Research Of The EMI Filter For High Voltage Resonant Converter

In recent years, with the miniaturization of the switching power supply in volums and the improving in switching frequency, it leads to the noise increased. Resonant converter can reduce the switching loss and impro ve switching devices EMC characteristics, so resonant converter widely used in switching power supply. However, because EMI characteristics of resonant converter are different from the PWM converter, the understanding of the technology is still lack of comprehensive. Therefore, it is necessary to characteristics of EMI resonant converter for more comprehensive analysis. According to the characteristics of high voltage resonant power supply, this paper researches on the design of EMI filter applied to the power supply.This paper firstly introduces the research status of EMI filters of switching power supply and the current problems. Second, the mechanism and suppression method of EMI of switching power supply were analyzed in detail. Third, through the analysis of the design principle of high voltage resonant converter and the EMI filter design method, this paper focuses on the spectrum of resonant converter and PWM converter as well as their worst working condition. The paper also contrast analyzes their spectrum difference and puts forward the principle of EMI filter design. The most important, this paper focuses on analyzing the common mode noise source of high voltage resonant converter, and puts forward the common mode and differential mode interference noise suppression method. Last but not least, on the one hand, by establishing the model of high frequency common mode choke, this paper analyzes its effect on EMI noise characteristics of the power system. O n the other hand, combined with the resonant converter design, the paper present methods for adjusting the common mode choke coil parasitic parameters and optimization design of the resonant inductor, and even complete reducing the coupling between compo nents by optimizing the winding mode of common mode choke.In the process of research, this paper uses simulation software, such as PSPICE, ANSYS and ANSOFT, and the experimental platform of high voltage power supply to verify the theoretical analysis.Finally, we finish the high- voltage power supply prototype, and it satisfies the GJB151A-97 CE102, CS101, CS114, CS115, CS116 requirements for EMC of products.