Patent ID: 7120039

Claim:
A voltage conversion circuit for conversion of an input d.c. voltage (U E ) into a three-phase a.c. current (UR, US, UT) in a mains frequency range having at least one inductor (L 1 , L 2 ) and several switches (S 1 , . . . , S 9 ) controlled by a drive circuit (AST), comprising: a first converter section for producing positive output voltage portions and a second converter section for producing negative output voltage portions, and output of the first converter section via one of a plurality of first longitudinal phase circuit breakers (S 4 , S 5 , S 6 ) and output of the second converter section via one of a plurality of second longitudinal phase circuit breakers (S 7 , S 8 , S 9 ) are connected to produce three-phase current outputs (R, S, T), wherein: a ground pole (m) of the d.c. voltage (U E ) is directly connected to a PEN conductor (N) of the three-phase outputs, a first series connection of a first transverse switch (S 3 ) and a transverse inductor (L 2 ) is between a non-ground pole (p) of the d.c. voltage and ground, a junction point of the first series connection (S 3 , L 2 ) is connected via one of the second longitudinal phase circuit breakers (S 7 , S 8 , S 9 ) to the three-phase outputs (R, S, T), the non-ground pole (p) of the d.c. voltage is also connected in a second series connection via a longitudinal circuit breaker (S 1 ) and in series with it a longitudinal inductor (L 1 ) via one of the first longitudinal phase circuit breakers (S 4 , S 5 , S 6 ) so the three-phase outputs (R, S, T) and via a second transverse switch (S 2 ) to ground, and a junction point of the second series connection of the longitudinal circuit breaker (S 1 ) with the longitudinal inductor (L 1 ) is connected to ground via a diode (D 1 ) that is in the blocking direction in relation to the input voltage, the longitudinal inductor (L 1 ) together with the longitudinal circuit breaker (S 1 ) and the second transverse switch (S 2 ) and one of the first longitudinal phase circuit breakers (S 4 , S 5 , S 6 ) and diode (D 1 ) defining a step-up/step-down converter forming the first converter section (S 1 , D 1 , L 1 , S 2 ), and the second transverse inductor (L 2 ) together with the first transverse switch (S 3 ) and one of the second longitudinal phase circuit breakers (S 7 , S 8 , S 9 ) defining an inverting converter forming the second converter section (S 3 , L 2 ).