Patent ID: 7622985

Claim:
An active compensation filter for the application in the electric power supply in a land vehicle, with the compensation filter comprising: a high-pass filter which is to coupled with a supply voltage line which carries a supply voltage in order to detect frequency and amplitude of interference voltage components of the supply voltage, a signal amplifier connected in series with the high-pass filter, which amplifies the detected interference voltage components and supplies them as output signals to a coupling element which is connected in series with the signal amplifier and comprises a primary side and a secondary side, with the primary side being fed with the output signals of the signal amplifier and the secondary side being looped into the supply voltage line, characterised in that the coupling element comprises a transformer with at least three galvanically separated, magnetically coupled turns, with a tertiary winding being provided in a negative feedback path of the signal amplifier, and with the negative feedback path leading from an output of the signal amplifier to an input of the signal amplifier wherein a tap for interference voltage components downstream of the secondary winding of the coupling transformer in a negative feedback path leads to an input of the signal amplifier.