`Passive Cancellation of Common-Mode
`Electromagnetic Interference in Switching Power
`Converters
`
`Daniel Cochrane
`
`Thesis Submitted to the Faculty of the Virginia Polytechnic
`Institute and State University in Partial Fulfillment of the
`Requirements for the Degree of
`
`Master of Science
`in
`Electrical Engineering
`
`Dan Y. Chen
`Dusan Boroyevic
`Jason S. Lai
`
`August 10, 2001
`Blacksburg, VA
`
`Keywords: EMI, Noise Cancellation, Noise Reduction Switching
`Power Supplies
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`Page 1 of 105
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`Volkswagen Exhibit 1029
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`Abstract
`
`It is well known that common-mode (CM) conducted electromagnetic interference (EMI) is
`caused by the common-mode current flowing through the parasitic capacitance of transistors,
`diodes, and transformers to ground in the power circuit. Because of the potential for interference
`with other systems as well as governmental regulations, it is necessary to attenuate this noise.
`Ordinarily this must be accomplished by using a magnetic choke on the input power lines, which
`can result in large penalties to the overall size, weight, and cost of the completed system.
`
`In order to lessen the requirement for this magnetic choke, there has been in recent years a
`desire to introduce noise cancellation techniques to the area of EMI. This text introduces a
`method of canceling the common-mode EMI by using a compensating transformer winding and a
`capacitor. Compared with active cancellation techniques, it is much simpler and requires no
`additional transistors and gate-drive circuitry since it merely adds a small copper winding and a
`small capacitor. By using this technique the size of the EMI filter can be reduced, especially for
`applications requiring high currents.
`
`In this thesis a survey of CM noise reduction techniques is presented, encompassing
`conventional and active cancellation techniques. The new method for passive noise cancellation
`is presented, which is then applied to families of isolated DC/DC converters, non-isolated DC/DC
`converters, and DC/AC inverters and motor drives. The method, results, and ramifications of this
`technique are presented in order of appearance.
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`Acknowledgement
`
` I would like to express my gratitude to my advisor Dr. Dan Y. Chen, for his unfailing help and
`support during my time at Virginia Tech. It would have been quite impossible for me to complete
`this thesis without his extensive knowledge and advice.
`
` I would also like to thank my committee members, Dr. Dusan Boroyevic and Dr. Jason Lai, for
`their support of my research. In addition, I would like to thank the faculty, staff and students at
`the Center for Power Electronics at Virginia Tech for their friendship and technical help, with
`particular thanks to the following: Carl Tinsley, Jeremy Ferrel, Robert Gannett, Erik Hertz, Cory
`Papenfuss, and Troy Nergard.
`
` Finally, I must thank my parents, Alan and Vivian Cochrane, for their love and support in my
`various endeavors throughout the years.
`
` This work was partially funded by the Office of Naval Research under contract number
`N000140010610, and made use of ERC Shared Facilities supported by the National Science
`Foundation under Award Number EEC-9731677
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`Table of Contents
`
`Chapter 1. A Brief Overview of EMI .......................................................................................... 1
`1.1. What is EMI? .................................................................................................................... 1
`1.1.1. The Basics.................................................................................................................. 1
`1.1.2. Standards.................................................................................................................... 3
`1.1.3. Testing........................................................................................................................ 6
`1.2. Sources and Traps ............................................................................................................. 9
`1.2.1. Active Components.................................................................................................... 9
`1.2.2. Passive Components ................................................................................................ 10
`1.2.3. Layout ...................................................................................................................... 11
`Chapter 2. Existing EMI Reduction Techniques ....................................................................... 13
`2.1. Conventional Methods .................................................................................................... 13
`2.2. Active Cancellation......................................................................................................... 14
`2.3. Passive Cancellation........................................................................................................ 19
`2.4. Remarks........................................................................................................................... 20
`Chapter 3. Proposed Passive Cancellation in Isolated DC/DC Converters ............................... 21
`3.1.
`Introduction to the Proposed Technique ......................................................................... 21
`3.2. Buck Derived Converters................................................................................................ 23
`3.2.1. Half-Bridge DC/DC ................................................................................................. 23
`3.2.1.1. General Description.......................................................................................... 23
`3.2.1.2. Construction of Prototype................................................................................. 24
`3.2.1.3.
