Patent ID: 6396652
Filing Date: 2002-05-28
Classification: G11B

Abstract:
A disk drive comprising:a head for reading/writing data from/on a disk; a ramp arranged outside the disk to unload the head; actuator means for supporting the head, and moving the head from the ramp over a predetermined range on a disk surface with a voice coil motor; reserve power means, arranged separately from a main power supply of said disk drive, for supplying a driving current to said actuator means upon power down of the main power supply; switching means for switching between a relatively-high-level voltage and low-level voltage from said reserve power means, and supplying the voltage to said actuator means; determining means for determining that the head comes into contact with the ramp by monitoring a change in voltage over time at a terminal of a coil of the voice coil motor; and control means for controlling said switching means in accordance with a determination result of said determining means upon power down of the main power supply so as to supply the low-level voltage from said reserve power means to said actuator means until the head moves to the ramp, and to supply the high-level voltage from said reserve power means to said actuator means when the head comes into contact with the ramp, wherein said determining means comprises: a detection circuit for detecting a back electromotive voltage induced by the coil of the voice coil motor included in said actuator means; a differentiating circuit for differentiating the back electromotive voltage by a time; and a comparison circuit for comparing an output value from said differentiating circuit with a reference value, and when the output value is not less than the reference value, outputting a determination signal representing that the head collides against the ramp.