Exact Analysis of a Control-to-Output Transfer Function of PWM-Converters - A Comparison of Two Methods

Abstract:
Generally, the design of control loops for power converters requires a transfer function. Commonly, averaging models are used to approximately describe the small signal behavior. This paper compares two alternative methods based on time discrete modeling, resulting in an exact prediction. Two perturbation methods will be explained and discussed with their advantages and disadvantages. The new methods are exemplarily demonstrated for a boost-converter. The paper reveals that with a typical design averaging methods correspond to the proposed exact methods. Furthermore, for critical designs given in literature, the exact methods predict the correct result, in contrast to the averaging method.