Research On Class E High Frequency Power Supply Used In Ultrasonic Therapy Instrument

Since the discovery of piezoelectric effect and the anti-piezoelectric effect in the late 1900's,the application of ultrasound has been rapidly developed and popularized,and one of the important applications is ultrasonic physiotherapy.Ultrasonic power supply is used to drive the transducer in ultrasonic physiotherapy apparatus,which is a key device in ultrasonic physiotherapy apparatus.This paper mainly discusses the E-class high frequency power supply used in ultrasonic physiotherapy apparatus.Firstly,this paper introduces the basic structure of E-class power amplifier,deduces the working principle and parameter calculation of E-class power amplifier.In order to realize the working condition adjustment of E-class power amplifier,this paper analyzes the influence of non-ideal factor and load network parameter change on the working state of E-class power amplifier,obtains and analyzes three kinds of working state of Class E power amplifier,and pointing out that e-class power amplifier should avoid working in disorder state.This paper introduces the equivalent circuit of transducer and analyzes the impedance circle characteristic of transducer.Considering the source impedance characteristics and output harmonic characteristics of the E-class power amplifier,this paper analyzes he corresponding matching circuits for the capacitive and inductive workload of the transducer.This paper points out that the transducer should work in the inductive load frequency band when the E-class power amplifier drives the transducer,and the parallel capacitance matching circuit should be adopted.Because different transducers of the same model vary in impedance and working frequency,and the impedance of the same transducer can be changed due to aging.This paper designed an on-line transducer impedance measurement scheme to solve the matching problem of the E-class power amplifier when driving different transducers.Aiming at the poor adaptability of E-class power amplifier to load network,this paper designs and implements on-line active adjustable inductance and active adjustable capacitance to adjust the working state of E-class power amplifier in real time,and to avoid its working in disorder state,which solves the problem of poor adaptability of E-class power amplifier to load network.The author of this paper constructed a set of 60 W,1MH ± 5% ultrasonic power supply system,and analyzed waveforms of different working states.The experimental results validate this paper's theoretical analysis.