Far field radiated emissions prediction of a flyback adapter with curved cables utilizing electromagnetic simulation method

Radiated emissions (RE) testing has long been a challenge in the development of a switched mode power supply (SMPS) with respect to electromagnetic compatibility performance. Accurate far-field RE prediction can effectively help SMPS designers reveal and understand the mechanisms of radiation generation, and reasonably suppress it. In this paper, a model for predicting the radiation from a single excitation source and a parasitic radiator for a flyback adapter are proposed after analysing the common mode voltage and current paths. Then, novel methods are proposed to predict the far-field RE of the flyback adapter based on measurements and electromagnetic simulations. Using these methods, the 10-m far-field radiation of the flyback adapter under the curved cables layout is accurately predicted and verified by experiments. Then, the characteristics and influencing factors of the radiation are analysed, including the far-field patterns, the load volume, and the sag degree of the output cable. Finally, a suppression design of the capacitor-inductor (CL) notch filter is designed for the frequency points that are above the standard limits, and the RE are reduced to less than 30 dB mu V/m from 30 to 300 MHz. The research methods proposed in this paper have good reference significance for radiation analysis and prediction of power electronic devices. Based on the CM excitation voltage spectrum measurement and the electromagnetic-simulated radiation transfer functions, an accurate prediction of the radiated emissions of a low-power flyback adapter with complex cables is achieved.image