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# Hard Disk Drive Actuator Auto-Landing Zone Circuit

IP.com Disclosure Number: IPCOM000035884D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 41K

IBM

## Related People

Lee, S: AUTHOR [+2]

## Abstract

Disclosed is a circuit for an auto-head parking function of a hard disk drive. The auto-head function involves moving an actuator arm to an inner side or an outer side of a disk where a power supply is turned off. To achieve it, this circuit uses the kinetic energy of a spindle motor for driving disks. This circuit provides the electric current of a coil of a spindle motor to a VCM (Voice Coil Motor) at the moment when the power supply is turned off.

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Hard Disk Drive Actuator Auto-Landing Zone Circuit

Disclosed is a circuit for an auto-head parking function of a hard disk drive. The auto-head function involves moving an actuator arm to an inner side or an outer side of a disk where a power supply is turned off. To achieve it, this circuit uses the kinetic energy of a spindle motor for driving disks. This circuit provides the electric current of a coil of a spindle motor to a VCM (Voice Coil Motor) at the moment when the power supply is turned off.

The figure is a diagram of the auto-landing zone circuit. This circuit consists of the following three portions.

(1) A portion, comprising a resistor (1kL), diode and capacitor (47mF), which stores up electrical charges. These charges are used for switching the following transistor and the FET (field-effect transistor).

(2) A transistor (a) which acts as a current limiter. The maximum electric current which flows to the VCM coil at power off is described as I = (Vo/R1) * hfe where I :Maximum VCM current at power off Vo : Voltage of electric charge

R1 : Resistance at base of transistor (a)

hfe : Static forward current transfer ratio of

transistor (a)

(3) A current switch which consists of two FETs. These FETs act at the moment when the power supply is turned off and the power-off signal becomes low level. By using the character of the FET whose input impedance is very high, it becomes possible to extend the period of FET switching time.

The performance of this circuit...