Below are the questions asked during the live event, along with their respective answers.

Q: You mentioned the importance of ground, so what’s your recommendation for grounding under an inductor or ground under coupling capacitors?
A: Grounding under inductor really depends on the inductor types, the orientation of the inductor on the PCB (vertically or horizontally), the number of turns of the inductor, etc. So it is generally hard to say. Many people are for the idea of putting ground plane under the inductor because it can block the magnetic field of the inductor, but people also find the plane can bypass the inductor. I would say it all depends on the layout. But for common mode choke, generally no ground should be put near the common mode choke.

Q: What’s your view on simulation software, particularly finite element-based software?
A: FE-based simulation tools are more accurate, but often take a long time to build a simple model, and the learning curve is relatively long, not to mention the license fee of such simulation software. We come from a strong electronics design background, so we like the SPICE-based tool. It is simple to learn, fast to build a model and by putting parasitic components in the system, design engineers can also learn the impact of these parasitic parameters in the system, so they get to know the EMC much better.

Q: What are the best packaging techniques for HV and LV wires in electric vehicles?
A: HV LV coupling has now become some vehicle manufacturers’ EMC specification. Generally speaking, you want to keep the HV and LV as far as possible. If possible, shield either or both cables. If you cannot shield or keep the distance far due to design constraints, you can insert a thin aluminium wall in between.

Q: Should grounding be common for both or separated?
A: When we say ‘grounding’ in the automotive, we mean LV system. For HV system, generally you need to isolate the HV lines. The HV lines will have capacitors to the ground, but you need to meet the leakage current requirement.