Data storage device compensating for fabrication tolerances when measuring spindle motor current

Patent metadata

Field	Value
Publication number	US-9396751-B1
Application number	US-201514752751-A
Country	US
Kind code	B1
Filing date	Jun 26, 2015
Priority date	Jun 26, 2015
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

A data storage device is disclosed comprising a spindle motor configured to rotate a disk, wherein the spindle motor comprises a stator, a rotor, and a plurality of windings. The data storage device further comprises an isolation circuit configured to isolate the windings from a supply voltage, a head actuated over the disk, and control circuitry comprising a spindle motor driver comprising a plurality of switches including a first switch and a second switch configured to commutate the windings. While driving the isolation circuit with a first calibration current, the first switch is driven with a second calibration current and a first current flowing through the first switch is measured. While driving the isolation circuit with the first calibration current, the second switch is driven with the second calibration current and a second current flowing through the second switch is measured.

First claim

What is claimed is:

1. A data storage device comprising:
a disk;
a spindle motor configured to rotate the disk, wherein the spindle motor comprises a stator, a rotor, and a plurality of windings;
an isolation circuit configured to isolate the windings from a supply voltage;
a head actuated over the disk; and
control circuitry comprising a spindle motor driver comprising a plurality of switches including a first switch and a second switch configured to commutate the windings, the control circuitry configured to:
while driving the isolation circuit with a first calibration current, drive the first switch with a second calibration current and measure a first current flowing through the first switch; and
while driving the isolation circuit with the first calibration current, drive the second switch with the second calibration current and measure a second current flowing through the second switch.

2. The data storage device as recited in claim 1 , wherein the control circuitry further comprises a first current source for generating the first calibration current and a second current source for generating the second calibration current.

3. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to:
generate a compensation value based on the measured first current;
measure a third current flowing through the first switch using the compensation value; and
estimate a position of the rotor relative to the stator based on the measured third current.

4. The data storage device as recited in claim 3 , wherein the compensation value compensates for a fabrication tolerance.

5. The data storage device as recited in claim 3 , wherein the control circuitry is further configured to generate the first calibration current based on a sum of a quiescent current and the second calibration current.

6. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to:
measure a current transient response of at least one of the windings to estimate a position of the rotor relative to the stator; and
generate the first calibration current and the second calibration current based on an average of the current transient response.

7. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to apply a calibration voltage to the isolation circuit when measuring the first current and when measuring the second current.

8. The data storage device as recited in claim 7 , wherein the control circuitry comprises a voltage source configured to generate the calibration voltage.

9. The data storage device as recited in claim 8 , wherein the voltage source is configured to sink at least part of the first calibration current when measuring the first current and when measuring the second current.

10. The data storage device as recited in claim 1 , further comprising a voice coil motor (VCM) configured to actuate the head over the disk and a VCM driver, wherein the control circuitry is further configured to:
while driving the isolation circuit with the first calibration current and driving the VCM driver with a third calibration current, drive the first switch with the second calibration current and measure a third current flowing through the first switch; and
while driving the isolation circuit with the first calibration current and driving the VCM driver with the third calibration current, drive the second switch with the second calibration current and measure a fourth current flowing through the second switch.

11. The data storage device as recited in claim 10 , wherein the third calibration current corresponds to a driving current applied to the VCM during at least one of a seek operation to seek the head over the disk and a tracking operation to track the head over a data track.

12. The data storage device as recited in claim 10 , wherein the control circuitry is further configured to generate the first calibration current based on a sum of the second calibration current and the third calibration current.

13. The data storage device as recited in claim 10 , wherein the control circuitry is further configured to:
generate a compensation value based on the measured third current;
measure a fifth current flowing through the first switch using the compensation value; and
estimate a position of the rotate relative to the stator based on the measured fifth current.

14. The data storage device as recited in claim 1 , wherein while driving the isolation circuit with the first calibration current and driving the first switch with the second calibration current, the control circuitry is further configured to drive the second switch with a third calibration current while measuring the first current flowing through the first switch.

15. The data storage device as recited in claim 14 , wherein the control circuitry comprises a current source for generating the third calibration current.

16. A method of operating a data storage device, the method comprising:
while driving an isolation circuit with a first calibration current, driving a first switch of a spindle motor driver with a second calibration current and measuring a first current flowing through the first switch; and
while driving the isolation circuit with the first calibration current, driving a second switch of the spindle motor driver with the second calibration current and measuring a second current flowing through the second switch.

17. The method as recited in claim 16 , further comprising generating the first calibration current using a first current source and generating the second calibration current using a second current source.

18. The method as recited in claim 16 , further comprising:
generating a compensation value based on the measured first current;
measuring a third current flowing through the first switch using the compensation value; and
estimating a position of a rotor of a spindle motor relative to a stator of the spindle motor based on the measured third current.

19. The method as recited in claim 18 , wherein the compensation value compensates for a fabrication tolerance.

20. The method as recited in claim 18 , further comprising generating the first calibration current based on a sum of a quiescent current and the second calibration current.

21. The method as recited in claim 16 , further comprising:
measuring a current transient response of at least one of the windings to estimate a position of a rotor of a spindle motor relative to a stator of the spindle motor; and
generating the first calibration current and the second calibration current based on an average of the current transient response.

22. The method as recited in claim 16 , further comprising applying a calibration voltage to the isolation circuit when measuring the first current and when measuring the second current.

23. The method as recited in claim 22 , further comprising generating the calibration voltage using a voltage source.

24. The method as recited in claim 23 , further comprising the voltage source sinking at least part of the first calibration current when measuring the first current and when measuring the second current.

25. The method as recited in claim 16 , further comprising:
while driving the isolation circuit with the first calibration current and driving a voice coil motor (VCM) driver with a third calibration current, driving the first switch with the s

Assignees

• Western Digital Tech Inc

Inventors

• Byoun Jaesoo
• Ferris Timothy A

Classifications

• G11B19/247 Primary

  using electrical means · CPC title

• G11B19/2081

  emergency power-down · CPC title

• G11B19/2009 Primary

  Turntables, hubs and motors for disk drives; Mounting of motors in the drive (means for clamping of disk to turntable G11B17/022 and subgroups) · CPC title

• G11B19/28

  Speed controlling, regulating, or indicating (G11B19/24 takes precedence) · CPC title