Dissertação
Análise estática normalizada e modelagem de pequenos sinais do conversor classe-e utilizando transformadores piezoelétricos
Fecha
2011-08-04Registro en:
ENGLEITNER, Raffael. Análise estática normalizada e modelagem de pequenos sinais do conversor classe-e utilizando transformadores piezoelétricos.. 2011. 149 f. Dissertação (Mestrado em Engenharia Elétrica) - Universidade Federal de Santa Maria, Santa Maria, 2011.
Autor
Engleitner, Raffael
Institución
Resumen
Piezoelectric transformers (PTs) allow the design of promising power supply applications, increasing
efficiency, reducing size, facilitating the achievement of high transformation ratio, besides providing
high immunity against electromagnetic noise. Due to the electrical equivalent model having resonant
characteristics, some resonant topologies are naturally suitable for these power supplies, i.e. the Class-
E, Half-Bridge, Full-Bridge and Push-pull. Among these topologies, the Class-E converter has a
highlight of having one controlled switch. The static gain of the Class-E is changed through the
switching frequency variation, while the duty cycle is adjusted with the purpose of achieving soft
switching for different switching frequencies and loads. The analisys of this process becomes complex
when the system has a high number of reactive elements. One way to simplify this analisys is applying
a normalized methodology. On this regard, the first result of this work is the normalized analisys of
the functionally of the Class-E converter, including normalized load and switching frequency
variation. This allows choosing one optimum point for the static design, without the necessity of
design parameters. The main objective of this analisys is the obtention of the duty cycle behavior in
order to have soft switching for all operation points. In a second moment, a small-signal model was
derived using the generalized averaging method, through Fourier series aproximation. The model
describes the relevant poles and zeros of the system, being accurate enough for different loads and
switching frequencies. The behavior of resonant converters changes considerably for different
operating points; therefore it is important to have a model that represents the system well. The
normalized analisys allowed simplifying the small-signal model derivation, once soft switching is
achieved for all the operation points. Experimental measurements validate either the normalized or the
small signal derivation methodologies. The measurements were achieved for a 3W step-down
converter, with universal 85-265 V AC input and 6 V DC output.