic interference emission mechanism of the power supply equipment and the insertion loss and other performance of the EMI filter, so as to meet the use of practical teaching courses of electrical majors in colleges and universities.

Claims

1. The power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device is characterized by: The conductive EMI experimental platform (4) is provided with a conductive EMI experimental module (1), a conductive EMI measurement module (2), and a computer (3) which are connected in sequence.

2. The power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device according to claim 1 is characterized in that: The conducted EMI experimental module (1) comprises a measurement block (34), a filter block (35) and a power supply load block (36) which are connected in sequence.

3. The power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device according to claim 2 is characterized by: The measuring block (34) comprises two impedance stabilizers (5), the L and N AC power lines are respectively connected to the two impedance stabilizers (5), the PE line is first connected to the PE on-off module (15) and then connected to the two impedance stabilizers (5), one end of the two impedance stabilizers (5) is connected to one end of the filter mode switching module (10), and the other end of the filter mode switching module (10) is an OUT output end.

4. The power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device according to claim 3 is characterized by: The filter plate (35) comprises a filter module (6), the input end and the output end of the filter module (6) are respectively connected to a slide slot (13), and three wire clamps (14) are equidistantly arranged on each slide slot (13).

5. The power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device according to claim 4 is characterized in that: The power load block (36) comprises a test object module (7), the + line and the - line of the DC power line in the test object module (7) are connected to the load module (8), the test object module (7) is connected to one end of the controller (9), and the other end of the controller (9) is respectively connected to the duty cycle regulator (18) and the switching frequency regulator (19), and a wire clamp (14) is installed between the test object module (7) and the controller (9) to fix the signal line, and the wire clamp (14) is installed on the slide groove (13).

6. The power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device according to claim 5, characterized in that: The load module (8) comprises n load resistors (11) and n load switching switches (16), and each load resistor (11) is connected in series with a load switching switch (16).

7. The power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device according to claim 6, characterized in that: The filter module (6) comprises L1, N1 and PE1 lines arranged in parallel, a passive filter module (20) is connected in series on the L1, N1 and PE1 lines, an active filter module (21) and a digital active filter module (22) are also connected in parallel on the L1, N1 and PE1 lines, a filter mode switching switch (23) is provided at both ends of the passive filter module (20), and a filter mode switching switch (23) is provided on the connection line between the active filter module (21) and the digital active filter module (22) and the L1, N1 and PE1 lines.

8. The design method of the teaching experimental device for measuring and filtering the conducted electromagnetic interference of power supply equipment according to any one of claims 1 to 7, characterized in that: It includes the design of the distance l1 between a conducted EMI experimental platform (4), an impedance stabilizer (5) and a test object module (7), and the spacing of a line clamp (14).

9. The design method of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device according to claim 8 is characterized by: The design process of the table height h of the conducted EMI experimental platform (4) is as follows: Based on the capacitive coupling mechanism of the power supply equipment, the power supply equipment generates parasitic capacitance C through the switch tube and the metal base plate. k , the height h of the table of the conducted EMI experimental platform (4) and the parasitic capacitance C k The formula is: Where ε0 is the dielectric constant of vacuum; ε r1 is the relative dielectric constant; a SMPS is the length of the power supply equipment; b SMPS is the width of the power supply device; according to the common mode noise loop formed by the power supply device and the impedance stabilizer, the common mode noise loop satisfies the following equation: Among them, U CM is the common mode interference source voltage; I EMI is the common mode interference current; R LISN is the internal resistance of the impedance stabilizer; C LISN is the internal capacitance of the impedance stabilizer; C k is the parasitic capacitance between the switch tube and the metal base plate; f SMPS is the switching frequency of the switch tube; The table height h of the conducted EMI test platform (4) satisfies the following relationship: The distance from the conducted EMI experiment module (1) to the rear metal side plate is x. Based on the capacitive coupling mechanism of the power supply device, a common mode noise loop is constructed. According to formulas (1) to (3), the size of x satisfies: Among them, x0 is the distance between the power supply equipment and the wall; The design process of the distance l1 between the impedance stabilizer (5) and the test object module (7) is as follows: Based on the conduction coupling principle, the common-mode circuits of the L line and the N line share the PE line. When there is interference current in the L line, the interference voltage generated on the L line will affect the N line, resulting in conduction coupling. According to the conduction coupling equivalent circuit of the L line common-mode loop, the following formula (5) is obtained: Among them, k c is the crosstalk of L line to PE line; U CM is the common mode interference source voltage; Z L1 is the load impedance between L line and PE line; Z L2 is the load impedance between the N line and the PE line; Z S1 is the source impedance between L line and PE line; Z S2 is the source impedance between the N line and the PE line; Z C is the PE line impedance; PE line impedance Z C The impedance Z is related to the distance l1 between the impedance stabilizer (5) and the test object module (7). C It is expressed by formula (6): Z C =ρ line l1 (6) Among them, ρ line is the resistivity of the conductor; According to formula (5) and formula (6), the distance l1 between the impedance stabilizer (5) and the test object module (7) is: Among them, k c is the crosstalk of L line to PE line; Z L1 is the load impedance between L line and PE line, Z L2 is the load impedance between the N line and the PE line, Z S2 is the source impedance between the N line and the PE line, ρ line is the resistivity of the wire.