`Experimental Test Results ................................................................................ 25
`3.2.2. Single-Switch Forward Converter ........................................................................... 33
`3.2.2.1. General Description.......................................................................................... 33
`3.2.2.2.
`Experimental Test Results ................................................................................ 33
`3.3. Buck-Boost Derived Converters ..................................................................................... 36
`3.3.1. Flyback Converter.................................................................................................... 36
`3.4. Remarks........................................................................................................................... 41
`Chapter 4. Proposed Passive Cancellation in Non-Isolated DC/DC Converters....................... 42
`4.1. Buck Converters.............................................................................................................. 42
`4.1.1. Description of Technique and Model Results.......................................................... 42
`4.1.2. Limitations of the Technique ................................................................................... 49
`4.2. Boost Converters............................................................................................................. 50
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`4.3. Buck-Boost Converters ................................................................................................... 52
`4.4. Remarks........................................................................................................................... 58
`Chapter 5. Proposed Passive Cancellation in DC/AC Inverters and Motor Drives................... 59
`5.1. Method 1: Modifying the Output Filter........................................................................... 59
`5.1.1. Description of Technique and Model Results.......................................................... 59
`5.1.2. Limitations Due to Load Interaction........................................................................ 62
`5.2. Method 2: The Phase Leg Cancellation Circuit .............................................................. 69
`5.2.1. General Description ................................................................................................. 69
`5.2.2. Analysis Using Saber............................................................................................... 70
`5.2.3. Construction of the Experimental Cancellators ....................................................... 75
`5.2.4. Experimental Test Results ....................................................................................... 81
`5.3. Remarks........................................................................................................................... 88
`Chapter 6. Conclusions and Future Work.................................................................................. 90
`6.1. Summary and Overview.................................................................................................. 90
`6.2. Future Research Topics................................................................................................... 92
`Bibliography .................................................................................................................................. 94
`Vita ................................................................................................................................................ 96
`
`
`List of Figures
`Figure 1: Examples of Conducted and Radiated EMI Propagation................................................. 2
`Figure 2: Flow Chart of Source to Victim Coupling Paths.............................................................. 2
`Figure 3: Comparison of Conducted Emissions Limits for FCC Part 15, Subpart J and
`CISPR, Publication 22............................................................................................................. 5
`Figure 4: MIL-STD-461E Conducted EMI Limits, CE102............................................................. 5
`Figure 5: MIL-STD-461E Conducted Emissions Test Setup .......................................................... 6
`Figure 6: MIL-STD-461E, CE102 Measurement Setup.................................................................. 7
`Figure 7: Typical and MIL-STD-461E LISN .................................................................................. 8
`Figure 8: LISN Impedance Comparison.......................................................................................... 8
`Figure 9: Packaging Parasitics for Active Device ......................................................................... 10
`Figure 10: Transformer with Lumped Reactive Parasitics ............................................................ 11
`Figure 11: Typical EMI Line Filter Topology Incorporating CM and DM Components.............. 14
`Figure 12: Typical Three-Phase Voltage Source Inverter ............................................................. 15
`Figure 13: 3-Phase 4-Leg VSI with Active CM Filter................................................................... 16
`Figure 14: Single-Phase Inverter with Active CM Voltage Cancellation...................................... 17
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`Figure 15: Balanced Buck Converter Topology ............................................................................ 18
`Figure 16: Auxiliary Active Circuit for CM Voltage Cancellation ............................................... 18
`Figure 17: CM Transformer for Damping of Noise Currents........................................................ 20
`Figure 18: Proposed Method of CM Noise Cancellation............................................................... 21
