Abstract:
A power loss retraction architecture is provided to retract the VCM arm of a hard disk drive upon power loss. The power loss retraction architecture is configurable to be able to use energy from different sources. The selected energy source is used efficiently by applying the energy only to the VCM retract arrangement, while isolating the energy source from other circuits that are not needed to accomplish the retraction operation.

Description:
This application claims the priority under 35 U.S.C. §119(e) of co-pending U.S. Provisional Application No. 60/525,476, filed on Nov. 26, 2003 and incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates generally to hard disk drives, and more particularly, to control of the read/write head in a hard disk drive. 
   BACKGROUND OF THE INVENTION 
   A hard disk drive includes a disk on which data is stored, a spindle motor which rotates the disk, a read/write head, and a voice coil motor (VCM) to move the head over the disk for reading/writing from/to the disk surface. When the disk is not rotating, the VCM moves the head away from the disk area. When the disk is rotating, and read/write operations are in progress, the head, which is carried on a VCM arm, is positioned above the data storage surface of the disk. When the disk is not rotating, the head is moved away from the disk in order to prevent any damage to the disk. When power loss (any power supply inactivation such as a power failure event or a power-down event) occurs, the disk will slow down and eventually stop due to its inertia. Whether the power loss is due to a power failure or a power-down event, there are several known ways to obtain energy for moving the head to a safety zone away from the disk. This movement of the head to a safety zone is also often referred to as “parking the VCM arm”. 
   One conventional source of energy for retracting the read/write head away from the disk is the spindle motor, which generates energy as it slows down but nevertheless continues to rotate for a period of time. This is illustrated in  FIG. 1 . The voltage VM generated by the slowing-down spindle motor produces a current  11  that passes through the VCM  13 , to effect retraction of the read/write head. 
   Another known source of energy for retracting the read/write head is a storage capacitor C 0  connected as shown in  FIG. 2 . Energy is stored in the capacitor C 0  while the power supply is present during normal operation, and this stored energy is used to retract the read/write head after a power loss event. In particular, the capacitor voltage VM 2  produces a current  21  which passes through the VCM  13  to effect retraction of the read/write head. 
   Another known scheme uses a capacitor in combination with a boost circuit such as shown in  FIG. 3 . The boost circuit  30 , for example a charge pump, operates to boost the capacitor voltage to a level that is higher than the nominal power supply voltage VCC. As shown in  FIG. 3 , the boosted voltage arrangement requires an additional switching device, namely FET M 11 , for directing through the VCM  13  a current  31  produced by the boosted capacitor voltage VBOOST. 
   In any of the prior art approaches of  FIGS. 1–3 , the amount of energy available for moving the read/write head after a power loss event is limited. Accordingly, the present invention recognizes that the effectiveness of the power loss head retraction scheme depends on how efficiently the retraction energy source is utilized. That is, in order to provide for a reliably effective power loss retraction operation, the retraction energy source must be used efficiently. 
   It is therefore desirable to provide for a power loss head retraction architecture which uses the available retraction energy source more efficiently than the prior art approaches. 
   SUMMARY OF THE INVENTION 
   Exemplary embodiments of the invention operate during a power loss event to isolate the head retraction energy source from portions of the hard disk drive that are not needed to accomplish the retraction. This provides for an efficient use of the energy source. 
   The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art will appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form. (STMI) 
   Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words or phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, whether such a device is implemented in hardware, firmware, software or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior uses, as well as to future uses, of such defined words and phrases. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, wherein like numbers designate like objects, and in which: 
       FIG. 1  illustrates the use of spindle motor energy to retract the read/write head according to the prior art. 
       FIG. 2  illustrates the use of a storage capacitor to provide energy for retracting the read/write head according to the prior art. 
       FIG. 3  illustrates the use of a storage capacitor combined with a boost circuit as an energy source for retracting the read/write head according to the prior art. 
       FIG. 4  diagrammatically illustrates exemplary embodiments of a power loss retraction architecture according to the invention which uses spindle motor energy. 
       FIG. 5  diagrammatically illustrates exemplary embodiments of a power loss retraction architecture according to the invention which uses energy stored in a capacitor. 
       FIG. 6  diagrammatically illustrates exemplary embodiments of a power loss retraction architecture according to the invention which uses energy from a boost circuit-capacitor combination. 
       FIG. 7  diagrammatically illustrates a configurable, multi-mode power loss retraction architecture which is cooperable with any of the power loss retraction energy sources described above with respect to  FIGS. 4–6 . 
       FIG. 8  diagrammatically illustrates exemplary embodiments of a data processing apparatus including a hard disk drive having a power loss retraction architecture according to the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The figures and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. 
   Exemplary embodiments of the invention provide for a more efficient use of the energy source for power loss read/write head retraction by isolating that energy source from other circuitry in the hard disk drive. More specifically, during power loss retraction operation, exemplary embodiments isolate the retraction energy source from those portions of the hard disk drive that are not necessary for the retraction operation. In this manner, the retraction energy source is efficiently used to power the retraction operation and is not drained by circuitry that is not used to perform the retraction operation. 
