Importance

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Abstract

An energizing circuit (10) for automatically driving a piezoelectric crystal transducer (Y1) at its resonant frequency includes a resonant circuit (12) of which the transducer (Y1) forms a capacitive element and the secondary winding (80) of a transformer (T2) forms an inductive element. In addition, the piezoelectric crystal itself acts as a series RLC circuit disposed in parallel with the parallel capacitive and inductive elements of the resonant circuit (12). Secondary winding (80) is inductively coupled with a primary winding (74) of the transformer (T2) which forms part of a driving circuit (14). The driving circuit (14) includes a switching circuit (20) connected between a power supply circuit (16) and the resonant circuit (12). Driving circuit (14) also includes a control circuit (28) which senses the difference between the vibrational frequency of transducer (Y1) and its resonant frequency and produces an appropriate level control signal which is transmitted to an oscillatory circuit (24) which in turn produces a switching signal of the desired frequency to actuate the switching circuit (20) at the proper rate to drive resonant circuit (12) at the resonant frequency of transducer (Y1) through the inductive coupling formed by transformer (T2).

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First Claim