The art of soft switching and control of power converters

This dissertation is comprised of two parts. The work in part I investigates the characteristics of both active and passive soft-switching methods. Through this research, general electrical and topological properties have been derived that enable simpler and more efficient soft-switching methods to be found for converters and inverters. A comparison study was conducted to characterize the loss mechanisms, component stresses, and overall efficiencies of a group of active voltage-mode soft-switching methods including two new methods discovered during this research. It was found that non necessarily all soft switching methods improve efficiency, only the methods that softly switch the auxiliary switch, minimize redirection current, and recover the auxiliary circuit energy were effective. After the comparison study, a new active soft-switching method that uses magnetic amplifiers to obtain nearly optimal efficiency is proposed for switching power converters, inverters, and amplifiers. This method requires no expensive sensors or complex control circuitry. It is ideal for power amplifiers where the load current is widely changing. The research effort was extended to passive soft-switching methods. General topological and electrical properties of lossless, passive soft-switching converters with defined characteristics are derived. The properties are then used to develop a synthesis procedure for the creation of new converters. After the converters are synthesized, a simple and effective design procedure is formulated to obtain the component values. The synthesis procedure is extended to inverters with promising results by presenting two new inverters with low component counts.; Part II of this dissertation investigates a class of non-linear control methods for the control of class-D audio amplifiers. A new nonlinear control technique is proposed that has one cycle response, does not need a resettable integrator in the control path, and has nearly constant switching frequency. An experimental 0–20 kHz bandwidth power audio amplifier using the control method demonstrates the applicability of this control technique for high fidelity audio applications. Several active soft-switching methods are combined with the control technique to demonstrate a high fidelity, high efficiency, audio power amplifier.; All findings in the dissertation are supported with experimental results...