Patent ID: 6040671
Filing Date: 2000-03-21
Classification: H02P,Y10S

Abstract:
An apparatus for controlling an actuator having a moveable member and having a coil that influences movement of the member, by provision of a drive current to said coil in response to a target speed voltage signal, comprising:an up/down counter, counting at a predetermined count rate and providing a count output;a control unit for controlling the direction of count of said up/down counter depending on whether the voltage across said coil, sensed periodically a first predetermined interval after said drive current to said coil is interrupted, is greater than, or less than, a reference voltage having a predetermined relationship to said target speed voltage;a digital-to-analog converter responsive to said count output to provide a compensated voltage signal having a voltage corresponding to said count output;a voltage sensing and holding unit that periodically, after said drive current is interrupted for a second predetermined interval, senses and holds a sample voltage corresponding to the voltage across said coil;a plus/minus indicator that senses when said up/down counter is in a down count direction and is at a count of zero, and in response thereto changes between a plus state and a minus state;a switch node combining said sample voltage signal with said compensated voltage signal to produce a command voltage signal, and providing said command voltage signal with a polarity controlled by the state of said plus/minus indicator; anda transconductance amplifier unit, receiving said command voltage signal and providing said drive current to said coil in a direction determined by the state of said plus/minus indicator.