Pulsed alignment commutation state for sensorless motor start

• US 5,821,715 A
• Filed: 07/26/1996
• Issued: 10/13/1998
• Est. Priority Date: 07/26/1996
• Status: Expired due to Fees

• Current Assignee: Western Digital Corporation
• Original Assignee: Western Digital Corporation
• Inventors: Warren, Robert W., Plutowski, Eugene F.
• Primary Examiner(s): Cabeca, John W.
• Application Number:
  US08/687,738
• Time in Patent Office: 809 Days
• Field of Search: 318/723, 318/722, 318/715, 318/696, 318/685, 318/254, 318/138, 318/798, 318/800, 318/799, 318/439, 318/603, 318/634, 318/635, 318/430, 318/445, 318/452, 318/471, 318/472, 318/484, 388/806, 388/815
• US Class Current: 318/472
• CPC Class Codes: H02P 1/04 Means for controlling progress of starting sequence in dependence upon time or upon current, speed, or other motor parameter
• CPC Class Codes: H02P 6/20 Arrangements for starting H02P6/08 takes precedence
• CPC Class Codes: H02P 6/28 Arrangements for controlling current H02P6/10 takes precedence

Abstract

A start-up controller is programmed to reduce current to a motor during a coast phase of an alignment state of the motor. The alignment state is divided into a plurality of phases based on time elapsed from the start of the alignment phase and the controller reduces the current when the elapsed time is substantially between a start and end time that define the coast phase. Because reduced current is provided to the motor during the coast phase, the total power and thus the thermal load on control components for the motor is decreased while the time the motor requires to "settle" into alignment is only slightly increased.

Claims

1. A method for reducing power consumption and thermal loads on control components that provide motor current to a spindle motor in a disk drive during an alignment state of a spin-up operation, the alignment state having an initial period for starting the spindle motor from a zero velocity, a coast period for coasting the spindle motor towards a known position, and a settle period for aligning and locking the spindle motor at the known position, the method comprising the steps of:

maintaining an elapsed time parameter that represents time elapsed from start of the alignment state, the coast period beginning when the elapsed time parameter has a first value and ending when the elapsed time parameter has a second value, the initial period preceding the coast period, the settle period following the coast period;

providing motor current having a first average magnitude to the spindle motor throughout the initial period;

reducing the motor current supplied to the spindle motor to a second average magnitude throughout the coast period;

increasing the motor current supplied to the spindle motor to a third average magnitude throughout the settle period;

whereby reducing the motor current during the coast period of the alignment state reduces the power consumption and the thermal loads on the control components.

2. A disk drive having a spindle motor, a power supply, and a variable duty cycle power driver for supplying motor current to the spindle motor from the power supply during an alignment state of a spin-up operation, the spindle motor consuming power during the alignment state that results in thermal loads on the power driver, the alignment state having an initial period for starting the spindle motor from a zero velocity, a coast period for coasting the spindle motor towards a known position, and a settle period for aligning and locking the spindle motor at the known position, the disk drive comprising:

a controller coupled to the power driver for controlling the motor current provided to the spindle motor during the alignment state;

means for maintaining an elapsed time parameter that represents time elapsed from start of the alignment state, the coast period beginning when the elapsed time parameter has a first value and ending when the elapsed time parameter has a second value, the initial period preceding the coast period, the settle period following the coast period;

the controller commanding the power driver to;

provide motor current having a first average magnitude to the spindle motor throughout the initial period;

reduce the motor current supplied to the spindle motor to a second average magnitude throughout the coast period;

increase the motor current supplied to the spindle motor to a third average magnitude throughout the settle period;

whereby reducing the motor current during the coast period of the alignment state reduces the power consumed by the spindle motor and the thermal loads on the power driver.