Achieving High Efficiency Across Load in a 2-Stage 140 W Flyback USB PD 3.1 Compact Notebook Adapter

Flyback converters are widely used for their simplicity and cost-effectiveness. However, when output power exceeds 100 W, meeting regulatory efficiency requirements for light to full load can be difficult. The primary sources of efficiency losses are switching losses in the primary power switch and conduction losses, particularly due to hard switching. This paper explores methods to reduce switching and conduction losses through component selection and how transformer leakage inductance can improve efficiency. Also, optimizing Zero Voltage Switching (ZVS) at different load points and the use of external circuits to minimize power dissipation at light loads will be explored.