Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the record
Reexamination Certificate
1999-03-25
2001-09-04
Sniezek, Andrew L. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the record
C360S077080
Reexamination Certificate
active
06285521
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to reducing power consumed by disk drives. More particularly, the present invention relates to disk drives employing power source modulation for reducing power consumption, such as when the disk drive is idling.
2. Description of the Prior Art
In hard disk drives, data is stored on magnetic media disks in concentric data tracks, which are divided into groups of data sectors. Disks are typically stacked on a spindle assembly. The spindle assembly is mechanically coupled to a spindle motor which rotates the disks at a substantially constant operating spin-rate. A spindle motor driver typically includes power metal oxide semiconductor field effect transistors (MOSFETs) to drive the spindle motor. A microprocessor is typically employed to ascertain when to apply a run signal, a coast signal, or a brake signal to the spindle motor driver to control the operation of the spindle motor.
The torque developed (T
d
) by the spindle motor is given by the following Equation I:
T
d
=Kt*I
m
Equation I
Where:
Kt is the torque constant of spindle motor;
I
m
is spindle motor current;
Power dissipation in the windings of the spindle motor are given by the following Equation II:
P=I
m
2
*R
m
Equation II
where:
R
m
is the total resistance of the spindle motor and wire connections between the spindle motor and the power MOSFETs.
Power dissipation in the power MOSFETs are given by the following Equation III:
P=I
m
2
*R
fet
Equation III
where:
R
fet
is the resistance in the power MOSFETs that are turned on for controlling current Im flowing through the spindle motor.
It is known to increase the RPM of the spindle motor to reduce rotational latency and increase disk transfer rate in the disk drive. However, as disk drives employ spindle motors operating at higher RPMs (such as 10,000 RPMs and higher), it is necessary to offset increased drag torque opposing the developed torque T
d
in order to maintain the spindle motor at a substantially constant operating spin-rate. As can be shown by Equations I-III above, an increased developed torque T
d
required to off-set the increased drag torque to maintain the higher operating spin-rate of the spindle motor can be obtained by increasing the spindle motor current I
m
. Unfortunately, increasing the spindle motor current I
m
causes a corresponding heating of the windings of the spindle motor as shown by the above power dissipation Equation II and also a corresponding heating of the power MOSFETs used to drive the spindle motor as shown by the above Equation M. The additional heat generated by the disk drive can cause heat related breakdown of components in the disk drive, including the spindle motor windings and the power MOSFETs themselves.
In addition, power supplies in high performance computer systems which employ disk drives having spindle motors operating at high RPMs typically limit the average current output from the computer system's power supply circuitry to reduce the cost of the computer system. An increased spindle motor current I
m
necessary to maintain the higher operating spin-rate may cause an average spindle motor current to exceed the average current output from the computer system's power supply.
It is known to employ a power saving operation to reduce power consumption when the disk drive is idling during an idle period (i.e., no read or write operations are being performed). A power saving operation may include parking the head and spinning-down the disk drive to a stop during the idle period. U.S. Pat. No. 5,412,519 (the “Buettner patent”) discloses a power saving operation that spins down the spindle motor to the minimum rotational velocity that is required for the head to continue flying above the disk during the idle period. A disadvantage with such power saving operations is that there is a significant recovery time to resume read and write operations after the idle period.
For reasons stated above, there is a need to reduce power consumption in the spindle motor and its power MOSFETs, especially in high performance disk drives operating at 10,000 RPMs and higher. In addition, there is a need to reduce the power consumption in the spindle motor and its power MOSFETs without significantly increasing the recovery time to resume read and write operations after an idle period.
SUMMARY OF THE INVENTION
The invention can be regarded as a disk drive comprising a disk including a recording surface having a plurality of data tracks. Each data track has servo sectors and data regions disposed between the servo sectors. The servo sectors include servo information. The disk drive includes transducer means for writing and reading from the data regions and reading servo information from the servo sectors. The disk drive further includes a spindle motor and a spindle motor driver. The spindle motor is coupled to the disk to rotate the disk. The spindle motor driver selectively provides current to the spindle motor. The disk drive includes track-following control means responsive to the servo information for causing the transducer means to remain on track. The disk drive further includes programmable means for performing a power-saving idle operation of causing the spindle motor driver to sequentially (1) provide no current to the spindle motor for at least one disk revolution and (2) provide current to the spindle motor for at least one disk revolution. The power-saving idle operation is performed while the track-following control means causes the transducer means to remain on track for multiple disk revolutions.
The invention can also be regarded as a method of operating a disk drive comprising a disk including a recording surface having a plurality of data tracks. Each data track has servo sectors and data regions disposed between the servo sectors. The servo sectors include servo information. The disk drive includes transducer means for writing and reading from the data regions and reading servo information from the servo sectors. The disk drive includes a spindle motor coupled to the disk to rotate the disk, and a spindle motor driver for selectively providing current to the spindle motor. The method includes the step of maintaining the transducer means on track for multiple disk revolutions. While performing the step of maintaining the transducer means on track, the method includes sequentially (1) providing no current to the spindle motor for at least one disk revolution and (2) providing current to the spindle motor for at least one disk revolution.
The invention can also be regarded as a disk drive comprising a disk including a recording surface having a plurality of data tracks. Each data track has servo sectors and data regions disposed between the servo sectors. The servo sectors include servo information. The disk drive includes transducer means for writing and reading from the data regions and reading servo information from the servo sectors. The disk drive further includes a spindle motor having a plurality of windings. The spindle motor is coupled to the disk to rotate the disk. The disk drive includes a spindle motor driver having switching elements coupled to the plurality of windings for selectively providing current to the spindle motor. The disk drive includes track-following control means being responsive to the servo information for causing the transducer means to remain on track. The disk drive further includes programmable means for performing a power-saving idle operation of causing the spindle motor driver to sequentially (1) turn off all of the switching elements so that no current is provided to the spindle motor and (2) turn on selected ones of the switching elements to provide current to the spindle motor. The power-saving idle operation is performed while the track-following control means causes the transducer means to remain on track for multiple disk revolutions.
REFERENCES:
patent: 5412519 (1995-05-01), Buettner et al.
patent: 5706265 (1998-01-01)
Shara Milad G
Sniezek Andrew L.
Western Digital Technologies Inc.
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