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.

Abstract: An electronic ballast circuit includes a programmable processor. The processor is programmed to vary operating parameters of the ballast circuit to accommodate operation of different types and/or sizes of lamps. Ballast circuit operating parameters that can be varied by the programmable processor include component parameters, such as inductance and resistance, and the frequency at which the ballast circuit is oscillated. The processor can be programmed to produce an oscillating processor signal which is used to produce a corresponding oscillating power signal to ignite and/or sustain ignition of the lamp. A voltage monitor and a current monitor are employed to monitor the operating condition of the lamp. The monitor outputs are used by the processor to optimize circuit operation.

Abstract: Method and apparatus for performing a seek operation to move a data transducing head from an initial track to a destination track on a rotatable recording surface. A servo control circuit operates to sweep the head across the recording surface. Servo data from an intermediary track are transduced to obtain a detected angular position value for the head with respect to the recording surface. When the detected angular position value differs from a predicted angular position value for the head, the servo control circuit initiates an index qualification routine at the conclusion of the seek. The qualification routine involves transducing the servo data from the destination track to verify the accuracy of the predicted angular position value. In this way, the effects of spurious (false) index signals obtained from the servo data transduced during the seek operation are minimized, and unnecessary reinitializations of the servo control circuit are avoided.

Abstract: Method and apparatus for reducing and dispersing wear to the surface of a rotatable disc in a disc drive using an adaptive dither process. The disc drive includes an actuator assembly that is secured in a parked position by a latch when not in use. The method includes determining an open latch current required to open the latch as the actuator assembly is moved from the parked position to a position over a user data storage portion of the disc. A dither current is subsequently applied to the actuator assembly to induce a reciprocating lateral displacement of the actuator assembly when the actuator assembly is secured in the parked position, wherein the maximum amplitude of the dither current is selected to be less than the open latch current.

Abstract: Method and apparatus for improving data transfer rate performance of a disc drive data handling system having a plurality of transducing heads adjacent a corresponding plurality of data recording surfaces. Concentric tracks on each of the recording surfaces are provided with a physical track address determined by servo data written to each track. Logical track addresses are assigned to the tracks by positioning a first head adjacent a selected location on the corresponding recording surface, measuring a head offset value for each of the remaining heads, and assigning the logical track addresses on each data recording surface in relation to the measured head offset values. The logical cylinders include tracks with different physical track addresses, and the tracks in each logical cylinder are nominally aligned with the heads. This reduces the need for corrective seeks after head switching within the same logical cylinder.

Abstract: An electronic ballast circuit includes a programmable processor. The processor is programmed to vary operating parameters of the ballast circuit to accommodate operation of different types and/or sizes of lamps. Ballast circuit operating parameters that can be varied by the programmable processor include component parameters, such as inductance and resistance, and the frequency at which the ballast circuit is oscillated. The processor can be programmed to produce an oscillating processor signal which is used to produce a corresponding oscillating power signal to ignite and/or sustain ignition of the lamp. A voltage monitor and a current monitor are employed to monitor the operating condition of the lamp. The monitor outputs are used by the processor to optimize circuit operation.

Abstract: An electronic ballast operates a gaseous discharge lamp. The electronic ballast includes a filter circuit for removing noise from an electrical power signal. The power factor of the filtered power signal is adjusted by a power factor correction circuit. The power factor correction circuit includes a programmable inductor circuit having a plurality of selectable inductance values for varying the amount of power factor adjustment to accommodate operation of different lamp types and/or different lamp wattages. A power supply circuit converts electrical power received from the filtered power signal to provide low level power for operating the electronic ballast. An output circuit receives the corrected power signal produced by the power factor correction circuit and produces an electrical signal to ignite and operate the discharge lamp.

Abstract: An electronic ballast operates a gaseous discharge lamp. The electronic ballast includes a filter circuit for removing noise from an electrical power signal. The power factor of the filtered power signal is adjusted by a power factor correction circuit. The power factor correction circuit includes a programmable inductor circuit having a plurality of selectable inductance values for varying the amount of power factor adjustment to accommodate operation of different lamp types and/or different lamp wattages. A power supply circuit converts electrical power received from the filtered power signal to provide low level power for operating the electronic ballast. An output circuit receives the corrected power signal produced by the power factor correction circuit and produces an electrical signal to ignite and operate the discharge lamp.

Abstract: Method and apparatus for performing a seek operation to move a data transducing head from an initial track to a destination track on a rotatable recording surface. A servo control circuit operates to sweep the head across the recording surface. Servo data from an intermediary track are transduced to obtain a detected angular position value for the head with respect to the recording surface. When the detected angular position value differs from a predicted angular position value for the head, the servo control circuit initiates an index qualification routine at the conclusion of the seek. The qualification routine involves transducing the servo data from the destination track to verify the accuracy of the predicted angular position value. In this way, the effects of spurious (false) index signals obtained from the servo data transduced during the seek operation are minimized, and unnecessary reinitializations of the servo control circuit are avoided.

Abstract: Method and apparatus for controlling a motor below a threshold velocity. During a velocity control mode, the motor is accelerated to an operational velocity, receives a commanded velocity value, and switches from a first control method to a second control method below the threshold velocity. The threshold velocity is determined from limitations of control electronics that do not function well when a motor current drops below the threshold level. The sliding mode control method measures the measured motor velocity, compares the velocity to the commanded velocity, applies a current value when the measured value is less than the commanded value and applies a negligible current value when the measured value is greater than the commanded value. The threshold level is dictated by the first control method. Back electromotive force (bemf) detection circuitry is used to measure the motor current.

Abstract: Method and apparatus for reducing and dispersing wear to the surface of a rotatable disc in a disc drive using an adaptive dither process. The disc drive includes an actuator assembly that is secured in a parked position by a latch when not in use. The method includes determining an open latch current required to open the latch as the actuator assembly is moved from the parked position to a position over a user data storage portion of the disc. A dither current is subsequently applied to the actuator assembly to induce a reciprocating lateral displacement of the actuator assembly when the actuator assembly is secured in the parked position, wherein the maximum amplitude of the dither current is selected to be less than the open latch current.

Abstract: Method and apparatus for improving data transfer rate performance of a disc drive data handling system having a plurality of transducing heads adjacent a corresponding plurality of data recording surfaces. Concentric tracks on each of the recording surfaces are provided with a physical track address determined by servo data written to each track. Logical track addresses are assigned to the tracks by positioning a first head adjacent a selected location on the corresponding recording surface, measuring a head offset value for each of the remaining heads, and assigning the logical track addresses on each data recording surface in relation to the measured head offset values. The logical cylinders include tracks with different physical track addresses, and the tracks in each logical cylinder are nominally aligned with the heads. This reduces the need for corrective seeks after head switching within the same logical cylinder.