Study On Far Field Electromagnetic Radiation Model And Simulation Of A Flyback Power Supply

The current and voltage, whose amplitudes are high, and rates of changes are fast, will be produced, when the switching-mode power supply(SMPS) is working. The current and voltage, whose amplitudes are high, and rates of changes are fast, can not only produce strong EMI problem around the circuit, but also emit out through the cables which add to the PCB. The far field radiation uaually interfer the other radio circuit which is around it, and the radiation will produce RFI filture. So it is important to study the Far-field radiation mode of the SMPS. It will have theoretical and practical use. In this paper, the Far-field electromagnetic radiation mechanism is studied among a Flyback power supply, and the model of the Flyback Power Supply is bulit up. Anter that, the radiation characters and effectors are also simulated and studied. In this paper, the main works of this paper as follows:The far field electromagnetic radiation interference mechanism in electronic circuit is introduced, the character and mechanism of a actural Flyback power supply is analyzed. The High amplitude and quick changes voltage and current will produce Electromagnetic Interference, and the interference will emit out by the cables.Some effecters of the SMPS radiation are identified, such as the length of cables and the position of the cables and the impedance between L/N and PE and the earth. A simple radiation model of Flyback power supply is bulit, and a 3D model is bulit in Ansoft HFSS.The factors, such as the position of the cables, the length of the cables, the impedance of the cables and the ground etc, are studied. And the models under different condiction are builed. The effects are also studied.Different experiments are designed under different condiations with a simple exciation. The results of the simulation are compared with the experiments, and the feasibility is verified.The paper will help designers get a clear understanding of the nature of electromagnetic radiation, to guide EMI design of SMPS, then reduce radiated interference and for EMC early to provide a reference for design.