Abstract

Medical imaging, specifically ultrasound, is undergoing a significant transformation. A smart probe ultrasound scanner is a handheld device that visualizes internal organs of the human body and their size using advanced technology. The high degree of integration in front-and back-end units within a handheld device brings the designers face-to-face with challenges like power dissipation, thermal performance, size constraints and noise immunity. This application note provides a solution to efficiently power ultrasound transmitters. This design generates bipolar programmable high voltage (HV) up to ±80 V from a very low voltage source. It can deliver continuous average power of 2-W on each rail. A Single-Ended Primary-inductor Converter (SEPIC) topology with uncoupled inductors is preferred over transformer based flyback converter in order to accomplish the critical height requirement (<5 mm). It features symmetric rails (<1%) and load regulation of <2%. It can be synchronized to an external clock to help filter out beat frequencies. This application report also provides a solution to generate programmable output voltage of up to ±100 V by the introduction of an intermediate boost stage.