`Figure 19: Half-Bridge Isolated DC/DC Topology Incorporating Passive Cancellation .............. 23
`Figure 20: Half-Bridge Prototype.................................................................................................. 24
`Figure 21: Winding Structure of Half-Bridge Transformer with Compensation Winding............ 25
`Figure 22: Test-Setup inside EMI Chamber for Half-Bridge Experiment..................................... 25
`Figure 23: Test-Setup outside EMI Chamber for Half-Bridge Experiment................................... 26
`Figure 24: Half-Bridge CM Voltage Waveforms .......................................................................... 27
`Figure 25: Half-Bridge CM Baseline and 56pF Compensation (Poor Transformer)..................... 28
`Figure 26: Half-Bridge CM Comparison with 750pF of Added CPARA (Poor Transformer) ......... 29
`Figure 27: Half Bridge Results with CPARA = 56pF (Good Transformer)...................................... 29
`Figure 28: Half Bridge Results with CPARA = 112pF (Good Transformer).................................... 30
`Figure 29: Final Half-Bridge CM Results ..................................................................................... 31
`Figure 30: Final Half-Bridge DM Results ..................................................................................... 32
`Figure 31: Off-Line Forward Converter Incorporating Passive CM Cancellation ........................ 33
`Figure 32: Forward Converter FET and Diode Waveforms .......................................................... 34
`Figure 33: Experimental CM Noise Comparison for Forward Converter ..................................... 35
`Figure 34: Isolated Flyback Topology Incorporating Passive CM Cancellation........................... 36
`Figure 35: Saber Model for Noise Compensated Flyback Converter............................................ 38
`Figure 36: Simulated Parasitic and Compensating Voltages for Flyback Converter..................... 39
`Figure 37: Simulated Parasitic and Compensating Currents in Flyback Converter....................... 39
`Figure 38: Simulated CM Spectrum Comparison for Flyback Converter ..................................... 40
`Figure 39: Simulated DM Spectrum Comparison for Flyback Converter (Unchanged) ............... 40
`Figure 40: Buck Converter Incorporating Passive CM Noise Cancellation .................................. 42
`Figure 41: Saber Model for CM Noise Compensated Buck Converter ......................................... 44
`Figure 42: Buck Converter CM Voltages ...................................................................................... 45
`Figure 43: Buck Converter CM Currents....................................................................................... 45
`Figure 44: Buck Converter CM Noise Spectrum Comparison ...................................................... 46
`Figure 45: Buck Converter DM Noise Spectrum Comparison...................................................... 46
`Figure 46: Buck Converter CM Voltages, High Input Capacitor ESL .......................................... 47
`Figure 47: Buck Converter CM Currents, High Input Capacitor ESL........................................... 47
`Figure 48: Buck Converter CM Voltages, High Leakage Inductance ........................................... 48
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`Figure 49: Buck Converter CM Currents, High Leakage Inductance............................................ 48
`Figure 50: Boost Converter Incorporating Passive CM Noise Cancellation ................................. 50
`Figure 51: Boost Converter Parasitic and Compensating Voltage Waveforms............................. 51
`Figure 52: Boost Converter CM Noise Spectrum Comparison ..................................................... 52
`Figure 53: Buck-Boost Converter Incorporating Passive CM Noise Cancellation........................ 52
`Figure 54: Saber Model for CM Noise Compensated Buck-Boost Converter............................... 53
`Figure 55: Buck-Boost Converter CM Voltages ........................................................................... 54
`Figure 56: Buck-Boost Converter CM Currents............................................................................ 54
`Figure 57: Buck-Boost Converter CM Noise Spectrum Comparison............................................ 55
`Figure 58: Buck-Boost Converter DM Noise Spectrum Comparison ........................................... 55
`Figure 59: Buck-Boost Converter CM Voltages, High Input Capacitor ESL ............................... 56
`Figure 60: Buck-Boost Converter CM Currents, High Input Capacitor ESL................................ 56
`Figure 61: Buck-Boost Converter CM Voltages, High Leakage Inductance................................. 57
`Figure 62: Buck-Boost Converter CM Currents, High Leakage Inductance................................. 57
`Figure 63: Inverter CM Reduction by Modified Output Filter...................................................... 59
`Figure 64: Saber Model for Half-Bridge PWM Inverter Output Filter Test.................................. 60
`Figure 65: Half-Bridge Inverter CM Noise Spectrum ................................................................... 61
`Figure 66: Half-Bridge Inverter DM Noise Spectrum................................................................... 62
`Figure 67: Equivalent Circuit of Half-Bridge Inverter Filter and Load......................................... 63
`Figure 68: Bridge Transfer Function for Lo = 1µH--10mH........................................................... 64
`Figure 69: Bridge Transfer Function for Ro = 0.01—100k............................................................ 64
`Figure 70: Bridge Transfer Function for Co = 1nF—10µF............................................................ 65
`Figure 71: Half-Bridge Inverter CM Noise Spectrum with Bridge Transfer Function.................. 66
