Synthesis of PWM Dc-to-Dc Power Converters

Citation

Zhou, Dongyan (1996) Synthesis of PWM Dc-to-Dc Power Converters. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/JEK6-1P40. https://resolver.caltech.edu/CaltechETD:etd-01312005-163350

Abstract

A novel systematical synthesis method of PWM dc-to-dc converters is established in this thesis. The new method can generate converters in an efficient way, with clear circuit insight.

The family of PWM dc-to-dc converters is defined to include converters with multiple-input and/or multiple-output; converters with arbitrary switched networks in each switching period; and converters with loops consisting only of capacitors and possibly a voltage source or cut-sets consisting only of inductors and possibly a current source in the individual switched networks.

This method is based on the equivalent ac and dc circuits of a PWM dc-to-dc converter, which consist only of switches in the converter.

The first part of the synthesis procedure is carried out without the participation of reactive elements. For a given number of switches and other requirements, the ac topology and its control sequence can be decided. Basic properties of ac and dc circuits are derived. Moreover, the topological relation between an ac circuit and its associated dc circuits is discovered. Based on the volt-second and ampere-second balance equations of the ac circuit and the matrix representation of dc circuits, a formalized dc model in terms of average switch voltages and currents is first developed. Consequently, the dc conversion ratio and switch implementation can be derived for each pair of ac and dc circuits. The associated dc circuits of the given ac circuit can be formally generated and sorted out according to the required dc conversion ratio, the types of switches, the order of the dc circuit, and other properties.

The insertion procedure for reactive elements is also formalized. The basic procedure generates the converters with the minimum number of inductors and capacitors. A modification of the basic procedure is given to generate converters with continuous input and output currents.

Different classes of converters are generated by the new synthesis approach. A class of three-switch converters are discovered, each of which has a loop of capacitors and possibly the voltage source. Some of these three-switch converters are of special practical interests. Also, a class of three-switch, and two-output converters are discovered that can provide opposite polarity output voltages without using a transformer.

Most importantly, this systematic synthesis method provides an analytic and circuit-oriented approach to develop new converter topologies in order to meet new requirements introduced by ever growing number of applications.

Thesis Files