Apparatus and method for control head unloading on power down in a disk drive

• US 6,396,652 B1
• Filed: 08/11/1999
• Issued: 05/28/2002
• Est. Priority Date: 08/12/1998
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Osafune, Koji, Kawachi, Hidetoshi
• Primary Examiner(s): Neal, Regina Y.
• Application Number:
  US09/371,634
• Time in Patent Office: 1,021 Days
• Field of Search: 360/75,73.03,78.04 318/254,245,439,456
• US Class Current: 360/75
• CPC Class Codes: G11B 21/12 Raising and lowering; Back-spacing or forward-spacing along track; Returning to starting position otherwise than during transducing operation
• CPC Class Codes: G11B 5/54 with provision for moving the head into or out of its operative position or across tracks

Abstract

Disclosed is a head loading/unloading type disk drive of retracting a head to a ramp by a reserve power supply upon power down of a main power supply. An unloading control system drives a VCM using a low-level voltage from the reserve power supply until the head reaches the ramp immediately upon power down of the main power supply. After the head reaches the ramp, the system applies a high-level voltage from the reserve power supply. The reserve power supply is made up of a rectifier for converting the back EMF of an SPM into a DC voltage. When a retract circuit detects power down of the main power supply, the DC voltage from the rectifier is limited to a low-level constant voltage by a constant voltage circuit, and applied to the VCM. When a ramp collision determining circuit determines collision of the head against the ramp, it controls the voltage applied to the VCM from the low-level voltage to a high-level voltage.

Claims

1. 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.

2. 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 reserve power means comprises;

a rectifier for rectifying a back electromotive force of a spindle motor for rotating the disk, and generating a relatively-high-level voltage; and

a constant voltage circuit for generating a constant voltage having a lower-level voltage value than the voltage level from the output voltage of said rectifier,

wherein said constant voltage circuit comprises;

comparison means for comparing a voltage applied to said actuator means with a reference value; and

a switching circuit for switching between application of the constant voltage to said actuation and stop of application thereof in accordance with a comparison result of said comparison means.