Electromagnetic Interference Modeling For Power Converters

This dissertation focuses on modeling technique of electromagnetic interference (EMI) for power converters. It includes following modeling works for: power semiconductors, passive component, printed circuit board (PCB), conducted EMI, and radiated EMI of power converters.The existing high frequency models of power semiconductors aren't so accurate that they can't be applied in conducted EMI simulation. To improve these models, based on detailed mechanism analysis, high frequency models of two typical power devices - double carriers PIN diodes and single carrier power MOSFET are proposed for EMI simulation. For the PIN diode, its major transient behaviors are forward voltage recovery and reverse current recovery. This dissertation describes these performances by lumped-charge approach, and then developed an improved lumped-charge model for PIN diode and a corresponding parameter extraction approach, which can reduce parameter measurement and enhance parameter accuracy. In addition, based on the analysis of the change of inter-electrode capacitances as changing working condition, a sub-circuit model for a power MOSFET is developed and all model parameters can be easily extracted by data sheet.Conducted EMI includes two modes: differential-mode (DM) and common-mode (CM). This dissertation puts forward an accurately modeling approach. These two kinds of interferences have different sources and spreading path. Their simple time-domain model and frequency-domain model are built in this dissertation too, which provides theory foundation for qualitative and quantitative EMI analysis.Aiming at the feature of CM interference in power converters, a new approach ?intrinsic dynamic nodes potential balance is proposed. By building node pair with balance potential and making use of the intrinsic stray capacitor of power semiconductor devices, the CM current can be suppressed effectively. This approach can be applied in several kinds of power converters.In the radiation aspect, the features o radiation sources in power converters are discussed. The radiation models of DM current and CM current in cables and radiative characteristics of cables and high frequency current loops in the converter are also discussed.