NCP1217A

NCP1217, NCP1217A Enhanced PWM Current-Mode Controller for High-Power Universal Off-Line Supplies Housed in an SO−8 or PDIP−7 package, the NCP1217 represents the enhanced version of the NCP1203−based controllers. Due to its high drive capability, NCP1217 drives large gate−charge MOSFETs, which together with internal ramp compensation and built−in overvoltage protection, ease the design of modern AC/DC adapters. NCP1217 offers a true alternative to UC384X−based designs. With an internal structure operating at different fixed frequencies (65–100–133 kHz), the controller features a high−voltage startup FET, which ensures a clean and loss less startup sequence. Its current−mode control topology provides an excellent input audio−susceptibility and inherent pulse−by−pulse control. Internal ramp compensation easily prevents subharmonic oscillations from taking place in continuous conduction mode designs. When the current setpoint falls below a given value, e.g. the output power demand diminishes, the IC automatically enters the so−called skip cycle mode and provides excellent efficiency at light loads. Because this occurs at a user adjustable low peak current, no acoustic noise takes place. The NCP1217 features two efficient protective circuitries: 1) In presence of an overcurrent condition, the output pulses are disabled and the device enters a safe burst mode, trying to restart. Once the default has gone, the device auto−recovers. 2) If an external signal (e.g. a temperature sens...