Abstract: The size of a reactor is reduced in a power supply device whose load circuit includes a second DC power supply. A power supply device includes: a chopper circuit CH connected between a first DC power supply E1 and load circuit L; and a filter circuit FI that includes a filter coil L2 and filter capacitor C and is interposed between the first DC power supply E1 and chopper circuit CH or between the second DC power supply E2 and chopper circuit CH; wherein the DC-current-inductance characteristic curve of the filter coil L2 and DC-current-inductance characteristic curve of the reactor L1 intersect each other, and the inductance value of the reactor L1 is made larger than that of the filter coil L2 in the region of current lower than a current value at the intersecting point.

Abstract: The size of a reactor is reduced in a power supply device whose load circuit includes a second DC power supply. A power supply device comprises: a chopper circuit CH connected between a first DC power supply E1 and load circuit L; and a filter circuit FI that includes a filter coil L2 and filter capacitor C and is interposed between the first DC power supply E1 and chopper circuit CH or between the second DC power supply E2 and chopper circuit CH; wherein the DC-current-inductance characteristic curve of the filter coil L2 and DC-current-inductance characteristic curve of the reactor L1 intersect each other, and the inductance value of the reactor L1 is made larger than that of the filter coil L2 in the region of current lower than a current value at the intersecting point.

Abstract: A disk drive comprising a head for accessing a disk, an actuator for moving the head in the radial direction of the disk and a controller. The controller for servo control of the actuator based on servo data read out from the disk by the head. The controller is configured for maintaining a width of the adaptive chasing notch filter below a specified value in servo system control and estimating an oscillation frequency of the actuator.

Abstract: A disk drive. The disk drive includes a head, an actuator, and a controller. The head accesses a disk. The actuator is configured to support the head and to move the head by action of a voice-coil motor in a substantially radial direction of the disk. The controller is also configured to perform servo control of the actuator by using servo data read out by the head. The controller includes at least one of a plurality of notch filters having a fixed center frequency inserted in a servo-control loop. The controller is configured to increase an attenuation rate by at least one of the plurality of notch filters having the fixed center frequency at a designated frequency, when a target position of the head is at a position selected from the group consisting of a position outside of a specified region and a position within the specified region.

Abstract: A servo control system configured to position a head in accordance with position error signals between servo data on a disk read by the head in a servo sampling cycle and a target position. The system includes a plurality of adaptive peak filters connected in parallel configured to filter the position error signals and configured to change filter coefficients adaptively, and an estimator configured to estimate head vibration caused by disturbances using the servo data read by the head. The system further includes a selector configured to select a portion of the plurality of adaptive peak filters at preset occasions, and a setter configured to update coefficient settings of the portion of the adaptive peak filters selected by the selector in accordance with an estimation by the estimator.

Abstract: A disk drive. The disk drive includes a head, a moving mechanism, a first peak filter, an adaptive peak filter, and a filter controller. The head is configured to read servo data on a disk at sampling frequency. The moving mechanism is configured to move the head in proximity with a recording surface of the disk. The first peak filter has a fixed peak frequency and a variable gain, and is configured to be inserted into a servo loop. The servo loop is configured to position the head with position error signals between servo data read by the head and a target position. The adaptive peak filter has a variable peak frequency and a variable gain, and is configured to be inserted into the servo loop. The filter controller is configured to control the gain of the adaptive peak filter according to the gain of the first peak filter.

Abstract: A servo control system configured to position a head in accordance with position error signals between servo data on a disk read by the head in a servo sampling cycle and a target position. The system includes a plurality of adaptive peak filters connected in parallel configured to filter the position error signals and configured to change filter coefficients adaptively, and an estimator configured to estimate head vibration caused by disturbances using the servo data read by the head. The system further includes a selector configured to select a portion of the plurality of adaptive peak filters at preset occasions, and a setter configured to update coefficient settings of the portion of the adaptive peak filters selected by the selector in accordance with an estimation by the estimator.

Abstract: A disk drive comprising a head for accessing a disk, an actuator for moving the head in the radial direction of the disk and a controller. The controller for servo control of the actuator based on servo data read out from the disk by the head. The controller is configured for maintaining a width of the adaptive chasing notch filter below a specified value in servo system control and estimating an oscillation frequency of the actuator.

Abstract: A disk drive. The disk drive includes a head, an actuator, and a controller. The head accesses a disk. The actuator is configured to support the head and to move the head by action of a voice-coil motor in a substantially radial direction of the disk. The controller is also configured to perform servo control of the actuator by using servo data read out by the head. The controller includes at least one of a plurality of notch filters having a fixed center frequency inserted in a servo-control loop. The controller is configured to increase an attenuation rate by at least one of the plurality of notch filters having the fixed center frequency at a designated frequency, when a target position of the head is at a position selected from the group consisting of a position outside of a specified region and a position within the specified region.

Abstract: Embodiments of the present invention help to perform appropriate servo control in response to detected vibration in a disk drive device having a vibration sensor. In an embodiment of the present invention, an HDD switches a correction servo mode to perform vibration correction in head positioning and a normal servo mode not to perform the vibration correction. The HDD performs servo positioning in either one of the serve modes and determines servo positioning accuracy in the servo mode from the measured positional error signal. The HDD obtains data indicating the servo positioning accuracy in the other servo mode from a table. The HDD compares the accuracy in the two servo modes and selects the servo mode with higher accuracy. The table contains previous measurements on servo positioning accuracy in the servo modes.

