Automotive EMC Introduction And Overview PDF

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Automotive EMCIntroduction and OverviewMark SteffkaEmail: [email protected] of Michigan – DearbornElectrical and Computer EngineeringDepartmentAutomotive EMC Introduction andOverview1

Automotive Systems “Past andPresent” Today’s vehicles contain three centuries oftechnology 19th century internal combustionengines combined with 20th century electricalsystems and 21st century electronics .Automotive EMC.fromSpark to Satellite Automotive EMC Introduction andOverview2

Automotive Systems and EMC The inclusion of new technologies in automotivesystems has resulted in new challenges across thespectrum. and can result in EMC issues from LF to SHF!Automotive EMC Introduction andOverview3

Why is EMC Important to theAutomotive Industry? Today’s electronic systems (including vehicles)contain many more active electronic componentsthan in the past. Those components and assemblies may emit RFnoise or be exposed to external sources of energy- resulting in unanticipated changes in systemoperation.Automotive EMC Introduction andOverview4

The EMC “Model” (as applied toAutomotive Systems)SourcePathPathReceiver The “Source” – near / far field high magneticfield or electric field? The “Path” – radiated or conducted? The “Receiver” – intentional or unintentional?Automotive EMC Introduction andOverview5

Electromagnetic Environmentfor Automotive Systems May be “off board” and “on board” sources. Studies have shown almost “DC to daylight”sources and high field strength levels – bothelectric and magnetic. Typical on board fields of 10 – 100 V/m. Some off board fields are 100’s of V/m !Automotive EMC Introduction andOverview6

Examples of “Off Board” RF New wireless technologies demand more spectrumand more energy Many rural areas are now populated Vehicle must operate in this new environmentAutomotive EMC Introduction andOverview7

“On Board” Vehicle Sources Automobiles canhave on boardsources of significantemissions. High RF levels withcommon equipmentsuch as mobile radiotransmitters.Automotive EMC Introduction andOverview8

Automotive Industry EMCMethodology Vehicle Original Equipment Manufacturer(OEM) practice is to address EMC in thecomponent and system design phase. The resolution of EMC issues mustcomprehend a high volume, complexmanufacturing process AND do not affectprogram timing. Goal is to balance EMC requirements withmarket-based vehicle usage.Automotive EMC Introduction andOverview9

“Customer Focused” AutomotiveEMC Benefit Recognition of twoway radio usage. Important tounderstand installationin vehicles tominimize EMC issues.Automotive EMC Introduction andOverview10

Development of OEM “MobileRadio Installation Guidelines” Shows “EMCfriendly” methods toinstall two way radiosand antenna systems. Based oncommerciallyavailable radios andtransmitters.Automotive EMC Introduction andOverview11

Automotive EMC Requirements “Good” News: Most automotive systems areexempt from FCC Part 15 (see 15.103). “Bad” News: OEM requirements typically 10 to40 dB more stringent than Part 15. “Ugly” News: Most OEM requirements are basedupon international standards such as CISPR, ISO,SAE (which many international legislatedrequirements are also based on).Automotive EMC Introduction andOverview12

Automotive EMC Case Studies Emissions: Microprocessor clock harmonic wason two way radio frequency – rendering radiocommunication impossible. Immunity (the Automotive characterization ofsusceptibility): An engine and transmissionseemed defective due to control systemmalfunctions – cause was a change from ametal to a non-conductive component package.Automotive EMC Introduction andOverview13

Automotive System RF Emissions Vehicle systems can be responsible for onboardnoise generation as a byproduct of vehicle operation. In the automotive industry, this noise has beenclassified into two categories:– Broadband (typically due to electrical arcing)» Referred to as “Arc and Spark” noise.– Narrowband (typically due to active electronics)» All other noise NOT due to “Arc and Spark”.Automotive EMC Introduction andOverview14

Representation Of NoiseBandwidth Broadband noise is greater than the “width” of receiver ofthe energy. Narrowband noise is less than the “width” of the receiver. Impact AM – Noise – FM loss of sensitivity.Automotive EMC Introduction andOverview15

Typical Sources Of BroadbandNoise Sources include ignition components and similar pulsetype systems. Electric motors (both the traditional and the new“brushless”).Automotive EMC Introduction andOverview16

EMC / RFI Issues in PowerElectronics Important to understand the impact of the“slew rate” of high power devices. Many are designed for low powerdissipation during operation resulting in:– Operation at an order of magnitude faster thanresponse of electromechanical devices– Causing radiated/conducted emission issues.Automotive EMC Introduction andOverview17

