Design of an Automatic Resonance Frequency Tracking Chip for Power Ultrasonic Transducer with a Centre Frequency Below 100KHz

This paper presents a chip for automatic resonance frequency tracking of power ultrasonic transducer. The transducer admittance and the phase difference of voltage and current are both used for frequency tracking, which solves the disadvantages of narrow frequency tracking range, long tracking time, and easy losing frequency lock in the traditional circuit scheme. Using the transducer voltage signal as the clock, the chip can respond to the transducer signal in every cycle, then maximize the frequency tracking speed, and the total frequency tracking time is less than 10ms. A 12-bit digital-to-analog convertor (DAC) is built to control the off-chip voltage controlled oscillator (VCO), the frequency tracking accuracy can reach 0.2‰. Compared with the traditional scheme, it greatly improves the performance and saves the hardware cost.