Closed-loop rotational control of a brushless dc motor
First Claim
1. A method comprising applying a sequence of drive pulses to rotate a brushless dc motor, wherein the sequence of drive pulses is switched from a first commutation state to a second commutation state of the motor at a time determined in relation to changes in elapsed time between successive pulses in said sequence.
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Abstract
Method and apparatus for controlling a brushless dc motor, such as the type used in a data storage device to rotate data storage media. A sequence of drive pulses is applied to rotate the motor. The sequence is switched from first to second motor commutation states at a time determined in relation to changes in elapsed time between successive pulses in the sequence. Each drive pulse has a duration established in relation to an inductance of the motor, and is separated from adjacent pulses by an intermediate delay of predetermined value. A peak elapsed time interval between successive pulses is identified, and the next commutation state is switched in at a selected time after the peak time interval. The sequence preferably accelerates the motor from rest to an intermediate velocity, after which back electromotive force (bemf) commutation is used to accelerate the motor to a final operational velocity.
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Citations
19 Claims
- 1. A method comprising applying a sequence of drive pulses to rotate a brushless dc motor, wherein the sequence of drive pulses is switched from a first commutation state to a second commutation state of the motor at a time determined in relation to changes in elapsed time between successive pulses in said sequence.
- 11. An apparatus comprising a motor control block configured to apply a sequence of drive pulses to rotate a brushless dc motor, wherein the motor control block switches application of the sequence of drive pulses from a first commutation state to a second commutation state of the motor at a time determined in relation to changes in elapsed time between successive pulses in said sequence.
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19. An apparatus comprising a brushless dc motor and first means for rotating the motor by applying a sequence of drive pulses and by switching application of said sequence from a first commutation state to a second commutation state at a time determined in relation to changes in elapsed time between successive pulses in said sequence.
Specification