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Dynamical Profile of SwitchedMode Converter Fact or Fiction?
Tiivistelmä:
The existence of the dynamical profile, for the voltageoutput converters, is demonstrated by developing the profile for a buck converter with different control principles. Operations in discontinuous and continuous conduction modes are also discussed. It is noticed that the control method and operation mode strongly affect the dynamical properties. It is verified both analytically and experimentally that these properties can be easily deduced by studying the parameters of the profile. The dynamical profile for the currentoutput converters is also proposed. The profile can be derived by using conventional modeling methods or from the corresponding voltageoutputconverter profile by applying duality. It is discovered that the dynamics of a currentoutput converter are totally different than in the corresponding voltageoutput converter. The prevailing assumption has been that the currentoutput converter has a peculiar characteristic of increased gain crossover frequency, when using a low impedance load. This phenomenon is addressed to be due to a wrong control design and the use of a resistive load as the initial load.
The prevailing method seems to be to use the resistive load in modeling and analyzing switchedmode converters. However, the true nominal load for the voltageoutput converter is a constant current sink and for the currentoutput converter a pure voltage source. Illustrative examples are provided, which explicitly show the adverse effect of the resistive load hiding the real dynamical profile.
As a conclusion, the introduced concept of the dynamical profile provides valuable tool and framework in analyzing and ensuring the performance and stability of a switchedmode converter, or any electrical device, as a part of a larger system. Its use can significantly save the design and prototype testing times and peculiar phenomena can usually be avoided. Several examples and aspects presented in the thesis explicitly prove that the unique dynamical profile of any given converter is a fact not a fiction.