Method of operating hard disk drive, corresponding control circuit, hard disk drive and processing device
The disclosure relates to a voice coil motor (VCM) in a hard disk drive during a retract phase, wherein read-and-write heads of the hard disk drive are retracted by the VCM from a disk surface towards an end-of-travel parking condition with the heads climbing over a ramp starting from a ramp edge adjacent the disk surface. During the retract phase, the VCM is operated in a discontinuous mode comprising an alternation of on-times of duration TON and off-times of duration TOFF wherein supply of a drive current to the VCM is facilitated and countered, respectively. The duration TOFF of the off-times is varied to have a lower bound value at the ramp edge and to increase towards an upper bound value as the heads climb over the ramp towards the end-of-travel parking condition.
1 . A method, comprising:
operating a voice coil motor (VCM) in a hard disk drive during a retract phase in which read-and-write heads of the hard disk drive are retracted by the VCM from a disk surface towards an end-of-travel parking condition with the heads climbing over a ramp starting from a ramp edge adjacent the disk surface;
during the retract phase, operating the VCM in a discontinuous mode comprising an alternation of on-times of a duration TON and off-times of a duration TOFF in which supply of a drive current to the VCM is facilitated and countered, respectively; and
during the retract phase, varying the duration TOFF of the off-times, with the duration TOFF of the off-times increasing from a first lower bound value at the ramp edge towards a first upper bound value as the heads climb over the ramp.
2 . The method of claim 1 , wherein the duration TOFF of the off-times varies linearly from the first lower bound value towards the first upper bound value.
3 . The method of claim 1 , wherein the first lower bound value and the first upper bound value of the duration TOFF of the off-times are about 200 us and about 600 us, respectively.
4 . The method of claim 1 , further comprising varying the duration TON of the on-times with the duration TON of the on-times increasing from a second lower bound value at the ramp edge towards a second upper bound value as the heads climb over the ramp.
5 . The method of claim 4 , further comprising varying the duration TON of the on-times as a function of the duration TOFF of the off-times.
6 . The method of claim 5 , further comprising varying the duration TON of the on-times according to:
TON
=
K
1
*
TOFF
where:
K1 is a proportionality factor equal to 1.5 or 2.
7 . The method of claim 4 , wherein the second lower bound value and the second upper bound value of the duration TON of the on-times are about 400 us and about 1200 us, respectively.
8 . The method of claim 1 , further comprising controlling an intensity of the drive current through the VCM as a function of a back electromotive force of the VCM.
9 . A control circuit comprising:
retract logic circuitry configured to be coupled to a voice coil motor (VCM) in a hard disk drive, and configured to, during a retract phase:
operate the VCM to retract read-and-write heads of the hard disk drive from a disk surface towards an end-of-travel parking condition with the heads climbing over a ramp starting from a ramp edge adjacent the disk surface;
operate the VCM in a discontinuous mode comprising an alternation of on-times of a duration TON and off-times of a duration TOFF in which supply of a drive current to the VCM is facilitated and countered, respectively; and
vary the duration TOFF of the off-times, with the duration TOFF of the off-times increasing from a first lower bound value at the ramp edge towards a first upper bound value as the heads climb over the ramp.
10 . The control circuit of claim 9 , wherein the retract logic circuitry is configured to linearly vary the duration TOFF of the off-times from the first lower bound value towards the first upper bound value.
11 . The control circuit of claim 9 , wherein the first lower bound value and the first upper bound value of the duration TOFF of the off-times are about 200 us and about 600 us, respectively.
12 . The control circuit of claim 9 , wherein the retract logic circuitry is configured to vary the duration TON of the on-times with the duration TON of the on-times increasing from a second lower bound value at the ramp edge towards a second upper bound value as the heads climb over the ramp.
13 . The control circuit of claim 12 , wherein the retract logic circuitry is configured to vary the duration TON of the on-times as a function of the duration TOFF of the off-times.
14 . The control circuit of claim 13 , wherein the retract logic circuitry is configured to vary the duration TON of the on-times according to:
TON
=
K
1
*
TOFF
where:
K1 is a proportionality factor equal to 1.5 or 2.
15 . The control circuit of claim 12 , wherein the second lower bound value and the second upper bound value of the duration TON of the on-times are about 400 us and about 1200 us, respectively.
16 . The control circuit of claim 9 , wherein the retract logic circuitry is configured to control an intensity of the drive current through the VCM as a function of a back electromotive force of the VCM.
17 . A hard disk drive, comprising:
at least one voice coil motor (VCM); and
a control circuit comprising retract logic circuitry coupled to the VCM and configured to, during a retract phase:
operate the VCM to retract read-and-write heads of the hard disk drive from a disk surface towards an end-of-travel parking condition with the heads climbing over a ramp starting from a ramp edge adjacent the disk surface;
operate the VCM in a discontinuous mode comprising an alternation of on-times of a duration TON and off-times of a duration TOFF in which supply of a drive current to the VCM is facilitated and countered, respectively; and
vary the duration TOFF of the off-times, with the duration TOFF of the off-times increasing from a first lower bound value at the ramp edge towards a first upper bound value as the heads climb over the ramp.
18 . The hard disk drive of claim 17 , wherein the hard disk drive is disposed in a processing device.
19 . The hard disk drive of claim 17 , wherein the retract logic circuitry is configured to vary the duration TON of the on-times with the duration TON of the on-times increasing from a second lower bound value at the ramp edge towards a second upper bound value as the heads climb over the ramp.
20 . The hard disk drive of claim 17 , wherein the retract logic circuitry is configured to control an intensity of the drive current through the VCM as a function of a back electromotive force of the VCM.