Navigating EMI Shield Can Selection for 48V Mild Hybrid Systems

What Are the EMI Shielding Challenges in 48V Mild Hybrid Systems?

In the realm of automotive engineering, 48V mild hybrid systems present unique EMI shielding challenges. These systems, operating under standards such as LV148 and ISO 21780:2020, demand sophisticated EMI shield cans capable of suppressing emissions to CISPR 25 Class 5 limits. This compliance is essential as these systems handle voltages up to 70V transients and experience high dv/dt from DC-DC converters and integrated starter-generators (ISGs).

Hybrid systems merge 48V rails for high-demand components like adjustable suspensions and air conditioning with legacy 12V systems, increasing EMI risks due to higher currents and switching noise. The challenge lies in managing elevated EMI emissions from power electronics, addressing thermal and mechanical stresses, and handling transient overvoltages effectively.

How Do Standards Influence EMI Shield Can Selection?

When selecting EMI shield cans for 48V mild hybrid systems, engineers must prioritize compliance with several key standards:

• CISPR 25 Class 5: This standard imposes stringent limits on both conducted and radiated emissions, making it a critical benchmark for shield can performance. Achieving compliance often requires integrating shielding with additional techniques like passive filters or spread-spectrum modulation (SSFM).
• ISO 21780:2020: This standard defines voltage levels and transient handling for 48V systems, guiding the required ratings for shield enclosures to manage potential overvoltages effectively.
• LV148: This standard is central to the EMC and electrical testing of 48V mild hybrid systems, particularly important for components such as DC-DC converters.

Adhering to these standards ensures that shield cans not only reduce EMI but also withstand the operational stresses encountered in automotive environments.

Why Is Material Selection Critical for EMI Shield Cans?

The choice of materials for EMI shield cans significantly impacts their effectiveness in 48V mild hybrid systems. Typically, high-conductivity alloys such as nickel-silver or tin-plated steel are favored for their ability to provide more than 60 dB attenuation at frequencies between 30 MHz to 1 GHz. For applications involving magnetic fields, Mu-metal is often employed due to its superior magnetic shielding properties.

For instance, POCONS USA offers shield cans that integrate seamlessly with advanced layout techniques, providing robust electromagnetic interference mitigation while maintaining compliance with automotive standards.

How Do Thermal and Mechanical Factors Affect Shield Can Performance?

In the compact and high-stress environment of a vehicle's engine bay, EMI shield cans must withstand significant thermal and mechanical stresses. These cans should exhibit low thermal resistance, such as matching the 0.19 K/W Rth(j-c) of onsemi's automotive modules, to handle the heat dissipation effectively.

Additionally, the mechanical design must accommodate vibrations up to 20g and ensure IP67 sealing for environmental protection. These factors are crucial to maintaining the integrity and performance of the shield cans throughout the vehicle's operational life.

What Are Practical Engineering Tips for Shield Can Integration?

Successful integration of EMI shield cans in 48V mild hybrid systems involves several practical considerations:

• Layout Optimization: Employ low stray inductance layouts to minimize EMI sources. This approach is particularly effective in hybrid SC topologies, which can achieve high efficiency with minimal emission.
• Gasket Integration: Utilize integrated gaskets, such as EMI silicone, to ensure 360° contact, significantly reducing crosstalk.
• Testing and Validation: Request LV148 and CISPR 25 test data from suppliers to confirm compliance and performance under real-world conditions. This step ensures that the shield cans meet or exceed the necessary insertion loss requirements.

FAQs

What is the primary function of EMI shield cans in 48V mild hybrid systems?

The primary function of EMI shield cans in these systems is to suppress electromagnetic interference, ensuring compliance with stringent standards like CISPR 25 and protecting sensitive electronics from emissions generated by high-current and high-frequency components.

Why is compliance with CISPR 25 Class 5 important?

Compliance with CISPR 25 Class 5 is crucial because it represents the highest level of EMI suppression required for automotive applications, ensuring that emissions do not interfere with other vehicle electronics or external devices.

How do thermal considerations affect shield can design?

Thermal considerations affect shield can design by dictating the materials and construction techniques used to manage heat dissipation. Low thermal resistance materials are essential to prevent overheating and maintain performance integrity in high-temperature environments.

Can POCONS USA products be used in 48V mild hybrid systems?

Yes, POCONS USA offers a range of EMI shielding components that are compatible with 48V mild hybrid systems, providing effective solutions for managing EMI and meeting regulatory compliance.

What role do gaskets play in EMI shielding?

Gaskets play a crucial role in EMI shielding by ensuring a continuous conductive path, reducing the potential for crosstalk and leakage, and enhancing the overall effectiveness of the shield can.