Abstract: An aspiration control system includes a proportional control valve and a motor, for driving a vacuum pump, which are controlled by a system controller in accordance with input commands to provide a precise, continuously variable vacuum or negative pressure within a vacuum chamber and surgical handpiece. A pressure transducer samples the vacuum output and produces a signal which is fed to the system controller. The signal is compared with an input command, and the motor speed and valve orifice size are coordinated to control the vacuum level.

Abstract: An electronic control system for determining the resonant frequency of and driving ultrasonic transducers in a phacoemulsification probe used for ophthalmic surgery. The control system includes a voltage control led oscillator, power amplifier, power monitor, and automatic gain control circuit operating under the direction of command signals received from a microprocessor-based control console. The control system operates in a constant apparent power, direct drive mode with closed loop feedback maintaining the electrical power provided to the primary of a RLC transformer at the constant level requested by the command signals from the console. The frequency of the drive signal is held at the dominant resonant frequency of the ultrasonic transducer which is being driven by the control system. This resonant frequency is determined via a calibration procedure performed when the probe is first attached to the control system.