The purpose of the paper is to review and compare the ac-dc electric power conversion topologies from the perspective of More Electric Aircraft (MEA) utilization. Advancements in power electronics encompass many evolving technologies including power semiconductor devices, microprocessors or digital signal processors (DSPs), thermal management, EMI and corona mitigation techniques, and mechanical packaging. The weight, volume, cost, and performance are critical design criteria, as is achieving other important requirements and specifications such as power quality, EMI/EMC, reliability, vibration, and shock for more electric aircraft applications. In this paper, an introduction will be made to the traditional versus modern aircraft power distribution systems illustrating the need of ac-dc power conversion systems. Then, the various power conversion topologies for more electric aircraft will be reviewed.