Oscillatory circuit for an ultrasonic cleaning device with feedback from the piezoelectric transducer

Claim 1

In an oscillatory circuit for an ultrasonic generator including a rectifier and filter network for providing a rectified voltage, a transistor network having a pair of transistor arrangements coupled to said rectifier and filter network and in series to each other and connected to inputs of a radio frequency transformer so that said transistor arrangements are cyclically rendered conductive in mutual opposition, and in which outputs of the radio frequency transformer are coupled through a series connected power inductance across piezoelectric ultrasonic transducer means, the improvement comprising feedback network means coupled in series with said ultrasonic transducer means and including a resistance series connected to said ultrasonic transducer means, and a capacitance, a feedback inductance, and a feedback transformer series connected to each other and in parallel with respect to said resistance for alternatively driving each of said transistor arrangements and for providing a variable phase shift in driving current thereto tending to hold the cyclic operation of said transistor arrangements at a target frequency.