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 start-up 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.