다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Методы подавления шумов и помех в электронных системах. (Noise reduction techniques in electronic systems)

This article first develops a radiated electromagnetic interference (EMI) model for a gallium nitride (GaN) integrated circuit (IC)-based active clamp flyback converter. Important capacitive couplings, which play a big role in the radiated EMI, are identified, extracted, and validated in the converter. The radiated EMI model is improved to characterize the impact of capacitive couplings. Based on the improved model, techniques to reduce capacitive couplings and the radiated EMI are proposed and experimentally validated.

Modeling and Reduction of Radiated EMI in a GaN IC-Based Active Clamp Flyback Adapter

For the radiated electromagnetic interference pre-compliance diagnosis in power electronics systems, the measurement of common mode (CM) currents, impedances, and voltages are essentially important. In this article, two measurement issues are first identified in CM current and impedance measurement. The first is the coupling between the cables attached to a power converter and the coaxial cable connected to the measurement equipment. It degrades the measurement accuracy. The second is the coupling between the converter's attached cables and the ac grid. It degrades the repeatability of measurements. To improve the measurement accuracy and repeatability, this article proposes an improved measurement technique to address these two issues. Furthermore, for the measurement of the voltage difference between primary and secondary grounds, this article also identifies two issues. The first is the poor measurement resolution for the low noise voltage in the high-frequency range due to the high magnitude of line-frequency voltages. The second is that the loading effects of the voltage probe can reduce the measurement accuracy. This article proposed a technique to address these two issues. Finally, the proposed measurement techniques were validated on a flyback converter.

Measurement Techniques of Common Mode Currents, Voltages, and Impedances in a Flyback Converter for Radiated EMI Diagnosis

Recent years have witnessed evolutions of topologies and applications of wide bandgap devices in flyback converters, in order to improve efficiency and power density. However, due to the increased topology diversity, and the increased high frequency noise, unprecedented EMI challenges are created. Those challenges lead to advances of EMI modeling and reduction techniques, to be generalized for different topologies, and to be effective at higher frequency ranges. The emerging flyback EMI challenges and research advances are analyzed in this paper. Future challenges and development of EMI in flyback converters are discussed.

Advances of Modeling and Reduction of Conducted and Radiated EMI in Flyback Converters

In power converters, common mode (CM) noise can radiate to cause radiated electromagnetic interference (EMI). Resistive, inductive and capacitive parts of the CM inductors can interact with the antenna to induce damping effect or additional resonance. The resistive component is desired for radiated EMI reduction with resonance avoided and noise energy dissipated. This paper researches on the equivalent core loss resistance and its application on CM inductors for radiated EMI reduction. This paper investigates the equivalent core loss resistance and quantifies its relation with core parameters and winding parameters. Critical factors for the equivalent core loss resistance include the ratio of core’s cross section area over core’s magnetic path length and winding’s turns number. Capacitive part of the CM inductor is also considered given its influence on impedance and on radiated EMI. Parasitic capacitances of both the winding and the core are analyzed. Experimental verification on the core loss based CM inductor design is performed on a flyback converter, with radiated EMI measured in a semi-anechoic chamber.

Design of CM Inductor Based on Core Loss for Radiated EMI Reduction in Power Converters

Electromagnetic interference (EMI) in non-isolated power converters is regulated by extensive standards in many applications. EMI modeling and reduction research is key to develop solutions to achieve EMI compliance. For conducted EMI, there are lots of techniques to analyze noise sources, propagation paths, parasitic couplings, and so on, which are summarized in this survey. Fundamental and general techniques to investigate and to reduce conducted EMI are analyzed. Moreover, in the high switching frequency era and with increasing applications of wide bandgap devices, radiated EMI is becoming an inevitable challenge. Modeling and reduction of radiated EMI, therefore, is becoming an important topic. Recent advances in radiated EMI research for non-isolated power converters are summarized and analyzed. Future EMI research development is discussed.

Juntao Yao

Papers

Modeling and Reduction of Radiated EMI in a GaN IC-Based Active Clamp Flyback Adapter

Measurement Techniques of Common Mode Currents, Voltages, and Impedances in a Flyback Converter for Radiated EMI Diagnosis

Advances of Modeling and Reduction of Conducted and Radiated EMI in Flyback Converters

Design of CM Inductor Based on Core Loss for Radiated EMI Reduction in Power Converters

Advances in Modeling and Reduction of Conducted and Radiated EMI in Non-isolated Power Converters