The Fairchild Power Switch (FPS) product family is specially designed for an off line SMPS with minimal external components. The Fairchild Power Switch (FPS) consists of high voltage power SenseFET and current mode PWM controller. The PWM controller includes integrated fixed oscillator, under voltage lock out, leading edge blanking block, optimized gate turnon/turn-off driver, thermal shut down protection, over voltage protection, temperature compensated precise current sources for loop compensation and fault protection circuit. Compared to discrete MOSFET and PWM controller or ring choke converter (RCC) solutions, the Fairchild Power Switch (FPS) can reduce total cost, component count, size and weight simultaneously increasing efficiency, productivity, and system reliability. It has simple applications well suited for cost down design for flyback converter or forward converter.