An integrated full-bridge Class-DE ultrasound transducer driver for HIFU applications

Abstract

This thesis present a CMOS integrated transducer driver for high intensity focused ultrasound (HIFU) applications. Because this driver will be used in a magnetic resonance imaging (MRI) environment, no magnetic components such as inductors and transformers have been used in this design. The transducer is directly connected to the driver without a matching network. The output stage of this driver is a full-bridge Class DE RF amplifier which is able to deliver more power than the previous design that has a half-bridge Class DE amplifier.The driver was also designed to be used in a transducer array. A digital control unit was integrated with the power amplifier that allows to program the drivers phase shift and duty ratio.A strategy to drive a ultrasound transducer array using the designed driver is also presented in this thesis.This design was implemented using the AMS H35B4 CMOS technology using the Cadence suite of design tools and occupies a die area of 2mm by 1.5mm with 20 input and output pads. Simulation and initial experimental results are presented in this work. The proposed integrated CMOS driver has an efficiency of 89.4% with 3.60 W of output power. Results are little bit different for each transducer. I I also would like to thank my family for their encouragement, patience and understanding.

Power Efficiency Characterization with Various Gate Oxide Thicknesses in Class DE Amplifiers for HIFU Applications

“…In the case of the class DE amplifier, switching of the amplifier was performed according to the transducer's resonance frequency. The series inductance (Ls), series capacitance (Cs), series resistance (Rs), and parallel capacitance (Cp) of the piezoelectric transducer-equivalent model of a single-element structure for the simulation were 315 μH, 90 pF, 55 ohm, and 950 pF, respectively [30]. Using a class DE amplifier is a method that actively utilizes the resonance frequency of the load.…”

“…However, it operates in a push-pull type manner, and its power efficiency is lower than that of the class B topology. However, in the case of a single element, a class DE power amplifier can achieve a power efficiency of approximately 90% [28][29][30]. This is possible because in the case of switched amplifiers, the power loss can be reduced through zero-voltage switching (ZVS) with the assistance of zero-derivative switching (ZDS) operation.…”