Research On EMI Radiation Modeling And Simulation Of Switchin Gpower Supply

Comparing to linear power supply, switching power supply has advantages of small size, light weight, high efficiency which makes it the dominant power supply in electronic products. Frequently turning-on and turning-off switches would results surges of voltage and current which is one of the causes of electromagnetic interference (EMI). EMI produced by switch power supply may both affect the normal operation of other parts of the circuit of the electronic products and switch power supply control circuits. Therefore, solving the problem of electromagnetic compatibility (EMC) in switching power supply is important and meaningful.Most of the previous researches are focused on conducted EMI of switching power supply, and only a few of them consider radiated EMI. A more suitable and systematic solution is needed. What’s more, the currently researches on radiated EMI are limited to the space near the switching power supply, but the sensitive circuits are not considered.This paper is focused on a typical Boost converter. Firstly, a theoretical analysis about the radiated EMI issue in switching power supply is done and related theories are introduced. Previously, most of the simulations of radiated EMI are focused on the surrounding space near the switching power supply, without considering the sensitive circuits. In this paper, by means of finite element analysis software Ansoft HFSS, a whole model including box, sensitive circuits inside and outside the box and switching power supply is built. The field distribution in the sensitive circuits is obtained, which proved that the interference of the switching power supply is serious. Finally, the solution of how to choose shielding schedule is demonstrated because there isn’t a scientific and systematic program for choosing a suitable solution to decrease radiated EMI. Choosing the material of the shielding box as the main factor, the efficiency of the shielding at three different frequencies is compared and a more suitable solution is found. This paper provides a new idea for EMC design of switching power supply.