Advanced filters and components for power applications

Abstract

The objective of this thesis is to improve the high frequency performance of components and filters by better compensating the parasitic effects of practical components. The main application for this improvement is in design of low pass filters for power electronics, although some other applications will be presented. In switching power supplies the input and output filters must attenuate frequencies related to the fundamental switching frequency of the converter. The filters represent a major contribution to the weight, volume and price of the power supply. Therefore, aspects of the design of the switching power converter, especially those related to the switching frequency, are limited by the high frequency performance of the filters. The usual methods of improving the high frequency performance of the filter includes using larger, better components. Filter performance can improve by using higher quality inductors and capacitors or by adding high frequency capacitors in parallel with the filter capacitor. Also, an additional filter stage can be added. All of these methods add significant cost to the design of the power supply. If the effect of high-frequency parasitic elements in the components can be reduced (at a low cost) the performance of the filter can be enhanced. This allows the development of filters with much better high frequency attenuation, or the reduction of filter size and cost at a constant performance level. In filtering and other applications, the ability to reduce the effect of parasitic elements will be a technique that will enable many high-frequency designs. Specifically, this thesis will present two techniques that can be used to reduce the effects of parasitic inductance and capacitance. One technique,

(cont.) called inductance cancellation, is used to reduce the amount of parasitic inductance in a path of interest. The other technique, capacitance cancellation, will reduce the effect of a parasitic capacitance in an inductor. The techniques introduced here cannot be used to improve performance of passive components in all applications. These techniques, though, do provide major improvements in most filtering applications, an application in which parasitic components play an important role in the design.