Design Of Driving Power For High Frequency Ultrasonic Physiotherapy Instrument

At present,the detection of ultrasound is widely used in medical field.The application of power ultrasound in medical field is relatively small,in the research stage such as ultrasound knife,targeted drug delivery.Therapeutic effect of ultrasound has been widely recognized,but the driving power of physiotherapy instrument defects still exist.As the frequency of ultrasound therapy is mostly higher than 1MHz,if using the linear amplifier to achieve power amplification,there will be most questions such as whether output power can be adjusted,the output voltage waveform distortion.In practical applications,it is difficult to achieve accurate matching only by the matching network of ultrasonic power supply.And because of the transducer heating,adhesive,aging and other factors led to resonant frequency changes.So the ultrasonic power supply is required to track the resonant frequency of the transducer so as to avoid a large loss of energy as well as to further heat.In this dissertation,with reference to the research status of high-frequency low-power ultrasonic power supply at home and abroad,aiming at the existing problems,the overall architecture of digital ultrasonic power supply is designed with the driving frequency of 1MHz and the output power of 10 watts.According to the electrical equivalent model of the transducer,the static matching network is designed and the parameters of the components are calculated.The phase difference detection methods such as the FFT transform method,the correlation function method and the zero-crossing comparison method are analyzed and compared.The suitable phase difference detection method is selected and the related detection circuit is designed.The power amplifier based on LCC power resonant inverter is adopted,and each modules of the resonant inverter are analyzed,and the calculation method of the parameters of the LCC resonant inverter is given by using the circuit theory and other knowledge.Compared with the usual power regulation method of the switching power supply,PDM method is introduced to realize adjustable output power.Aiming at the drift of the resonant frequency of the physical therapy transducer,the frequency self-tracking function is introduced,which makes the transducer always in resonance state.The algorithm of frequency point search in the engineering application is improved and its deficiency is pointed out.Furthermore,due to the transducer has complex nonlinearity and no precise mathematical model,a fuzzy controller based frequency tracking algorithm is proposed.The simulation model of the frequency tracking algorithm based on the fuzzy controller is built by using the fuzzy toolbox and Simulink simulation platform in Matlab.The simulation results show that the fuzzy control can quickly to achieve frequency tracking.The experimental results show that the driving system based on LCC resonant inverter and fuzzy phase locked loop can drive the transducer efficiently and realize the voltage and current in phase.The system can be safe,stable and continuous operation.