RIPPLE EXTRACTION DEVICE, MOTOR CONTROL APPARATUS, VEHICLE SEAT, AND RIPPLE EXTRACTION METHOD

A ripple extraction device (3) extracts ripple components contained in a current signal of a motor (2). The ripple extraction device (3) is provided with; a current-voltage converter (10) that converts a current signal of the motor (2) into a voltage signal; a filter (40) that filters the voltage signal converted by the current-voltage converter (10), and attenuates the ripple components; and a differential amplifier ( 5 0) that obtains the difference between the voltage signal converted by the current-voltage converter (10) and an output signal of the filter (40).