The NCP1339 is a highly integrated quasi-resonant flyback controller capable of controlling rugged and high-performance off-line power supplies as required by adapter applications. With an integrated active X-cap discharge feature and power savings mode, the NCP1339 can enable no-load power consumption below 10 mW for 65 W notebook adapters.The quasi-resonant current-mode flyback stage features a proprietary valley-lockout circuitry, ensuring stable valley switching. This system works down to the 6th valley and toggles to a frequency foldback mode to eliminate switching losses. When the loop tends to force below 25-kHz frequencies, the NCP1339 skips cycles to contain the power delivery.To help build rugged converters, the controller features several key protective features: an internal brown-out, a non-dissipative Over Power Protection for a constant maximum output current regardless of the input voltage, a latched over voltage protection through a dedicated pin.