Research On Radiated Electromagnetic Interference Analysis And Suppression Of Half-bridge LLC Resonant Boost Switching Power Supply

With the miniaturization and integration of PCBs,the electromagnetic interference problems are becoming more and more serious.These electromagnetic noises interfere with the stable operation of other devices while affecting the normal operation of their own devices.Therefore,research on electromagnetic compatibility of power electronic devices has become a top priority.This paper toke Boost+LLC circuit as the research object,analyzed and designed its circuit structure and built the model in the circuit software,extracted the noise source current,combined the radiation noise mechanism research and calculation derivation,performed the field-path co-simulation and obtained the noise spectrum,proposed the radiation suppression measures,and finally verified the feasibility of the suppression method by hardware experiments.The specific contents are as follows:(1)Analyzed and designed the Boost+LLC switching power supply circuit.Chose the DCM Boost+half-bridge LLC circuit as the research object through theoretical analysis and comparison;Selected the Electronic parameters by combining with the design requirements and formula calculation,such as the inductance L,the switch tube,the output capacitor C,the resonant inductor Lr,the magnetizing inductance Lm and the capacitor Cr.At last,built the whole machine Boost+LLC circuit in PSIM circuit simulation software.(2)Analyzed the radiation noise of the Boost+LLC switching power supply circuit.Analyzed the reasons for the influence of MOSFET,inductors and capacitors on radiation emission,and determined the MOSFET as the main radiation interference source;Analyzed the radiation noise mechanism,and derived the calculation formula of electric field radiation noise and magnetic field radiation noise;Extracted the circuit on MOSFET and achieved the field-circuit co-simulation;Based on this,analyzed the suppression of the radiation interference source under different capacitance parameters.(3)Studied the radiation suppression based on electromagnetic shielding.Analyzed the calculation principle of the gap,the shielding mechanism of the metal good conductor and the slotted cavity;Compared the shielding effectiveness of the metal good conductor with the slotted cavity under the same material in CST microwave studio,and optimized the shielding effectiveness by changing the area,the shape and the size of the hole.(4)Established the hardware circuit and radiation experiment of the Boost+LLC switching power supply.Selected UC3854 and NCP1399 as the control circuit chip;On this basis,built the hardware circuit,and carried out the radiation suppression experiment;Verified the correction of the theoretical simulation and the effectiveness of the suppression measures.