Electromagnetic Interference Behavior Research Articles

Comprehensive Conducted Emission Analysis of the Three-Phase and Single-Phase LLC Resonant Converters for EV Application

Resonant <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter is a preferred candidate for emerging electric vehicle (EV) applications, thanks to its high efficiency and high power density characteristics, which are achieved due to high switching frequency and soft-switching operation. On the other hand, planar transformers (PTs) for EVs offer power density in a small package and withstand vibrations. However, large parasitic capacitance is a characteristic of PT, which along with the large <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> of the converter leads to severe conducted emission problems. Therefore, multifold complicated and bulky electromagnetic interference (EMI) filters are required to suppress conducted noise and meet the requirements of the relevant standards. In this article, a comprehensive analysis has been conducted to model and study both single-phase and three-phase <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converters from a conducted noise perspective. With this study, a better understanding of the EMI behavior of these converters can be obtained. Owing to the symmetrical design of the three-phase converter, several harmonics cancel out each other, resulting in lower common-mode (CM) emissions. It is also shown that differential-mode (DM) current generated from the three-phase converter contains lower peak amplitude at high frequency. For comparison purposes, two prototype converters based on the conventional single-phase and the three-phase configuration are fabricated and their conducted emissions are measured and compared experimentally. Simulation and experimental results verify that the three-phase converter effectively suppresses CM and DM noise by a considerable amount.

A 2–10 MHz GaN HEMTs Half-Bridge Driver With Bandgap Reference Comparator Clamping and Dual Level Shifters for Automotive Applications

Gallium nitride (GaN) high electron mobility transistors (HEMTs) are promising power devices due to their excellent characteristics. However, GaN HEMTs have vulnerable gates that are susceptible to noise and voltage spikes, limiting their implementation in power converters. This paper presents a GaN HEMTs half-bridge driver with bandgap reference comparator clamping (BGRCC) and dual level shifters (DLS) for high switching frequency automotive applications. The BGRCC scheme can adaptively clamp the bootstrap rail voltage at an appropriate level with acceptable voltage ripples, which guarantees the safety of high-side GaN HEMT. Meanwhile, DLS scheme is applied in both the high- and low-side driving path to effectively drive the GaN HEMTs with low propagation delay and high dv / dt immunity. The proposed driver is fabricated in 0.18 μm high voltage bipolar-complementary metaloxide semiconductor (CMOS)-double-diffused metaloxide semiconductor (DMOS) process and can support 2–10 MHz operating. The functionality and performance are verified by experimental results. A buck converter utilizing this driver with GaN HEMTs can achieve maximum efficiency of 91.58% with quite electromagnetic interference behavior in the 16.5-W output power rating when operating at 2 MHz, which is superior to conventional silicon-based power converters and suitable for automotive applications.

EMI Measurements, Modeling, and Reduction of 32-Bit High-Performance Microcontrollers

This paper presents a full electromagnetic interference (EMI) study of high-performances 32-bit microcontrollers (MCU). First, two types of standard radiated emissions measurements have been executed on a device. Then, EMI modeling has been simulated with the help of a predictive SPICE model. Finally, modifications has been studied and implemented in order to reduce the EMI levels. The aim of this paper is to be able to predict, during the design stage, the level of electromagnetic emissions in order to establish design, layout, or packaging rules. The modeling part, which is the most important, is intended to represent the EMI behavior of a microcontroller when it is running in a noisy mode (reading accesses to the embedded nonvolatile memory Flash memory and CPU running). The simulated results have then been correlated with radiated emission measurements. All measurements are following the International Electrotechnical Commission 61967-2 or 61967-3 standards whereas the model has been simulated by the ELDO simulator.

