Electrical circuit for ultrasonic cleaning device - incorporates pulse width modulation for regulating power output resonance frequency

摘要

The electrical circuit has an ultrasonic generator and an ultrasonic transducer, the ultrasonic generator having a power end stage (6) supplying a HF transformer (5) and the ultrasonic transducer using a piezoelectric element (8) which is caused to oscillate at an ultrasonic frequency, upon application of the HF voltage. The power output of the ultrasonic generator is varied via pulse width modulation of the HF voltage to maintain a constant power output, using comparison of the actual and required power output levels and supplying the difference to an end stage control device (17). The resonance frequency of the oscillating system is held constant by a regulating circuit comparing the voltage and current phases for the transducer element, to detect a resonance shift, with subsequent correction of the frequency of the HF voltage. ADVANTAGE - Allows max. cleaning efficiency to be maintained.