`Figure 72: Half-Bridge Inverter CM Comparison with Increases CCOMP....................................... 67
`Figure 73: Half-Bridge Inverter CM Voltages, Leakage = 0.1%................................................... 68
`Figure 74: Half-Bridge Inverter CM Currents, Leakage = 10%.................................................... 68
`Figure 75: Generic Phase-Leg Cancellation Circuit ...................................................................... 69
`Figure 76: 3-Φ Inverter Saber Model with CM Cancellators ........................................................ 71
`Figure 77: Inverter Parasitic and Compensating Waveforms with Non-Ideal Cancellator,
`High RCOIL.............................................................................................................................. 71
`Figure 78: 3-Φ Inverter CM Noise Spectrum Comparison with Cancellator ................................ 72
`Figure 79: 3-Φ Inverter DM Noise Spectrum Comparison with Cancellator................................ 72
`Figure 80: 3-Φ Inverter CM Noise Spectrum Comparison with Cancellator, Small CBLOCK......... 73
`Figure 81: 3-Φ Inverter CM Noise Spectrum Comparison with Cancellator, Large RCOIL ........... 73
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`Figure 82: Inverter Parasitic and Compensating Waveforms with Cancellator, Large
`RCOIL....................................................................................................................................... 74
`Figure 83: Cancellator Sees 60 Hz Inverter Output Frequency..................................................... 74
`Figure 84: Phase-Leg Cancellation Circuit (Metglas) ................................................................... 77
`Figure 85: Phase-Leg Cancellation Circuit (Air / Metglas Core Comparison).............................. 77
`Figure 86: Primary Side Impedance of Metglas Cancellator......................................................... 78
`Figure 87: Primary Side Impedance of Air Core Cancellator........................................................ 78
`Figure 88: Pulse Response of Metglas Core Phase-Leg Cancellator at 10 kHz ............................ 79
`Figure 89: Pulse Response of Air Core Phase-Leg Cancellator at 10 kHz.................................... 79
`Figure 90: Installation of Phase-Leg Cancellation Circuit ............................................................ 80
`Figure 91: Inverter Test Setup (Right Side)................................................................................... 81
`Figure 92: Inverter Test Setup Close-up........................................................................................ 81
`Figure 93: Inverter Test Setup (Left Side)..................................................................................... 82
`Figure 94: Inverter Power Waveforms .......................................................................................... 83
`Figure 95: Inverter CM Noise Spectrum (Metglas) is Unchanged ................................................ 84
`Figure 96: Inverter DM Noise Spectrum (Metglas) is Unchanged................................................ 84
`Figure 97: Simulated Metglas Cancellator, High RCOIL................................................................. 85
`Figure 98: Simulated Metglas Cancellator, High RCOIL................................................................. 86
`Figure 99: Simulated Metglas CM Noise Spectrum Comparisons................................................ 86
`Figure 100: Inverter CM Results with AMCC-40 Core and #27 Wire.......................................... 87
`Figure 101: Inverter CM Noise Spectrum (Air Core).................................................................... 88
`Figure 102: Inverter DM Noise Spectrum (Air Core) is Unchanged............................................. 88
`Figure 103: Noise Spectrum Attenuation Example ....................................................................... 91
`Figure 104: CM Filter for Example ............................................................................................... 91
`List of Tables
`Table 1: List of Common EMI Regulations .................................................................................... 3
`Table 2: Design Details of Half-Bridge Prototype ........................................................................ 24
`Table 3: Test Settings for HP4195A in Half-Bridge Experiments ................................................ 26
`Table 4: Comparison for Selected Switching Harmonics (Heat Sink Ungrounded) ..................... 30
`Table 5: Final Half-Bridge Switching Harmonic Comparison ...................................................... 32
`Table 6: Design Details of Forward Converter Prototype ............................................................. 34
`Table 7: Test Settings for HP4195A in Forward Converter Experiments ..................................... 35
`Table 8: Metglas Transformer Design Details............................................................................... 76
`Table 9: AMCC-25 Core Information ........................................................................................... 76
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`Table 10: Transformer Parameter Comparison.............................................................................. 80
`Table 11: Test Settings for HP4195A in Inverter Experiments..................................................... 82
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`Chapter 1. A Brief Overview of EMI
`
`Before we look at the main topic of this thesis text, it is necessary to present some basic
`background information. This chapter briefly summarizes some of the most important topics of
`the field of EMI as they relate to this particular subject. Starting with the fundamental definitions,
`we will then look at some of the regulations pertaining to this subject before looking at the causes
`of noise.
