Faster spin-down operation in a disk drive by utilizing pulsed braking

A disk drive comprising:

• a spindle motor having a plurality of windings and a rotor rotatable at a variable magnitude rotational velocity;
• a spindle motor driver including switching elements connected to the plurality of windings;
• means for producing a speed-indicating signal representing the magnitude of the rotational velocity;
• means for storing spin-down instructions;
• means for initiating a spin-down command;
• a microprocessor responsive to the spin-down command to receive and execute the spin-down instructions, wherein the execution of the spin-down instructions causes the microprocessor to perform the following cycle and sub-cycle operations of:
• cyclically reading the speed signal to determine whether the magnitude of the rotational velocity is within a range bounded by a selected upper rotational velocity (.omega.1) and a second selected lower rotational velocity (.omega.2);
• within each cycle in which the magnitude of the rotational velocity is determined to be in the range, cyclically executing the following subcycle operations of:
• (1) providing a brake signal for a first selected period of time (T1),
• (2) providing a coast signal for a second selected time period (T2), and
• (3) repeating (1) and (2);
• within each cycle in which the magnitude of the rotational velocity is determined to be lower than the range, executing the following subcycle operation:
• (1) providing the brake signal;
• and
• the spindle motor driver being responsive to the coast signal to control the switching elements to cause the spindle motor to coast and being responsive to the brake signal to control the switching elements to brake the spindle motor.

A method for spinning down a spindle motor in a disk drive, the method comprising the steps of:

• a. initiating a spin-down operation;
• b. monitoring a rotational velocity of the spindle motor;
• c. while the monitored rotational velocity of the spindle motor is less than a first selected rotational velocity (.omega.1) and greater than or equal to a second selected rotational velocity (.omega.2):
• (1) braking the spindle motor with a braking mechanism for a first selected period of time (T1),
• (2) coasting the spindle motor for a second selected period of time (T2), and
• (3) repeating steps c(1) and c(2);
• and
• d. selecting .omega.2 to be a safe braking rotational velocity such that substantially no heat related breakdown of any portion of the spindle motor and the breaking mechanism occurs when the spindle motor is repeatedly braked for T1 and coasted for T2 at velocities in the range, and continuously braked for time periods greater than T1 at rotational velocities less than .omega.2.

A method for spinning down a spindle motor in a disk drive, the method comprising the steps of:

• a. monitoring a rotational velocity of the spindle motor;
• b. storing spin-down instructions;
• c. initiating a spin-down operation in a microprocessor, the spin-down operation including receiving and executing the spin-down instructions to cause the microprocessor to perform the following steps:
• (1) reading the monitored rotational velocity of the spindle motor;
• and
• (2) while the monitored rotational velocity of the spindle motor is less than a first selected rotational velocity (.omega.1) and greater than or equal to a second selected rotational velocity (.omega.2):
• (i) providing a brake signal for a first selected period of time (T1),
• (ii) providing a coast signal for a second selected time period (T2), and
• (iii) repeating steps c(2)(i) and c(2)(ii);
• d. coasting the spindle motor in response to the coast signal;
• and
• e. braking the spindle motor in response to the brake signal.