Why Ignition Noise Is“Broadband” Representative ignitionsystems used today - allutilize high-voltagedischarge. Source of noise is sparkdischarge across gap inplug and/or distributor.Automotive EMC Introduction andOverview18

Consequences Of BroadbandNoise Sources BAD –Due to functions that are required forbasic vehicle operation (such as ignition orinductive devices). BAD – Can have both conducted AND radiatedcoupling path. GOOD – Energy spread out – may have minimaleffect on potential receivers (intentional andunintentional).Automotive EMC Introduction andOverview19

Representation of NarrowbandEmissions Sources are active electronics. Result is a spectrum of a “comb-like” appearance. Spectrum stays approximately constant over time.Automotive EMC Introduction andOverview20

Consequences Of NarrowbandNoise Sources BAD -May be many sources on a vehicle due toproliferation of active devices. BAD - Receivers can appear to function “almostnormal”. GOOD - Can be addressed in component designprocess (will be discussed by Todd Hubing).Automotive EMC Introduction andOverview21

Immunity Issues Must BeAddressed - Why?“Good Old Days”Today's SystemsComplex engine/vehicle control systems require ahigh degree of robustness to insure proper operationAutomotive EMC Introduction andOverview22

Vehicle Level Immunity ToExternal Fields The goal: to understand the compatibility of theelectronic systems with the environmentOther Signals orServicesOperational FreqAutomotive EMC Introduction andOverviewOther Signals orServices23

Today’s Systems Can HaveImmunity Issues Characteristics of today’s systems are:– Electronic modules that radiate energy may alsobe efficient unintentional receivers of energy.– Therefore, RF sources may affect the operation ofactive devices .with the followingimplications Automotive EMC Introduction andOverview24

Immunity Issues Can ExistDue To The Following Most of today’s vehicle rely on active devices,microprocessors, and vehicle communicationnetworks for:– Control of vehicle functions.– Entertainment systems.– Legislated requirements (such as tire pressure monitoring).Automotive EMC Introduction andOverview25

Immunity: Industry Practices How to ensure product immunity?- Measures should be implemented to “design in”appropriate immunity characteristics.- System and component testing can be conducted bysimulating “external” sources to ensure immunitycharacteristics.Automotive EMC Introduction andOverview26

Bulk Current Injection (BCI)Test Method Injection of RF or pulseenergy on wiring harness. Typical BCI testing is to 400MHz. General rule: 1.5 mA of RFcurrent induced on a cable isequivalent to ½ wavelengthcable in a field strength of 1V/M.Automotive EMC Introduction andOverview27

EMC Circuit Design forImmunity Add series inductance to sensitive I/O. Add parallel capacitance to shunt RF away. Buffer or isolate circuits (opto-isolator,transformer). Keep circuit gain-bandwidth to minimumrequired. Application of localized shielding ondevices.Automotive EMC Introduction andOverview28

Wire Routing Impact On EMC Even the process of wire routing is canbe an important contributor to EMC!– Need to comprehend sources and receiversin systems.– Wire routing affects EMC “Path”.– Critical to recognize that due to parasiticinductance and/or capacitance effects exist.Automotive EMC Introduction andOverview29

Why Wiring Is Contributor ToConducted EMC Issues Early vehicle systems had few electrical components to beconnected - when many wiring practices were developed. Today’s systems have increased wiring demands andsensitive electronic devices. Must be addressed - wiring will still be used for theforeseeable future.Automotive EMC Introduction andOverview30

Automotive EMC Introduction andOverview31

Why Wiring is Important toAutomotive EMC Early systems (and vehicles) had fewcomponents to be connected -Recent systemshave increased wiring complexity. Many automotive engineers consider it “just apiece of wire” and the chassis is “GROUND”! Wiring will still be used for many systems in thefuture. Need to understand relevant physical parameters.Automotive EMC Introduction andOverview32

Role Of Wiring In ConductedEMC Issues Energy may escape or be brought into/from the modules byconduction with wiring harness. Wiring can act as a coupling mechanism.Automotive EMC Introduction andOverview33

Automotive Wiring InductiveCoupling Coupling from the wiringof system 1 to the wiringof system 2 can occur. May be due to “commonground” with manyautomotive circuits. Noise is induced in system2 by “dI/dt” of system 1:– Occurs during period whendI/dt NOT equal to zero– Is the source of inductivelycoupled transientsAutomotive EMC Introduction andOverview34

Automotive Wiring CapacitiveCoupling Capacitive coupling fromsystem 1 to system 2. Due to close proximity ofmany wires in a harnessbundle. Noise is induced in system2 by “dV/dt” of system 1:– Occurs during period whendV/dt NOT equal to zero– Is the source of capacitivecoupled transientsAutomotive EMC Introduction andOverview35

