Abstract: A circuit includes a driver circuit having a high side switch device and a low side switch device coupled to a load voltage node and a motor winding output. A controller operates the high side switch device and the low side switch device. The controller operates in a normal mode to supply current to the motor winding output for driving a motor winding when an external power supply is available to supply the load voltage node. In response to detecting a loss of the external power supply, the controller operates the high side switch device and the low side switch device in a boost mode to utilize a back electromotive force (BEMF) voltage from the motor winding to supply current to the load voltage node.

Abstract: Systems and methods for increasing Pulse Width Modulation (PWM) resolution for digitally controlled motor control applications are described. For example, in some embodiments, a method may include receiving a clock signal having a given period; identifying a target duty cycle; calculating a comparison point based upon the given period and the target duty cycle; generating a PWM signal based upon the clock signal using the comparison point; and varying the comparison point to increase a resolution of an effective duty cycle of the PWM signal.

Abstract: Systems and methods for increasing Pulse Width Modulation (PWM) resolution for digitally controlled motor control applications are described. For example, in some embodiments, a method may include receiving a clock signal having a given period; identifying a target duty cycle; calculating a comparison point based upon the given period and the target duty cycle; generating a PWM signal based upon the clock signal using the comparison point; and varying the comparison point to increase a resolution of an effective duty cycle of the PWM signal.

Abstract: A circuit includes a driver circuit having a high side switch device and a low side switch device coupled to a load voltage node and a motor winding output. A controller operates the high side switch device and the low side switch device. The controller operates in a normal mode to supply current to the motor winding output for driving a motor winding when an external power supply is available to supply the load voltage node. In response to detecting a loss of the external power supply, the controller operates the high side switch device and the low side switch device in a boost mode to utilize a back electromotive force (BEMF) voltage from the motor winding to supply current to the load voltage node.

Abstract: A quiet motor control system is described. This system digitally determines modulated voltages applied to motor phases in a manner that compensates for winding torque distortions, which reduces acoustic emissions.

Abstract: To achieve peak acoustic and power performance, the coil or applied current should be in phase or substantially aligned with the back electromotive force (back-EMF) voltage. However, there are generally phase differences between the applied current and back-EMF voltage that are induced by the impedance of the brushless DC motor (which can vary based on conditions, such as temperature and motor speed). Traditionally, compensation for these phase differences was provided manually and on an as-needed basis. Here, however, a system and method are provided that automatically perform a commutation advance by incrementally adjusting a drive signal over successive commutation cycles when the applied current and back-EMF voltage are misaligned.

Abstract: A quiet motor control system is described. This system digitally determines modulated voltages applied to motor phases in a manner that compensates for winding torque distortions, which reduces acoustic emissions.

Abstract: To achieve peak acoustic and power performance, the coil or applied current should be in phase or substantially aligned with the back electromotive force (back-EMF) voltage. However, there are generally phase differences between the applied current and back-EMF voltage that are induced by the impedance of the brushless DC motor (which can vary based on conditions, such as temperature and motor speed). Traditionally, compensation for these phase differences was provided manually and on an as-needed basis. Here, however, a system and method are provided that automatically perform a commutation advance by incrementally adjusting a drive signal over successive commutation cycles when the applied current and back-EMF voltage are misaligned.

Abstract: Traditionally, controllers for brushless, sensorless direct current (DC) motors (in, for example, Hard Disk Drive applications) would use one of the phases of the DC motor to measure a back electromotive force (back-EMF) voltage. This measurement would generally cause a discontinuity in the current waveform for a motor operating at a generally constant rotational speed (i.e., at “run speed”), which would result in poor acoustic performance (i.e., audible hum). Here, however, an integrated circuit (IC) is provided that uses coil current and applied voltage measurements to substantially maintain a predetermined phase difference between the phase of the applied voltage and back-EMF voltage, eliminating the need for a back-EMF voltage measurement and improving the acoustic performance.

Abstract: A circuit (90) and method are presented to accurately determine a BEMF voltage of a VCM coil (20) after termination of a driving current in a first current direction in the coil (20). The circuit includes a circuit for activating selected VCM coil driver transistors (44–47) to apply a current to the coil (20) in a direction opposite the first current direction to generate a magnetic field to oppose eddy currents established in structures adjacent the coil (20) by the driving current. The time that the eddy current opposing current may be applied may be determined, for example, by determining a magnitude of the original current command, a time that the coil spends in flyback, or a magnitude of the original driving current, and adjusting the time of application of the eddy current opposing current accordingly.

Abstract: A system and method of motor control enable improved motor control by controlling a phase winding to float or enter a high impedance state prior to activating phase detection of the phase winding. Because the phase winding floats prior to phase detection, the effect residual current coupling in such phase can be mitigated and thereby help improve motor operation.

