Electricity: motive power systems – Synchronous motor systems – Brushless motor closed-loop control
Reexamination Certificate
2011-03-08
2011-03-08
Benson, Walter (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
Brushless motor closed-loop control
C318S400320, C318S400010, C318S700000, C360S075000
Reexamination Certificate
active
07902778
ABSTRACT:
A disk drive system including retract logic for control of the voice coil motor in a retract operation, in which the voice coil motor positions the read/write head actuator arm in a safe place in a loss-of-power event, is disclosed. The retract logic includes circuitry for controlling the application of power to the voice coil motor from an external capacitor, so that a constant voltage is maintained across the voice coil motor. Current from the capacitor is directed to an internal variable resistor that conducts a selected current, in parallel with the current applied to the voice coil motor. The voltage developed across the variable resistor is applied to one input of a control amplifier, which receives the voltage across the voice coil motor at another input; the control amplifier in turn controls the gate of a low side transistor. The transistor passes current to the extent that the voltage across the voice coil motor corresponds to that developed across the variable resistor.
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Copending U.S. Appl. No. 11/323,800, filed Dec. 30, 2005.
Copending U.S. Appl. No. 11/758,872, filed Jun. 6, 2007.
Ota Chisako
Yamashita Masaki
Benson Walter
Brady III Wade James
Luo David S
Stephens Dawn V.
Telecky , Jr. Frederick J.
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