Patent ID: RE44486

Claim:
A circuit apparatus for transformerless conversion of an electric direct voltage of a two-pole direct voltage source ( 1 ) connected to ground having a first voltage pole (+) and a second voltage pole (−) into an alternating voltage for feeding into an alternating voltage network, a DC-AC converter ( 400 ) for feeding into said alternating voltage network being connected downstream of a DC-DC converter ( 300 ) , and two first and second capacitors ( 41 , 42 ) being present in an intermediate circuit between said the DC-DC converter ( 300 ) and said the DC-AC converter ( 400 ) , said capacitors being connected in series and comprising a connection point (V) at ground potential so that a +/− voltage that is symmetrical with respect to ground potential ( 80 ) is available on the an output side of the DC-DC converter stage ( 300 ) , characterized in that there is provided comprising : a first inverting buck-boost chopper ( 100 ) that is connected in parallel with the direct voltage source ( 1 ) downstream thereof and that is connected such that it charges the first capacitor ( 41 ) ; and a second inverting buck-boost chopper ( 200 ) that is connected in parallel with said the first inverting buck-boost chopper ( 100 ) downstream thereof and is connected such that it the second inverting buck-boost chopper charges the second capacitor ( 42 ) , wherein the two first and second inverting buck-boost choppers ( 100 , 200 ) forming form the DC-DC converter ( 300 ) , wherein the first inverting buck-boost chopper ( 100 ) consisting of at least one comprises a first switch ( 11 ) , at least one a first diode ( 21 ) and at least one a first choke ( 31 ) , and wherein said second inverting buck-boost chopper ( 200 ) consisting of at least one comprises a second switch ( 12 ) , at least one a second diode ( 22 ) and at least one a second choke ( 32 ) .