ELEC 425 Interference Control in Electronics Lecture 6(a) Conducted Emissions & Susceptibility

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1 Dr. Gregory J. Mazzaro Fall 2017 ELEC 425 Interference Control in Electronics Lecture 6(a) Conducted Emissions & Susceptibility THE CITADEL, THE MILITARY COLLEGE OF SOUTH CAROLINA 171 Moultrie Street, Charleston, SC 29409

Line Impedance Stabilization Network LISN Equipment Under Test AC power network Electro-metrics EM-7823 keeps the Equipment Under Test powered from the AC power

2 Line Impedance Stabilization Network LISN Equipment Under Test AC power network Electro-metrics EM-7823 keeps the Equipment Under Test powered from the AC power net prevents noise from AC power network from affecting the measurement ensures repeatability of measurements (e.g. 50-W impedance looking into AC power network) 2

3 LISN: In-class Demo Line Impedance Stabilization Network powered directly from the AC net Equipment Under Test (EUT) i.e. product to be tested, powered through the LISN spectrum analyzer: voltage reported in dbmv for direct comparison w/ FCC limits center = 150 khz span = 50 khz reference = 10 dbm 3

4 AC power network Equipment Under Test Line Impedance Stabilization Network LISN keeps the Equipment Under Test powered from the AC power net prevents noise from AC power network from affecting the measurement ensures repeatability of measurements (e.g. 50-W impedance looking into AC power network) 4

5 AC power network Equipment Under Test Line Impedance Stabilization Network keeps the Equipment Under Test powered from the AC power net prevents noise from AC power network from affecting the measurement ensures repeatability of measurements (e.g. 50-W impedance looking into AC power network) 5

6 Equipment Under Test Total Current Measured by the LISN Both common- and differential-mode currents can contribute to conducted emissions. 6

7 Total Current Measured by the LISN Both common- and differential-mode currents can contribute to conducted emissions. 7

8 Equipment Under Test Measured Differential Current Under normal operation, the phase and neutral lines carry all current. 8

9 Equipment Under Test Measured Common-Mode Current Under abnormal operation, the green ( safety ) wire carries current. 9

10 Equipment Under Test Total Current Measured by the LISN Both common- and differential-mode currents can contribute to conducted emissions. One way to mitigate these emissions is to place a filter between the EUT and AC power net. 10

11 Dr. Gregory J. Mazzaro Fall 2017 ELEC 425 Interference Control in Electronics Lecture 6(b) Filter Topologies & Power-Supply Filter THE CITADEL, THE MILITARY COLLEGE OF SOUTH CAROLINA 171 Moultrie Street, Charleston, SC 29409

12 Filter Topologies insertion loss, IL a measure of filter effectiveness V L, wo IL 20log10 V Lw, passive filter inserted in cascade, between source & load contains only passive components (e.g. inductors, capacitors) behavior depends partially on source and load impedances 12

13 Example: Lowpass Filter Determine the insertion loss for an inductive lowpass filter (a) vs. frequency, given this topology, and (b) for R S = R L = 50 W and L = 50 mh, at 1 MHz and 10 MHz, in decibels. 13

14 Equipment Under Test Power Supply Filter currents output by the EUT: unprimed currents measured by the LISN: primed The power-supply filter reduces highfrequency currents that would cause the EUT to fail the FCC emissions test. 15

15 Power Supply Filter: Common-Mode + jw(l + M) + + By symmetry, the circuit may be analyzed as: where V C is the measured common-mode voltage. 16

16 Power Supply Filter: Differential + jw(l M) + + By symmetry, the circuit may be analyzed as: where V D is the measured differential-mode voltage. 17

17 Example: Conducted Emissions The parameters of this power-supply filter are: L GW = 1 mh, L = 28 mh, k = 0.98, C CL = C CR = 3.3 nf, C DR = C DL = 0.1 mf The differential-mode and common-mode currents at the input to the filter are 1 ma at 150 khz. Determine (a) the total voltage across the LISN and (b) which component is dominant. V μv C 18

18 Example: Conducted Emissions The parameters of this power-supply filter are: L GW = 1 mh, L = 28 mh, k = 0.98, C CL = C CR = 3.3 nf, C DR = C DL = 0.1 mf The differential-mode and common-mode currents at the input to the filter are 1 ma at 150 khz. Determine (a) the total voltage across the LISN and (b) which component is dominant. V μv D V C V D μv 10 20log dbμv 19

ELEC 425 Interference Control in Electronics Lecture 0 Introduction to the Course & Syllabus

Dr. Gregory J. Mazzaro Fall 2017 ELEC 425 Interference Control in Electronics Lecture 0 Introduction to the Course & Syllabus THE CITADEL, THE MILITARY COLLEGE OF SOUTH CAROLINA 171 Moultrie Street, Charleston,