EMC in Automotive
1. Importance of EMC in Automotive
Modern vehicles contain numerous electronic systems that control everything from engine performance to safety features such as airbags, anti-lock braking systems (ABS), and advanced driver-assistance systems (ADAS). These systems must operate reliably in the presence of electromagnetic interference, which could originate from various sources inside and outside the vehicle.
2. Sources of EMI in Automotive
•Internal Sources: Electronic Control Units (ECUs), sensors, communication buses (e.g., CAN, LIN), and motors generate EMI within the vehicle. Switching circuits, electric motor brushes, and digital clocks contribute to noise.
•External Sources: Vehicles are exposed to electromagnetic interference from radio stations, cell towers, nearby vehicles, and power lines.
3. Key EMC Issues in Automotive
-Radiated Emissions: Emissions from onboard electronics, such as infotainment systems and power electronics, must be controlled to avoid interference with radio communications or other vehicles.
-Radiated Immunity: Automotive systems need to be immune to external EMI, ensuring that safety-critical systems remain operational under real-world interference.
-Conducted Emissions: Electrical noise generated by powertrain components (especially in electric and hybrid vehicles) needs to be limited to avoid interference with the vehicle’s electrical network or with external systems.
-Conducted Immunity: Vehicle systems must resist EMI that enters through wiring harnesses or the power supply.
4. Testing and Standards Automotive EMC testing follows international standards like:
•ISO 11452: Covers the immunity of vehicle electronics to radiated electromagnetic fields.
•ISO 7637: Focuses on immunity to conducted transients, especially on automotive wiring and power systems.
•CISPR 25: Specifies the limits for radio-frequency emissions and immunity from components and modules in vehicles.
•OEM-Specific Standards: Automakers often have their own EMC requirements for testing.
5. EMC in Electric Vehicles (EVs)Electric vehicles and hybrid electric vehicles (HEVs) pose new challenges for EMC because:
•High-Power Systems: EVs and HEVs use high-voltage powertrain systems that generate substantial EMI, particularly from inverters and switching components.
•Battery Management Systems: These systems must be robust against EMI to prevent malfunction or data corruption.
•Wireless Charging: Wireless charging introduces additional EMI challenges due to the magnetic fields involved, which could interfere with other vehicle electronics if not well-managed.
6. EMC Design Considerations in Automotive
•Shielding and Grounding: Shielded cables and enclosures protect sensitive systems from EMI, while proper grounding helps dissipate unwanted electromagnetic energy.
•PCB Design: Proper PCB layout, minimizing trace length, and using differential signaling reduce the risk of EMI in automotive electronics.
•Component Placement: Noise-generating components are kept away from sensitive systems to minimize EMI coupling.
•Filtering: Power line and signal filtering reduce conducted noise between various systems in the vehicle.