Patent ID: 6710567
Filing Date: 2004-03-23
Classification: G11B

Abstract:
In a disc drive having a brushless direct current (dc) spindle motor which rotates a disc recording surface at an operational velocity during data transfer operations between the disc recording surface and a host device, the disc drive electrically commutating the spindle motor in response to detected back electromotive force (bemf) from the spindle motor during rotation, a method for accelerating the spindle motor from rest to the operational velocity comprising:initially accelerating the spindle motor from rest to an intermediate velocity at which sufficient bemf is generated by the rotation of the spindle motor to enable commutation circuitry of the disc drive to time the application of drive pulses to the spindle motor; and subsequently accelerating the spindle motor from the intermediate velocity to the operational velocity by applying a velocity dependent reference profile which establishes a sequence of reference levels to control the flow of current through the spindle motor during acceleration, the sequence of reference levels having different magnitudes at different velocities of the spindle motor between the intermediate velocity and the operational velocity.