DESIGN OF A CLASS-E INVERTER FOR PIEZOELECTRIC ULTRASOUND GENERATION AGAINST LOAD VARIATION

Piezoelectric transducers are used for generating ultrasound around their resonant frequencies. Single-ended class-E resonant inverter has a simple configuration and high conversion efficiency; therefore, was investigated for driving piezoelectric transducer for ultrasound generation. However, both piezoelectric transducer and class-E circuit are sensitive to load variation. This paper studies the susceptibility of output power and conversion efficiency of a class-E based piezoelectric ultrasound generator under different load conditions. By using the iteration-free extended impedance method, the integration of class-E inverter and piezoelectric transducer can be efficiently analyzed; parameters can be properly designed and optimized. An in-situ adapting approach, which tunes the duty ratio and dc supply voltage for maximizing the conversion efficiency at constant output power against load variation, is investigated. Simulation results show that, by taking this parameter tuning, the susceptibility of output power and conversion efficiency can be alleviated within a wide range of load.