NCP1342: Quasi-Resonant Flyback Controller with Valley Lock-Out Switching

The NCP1342 is a highly integrated quasi-resonant flyback controller suitable for designing high-performance off-line power converters. With an integrated active X2 capacitor discharge feature, the NCP1342 can enable no-load power consumption below 30 mW.

The NCP1342 features proprietary valley-lockout circuitry, ensuring stable valley switching. This system works down to the 6th valley and transitions to frequency foldback mode to reduce switching losses. As the load decreases further, the NCP1342 enters quiet-skip mode to manage the power delivery while minimizing acoustic noise.

To ensure light load performance with high frequency designs, the NCP1342 incorporates Minimum Peak Current Modulation (MPCM) to reduce the switching frequency quickly. To help ensure converter ruggedness, the NCP1342 implements several key protective features such as internal brownout detection, a non-dissipative Over Power Protection (OPP) for constant maximum output power regardless of input voltage, a latched overvoltage and NTC-ready overtemperature protection through a dedicated pin, and line removal detection to safely discharge the X2 capacitors when the ac line is removed.