Disk drive head retract and motor braking method and apparatus

Abstract

One phase of a multi-phase spindle motor, normally used to rotate the disk of a disk drive system when power is on, is used to supply power to a capacitor storage circuit when power is lost (turned off or otherwise interrupted). The capacitor storage circuit provides the power to the retract circuit, which retracts the head. The combination of the generator effect of the phase and the capacitor storage circuit provides power to the retract circuit for a time clearly sufficient to reliably retract and lock the head regardless of the bias of the head prior to power loss. Simultaneously with one phase being used to retract the head, the other phases are shorted together to provide regenerative braking. FET drivers, normally used to drive the spindle motor when power is supplied, are used to short out the remaining phases to brake the motor when power is lost. In the preferred embodiment, the capacitor storage circuit is used as a line filter circuit when power is on. Therefore, the major circuit components used for retracting the head and braking the motor upon loss of power (capacitor storage circuit, motor windings, FET drivers) are all used for different purposes when power is on. This efficient use of the same circuitry for multiple purposes results in an efficient, reliable, compact, and relatively inexpensive approach for disk drive head retract and motor braking upon loss of power.