Disk drive employing method of spinning up spindle motor including detecting bemf polarity change for selecting initial commutation state

Abstract

A disk drive is connectable to a power supply voltage and includes a spindle motor, a spindle motor driver, a spindle motor controller, and a detector. The spindle motor has windings and a rotatable rotor. The spindle motor driver is connected to the windings and connectable to the voltage. The spindle motor controller commands the spindle motor driver to apply the voltage across at least one of the windings to cause the rotor to rotate, which induces a BEMF having a polarity across each of the windings. The spindle motor controller subsequently commands the spindle motor driver to remove the applied voltage across the windings, and the detector monitors the BEMF in each of the windings to detect the polarity of the BEMF in each of the windings to generate a previous multi-bit sequence representing a previous phase position ({circumflex over (&thgr;)} ) of the rotor and subsequently detect a change in the polarity of the BEMF in one of the windings to generate a present multi-bit sequence representing a present position (&thgr; ) of the rotor. The spindle motor controller is responsive to the previous phase position ({circumflex over (&thgr;)} ) and the present phase position (&thgr; ) of the rotor for selecting an initial commutation state for commanding the spindle motor driver to initiate a spin-up commutation sequence starting from the selected initial commutation state such that the voltage is sequentially applied across a selected combination of the windings in order to spin-up the spindle motor to an operating spin-rate.