Capacitorless DC-DC Regulator as a Candidate Topology for Photovoltaic Solar Facilities

Abstract

Linear-assisted   DC/DC   converters   (or   linear-switching  hybrid  DC/DC  converters)  consist  of  a  voltage  linear  regulator (classic NPN or nMOS topologies and LDO) connected in  parallel  with  a  switching  DC/DC  converter.  They  are  a  good  candidate for energy processing in photovoltaic solar facilities. In order to control these hybrid structures, different strategies exist, allowing  fixing  the  switching  frequency  as  a  function  of  some  parameters  of  the  linear  regulator.  This  article  compares  two  control  strategies  that,  although  can  be  applied  to  the  same  circuital   structure   of   linear-assisted   converter,   are   sensibly   different.  The  first  one,  reported  in  previous  literature,  cancels  completely  the  average  current  through  the  linear  regulator  in  steady  state  to  achieve  a  reduction  of  the  losses.  Thus  the  efficiency  of  the  whole  system  increases  and  almost  equals  the  one   of   the   standalone   switching   converter.   The   proposed   approach,  in  spite  of  a  slightly  increment  of  linear  regulator’s  losses, reduces the output ripple due to the crossover distortion of linear regulator output stage.