Designs Of Ultrasonic Driver Circuit Based On The Third Harmonic Frequency Tracking Method

Ultrasound as a branch of acoustics, the rapid development in recent years. Ultrasonicwave has adirection, transmission of good acoustic properties, ultrasonic energy concentration,gas, solid and liquid are better dissemination of. Widely used in ultrasonic detection,ultrasonic inspection, ultrasonic vibration, ultrasonic extraction etc..The application ofultrasonic in different direction can be divided into: detection of ultrasonic, ultrasonic power。Ultrasonic by ultrasonic transducer inverse piezoelectric effect, in the use of power ultrasonictransducer in the process, the effects due to changes in load, transducer aging, wear, fatigue,Wen Sheng and other factors, the resonance frequency of transducer often produce offset。Howto dynamically track the resonance frequency of the transducer has become a researchhotspot in the field of ultrasonic application.Based on the ultrasonic frequency tracking technique based on the comparison andanalysis, the improvement of the existing frequency tracking driving circuit, the design of atracking technique of ultrasonic transducers based on the three harmonic frequency.According to the different signal sampling feedback, can better get the series resonantfrequency transducer transducer, improve the electromechanical coupling coefficient. Thedesign of the driving signal circuit basis, an increase of three times harmonic samplingfeedback circuit, the sampling and quantization of three harmonic voltage and current gain,phase difference and amplitude information, provides the calculating parameter matchingnetwork for the output signal frequency and impedance. The circuit mainly includes: signalgenerating circuit, PWM signal modulation circuit, inverter output circuit, impedancematching network and a feedback control circuit. The feedback control circuit includes: asampling circuit, a high pass filtering circuit, the three harmonic voltage and currentproportion amplifying circuit, phase difference detection circuit and A/D conversion circuit.According to the requirements of various circuit parameters, this paper adopts Proteus,Multisim simulation testing of each module design。Under typical conditions (temperature of300K), signal generating circuit outputs the frequency range of15KHz~70KHz, thesensitivity is less than or equal to1Hz;PWM signal modulation circuit adopts fixed frequencywidth adjustment mode, the amplitude of the input signal0~5V, duty ratio0~100%stepless adjustable PWM modulation signal; The high pass filter circuit in the f=4/9fT, requirementsfor amplitude attenuation greater than40dB. By setting the ultrasonic transducer equivalentcircuit parameters simulation model for system simulation. Simulation results show that thedriver circuit designed in this paper implements the automatic tracking frequency, the systemtracks the frequency of the maximum deviation of0.89%.