Staircase-Voltage Metal--Oxide--Semiconductor Field-Effect Transistor Driver Circuit for Therapeutic Ultrasound

An important component of all ultrasound systems is the high-voltage pulse generator used to excite the transducer. We created a new type of metal--oxide--semiconductor field-effect transistor (MOSFET) switching circuit for therapeutic ultrasound applications, on the basis of the staircase-voltage drive concept. The staircase drive can significantly decrease the harmonics in comparison with the conventional square-wave drive. Since it does not require a resonant circuit to improve the efficiency, the drive frequency can be freely changed and the total size of the drive circuit can be made smaller. Using a diode in series to the drain of each MOSFET, a staircase-voltage driver was created with a relatively simple configuration. The experimental results of operating a prototype driver, as well as the results from circuit simulation, are discussed.