Research On Modeling And Suppression Methods Of Radiated Electromagnetic Interference From DC-DC Power Converters

With the development of power electronic equipment in the direction of high frequency and miniaturization,the switching frequency of semiconductor switching devices has gradually increased.However,the high-speed switching on and switching off of semiconductor switching devices will generate a lot of electromagnetic noise,which will not only affect the internal electromagnetic environment of electronic equipment,but also interfere with other sensitive equipment in the form of electromagnetic radiation.Therefore,in order to better deal with the challenge of radiated EMI to power electronic products,it is necessary to deeply understand the generation mechanism and propagation characteristics of radiated EMI.The research focus of this paper is to analyze the characteristics of radiated EMI in DC-DC power converters and propose corresponding equivalent behavior models to provide theoretical support for solving the radiated EMI problem in practical engineering.The main contents include:Firstly,the generation and propagation path of common mode and differential mode noise of the power converter are analyzed,and the generation mechanism of radiated electromagnetic interference is studied.Comparing the differential mode radiation and common mode radiation inside the DC-DC power converter,the result shows that the radiated electromagnetic interference intensity caused by the common mode current is more than 10 times that of the differential mode radiation,which proves that common-mode current is the main cause of radiated electromagnetic interference.Secondly,taking Buck converter as an example,a radiated EMI model for DC-DC power converters is established.This model uses Thevenin and Norton equivalent theorem to equate the common mode noise path inside the power converter to a series-parallel connection of voltage source,current source,and impedance.The existing radiation model of external cable is improved so that it is no longer limited to the application of small electrical size.The common mode current and radiant electric field in the system are calculated using this model,and the accuracy of the model is verified by simulation and experiment.Thirdly,by comparing the difference of radiated electromagnetic interference between MOSFET and IGBT power converter,the influences of rising edge,falling edge time and internal parasitic parameters on radiated EMI of the switching device are discussed respectively.The noise source waveform of the switching device is decomposed into two components: trapezoidal wave and oscillation,and the internal relationship between trapezoidal wave,oscillation and radiated EMI is analyzed respectively.The result shows that the shorter the time of rising edge and falling edge of the switching device,the greater the intensity of radiated electromagnetic interference.In addition,the smaller the parasitic capacitance,the higher the center frequency of oscillation,Radiated EMI is more likely to exceed the standard in high-frequency locations.This research provides a theoretical basis for suppressing radiated electromagnetic interference.Finally,the suppression method of radiated electromagnetic interference of DC-DC power converter is studied.Four methods are applied to suppress the radiated EMI from the noise source and the noise propagation path.Combining the relevant research theories in Chapter 3 and Chapter 4,for each suppression method,the inhibition mechanism is analyzed,and an experimental platform is built to verify the effectiveness of the suppression method.