Improved efficiency in medium-power flyback converters

Abstract

Switch-mode power supplies (SMPS's) not only convert energy, they also consume it. Typical operational efficiencies are approximately 25 to 60% for linear power supplies, and approximately 50-90% for switching power supplies. This means that products whose end-use electronics are dc, such as televisions and DVD players, could consume 50% less power when operating if the power supply were upgraded from 40% efficiency to 80% efficiency. Savings can occur not only from using SMPS's instead of linear power supplies, but also from specifying highly efficient switching power supplies. In many cases, efficiencies are still lagging to keep costs down, since the power consumption is considered to be relatively low (40W-700W range). Over time, however, efficiency improvement strategies will pay back based on the cost of energy. Therefore three common flyback converter topologies have been studied through this thesis in the Low (15W), Medium (40W), and High (150W) Power levels. Efficiency analysis on the three power level topologies showed that the greatest opportunity for efficiency improvement existed in the 40W (medium power) topology. Efficiency improvement and measurement approaches are investigated and an optimized medium-power flyback converter is proposed and implemented resulting in an efficiency improvement from 57.8% to 83.6%.