Losses analysis and low standby losses quasi-resonant flyback converter design

In this paper, an AC-DC flyback converter with low power loss during low load condition is designed and implemented. A power loss model and breakdown of the quasi-resonant flyback converter is not only derived, but also analyzed with mathematic analysis software, MathCAD^®. A new efficiency oriented burst mode control method is proposed to improve the system efficiency under standby condition. A laboratory prototype quasi-resonant flyback converter with universal range input voltage of 90~264 V_rms and output 24V/4.17A is implemented to verify the theoretical analysis. The power loss of the quasi-resonant flyback converter at 0.25 W load and 264 V_rms is 160 mW that achieve the Energy Star Standard.