Low cost emergency disk drive head retract architecture

Abstract

A disk drive emergency retract architecture for providing power to a voice coil motor (VCM) to retract a transducing head from a surface of a recordable medium during loss of power from an external power supply. The disk drive emergency retract architecture comprises a spindle motor, having an internal inductance and an internal resistance, for spinning the recordable medium. The spinning recordable medium creates a back electromotive force (BEMF) in the spindle motor. A boost circuit transfers the back electromotive force located in the spindle motor to a capacitor which stores and supplies power to the VCM. The capacitor is connected to a power switch circuit, which supplies power from the capacitor to the VCM when the power switch circuit is in a conducting state and prevents power from being supplied to by the capacitor to the VCM when the power switch circuit is in a non-conducting state. A retract circuit supplies a signal to the power switch circuit, dictating whether the power switch circuit is in the conducting state or the non-conducting state. The retract circuit operates to alternate the power switch circuit between the conducting state and the non-conducting state at a set frequency, resulting in power being provided from the capacitor to the VCM at this frequency.