Research On Automatic Impedance Maching Technology Of Magnetostrictive Transducer Power Supply Based On DSP By Wang Chao

Magnetostrictive transducer is a kind of energy conversion device which using the magnetostrictive effect of materials.It is used in low frequency acoustic transducer,liquid level detection,precision actuator,etc.In recent years,the magnetostrictive transducers which use Terfenol-D,Fe-Ga materials as its actuating element become a research hotspot.For the influence of material's nonlinear,working temperature,load changing and other factors,the equivalent circuit parameters and resonant frequency of the transducer will be changed.It will result in the decrease of the working efficiency and output performance.The driving ability of the power supply is closely related to the transducer's working efficiency and output performance.So the research of power supply is of great significance in promoting the development and application of transducer.In this paper,based on the Terfenol-D transducer,the typical structure of the transducer is analyzed.Based on the PWM inverter power supply and combined with the DSP chip,a magnetostrictive transducer drive power supply with automatic impedance matching function is designed.The power supply uses AC220 V as input,output the square wave voltage which frequency from100 Hz to 2000 Hz and with the continuously adjustable peak.Firstly,based on the typical structure of the magnetostrictive transducer,the equivalent circuit analysis is carried out.The working principle of the series resonant circuit and the parallel resonant circuit is compared and analyzed by the vector method.The necessary conditions for the normal operation of the two circuits are summed up.The basic form of impedance matching circuit is determined.Combining with the quality factor and frequency-selective network band-pass,we make the optimized design of matching control program flow and matching capacitor selection.Then,based on the structure of DSP chip,we design an impedance matching system composed of four main parts: master chip,voltage and current signal acquisition circuit,matching capacitor and actuator.After the theoretical analysis combined with the experiment,the working flow of the impedance matching program is designed,and the frequency closed loop is realized by controlling the matching capacitance by the DSP chip,thus improving the power output efficiency and the quality of the load current waveform.Finally,the basic topology of the main circuit is determined,and the overall design of the drive power is designed.It includes uncontrolled bridge rectifier circuit,filter circuit,MOSFET driver circuit,optical coupling isolation circuit,level conversion circuit,basic power supply and heat dissipation control.The prototype circuit is composed of PWM signal,drive circuit output signal,main circuit output and phase signal acquisition circuit.The experiment of the power supply using to drive the inductor coil and the low frequency transducer are carried out.The switching of the matching capacitor can meet the load power demand.The magnetostrictive transducer can work in the resonant state in real time,and the sine degree and peak value of the load current are improved.