Switching model power supplies (SMPS) are widely used in applications ranging from small consumer electronics to large industrial equipment. Most SMPS employ switching devices that rapidly and repeatedly change states producing high-frequency electromagnetic interference (EMI) due to the large di/dt and dv/dt in the circuit waveforms. The prediction of far-field EMI for SMPS can not only shorten the production cycle and reduce the measurement cost, but also can provide a very valuable reference for the EMC design of SMPS. In this talk a radiation prediction method of SMPS is proposed to predict the noise level of SMPS in the standard measurement of the 3m semi-anechoic chamber, and divides the SMPS into power cables, PCB and shell. The power cable serves as a radiation antenna, the PCB circuit containing the switching device and the digital chip serves as the radiation source, and the shell serves as a measure to eliminate the radiation of the PCB. First, the shell of the SMPS is used to eliminate the influence of the radiation caused by the PCB on the estimation accuracy. Then, the excitation signal of the radiation is obtained through full-circuit simulation. In circuit simulation, intelligent algorithms and other technologies will be employed to establish high-frequency equivalent circuit models of related devices. Finally, the improved antenna model is employed to achieve the final radiation prediction.
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