Analysis and Design Approach for Converters with Large Signal Variations

Abstract

Accurate large signal analysis of Power Electronics converters is essential for achieving high performance and reliable designs. Converter topologies with large signal variations are conventionally analyzed using numerical methods, averaged models, or inaccurate analyses. In this thesis, a Laplace based theorem (LBT) is developed to analyze and derive the steady state response of a class of switching-mode power converters that can be modeled by Ordinary Differential Equation with periodic input. Although LBT is based on Laplace transform which is a linear system analysis tool, it introduces a new tool to analyze a piecewise linear system such as switching power converter. The proposed method is especially useful to analyze resonant converters and has many applications in the design and analysis of such converters and their control systems. The proposed method is applied to a full bridge Series Resonant Converter (SRC) topology with both variable duty cycle and variable frequency control. Using the proposed method continuous/discontinuous conduction modes (CCM/DCM) of SRC are analyzed. Closed form and analytical expressions for converter gain, current phase lag, and ZVS boundary are found and novel optimized converter design approach is proposed without resorting to numerical iterations. The LBT method derivations are compared with existing averaged and inaccurate methods and are also validated by simulations and experimental results.