Patent ID: 7616467

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 capacitors ( 41 , 42 ) being present in an intermediate circuit between said DC-DC converter ( 300 ) and said 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 output side of the DC-DC converter stage ( 300 ), characterized in that there is provided: 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 first buck-boost chopper ( 100 ) downstream thereof and is connected such that it charges the second capacitor ( 42 ), the two buck-boost choppers ( 100 , 200 ) forming the DC-DC converter ( 300 ), the first buck-boost chopper ( 100 ) consisting of at least one first switch ( 11 ), at least one first diode ( 21 ) and at least one first choke ( 31 ), said second buck-boost chopper ( 200 ) consisting of at least one second switch ( 12 ), at least one second diode ( 22 ) and at least one second choke ( 32 ).