Improving Electro-Magnetic Interference of Embedded Systems Through Jittered-Delay Desynchronization

ICs are required to satisfy always increasing performance needs for modern electronic applications. This results in higher operating frequencies for digital circuits, thus increasing the generated Electro-Magnetic Interference (EMI). International standards and industrial regulations, in domains such as automotive applications, enforce strict rules about the EMI behavior of electronic systems. Thus, EMI is becoming a major concern for designers, with direct implications on the commercial viability of a product. In this paper, we apply the desynchronization methodology, down to the physical layout level, to an industrial microprocessor used in automotive applications. The results show that we can both use the advantages from desynchronization, i.e., average case performance and better variability tolerance, and achieve significant EMI reductions, without excessive costs in area or power consumption. While our paper confirms earlier claims that indeed asynchronous circuits reduce EMI, it also shows clearly that by far the largest EMI gain can be obtained by adding dynamically varying delays (which in turn cause local clock jittering) on top of desynchronization

A Microcontroller Instruction Set Simulator for EMI Prediction

This paper predicts programspsila effect of time-domain electromagnetic interference (EMI) on a simple microcontroller. Using the instruction current concept and a modified instruction set simulator (ISS) for this purpose, this paper can predict, in the time domain, accurate conducted EMI behaviors when different programs are running on this system. Different program codespsila EMI behaviors are predicted, and all of these codes fit well with the measurement results. The modified ISS is adapted to estimate the pipeline effect of a microcontroller and to give an accurate current profile of any complex multi-instruction program. By using the instruction current model and the proposed ISS, this paper can predict the EMI behavior of a very complex program-a simple home-made operating system (OS) kernel. To the best of our knowledge, this paper is the first work on observation and prediction of EMI behavior of an embedded system OS kernel.

Identification of Essential Coupling Path Models for Conducted EMI Prediction in Switching Power Converters

A knowledge of conducted electromagnetic interference (EMI) generation and propagation mechanisms can aid the engineers working in the field of electromagnetic compatibility (EMC). This paper presents a method, called essential coupling path models, to investigate the conducted EMI coupling in switching power converters. Three modes of conducted EMI noise: the mixed-mode (MM), the intrinsic-differential-mode (IDM), and the common-mode (CM) are identified by time domain measurements associated with an ac-dc half-bridge converter. The derived models assume that the lumped parameters' circuits represent the noise generation and propagation paths that allow easy physical interpretations. The experimental results show good agreement by the comparison of measured and predicted MM, IDM, and CM noise emissions with filter included. The proposed method is easy to apply in practice for understanding, diagnosis, and evaluation of EMI behavior

Numerical and Experimental Investigation of Radiation Caused by the Switching Noise on the Partitioned DC Reference Planes of High Speed Digital PCB

Influence of the partitioning and bridging of the power/ground planes on the radiation caused by the switching noise on the dc reference planes is investigated both theoretically and experimentally. Based on the three-dimensional finite-difference time-domain modeling, the electromagnetic interference (EMI) performance of the partitioned power/ground planes is studied. Radiated emission at the 3-m distance from the tested boards is measured in a fully anechoic chamber. The measured and the numerical results agree generally well. The radiation behavior of four kinds of partitioned configuration of the power/ground planes is studied. It is found that completely isolating the noise source by the etched slits, or moats, significantly reduces the radiation level at the frequencies near resonance. However, bridges connecting two sides of the moat not only significantly degrade the ability of the EMI protection of the moat, but also excite a new low-frequency resonant mode. The effect of the geometrical parameters, such as the moat size, moat location, bridge width, and bridge position, on the radiation behavior of the printed circuit board is considered. The radiation mechanism of the EMI behavior of the partitioned dc reference planes is discussed.

Conducted and radiated interference measurements in the line-pantograph system

We present the results of a measurement campaign aimed at investigating electromagnetic interference (EMI) phenomena in the interaction between overhead railway power supply lines and pantograph. In order to obtain such data, an experimental setup was assembled in a shielded room, consisting in a short section of overhead line and a full scale pantograph. One of the most interesting results consists in the observation of a very significant (both from the qualitative and the quantitative point of view) difference between the EMI behavior in the switch-on (pantograph going up) and switch-off (pantograph going down) transients.