Resonant inverters and their applications to electronic ballasts and high-voltage power conversions

Abstract

Two novel zero-current-switching dc-to-ac inverters: Class-L and Class-M resonant inverters are presented. They are especially suitable for high voltage applications because of their parallel resonant nature. Lamps, particularly fluorescent lamps in the lighting industry, possess a negative impedance feature and require high voltage to start the ignition process, require operating circuits tailored to meet their characteristics. The two inverters are well-suited in these applications. A detailed analysis, systematic design procedure and experimental verification of the two inverters are given. A Fundamental component analysis in the Fourier series expansion is applied for the analysis of the circuits. Steady state characteristics of the inverters, analytically described by the relationship between the output current and voltage are also graphically represented. This provides insight into the characteristics and design of the inverters. The techniques are extended and applied to analyze the zero-voltage-switching Class-D and Class-E resonant inverters. These four inverters form a family of dc-to-ac resonant inverters in terms of input sources and output characteristics. A unique design procedure is also discussed which is made possible from the construction of constant-gain trajectories in the conductance (impedance) plane, where the conductance (impedance) consists of the resonant tank circuit and the load for a given operating frequency. One of the applications of the dc-to-ac inverters is dc-to-dc converter. The Class-D dc-to-dc converters are illustrated as examples. The analytic techniques are also applied to the analysis of the dc-to-dc converters. The flow of the analysis starts with the zero-voltage-switching (ZVS) dc-to-ac inverter and moves to the ZVS dc-to-dc converters, then the ZVS dc-to-dc converters regulated at fixed switching frequency are analyzed, and finally the ZVS dc-to-dc converter is regulated at a fixed switching frequency with a shunt inductor which operates over a wide range of load. A detailed analysis and design procedure for the ZVS Class-D dc-to-dc converter is discussed. An experimental verification of a 1-MHz ZVS Class-D converter is presented. Good agreement is obtained between experimental and theoretical results.