Method of operating hard disk drives and corresponding control circuit

A control circuit for a voice coil motor in a hard disk drive having a spindle motor, wherein the control circuit is configured to:

• rectify a back electromotive force of the spindle motor in the hard disk drive;
• energize a voice coil motor in the hard disk drive using the rectified back electromotive force of the spindle motor via a voice coil motor power stage to retract a head of the hard disk drive to a park position, wherein the head is retracted by moving the head towards the park position during a first retract phase and retaining the head in the park position during a second retract phase by applying a bias voltage to the voice coil motor power stage during a bias interval of the second retract phase;
• produce a saturation signal indicative of onset of saturation in the voice coil motor power stage;
• and
• control the bias voltage during the second retract phase based on the saturation signal to counter saturation in the voice coil motor power stage.

A control circuit for a voice coil motor in a hard disk drive having a spindle motor, the control circuit comprising:

• a regulator coupled to windings of the spindle motor, the regulator being configured to rectify a spindle current of a back electromotive force of the spindle motor;
• a capacitor coupled between an output of the regulator and a reference node;
• and
• a voice coil motor power stage coupled between the output of the regulator and the reference node, the voice coil motor power stage being configured to drive the voice coil motor using the rectified spindle motor current to retract a head of the hard disk drive to a park position;
• wherein the retracting of the head comprises moving the head towards the park position during a first retract phase, and retaining the head in the park position during a second retract phase by applying a bias voltage to the voice coil motor power stage during a bias interval of the second retract phase;
• wherein the voice coil motor power stage is configured to produce a saturation signal indicative of onset of saturation in the voice coil motor power stage;
• and
• wherein the voice coil motor power stage is configured to control the bias voltage during the second retract phase based on the saturation signal to counter saturation in the voice coil motor power stage.