NCP1361

Low Power Offline Constant Current PWM Current-Mode Controller with/without High Voltage Startup Current Source NCP1361, NCP1366 The NCP1361/66 offers a new solution targeting output power levels from a few watts up to 20 W in a universal−mains flyback application. Due to a novel method this new controller offers a primary−side constant current control, saving secondary−side components to perform current regulation. The NCP1361/66 operates in valley−lockout quasi−resonant peak current mode control mode at nominal load to provide high efficiency. When the secondary−side power starts diminishing, the switching frequency naturally increases until a voltage−controlled oscillator (VCO) takes the lead, synchronizing the MOSFET turn−on in a drain−source voltage valley. The frequency is thus reduced by stepping into successive valleys until the number 4 is reached. Beyond this point, the frequency is linearly decreased in valley−switching mode until a minimum is hit. Valley lockout during the first four drain−source valleys prevents erratic discrete jumps and provides good efficiency in lighter load situations. Features ±10% Current Regulation 560 V Startup Current Source No Frequency Clamp, 80 or 110 kHz Maximum Switching Frequency Options Quasi−Resonant Operation with Valley Switching Operation Fixed Peak Current & Deep Frequency Foldback @ Light Load Operation External Constant Voltage Feedback Adjustment Cycle by Cycle Peak Current Limit Built−In Soft−Start Over...