Disk drive increasing laser power at beginning of write in heat assisted magnetic recording
View Patent ↗A disk drive is disclosed comprising a disk comprising a plurality of data tracks, wherein each data track comprises a plurality of data sectors. A head is actuated over the disk, wherein the head comprises a laser operable to heat the disk while writing data to the disk. When a write command is received to write data to a target data sector of a target data track, the head is positioned over the target data track. When the head reaches the target data sector, a power applied to the laser is increased to above a steady state value to compensate for a high fly height of the head. The power applied to the laser is decreased toward the steady state value while writing at least part of the data to the target data sector.
1. A disk drive comprising:
a disk comprising a plurality of data tracks, wherein each data track comprises a plurality of data sectors;
a head actuated over the disk, wherein the head comprises a laser operable to heat the disk while writing data to the disk; and
control circuitry operable to:
receive a write command to write data to a target data sector of a target data track;
position the head over the target data track;
when the head reaches the target data sector, increase a power applied to the laser to above a steady state value to compensate for a high fly height of the head; and
decrease the power applied to the laser toward the steady state value while writing at least part of the data to the target data sector.
2. The disk drive as recited in claim 1 , wherein the power applied to the laser is decreased as the fly height decreases.
3. The disk drive as recited in claim 1 , wherein the control circuitry is operable to decrease the power applied to the laser based on at least one exponential function that establishes a time constant for the decreasing power.
4. The disk drive as recited in claim 3 , wherein the control circuitry is operable to adjust at least one parameter of the exponential function in order to adjust the time constant.
5. The disk drive as recited in claim 1 , wherein the control circuitry is operable to begin writing the data to the target data sector substantially simultaneous with increasing the power applied to the laser.
6. The disk drive as recited in claim 1 , wherein the control circuitry is operable to delay writing the data to the target data sector after increasing the power applied to the laser.
7. The disk drive as recited in claim 1 , wherein the control circuitry is operable to increase the power applied to the laser to a level based on an interval between consecutive writes to the disk.
8. The disk drive as recited in claim 7 , wherein the interval corresponds to a time needed to read a servo sector during a write operation.
9. The disk drive as recited in claim 7 , wherein the interval corresponds to a gap between consecutive data sectors during a write operation.
10. The disk drive as recited in claim 7 , wherein the control circuitry is operable to select the level based on at least one exponential function having the interval as a parameter of the function.
11. A method of operating a disk drive, the disk drive comprising a disk comprising a plurality of data tracks, wherein each data track comprises a plurality of data sectors, and a head actuated over the disk, wherein the head comprises a laser operable to heat the disk while writing data to the disk, the method comprising:
receiving a write command to write data to a target data sector of a target data track;
positioning the head over the target data track;
when the head reaches the target data sector, increasing a power applied to the laser to above a steady state value to compensate for a high fly height of the head; and
decreasing the power applied to the laser toward the steady state value while writing at least part of the data to the target data sector.
12. The method as recited in claim 11 , further comprising decreasing the power applied to the laser as the fly height decreases.
13. The method as recited in claim 11 , further comprising decreasing the power applied to the laser based on at least one exponential function that establishes a time constant for the decreasing power.
14. The method as recited in claim 13 , further comprising adjusting at least one parameter of the exponential function in order to adjust the time constant.
15. The method as recited in claim 11 , further comprising beginning the writing of the data to the target data sector substantially simultaneous with increasing the power applied to the laser.
16. The method as recited in claim 11 , further comprising delaying the writing of the data to the target data sector after increasing the power applied to the laser.
17. The method as recited in claim 11 , further comprising increasing the power applied to the laser to a level based on an interval between consecutive writes to the disk.
18. The method as recited in claim 17 , wherein the interval corresponds to a time needed to read a servo sector during a write operation.
19. The method as recited in claim 17 , wherein the interval corresponds to a gap between consecutive data sectors during a write operation.
20. The method as recited in claim 17 , further comprising selecting the level based on at least one exponential function having the interval as a parameter of the function.