Large Signals in Switching Converters

Citation

Erickson, Robert Warren, Jr. (1983) Large Signals in Switching Converters. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/CN9A-WY51. https://resolver.caltech.edu/CaltechETD:etd-01112006-110638

Abstract

The behavior of switching converters under large-signal conditions is modelled and analyzed. Two major problems are of interest: the reduction of the distortion which occurs in switching amplifiers, and the stabilization of switching regulators for all transients which are expected to occur.

In Part 1, a large-signal model is described which predicts the simple harmonic distortion generated inherently by switched-mode amplifiers. The causes of this distortion are identified, and relatively simple design techniques for its reduction to an acceptable level are presented. A particularly attractive feature of the method is the ability to compute harmonic magnitude and phase using linear circuit models and Bode plots.

The method is extended to account for intermodulation distortion. Additional effects not described by the model are also discussed, including crossover distortion and bandwidth limitations.

Although in its simplest form the buck converter is inherently linear, considerable distortion may arise when it is preceded by an input filter. This problem is solved as an example of the usefulness and circuit-oriented nature of the method.

In Part 2, a large-signal switching regulator model is derived, and prominent features of the transient response are determined. In particular, the various regions of operation are identified in the state plane, analytical expressions are found for the equilibrium points of the system, and computer-generated transient waveforms are obtained.

As an example, a boost regulator is investigated, and is found to be stable for small signals but unstable for large transients. Approximate analytical expressions are found for the waveforms and salient features of the response, and a number of ways of obtaining global stability are discussed.

Experimental evidence is presented to verify both the distortion and stability analyses.

Thesis Files