Control of ultrasonic vibratory transducer - has phase comparator maintaining oscillator frequency equal to resonance frequency

摘要

The transducer has a resonant circuit, and is controlled by a voltage or current controlled oscillator (3). A voltage is derived corresponding to the phase of the current supplied to the transducer. This voltage is applied to a phase comparator (1) as a first input signal, whose second input signal is the transducer driving voltage. The voltage or current controlled oscillator is controlled by the phase comparator output signal in accordance with the phase difference between its two input signals. This results in the transducer driver frequency being always equal to the resonance frequency.