The PCB EMC Analysis Of Multiple Output LLC Series-parallel Resonant Circuit

With the development of the switching power supply towards high efficiency, high integration and miniaturization, intelligent, switching power supply operating frequency increases continuously, and interfere problems become increasingly serious. As a carrier of electrical function, electromagnetic compatibility of PCB should not be overlooked. At present, there are several methods to deal with electromagnetic compatibility of PCB, road, field, and field-circuit method.In this thesis, I present the method of field, combined with half-bridge LLC resonant converter design, and analyze the impact of high-frequency conduction interference for PCB electromagnetic compatibility. Major work is as follows:First, the basic theory of electromagnetic compatibility for switching power supply is elaborated. It includes three key elements of electromagnetic interference that are harassment of the source, transmission routes and sensitive equipment. Because main coupling of PCB is radiation-dominated, I focus on the characteristics of electro dipole and magnetic dipole and analyze the classification and characteristics of near-field to far-field.Second, switching power supply design of electromagnetic compatibility for printed circuit board is presented from two parts. One part is the right choice of active devices; the other is electromagnetic disturbances of the printed circuit board. Specifically, the characteristics of two-layer printed circuit board wiring, ground wire wiring rules, interference suppression and considerations are considered.Third, the design process of half-bridge LLC resonant converter is presented. The schematic design phase, I calculate the parameters of half-bridge LLC resonant circuit and control circuit and select the appropriate components to reduce electromagnetic interference. In addition, I analyze the parameter of the flyback circuit. Electromagnetic compatibility design phase, combining the Cadence SPB16.3and Ansoft Designer6.1, based on field principle, I create models in PCB simulation and analyze the electromagnetic compatibility characteristics of half-bridge LLC resonant converter. According to electromagnetic near-field distribution, PCB layout wiring is optimized, electromagnetic compatibility of PCB is improved.Again, half-bridge LLC resonant converter is tested to confirm the operation and electrical performance. According to the waveforms of half-bridge LLC resonant converter, the characteristics of half-bridge LLC resonant converter are presented.Finally, the design process of half-bridge LLC resonant converter, major research results, and shortcomings are presented.