Abstract: A capacitor discharge retract system is provided for small disk drives wherein the small spindle size is incapable of generating enough electrical energy to enable conventional actuator retraction and the form factor is too small to accommodate capacitors of sufficient size to enable a conventional capacitive discharge system. A capacitive discharge retract technique is enabled using an elevated voltage, significantly above the disk drive supply voltage, to allow smaller capacitive storage elements to perform the function. The effectiveness of the system is further enhanced in those environments where a source of the required elevated voltage can be found already resident in the device circuitry where it was generated to support another function.

Abstract: A digital storage system is disclosed in which a flying read/write head is loaded onto the surface of moving storage media with controlled velocity to avoid contact with the surface of the storage media. Head load velocity is detected by measuring the back EMF generated by the head arm actuator. Improved control and accuracy is obtained by breaking up the head arm actuator drive power into a series of pulses and measuring the back EMF induced into the low impedance voice coil of the head arm actuator in between pulses but only after the actuator current has been reduced to substantially zero in order to avoid interference by actuator current induced voltages.