US6493169B1 — Disk drive employing spindle motor commutation ti…

Claim 1

Independent Claim 205 words

A disk drive that incidentally generates undesirable acoustic noise during an operation mode, the disk drive comprising: a spindle motor having a plurality of windings and a rotor rotatable at an operating spin-rate during the operation mode of the disk drive; switching elements; a commutation state sequencer including a sequence of commutation states for generating a sequence of control signals, the sequence of commutation states including a present commutation state and a next commutation state; the switching elements being responsive to the sequence of control signals for sequentially applying a voltage across a selected combination of the windings to generate a torque on the rotor in order to maintain the operating spin-rate; a spindle motor control system for providing a series of commutation clock pulses to advance the commutation state sequencer from the present commutation state to the next commutation state, the series of commutation clock pulses having a corresponding series of commutation clock periods, at least two of the commutation clock periods each having a systematically introduced variation from a nominal commutation clock period that depends on the operating spin-rate; and whereby the systematically introduced variation for each of the at least two commutation clock periods reduces the acoustic noise in the disk drive.

Claim 2

Dependent Claim 205 words

A disk drive that incidentally generates undesirable acoustic noise during an operation mode, the disk drive comprising: a spindle motor having a plurality of windings and a rotor rotatable at an operating spin-rate during the operation mode of the disk drive; switching elements; a commutation state sequencer including a sequence of commutation states for generating a sequence of control signals, the sequence of commutation states including a present commutation state and a next commutation state; the switching elements being responsive to the sequence of control signals for sequentially applying a voltage across a selected combination of the windings to generate a torque on the rotor in order to maintain the operating spin-rate; a spindle motor control system for providing a series of commutation clock pulses to advance the commutation state sequencer from the present commutation state to the next commutation state, the series of commutation clock pulses having a corresponding series of commutation clock periods, at least two of the commutation clock periods each having a systematically introduced variation from a nominal commutation clock period that depends on the operating spin-rate; and whereby the systematically introduced variation for each of the at least two commutation clock periods reduces the acoustic noise in the disk drive.

Claim 3

Dependent Claim 57 words

The disk drive of claim 1 wherein the spindle motor control system comprises: means for providing multiple systematically introduced variations in commutation periods, the accumulation of the variations within a series of the variations being substantially zero; and means for varying each of the at least two commutation clock periods by a selected one of the variations.

Claim 4

Dependent Claim 24 words

The disk drive of claim 2 wherein each series of variations is over an integer multiple of an electrical cycle of the spindle motor.

Claim 5

Dependent Claim 23 words

The disk drive of claim 2 wherein multiple series of variations are over an integer multiple of a mechanical revolution of the rotor.

Claim 6

Dependent Claim 18 words

The disk drive of claim 2 wherein the variations in each series alternate between negative and positive polarity.

Claim 7

Dependent Claim 27 words

The disk drive of claim 2 wherein the means for providing the multiple variations includes an offset table, having entries which in each represent a corresponding variation.

Claim 8

Dependent Claim 114 words

The disk drive of claim 1 wherein the rotor induces bemf across the windings, and the spindle motor control system includes means responsive to the bemf in the windings for controlling the voltage applied across the windings in order to maintain the operating spin-rate of the rotor, wherein the spindle motor control system monitors the time period between bemf zero crossings to determine speed error that is used for controlling the voltage applied across the windings which compensates for the speed error, wherein the time period between bemf zero crossings is monitored once per mechanical revolution of the rotor, and wherein the systematically introduced variation is within speed error tolerance for each mechanical revolution.

Claim 9

Dependent Claim 45 words

The disk drive of claim 1 wherein the rotor induces bemf across the windings, the spindle motor control system includes means responsive to the bemf in the windings for adjusting the time for providing the series of commutation clock pulses to the commutation state sequencer.

