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Visok izkoristek in zmanjšanje dimenzij stikalnih pretvornikov sta ključni zahtevi pri načrtovanju pretvornikov napetosti, saj je vse več električnih naprav, ki se napajajo iz baterij. Zmanjšanje dimenzij je pogojeno predvsem z zvišanjem preklopne frekvence. S tem pa se manjša izkoristek pretvornika, saj se z višanjem stikalne frekvence višajo tudi preklopne izgube na tranzistorjih. V delu je predstavljen način vklapljanja tranzistorjev pri ničelni napetosti, kar omogoča, da se vklop tranzistorja izvrši z mnogo manjšo izgubno močjo. S tem se pri zvišanju preklopne frekvence izkoristek pretvornika ohrani dovolj visoko. Predstavljen je tudi način reguliranja pretvornika navzdol, s pravilnim izračunom želene stikalne frekvence in negativne vrednosti toka dušilke, ki pogojuje mehak vklop zgornjega tranzistorja v pretvorniku navzdol. Pretvornik deluje v »kvazi« trganem režimu in izkorišča medelektrodne izhodne kapacitivnosti MOSFET tranzistorjev. Podane so izpeljave, s katerimi izračunamo veličine pomembne za regulacijo pretvornika. Rezultati so preverjeni v simulacijskem programu LtSpice in na realnem šolskem modelu pretvornika. Regulacija šolskega pretvornika je izvedena z DSP krmilnikom proizvajalca Texas Instrument. Achieving high efficiency and reducing the dimensions of switching inverters are key requirements in designing voltage converters as more and more electric devices are being supplied from batteries. The reduction in dimensions is possible with increased switching frequency. As the switching frequency increases, the switching losses of transistors also increase. This reduces the efficiency of converters. In this section, the method of switching the transistors at zero voltage is presented, which enables the transistor to be turned on without loss of power. This results in increased efficiency of the converter at increased switching frequency. In this paper is presented the regulation of buck converter, which enables zero voltage switching and does not require additional changes in the circuit (adding elements). The converter operates in the "quasi-" discontinued current mode and exploits the interelectrode output capacitance of the MOSFET transistors. Equations relevant to the regulation of converter are also presented. The results of the regulation using these equations are verified in the LtSpice simulation program and on the real school model of buck converter. School converter was controlled with the DSP controller manufactured by Texas Instrument. |
