Disk drive employing active braking using inductive sense
View Patent ↗A disk drive is disclosed comprising a disk, a head actuated over the disk, and a spindle motor for rotating the disk, the spindle motor comprising a plurality of windings. Disk control circuitry executes a spin-down operation of the spindle motor by estimating an angular position of the spindle motor by applying a voltage to at least one of the windings and evaluating a rise time of current flowing through the winding. The windings are commutated in response to the estimated angular position, and a driving current is applied to the windings to brake the spindle motor.
1. A disk drive comprising:
(a) a disk;
(b) a head actuated over the disk;
(c) a spindle motor for rotating the disk, the spindle motor comprising a plurality of windings configurable into a plurality of commutation states; and
(d) disk control circuitry for executing a spin-down operation of the spindle motor by:
estimating an angular position of the spindle motor by applying a voltage to at least one of the windings and evaluating a rise time of current flowing through the winding;
configuring the windings into a selected one of the commutation states in response to the estimated angular position; and
applying a driving current to the windings of the selected commutation state to brake the spindle motor.
2. The disk drive as recited in claim 1 , wherein the disk control circuitry estimates an angular velocity of the spindle motor in response to the estimated angular position.
3. The disk drive as recited in claim 2 , wherein the disk control circuitry shorts the windings in order to brake the spindle motor when the estimated angular velocity falls below a predetermined threshold.
4. The disk drive as recited in claim 2 , wherein the disk control circuitry shorts the windings in order to brake the spindle motor when the estimated angular velocity is substantially zero.
5. The disk drive as recited in claim 1 , wherein the disk control circuitry periodically estimates the angular position of the spindle motor to determine when to change the selected commutation state.
6. The disk drive as recited in claim 1 , wherein the disk control circuitry disables the driving current while estimating the angular position of the spindle motor.
7. A method of spinning down a disk drive, the disk drive comprising a disk, a head actuated over the disk, and a spindle motor for rotating the disk, the spindle motor comprising a plurality of windings configurable into a plurality of commutation states, the method comprising:
(a) estimating an angular position of the spindle motor by applying a voltage to at least one of the windings and evaluating a rise time of current flowing through the winding;
(b) configuring the windings into a selected one of the commutation states in response to the estimated angular position; and
(c) applying a driving current to the windings of the selected commutation state to brake the spindle motor.
8. The method as recited in claim 7 , further comprising estimating an angular velocity of the spindle motor in response to the estimated angular position.
9. The method as recited in claim 8 , further comprising shorting the windings in order to brake the spindle motor when the estimated angular velocity falls below a predetermined threshold.
10. The method as recited in claim 8 , further comprising shorting the windings in order to brake the spindle motor when the estimated angular velocity is substantially zero.
11. The method as recited in claim 7 , further comprising periodically estimating the angular position of the spindle motor to determine when to change the selected commutation state.
12. The method as recited in claim 7 , wherein estimating the angular position of the spindle motor comprises disabling the driving current.