Claim 10

Dependent Claim 117 words

The disk drive of claim 1 wherein the spindle motor control system comprises: nominal commutation clock circuitry for generating a pre-series of commutation clock pulses having the nominal commutation clock period; a jitter clock generator for generating a fixed frequency clock which is asynchronous to the pre-series of commutation clock pulses having the nominal commutation clock period; and a flip-flop register having a data input, a clock input, and data output, wherein the clock input is coupled to the fixed frequency clock, the data input is coupled to the pre-series of commutation clock pulses having the nominal commutation clock period, and the data output provides the series of commutation clock pulses to advance the commutation state sequencer.

Claim 11

Independent Claim 200 words

A method of reducing acoustic noise in a disk drive that incidentally generates undesirable acoustic noise during an operation mode, the disk drive including a spindle motor having a plurality of windings and a rotor rotatable at an operating spin-rate during the operation mode of the disk drive; and a spindle motor driver having switching elements, the method comprising the steps of: providing a sequence of commutation states for generating a sequence of control signals, the sequence of commutation states including a present commutation state and a next commutation state; controlling the switching elements with the sequence of control signals to sequentially apply a voltage across a selected combination of the windings to generate a torque on the rotor in order to maintain the operating spin-rate; providing a series of commutation clock pulses to advance the sequence of commutation states from the present commutation state to the next commutation state, the series of commutation clock pulses having a corresponding series of commutation clock periods; and systematically introducing variation from a nominal commutation clock period that depends on the operating spin-rate into each of at least two of the commutation clock periods to reduce the acoustic noise in the disk drive.

Claim 12

Independent Claim 200 words

A method of reducing acoustic noise in a disk drive that incidentally generates undesirable acoustic noise during an operation mode, the disk drive including a spindle motor having a plurality of windings and a rotor rotatable at an operating spin-rate during the operation mode of the disk drive; and a spindle motor driver having switching elements, the method comprising the steps of: providing a sequence of commutation states for generating a sequence of control signals, the sequence of commutation states including a present commutation state and a next commutation state; controlling the switching elements with the sequence of control signals to sequentially apply a voltage across a selected combination of the windings to generate a torque on the rotor in order to maintain the operating spin-rate; providing a series of commutation clock pulses to advance the sequence of commutation states from the present commutation state to the next commutation state, the series of commutation clock pulses having a corresponding series of commutation clock periods; and systematically introducing variation from a nominal commutation clock period that depends on the operating spin-rate into each of at least two of the commutation clock periods to reduce the acoustic noise in the disk drive.

Claim 13

Dependent Claim 50 words

The method of claim 10 further comprising the steps of: providing multiple systematically introduced variations in commutation periods, the accumulation of the variations within a series of the variations being substantially zero; and varying each of the at least two commutation clock periods by a selected one of the variations.

Claim 14

Dependent Claim 23 words

The method of claim 11 wherein each series of variations is over an integer multiple of an electrical cycle of the spindle motor.

Claim 15

Dependent Claim 22 words

The method of claim 11 wherein multiple series of variations are over an integer multiple of a mechanical revolution of the rotor.

Claim 16

Dependent Claim 17 words

The method of claim 11 wherein the variations in each series alternate between negative and positive polarity.

Claim 17

Dependent Claim 109 words

The method of claim 10 wherein the rotor induces bemf across the windings, and the method further comprises the steps of: controlling the voltage applied across the windings in order to maintain the operating spin-rate of the rotor in response to the bemf in the windings; monitoring the time period between bemf zero crossings to determine speed error that is used for controlling the voltage applied across the windings which compensates for the speed error; and wherein the time period between bemf zero crossings is monitored once per mechanical revolution of the rotor wherein the percentage of systematically introduced variations is within speed error tolerance for each mechanical revolution.

Claim 18

Dependent Claim 45 words

The method of claim 10 wherein the rotor induces bemf across the windings, and the method further comprises the step of: adjusting the time for providing the series of commutation clock pulses to the commutation state sequence in response to the bemf in the windings.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2005-12-09	2006-06-10	2006-12-10	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2009-12-09	2010-06-10	2010-12-10	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2013-12-09	2014-06-10	2014-12-10	$7700.00	Window Closed / Lapsed

Disk drive employing spindle motor commutation time variation for reducing acoustic noise

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