An Overview of Automotive EMC Problems

Key Takeaways

• Automotive EMC problems are capable of causing unintended changes in automotive system operations.

• These issues can either be emissions or susceptibility to external EMI sources.

• Automotive EMC problems are the third-largest form of vehicle pollution after exhaust emission and traffic noise.

Automotive EMC problems are the third-largest form of vehicle pollution after exhaust emission and traffic noise

In conventional automobiles, you can find electrical systems and electronic circuits along with the internal combustion engine. Technology advancements in engineering have brought several features into the automotive field but at the expense of electromagnetic compatibility issues.

Automotive EMC problems are the result of either the emissions from electronic assemblies inside a vehicle or the susceptibility of the electronics when exposed to external EMI sources. In both cases, automotive EMC problems are capable of causing unintended changes in the automotive’s system operation. The introduction of new wireless technologies in vehicles and the wide reach of communication connectivity outside vehicles have worsened these issues.

In this article, we will take a closer look at some of the EMC issues vehicles face as well as the sources of that EMC. 

Automotive EMC Problems

Here are a few common automotive EMC problems: 

Vehicle Drive System

In electric vehicles, the vehicle drive system is vulnerable to EMC issues. Most often, the vehicle drive system is subjected to a significant amount of conducted common-mode interference. Improper system grounding and poor board layout designs are potential sources of EMI in vehicle drive systems.

In vehicle drive systems, there are power converters such as DC-AC inverters and DC-DC converters. These converters in the drive create spurious signals that interfere with automotive electronic systems. Also, the PWM signals generated are a source of vehicular electromagnetic interference. 

Vehicle Ignition System

The high-voltage transient electromagnetic pulses in the vehicle ignition system play an important role in inducing internal as well as external EMI. The electromagnetic radiation during the start of ignition is one of the strongest sources of electromagnetic interference affecting vehicle electronics. 

Vehicle Wiper Motor System

Electric DC motors for wipers and windows in conventional automobiles generate reverse transient voltages during motor operation and cause spark discharge between the brushes and commutator segments. The conducted and radiated EMI originating from this discharge develops interference issues in the automotive system. Apart from this, the wiper motor produces conducted interferences between motor windings when they are operating and triggers interference. 

What Causes Automotive EMC Problems?

Automotive EMC problems impact the internal integrated circuitry as well as the electronic systems in the vicinity of a vehicle. In an automobile, the EMC domain can be classified as:

• Radiated immunity
• Radiated emissions
• Conducted immunity
• Conducted emissions 
• Electrostatic discharge (ESD)

The component placement, electronic assemblies, antenna systems, and wiring are all potential causes of automotive EMC problems. The electromagnetic coupling in automotive electronic assemblies is usually via printed circuit board traces or wiring. They act as a path for conducted emissions. The wiring in the vehicle and the internal interconnects can also serve as antennas that convert the electromagnetic field into radiated emissions. 

Apart from hardware, the microprocessor clock frequencies and periodic timing loops present in the software that controls certain automobile operations can cause EMC in vehicles. If the microprocessor frequency matches the radio frequency bands utilized in the vehicle, it can result in EMC issues. 

Sources of EMI in an Automotive System

The vehicle systems we mentioned above are on-board EMI generators. Automotive EMC problems can be caused by on-board as well as off-board EMI sources. Apart from these sources, there are internal receivers that make automotive electronics susceptible to EMI. The table below gives some of the internal and external EMI sources affecting automotive EMC.

Automotive EMC problems are the third-largest form of vehicle pollution after exhaust emission and traffic noise. Compared to conventional internal combustion engine automobiles, electric or hybrid electric vehicles are increasingly becoming victims of automotive EMC issues. Cadence offers a suite of design and analysis tools that can help address automotive EMI issues during the design stage.

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