Disk drive comprising oscillators and counters for sensing current in a voice coil motor
AssigneeWestern Digital Technologies, Inc.
InventorGeorge J. Bennett
Life of this patent
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Abstract
A disk drive is disclosed comprising a voice coil motor (VCM) driver including an H-bridge driver having a first sense resistor connected in series with a supply voltage and a second sense resistor connected in series with ground. First and second amplifiers amplify the voltages across the first and second sense resistors, wherein the output of the amplifiers drive respective first and second oscillators. A counter processes the frequency signals output by the oscillators to generate a digital representation of the current flowing through the voice coil of the VCM.
Claims12
A disk drive comprising:
- (a) a disk;
- (b) an actuator arm;
- (c) a head connected to a distal end of the actuator arm;
- (d) a voice coil motor (VCM) comprising a voice coil, the VCM for rotating the actuator arm about a pivot to actuate the head radially over the disk;
- and
- (e) a VCM driver comprising:
- an H-bridge driver comprising a plurality of driver switches for driving current from a supply voltage through the voice coil to ground;
- a first sense resistor connected in series between the supply voltage and at least one of the driver switches;
- a first amplifier for amplifying a voltage across the first sense resistor to generate a first sense signal;
- a second sense resistor connected in series between at least one of the driver switches and ground;
- a second amplifier for amplifying a voltage across the second sense resistor to generate a second sense signal;
- a first oscillator for generating a first frequency signal in response to the first sense signal;
- a second oscillator for generating a second frequency signal in response to the second sense signal;
- and
- a first counter responsive to a reference frequency, the first frequency signal, and the second frequency signal, wherein an output of the first counter represents a current flowing through the voice coil.
A method of operating a disk drive, the disk drive comprising a disk, an actuator arm, a head connected to a distal end of the actuator arm, a voice coil motor (VCM) comprising a voice coil for rotating the actuator arm about a pivot to actuate the head radially over the disk, and an H-bridge driver comprising a plurality of driver switches for driving current from a supply voltage through the voice coil to ground, the method comprising the steps of:
- amplifying a voltage across a first sense resistor to generate a first sense signal, the first sense resistor being connected in series between the supply voltage and at least one of the driver switches;
- amplifying a voltage across a second sense resistor to generate a second sense signal, the second sense resistor being connected in series between at least one of the driver switches and ground;
- generating a first frequency signal in response to the first sense signal;
- generating a second frequency signal in response to the second sense signal;
- counting periods in the reference frequency, the first frequency signal, and the second frequency signal, to generate a first count representing a current flowing through the voice coil.
Dependencies are inferred from the claim text.