[Editor's Note] Electromagnetic noise generated during IT product design causes fatal defects such as product performance degradation and malfunction. Recently, with the transition to electrification of automobiles, miniaturization of products, and expansion of the use of high-band frequencies (millimeter waves) such as 5G and 6G communications, the possibility of malfunction of devices and systems due to intentional and unintentional electromagnetic noise is gradually increasing. As the importance of EMI/EMC design is receiving attention, e4ds news holds an Analog Day every year to bring together EMI/EMC experts to share the latest technology trends and seek solutions.

We met with Professor Ji-Sung Kim, who will present the key session 'SMPS Noise Countermeasures' at this year's Analog Day , and had a conversation. Professor Ji-Sung Kim worked as a senior researcher at Samsung Electronics and an associate professor at Suwon Science University. He is currently a visiting professor at KAIST Cho Cheon-Sik Mobility Graduate School and CTO of CPS Tech. His main field is EMI/EMC, and he is researching important technologies to reduce noise generated during electronic product design and minimize electromagnetic waves harmful to the human body to secure high-reliability design.


■ Please introduce your main research areas and main activities.

His research mainly focuses on electromagnetic waves in high-speed digital systems and power systems to ensure high-reliability design. We are also conducting research on wireless power transmission technology in the IT, home appliance, and automotive fields using electromagnetic waves, high-speed signal transmission technology for automobiles and IT products, and signal and power noise.

As an expert in the field of research, he is active as an associate director of the Korean Institute of Electromagnetic Engineering and Science and also serves as the chairman of the EMC research group within the society. In addition, he provides various technical lectures and guidance to employees of large and small domestic companies on related technologies.

■ Why is design considering EMI/EMC becoming increasingly important?

Research on science and technology continues along with the great technological movement of the 4th Industrial Revolution. It is expected that the era of new industries such as 5G technology, the Internet of Things, smart homes, smart factories, e-mobility, and connected cars will arrive, and related materials, parts, equipment, and service industries are also changing.

On the other hand, in terms of technology, there are many challenges to be solved, such as developing new materials, operating faster wired and wireless communication speeds, and considering energy and environmental issues. In particular, in terms of electromagnetic waves, or EMI/EMC technology, the emergence of new technologies is expected to increase the possibility that intentional and unintentional electromagnetic waves will affect devices and systems, causing malfunctions.

Therefore, when integrating new technologies, it is becoming increasingly important to design each device so that it can operate normally on its own while coexisting with other devices. Accordingly, research in the field of EMI/EMC is currently in continuous technical demand not only in information and communication, home appliances, and automobiles, but also in most fields that include electronic circuits, and its importance is increasing as the environment changes, such as faster signal speeds and smaller products.

■ Why does SMPS noise occur?

Switched-Mode Power Supply (SMPS) is gradually expanding its usage environment due to its high efficiency, but the electromagnetic noise caused by the switching operation has caused many problems since the past. In line with this, countermeasure technology to solve the problem has also been continuously developed.

Recently, the demand has expanded widely to include small products such as smartphones, renewable energy fields such as solar inverters, and electric vehicles, so electromagnetic wave response devices and design technologies are needed.

Basically, noise generated in SMPS occurs when switching elements such as MOSFETs or IGBTs or diodes switch. Electromagnetic noise caused by harmonics of the switching frequency, resonance noise generated in the path of high-frequency current during switching, etc. appear in the form of conduction or radiation.

Noise generated by switching can appear differently depending on the characteristics of the device, circuit, and PCB design, and the noise generated at this time can be transmitted to the input line by conduction, or can cause electromagnetic problems due to capacitive coupling by mutual capacitance with nearby conductors, or inductive coupling by mutual slope generated in high-frequency current paths.

■ What solutions are required to control noise generated from high-frequency switching?

There are various countermeasure technologies for electromagnetic noise generated from SMPS depending on the cause and path of generation.

Snubber circuit technology is being used to reduce the cause of noise, PCB layout technology is being used to minimize parasitic components, methods are being used to improve the fundamental circuit topology, and methods are being used to control switching speed or frequency. In addition, we are improving the characteristics of components such as switch elements and capacitors, and also using filter technology and shielding technology.

In addition, countermeasure technologies are being used to reduce electromagnetic noise caused by common mode or differential mode current paths, and improved technologies, including analysis and measurement technologies, are continuously being proposed.

■ Please give a brief introduction to the topics that will be covered at this Analog Day .

We will explain the causes and countermeasures for electromagnetic noise generated from SMPS. There are many types of SMPS, but due to time constraints, we will cover the noise generated from the most commonly used DC-DC converter. We will summarize the causes of noise and design countermeasures to reduce noise.

■ If you have any final words for e4ds news readers,

EMI/EMC problems occur in all electronic products and must be solved for product reliability and standard certification. On the other hand, if you try to solve this problem when it becomes a problem rather than solving it at the design stage, it will require a lot of effort, time, and money.

Therefore, minimizing the causes during the design phase is the most effective method. I hope that this Analog Day will be of great help to readers in designing their products.

thank you

Meanwhile, Analog Day, which will feature various sessions including KAIST visiting professor Kim Ji-seong's session on 'SMPS Noise Countermeasures', EMI·EMC standard/certification trends, wireless charging market outlook, and EMI countermeasures according to the development of wireless power transmission technology, is scheduled to be held in the main auditorium of the Gangnam Station Conference Center on December 9.