Frank Z. Feng

Optimal Damping of EMI Filter Input Impedance

Input filter damping has long been recognized as critical for avoiding unintended interactions with a switching power converter. This paper investigates a related problem -dynamic interactions between a converter input filter and the source - and develops optimal damping designs that minimize the dipping in the input impedance of a filter seen by the source. Three different damper circuits are studied and for each an analytical model that defines the optimal damping resistance is presented. Performances of these damping methods are compared in terms of achievable damping effects, power dissipation, as well as size and volume of damping capacitors and inductors. A case study is also presented to illustrate the effects of filter input impedance dipping on system stability and the mitigation of such stability problems by filter damping.

Behavioral modeling methods for motor drive system EMI design optimization

Electromagnetic interference (EMI) filtering is a critical driver for volume and weight for many applications, particularly in airborne and other mobile platforms. Because of the lack of the ability to accurately model system EMI behavior, EMI filter design usually cannot start until EMI measurement results have become available. This often leads to costly schedule delay and disruption, and the resulting designs are suboptimal at the best. This paper presents systematic EMI modeling methods that solve this problem and enable optimal system EMI solutions to be developed concurrent with the design of the rest of the system. The proposed methods use linear and piece-wise linear behavioral models that are easy to parameterize and to simulate, thereby avoiding the need for detailed modeling of board-level interconnects and the use of complex physics-based semiconductor device models. Both differential-mode and common-mode EMI are considered. The proposed modeling approach is verified in two motor drive systems for which model predictions and experimental measurements are presented and compared.

Optimal damping of EMI filter input impedance

Input filter damping has long been recognized as critical for avoiding unintended interactions with a switching power converter. This paper investigates a related problem -dynamic interactions between a converter input filter and the source - and develops optimal damping designs that minimize the dipping in the input impedance of a filter seen by the source. Three different damper circuits are studied and for each an analytical model that defines the optimal damping resistance is presented. Performances of these damping methods are compared in terms of achievable damping effects, power dissipation, as well as size and volume of damping capacitors and inductors. A case study is also presented to illustrate the effects of filter input impedance dipping on system stability and the mitigation of such stability problems by filter damping.