Patent ID: 8453814

Claim:
A motor drive circuit for a rail vehicle, comprising: an input for receiving a power supply system DC voltage; a step-up converter connected at said input of the motor drive circuit and configured to convert the power supply system DC voltage at said input to an intermediate-circuit DC voltage, wherein said intermediate-circuit DC voltage is equal to or greater than the power supply system DC voltage, and wherein said step-up converter is a DC-DC converter; a pulse-controlled inverter having an input connected to an output of said step-up converter and an output to be connected to a drive motor for the rail vehicle, said pulse-controlled inverter being configured for converting the intermediate-circuit DC voltage of said step-up converter to a motor drive voltage for driving the drive motor; and a control device connected to drive said step-up converter in operation, wherein: in case the power supply system DC voltage lies below a rated intermediate-circuit DC voltage, said control device drives said step-up converter to produce the predetermined rated intermediate-circuit DC voltage as the intermediate-circuit DC voltage; and in case the power supply system DC voltage lies above the rated intermediate-circuit DC voltage, said control device drives said step-up converter to produce an intermediate-circuit DC voltage identical to the power supply system DC voltage, or to output an intermediate-circuit DC voltage that is greater than the power supply system DC voltage at most by a predetermined offset value; and the intermediate-circuit DC voltage is output to said pulse-controlled inverter.