`
`1.1. What is EMI?
`
`1.1.1. The Basics
`
`What is EMI? Simply put, EMI, or electromagnetic interference, is undesirable noise that
`interferes with the normal operation of electronics. Michel Mardiguian puts it the following:
`
`“Generally, electromagnetic interference occurs when an electrical disturbance from either a
`natural phenomenon (e.g., electrostatic discharge [ESD], lightning, and so on) or an electrical or
`electronic equipment causes an undesired response in another equipment.”1
`
`Specifically, we can categorize EMI into four different groups:
`
`1. Conducted emissions
`
`2. Radiated emissions
`
`3. Conducted susceptibility
`
`4. Radiated susceptibility
`
`The first two groups deal with the undesirable emanations from a particular piece of equipment,
`and the second two groups deal with a piece of equipment’s ability to reject interference from
`external sources of noise. In this thesis I will be focusing on the first type of EMI: conducted
`emissions.
`
`In practice this interference can have various degrees of manifestation ranging from nuisance,
`such as interference with a portable radio when walking under a power line, to catastrophic, such
`
`1 Mardiguian, pg 1
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`as an electronic communications device interfering with a aircraft navigation equipment’. Ott
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`gives a diagram shown in Figure 1 that illustrates some of the myriad ways that EMI can be
`
`propagated.
`
`RADIO
`& TV
`BROAOCAST
`
`ELECTRIC MOTORS AC POWER CIRCUIT
`—»
`
`Figure 1: Examples of Conducted and Radiated EMI Propagation®
`
`Culprit Noise:
`E-Field
`H-Field
`Voltage
`Current
`
`Figure 2: Flow Chart of Source to Victim Coupling Paths‘
`
`> CAA News,referenced in bibliography, specifies several instancesof cell phones triggering various
`
`system malfunctions in commercial aircraft.
`3 Ott. pg. 3
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` Figure 2 is a simple flow chart showing how the noise sources are coupled into a noise victim;
`this can be the system itself or some other nearby susceptible equipment. The particular method
`of coupling that this thesis will focus on eliminating is the highlighted box “Common Ground
`Impedance Coupling”.
`
` As electronic equipment has increased in popularity we have been seeing a great deal of interest
`in incorporating switch-mode power converters to reduce the size, weight, and cost of said
`equipment. In order to increase the performance and/or the efficiency of these power converters
`the switching frequency has been increasing with concomitant increases in the levels of EMI.
`Techniques of reducing this EMI by cheap and simple means should therefore be of great interest
`to persons involved in the design of switch-mode power conversion equipment.
`
`1.1.2. Standards
`
`Because of the difference in motivation between protecting the designer’s product against
`susceptibility to other products emissions and protecting other products from emissions from the
`designer’s product, various government bodies have instituted standards which set specific limits
`on the quantities of radiated and conducted noise emissions in order for a product to be sold
`within that country. In the United States these regulatory bodies are the Federal Communications
`Commission (FCC) and the Department of Defense (DOD). In Europe all standards are set by the
`European Economic Consortium (EEC). There is also an international body called the
`International Special Committee on Radio Interference (CISPR), a committee of the International
`Electrontechnical Commission (IEC), which has no regulatory authority but which sets standards
`that can then be adopted by individual nations in order to facilitate international trade. Table 1
`summarizes these various standards.
`Table 1: List of Common EMI Regulations
`Description
`FCC General standard for digital electronics
`EU standard for industrial, scientific, and medical equipment
`EU standard for broadcast receivers
`EU standard for motor and thermal appliances, and electrical tools
`EU standard for electrical lighting
`EU standard for information technology (IT) equipment
`CISPR standards for digital electronics
`DOD standards for electrical equipment
`
`
`Standard
`FCC Part 15, Subpart J
`EN55011
`EN55013
`EN55014
`EN55015
`EN55022
`CISPR Publication 22
`MIL-STD-461E
`
`
`4 Mardiguian, pg. 16
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` While all of the aforementioned standards include both conducted and radiated specifications as
`well as regulations concerning electromagnetic compatibility, only the conducted noise
`interference specifications will be discussed in this thesis in the interest of reducing extraneous
`noise. Figure 3 and Figure 4 (The EN standards follow CISPR specifications) compare the limits
`of each of these standards. The non-military specifications differentiate between types of
`electronic equipment; a Class A device is intended for use in commercial or industrial
`environments while a Class B device is intended for consumer applications5. Typically no
`military equipment is intended for use in consumer applications, so the military specification
`differentiates between equipment based on input voltage and adds special rules if the equipment
`is to be used in an electromagnetically sensitive environment such as that in a submarine or
`spacecraft.
