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USB-C power adapters and other AC-DC power converters operating in the 45- to 120-W range are under constant pressure to deliver higher efficiency in ever-smaller form factors without overheating. These challenges are compounded by increasingly tight regulations for standby and active efficiency, while system designers must also meet cost and manufacturability constraints.

At these power levels, quasi-resonant (QR) flyback converters remain the most dominant topology. By enabling valley switching to reduce switching losses while maintaining a relatively simple architecture, QR flyback designs can strike a strong balance of efficiency, cost, and design complexity.