Data storage device employing a phase offset to generate power from a spindle motor during a power failure
View Patent ↗A data storage device is disclosed comprising a disk, a spindle motor configured to rotate the disk, wherein the spindle motor comprises a plurality of windings, and a head actuated over the disk. The windings are commutated based on a commutation sequence while applying a periodic driving voltage to each winding, wherein the periodic driving voltage comprises an operating amplitude during normal operation. When a supply voltage falls below a threshold, the spindle motor is configured into a power generator by at least adjusting a phase of the periodic driving voltage by a phase offset and adjusting the amplitude of the periodic driving voltage based on the phase offset.
1. A data storage device comprising:
a disk;
a spindle motor configured to rotate the disk, wherein the spindle motor comprises a plurality of windings;
a head actuated over the disk; and
control circuitry powered by a supply voltage, the control circuitry configured to:
commutate the windings based on a commutation sequence while applying a periodic driving voltage to each winding, wherein the periodic driving voltage comprises an operating amplitude during normal operation; and
when the supply voltage falls below a threshold, configure the spindle motor into a power generator by at least adjusting a phase of the periodic driving voltage by a phase offset and by adjusting the amplitude of the periodic driving voltage based on the phase offset.
2. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to adjust the amplitude of the periodic driving voltage based on:
C
1
·
Vbo
Vpwr_min
(
cos
ϕ
PO
-
L
ω
ecyco
R
sin
ϕ
PO
)
where:
C1 represents a scalar;
|Vbo| represents an amplitude of a sinusoidal back electromotive force (BEMF) voltage generated by one of the windings;
L represents an inductance of the winding;
ω ecyco represents a frequency of the sinusoidal BEMF voltage generated by the winding;
R represents a resistance of the winding;
φ PO represents the phase offset relative to the sinusoidal BEMF voltage; and
Vpwr_min represents a minimum amplitude of the supply voltage.
3. The data storage device as recited in claim 2 , wherein an amplitude of the periodic driving voltage is generated based on:
C 2 ·V pwr·DAC %
where:
C2 represents a scalar;
Vpwr represents the supply voltage; and
DAC % represents a scalar.
4. The data storage device as recited in claim 3 , wherein:
DAC
%
=
C
1
·
Vbo
Vpwr_min
(
cos
ϕ
PO
-
L
ω
ecyco
R
sin
ϕ
PO
)
.
5. The data storage device as recited in claim 4 , wherein the spindle motor generates a peak power when Vpwr falls to Vpwr_min.
6. The data storage device as recited in claim 5 , wherein Vpwr_min is selected based on a peak power needed to park the head under worst case conditions.
7. The data storage device as recited in claim 6 , wherein when Vpwr substantially equals Vpwr_min the control circuitry is further configured to reduce the power consumed when parking the head.
8. The data storage device as recited in claim 7 , wherein when Vpwr substantially equals Vpwr_min, the control circuitry is configured to reduce the power consumed when parking the head by reducing a power consumed by a voice coil motor configured to actuate the head radially over the disk.
9. The data storage device as recited in claim 3 , wherein a power generating efficiency of the spindle motor increases as Vpwr rises above Vpwr_min.
10. The data storage device as recited in claim 9 , wherein Vpwr rises above Vpwr_min when a load powered by the spindle motor decreases.
11. A method of operating a data storage device, the method comprising:
rotating a disk using a spindle motor comprising a plurality of windings;
actuating a head over the disk;
commutating the windings based on a commutation sequence while applying a periodic driving voltage to each winding, wherein the periodic driving voltage comprises an operating amplitude during normal operation; and
when a supply voltage falls below a threshold, configuring the spindle motor into a power generator by adjusting a phase of the periodic driving voltage by a phase offset and by at least adjusting the amplitude of the periodic driving voltage based on the phase offset.
12. The method as recited in claim 11 , further comprising adjusting the amplitude of the periodic driving voltage based on:
C
1
·
Vbo
Vpwr_min
(
cos
ϕ
PO
-
L
ω
ecyco
R
sin
ϕ
PO
)
where:
C1 represents a scalar;
|Vbo| represents an amplitude of a sinusoidal back electromotive force (BEMF) voltage generated by one of the windings;
L represents an inductance of the winding;
ω ecyco represents a frequency of the sinusoidal BEMF voltage generated by the winding;
R represents a resistance of the winding;
φ PO represents the phase offset relative to the sinusoidal BEMF voltage; and
Vpwr_min represents a minimum amplitude of the supply voltage.
13. The method as recited in claim 12 , wherein an amplitude of the periodic driving voltage is generated based on:
C 2 ·V pwr·DAC %
where:
C2 represents a scalar;
Vpwr represents the supply voltage; and
DAC % represents a scalar.
14. The method as recited in claim 13 , wherein:
DAC
%
=
C
1
·
Vbo
Vpwr_min
(
cos
ϕ
PO
-
L
ω
ecyco
R
sin
ϕ
PO
)
.
15. The method as recited in claim 14 , wherein the spindle motor generates a peak power when Vpwr falls to Vpwr_min.
16. The method as recited in claim 15 , wherein Vpwr_min is selected based on a peak power needed to park the head under worst case conditions.
17. The method as recited in claim 16 , wherein when Vpwr substantially equals Vpwr_min the method further comprises reducing the power consumed when parking the head.
18. The method as recited in claim 17 , wherein when Vpwr substantially equals Vpwr_min, the method further comprises reducing the power consumed when parking the head by reducing a power consumed by a voice coil motor configured to actuate the head radially over the disk.
19. The method as recited in claim 13 , wherein a power generating efficiency of the spindle motor increases as Vpwr rises above Vpwr_min.
20. The method as recited in claim 19 , wherein Vpwr rises above Vpwr_min when a load powered by the spindle motor decreases.
21. Control circuitry powered by a supply voltage, the control circuitry configured to:
commutate windings of a spindle motor based on a commutation sequence while applying a periodic driving voltage to each winding, wherein the periodic driving voltage comprises an operating amplitude during normal operation; and
when the supply voltage falls below a threshold, configure the spindle motor into a power generator by at least adjusting a phase of the periodic driving voltage by a phase offset and adjusting the amplitude of the periodic driving voltage based on the phase offset.
22. The control circuitry as recited in claim 21 , further configured to adjust the amplitude of the periodic driving voltage based on:
C
1
·
Vbo
Vpwr_min
(
cos
ϕ
PO
-
L
ω
ecyco
R
sin
ϕ
PO
)
where:
C1 represents a scalar;
|Vbo| represents an amplitude of a sinusoidal back electromotive force (BEMF) voltage generated by one of the windings;
L represents an inductance of the winding;
ω ecyco represents a frequency of the sinusoidal BEMF voltage generated by the winding;
R represents a resistance of the winding;
φ PO represents the phase offset relative to the sinusoidal BEMF voltage; and
Vpwr_min represents a minimum amplitude of the supply voltage.
23. The control circuitry as recited in claim 22 , wherein an amplitude of the periodic driving voltage is generated based on:
C 2 ·V pwr·DAC %
where:
C2 represents a scalar;
Vpwr represents the supply voltage; and
DAC % represents a scalar.
24. The control circuitry as recited in claim 23 , wherein:
DAC
%
=
C
1
·
Vbo
Vpwr_min
(
cos
ϕ
PO
-
L
ω
ecyco
R
sin
ϕ
PO
)
.