Stmicroelectronics S.r.l.

Roberto Peritore

Andrea Merello

Gianluca Ventura

Ezio Galbiati

Alberto Salina

Michele Bartolini

Agostino Mirabelli

Lorenzo Papillo

Francesco Vavala

A device for the change of the driving mode of an electromagnetic load from a first operating mode with pulse width modulation to a second operating mode that is linear by means of switching circuits. During a first operating mode, each of two outputs has a voltage value ranging from a first reference voltage to a second reference voltage. The device adapted to synchronize a change command signal from a first operating mode to a second operating mode of the electromagnetic load with the signal representative of the flow of current circulating within the load at substantially its average value and adapted to generate a first command signal in response to the synchronization.

Device to synchronize the change of the driving mode of an electromagnetic load

A system for controlling and driving an electromagnetic actuator includes a unique operational amplifier in the regulation loop for driving the electromagnetic actuator and for monitoring, during different phases of operation, the current in the actuator and the back electromotive force. The new architecture allows for a considerable reduction of the area of integration of the system as a whole.

Control and drive system for a single winding electromagnetic actuator employing a single multifunction operational amplifier

The present invention relates to the positioning of the read/write transducer heads of an hard disk (HD) in a designated landing zone when requested or when the electrical power is removed from the drive. In particularly it relates to the detection of the back electromotive force (BEMF) of the motor involved in the positioning of the read/write transducer heads. According to an embodiment of the present invention a BEMF detection circuit for a voice-coil motor operative to continually generate a signal proportionally to the velocity of said voice-coil motor comprises a algebraic summing node producing at its output the BEMF of the voice-coil motor and receiving: a first voltage proportional to the voltage across the voice-coil motor; a second voltage representing the product of a first multiplier factor and a voltage proportional to the current in the coil; a third voltage representing the product of a prefixed bias voltage Vref and a second multiplier factor; said third voltage is calibrated by a single calibration circuitry operative to calibrate said second multiplier factor in response to a calibration control signal, in order to cancel said second voltage.

Calibration technique of a BEMF detector

A method for controlling an electromagnetic actuator having an arm connected thereto uses a circuit that temporarily places in a high impedance state output nodes connected to a winding of the electromagnetic actuator. A detected BEMF is compared with a lower threshold and an upper threshold. Current in the electromagnetic actuator is monitored and controlled. A current pulse is provided to the electromagnetic actuator based upon the comparison of the detected BEMF with the lower and upper thresholds. The respective amplitudes of successively provided current pulses having a same polarity are progressively increased, and an amplitude of a provided current pulse having a polarity opposite a polarity of a preceding current pulse is decreased. The amplitude of the driving current pulses provided to the winding of the electromagnetic actuator advantageously adapts automatically to varying frictional conditions, or to any other cause of variation of the mechanical load of the actuator. These conditions occur when the arm moved by the electromagnetic actuator starts to slide up or flies off the parking ramp.

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Trezzano Sul Naviglio, Italy

Roberto Peritore