     FIG. 4  diagrammatically illustrates exemplary embodiments of the invention wherein the spindle motor provides power to retract the read/write head when a power loss event occurs. The example of  FIG. 4  includes six spindle motor drivers M 0 –M 5 , and four VCM drivers M 7 –M 10 . When a power loss event occurs, the spindle motor, as it winds down, provides power to the VCM in generally similar fashion to  FIG. 1  above. However, in the example of  FIG. 4 , an isolation device M 6  (also designated as ISO-FET) is provided to isolate the spindle motor and associated drivers M 0 –M 5  from other circuitry  41 . The other circuitry  41  is powered by the normal power supply VCC, but is unrelated to the read/write head retraction operation. Accordingly, by isolating the spindle motor arrangement from the other circuitry  41 , the energy provided by the spindle motor arrangement can be efficiently supplied to the VCM  13  to power the retraction operation, and the other circuitry  41  does not drain energy from the spindle motor arrangement. When a power loss event occurs, VCC is effectively inactivated, so the isolation device M 6  (for example a MOSFET) is turned off because VCC is less than the spindle motor voltage VM. This places the effective diode of M 6  into reverse bias, thereby isolating the other circuitry  41  from the spindle motor arrangement and the VCM arrangement. 
     FIG. 5  diagrammatically illustrates exemplary embodiments of the invention wherein power loss retraction energy is provided by a capacitor C 0 . In  FIG. 5 , the power loss retraction energy is provided by the storage capacitor C 0  in generally similar fashion to  FIG. 2  above, but the isolation device M 6  isolates the spindle motor arrangement and the other circuitry  41  from the capacitor C 0  and the VCM arrangement. Again, when a power loss event occurs, VCC becomes less than the capacitor voltage VM 2 , so the isolation FET M 6  is turned off, thereby isolating the capacitor C 0  and the VCM arrangement from the remainder of the circuitry. 
     FIG. 6  diagrammatically illustrates exemplary embodiments of the invention wherein a boost circuit-capacitor combination provides power loss retraction energy. In  FIG. 6 , the combination of the boost circuit  30  and the capacitor C 0  provides power loss retraction energy in generally similar fashion to  FIG. 3  above. However, when a power loss event occurs, the isolation device M 6  turns off, thereby isolating the VCM current path from the remainder of the circuitry of the hard disk drive apparatus. In some exemplary embodiments, the boost circuit  30  is a charge pump. 
     FIG. 7  diagrammatically illustrates a configurable, multi-mode power loss retraction architecture which is cooperable with any of the power loss retraction energy sources described above with respect to  FIGS. 4–6 . In the architecture of  FIG. 7 , isolation devices (ISO)  4 ,  5  and  6  are connected in generally the same fashion as the isolation devices in  FIGS. 4 ,  5  and  6 , respectively. The architecture of  FIG. 7  can be selectively configured to cooperate with any selected one of the power loss retraction energy sources of  FIGS. 4–6 . More particularly, in the integrated circuit which implements drivers M 0 –M 5 , M 7 –M 10  and isolation devices  4 – 6 , the nodes designated at  71 – 75  are physically accessible at the externally available pins of the integrated circuit. The proper isolation device is selected based upon which power loss retraction energy source is to be used, and the other two isolation devices can then be shunted out of the circuit. 
   For example, if the spindle motor is to be used as the power loss retraction energy source, then the externally accessible nodes  72  and  73  are shorted together and the externally accessible nodes  74  and  75  are shorted together, thereby eliminating isolation devices  5  and  6  from the circuit, which results in the arrangement of  FIG. 4 . Similarly, if the capacitor C 0  of  FIG. 5  is to be used as the power loss retraction energy source, then externally accessible nodes  71  and  72  are shorted together, and externally accessible nodes  74  and  75  are shorted together, thereby eliminating isolation devices  4  and  6  from the circuit, which results in the arrangement of  FIG. 5 . Finally, if the boost circuit-capacitor combination of  FIG. 6  is to be used as the power loss retraction energy source, then externally available nodes  71 ,  72  and  73  are all shorted together, thereby eliminating isolation devices  4  and  5  from the circuit, which results in the arrangement of  FIG. 6 . In some exemplary embodiments, the isolation devices  4 – 6  are MOSFETs such as M 6  of  FIGS. 4–6 . 
     FIG. 8  diagrammatically illustrates exemplary embodiments of a data processing apparatus according to the invention. The apparatus of  FIG. 8  includes a hard disk drive  80  which includes a ramp  14  arranged outside and near a storage disk  110 . During the retraction operation, the VCM arm  130  rotates about shaft  170  and retracts the read/write head  12  away from the disk  110 . A tab  132  slides onto the ramp  14  to position the read/write head  12  in a non-contacting state with respect to the disk  110 . In various exemplary embodiments, the hard disk drive  80  can include the various power loss head retraction arrangements described above with respect to  FIGS. 4–7 . A data processing portion (e.g., a microprocessor device or microprocessor-based circuit)  81  is coupled to the hard disk drive  80  for permitting the data processing portion  81  to store data onto and retrieve data from the data storage disk  110 . A user interface  82  is coupled to the data processing portion  81  for permitting communication between the data processing portion  81  and a user. In some embodiments, the user interface can include one or more of a tactile interface, a visual interface and an audio interface. The data processing system of  FIG. 8  can be, in some exemplary embodiments, a desktop computer, a notebook computer, a personal digital assistant (PDA), or a digital camera. 
   Although the present invention has been described in detail, those skilled in the art will understand that various changes, substitutions, and alterations herein may be made without departing from the spirit and scope of the invention it its broadest form.