NCP1280

NCP1280 Active Clamp Voltage Mode PWM Controller for Off-Line Applications The NCP1280 provides a highly integrated solution for off−line power supplies requiring high−efficiency and low parts count. This voltage mode controller provides control outputs for driving a forward converter primary MOSFET and an auxiliary MOSFET for active clamp circuit. The second output with its programmable delay can also be used for driving a synchronous rectifier on the secondary or for asymmetric half bridge circuits. Incorporation of high voltage startup circuitry (with 700 V capability) reduces parts count and system power dissipation. Additional features such as line UV/OV protection, soft−start, single resistor programmable (high) frequency oscillator, line voltage feedforward, dual mode overcurrent protection and maximum duty cycle control, allow converter optimization at minimal cost. Compared to a traditional forward converter, an NCP1280 based converter can offer significant efficiency improvements and system cost savings. Features Internal High Voltage Startup Regulator (25 V to 700 V) Dual Control Outputs with Adjustable Overlap Delay Programmable Maximum Duty Cycle Control Single Resistor Oscillator Frequency Setting Fast Line Feedforward Line Under/Overvoltage Lockout Dual Mode Overcurrent Protection Programmable Soft−Start Precision 5.0 V Reference This is a Pb−Free Device* Typical Applications Off−Line Power Converters in 100−500 W Range Desktop Power S...