ELECTROMAGNETIC COMPATIBILITY

Dr. Donald Church

Senior Staff Engineer

International Rectifier Automotive Systems

November 17, 2005

Electromagnetic Compatibility Outline

• Introduction: Terms & Definitions

• EMC in Product Development: Activities & Outputs

• EMC in the Automotive Environment: Challenges

• Example: Electro-Hydraulic Power Steering System

• EMC and the IEEE: Education

• Questions

ELECTROMAGNETIC COMPATIBILITY(EMC)

1. Electromagnetic Emissions

Your System Cannot Interfere With Other Systems or Subsystems in the Vehicle

(e.g., FM Radio).

2. Electromagnetic Susceptibility

Your System Must Continue to Operate Correctly

in the Presence of Interference From Others or

Transient Disturbances.

ELECTROMAGNETIC INTERFERENCE (EMI)

• Conducted Interference

Enters/Exits on Wires for Power or Control

• Radiated Interference

Enters/Exits Through the Air

Emissions Must be Controlled to Protect:

AM & FM Radio Stations

Aircraft Communications & Navigation

Emergency Services Land Communications

EMI MEASUREMENT

Units: dBuV

50dBuV = 316uV

Frequency100kHz – 100MHz

Spectrum Analyzer Screen

~15uV

EMC in Product Development

Typical Development Cycle Outputs

• Product Specification

• System Architecture

• Physical Design

• Product Qualification

Corresponding EMC Outputs

• EMC Requirements Analysis

• EMC Concept Review

• EMC Design Review

• EMC Lessons Learned

EMC in Product Development

Typical EMC Activities During Product Development

Specification:

Architectural/System Design:

Detailed Design:

Prototype/Qualification:

Define the EMC requirements (5 types).Which directives apply? Ensure the standards are understood.What are the implications?

Propose preliminary EMC design concepts.Create the EMC test plan.Propose PCB design strategies.Review Power Stage Concept for EMC.Do an EMC risk analysis.

Implement the strategies and concepts.Do pre-screening tests and simulation.

Do formal certification testing.Re-design & Re-test? Failures here are expensive!

EMC In The Automotive Environment

• Harsh Environment

Power Line Transients

RF Interference

Electrostatic Discharge

Power Line Electric & Magnetic Fields

• High Reliability

1 ppm Goal

“Fail Safe” is Critical

• Extreme Cost Sensitivity

EMC In The Automotive Environment:Susceptibility

Power TransientsInductive Load SwitchingVoltage Sag“Load Dump”

RF ImmunityOn-Board TransmittersRadio StationsAirport Radar SystemsSensors are Most Vulnerable

Electrostatic Discharge (ESD)Up to 15kV

EMC In The Automotive Environment:Emissions

Radiated EmissionsVery Sensitive Receivers

Distance to the Antenna

50dB Lower Than Commercial Limits

Cables Are Unintended Antennas

PCB Traces Also Radiate

Digital Circuits Are The Main Source

EMI Lesson #1: Remember Fourier!

The Energy in a Trapezoidal Waveform is a Function of the PulseWidth and the Rise and Fall Times.

Example: 20kHz waveform with 10ns rise & fall times.

F1 ~ 13kHz F2 ~ 32MHz

ELECTRO-HYDRAULICPOWER STEERING SYSTEM

Hydraulic Pump

Electronic Control Unit• Three-Phase Inverter• Microcontroller & S/W• Sensors• CAN Bus

Three-Phase BrushlessDC Motor

Conducted Emissions Results

Test Conditions; Typical Load, PWM @ 20-30A, 1,000RPM

PWMHarmonics

Power Stage & I/O

Load Z Fast Edges & I/O

Low Frequency; 150kHz - 30MHz High Frequency; 30MHz – 100MHz

EMC AND THE IEEE

• Ancora Imparo – “I Am Still Learning”Michelangelo at Age 87

• IEEE EMC Society

• IEEE Annual EMC Symposium

• NARTE & The IEEE EMC SocietyFostering and promoting Technical Awareness,Education and Achievement in EMC

EMC Summary

• What it is and why it is important

• Designing Early for EMC

• EMC Challenges in the Automotive Environment

• Example of a Certified Automotive Component

• Continuing Education Through NARTE & IEEE

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