Image Number 2 for United States Patent #4888565.
An ultrasonic generator, particularly for use in ultrasonic cleaning systems, provides a constant ultrasonic power output for a cleaning tank or chamber. A generator output stage fed from an unsmoothed mains power supply receives signals from an oscillator via a pulse-width modulation circuit. A power control feedback loop monitors the mains current, or alternatively the output signal from the output stage, and provides a compensation signal to the pulse-width modulation circuit. A frequency control feedback loop senses the current in the output from the output stage and tunes the generator for maximum current in this output.