Patent ID: 8143829
Filing Date: 2012-03-27
Classification: G11B

Abstract:
1. A disk drive system including one or more magnetic disks arranged in a stack and rotatable on a spindle, a read/head movable relative to a surface of an associated magnetic disk, a DC motor for rotating the spindle and a voice-coil motor for actuating the read/write head, said system comprising: a plurality of power transistors arranged in respective H-bridges with respect to each winding in the DC motor on an upper motor control circuit; an equal plurality of power transistors arranged in the respective H-bridges with respect to each winding in the DC motor on a lower motor control circuit; and a comparator operable to couple across each of the plurality of power transistors; wherein the disk drive system is operable such that, during power interruption, a back-EMF voltage in a first motor winding is increasing and crosses a decreasing back-EMF in second motor winding at a voltage-crossing on the upper motor control circuit, and the comparator associated with the first motor winding is turned ON when the comparator input is above the supply rail voltage, thereby turning ON the transistor associated with the comparator and allowing the voltage above the voltage-crossing to pass through the transistor and, at the same time, turning OFF the transistor associated with the third motor winding; wherein the disk drive system is operable such that the back-EMF voltage in a first motor winding is decreasing and crosses an increasing back-EMF voltage in a third motor winding at a voltage-crossing on the lower motor control circuit, and the comparator associated with the second winding is turned ON when the comparator input is below the ground rail voltage, thereby turning ON the transistor associated with the comparator and, at the same time, turning OFF the transistor associated with the second motor winding; and wherein the disk drive system is operable to repeat the turning ON and OFF of the transistors in a cyclical manner in accordance with a sequence of commutating of the DC motor.