正激式变换器输入端共模噪声的研究

Study of common mode noise in the input side of a forward converter

噪声源的研究对噪声控制是十分重要的,掌握噪声特征是噪声控制方法比较以及滤波器设计的基础。本文以电路理论为基础,建立了单端正激式变换器由功率MOSFET的漏极与接地散热器之间寄生电容所引起的输入端共模噪声分析模型,借助于PSPICE仿真工具,分析了硬开关和软开关情况下所产生的共模噪声。本文的工作将有助于开关式电源电磁干扰诊断和滤波器的设计。

The study of noise sources is essential in noise control,know well characteriza-tion of noise is the basis for comparison of methods and for filter design.Based on cir-cuit theory,this paper gives an analysis model of common mode noise in the input side of a forward converter,which is caused by ground current due to the periodic instantaneous change of the voltage across the parasitic capacitance between the drain of the MOSFET and the chassis ground.By means of simulation with PSPICE program,the paper also pre-sents the effect of soft switching on CMN in comparison with hard switching.Understand-ing the generation mechanism of CMN makes the EMI diagnosis and filter design less of a black magic.