Abstract: In a method and circuit for retracting a data transducer carrying assembly (17) in a mass data storage device (10), has the assembly (17) is positioned in response to a voltage applied to a driver mechanism (22), and a crash-stop barrier (21) against which the assembly (17) contacts when the assembly (17) is moved to the retract position (23). When a retract process is initiated, a determination is made whether the assembly (17) has contacted the crash-stop barrier (21). If the determination establishes that the assembly (17) has contacted the crash-stop barrier (21), the retract process is terminated. Determining whether the assembly (17) has contacted the crash-stop barrier (21) may be performed, for example, by determining an instantaneous direction of movement of the assembly (17), which may be determined by determining a sign change in the velocity measurements of the assembly (17).

Abstract: In a method and circuit for retracting a data transducer carrying assembly (17) in a mass data storage device (10), has the assembly (17) is positioned in response to a voltage applied to a driver mechanism (22), and a crash-stop barrier (21) against which the assembly (17) contacts when the assembly (17) is moved to the retract position (23). When a retract process is initiated, a determination is made whether the assembly (17) has contacted the crash-stop barrier (21). If the determination establishes that the assembly (17) has contacted the crash-stop barrier (21), the retract process is terminated. Determining whether the assembly (17) has contacted the crash-stop barrier (21) may be performed, for example, by determining an instantaneous direction of movement of the assembly (17), which may be determined by determining a sign change in the velocity measurements of the assembly (17).

Abstract: A system and method are provided for controlling operation of an actuator for retracting a read/write head of a hard disk drive system. One aspect of the system and method relates to controlling the actuator in response to a retract request command by first decelerating the actuator for a time period and then braking of the actuator for another time period. Another aspect of the system and method relates to controlling operation of the actuator during retract based on a sensed back EMF relative to a target back EMF, which may be selected by a user.

Abstract: A system and method of motor control enable improved motor control by controlling a phase winding to float or enter a high impedance state prior to activating phase detection of the phase winding. Because the phase winding floats prior to phase detection, the effect residual current coupling in such phase can be mitigated and thereby help improve motor operation.

Abstract: A method for characterizing a VCM assembly includes measuring a first response of the VCM assembly (100), removing a first conducting part of the VCM assembly (102), and measuring a second response of the VCM assembly with the first conducting part removed (104). Then, the method includes using curve fitting techniques (110) with the determined VCM compensation parameters to construct a model of the VCM assembly.

Abstract: A method is disclosed for controlling the voltage applied to a voice coil motor coil during the retract operations of a mass storage device, comprising a combination of three different voltage regulator stages. This method includes providing a first circuitry stage adapted to source current to a voice coil motor apparatus, raising the voltage across the voice coil motor to a desired level, providing a second circuitry stage adapted to draw current from the voice coil motor effecting a desired voltage across the voice coil motor, and providing a third circuitry stage adapted to raise the voltage of the voice coil motor to ground by effectively shorting the voice coil motor to ground.

Abstract: An actuator (12) has a movable member (20), and has a coil (26) which can be controlled to urge the member to move. In a particular mode of operation, a driver circuit (70) is periodically uncoupled from the coil so that the current through the coil goes to zero, after which the back-emf voltage of the coil is applied to a capacitor (94). Then, the driver circuit is recoupled to the coil, and the voltage held by the capacitor is used to effect feedback control of the driver circuit for the coil.

Abstract: An apparatus for controlling an actuator in response to a target speed voltage signal, the actuator having a moveable member and having a coil that influences movement of the member. A first summing node is provided having a control output voltage, for summing or subtracting voltages applied thereto, as the case may be and receiving the target speed voltage signal at a first, summing input thereto. A proportional compensation unit is provided, receiving the control output voltage and providing as an output a proportionally compensated output signal. An integral compensation unit is provided, receiving the control output voltage and providing as an output an integrally compensated output signal. An inverse compensation unit is provided, receiving the target speed voltage signal as an input and providing an inversely compensated output signal having a voltage corresponding to the voltage of the target speed voltage signal multiplied by the inverse of a predetermined amplification factor.

Abstract: An apparatus for controlling an actuator having a moveable member and having a coil that influences movement of the member, by provision of a drive current to the coil in response to a target speed voltage signal. The invention includes an up/down counter, counting at a predetermined count rate and providing a count output. A control unit is provided for controlling the direction of count of the up/down counter depending on whether the voltage across the coil, sensed periodically a first predetermined interval after the drive current to the coil is interrupted, is greater than, or less than, a reference voltage having a predetermined relationship to the target speed voltage. A digital-to-analog converter is provided, responsive to the count output to provide a compensated voltage signal having a voltage corresponding to the count output.