A motor drive circuit for a rail vehicle has a step-up converter, which is disposed at the input of the motor drive circuit, and which converts a mains DC voltage, at the input of the motor drive circuit into an intermediate circuit DC voltage. A pulse rectifier, which is downstream from the step-up converter, can be connected at the output to a drive motor of the rail vehicle and it is capable of converting the intermediate circuit DC voltage of the step-up converter into a motor drive voltage for driving the drive motor. A control unit activates the step-up converter in operation such that the converter generates the predetermined rated intermediate circuit DC voltage for a mains DC voltage below a predetermined rated intermediate circuit DC voltage as the intermediate circuit DC voltage. The control unit is designed such that it activates the step-up converter for a mains DC voltage above the rated intermediate circuit DC voltage such that the converter generates an intermediate circuit DC voltage identical to the mains DC voltage or an intermediate circuit DC voltage, which is greater at most by a predetermined offset value, and feeds the intermediate circuit DC voltage into the pulse rectifier.