10. The design method of the power supply equipment conducted electromagnetic interference measurement and filtering test teaching experimental device according to claim 9 is characterized in that: The design process of the spacing of the wire clamp (14) is as follows: The input end and the output end of the filter module (6) are respectively connected to a group of slide grooves (13), and three wire clamps (14) are equidistantly arranged in each group of slide grooves (13). At this time, the two groups of slide grooves (13) and the three corresponding wire clamps (14) constitute H1 and H2; wherein H1 is located between the impedance stabilizer (5) and the filter module (6); H2 is located between the filter module (6) and the test object module (7); by moving the wire clamp (14) on the slide groove (13) to adjust the distance d1 between the L line and the N line, the design process of the distance d1 between the L line and the N line is: Based on the electric field coupling theory, when the common mode noise voltage exists, the L line and the N line are close to each other and a coupling capacitor C is generated. LN , and then crosstalk is generated between the L line and the N line. According to the equivalent circuit of the capacitive coupling between the L line and the N line, the following formula (8) is obtained: Among them, k t is the crosstalk of L line to N line; Z L1 is the load impedance between L line and PE line; Z L2 is the load impedance between the N line and the PE line; Z S1 is the source impedance between L line and PE line; Z S2 is the source impedance between the N line and the PE line; C LG is the capacitance of L line to ground; C NG is the capacitance of N line to ground; C LN is the coupling capacitance between the L line and the N line; f SMPS is the switching frequency of the switch tube; According to the principle of capacitance between conductors, the L line and the N line generate coupling capacitance at high frequencies. LN The capacitance C is related to the distance d1 between the two lines. LN It is expressed by formula (9): Where, ε0 is the dielectric constant of air; d1 is the distance between L line and N line; l1 is the distance between the impedance stabilizer and the test object module; r line is the radius of the wire; According to the principle of parallel plate capacitor, the L line and the N line generate a L line to ground capacitance C at high frequency. LG and an N-line to ground capacitor C NG , these two capacitors are related to the height h of the conduction EMI experimental platform. The capacitor C LG and C NG It is expressed by formula (10): Where, l1 is the distance between the impedance stabilizer and the test object module; r line is the radius of the conductor; according to formula (8) to formula (10), the distance d1 between the L line and the N line is: d1=2r line e m (11) in: k t is the crosstalk of L line to N line, ε0 is the relative dielectric constant; Z L1 is the load impedance between L line and PE line, Z S1 is the source impedance between L line and PE line, f SMPS is the switching frequency of the switch tube; in order to balance the common mode interference between the L line and the N line, the distance from the PE line to the L line and the distance from the PE line to the N line are A wire clamp (14) is installed between the test object module (7) and the controller (9) to fix the signal wire. The wire clamp (14) is installed on the slide slot (13) to form H3. The distance d2 between the signal wire of the controller (9) and the power supply wire is adjusted by moving the wire clamp (14) on the slide slot (13). Based on the electric field coupling theory, according to formulas (8) to (12), the distance d2 between the signal wire of the controller and the power supply wire satisfies the following relationship: <h2 style=";text-align:left;direction:ltr">d2 = 2r<h2 style=";text-align:left;direction:ltr"> line <h2 style=";text-align:left;direction:ltr"> e<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> (13) in:

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