Low cost emergency disk drive head retract architecture

A method for retracting a read/write head during emergency loss of power, the method comprising:

• creating a first current path such that energy associated with a back electromotive force (BEMF) created in a spindle motor by the inertia of a spinning disk is transferred only to an internal inductance within the spindle motor;
• creating a second current path such that energy transferred to the internal inductance of the spindle motor is transferred to a capacitor, wherein the internal inductance of the spindle motor provides a charging voltage to the capacitor greater than a voltage provided by the BEMF;
• supplying energy stored in the capacitor to a power switch circuit, wherein the power switch circuit operates to supply power to a retract motor when the power switch circuit is in a conducting state, and prevents power from being supplied by the capacitor when the power switch circuit is in a non-conducting state;
• and
• driving the retract motor by alternating the power switch circuit between the conducting state and the non-conducting state.

A emergency retract architecture for retracting a transducing head from a disk to a safe landing zone during emergency loss of power, the emergency retract architecture comprising:

• a voice coil motor (VCM) for retracting the transducing head when power is supplied to the VCM;
• a three phase electric motor for spinning the disk, wherein the spinning disk creates a three phase back electromotive force in the electric motor and wherein the electric motor further comprises an internal inductance;
• a capacitor coupled to the electric motor;
• a power switch circuit, wherein the power switch circuit operates to supply power from the capacitor to the VCM when the power switch circuit is in a conducting state and prevents power from being supplied by the capacitor when the power switch circuit is in a non-conducting state;
• at least one switching circuit having a conducting state and a non-conducting state;
• and
• a control circuit connected to the at least one switching circuit and to the power switch circuit, wherein the control circuit places the at least one switching circuit in the conducting state, causing current to build up only in the internal inductance of the electric motor and wherein the control circuit places the at least one switching circuit to the non-conducting state, causing current to be drawn from the internal inductance of the electric motor to the capacitor, and wherein the control circuit further operates to alternately place the power switch circuit between the conducting state and the non-conducting state at a given frequency, such that power stored in the capacitor is supplied to the VCM at the frequency dictated by the control circuit.

A disk drive emergency retract architecture for providing power to a voice coil motor (VCM) from a back electromotive force (BEMF) generated in a spindle motor 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 comprising:

• a capacitor for storing and supplying power to the VCM;
• a switching circuit connected to the spindle motor, wherein the switching circuit causes only an internal inductance of the spindle motor to store the BEMF when in a first state and causes energy stored in the internal inductance of the spindle motor to be transferred to the capacitor when in a second state;
• and
• a logic circuit connected to selectively control the state of the switching circuit such that the capacitor is charged to a voltage level greater than a voltage provided by the BEMF.