Patent ID: 8395280

Claim:
A circuit arrangement comprising a multi-level converter, the multi-level converter comprising: voltage supply terminals configured to provide an AC output voltage; at least two converter units, each converter unit comprising input terminals configured to have an electrical charge storage unit connected thereto, output terminals, and a switch arrangement connected between the input terminals and the output terminals, the switch arrangement being configured to receive a control signal, and being configured to provide an output voltage having a duty-cycle at the output terminals dependent on the control signal, the at least two converter units being connected in series with each other between the voltage supply terminals; and a control circuit configured to: provide a set of parameter sets, the set of parameter sets being dependent on a desired output voltage waveform, and at least one parameter set defining a fixed duty-cycle, wherein the at least one parameter set is assigned to a converter unit for a duration of at least one half-cycle of the AC output voltage, wherein the output voltage of each of the at least two converter units is a voltage that assumes a voltage amplitude level of one of two different voltage amplitude levels in accordance with the fixed duty cycle, generate the control signals for the at least two converter units such that one parameter set selected from the set of parameter sets is assigned to one converter unit, wherein the assignment of parameter sets to the converter units varies over time, detect a charge state of the charge storage units of the converter units, and assign the parameter sets to the converter units dependent on the detected charge states.