Disk drive controlling ripple current of a voice coil motor when driven by a PWM driver
AssigneeWestern Digital Technologies, Inc.
InventorGeorge J. Bennett
Life of this patent
Estimating the term…
Abstract
A disk drive is disclosed comprising a pulse width modulated (PWM) signal generator for generating PWM control signals applied to the driver switches of a voice coil motor (VCM). The PWM control signals comprise a PWM cycle time, a Tforward time interval of the PWM cycle time wherein a positive control voltage is applied to the VCM, a Treverse time interval of the PWM cycle time wherein a negative control voltage is applied to the VCM, and a Tdead time interval of the PWM cycle time wherein a substantially zero control voltage is applied to the VCM. The Tdead time interval is adjusted to control a magnitude of an actual ripple current flowing through the VCM.
Claims22
A disk drive comprising:
- (a) a disk;
- (b) a head;
- (c) a voice coil motor (VCM) for actuating the head radially over the disk, the VCM comprising a voice coil;
- (d) a plurality of driver switches for controlling a voltage applied to the voice coil;
- and
- (e) a pulse width modulated (PWM) signal generator for generating PWM control signals applied to the driver switches, the PWM control signals comprising:
- a PWM cycle time;
- a Tforward time interval of the PWM cycle time wherein a positive control voltage is applied to the voice coil;
- a Treverse time interval of the PWM cycle time wherein a negative control voltage is applied to the voice coil;
- and
- a Tdead time interval of the PWM cycle time wherein a substantially zero control voltage is applied to the voice coil, wherein the Tdead time interval is adjusted to control a magnitude of an actual ripple current flowing through the voice coil.
A method of controlling ripple current in a voice coil motor (VCM) of a disk drive when driven in a PWM mode, the disk drive comprising a disk, a head, and the VCM for actuating the head radially over the disk, wherein the VCM comprise a voice coil, the method comprises the steps of:
- (a) computing a Tforward time interval of a PWM cycle time;
- (b) applying a positive control voltage to the voice coil during the Tforward time interval;
- (c) computing a Treverse time interval of the PWM cycle time;
- (d) applying a negative control voltage to the voice coil during the Treverse time interval;
- (e) computing a Tdead time interval of the PWM cycle time;
- (f) applying a substantially zero control voltage to the voice coil during the Tdead time interval;
- and
- (g) adjusting the Tdead time interval to control a magnitude of an actual ripple current flowing through the voice coil.
Dependencies are inferred from the claim text.