Patent ID: 7042672
Filing Date: 2006-05-09
Classification: G11B

Abstract:
1. A control device for controlling current through a voice coil motor (VCM) during retraction of a transducing head from the surface of a recordable medium, the transducing head carried on a movable member actuated by the VCM, the control device comprising: a measuring circuit for determining an average back electromotive force (back EMF) from the VCM by measuring the back EMF a plurality of times and averaging the measured back EMF, wherein the average back EMF from the VCM is related to a velocity of the movable member; a driver circuit connected to the VCM for providing the VCM with a drive current having a magnitude based on the average back EMF from the VCM; and switching circuitry that aperiodically and alternately enables the measuring circuit and the driver circuit.