Stmicroelectronics Gmbh

Stmicroelectronics S.r.l.

Stmicroelectronics Asia Pacific Pte Limited

Frederic Bonvin

Ezio Galbiati

Agostino Mirabelli

Maurizio Nessi

Davide Betta

Diego Armaroli

Seng-Chean Hong

Andrea Di Ruzza

A drive circuit having asymmetrical drivers. In an embodiment, a brushless DC motor may be driven by a drive circuit having three high-side MOSFETs and three low-side MOSFETs. A driver controller turns the MOSFETs on and off according to a drive algorithm such that phase currents are injected into motor coils to be driven. The high-side MOSFETs may be sized differently than the low-side MOSFETs. As such, when a MacDonald waveform (or similar drive algorithm) is used to drive the phases of the motor, less power may be required during disk spin-up because the MOSFETs that are on more (e.g., the low-side MOSFETs with a MacDonald waveform) may be sized larger than the MOSFETs that are on less (e.g., the high-side MOSFETs). In this manner, less power is dissipated in the larger size MOSFETs that are on more than the others.

Asymmetrical driver

An embodiment of a motor controller includes a motor driver and a signal conditioner. The motor driver is operable to generate a motor-coil drive signal having a first component at a first frequency, and the signal conditioner is coupled to the motor driver and is operable to alter the first component. For example, if the first component of the motor-coil drive signal causes the motor to audibly vibrate (e.g., 'whine'), then the signal conditioner may alter the amplitude or phase of the first component to reduce the vibration noise to below a threshold level.

Motor controller with drive-signal conditioning

An embodiment of a motor controller includes first and second supply nodes, a motor-coil node, an isolator, a motor driver, and a motor position signal generator. The isolator is coupled between the first and second supply nodes, and the motor driver is coupled to the second supply node and to the motor-coil node. The motor position signal generator is coupled to the isolator and is operable to generate, in response to the isolator, a motor-position signal that is related to a position of a motor having at least one coil coupled to the motor-coil node. By generating the motor-position signal in response to the isolator, the motor controller or another circuit may determine the at-rest or low-speed position of a motor without using an external coil-current-sense circuit.

Determining a position of a motor using an on-chip component

Techniques and apparatus for limiting the current through a motor, such as a motor for rotating a rotatable element of a hard drive. The current can be limited based on a threshold. A first threshold value can be set for a first time period. A second threshold value can be set for a second time period in which the current through the motor rises. The second threshold value is lower than the first threshold value. A spike in the supply current upon accelerating the rotatable element of the motor can thereby be reduced or eliminated.

Current limiting for a motor winding

Applicant has recognized and appreciated the desirability of powering an actuator using power drawn from one or both of an energy storage device and a spindle motor. In some embodiments, following a loss of external power to a hard disk drive, the hard disk drive (or one or more components thereof) determines whether to provide the actuator with power drawn from the spindle motor or to provide the actuator with power drawn from the spindle motor and from the energy storage device. In some embodiments, the hard disk drive (or the component(s) thereof) may additionally or alternatively determine whether to charge the energy storage device using power drawn from the spindle motor. In some embodiments, the drive may make the determinations based on an amount of power that the actuator is to consume at a time and an amount of power that the spindle motor can provide at the time.

Regulating distribution of power in a hard disk drive following a power loss

An embodiment of a motor controller includes a motor driver and a signal conditioner. The motor driver is configured to generate a motor-coil drive signal having a first component at a first frequency, and the signal conditioner is coupled to the motor driver and is configured to alter the first component. For example, if the first component of the motor-coil drive signal causes the motor to audibly vibrate (e.g., 'whine'), then the signal conditioner may alter the amplitude or phase of the first component to reduce the vibration noise to below a threshold level.

A system and method for determining the start position of a motor. According to an embodiment, a voltage pulse signal may be generated across a pair of windings in a motor. A current response signal will be generated and based upon the position of the motor, the response signal will be greater in one pulse signal polarity as opposed to an opposite pulse signal polarity. The response signal may be compared for s specific duration of time or until a specific integration threshold has been reached. Further, the response signal may be converted into a digital signal such that a sigma-delta circuit may smooth out glitches more easily. In this manner, the position of the motor may be determined to within 60 electrical degrees during a startup.

System and method for determining the start position of a motor

A method and circuit to stop a spindle motor in the absence of the external supply voltage in which the spindle motor is structured to move a hard disk provided with at least one reading or writing head moved by a voice coil motor, the spindle motor provided with a plurality of coils. The method includes rectifying the backelectromotive force of the spindle motor to produce a braking current, driving the voice coil motor with at least a portion of the braking current until the speed of the spindle motor becomes lower than a predetermined stop speed, and, after the parking of the at least one reading or writing head of the voice coil motor, stopping the spindle motor by short-circuiting the coils of the spindle motor.

Stopping method for a spindle motor and related device

An embodiment of a circuit for maintaining voltage at a voltage bus after a power loss in a hard disk drive system. HDD systems may suddenly lose power and specific tasks, such as parking the read/write head and storing state data may be accomplished using a power generated from back EMF of a motor that is still turning. During the power loss sequence, a drive controller may drive a power chipset to regulate the voltage at a voltage bus so as to conserve power as much as possible. In this manner, the drive circuit may regulate the voltage via a drive algorithm to be just above a threshold voltage (typically 4.4 V) while the HDD system is storing state data, but apply other algorithm for other situations, such as parking the read/write head. Various drive algorithms may be tailored to provide a specific sequence of voltage bus regulation techniques suited to specific applications.

Management of disk drive during power loss

In BLDC motors driven via sensorless techniques, the BEMF signals in the motor coils may be used to detect the position of the motor such that speed of the motor may be accurately controlled. When detecting the BEMF signals, however, small perturbations occur which negatively impact the rotational torque of the motor. As a result, torque ripple may occur at regular intervals which may result in inefficiencies as well as audible noise. In various embodiments as described herein, the sampling of the BEMF signals may be done so at pseudo-random intervals such that the overall spectral energy that presents from the BEMF detections may be reduced at specific frequencies (such as fundamental sampling frequencies and harmonics thereof) and spread out over many more frequencies. Thus, despite the overall spectral energy being the same, the amplitude of any given frequency is lower as the sampling of the BEMF is less periodic.

Reducing the spectral energy of torque ripple

Disk drive spindle jitter is comprised of electrical noise, error due to pair pole asymmetry, and random disk speed variances. Error caused by pair pole asymmetry can be identified and compensated for by detecting over a single rotation of a rotor a plurality of zero cross signals. These signals can be statistically analyzed over a period of a plurality of revolutions of the rotor so as to identify the systematic error caused by pair poles. Once identified, this pair pole error can be used to modify zero cross signals and/or modify commutation signal driving the disk so as to arrive at a more accurate determination of disk speed and to precisely control the speed of the disk.

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Longmont, CO, United States of America

Frederic Bonvin