Research On High Frequency Characteristics Of Filter Based On Electrical Fast Pulse Group

With the increase of the working frequency of the switching power supply, more and more electronic noise spread outward in the form of electromagnetic interference, which leads to the more serious problem of electromagnetic compatibility between the electrical and electronic products and thus the electromagnetic environment of electronic equipment has been seriously polluted. Therefore the relevant electronic products must meet the electromagnetic compatibility standards. EFT filter is one of the effective methods to suppress the EFT interference. But because of the parasitic parameters in the various components, sometimes the EFT filter is not particularly effective for the suppressing of the EFT noise. So in order to improve the performance of the filter, it is necessary to extract and restrain the parasitic parameters of EFT filter.This thesis firstly analyzes the harm of EFT and the general methods to deal with the EFT noise. It describes the basic principles of EFT including working principle of EFT, analysis of pulse group spectrum, energy transferring and loss and analyzes the characteristics of energy distribution. Then the thesis describes the insertion loss which is the main performance of EFT filter, and explains how to obtain the insertion loss of the EFT filter based on the network analyzer combining S parameters. A model of EFT filter with discrete components is established with higher frequency, and a model of the parasitic parameters between discrete elements is also established with higher frequencies. The impedance measurement can be used to calculate the parasitic parameters of the EFT filter, which can eliminate the parasitic parameters precisely.This thesis adopts the method of "negative parameter offset" to suppress the corresponding parasitic parameters. According to the principle of dimensional equivalence, the inductance is eliminated by inductance and capacitance by capacitance. Instead of common mode choke, the bifilar windings in series and its different placement can reduce the effect of leakage inductance effectively. After the suppression of the parasitic parameters, the performance of the EFT filter with higher frequency is significantly improved. Through the experimental measurement of the EFT filter, it is found that the filter performance has a great improvement at a higher frequency. At last, a practical application case is used to prove the correctness of the thesis.