`
` The most important difference between all of these specifications is the frequency band that
`they cover. The CISPR and the EU regulations specify a bandwidth of 150 kHz-30 MHz, while
`the FCC is more lax in calling for a starting frequency of 450 kHz. MIL-STD-461E is much
`stricter on the low frequency side (10 kHz), although the high side of the specification only goes
`to 10 MHz. What this translates into is that the corner frequency of the input EMI filter will have
`to be lowered for the stricter standards, which can mean a considerable increase in the size and
`cost of the compliant system. Naturally this also increases the motivation for eliminating the EMI
`by techniques other than filtering.
`
`
`5 Ott, pg 8
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`
` Voltage(dBuV)
`
`Figure 3: Comparison of Conducted Emissions Limits for FCC Part 15, Subpart J and CISPR, Publication 22°
`
`Frequency (MHz)
`
`
`
`
`Nominal EUT Source
`Voltage (AC & DC)
`28V
`115V
`220V
`270V
`
`
`
`Voltage(dBuV)
`
`Frequency (MHz)
`
`Figure 4: MIL-STD-461E Conducted EMI Limits, CE102’
`
`° Tbid., pg. 15
`7 MIL-STD-461E,pg. 38
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`1.1.3. Testing
`
`Each regulatory body has a specific standard of performing EMI tests. Figure 5 shows the
`conducted emission test setup for MIL-STD-461E by means of example. The equipment under
`test (EUT) is placed on a copper ground plane that is electrically isolated from the surrounding
`area. Power leads to the EUT have a Line Impedance Stabilization Network (LISN) placed in
`series to provide a common power line impedance over the frequency of interest. The LISN also
`serves as the measurement point for the conducted mode testing, as shown in the MIL-STD-461E,
`CE102 measurement setup in Figure 6.
`
`
`
`Figure 5: MIL-STD-461E Conducted Emissions Test Setup8
`
`
`
`
`8 MIL-STD-461E, pg. 19
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`50 Q Terminator
`
`Power
`
`Power Cable
`
`Receiver
`
`J Lead/ Measurement
`
`Data
`
`Recording
`
`Device
`
`Figure 6: MIL-STD-461E, CE102 Measurement Setup?
`
`Asstated before, the purpose of the LISN is to provide a common 50 Q line impedance for
`
`comparing test results. However, this 50 Q impedanceis only specified of the frequencies to be
`
`tested for noise. This means that for practical purposes, different LISNs mustbe usedfor different
`
`regulations testing. Figure 7 give the schematics of the LISNs used for FCC and MIL-STD-461E
`
`testing. Figure 8 compares their impedances.It is obvious that the typical LISN will give good
`
`results for the FCC test that starts at 450 kHz, but the system designer should be aware of the
`
`limitations of the -461E LISN. The 10 kHz—500 kHz portion of the CE102 test will have a much
`
`lower impedance than the higher frequencies. This can possibly create issues with an input filter
`
`(See Section 2.1) designed for the larger line impedance. Of course, these problems will be
`
`magnified if the wrong LISN is used, since the typical LISN dropsto slightly less than 1 Q at low
`
`frequency versus 5 Q for the -461E LISN.
`
`° Tbid., pg. 40
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`56 µH
`
`Line
`22.5 µF
`
`1 Ω
`
`Line
`22.5 µF
`
`1 kΩ
`
`Line
`2 µF
`
`5 Ω
`
`50Ω
`Terminal
`
`50 µH
`
`Line
`0.25 µF
`
`1 kΩ
`
`50Ω
`Terminal
`
`
`
`
`
`8
`
`Figure 7: Typical and MIL-STD-461E LISN10
`
`MIL-STD-461E
`
`Typical
`
`10000
`
`100000
`Frequency (Hz)
`
`1000000
`
`10000000
`
`Figure 8: LISN Impedance Comparison
`
`100
`
`10
`
`1
`
`Impedance (Ω)
`
`0.1
`1000
`
`
`10 Ozenbaugh, pg. 23
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`1.2.
`
`Sources and Traps
`
`1.2.1.