Auto Industry “Best Practices”For Wiring To Minimize EMC Recommendation Route wiring awayfrom ignition system,spark plug wires, andalternator wiring. Rationale High energy noise maycouple inductively orcapacitively into wiring Don’t bundle antenna,speaker, or powerwiring with vehiclewiring Low-level signals canbe affected by highpower circuits.Automotive EMC Introduction andOverview36

Conducted Transients andAutomotive Systems Can result in voltages about 5 –10 timesthat of vehicle system (e.g. 13.8 volts –150 volts transient generation). Can be results of the many inductive loadsused in automotive systems.Automotive EMC Introduction andOverview37

Protection is Required toMinimize Effect of Transients Circuit provisions for over voltage, loaddump, and reverse battery should be made. Transient protection should be on all I/Oand lines going to vehicle power. Realize that all vehicle devices may nothave extensive transient suppression neededby sensitive I/O.Automotive EMC Introduction andOverview38

Automotive EMC ElectrostaticDischarge Testing is used to identify sensitivities. Simulates natural and human-body induced highvoltage ( 4 - 25 kV) discharges. Can cause immediate failure or induce latentdefect (such as in manufacturing process orcustomer use).Automotive EMC Introduction andOverview39

Things to Consider BeforeVehicle Level Testing Begins Meet component requirements. Wiring representative of the actual productionvehicle.Why?– Component level requirements are set at level toprevent any vehicle level interactions fromoccurring.– Many time only the power and signal lines are in theharness – and the return conductor is the vehiclechassis.Automotive EMC Introduction andOverview40

“Quick” Vehicle Level Help For emission diagnostics:– AM/FM radio receivers - AM setting useful to trace BBnoise - FM useful to trace NB noise.– Clamp ferrites on harnesses to eliminate effect ofconducted energy.– Disconnect fuses until noise stops. For immunity – 150 MHz hand held radio canprovide local high fields to identify potentialissues.Automotive EMC Introduction andOverview41

Automotive Component EMCPractices “Back in the day”, the emphasis was on vehiclelevel testing. Now the emphasis is on component levelrequirements and performance due tocomplexity of vehicles, styles, applications, andextensive use of common components. Key to assuring vehicle EMC is the ability toassure component level EMC performance.Automotive EMC Introduction andOverview42

“Cost of EMC” and SolutionsAvailable Goal should be to identify options to address EMCearly in the design stage. Early attentionminimizes cost – and maximizes available options. Use “Pre-Compliance” methods wheneverpossible (will be discussed by Scott Mee).Cost of EMCLowMediumHighVery evelopmentValidationProductionAutomotive EMC Introduction andOverview43

The Component’s Role InAutomotive EMC Incorporate a “Design for EMC” approach. Test by simulating component operation as itwould function in the complete vehicle. If component passes test no action is required. Ifit does not pass - use the test data to determinecorrective action plans.Automotive EMC Introduction andOverview44

Component Testing Methods Most are based upon CISPR, ISO standards(two of which will be discussed in detail byVince Rodriguez). Defines typical component level test set-up. Device under test is configured to functionin a manner similar to vehicle application.Automotive EMC Introduction andOverview45

What is the Supplier’s Role? Obligation to deliver a component that meetscomponent level EMC without requiring vehiclelevel corrective actions. Depends on crucial supplier-to-OEM cooperation(will be discussed by Julian Weber). Important to know the program requirements anddemonstrate compliance by validation.Automotive EMC Introduction andOverview46

Component Level EMC ProgramPlan The process to ensure proper component design,development, and validation prior to vehiclevalidation. The process includes:– Definition of test modes, and input signals similar toapplication usage.– Wiring harness definition.– Load definition.– Methods for monitoring test results.Automotive EMC Introduction andOverview47

Next Steps for Automotive EMC Develop and improve simulation and modeling toinclude both DESIGN aspects and impact ofmanufacturing issues. Goal is to develop physics based models and toevaluate anticipated EMC characteristics usingcircuit simulation and electromagnetic theory (willbe discussed by Daryl Beetner). Key aspect is understanding the coupling paths,sources and receivers.Automotive EMC Introduction andOverview48

Automotive EMC- Overview Automotive EMC is concerned withvehicle electrical/electronic systeminteraction.

Automotive EMC Introduction and Overview. 14. Automotive System RF Emissions •Vehicle systems can be responsible for onboard noise generation as a byproduct of vehicle operation. •In the automotive industry, this noise has been classified into two categories: – Broadband (typically due to electrical arcing) » Referred to as “Arc and Spark” noise. – Narrowband (typically due to ...