Quantum Corporation

Sassan Mortazavi

Mehran Ataee

A voice coil motor (VCM) driver has four field effect transistors connected to a motor coil as an H-bridge. A sense resistor in series with the coil and the H-bridge senses coil current. A feedback amplifier provides a feedback signal from a voltage developed across the sense resistor. A summing junction sums current command signals with the feedback signal. A transconductance loop compensation amplifier has an inverting input connected to the summing junction, has a non-inverting input connected to a reference level, and has an output control signal node. The control level is connected to control linear transconductance differential driver amplifiers including the four field effect transistors during a linear drive mode. A pulse width modulation (PWM) generator connected to the output control signal node generates variable duty cycle pulses related to the control level during a PWM drive mode applies the pulses to a first one of the four field effect transistors, and a polarity control circuit responds to a driving current direction signal by controlling another one of the four field effect transistors during the PWM drive mode.

PWM/linear driver for disk drive voice coil actuator

A voltage boost circuit within a hard disk drive is realized by switching a center tap node of a three phase spindle motor to ground during a power down sequence, thereby employing inductance of the spindle motor as a voltage boost inductor. The boosted voltage is rectified and stored in a capacitor for use, e.g. to control a source transistor of an actuator driver during an actuator retract operation.

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San Jose, CA, United States of America

Sassan Mortazavi