The NCP1380 is a high performance device aimed at powering quasi-resonant converters. Capitalizing on a proprietary valley lockout system, the controller shifts gears and reduces the switching frequency as the power loading becomes lighter. This results in a stable operation despite switching events always triggering in the drain-source valley. This system works down to the 4th valley and toggles to a variable frequency mode beyond, ensuring an excellent standby power performance. To improve the safety in the overload situations, the controller includes an Over Power Protection (OPP) circuit which clamps the delivered power at high-line. Safety-wise, a fixed internal timer relies on the feedback voltage to detect a fault. Once the timer elapses, the controller stops and stays latched for option A and C or enters auto-recovery mode for option B and D. Particularly well suited for adapter applications, the controller features a pin to implement either a combined overvoltage / overtemperature protection (version A and B) or a combined brownout / overvoltage protection (version C and D).