Patent ID: 7741796

Claim:
A method for controlling at least two brake resistors, each being connected in series with a respective one of a plurality of switches to be controlled, each of the at least two brake resistors and the respective one of the switches being connected between a positive and a negative rail of a direct current (DC) intermediate circuit, the method comprising: determining a magnitude of a voltage of a DC intermediate circuit in relation to a first voltage limit and a second voltage limit; and switching the brake resistors to the DC intermediate circuit in a periodically alternating manner by alternately switching each switch, during a switching period, between a respective off-period and an on-period of each switch when the magnitude of the voltage of the DC intermediate circuit is determined to be above the first voltage limit and below the second voltage limit, wherein the length of the respective on-period of each switch is based on the determined magnitude of the voltage of the DC intermediate circuit.