A variable step-down converter, comprising - a voltage output, - at least one first controllable voltage converter having a first voltage input and a first switch, - at least one first secondary winding connected to the first voltage input, - a first controller of the controllable voltage converter, including -- detecting an actual voltage and an actual current at the voltage output of the variable step-down converter, -- retrieving a target voltage, and -- outputting a first control signal for equalizing the actual voltage to the target voltage to the switch of the controllable voltage converter, characterized in - an even number of n second voltage converters in the form of not controllable voltage converters (5, 5') each having a second voltage input (22, 22') and a second switch (32, 32'), - second secondary windings wherein each second secondary winding is connected with each one of the second voltage inputs via a pulse rectifier and each of the second secondary windings is part of a star or a delta connection, - a cascading of the first and second voltage converters (1, 5, 5'), wherein the cascading is provided with a cascading of the second voltage converters (5, 5') wherein the second voltage converters (5, 5') are assigned alternately star and delta connections, which in each case are connected with the voltage inputs (22, 22') of the second voltage converters (5, 5'), - a second controller for outputting the target voltage to the first controller and for outputting a set of n second control signals with one control signal for each of the second switches (32, 32'), wherein the set of n second control signals defines how many of the n second voltage converters (5, 5') with the at least one controllable voltage converter are connected in series with the voltage output of the variable step-down converter during the cascading with a series connection, - wherein two first secondary windings are provided, one of which being part of a star connection and one of which being part of a delta connection, wherein the first two secondary windings are connected to the first voltage input via a series connection of two further pulse rectifiers. - a voltage output, - at least one first controllable voltage converter having a first voltage input and a first switch, - at least one first secondary winding connected to the first voltage input, - a first controller of the controllable voltage converter, including -- detecting an actual voltage and an actual current at the voltage output of the variable step-down converter, -- retrieving a target voltage, and -- outputting a first control signal for equalizing the actual voltage to the target voltage to the switch of the controllable voltage converter, characterized in -- detecting an actual voltage and an actual current at the voltage output of the variable step-down converter, -- retrieving a target voltage, and -- outputting a first control signal for equalizing the actual voltage to the target voltage to the switch of the controllable voltage converter, characterized in - an even number of n second voltage converters in the form of not controllable voltage converters (5, 5') each having a second voltage input (22, 22') and a second switch (32, 32'), - second secondary windings wherein each second secondary winding is connected with each one of the second voltage inputs via a pulse rectifier and each of the second secondary windings is part of a star or a delta connection, - a cascading of the first and second voltage converters (1, 5, 5'), wherein the cascading is provided with a cascading of the second voltage converters (5, 5') wherein the second voltage converters (5, 5') are assigned alternately star and delta connections, which in each case are connected with the voltage inputs (22, 22') of the second voltage converters (5, 5'), - a second controller for outputting the target voltage to the first controller and for outputting a set of n second control signals with one control signal for each of the second switches (32, 32'), wherein the set of n second control signals defines how many of the n second voltage converters (5, 5') with the at least one controllable voltage converter are connected in series with the voltage output of the variable step-down converter during the cascading with a series connection, - wherein two first secondary windings are provided, one of which being part of a star connection and one of which being part of a delta connection, wherein the first two secondary windings are connected to the first voltage input via a series connection of two further pulse rectifiers.