Magnetic disk storage apparatus and method for controlling magnetic disk storage apparatus
View Patent ↗In a magnetic disk storage apparatus, when power supply is stopped, a magnetic head can be retracted safely and quickly so as not to be damaged. There are provided a back electromotive a force detector that detects back electromotive forces developed in coils of a voice coil motor for moving a magnetic head when power a supply is stopped, and a brake controller that judges a movement speed of the magnetic head from the detected back electromotive forces, and brakes the voice coil motor when the movement speed is greater than a preset first limited speed.
1. A magnetic disk storage apparatus comprising:
a first motor for rotating a magnetic disk;
a magnetic head for reading information from storage tracks on the magnetic disk rotated by the first motor;
a second motor for moving the magnetic head over the magnetic disk;
a second motor driving control circuit for controlling a movement of the magnetic head by controlling drive currents of the second motor;
a back electromotive force detecting circuit;
a brake control circuit; and
a retract control circuit,
wherein the brake control circuit includes a first comparator; and a second comparator,
wherein a first threshold voltage corresponds to a first preset speed of the magnetic head in a first direction being inward of the magnetic disk, and a second threshold voltage corresponds to a second preset speed of the magnetic head in a second direction being outward of the magnetic disk,
wherein the first threshold voltage is inputted to a first input terminal of the first comparator, the second threshold voltage is inputted to a second input terminal of the second comparator, and a first back electromotive force of the second motor is inputted to a third input terminal of the first comparator and a fourth input terminal of the second comparator,
wherein the first comparator compares the first threshold voltage with the first back electromotive force, and the second comparator compares the second threshold voltage with the first back electromotive force,
wherein the back electromotive force detecting circuit detects the first back electromotive force, and the brake control circuit judges a movement speed of the magnetic head based on comparison results of the first comparator and the second comparator when a first power supply to the magnetic disk storage apparatus is stopped,
wherein if the first comparator determines that the first back electromotive force detected when the first power supply to the magnetic disk storage apparatus is stopped is greater than the first threshold voltage, the brake control circuit judges the movement speed being greater than the first preset speed and the brake control circuit brakes the second motor,
wherein if the second comparator determines that the first back electromotive force detected when the first power supply to the magnetic disk storage apparatus is stopped is greater than the second threshold voltage, the brake control circuit determines the movement speed being greater than the second preset speed and the brake control circuit brakes the second motor,
wherein the retract control circuit is adapted to drive the second motor to move the magnetic head to a retract position after the brake control circuit braking the second motor when the first power supply to the magnetic disk storage apparatus is stopped,
wherein when a predetermined time elapses after the first power supply to the magnetic disk storage apparatus is stopped, the brake control circuit judges the movement speed of the magnetic head based on comparison results of the first comparator and the second comparator.
2. The magnetic disk storage apparatus according to claim 1 , wherein the retract control circuit drives the second motor to move the magnetic head to the retract position at a speed being smaller than a predetermined speed, when the first power supply to the magnetic disk storage apparatus is stopped.
3. The magnetic disk storage apparatus according to claim 2 , wherein in a first operation, the brake control circuit brakes the second motor, and in a second operation, the back electromotive force detecting circuit detects the first back electromotive force,
wherein the first operation and the second operation are repeated alternately, until the movement speed when the first power supply to the magnetic disk storage apparatus is stopped becomes smaller than the first preset speed, and
wherein the first operation and the second operation are repeated alternately, until the movement speed when the first power supply to the magnetic disk storage apparatus is stopped becomes smaller than the second preset speed.
4. The magnetic disk storage apparatus according to claim 2 , further including a setting circuit for setting judgment levels of the first threshold voltage and the second threshold voltage in order to judge the movement speed of the magnetic disk.
5. The magnetic disk storage apparatus according to claim 1 , wherein when the first power supply to the magnetic disk storage apparatus is stopped, the second motor, the second motor driving control circuit, the back electromotive force detecting circuit, the brake control circuit, and the retract control circuit are supplied a second power supply from a second back electromotive force of the first motor.
6. The magnetic disk storage apparatus according to claim 5 , further comprising a plurality of diodes for rectifying currents caused by the second back electromotive force of the first motor.