Abstract: A disk drive. The disk drive includes a head, a moving mechanism, a first peak filter, an adaptive peak filter, and a filter controller. The head is configured to read servo data on a disk at sampling frequency. The moving mechanism is configured to move the head in proximity with a recording surface of the disk. The first peak filter has a fixed peak frequency and a variable gain, and is configured to be inserted into a servo loop. The servo loop is configured to position the head with position error signals between servo data read by the head and a target position. The adaptive peak filter has a variable peak frequency and a variable gain, and is configured to be inserted into the servo loop. The filter controller is configured to control the gain of the adaptive peak filter according to the gain of the first peak filter.

Abstract: A method (and structure) senses a rotational vibration of a disk drive. The disk drive includes a rotating disk. The disk includes a plurality of reference bits across a surface thereof. The method (and structure) includes detecting the reference bits across a pattern on the rotating disk, and analyzing a time interval between adjacent ones of the reference bits.

Abstract: Detection capability of a servo timing mark (STM) is improved. Long STM is configured by pseudo-STM forming part of an AGC/PLL pattern and intrinsic STM. When a system can not recognize the intrinsic STM, it keeps a state that a sector detection window is opened, and is operated in a long STM detection mode to recognize the long STM, thereby generates an STM detection signal. After the STM detection signal has been generated, an STM detection window is closed, and the system is operated in an intrinsic STM detection mode. Since the long STM has longer bit length than the intrinsic STM, it has high discriminating power with respect to other bit patterns. Therefore, even if the sector detection window is remained to be in an opened state, bit strings of data sector, address information in a servo sector or the like is not falsely recognized.

Abstract: Embodiments in accordance with the present invention provide a magnetic disk drive with reduced noise during seek operation without causing any delay in control response. According to one embodiment of the present invention, a control circuit of a magnetic disk drive controls the drive power supplied to a voice coil motor during a seek operation adapted to move a magnetic head over a target track formed on a magnetic disk so as to bring the travel speed of the magnetic head close to a predetermined target speed. The control circuit determines a provisional current according to the difference between the predetermined target speed and an actual travel speed in an acceleration zone adapted to accelerate the magnetic head to the predetermined target speed. If the provisional current exceeds a limit specified in relation to an elapsed time from the start of acceleration, the control circuit sets the limit as the current of the drive power supplied to the voice coil motor to control the motor.

Abstract: Embodiments of the present invention help to achieve a read error recovery, and suppress decreases in the capacity of the disk drive device and degradation in performance. In one embodiment, a hard disk drive (HDD) performs following control without use of repeatable run-out (RRO) compensation information on a magnetic disk in a normal reading process. When an error occurs in a normal reading process, the HDD moves a read element to a position different from a target position of the normal reading process. At the position where the read element has been moved, the read element reads out the RRO compensation information. In a recovery procedure for the reading process where the error has occurred, the HDD performs following control with compensation by the servo compensation information read out by the read element.

Abstract: Embodiments in accordance with the present invention provide a magnetic disk drive with sufficiently low noise. A digital/analog converter supplies to a voice coil motor (VCM) driver a control voltage comprising a first preset voltage value, a second preset voltage value, and a transition voltage value of a substantially cosine wave that interconnects the first preset voltage value and the second preset voltage value. A driving current is supplied from the VCM driver to a voice coil of an actuator assembly. Since a current not containing higher-harmonic components in a transition period flows as a VCM current that flows into the voice coil, vibromotive force can be easily suppressed by shifting a structural resonance point of the entire disk drive including the actuator assembly.

Abstract: Embodiments of the present invention help to perform appropriate servo control in response to detected vibration in a disk drive device having a vibration sensor. In an embodiment of the present invention, an HDD switches a correction servo mode to perform vibration correction in head positioning and a normal servo mode not to perform the vibration correction. The HDD performs servo positioning in either one of the serve modes and determines servo positioning accuracy in the servo mode from the measured positional error signal. The HDD obtains data indicating the servo positioning accuracy in the other servo mode from a table. The HDD compares the accuracy in the two servo modes and selects the servo mode with higher accuracy. The table contains previous measurements on servo positioning accuracy in the servo modes.

Abstract: Embodiments in accordance with the present invention provide a disk drive that ensures quieter rotational acceleration of a recording disk. Certain embodiments relate to a hard disk drive that detects the vibration of an enclosure by monitoring, via a driver, a counter electromotive voltage generated in a voice coil motor. If the hard disk drive detects a predetermined level of vibration or higher in the enclosure, it switches the status of a drive signal applied to a spindle motor so as to reduce the current level or smooth the waveform. This ensures reduced vibration of the enclosure.

Abstract: Embodiments of the present invention help to achieve a read error recovery, and suppress decreases in the capacity of the disk drive device and degradation in performance. In one embodiment, a hard disk drive (HDD) performs following control without use of repeatable run-out (RRO) compensation information on a magnetic disk in a normal reading process. When an error occurs in a normal reading process, the HDD moves a read element to a position different from a target position of the normal reading process. At the position where the read element has been moved, the read element reads out the RRO compensation information. In a recovery procedure for the reading process where the error has occurred, the HDD performs following control with compensation by the servo compensation information read out by the read element.

Abstract: Embodiments in accordance with the present invention provide a magnetic disk drive with sufficiently low noise. A digital/analog converter supplies to a voice coil motor (VCM) driver a control voltage comprising a first preset voltage value, a second preset voltage value, and a transition voltage value of a substantially cosine wave that interconnects the first preset voltage value and the second preset voltage value. A driving current is supplied from the VCM driver to a voice coil of an actuator assembly. Since a current not containing higher-harmonic components in a transition period flows as a VCM current that flows into the voice coil, vibromotive force can be easily suppressed by shifting a structural resonance point of the entire disk drive including the actuator assembly.